bims-auttor Biomed News
on Autophagy and mTOR
Issue of 2022–10–23
63 papers selected by
Viktor Korolchuk, Newcastle University
  1. Parkin drives pS65-Ub turnover independently of canonical autophagy in Drosophila.
  2. NBR1: The archetypal selective autophagy receptor.
  3. The intracellular Ca2+ channel TRPML3 is a PI3P effector that regulates autophagosome biogenesis.
  4. Parkin coordinates mitochondrial lipid remodeling to execute mitophagy.
  5. Zinc enhances autophagic flux and lysosomal function through transcription factor EB activation and V-ATPase assembly.
  6. Transcriptional regulation of autophagy by RNA polymerase II.
  7. Cellular autophagy, the compelling roles in hearing function and dysfunction.
  8. The cholesterol transport protein GRAMD1C regulates autophagy initiation and mitochondrial bioenergetics.
  9. Interaction between autophagy and the NLRP3 inflammasome in Alzheimer's and Parkinson's disease.
  10. Eructophagy: Macrophages Use Autophagic Machinery to Burp Out Parts of Their Meal by Autophagy.
  11. Endothelial cell autophagy in the context of disease development.
  12. Role of mitophagy in the neurodegenerative diseases and its pharmacological advances: A review.
  13. Class III PI3K Biology.
  14. Functions of autophagy in chloroplast protein degradation and homeostasis.
  15. Oligodendroglial macroautophagy is essential for myelin sheath turnover to prevent neurodegeneration and death.
  16. Arabidopsis ORP2A mediates ER-autophagosomal membrane contact sites and regulates PI3P in plant autophagy.
  17. ClC-3 silencing mediates lysosomal acidification arrest and autophagy inhibition to sensitize chemo-photothermal therapy.
  18. LC3/GABARAP binding to fluid membranes is potentiated by ceramide.
  19. Development of new tools to study membrane-anchored mammalian Atg8 proteins.
  20. SZT2 maintains hematopoietic stem cell homeostasis via nutrient-mediated mTORC1 regulation.
  21. Transcriptional targets of senataxin and E2 promoter binding factors are associated with neuro-degenerative pathways during increased autophagic flux.
  22. The critical role of the endolysosomal system in cerebral ischemia.
  23. Lysosomal positioning regulates Rab10 phosphorylation at LRRK2+ lysosomes.
  24. Engineered AIM-based selective autophagy to degrade proteins and organelles in planta.
  25. Super-Resolution Imaging of Autophagy by a Preferred Pair of Self-Labeling Protein Tags and Fluorescent Ligands.
  26. Methylglyoxal induces multiple serine phosphorylation in insulin receptor substrate 1 via the TAK1-p38-mTORC1 signaling axis in adipocytes.
  27. Cobalt induces neurodegenerative damages through impairing autophagic flux by activating hypoxia-inducible factor-1α triggered ROS overproduction.
  28. Temporal analysis of skeletal muscle remodelling post hindlimb ischemia reveals intricate autophagy regulation.
  29. Cellular and physiological roles of the conserved atypical MAP kinase ERK7.
  30. Silver nanoparticle-induced impaired autophagic flux and lysosomal dysfunction contribute to the microglia inflammation polarization.
  31. Treadmill Exercise Improves PINK1/Parkin-Mediated Mitophagy Activity Against Alzheimer's Disease Pathologies by Upregulated SIRT1-FOXO1/3 Axis in APP/PS1 Mice.
  32. Neuronal Ganglioside and Glycosphingolipid (GSL) Metabolism and Disease : Cascades of Secondary Metabolic Errors Can Generate Complex Pathologies (in LSDs).
  33. The Amyloid Inhibitor CLR01 Relieves Autophagy and Ameliorates Neuropathology in a Severe Lysosomal Storage Disease.
  34. Inhibiting glutamine utilization creates a synthetic lethality for suppression of ATP citrate lyase in KRas-driven cancer cells.
  35. Myelinosome organelles in pathological retinas: ubiquitous presence and dual role in ocular proteostasis maintenance.
  36. Tracking Autophagy Process with a TBET and AIE-Based Ratiometric Two-Photon Viscosity Probe.
  37. Targeting LRRK2 in Parkinson's disease.
  38. RagC GTPase regulates mTOR to promote chemoresistance in senescence-like HepG2 cells.
  39. Cross-linking of the endolysosomal system reveals potential flotillin structures and cargo.
  40. Tau interactome and RNA binding proteins in neurodegenerative diseases.
  41. Inducible deletion of Raptor and mTOR from adult skeletal muscle impairs muscle contractility and relaxation.
  42. Angiotensin II regulates mitochondrial mTOR pathway activity dependent on acyl CoA synthetase 4 in adrenocortical cells.
  43. Retinoic Acid Increases Cellular Cholesterol in Leishmania donovani-Infected Macrophages in an mTOR-Independent Manner.
  44. Rapalogs downmodulate intrinsic immunity and promote cell entry of SARS-CoV-2.
  45. Autophagy activation can partially rescue proteasome dysfunction-mediated cardiac toxicity.
  46. Autophagy in the normal and diseased Cornea.
  47. Resistance exercise enhances long-term mTORC1 sensitivity to leucine.
  48. Plant autophagosomes mature into amphisomes prior to their delivery to the central vacuole.
  49. Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases.
  50. Wnt5a regulates autophagy in Bacille Calmette-Guérin (BCG)-Infected pulmonary epithelial cells.
  51. Proteomic analysis of Atg8-dependent recruitment of phagosomal proteins in the enteric protozoan parasite Entamoeba histolytica.
  52. Mitophagy and reactive oxygen species interplay in Parkinson's disease.
  53. Larotrectinib induces autophagic cell death through AMPK/mTOR signalling in colon cancer.
  54. Graphene oxide induced dynamic changes of autophagy-lysosome pathway and cell apoptosis via TFEB dysregulation in F98 cells.
  55. A minute fraction of α-synuclein in extracellular vesicles may be a major contributor to α-synuclein spreading following autophagy inhibition.
  56. LC3B Binds to the Autophagy Protease ATG4b with High Affinity Using a Bipartite Interface.
  57. The metabolite-controlled ubiquitin conjugase Ubc8 promotes mitochondrial protein import.
  58. Autophagy: Dual roles and perspective for clinical treatment of colorectal cancer.
  59. Autophagy Regulates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells Induced by Orthodontic Tension.
  60. mTOR signaling: A pivotal player in Treg cell dysfunction in systemic lupus erythematosus.
  61. Editorial: Mitochondrial and lysosomal dysfunction in neurodegenerative diseases: Molecular mechanisms and therapeutic strategies.
  62. Liquid-liquid phase separation mediates the formation of herpesvirus assembly compartments.
  63. Lysosomal Targeting of β-Cyclodextrin.
  1. EMBO Rep. 2022 Oct 17. e202153552
    Parkin drives pS65-Ub turnover independently of canonical autophagy in Drosophila.
    Joanne L Usher, Alvaro Sanchez-Martinez, Ana Terriente-Felix, Po-Lin Chen, Juliette J Lee, Chun-Hong Chen, Alexander J Whitworth.
      Parkinson's disease-related proteins, PINK1 and Parkin, act in a common pathway to maintain mitochondrial quality control. While the PINK1-Parkin pathway can promote autophagic mitochondrial turnover (mitophagy) following mitochondrial toxification in cell culture, alternative quality control pathways are suggested. To analyse the mechanisms by which the PINK1-Parkin pathway operates in vivo, we developed methods to detect Ser65-phosphorylated ubiquitin (pS65-Ub) in Drosophila. Exposure to the oxidant paraquat led to robust, Pink1-dependent pS65-Ub production, while pS65-Ub accumulates in unstimulated parkin-null flies, consistent with blocked degradation. Additionally, we show that pS65-Ub specifically accumulates on disrupted mitochondria in vivo. Depletion of the core autophagy proteins Atg1, Atg5 and Atg8a did not cause pS65-Ub accumulation to the same extent as loss of parkin, and overexpression of parkin promoted turnover of both basal and paraquat-induced pS65-Ub in an Atg5-null background. Thus, we have established that pS65-Ub immunodetection can be used to analyse Pink1-Parkin function in vivo as an alternative to reporter constructs. Moreover, our findings suggest that the Pink1-Parkin pathway can promote mitochondrial turnover independently of canonical autophagy in vivo.
    Keywords:   in vivo ; Parkinson's disease; mitochondria; mitophagy; phospho-ubiquitin
    DOI:  https://doi.org/10.15252/embr.202153552
  2. J Cell Biol. 2022 11 07. pii: e202208092. [Epub ahead of print]221(11):
    NBR1: The archetypal selective autophagy receptor.
    Nikoline Lander Rasmussen, Athanasios Kournoutis, Trond Lamark, Terje Johansen.
      NBR1 was discovered as an autophagy receptor not long after the first described vertebrate autophagy receptor p62/SQSTM1. Since then, p62 has currently been mentioned in >10,000 papers on PubMed, while NBR1 is mentioned in <350 papers. Nonetheless, evolutionary analysis reveals that NBR1, and likely also selective autophagy, was present already in the last eukaryotic common ancestor (LECA), while p62 appears first in the early Metazoan lineage. Furthermore, yeast-selective autophagy receptors Atg19 and Atg34 represent NBR1 homologs. NBR1 is the main autophagy receptor in plants that do not contain p62, while most animal taxa contain both NBR1 and p62. Mechanistic studies are starting to shed light on the collaboration between mammalian NBR1 and p62 in the autophagic degradation of protein aggregates (aggrephagy). Several domains of NBR1 are involved in cargo recognition, and the list of known substrates for NBR1-mediated selective autophagy is increasing. Lastly, roles of NBR1 in human diseases such as proteinopathies and cancer are emerging.
    DOI:  https://doi.org/10.1083/jcb.202208092
  3. Proc Natl Acad Sci U S A. 2022 Oct 25. 119(43): e2200085119
    The intracellular Ca2+ channel TRPML3 is a PI3P effector that regulates autophagosome biogenesis.
    So Woon Kim, Mi Kyung Kim, Seokwoo Hong, Areum Choi, Jee Hye Choi, Shmuel Muallem, Insuk So, Dongki Yang, Hyun Jin Kim.
      Autophagy is a multiple fusion event, initiating with autophagosome formation and culminating with fusion with endo-lysosomes in a Ca2+-dependent manner. The source of Ca2+ and the molecular mechanism by which Ca2+ is provided for this process are not known. The intracellular Ca2+ permeable channel transient receptor potential mucolipin 3 (TRPML3) localizes in the autophagosome and interacts with the mammalian autophagy-related protein 8 (ATG8) homolog GATE16. Here, we show that lipid-regulated TRPML3 is the Ca2+ release channel in the phagophore that provides the Ca2+ necessary for autophagy progress. We generated a TRPML3-GCaMP6 fusion protein as a targeted reporter of TRPML3 compartment localization and channel function. Notably, TRPML3-GCaMP6 localized in the phagophores, the level of which increased in response to nutrient starvation. Importantly, phosphatidylinositol-3-phosphate (PI3P), an essential lipid for autophagosome formation, is a selective regulator of TRPML3. TRPML3 interacted with PI3P, which is a direct activator of TRPML3 current and Ca2+ release from the phagophore, to promote and increase autophagy. Inhibition of TRPML3 suppressed autophagy even in the presence of excess PI3P, while activation of TRPML3 reversed the autophagy inhibition caused by blocking PI3P. Moreover, disruption of the TRPML3-PI3P interaction abolished both TRPML3 activation by PI3P and the increase in autophagy. Taken together, these results reveal that TRPML3 is a downstream effector of PI3P and a key regulator of autophagy. Activation of TRPML3 by PI3P is the critical step providing Ca2+ from the phagophore for the fusion process, which is essential for autophagosome biogenesis.
    Keywords:  Ca2+ channel; GCaMP6; PI3P; TRPML3; autophagy
    DOI:  https://doi.org/10.1073/pnas.2200085119
  4. EMBO Rep. 2022 Oct 18. e55191
    Parkin coordinates mitochondrial lipid remodeling to execute mitophagy.
    Chao-Chieh Lin, Jin Yan, Meghan D Kapur, Kristi L Norris, Cheng-Wei Hsieh, De Huang, Nicolas Vitale, Kah-Leong Lim, Ziqiang Guan, Xiao-Fan Wang, Jen-Tsan Chi, Wei-Yuan Yang, Tso-Pang Yao.
      Autophagy has emerged as the prime machinery for implementing organelle quality control. In the context of mitophagy, the ubiquitin E3 ligase Parkin tags impaired mitochondria with ubiquitin to activate autophagic degradation. Although ubiquitination is essential for mitophagy, it is unclear how ubiquitinated mitochondria activate autophagosome assembly locally to ensure efficient destruction. Here, we report that Parkin activates lipid remodeling on mitochondria targeted for autophagic destruction. Mitochondrial Parkin induces the production of phosphatidic acid (PA) and its subsequent conversion to diacylglycerol (DAG) by recruiting phospholipase D2 and activating the PA phosphatase, Lipin-1. The production of DAG requires mitochondrial ubiquitination and ubiquitin-binding autophagy receptors, NDP52 and optineurin (OPTN). Autophagic receptors, via Golgi-derived vesicles, deliver an autophagic activator, EndoB1, to ubiquitinated mitochondria. Inhibition of Lipin-1, NDP52/OPTN, or EndoB1 results in a failure to produce mitochondrial DAG, autophagosomes, and mitochondrial clearance, while exogenous cell-permeable DAG can induce autophagosome production. Thus, mitochondrial DAG production acts downstream of Parkin to enable the local assembly of autophagosomes for the efficient disposal of ubiquitinated mitochondria.
    Keywords:  Lipin-1; PLD2; Parkin; diacylglycerol; mitophagy
    DOI:  https://doi.org/10.15252/embr.202255191
  5. Front Cell Neurosci. 2022 ;16 895750
    Zinc enhances autophagic flux and lysosomal function through transcription factor EB activation and V-ATPase assembly.
    Ki-Ryeong Kim, Sang Eun Park, Ji-Ye Hong, Jae-Young Koh, Dong-Hyung Cho, Jung Jin Hwang, Yang-Hee Kim.
      The stimulation of autophagy or lysosomes has been considered therapeutic for neurodegenerative disorders because the accumulation of misfolded proteins is commonly observed in the brains of individuals with these diseases. Although zinc is known to play critical roles in the functions of lysosomes and autophagy, the mechanism behind this regulatory relationship remains unclear. Therefore, in this study, we examined which mechanism is involved in zinc-mediated activation of autophagy and lysosome. Exposure to zinc at a sub-lethal concentration activated autophagy in a concentration-dependent manner in mRFP-GFP-LC3-expressing H4 glioma cells. Zinc also rescued the blocking of autophagic flux arrested by pharmaceutical de-acidification. Co-treatment with zinc attenuated the chloroquine (CQ)-induced increase in the number and size of mRFP-GFP-LC3 puncta in H4 cells and accumulation of p62 by CQ or ammonium chloride in both H4 and mouse cerebrocortical cultures. Zinc rapidly induced the expression of cathepsin B (CTSB) and cathepsin D (CTSD), representative lysosomal proteases in neurons, which appeared likely to be mediated by transcription factor EB (TFEB). We observed the translocation of TFEB from neurite to nucleus and the dephosphorylation of TFEB by zinc. The addition of cycloheximide, a chemical inhibitor of protein synthesis, inhibited the activity of CTSB and CTSD at 8 h after zinc exposure but not at 1 h, indicating that only late lysosomal activation was dependent on the synthesis of CTSB and CTSD proteins. At the very early time point, the activation of cathepsins was mediated by an increased assembly of V-ATPase on lysosomes and resultant lysosomal acidification. Finally, considering that P301L mutation in tau protein causes frontotemporal dementia through aggressive tau accumulation, we investigated whether zinc reduces the accumulation of protein aggregates in SK-N-BE(2)-C neuroblastoma cells expressing wild-type tau or mutant P301L-tau. Zinc markedly attenuated the levels of phosphorylated tau and total tau as well as p62 in both wild-type and mutant tau-overexpressing cells. We also observed that zinc was more effective than rapamycin at inducing TFEB-dependent CTSB and CTSD expression and V-ATPase-dependent lysosomal acidification and CTSB/CTSD activation. These results suggest that the regulation of zinc homeostasis could be a new approach for developing treatments for neurodegenerative diseases, including Alzheimer's and Parkinson's.
    Keywords:  TFEB; V-ATPase; autophagy; cathepsin B; cathepsin D; lysosome; neurodegenerative disease; zinc
    DOI:  https://doi.org/10.3389/fncel.2022.895750
  6. Autophagy. 2022 Oct 20.
    Transcriptional regulation of autophagy by RNA polymerase II.
    Yuqing Lei, Ting Huang, Gaoyue Jiang, Yabin Zhang, Shiyan Liu, Huihui Li, Kefeng Lu.
      Macroautophagy/autophagy is a catabolic recycling pathway and is tightly regulated by upstream signals. Autophagy genes are quickly upregulated upon stimuli such as nutrition limitation in response to the external environment. However, how the transcriptional activation of autophagy genes occurs is not well understood. We recently found that in yeast, the RNA polymerase II subunit Rpb9 specifically and efficiently upregulates the transcription of the autophagy gene ATG1 with the mediation of Gcn4. Such regulation was shown to be essential for autophagic activities induced by starvation. Furthermore, the function of Rpb9 in autophagy and the activation of ATG1 transcription is conserved in mammalian cells. In conclusion, Rpb9 specifically and positively regulates ATG1 transcription as a key regulator of autophagy.
    Keywords:  ATG1 gene; Gcn4; Rpb9; autophagy; starvation; transcription; yeast
    DOI:  https://doi.org/10.1080/15548627.2022.2138141
  7. Front Cell Neurosci. 2022 ;16 966202
    Cellular autophagy, the compelling roles in hearing function and dysfunction.
    Huanzhi Wan, Yuanyuan Zhang, Qingquan Hua.
      Sensorineural hearing loss (SNHL) is currently a major health issue. As one of the most common neurodegenerative diseases, SNHL is associated with the degradation of hair cells (HCs), spiral ganglion neurons (SGNs), the stria vascularis, supporting cells and central auditory system cells. Autophagy is a highly integrated cellular system that eliminates impaired components and replenishes energy to benefit cellular homeostasis. Etiological links between autophagy alterations and neurodegenerative diseases, such as SNHL, have been established. The hearing pathway is complex and depends on the comprehensive functions of many types of tissues and cells in auditory system. In this review, we discuss the roles of autophagy in promoting and inhibiting hearing, paying particular attention to specific cells in the auditory system, as discerned through research. Hence, our review provides enlightening ideas for the role of autophagy in hearing development and impairment.
    Keywords:  auditory cells; auditory pathway; autophagy; cochlea; sensorineural hearing loss
    DOI:  https://doi.org/10.3389/fncel.2022.966202
  8. Nat Commun. 2022 Oct 21. 13(1): 6283
    The cholesterol transport protein GRAMD1C regulates autophagy initiation and mitochondrial bioenergetics.
    Matthew Yoke Wui Ng, Chara Charsou, Ana Lapao, Sakshi Singh, Laura Trachsel-Moncho, Sebastian W Schultz, Sigve Nakken, Michael J Munson, Anne Simonsen.
      During autophagy, cytosolic cargo is sequestered into double-membrane vesicles called autophagosomes. The contributions of specific lipids, such as cholesterol, to the membranes that form the autophagosome, remain to be fully characterized. Here, we demonstrate that short term cholesterol depletion leads to a rapid induction of autophagy and a corresponding increase in autophagy initiation events. We further show that the ER-localized cholesterol transport protein GRAMD1C functions as a negative regulator of starvation-induced autophagy and that both its cholesterol transport VASt domain and membrane binding GRAM domain are required for GRAMD1C-mediated suppression of autophagy initiation. Similar to its yeast orthologue, GRAMD1C associates with mitochondria through its GRAM domain. Cells lacking GRAMD1C or its VASt domain show increased mitochondrial cholesterol levels and mitochondrial oxidative phosphorylation, suggesting that GRAMD1C may facilitate cholesterol transfer at ER-mitochondria contact sites. Finally, we demonstrate that expression of GRAMD family proteins is linked to clear cell renal carcinoma survival, highlighting the pathophysiological relevance of cholesterol transport proteins.
    DOI:  https://doi.org/10.1038/s41467-022-33933-2
  9. Front Aging Neurosci. 2022 ;14 1018848
    Interaction between autophagy and the NLRP3 inflammasome in Alzheimer's and Parkinson's disease.
    Ranran Lu, Lijie Zhang, Xinling Yang.
      Autophagy degrades phagocytosed damaged organelles, misfolded proteins, and various pathogens through lysosomes as an essential way to maintain cellular homeostasis. Autophagy is a tightly regulated cellular self-degradation process that plays a crucial role in maintaining normal cellular function and homeostasis in the body. The NLRP3 inflammasome in neuroinflammation is a vital recognition receptor in innate cellular immunity, sensing external invading pathogens and endogenous stimuli and further triggering inflammatory responses. The NLRP3 inflammasome forms an inflammatory complex by recognizing DAMPS or PAMPS, and its activation triggers caspase-1-mediated cleavage of pro-IL-1β and pro-IL-18 to promote the inflammatory response. In recent years, it has been reported that there is a complex interaction between autophagy and neuroinflammation. Strengthening autophagy can regulate the expression of NLRP3 inflammasome to reduce neuroinflammation in neurodegenerative disease and protect neurons. However, the related mechanism is not entirely clear. The formation of protein aggregates is one of the standard features of Neurodegenerative diseases. A large number of toxic protein aggregates can induce inflammation. In theory, activation of the autophagy pathway can remove the potential toxicity of protein aggregates and delay the progression of the disease. This article aims to review recent research on the interaction of autophagy, NLRP3 inflammasome, and protein aggregates in Alzheimer's disease (AD) and Parkinson's disease (PD), analyze the mechanism and provide theoretical references for further research in the future.
    Keywords:  Alzheimer’s disease; NLRP3; Parkinson’s disease; autophagy; inflammasome; protein aggregation
    DOI:  https://doi.org/10.3389/fnagi.2022.1018848
  10. Autophagy. 2022 Oct 20.
    Eructophagy: Macrophages Use Autophagic Machinery to Burp Out Parts of Their Meal by Autophagy.
    Jenny A Nguyen, Catherine J Greene, Robin M Yates.
      The phagolysosome is an antimicrobial and degradative organelle that plays key roles in macrophage-mediated inflammatory and homeostatic functions. Whereas mature phagolysosomes are known to sequester and degrade their contents into basic nutrients, they were not previously assigned an active role in amplifying inflammation. We have described a novel macrophage process in which partially digested immunostimulatory PAMPs are released extracellularly from the mature phagolysosome via discrete events we term eructophagy. Eructophagy is induced by proinflammatory stimuli, negatively regulated by IL4 and MTOR, and is dependent on key autophagy proteins, including fusion machinery of degradative and secretory autophagy. We propose that macrophages use eructophagy to release processed PAMPs/DAMPs to amplify local inflammation.
    Keywords:  PAMPs; autophagy; eructophagy; inflammation; macrophage; phagolysosome; phagosome; secretion
    DOI:  https://doi.org/10.1080/15548627.2022.2138006
  11. Anat Cell Biol. 2022 Oct 21.
    Endothelial cell autophagy in the context of disease development.
    Basheer Abdullah Marzoog.
      Endothelial cells (EC) are the anatomical boundaries between the intravascular and extravascular space. Damage to ECs is catastrophic and induces endothelial cell dysfunction. The pathogenesis is multifactorial and involves dysregulation in the signaling pathways, membrane lipids ratio disturbance, cell-cell adhesion disturbance, unfolded protein response, lysosomal and mitochondrial stress, autophagy dysregulation, and oxidative stress. Autophagy is a lysosomal-dependent turnover of intracellular components. Autophagy was recognized early in the pathogenesis of endothelial dysfunction. Autophagy is a remarkable patho (physiological) process in the cell homeostasis regulation including EC. Regulation of autophagy rate is disease-dependent and impaired with aging. Up-regulation of autophagy induces endothelial cell regeneration/differentiation and improves the function of impaired ones. The paper scrutinizes the molecular mechanisms and triggers of EC dysregulation and current perspectives for future therapeutic strategies by autophagy targeting.
    Keywords:  Autophagy; Endothelial cells; Molecular medicine; Regeneration
    DOI:  https://doi.org/10.5115/acb.22.098
  12. Front Mol Neurosci. 2022 ;15 1014251
    Role of mitophagy in the neurodegenerative diseases and its pharmacological advances: A review.
    Qixia Wang, Haoyuan Xue, Yundi Yue, Shiqi Hao, Shu-Hong Huang, Zhaoqiang Zhang.
      Neurodegenerative diseases are a class of incurable and debilitating diseases characterized by progressive degeneration and death of cells in the central nervous system. They have multiple underlying mechanisms; however, they all share common degenerative features, such as mitochondrial dysfunction. According to recent studies, neurodegenerative diseases are associated with the accumulation of dysfunctional mitochondria. Selective autophagy of mitochondria, called mitophagy, can specifically degrade excess or dysfunctional mitochondria within cells. In this review, we highlight recent findings on the role of mitophagy in neurodegenerative disorders. Multiple studies were collected, including those related to the importance of mitochondria, the mechanism of mitophagy in protecting mitochondrial health, and canonical and non-canonical pathways in mitophagy. This review elucidated the important function of mitophagy in neurodegenerative diseases, discussed the research progress of mitophagy in neurodegenerative diseases, and summarized the role of mitophagy-related proteins in neurological diseases. In addition, we also highlight pharmacological advances in neurodegeneration.
    Keywords:  Alzheimer's disease; Huntington's disease; Parkinson's disease; amyotrophic lateral sclerosis; mitophagy; neurodegenerative diseases
    DOI:  https://doi.org/10.3389/fnmol.2022.1014251
  13. Curr Top Microbiol Immunol. 2022 ;436 69-93
    Class III PI3K Biology.
    Manuella Caux, Gaetan Chicanne, Sonia Severin.
      Highly conserved from yeast to mammals, vacuolar protein sorting 34 (Vps34) is the sole member of the third class of the phosphoinositide 3-kinase (PI3K) family. By producing phosphatidylinositol-3-monophosphate (PtdIns3P) through its scaffolding function essential for the catalytic lipid activity, Vps34 regulates endosomal trafficking, autophagy, phagocytosis, and nutrient-sensing signaling. The development of genetically modified mouse models and specific inhibitors has largely contributed over the past ten years to a better understanding of Vps34 functions in biological and physiological processes in mammals and, ultimately, its potential implications and targeting in human diseases. This chapter will summarize the current knowledge of the structure and regulation of Vps34 as well as its cellular and organismal functions.
    Keywords:  Autophagy; PhosphatIdylinositol-3-monophosphate; Signaling; Vesicular trafficking; Vps34
    DOI:  https://doi.org/10.1007/978-3-031-06566-8_3
  14. Front Plant Sci. 2022 ;13 993215
    Functions of autophagy in chloroplast protein degradation and homeostasis.
    Chen Wan, Qihua Ling.
      Chloroplasts are defining organelles in plant and algae, which carried out various critical metabolic processes, including photosynthesis. Roles of chloroplast protein homeostasis in plant development and stress adaptation were clearly demonstrated in previous studies, and its maintenance requires internal proteases originated from the prokaryotic ancestor. Recently, increasing evidence revealed that eukaryotic proteolytic pathways, ubiquitin-proteasome system (UPS) and autophagy, are also involved in the turnover of chloroplast proteins, in response to developmental and environmental cues. Notably, chloroplasts can be regulated via the selective degradation of chloroplast materials in a process called chlorophagy. Yet, understandings of the mechanism of chlorophagy are still rudimentary, particularly regarding its initiation and operation. Here we provide an updated overview of autophagy pathways for chloroplast protein degradation and discuss their importance for plant physiology. In addition, recent advance in analogous mitophagy in yeast and mammals will also be discussed, which provides clues for further elucidating the mechanism of chlorophagy.
    Keywords:  autophagy; chlorophagy; chloroplast; mitophagy; stress response
    DOI:  https://doi.org/10.3389/fpls.2022.993215
  15. Cell Rep. 2022 Oct 18. pii: S2211-1247(22)01330-4. [Epub ahead of print]41(3): 111480
    Oligodendroglial macroautophagy is essential for myelin sheath turnover to prevent neurodegeneration and death.
    Etan R Aber, Christopher J Griffey, Tim Davies, Alice M Li, Young Joo Yang, Katherine R Croce, James E Goldman, Jaime Grutzendler, Julie C Canman, Ai Yamamoto.
      Although macroautophagy deficits are implicated across adult-onset neurodegenerative diseases, we understand little about how the discrete, highly evolved cell types of the central nervous system use macroautophagy to maintain homeostasis. One such cell type is the oligodendrocyte, whose myelin sheaths are central for the reliable conduction of action potentials. Using an integrated approach of mouse genetics, live cell imaging, electron microscopy, and biochemistry, we show that mature oligodendrocytes require macroautophagy to degrade cell autonomously their myelin by consolidating cytosolic and transmembrane myelin proteins into an amphisome intermediate prior to degradation. We find that disruption of autophagic myelin turnover leads to changes in myelin sheath structure, ultimately impairing neural function and culminating in an adult-onset progressive motor decline, neurodegeneration, and death. Our model indicates that the continuous and cell-autonomous maintenance of the myelin sheath through macroautophagy is essential, shedding insight into how macroautophagy dysregulation might contribute to neurodegenerative disease pathophysiology.
    Keywords:  Alfy/Wdfy3; CP: Neuroscience; amphisome; autophagosome; myelin; neurodegeneration; oligodendrocyte; selective autophagy
    DOI:  https://doi.org/10.1016/j.celrep.2022.111480
  16. Proc Natl Acad Sci U S A. 2022 Oct 25. 119(43): e2205314119
    Arabidopsis ORP2A mediates ER-autophagosomal membrane contact sites and regulates PI3P in plant autophagy.
    Hao Ye, Jiayang Gao, Zizhen Liang, Youshun Lin, Qianyi Yu, Shuxian Huang, Liwen Jiang.
      Autophagy is an intracellular degradation system for cytoplasmic constituents which is mediated by the formation of a double-membrane organelle termed the autophagosome and its subsequent fusion with the lysosome/vacuole. The formation of the autophagosome requires membrane from the endoplasmic reticulum (ER) and is tightly regulated by a series of autophagy-related (ATG) proteins and lipids. However, how the ER contacts autophagosomes and regulates autophagy remain elusive in plants. In this study, we identified and demonstrated the roles of Arabidopsis oxysterol-binding protein-related protein 2A (ORP2A) in mediating ER-autophagosomal membrane contacts and autophagosome biogenesis. We showed that ORP2A localizes to both ER-plasma membrane contact sites (EPCSs) and autophagosomes, and that ORP2A interacts with both the ER-localized VAMP-associated protein (VAP) 27-1 and ATG8e on the autophagosomes to mediate the membrane contact sites (MCSs). In ORP2A artificial microRNA knockdown (KD) plants, seedlings display retarded growth and impaired autophagy levels. Both ATG1a and ATG8e accumulated and associated with the ER membrane in ORP2A KD lines. Moreover, ORP2A binds multiple phospholipids and shows colocalization with phosphatidylinositol 3-phosphate (PI3P) in vivo. Taken together, ORP2A mediates ER-autophagosomal MCSs and regulates autophagy through PI3P redistribution.
    Keywords:  PI3P; autophagy; membrane contact site; oxysterol-binding protein–related protein
    DOI:  https://doi.org/10.1073/pnas.2205314119
  17. Int J Pharm. 2022 Oct 16. pii: S0378-5173(22)00852-3. [Epub ahead of print] 122297
    ClC-3 silencing mediates lysosomal acidification arrest and autophagy inhibition to sensitize chemo-photothermal therapy.
    Hongyu Zhang, Lanxin Meng, Lei Yin, Taojian Fan, Lan Yu, Shichao Han, Lixia Wang, Weiyuan Liang, Xiaoli Yang, Shiguo Sun.
      Protective autophagy can be activated by external stimuli such as chemotherapy (CT) and photothermal therapy (PTT), leading to tumour resistance. As a key subcellular for autophagy, lysosomal dysfunction is crucial for autophagy suppression. Furthermore, lysosomal drug sequestration enhances basic drug resistance such as doxorubicin (DOX), which is trapped away from its target site, namely, the nucleus. Moreover, most of nanodrug delivery systems are internalised to lysosome for degradation, which further leads to DOX resistance. Lysosome serves as an essential organelle in drug resistance mechanisms, whose acidification arrest provides a potential strategy to inhibit autophagy and lysosomal drug sequestration simultaneously. The chloride channel-3 (ClC-3) protein is known as an important Cl--H+ transporter to maintain lysosomal pH at low values of various human cells. Herein, a black phosphorus-based theranostic nanoplatform of BP-A-S@D is constructed, and HeLa cells are used as a model to verify the effect of ClC-3 on tumour lysosomal acidification and autophagy regulation. Consequently, ClC-3 silencing inhibits not only protective autophagy to sensitise chemo-photothermal therapy, but also DOX resistance by suppressing lysosomal acidification. Therefore, ClC-3 silencing could simultaneously inhibit autophagy and lysosomal drug sequestration to improve anti-tumour efficiency.
    Keywords:  ClC-3; autophagy inhibition; black phosphorus; chemo-photothermal therapy; lysosomal drug sequestration; lysosome acidification
    DOI:  https://doi.org/10.1016/j.ijpharm.2022.122297
  18. Autophagy. 2022 Oct 17.
    LC3/GABARAP binding to fluid membranes is potentiated by ceramide.
    Yaiza R Varela, Alicia Alonso.
      LC3/GABARAP constitute a macroautophagy/autophagy-related protein family derived from yeast Atg8. The involvement of specific lipids in LC3/GABARAP function is poorly understood. Exploring the interaction of LC3/GABARAP proteins with phosphatidylcholine- or sphingomyelin-based bilayers has revealed that cardiolipin is essential for the protein-bilayer interaction, and that ceramide markedly increases binding. Giant unilamellar vesicles examined under confocal fluorescence microscopy reveal that ceramide segregates laterally into very rigid domains, while GABARAP binds only the more fluid regions, suggesting that the enhancing role of ceramide is exerted by the minority of ceramide molecules dispersed in the fluid phase.
    Keywords:  LC3/GABARAP; autophagy proteins; cardiolipin; ceramide; mitochondria
    DOI:  https://doi.org/10.1080/15548627.2022.2136821
  19. Autophagy. 2022 Oct 17. 1-20
    Development of new tools to study membrane-anchored mammalian Atg8 proteins.
    Sang-Won Park, Pureum Jeon, Akinori Yamasaki, Hye Eun Lee, Haneul Choi, Ji Young Mun, Yong-Woo Jun, Ju-Hui Park, Seung-Hwan Lee, Soo-Kyeong Lee, You-Kyung Lee, Hyun Kyu Song, Michael Lazarou, Dong-Hyong Cho, Masaaki Komatsu, Nobuo N Noda, Deok-Jin Jang, Jin-A Lee.
       ABBREVIATIONS: A:C autophagic membrane:cytosol; ALS amyotrophic lateral sclerosis; ATG4 autophagy related 4; Atg8 autophagy related 8; BafA1 bafilomycin A1; BNIP3L/Nix BCL2 interacting protein 3 like; CALCOCO2/NDP52 calcium binding and coiled-coil domain 2; EBSS Earle's balanced salt solution; GABARAP GABA type A receptor-associated protein; GST glutathione S transferase; HKO hexa knockout; Kd dissociation constant; LIR LC3-interacting region; MAP1LC3/LC3 microtubule associated protein 1 light chain 3; NLS nuclear localization signal/sequence; PE phosphatidylethanolamine; SpHfl1 Schizosaccharomyces pombeorganic solute transmembrane transporter; SQSTM1/p62 SQSTM1/p62; TARDBP/TDP-43 TAR DNA binding protein; TKO triple knockout.
    Keywords:  Autophagy; GABARAP; LIR motif; RavZ protein; mammalian ATG8; selective mATG8–PE delipidation
    DOI:  https://doi.org/10.1080/15548627.2022.2132040
  20. J Clin Invest. 2022 Oct 17. pii: e146272. [Epub ahead of print]132(20):
    SZT2 maintains hematopoietic stem cell homeostasis via nutrient-mediated mTORC1 regulation.
    Na Yin, Gang Jin, Yuying Ma, Hanfei Zhao, Guangyue Zhang, Ming O Li, Min Peng.
      The mTORC1 pathway coordinates nutrient and growth factor signals to maintain organismal homeostasis. Whether nutrient signaling to mTORC1 regulates stem cell function remains unknown. Here, we show that SZT2 - a protein required for mTORC1 downregulation upon nutrient deprivation - is critical for hematopoietic stem cell (HSC) homeostasis. Ablation of SZT2 in HSCs decreased the reserve and impaired the repopulating capacity of HSCs. Furthermore, ablation of both SZT2 and TSC1 - 2 repressors of mTORC1 on the nutrient and growth factor arms, respectively - led to rapid HSC depletion, pancytopenia, and premature death of the mice. Mechanistically, loss of either SZT2 or TSC1 in HSCs led to only mild elevation of mTORC1 activity and reactive oxygen species (ROS) production. Loss of both SZT2 and TSC1, on the other hand, simultaneously produced a dramatic synergistic effect, with an approximately 10-fold increase of mTORC1 activity and approximately 100-fold increase of ROS production, which rapidly depleted HSCs. These data demonstrate a critical role of nutrient mTORC1 signaling in HSC homeostasis and uncover a strong synergistic effect between nutrient- and growth factor-mediated mTORC1 regulation in stem cells.
    Keywords:  Amino acid metabolism; Bone marrow transplantation; Hematology; Hematopoietic stem cells; Metabolism
    DOI:  https://doi.org/10.1172/JCI146272
  21. Sci Rep. 2022 Oct 21. 12(1): 17665
    Transcriptional targets of senataxin and E2 promoter binding factors are associated with neuro-degenerative pathways during increased autophagic flux.
    Aaron E Casey, Wenjun Liu, Leanne K Hein, Timothy J Sargeant, Stephen M Pederson, Ville-Petteri Mäkinen.
      Autophagy is an intracellular recycling process that degrades harmful molecules and enables survival during starvation, with implications for diseases including dementia, cancer and atherosclerosis. Previous studies demonstrate how a limited number of transcription factors (TFs) can increase autophagy. However, this knowledge has not resulted in translation into therapy, thus, to gain understanding of more suitable targets, we utilized a systems biology approach. We induced autophagy by amino acid starvation and mTOR inhibition in HeLa, HEK 293 and SH-SY5Y cells and measured temporal gene expression using RNA-seq. We observed 456 differentially expressed genes due to starvation and 285 genes due to mTOR inhibition (PFDR < 0.05 in every cell line). Pathway analyses implicated Alzheimer's and Parkinson's diseases (PFDR ≤ 0.024 in SH-SY5Y and HeLa) and amyotrophic lateral sclerosis (ALS, PFDR < 0.05 in mTOR inhibition experiments). Differential expression of the Senataxin (SETX) target gene set was predicted to activate multiple neurodegenerative pathways (PFDR ≤ 0.04). In the SH-SY5Y cells of neuronal origin, the E2F transcription family was predicted to activate Alzheimer's disease pathway (PFDR ≤ 0.0065). These exploratory analyses suggest that SETX and E2F may mediate transcriptional regulation of autophagy and further investigations into their possible role in neuro-degeneration are warranted.
    DOI:  https://doi.org/10.1038/s41598-022-21617-2
  22. Neural Regen Res. 2023 May;18(5): 983-990
    The critical role of the endolysosomal system in cerebral ischemia.
    Hui-Yi Zhang, Ye Tian, Han-Yan Shi, Ya Cai, Ying Xu.
      Cerebral ischemia is a serious disease that triggers sequential pathological mechanisms, leading to significant morbidity and mortality. Although most studies to date have typically focused on the lysosome, a single organelle, current evidence supports that the function of lysosomes cannot be separated from that of the endolysosomal system as a whole. The associated membrane fusion functions of this system play a crucial role in the biodegradation of cerebral ischemia-related products. Here, we review the regulation of and the changes that occur in the endolysosomal system after cerebral ischemia, focusing on the latest research progress on membrane fusion function. Numerous proteins, including N-ethylmaleimide-sensitive factor and lysosomal potassium channel transmembrane protein 175, regulate the function of this system. However, these proteins are abnormally expressed after cerebral ischemic injury, which disrupts the normal fusion function of membranes within the endolysosomal system and that between autophagosomes and lysosomes. This results in impaired "maturation" of the endolysosomal system and the collapse of energy metabolism balance and protein homeostasis maintained by the autophagy-lysosomal pathway. Autophagy is the final step in the endolysosomal pathway and contributes to maintaining the dynamic balance of the system. The process of autophagosome-lysosome fusion is a necessary part of autophagy and plays a crucial role in maintaining energy homeostasis and clearing aging proteins. We believe that, in cerebral ischemic injury, the endolysosomal system should be considered as a whole rather than focusing on the lysosome. Understanding how this dynamic system is regulated will provide new ideas for the treatment of cerebral ischemia.
    Keywords:  autophagy; biodegradation; brain injury; chaperone-mediated autophagy; endolysosomal system; fusion; hypoxia-ischemia; brain; mitophagy; N-ethylmaleimide-sensitive protein; TMEM175
    DOI:  https://doi.org/10.4103/1673-5374.355745
  23. Proc Natl Acad Sci U S A. 2022 Oct 25. 119(43): e2205492119
    Lysosomal positioning regulates Rab10 phosphorylation at LRRK2+ lysosomes.
    Jillian H Kluss, Alexandra Beilina, Chad D Williamson, Patrick A Lewis, Mark R Cookson, Luis Bonet-Ponce.
      Genetic variation at the leucine-rich repeat kinase 2 (LRRK2) locus contributes to an enhanced risk of familial and sporadic Parkinson's disease. Previous data have demonstrated that recruitment to various membranes of the endolysosomal system results in LRRK2 activation. However, the mechanism(s) underlying LRRK2 activation at endolysosomal membranes and the cellular consequences of these events are still poorly understood. Here, we directed LRRK2 to lysosomes and early endosomes, triggering both LRRK2 autophosphorylation and phosphorylation of the direct LRRK2 substrates Rab10 and Rab12. However, when directed to the lysosomal membrane, pRab10 was restricted to perinuclear lysosomes, whereas pRab12 was visualized on both peripheral and perinuclear LRRK2+ lysosomes, suggesting that lysosomal positioning provides additional regulation of LRRK2-dependent Rab phosphorylation. Anterograde transport of lysosomes to the cell periphery by increasing the expression of ARL8B and SKIP or by knockdown of JIP4 blocked the recruitment and phosphorylation of Rab10 by LRRK2. The absence of pRab10 from the lysosomal membrane prevented the formation of a lysosomal tubulation and sorting process we previously named LYTL. Conversely, overexpression of RILP resulted in lysosomal clustering within the perinuclear area and increased LRRK2-dependent Rab10 recruitment and phosphorylation. The regulation of Rab10 phosphorylation in the perinuclear area depends on counteracting phosphatases, as the knockdown of phosphatase PPM1H significantly increased pRab10 signal and lysosomal tubulation in the perinuclear region. Our findings suggest that LRRK2 can be activated at multiple cellular membranes, including lysosomes, and that lysosomal positioning further provides the regulation of some Rab substrates likely via differential phosphatase activity or effector protein presence in nearby cellular compartments.
    Keywords:  JIP4; LLOMe; LYTL; Parkinson's disease; kinase
    DOI:  https://doi.org/10.1073/pnas.2205492119
  24. New Phytol. 2022 Oct 20.
    Engineered AIM-based selective autophagy to degrade proteins and organelles in planta.
    Na Luo, Dandan Shang, Zhiwei Tang, Jinyan Mai, Xiao Huang, Li-Zhen Tao, Linchuan Liu, Caiji Gao, Yangwen Qian, Qingjun Xie, Faqiang Li.
      ● Protein-targeting technologies represent essential approaches in biological research. Protein knockdown tools developed recently in mammalian cells by exploiting natural degradation mechanisms allow for precise determination of protein function and discovery of degrader-type drugs. However, no method to directly target endogenous proteins for degradation is currently available in plants. ● Here, we describe a novel method for targeted protein clearance by engineering an autophagy receptor with a binder to provide target specificity and an ATG8-binding motif (AIM) to link the targets to nascent autophagosomes, thus harnessing the autophagy machinery for degradation. ● We demonstrate its specificity and broad potentials by degrading various fluorescence-tagged proteins, including cytosolic mCherry, the nucleus-localized bZIP transcription factor TGA5, and the plasma membrane-anchored brassinosteroid receptor BRI1, as well as fluorescence-coated peroxisomes, using a tobacco-based transient expression system. Stable expression of AIM-based autophagy receptors in Arabidopsis further confirms the feasibility of this approach in selective autophagy of endogenous proteins. ● With its wide substrate scope and its specificity, our concept of engineered AIM-based selective autophagy could provide a convenient and robust research tool for manipulating endogenous proteins in plants and may open an avenue toward degradation of cytoplasmic components other than proteins for plant research.
    Keywords:  ATG8; ATG8-interacting motif; Autophagy; Autophagy receptor; Selective autophagy; nanobody; targeted protein degradation; vacuole
    DOI:  https://doi.org/10.1111/nph.18557
  25. Anal Chem. 2022 Oct 19.
    Super-Resolution Imaging of Autophagy by a Preferred Pair of Self-Labeling Protein Tags and Fluorescent Ligands.
    Huizi Man, Lin Zhou, Guanghao Zhu, Ying Zheng, Zhiwei Ye, Zhenlong Huang, Xinru Teng, Chunzhi Ai, Guangbo Ge, Yi Xiao.
      Autophagy is a core recycling process for homeostasis, with its dysfunction associated with tumorigenesis and various diseases. Yet, its subtle intracellular details are covered due to the limited resolution of conventional microscopies. The major challenge for modern super-resolution microscopy deployment is the lack of a practical labeling system, which could provide robust fluorescence with fidelity in the context of the dynamic autophagy microenvironment. Herein, a representative autophagy marker LC3 protein is selected to develop two hybrid self-labeling systems with tetramethylrhodamine (TMR) fluorophores through SNAP/Halo-tag technologies. A systematic investigation indicated that the match of the LC3-Halo and TMR ligand remarkably outperforms that of LC3-SNAP, as the former Halo system exhibited more robust single-molecule brightness (440 vs 247), total photon numbers (45600 vs 13500), and dwell time of the initial bright state (0.82 vs 0.40 s) than the latter. With the aid of this desirable Halo system, for the first time, live-cell ferritinophagy is monitored with a spatial resolution of ∼50 nm, which disclosed reduced sizes of autophagosomes (∼650 nm, ferritinophagy) than those in nonselective (∼840 nm, mammalian target of rapamycin (mTOR)) and selective autophagy (∼900 nm, mitophagy).
    DOI:  https://doi.org/10.1021/acs.analchem.2c03125
  26. Biochem J. 2022 Oct 18. pii: BCJ20220271. [Epub ahead of print]
    Methylglyoxal induces multiple serine phosphorylation in insulin receptor substrate 1 via the TAK1-p38-mTORC1 signaling axis in adipocytes.
    Su-Ping Ng, Wataru Nomura, Haruya Takahashi, Kazuo Inoue, Teruo Kawada, Tsuyoshi Goto, Yoshiharu Inoue.
      Certain metabolic intermediates produced during metabolism are known to regulate a wide range of cellular processes. Methylglyoxal (MG), a natural metabolite derived from glycolysis, has been shown to negatively influences systemic metabolism by inducing glucose intolerance, insulin resistance, and diabetic complications. MG plays a functional role as a signaling molecule that initiates signal transduction. However, the specific relationship between MG-induced activation of signal transduction and its negative effects on metabolism remains unclear. Here, we found that MG activated mammalian target of rapamycin complex 1 (mTORC1) signaling via p38 mitogen-activated protein kinase in adipocytes, and that the transforming growth factor-b-activated kinase 1 (TAK1) is needed to activate p38-mTORC1 signaling following treatment with MG. We also found that MG increased the phosphorylation levels of serine residues in insulin receptor substrate (IRS)-1, which is involved in its negative regulation, thereby attenuating insulin-stimulated tyrosine phosphorylation in IRS-1. The negative effect of MG on insulin-stimulated IRS-1 tyrosine phosphorylation was exerted due to the MG-induced activation of the TAK1-p38-mTORC1 signaling axis. The involvement of the TAK1-p38-mTORC1 signaling axis in the induction of IRS-1 multiple serine phosphorylation was not unique to MG, as the proinflammatory cytokine, tumor necrosis factor-α, also activated the same signaling axis. Therefore, our findings suggest that MG-induced activation of the TAK1-p38-mTORC1 signaling axis caused multiple serine phosphorylation on IRS-1, potentially contributing to insulin resistance.
    Keywords:  TAK1; adipocytes; insulin signalling; mTOR; methylglyoxal; signalling
    DOI:  https://doi.org/10.1042/BCJ20220271
  27. Sci Total Environ. 2022 Oct 12. pii: S0048-9697(22)06531-7. [Epub ahead of print] 159432
    Cobalt induces neurodegenerative damages through impairing autophagic flux by activating hypoxia-inducible factor-1α triggered ROS overproduction.
    Jianping Tang, Yanjun Li, Xu Liu, Guangxia Yu, Fuli Zheng, Zhenkun Guo, Yating Zhang, Wenya Shao, Siying Wu, Huangyuan Li.
      Cobalt is an environmental toxicant, and excessive bodily exposure can damage the nervous system. Particularly, our previous study reported that low-dose cobalt (significantly less than the safety threshold) is still able to induce neurodegenerative changes. However, the underlying molecular mechanism is still insufficient revealed. Herein, we further investigate the molecular mechanism between cobalt-induced neurodegeneration and autophagy, as well as explore the interplay between hypoxia-inducible factor-1α (HIF-1α), reactive oxygen species (ROS), and autophagy in cobalt-exposed mice and human neuroglioma cells. We first reveal cobalt as an environmental toxicant to severely induce β amyloid (Aβ) deposition, tau hyperphosphorylation, and dysregulated autophagy in the hippocampus and cortex of mice. In particular, we further identify that cobalt-induced neurotoxicity is triggered by the impairment of autophagic flux in vitro experiments. Moreover, the mechanistic study reveals that cobalt exposure extremely activates HIF-1α expression to facilitate the overproduction of ROS. Then, elevated ROS can target the amino-threonine kinase (AKT)-mammalian target of rapamycin (mTOR)-Unc-51 like autophagy activating kinase 1 (ULK1) signaling pathway to participate in cobalt-induced impairment of autophagic flux. Subsequently, defected autophagy further exacerbates cobalt-induced neurotoxicity for its unable to eliminate the deposition of pathological protein. Therefore, our data provide scientific evidence for cobalt safety evaluation and risk assessment and propose a breakthrough for understanding the regulatory relationship between HIF-1α, ROS, and autophagy in cobalt-induced neurodegeneration.
    Keywords:  Autophagy; CoCl(2) exposure; HIF-1α; Neurodegeneration; ROS
    DOI:  https://doi.org/10.1016/j.scitotenv.2022.159432
  28. Am J Physiol Cell Physiol. 2022 Oct 17.
    Temporal analysis of skeletal muscle remodelling post hindlimb ischemia reveals intricate autophagy regulation.
    Mattia Scalabrin, Viktor Engman, Amanda Maccannell, Annabel Critchlow, Lee D Roberts, Nadira Yudalsheva, T Scott Bowen.
      Hind Limb Ischemia (HLI) is the most severe form of peripheral arterial disease, associated with a substantial reduction of limb blood flow that impairs skeletal muscle homeostasis to promote functional disability. The molecular regulators of HLI-induced muscle perturbations remain poorly defined. This study investigated whether perturbations in the molecular catabolic-autophagy signalling network were linked to temporal remodelling of skeletal muscle in HLI. HLI was induced via hindlimb ischemia (femoral artery ligation) and confirmed by Doppler echocardiography. Experiments were terminated at time points defined as early- (7 days; n=5) or late (28 days; n=5) stage HLI. Ischemic and non-ischemic (contralateral) limb muscles were compared. Ischemic vs. non-ischemic muscles demonstrated overt remodelling at early-HLI but normalised at late-HLI. Early-onset fibre atrophy was associated with excessive autophagy signalling in ischemic muscle: protein expression increased for Beclin-1, LC3 and p62 (p<0.05) but proteasome-dependent markers were reduced (p<0.05). Mitophagy signalling increased in early-stage HLI which aligned with an early and sustained loss of mitochondrial content (p<0.05). Upstream autophagy regulators Sestrins showed divergent responses during early-stage HLI (Sestrin2 increased while Sestrin1 decreased; p<0.05) in parallel to increased AMPK phosphorylation (p<0.05) and lower antioxidant enzyme expression. No changes were found in markers for mTORC1 signalling. These data indicate early-activation of the sestrin-AMPK signalling axis may regulate autophagy to stimulate rapid and overt muscle atrophy in HLI, which is normalised within weeks and accompanied by recovery of muscle mass. A complex interplay between Sestrins to regulate autophagy signalling during early-to-late muscle remodelling in HLI is likely.
    Keywords:  Autophagy; Ischemia; Sestrins; Skeletal Muscle
    DOI:  https://doi.org/10.1152/ajpcell.00174.2022
  29. FEBS Lett. 2022 Oct 20.
    Cellular and physiological roles of the conserved atypical MAP kinase ERK7.
    Onur Deniz, Kiran Hasygar, Ville Hietakangas.
      Extracellular signal-regulated kinase 7 (ERK7), also known as ERK8 and MAPK15, is an atypical member of the MAP kinase family. Compared with other MAP kinases, the biological roles of ERK7 remain poorly understood. Recent work, however, has revealed several novel functions for ERK7. These include a highly conserved essential role in ciliogenesis, the ability to control cell growth, metabolism, and autophagy, as well as maintenance of genomic integrity. ERK7 functions through phosphorylation-dependent and -independent mechanisms and it is activated by cellular stressors, including DNA damaging agents, and nutrient deprivation. Here, we summarize recent developments in the understanding of ERK7 function, emphasizing its conserved roles in cellular and physiological regulation.
    Keywords:  DNA damage; Toxoplasma; adiposity; apical complex; autophagy; cilia; growth control; kinase; nutrient sensing; phosphorylation; signaling
    DOI:  https://doi.org/10.1002/1873-3468.14521
  30. Food Chem Toxicol. 2022 Oct 13. pii: S0278-6915(22)00667-6. [Epub ahead of print]170 113469
    Silver nanoparticle-induced impaired autophagic flux and lysosomal dysfunction contribute to the microglia inflammation polarization.
    Mengting Shang, Shuyan Niu, Xiaoru Chang, Jiangyan Li, Wenli Zhang, Menghao Guo, Tianshu Wu, Ting Zhang, Meng Tang, Yuying Xue.
      Silver nanoparticles (AgNPs) have been incorporated in many consumer and biomedical products. Serious concerns have been expressed about the environmental and public health risks caused by nanoparticles. In previous studies, we found that AgNPs induced microglia polarization of the inflammatory phenotype. Autophagy was a critical for AgNPs-induced neuroinflammation. In the present study, we evaluated in detail the effects of AgNPs in different stages of the autophagy process, and we found that AgNPs induced neuroinflammatory responses and autophagic flux blockage both in the mouse brain and BV2 cells. AgNPs inhibited autophagosome-lysosome fusion and impaired the lysosomal functions by reducing the levels of lysosomal-associated membrane proteins, promoting lysosome membrane permeability and altering the lysosomal acidic microenvironment. These changes resulted in the defects in autophagic substrate clearance and subsequently led neuroinflammation. In addition, the elevation of autophagy could prevent the neuroinflammation induced by AgNPs. As a result, AgNPs hindered autophagic flux by inhibiting autophagosome fusion with lysosomes, thus aggravating the AgNPs-induced neurotoxicity. These findings will provide new insights to investigate the molecular mechanisms of neurotoxicity caused by AgNPs.
    Keywords:  AgNPs; Autophagosome–lysosome fusion; Autophagy; Lysosome; Neuroinflammation
    DOI:  https://doi.org/10.1016/j.fct.2022.113469
  31. Mol Neurobiol. 2022 Oct 20.
    Treadmill Exercise Improves PINK1/Parkin-Mediated Mitophagy Activity Against Alzheimer's Disease Pathologies by Upregulated SIRT1-FOXO1/3 Axis in APP/PS1 Mice.
    Na Zhao, Xianliang Zhang, Baixia Li, Jing Wang, Chenfei Zhang, Bo Xu.
      Although treadmill exercise is effective against Alzheimer's disease (AD), the molecular mechanisms underlying these effects are not fully understood. Recent literature has linked the accumulation of damaged mitochondria and defective mitophagy to AD progression. Here, we determined that abnormally activated PINK1/Parkin pathway-mediated mitophagy plays an important role in AD progression and pathogenesis in 6-month-old APP/PS1 mice. We used the lysosomal inhibitor chloroquine and demonstrated that a 12-week treadmill exercise program improved mitochondrial function, decreased accumulation of β-amyloid plaques, and ameliorated loss of learning and memory ability by enhancing PINK1/Parkin-mediated mitophagy activity in the hippocampus of APP/PS1 mice. Moreover, using the SIRT1 inhibitor EX527, we found that 12 weeks of treadmill exercise rescued PINK1/Parkin-mediated mitophagy by activating the SIRT1-FOXO1/3 axis in the hippocampus of APP/PS1 mice. These findings reveal that activating PINK1/Parkin-mediated mitophagy is a promising strategy for AD treatment, and that the SIRT1-FOXO1/3 axis is a potential candidate for the development of mitophagy enhancers.
    Keywords:  Alzheimer’s disease; Mitophagy; PINK1/Parkin; SIRT1-FOXO1/3; Treadmill exercise
    DOI:  https://doi.org/10.1007/s12035-022-03035-7
  32. Adv Neurobiol. 2023 ;29 333-390
    Neuronal Ganglioside and Glycosphingolipid (GSL) Metabolism and Disease : Cascades of Secondary Metabolic Errors Can Generate Complex Pathologies (in LSDs).
    Roger Sandhoff, Konrad Sandhoff.
      Glycosphingolipids (GSLs) are a diverse group of membrane components occurring mainly on the surfaces of mammalian cells. They and their metabolites have a role in intercellular communication, serving as versatile biochemical signals (Kaltner et al, Biochem J 476(18):2623-2655, 2019) and in many cellular pathways. Anionic GSLs, the sialic acid containing gangliosides (GGs), are essential constituents of neuronal cell surfaces, whereas anionic sulfatides are key components of myelin and myelin forming oligodendrocytes. The stepwise biosynthetic pathways of GSLs occur at and lead along the membranes of organellar surfaces of the secretory pathway. After formation of the hydrophobic ceramide membrane anchor of GSLs at the ER, membrane-spanning glycosyltransferases (GTs) of the Golgi and Trans-Golgi network generate cell type-specific GSL patterns for cellular surfaces. GSLs of the cellular plasma membrane can reach intra-lysosomal, i.e. luminal, vesicles (ILVs) by endocytic pathways for degradation. Soluble glycoproteins, the glycosidases, lipid binding and transfer proteins and acid ceramidase are needed for the lysosomal catabolism of GSLs at ILV-membrane surfaces. Inherited mutations triggering a functional loss of glycosylated lysosomal hydrolases and lipid binding proteins involved in GSL degradation cause a primary lysosomal accumulation of their non-degradable GSL substrates in lysosomal storage diseases (LSDs). Lipid binding proteins, the SAPs, and the various lipids of the ILV-membranes regulate GSL catabolism, but also primary storage compounds such as sphingomyelin (SM), cholesterol (Chol.), or chondroitin sulfate can effectively inhibit catabolic lysosomal pathways of GSLs. This causes cascades of metabolic errors, accumulating secondary lysosomal GSL- and GG- storage that can trigger a complex pathology (Breiden and Sandhoff, Int J Mol Sci 21(7):2566, 2020).
    Keywords:  Alzheimer; Catabolism; Degradation; Development; Endosomal pathway; Frontal lobe dementia; Ganglio-series; Ganglioside; Genetic disease; Glycolipid; Glycosphingolipid; Glycosyltransferase; Hydrolase; Intra-lysosomal luminal vesicle (ILV); Lysosomal storage disease (LSD); Lysosome; Membrane-surface; Metabolism; Neurodegenerative disease; Neuron; Organelle; Parkinson; Receptor; Secondary storage; Secretory pathway; Sphingolipid-binding protein (SAP); Sphingolipid-transfer protein; Topology
    DOI:  https://doi.org/10.1007/978-3-031-12390-0_12
  33. Mol Ther. 2022 Oct 18. pii: S1525-0016(22)00613-X. [Epub ahead of print]
    The Amyloid Inhibitor CLR01 Relieves Autophagy and Ameliorates Neuropathology in a Severe Lysosomal Storage Disease.
    Antonio Monaco, Veronica Maffia, Nicolina Cristina Sorrentino, Irene Sambri, Yulia Ezhova, Teresa Giuliano, Vincenzo Cacace, Edoardo Nusco, Maria De Risi, Elvira De Leonibus, Thomas Schrader, Frank-Gerrit Klärner, Gal Bitan, Alessandro Fraldi.
      
    DOI:  https://doi.org/10.1016/j.ymthe.2022.10.001
  34. PLoS One. 2022 ;17(10): e0276579
    Inhibiting glutamine utilization creates a synthetic lethality for suppression of ATP citrate lyase in KRas-driven cancer cells.
    Ahmet Hatipoglu, Deepak Menon, Talia Levy, Maria A Frias, David A Foster.
      Metabolic reprogramming is now considered a hallmark of cancer cells. KRas-driven cancer cells use glutaminolysis to generate the tricarboxylic acid cycle intermediate α-ketoglutarate via a transamination reaction between glutamate and oxaloacetate. We reported previously that exogenously supplied unsaturated fatty acids could be used to synthesize phosphatidic acid-a lipid second messenger that activates both mammalian target of rapamycin (mTOR) complex 1 (mTORC1) and mTOR complex 2 (mTORC2). A key target of mTORC2 is Akt-a kinase that promotes survival and regulates cell metabolism. We report here that mono-unsaturated oleic acid stimulates the phosphorylation of ATP citrate lyase (ACLY) at the Akt phosphorylation site at S455 in an mTORC2 dependent manner. Inhibition of ACLY in KRas-driven cancer cells in the absence of serum resulted in loss of cell viability. We examined the impact of glutamine (Gln) deprivation in combination with inhibition of ACLY on the viability of KRas-driven cancer cells. While Gln deprivation was somewhat toxic to KRas-driven cancer cells by itself, addition of the ACLY inhibitor SB-204990 increased the loss of cell viability. However, the transaminase inhibitor aminooxyacetate was minimally toxic and the combination of SB-204990 and aminooxtacetate led to significant loss of cell viability and strong cleavage of poly-ADP ribose polymerase-indicating apoptotic cell death. This effect was not observed in MCF7 breast cancer cells that do not have a KRas mutation or in BJ-hTERT human fibroblasts which have no oncogenic mutation. These data reveal a synthetic lethality between inhibition of glutamate oxaloacetate transaminase and ACLY inhibition that is specific for KRas-driven cancer cells and the apparent metabolic reprogramming induced by activating mutations to KRas.
    DOI:  https://doi.org/10.1371/journal.pone.0276579
  35. Neural Regen Res. 2023 May;18(5): 1009-1016
    Myelinosome organelles in pathological retinas: ubiquitous presence and dual role in ocular proteostasis maintenance.
    Marina G Yefimova.
      The timely and efficient elimination of aberrant proteins and damaged organelles, formed in response to various genetic and environmental stressors, is a vital need for all cells of the body. Recent lines of evidence point out several non-classical strategies employed by ocular tissues to cope with aberrant constituents generated in the retina and in the retinal pigmented epithelium cells exposed to various stressors. Along with conventional strategies relying upon the intracellular degradation of aberrant constituents through ubiquitin-proteasome and/or lysosome-dependent autophagy proteolysis, two non-conventional mechanisms also contribute to proteostasis maintenance in ocular tissues. An exosome-mediated clearing and a myelinosome-driven secretion mechanism do not require intracellular degradation but provide the export of aberrant constituents and "waste proteins" outside of the cells. The current review is centered on the non-degradative myelinosome-driven secretion mechanism, which operates in the retina of transgenic Huntington's disease R6/1 model mice. Myelinosome-driven secretion is supported by rare organelles myelinosomes that are detected not only in degenerative Huntington's disease R6/1 retina but also in various pathological states of the retina and of the retinal pigmented epithelium. The intra-retinal traffic and inter-cellular exchange of myelinosomes was discussed in the context of a dual role of the myelinosome-driven secretion mechanism for proteostasis maintenance in different ocular compartments. Special focus was made on the interplay between degradative and non-degradative strategies in ocular pathophysiology, to delineate potential therapeutic approaches to counteract several vision diseases.
    Keywords:  Huntington’s disease; Müller cells; autophagy; myelinosome-driven secretion; myelinosomes; ocular pathophysiology; proteostasis; retina; retinal pigmented epithelium; ubiquitin-proteasome system
    DOI:  https://doi.org/10.4103/1673-5374.355753
  36. Anal Chem. 2022 Oct 19.
    Tracking Autophagy Process with a TBET and AIE-Based Ratiometric Two-Photon Viscosity Probe.
    Shengze Su, Li Chai, Qian An, Wei Hu, Lina Wang, Xingcan Li, Huijuan Zhang, Chunya Li.
      Autophagy is a cellular self-degrading process that plays a key role in cellular health and functioning. Since autophagy disorder is related to many diseases, it is highly important to detect autophagy. This study aimed to establish a dual-sensing mechanism-based ratiometric viscosity-sensitive lysosome-targeted two-photon fluorescent probe Vis-sun to track the autophagy process (the increase in lysosome viscosity during autophagy) by combining through bond energy transfer (TBET) and aggregation-induced emission (AIE). The introduction of TBET not only overcame the interference of background signals but also achieved the baseline separation of two emission peaks, thus reducing the crosstalk between emissions, as well as the noninvasive bio-sensing of biological targets and long-term real-time tracer imaging by introducing AIE. In vitro experiments showed that the fluorescence intensity at 485 nm decreased gradually on increasing the volume ratio of water to tetrahydrofuran (Vwater/VTHF), while the fluorescence intensity at 605 nm increased significantly. Also, the fluorescence signal was maximized when the water content reached 100%. At the same time, the probe exhibited a significant dependence on the ambient viscosity. Therefore, the dynamic monitoring of lysosome viscosity during autophagy and the in situ imaging of autophagy fluctuations during stroke-induced neuroinflammation were successfully achieved by implementing Vis-sun lysosome anchoring with morpholine.
    DOI:  https://doi.org/10.1021/acs.analchem.2c03555
  37. Cell Rep Med. 2022 Oct 18. pii: S2666-3791(22)00333-0. [Epub ahead of print]3(10): 100778
    Targeting LRRK2 in Parkinson's disease.
    Bin Xiao, Eng-King Tan.
      Jennings et al.1 reported that LRRK2 inhibitors can reduce kinase activity and improve lysosomal function with minor adverse effects in both animal models and human subjects. The findings provide proof of principle for LRRK2 inhibitor as a Parkinson's disease therapeutic option.
    DOI:  https://doi.org/10.1016/j.xcrm.2022.100778
  38. Front Physiol. 2022 ;13 949737
    RagC GTPase regulates mTOR to promote chemoresistance in senescence-like HepG2 cells.
    Wei Jiang, Zhenglin Ou, Qin Zhu, Hongyan Zai.
      Radiotherapy and chemotherapy can arrest cancer cells in a senescence-like state, which can lead to therapy resistance and cancer relapse. mTOR is hyperactivated in senescent cells but the mechanisms remain unclear. In this study, we examine the roles of several mTOR-regulated GTPases in senescence-like liver cancer cells and the mechanisms in drug resistance. We show that although RagC, Rheb, Rab1A, Rab5 and Arf1 GTPases were required for optimal mTOR activation in proliferating HepG2 cells, only RagC and Rheb are required in the senescence-like counterparts. Consistently, the drug resistance of the senescence-like HepG2 can be reduced by knocking down RagC and Rheb but not the other GTPases. Autophagic and lysosomal activity were increased in senescence-like cells; pharmacological inhibition of autophagy-lysosome decreased mTOR activity and preferentially sensitized senescence-like HepG2 cells to chemotherapy drugs including trametinib, cisplatin, and doxorubicin. In liver cancer patients, expression of RagC and Rheb but not other GTPases examined was associated with unfavorable prognosis. Our study therefore has defined a key role of Rag-Rheb GTPase in mediating mTOR activation and drug resistance in senescence-like HepG2 cells, which could have important implications in developing second-line treatments for liver cancer patients.
    Keywords:  GTPase; chemoresistance; liver cancer; mTOR; senescence
    DOI:  https://doi.org/10.3389/fphys.2022.949737
  39. Nat Commun. 2022 Oct 20. 13(1): 6212
    Cross-linking of the endolysosomal system reveals potential flotillin structures and cargo.
    Jasjot Singh, Hadeer Elhabashy, Pathma Muthukottiappan, Markus Stepath, Martin Eisenacher, Oliver Kohlbacher, Volkmar Gieselmann, Dominic Winter.
      Lysosomes are well-established as the main cellular organelles for the degradation of macromolecules and emerging as regulatory centers of metabolism. They are of crucial importance for cellular homeostasis, which is exemplified by a plethora of disorders related to alterations in lysosomal function. In this context, protein complexes play a decisive role, regulating not only metabolic lysosomal processes but also lysosome biogenesis, transport, and interaction with other organelles. Using cross-linking mass spectrometry, we analyze lysosomes and early endosomes. Based on the identification of 5376 cross-links, we investigate protein-protein interactions and structures of lysosome- and endosome-related proteins. In particular, we present evidence for a tetrameric assembly of the lysosomal hydrolase PPT1 and a heterodimeric structure of FLOT1/FLOT2 at lysosomes and early endosomes. For FLOT1-/FLOT2-positive early endosomes, we identify >300 putative cargo proteins and confirm eleven substrates for flotillin-dependent endocytosis, including the latrophilin family of adhesion G protein-coupled receptors.
    DOI:  https://doi.org/10.1038/s41467-022-33951-0
  40. Mol Neurodegener. 2022 Oct 17. 17(1): 66
    Tau interactome and RNA binding proteins in neurodegenerative diseases.
    Tomas Kavanagh, Aditi Halder, Eleanor Drummond.
      Pathological tau aggregation is a primary neuropathological feature of many neurodegenerative diseases. Intriguingly, despite the common presence of tau aggregates in these diseases the affected brain regions, clinical symptoms, and morphology, conformation, and isoform ratio present in tau aggregates varies widely. The tau-mediated disease mechanisms that drive neurodegenerative disease are still unknown. Tau interactome studies are critically important for understanding tauopathy. They reveal the interacting partners that define disease pathways, and the tau interactions present in neuropathological aggregates provide potential insight into the cellular environment and protein interactions present during pathological tau aggregation. Here we provide a combined analysis of 12 tau interactome studies of human brain tissue, human cell culture models and rodent models of disease. Together, these studies identified 2084 proteins that interact with tau in human tissue and 1152 proteins that interact with tau in rodent models of disease. Our combined analysis of the tau interactome revealed consistent enrichment of interactions between tau and proteins involved in RNA binding, ribosome, and proteasome function. Comparison of human and rodent tau interactome studies revealed substantial differences between the two species. We also performed a second analysis to identify the tau interacting proteins that are enriched in neurons containing granulovacuolar degeneration or neurofibrillary tangle pathology. These results revealed a timed dysregulation of tau interactions as pathology develops. RNA binding proteins, particularly HNRNPs, emerged as early disease-associated tau interactors and therefore may have an important role in driving tau pathology.
    Keywords:  Alzheimer’s disease; Frontotemporal dementia; HNRNP; Interactome; Neurofibrillary tangle; Protein–protein interactions; RNA binding proteins; Tau; Tauopathy
    DOI:  https://doi.org/10.1186/s13024-022-00572-6
  41. J Physiol. 2022 Oct 18.
    Inducible deletion of Raptor and mTOR from adult skeletal muscle impairs muscle contractility and relaxation.
    Martina Baraldo, Sabrina Zorzato, Achille Homère Tchampda Dondjang, Alessia Geremia, Leonardo Nogara, Ana Georgia Dumitras, Marta Canato, Lorenzo Marcucci, Hendrik Nolte, Bert Blaauw.
       KEY POINTS: Skeletal muscle wasting and weakness have been associated with different pathological conditions, including sarcopenia and muscular dystrophy, and is accompanied by altered mTOR signaling Mammalian Target of Rapamycin (mTOR) plays a crucial role in the maintenance of muscle mass and functionality We found that the loss of both mTOR and Raptor results in contractile abnormalities, with severe muscle weakness and delayed relaxation following tetanic stimulation These results are associated with alterations in the expression of genes involved in sarcomere organization and calcium handling, and with an impairment in calcium reuptake after contraction Taken together, these results reveal a mechanistic insight into the role of mTOR in muscle contractility ABSTRACT: Skeletal muscle weakness has been associated with different pathological conditions, including sarcopenia and muscular dystrophy, and is accompanied by altered mTOR signaling. Here we wanted to better elucidate the functional role of mTOR on muscle contractility. Most loss of function studies for mTOR signaling have used the drug rapamycin to inhibit some of the signaling downstream of mTOR. However, as rapamycin does not completely inhibit all mTOR signaling, we generated a double k.o. for mTOR and for the scaffold protein of mTORC1, Raptor, in skeletal muscle. We found that dk.o. mice results in a more severe phenotype compared to Raptor or mTOR deletion alone. Indeed, they display muscle weakness, increased fiber denervation, and a slower muscle relaxation following tetanic stimulation. This is accompanied by a shift towards slow-twitch fibers and changes in the expression levels of calcium-related genes, like Serca1 and Casq1. Indeed, dk.o. mice show a decrease in calcium decay kinetics after tetanus in vivo, suggestive of a reduced calcium reuptake. In addition, RNA sequencing analysis revealed that many downregulated genes are linked to sarcomere organization, like Tcap and Fhod3. These results suggest a key role for mTOR signaling in maintaining a proper fiber relaxation in skeletal muscle. Abstract figure legend This article is protected by copyright. All rights reserved.
    Keywords:  Raptor; calcium; mTOR; muscle force; relaxation; skeletal muscle
    DOI:  https://doi.org/10.1113/JP283686
  42. Endocrinology. 2022 Oct 18. pii: bqac170. [Epub ahead of print]
    Angiotensin II regulates mitochondrial mTOR pathway activity dependent on acyl CoA synthetase 4 in adrenocortical cells.
    Katia E Helfenberger, Giuliana F Argentino, Yanina Benzo, Lucía Herrera, Paola Finocchietto, Cecilia Poderoso.
      Two well-known protein complexes in mammalian cells, mTOR type 1 and type 2 (mTORC1/2) are involved in several cellular processes such as protein synthesis, cell proliferation and commonly dysregulated in cancer. An acyl-CoA synthetase type 4 (ACSL4) is one of the most recently mTORC1/2 regulators described, in breast cancer cells. The expression of ACSL4 is hormone-regulated in adrenocortical cells and required for steroid biosynthesis. mTORC1/2 have been reported to be crucial in the proliferation of human adrenocortical tumor cells H295R and interestingly reported at several subcellular locations, which has brought cell biology to the vanguard of the mTOR signaling field. In the present work, we study the regulation of mTORC1/2 activation by angiotensin II (Ang II) -the trophic hormone for adrenocortical cells-, the subcellular localization of mTORC1/2 signaling proteins and the role of ACSL4 in the regulation of this pathway, in H295R cells. Ang II promotes activation by phosphorylation of mTORC1/2 pathway proteins in a time-dependent manner. Mitochondrial pools of ribosomal protein S6, Akt in threonine 308 and serine 473 and Rictor are phosphorylated and activated. Glycogen synthase kinase type 3 (GSK3) is phosphorylated and inactivated in mitochondria, favoring mTORC1 activation. Epidermal growth factor, a classic mTORC1/2 activator, promoted unique activation kinetics of mTORC1/2 pathway, except for Akt phosphorylation. Here, we demonstrate that ACSL4 is necessary for mTORC1/2 effectors phosphorylation and H295R proliferation, triggered by Ang II. Ang II promotes activation of mitochondrial mTORC1/2 signaling proteins, through ACSL4, with a direct impact on adrenocortical cellular proliferation.
    Keywords:  acyl-CoA synthetase type 4; adrenocortical human cells; angiotensin II; compartmentalization; mTORC proteins; mitochondria
    DOI:  https://doi.org/10.1210/endocr/bqac170
  43. Microbiol Spectr. 2022 Oct 20. e0269922
    Retinoic Acid Increases Cellular Cholesterol in Leishmania donovani-Infected Macrophages in an mTOR-Independent Manner.
    Satya Prakash, Ambak Kumar Rai.
      Infection with Leishmania donovani reduces cellular cholesterol and thus deprives the host cells by inhibiting its synthesis and uptake. Changes in cholesterol levels increase the chance of attachment and internalization of L. donovani in macrophages (Mϕ). Retinoic acid (RA), an important micronutrient, restores the lysosomal uptake of cholesterol in L. donovani-infected Mϕ. Importantly, mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1) increases the cellular cholesterol level by increasing expression of sterol regulatory element-binding protein 2 (SREBP2). Whether the efficacy of RA in L. donovani-infected Mϕ is mediated by mTOR is not yet established. Moreover, there are contradicting reports suggesting potential activation and inhibition of mTOR in L. donovani-infected Mϕ. Intrigued by this, we attempted to understand the RA-mediated restoration of cholesterol as well as the possible roles of mTORC1, if any. Our findings suggest that L. donovani infection impairs the synthesis of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), uptake of low-density lipoprotein receptor (LDLR), and secretion of ATP-binding cassette transporter (ABCA1) in Mϕ. L. donovani infection possibly impairs mTORC1 formation, as it inhibits the expression of regulatory-associated protein of mammalian target of rapamycin (RAPTOR). Importantly, all these are restored upon RA supplementation. RA also restores the levels of SREBP2 in L. donovani-infected Mϕ, resulting in increased cellular cholesterol and thus reducing the parasite burden. When mTORC1 was inhibited, RA exerted a similar response in L. donovani-infected Mϕ; i.e., it restored cholesterol levels and reduced the parasite burden. In summary, RA restores cholesterol levels in L. donovani-infected Mϕ and reduces the parasite burden in an mTOR-independent manner. IMPORTANCE People who reside in regions where leishmaniasis is endemic and who lack proteins, iron, zinc, and vitamin A in their diet are more prone to develop visceral leishmaniasis (VL) as a full-blown disease. Vitamin A deficiency favors the development of a parasitic infection in the human host, and the WHO recommends administering 200,000-IU doses to VL patients on admission. Additionally, Leishmania entry and its survival inside the host are achieved by utilizing host cholesterol, as all trypanosomatids lack de novo synthesis of sterol. We have already shown that RA regulates cellular cholesterol levels associated with an efficient immune response. A deficiency of retinoic acid (RA) favors the parasite in Leishmania donovani-infected macrophages by downregulating the immune response. In the present work, we observed that RA restores cellular cholesterol levels in Leishmania donovani-infected macrophages. This study proposes using RA as an immune potentiator along with standard therapy.
    Keywords:  Leishmania; cholesterol; mTOR; retinoic acid
    DOI:  https://doi.org/10.1128/spectrum.02699-22
  44. J Clin Invest. 2022 Oct 20. pii: e160766. [Epub ahead of print]
    Rapalogs downmodulate intrinsic immunity and promote cell entry of SARS-CoV-2.
    Guoli Shi, Abhilash I Chiramel, Tiansheng Li, Kin Kui Lai, Adam D Kenney, Ashley Zani, Adrian C Eddy, Saliha Majdoul, Lizhi Zhang, Tirhas Dempsey, Paul A Beare, Swagata Kar, Jonathan W Yewdell, Sonja M Best, Jacob S Yount, Alex A Compton.
      SARS-CoV-2 infection in immunocompromised individuals is associated with prolonged virus shedding and evolution of viral variants. Rapamycin and its analogs (rapalogs, including everolimus, temsirolimus, and ridaforolimus) are FDA-approved as mTOR inhibitors for the treatment of human diseases, including cancer and autoimmunity. Rapalog use is commonly associated with increased susceptibility to infection, which has been traditionally explained by impaired adaptive immunity. Here, we show that exposure to rapalogs increases susceptibility to SARS-CoV-2 infection in tissue culture and in immunologically naive rodents by antagonizing the cell-intrinsic immune response. By identifying one rapalog (ridaforolimus) that is less potent in this regard, we demonstrate that rapalogs promote Spike-mediated entry into cells by triggering the degradation of antiviral proteins IFITM2 and IFITM3 via an endolysosomal remodeling program called microautophagy. Rapalogs that increase virus entry inhibit the mTOR-mediated phosphorylation of the transcription factor TFEB, which facilitates its nuclear translocation and triggers microautophagy. In rodent models of infection, injection of rapamycin prior to and after virus exposure resulted in elevated SARS-CoV-2 replication and exacerbated viral disease, while ridaforolimus had milder effects. Overall, our findings indicate that preexisting use of certain rapalogs may elevate host susceptibility to SARS-CoV-2 infection and disease by activating lysosome-mediated suppression of intrinsic immunity.
    Keywords:  Autophagy; COVID-19; Innate immunity; Lysosomes
    DOI:  https://doi.org/10.1172/JCI160766
  45. Aging Cell. 2022 Oct 19. e13715
    Autophagy activation can partially rescue proteasome dysfunction-mediated cardiac toxicity.
    Eleni-Dimitra Papanagnou, Sentiljana Gumeni, Aimilia D Sklirou, Alexandra Rafeletou, Evangelos Terpos, Kleoniki Keklikoglou, Efstathios Kastritis, Kimon Stamatelopoulos, Gerasimos P Sykiotis, Meletios A Dimopoulos, Ioannis P Trougakos.
      The ubiquitin-proteasome pathway and its functional interplay with other proteostatic and/or mitostatic modules are crucial for cell viability, especially in post-mitotic cells like cardiomyocytes, which are constantly exposed to proteotoxic, metabolic, and mechanical stress. Consistently, treatment of multiple myeloma patients with therapeutic proteasome inhibitors may induce cardiac failure; yet the effects promoted by heart-targeted proteasome dysfunction are not completely understood. We report here that heart-targeted proteasome knockdown in the fly experimental model results in increased proteome instability and defective mitostasis, leading to disrupted cardiac activity, systemic toxicity, and reduced longevity. These phenotypes were partially rescued by either heart targeted- or by dietary restriction-mediated activation of autophagy. Supportively, activation of autophagy by Rapamycin or Metformin administration in flies treated with proteasome inhibitors reduced proteome instability, partially restored mitochondrial function, mitigated cardiotoxicity, and improved flies' longevity. These findings suggest that autophagic inducers represent a novel promising intervention against proteasome inhibitor-induced cardiovascular complications.
    Keywords:  autophagy; cardiotoxicity; metformin; mitostasis; proteasome inhibitor; proteostasis
    DOI:  https://doi.org/10.1111/acel.13715
  46. Exp Eye Res. 2022 Oct 14. pii: S0014-4835(22)00355-4. [Epub ahead of print] 109274
    Autophagy in the normal and diseased Cornea.
    Karina Luiza Dias-Teixeira, Mohammad Sharifian Gh, Jeff Romano, Fatemeh Norouzi, Gordon W Laurie.
      The cornea and covering tear film are together the 'objective lens' of the eye through which 80% of light is refracted. Despite exposure to a physically harsh and at times infectious or toxic environment, transparency essential for sight is in most cases maintained. Such resiliency makes the avascular cornea a superb model for the exploration of autophagy in the regulation of homeostasis with relevancy to all organs. Nonetheless, missense mutations and inflammation respectively clog or apparently overwhelm autophagic flux to create dystrophies much like in neurodegenerative diseases or further exacerbate inflammation. Here there is opportunity to generate novel topical therapies towards the restoration of homeostasis with potential broad application.
    Keywords:  Autophagy; Cornea; Disease; Eye; Homeostasis
    DOI:  https://doi.org/10.1016/j.exer.2022.109274
  47. Mol Metab. 2022 Oct 14. pii: S2212-8778(22)00184-3. [Epub ahead of print] 101615
    Resistance exercise enhances long-term mTORC1 sensitivity to leucine.
    Gommaar D'Hulst, Evi Masschelein, Katrien De Bock.
       OBJECTIVE: Exercise enhances the sensitivity of mammalian target of rapamycin complex 1 (mTORC1) to amino acids, in particular leucine. How long this enhanced sensitivity lasts, and which mechanisms control enhanced leucine-mediated mTORC1 activation following exercise is currently unknown.
    METHODS: C57BL/6J mice were exercised for one night in a resistance-braked running wheel after a 12-day acclimatization period. Mice were gavaged with a submaximal dose of L-leucine or saline acutely or 48 hours after exercise cessation, following 3 h food withdrawal. Muscles were excised 30 min after leucine administration. To study the contribution of mTORC1, we repeated those experiments but blocked mTORC1 activation using rapamycin immediately before the overnight running bout and one hour before the first dose of leucine. mTORC1 signaling, muscle protein synthesis and amino acid sensing machinery were assessed using immunoblot and qPCR. Leucine uptake was measured using L-[14C(U)]-leucine tracer labeling.
    RESULTS: When compared to sedentary conditions, leucine supplementation more potently activated mTORC1 and protein synthesis in acutely exercised muscle. This effect was observed in m. soleus but not in m. tibialis anterior nor m. plantaris. The synergistic effect in m. soleus was long-lasting as key downstream markers of mTORC1 as well as protein synthesis remained higher when leucine was administered 48 h after exercise. We found that exercise enhanced the expression of amino acid transporters and promoted uptake of leucine into the muscle, leading to higher free intramuscular leucine levels. This coincided with increased expression of activating transcription factor 4 (ATF4), a main transcriptional regulator of amino acid uptake and metabolism, and downstream activation of amino acid genes as well as leucyl-tRNA synthetase (LARS), a putative leucine sensor. Finally, blocking mTORC1 using rapamycin did not reduce expression and activation of ATF4, suggesting that the latter does not act downstream of mTORC1. Rather, we found a robust increase in eukaryotic initiation factor 2α (eIF2α) phosphorylation, suggesting that the integrated stress response pathway, rather than exercise-induced mTORC1 activation, drives long-term ATF4 expression in skeletal muscle after exercise.
    CONCLUSIONS: The enhanced sensitivity of mTORC1 to leucine is maintained at least 48 h after exercise. This shows that the anabolic window of opportunity for protein ingestion is not restricted to the first hours immediately following exercise. Increased mTORC1 sensitivity to leucine coincided with enhanced leucine influx into muscle and higher expression of genes involved in leucine sensing and amino acid metabolism. Also, exercise induced an increase in ATF4 protein expression. Altogether, these data suggest that muscular contractions switch on a coordinated program to enhance amino acid uptake as well as intramuscular sensing of key amino acids involved in mTORC1 activation and the stimulation of muscle protein synthesis.
    Keywords:  ATF4; exercise; leucine; mTOR; sensitivity
    DOI:  https://doi.org/10.1016/j.molmet.2022.101615
  48. J Cell Biol. 2022 Dec 05. pii: e202203139. [Epub ahead of print]221(12):
    Plant autophagosomes mature into amphisomes prior to their delivery to the central vacuole.
    Jierui Zhao, Mai Thu Bui, Juncai Ma, Fabian Künzl, Lorenzo Picchianti, Juan Carlos De La Concepcion, Yixuan Chen, Sofia Petsangouraki, Azadeh Mohseni, Marta García-Leon, Marta Salas Gomez, Caterina Giannini, Dubois Gwennogan, Roksolana Kobylinska, Marion Clavel, Swen Schellmann, Yvon Jaillais, Jiri Friml, Byung-Ho Kang, Yasin Dagdas.
      Autophagosomes are double-membraned vesicles that traffic harmful or unwanted cellular macromolecules to the vacuole for recycling. Although autophagosome biogenesis has been extensively studied, autophagosome maturation, i.e., delivery and fusion with the vacuole, remains largely unknown in plants. Here, we have identified an autophagy adaptor, CFS1, that directly interacts with the autophagosome marker ATG8 and localizes on both membranes of the autophagosome. Autophagosomes form normally in Arabidopsis thaliana cfs1 mutants, but their delivery to the vacuole is disrupted. CFS1's function is evolutionarily conserved in plants, as it also localizes to the autophagosomes and plays a role in autophagic flux in the liverwort Marchantia polymorpha. CFS1 regulates autophagic flux by bridging autophagosomes with the multivesicular body-localized ESCRT-I component VPS23A, leading to the formation of amphisomes. Similar to CFS1-ATG8 interaction, disrupting the CFS1-VPS23A interaction blocks autophagic flux and renders plants sensitive to nitrogen starvation. Altogether, our results reveal a conserved vacuolar sorting hub that regulates autophagic flux in plants.
    DOI:  https://doi.org/10.1083/jcb.202203139
  49. Ageing Res Rev. 2022 Oct 13. pii: S1568-1637(22)00198-2. [Epub ahead of print]82 101756
    Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases.
    Mathew George, Matthan Tharakan, John Culberson, Arubala P Reddy, P Hemachandra Reddy.
      Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.
    Keywords:  Alzheimer’s disease; Huntington’s disease; Mitochondria; Mitochondrial biogenesis; Nuclear factor-erythroid factor 2; Oxidative stress; Parkinson’s disease
    DOI:  https://doi.org/10.1016/j.arr.2022.101756
  50. Microb Pathog. 2022 Oct 12. pii: S0882-4010(22)00439-9. [Epub ahead of print] 105826
    Wnt5a regulates autophagy in Bacille Calmette-Guérin (BCG)-Infected pulmonary epithelial cells.
    Qi Chen, Xuedi Zheng, Yong Li, Boli Ma, Xueyi Nie, Mengyuan Li, Yueyang Liu, Jinrui Xu, Yi Yang.
      Autophagy functions as a critical process that can suppress the proliferation of Mycobacterium tuberculosis (Mtb) within infected host cells. Wnt5a is a secreted protein that plays a range of physiological functions, activating several signaling pathways and thereby controlling cellular responses to particular stimuli. The importance of Wnt5a as a regulator of protection against Mtb infection, however, has yet to be fully characterized. Here, changes in murine pulmonary epithelial-like TC-1 cell morphology, autophagy, the Wnt/Ca2+ signaling pathway, and the mTOR autophagy pathway were analyzed following infection with the Mtb model pathogen Bacille Calmette-Guerin (BCG) in order to understand the regulatory role of Wnt5a in this context. These experiments revealed that Wnt5a was upregulated and autophagy was enhanced in TC-1 cells infected with BCG, and Wnt5a overexpression was found to drive BCG-induced autophagy in these cells upon infection, whereas the inhibition or knockdown of Wnt5a yielded the opposite effect. At the mechanistic level, Wnt5a was found to mediate non-canonical Wnt/Ca2+ signaling and thereby inhibit mTOR-dependent pathway activation, promoting autophagic induction within BCG-infected TC-1 cells. These data offer new insight regarding how Wnt5a influences Mtb-induced autophagy within pulmonary epithelial cells, providing a foundation for further research exploring the immunological control of this infection through the modulation of autophagy.
    Keywords:  Autophagy; BCG; Pulmonary epithelial cells; Wnt5a
    DOI:  https://doi.org/10.1016/j.micpath.2022.105826
  51. Front Cell Infect Microbiol. 2022 ;12 961645
    Proteomic analysis of Atg8-dependent recruitment of phagosomal proteins in the enteric protozoan parasite Entamoeba histolytica.
    Kumiko Nakada-Tsukui, Natsuki Watanabe, Kumiko Shibata, Ratna Wahyuni, Eri Miyamoto, Tomoyoshi Nozaki.
      Autophagy is one of the bulk degradation systems and is conserved throughout eukaryotes. In the enteric protozoan parasite Entamoeba histolytica, the causative agent of human amebiasis, Atg8 is not exclusively involved in autophagy per se but also in other membrane traffic-related pathways such as phagosome biogenesis. We previously reported that repression of atg8 gene expression by antisense small RNA-mediated transcriptional gene silencing (gs) resulted in growth retardation, delayed endocytosis, and reduced acidification of endosomes and phagosomes. In this study, to better understand the role of Atg8 in phagocytosis and trogocytosis, we conducted a comparative proteomic analysis of phagosomes isolated from wild type and atg8-gs strains. We found that 127 and 107 proteins were detected >1.5-fold less or more abundantly, respectively, in phagosomes isolated from the atg8-gs strain, compared to the control strain. Among 127 proteins whose abundance was reduced in phagosomes from atg8-gs, a panel of proteins related to fatty acid metabolism, phagocytosis, and endoplasmic reticulum (ER) homeostasis was identified. Various lysosomal hydrolases and their receptors also tend to be excluded from phagosomes by atg8-gs, reinforcing the notion that Atg8 is involved in phagosomal acidification and digestion. On the contrary, among 107 proteins whose abundance increased in phagosomes from atg8-gs strain, ribosome-related proteins and metabolite interconversion enzymes are enriched. We further investigated the localization of several representative proteins, including adenylyl cyclase-associated protein and plasma membrane calcium pump, both of which were demonstrated to be recruited to phagosomes and trogosomes via an Atg8-dependent mechanism. Taken together, our study has provided the basis of the phagosome proteome to further elucidate molecular events in the Atg8-dependent regulatory network of phagosome/trogosome biogenesis in E. histolytica.
    Keywords:  Atg8; Entamoeba histolytica; autophagy; endoplasmic reticulum; gene silencing; lysosome; phagosome; proteome
    DOI:  https://doi.org/10.3389/fcimb.2022.961645
  52. NPJ Parkinsons Dis. 2022 Oct 18. 8(1): 135
    Mitophagy and reactive oxygen species interplay in Parkinson's disease.
    Bin Xiao, Joshua Kuruvilla, Eng-King Tan.
      Mitophagy impairment and oxidative stress are cardinal pathological hallmarks in Parkinson's disease (PD), a common age-related neurodegenerative condition. The specific interactions between mitophagy and reactive oxygen species (ROS) have attracted considerable attention even though their exact interplay in PD has not been fully elucidated. We highlight the interactions between ROS and mitophagy, with a focus on the signalling pathways downstream to ROS that triggers mitophagy and draw attention to potential therapeutic compounds that target these pathways in both experimental and clinical models. Identifying a combination of ROS inhibitors and mitophagy activators to provide a physiologic balance in this complex signalling pathways may lead to a more optimal outcome. Deciphering the exact temporal relationship between mitophagy and oxidative stress and their triggers early in the course of neurodegeneration can unravel mechanistic clues that potentially lead to the development of compounds for clinical drug trials focusing on prodromic PD or at-risk individuals.
    DOI:  https://doi.org/10.1038/s41531-022-00402-y
  53. J Cell Mol Med. 2022 Oct 17.
    Larotrectinib induces autophagic cell death through AMPK/mTOR signalling in colon cancer.
    Wencheng Kong, Hangzhang Zhu, Sixing Zheng, Guang Yin, Panpan Yu, Yuqiang Shan, Xinchun Liu, Rongchao Ying, Hong Zhu, Shenglin Ma.
      Larotrectinib (Lar) is a highly selective and potent small-molecule inhibitor used in patients with tropomyosin receptor kinase (TRK) fusion-positive cancers, including colon cancer. However, the underlying molecular mechanisms specifically in patients with colon cancer have not yet been explored. Our data showed that Lar significantly suppressed proliferation and migration of colon cancer cells. In addition, Lar suppressed the epithelial-mesenchymal transition (EMT) process, as evidenced by elevation in E-cadherin (E-cad), and downregulation of vimentin and matrix metalloproteinase (MMP) 2/9 expression. Furthermore, Lar was found to activate autophagic flux, in which Lar increased the ratio between LC3II/LC3I and decreased the expression of p62 in colon cancer cells. More importantly, Lar also increased AMPK phosphorylation and suppressed mTOR phosphorylation in colon cancer cells. However, when we silenced AMPK in colon cancer cells, Lar-induced accumulation of autolysomes as well as Lar-induced suppression of the EMT process were significantly diminished. An in vivo assay also confirmed that tumour volume and weight decreased in Lar-treated mice than in control mice. Taken together, this study suggests that Lar significantly suppresses colon cancer proliferation and migration by activating AMPK/mTOR-mediated autophagic cell death.
    Keywords:  AMPK/mTOR signalling; Larotrectinib; autophagy flux; colon cancer; epithelial-mesenchymal transition
    DOI:  https://doi.org/10.1111/jcmm.17530
  54. Ecotoxicol Environ Saf. 2022 Oct 14. pii: S0147-6513(22)01012-0. [Epub ahead of print]246 114172
    Graphene oxide induced dynamic changes of autophagy-lysosome pathway and cell apoptosis via TFEB dysregulation in F98 cells.
    Danni Dai, Yuming Chen, Qiuyu Wang, Chunlin Wang, Chao Zhang.
      The extensive application of graphene oxide (GO) nanomaterials increases the risk of their release into the environment, thus posing a threat to the human body. Multiple studies indicate that GO could lead to neurotoxicity, while the intricate biological effects of GO in astrocytes remain unclear. The autophagic disorder was considered an important part of the exposure risk of GO in the application of neuromedicine. This study explored the key regulators mediating the autophagic process in rat astroglioma-derived F98 cells caused by GO, especially the dynamic changes in the cellular physiological state over time. We identified transcription factor EB (TFEB), a critical regulator of the autophagy-lysosome pathway (ALP), as a crucial factor in GO-induced autophagy flux blockade and cell apoptosis. Specifically, the prolonged exposure to GO increased the amount of its cellular internalization, which gradually prevented TFEB from entering the nucleus, thereby leading to the subsequent ALP dysfunction and excessive cell apoptosis. Furthermore, STIP1 homology and U-Box containing protein 1 (STUB1), an E3 ubiquitin ligase, was responsible for GO-triggered TFEB dysregulation, and overexpression of STUB1 helped alleviate GO cytotoxicity. Our study highlights that impaired TFEB activity underlies compromised autophagy flux in GO-induced apoptosis and opens up new avenues for the application of GO-based nanotherapeutics with specific autophagy-regulating properties in the central nervous system.
    Keywords:  Apoptosis; Astrocyte; Graphene oxide; Neurobiology; TFEB
    DOI:  https://doi.org/10.1016/j.ecoenv.2022.114172
  55. Front Mol Neurosci. 2022 ;15 1001382
    A minute fraction of α-synuclein in extracellular vesicles may be a major contributor to α-synuclein spreading following autophagy inhibition.
    Hash Brown Taha, Brian Kearney, Gal Bitan.
      
    Keywords:  alpha-synclein; autophagy; extracellular vesicle (EV); p62; post translational modification (PTM); synucleinopathy
    DOI:  https://doi.org/10.3389/fnmol.2022.1001382
  56. Biochemistry. 2022 Oct 20.
    LC3B Binds to the Autophagy Protease ATG4b with High Affinity Using a Bipartite Interface.
    Yinyan Tang, Amber Kay, Ziwen Jiang, Michelle R Arkin.
      Autophagy is a catabolic cellular process in which unwanted proteins and organelles are degraded by lysosomes. It is characterized by the formation of the double-membrane autophagosome decorated with LC3B, a protein that mediates autophagosomal fusion with lysosomes. The cysteine protease ATG4b acts at two stages in the life cycle of LC3B. We set out to characterize the protein-protein interaction between LC3B and ATG4b. Through biochemical and biophysical studies, we show that the ubiquitin-like core of LC3B (residues 1-115; "LC3B-115"), which lacks the C-terminal cleavage site (between residue 120 and 121), binds to full-length ATG4b with a surprisingly tight dissociation constant (KD) in the low nanomolar range; 10-30-fold tighter than that of the substrate pro-LC3B (residues 1-125) or the product LC3B-I (residues 1-120). Consequently, LC3B-115 is a potent inhibitor of the ATG4b-mediated cleavage of pro-LC3B (IC50 = 15 nM). Binding of the LC3B-115 has no effect on the conformation of the active site of ATG4b, as judged by the turnover of a peptide substrate ("substrate-33"), derived from LC3B-I residues 116-120. Conversely, truncations of ATG4b show that binding and proteolysis of LC3B critically depend on the C-terminal tail of ATG4b, whereas proteolysis of the peptide substrate-33 does not require the C-terminal tail of ATG4b. These results support a bipartite model for LC3B-ATG4b binding in which the core of LC3B binds to ATG4b and the C-terminal tail of pro-LC3B organizes the ATG4b active site; additionally, the C-terminal tail of ATG4b contributes at least 1000-fold higher binding affinity to the LC3B-ATG4b interaction and likely wraps around the LC3B-ubiquitin core. PPIs are often described as containing an energetic "hot spot" for binding; in the case of LC3B-ATG4b, however, the substrate-enzyme complex contains multiple, energetically relevant domains that differentially affect binding affinity and catalytic efficiency.
    DOI:  https://doi.org/10.1021/acs.biochem.2c00482
  57. Life Sci Alliance. 2023 Jan;pii: e202201526. [Epub ahead of print]6(1):
    The metabolite-controlled ubiquitin conjugase Ubc8 promotes mitochondrial protein import.
    Saskia Rödl, Fabian den Brave, Markus Räschle, Büsra Kizmaz, Svenja Lenhard, Carina Groh, Hanna Becker, Jannik Zimmermann, Bruce Morgan, Elke Richling, Thomas Becker, Johannes M Herrmann.
      Mitochondria play a key role in cellular energy metabolism. Transitions between glycolytic and respiratory conditions induce considerable adaptations of the cellular proteome. These metabolism-dependent changes are particularly pronounced for the protein composition of mitochondria. Here, we show that the yeast cytosolic ubiquitin conjugase Ubc8 plays a crucial role in the remodeling process when cells transition from respiratory to fermentative conditions. Ubc8 is a conserved and well-studied component of the catabolite control system that is known to regulate the stability of gluconeogenic enzymes. Unexpectedly, we found that Ubc8 also promotes the assembly of the translocase of the outer membrane of mitochondria (TOM) and increases the levels of its cytosol-exposed receptor subunit Tom22. Ubc8 deficiency results in compromised protein import into mitochondria and reduced steady-state levels of mitochondrial proteins. Our observations show that Ubc8, which is controlled by the prevailing metabolic conditions, promotes the switch from glucose synthesis to glucose usage in the cytosol and induces the biogenesis of the mitochondrial TOM machinery to improve mitochondrial protein import during phases of metabolic transition.
    DOI:  https://doi.org/10.26508/lsa.202201526
  58. Biochimie. 2022 Oct 13. pii: S0300-9084(22)00268-1. [Epub ahead of print]
    Autophagy: Dual roles and perspective for clinical treatment of colorectal cancer.
    Yabin Zhang, Haiyan Li, Liang Lv, Kefeng Lu, Huihui Li, Wenli Zhang, Tao Cui.
      Colorectal cancer (CRC) raises concerns to people because of its high recurrence and metastasis rate, diagnosis challenges, and poor prognosis. Various studies have shown the association of altered autophagy with tumorigenesis, tumor-stroma interactions, and resistance to cancer therapy in CRC. Autophagy is a highly conserved cytosolic catabolic process in eukaryotes that plays distinct roles in CRC occurrence and progression. In early tumorigenesis, autophagy may inhibit tumor growth through diverse mechanisms, whereas it exhibits a tumor promoting function in CRC progression. This different functions of autophagy in CRC occurrence and progression make developing therapies targeting autophagy complicated. In this review, we discuss the classification and process of autophagy as well as its dual roles in CRC, functions in the tumor microenvironment, cross-talk with apoptosis, and potential usefulness as a CRC therapeutic target.
    Keywords:  Autophagy; Chemo-/immuno-therapy; Colorectal cancer; Tumor microenvironment; Tumor promoter; Tumor suppressor
    DOI:  https://doi.org/10.1016/j.biochi.2022.10.004
  59. Stem Cells Int. 2022 ;2022 2983862
    Autophagy Regulates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells Induced by Orthodontic Tension.
    Junyi Zheng, Bowen Xu, Kai Yang.
      Tooth movement is the core of orthodontics. Osteogenesis of the tension side under orthodontic force has great significance on tooth movement and stability, which involves complex mechanical and biological signal transduction. However, the mechanism remains unclear. Through in vitro cell studies, we observed the increased expression levels of osteogenesis-related factors and autophagy-related factors during the osteogenic differentiation of mesenchymal stem cells induced by orthodontic force. The change trend of autophagy-related factors and osteogenesis-related factors is similar, which indicates the involvement of autophagy in osteogenesis. In the study of autophagy-related gene ATG7 silenced cells, the expression level of autophagy was significantly inhibited, and the expression level of osteogenesis-related factors also decreased accordingly. Through drug regulation, we observed that the increase of autophagy level could effectively promote osteogenic differentiation, while the decrease of the autophagy level inhibited this process to some extent. Therefore, autophagy plays an important role in the osteogenic differentiation of mesenchymal stem cells induced by orthodontic force, which provides a novel idea useful for orthodontic treatment in promoting periodontal tissue remodeling and accelerating tooth movement.
    DOI:  https://doi.org/10.1155/2022/2983862
  60. Clin Immunol. 2022 Oct 17. pii: S1521-6616(22)00234-0. [Epub ahead of print] 109153
    mTOR signaling: A pivotal player in Treg cell dysfunction in systemic lupus erythematosus.
    Xingyun Zhao, Shifen Wang, Shengjun Wang, Jue Xie, Dawei Cui.
      Systemic lupus erythematosus (SLE) is a typical autoimmune disease characterized by multiorgan involvement and marked variability in clinical presentation. SLE pathogenesis includes regulatory T cell dysfunction and antinuclear antibody production. Mammalian target of rapamycin (mTOR), a serine/threonine kinase in the phosphoinositide 3-kinase (PI3K)-related kinase family, is a therapeutic target for autoimmune diseases such as SLE. Rapamycin, an inhibitor of the mTOR signaling pathway, is a macrolide antibiotic with potent immunosuppressive, antiproliferative and antifibrotic effects. Recently, an increasing number of studies have investigated the role of mTOR in regulatory T (Treg) cells and its impact on SLE pathogenesis. This review aims to systematically summarize the role of the mTOR signaling pathway in SLE pathogenesis, Treg cell dysfunction and SLE treatment.
    Keywords:  Autoimmune disease; Dysfunction; Regulatory T cells; Systemic lupus erythematosus; mTOR
    DOI:  https://doi.org/10.1016/j.clim.2022.109153
  61. Front Aging Neurosci. 2022 ;14 1029440
    Editorial: Mitochondrial and lysosomal dysfunction in neurodegenerative diseases: Molecular mechanisms and therapeutic strategies.
    Chen Xiang, Xiao Yousheng, Zhu Xiaolei, Yang Wenjie, Pu Jiali, Pei Zhong.
      
    Keywords:  lysosomal dysfunction; mitochondrial dysfunction; molecular mechanism; neurodegenerative disease; therapeutic
    DOI:  https://doi.org/10.3389/fnagi.2022.1029440
  62. J Cell Biol. 2023 Jan 02. pii: e202201088. [Epub ahead of print]222(1):
    Liquid-liquid phase separation mediates the formation of herpesvirus assembly compartments.
    Sheng Zhou, Zhifei Fu, Ziwei Zhang, Xing Jia, Guangjun Xu, Long Sun, Fei Sun, Pu Gao, Pingyong Xu, Hongyu Deng.
      Virus assembly, which takes place during the late stage of viral replication, is essential for virus propagation. However, the underlying mechanisms remain poorly understood, especially for viruses with complicated structures. Here, we use correlative light and electron microscopy to examine the formation of cytoplasmic virion assembly compartments (cVACs) during infection by a γ-herpesvirus. These cVACs are membraneless organelles with liquid-like properties. Formation of cVACs during virus infection is mediated by ORF52, an abundant tegument protein. ORF52 undergoes liquid-liquid phase separation (LLPS), which is promoted by both DNA and RNA. Disrupting ORF52 phase separation blocks cVACs formation and virion production. These results demonstrate that phase separation of ORF52 is critical for cVACs formation. Our work defines herpesvirus cVACs as membraneless compartments that are generated through a process of LLPS mediated by a tegument protein and adds to the cellular processes that are facilitated by phase separation.
    DOI:  https://doi.org/10.1083/jcb.202201088
  63. Chemistry. 2022 Oct 20.
    Lysosomal Targeting of β-Cyclodextrin.
    Andrea Mascherpa, Nozomii Ishii, Ayelen Tayagui, Jiang Liu, Matthieu Sollogoub, Antony John Fairbanks.
      β-Cyclodextrin (β-CD) and derivatives are approved therapeutics in >30 clinical settings. β-CDs have also shown promise as therapeutics for treatment of some lysosomal storage disorders, such as Niemann-Pick disease type C, and other disease states which involve metabolite accumulation in the lysosome. In these cases, β-CD activity relies on transport to the lysosome, wherein it can bind hydrophobic substrate and effect extraction. The post-translational attachment of N-glycans terminated in mannose-6-phosphate (M6P) residues is the predominant method by which lysosomal enzymes are targeted to the lysosome. In this work we covalently attach a synthetic biantennary bis-M6P-terminated N-glycan to β-CD and study the effect of the added glycans in a mammalian cell line. The formation of a host guest complex with a Cy5 fluorophore allows study of both cellular internalisation and transport to the lysosome by fluorescence microscopy. Results indicate that the rates of both internalisation and lysosomal transport are increased by the attachment of M6P-glycans to β-CD, indicating that M6P-glycan conjugation may improve the therapeutic effectiveness of β-CD for the treatment of disorders involving hydrophobic metabolite accumulation in the lysosome.
    Keywords:  Fluorescent probes; carbohydrates; cyclodextrins; lysosome; mannose-6-phosphate
    DOI:  https://doi.org/10.1002/chem.202203252
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