bims-auttor 2024-04-21 papers

bims-auttor

Biomed News

on Autophagy and mTOR

Issue of 2024‒04‒21
forty-six papers selected by
Viktor Korolchuk, Newcastle University

Defective Lamtor5 Leads to Autoimmunity by Deregulating v-ATPase and Lysosomal Acidification.
Autophagy cooperates with PDGFRA to support oncogenic growth signaling.
TXNIP deficiency attenuates renal fibrosis by modulating mTORC1/TFEB-mediated autophagy in diabetic kidney disease.
The impact of nanomaterials on autophagy across health and disease conditions.
All Roads Lead to Rome: Comparing Nanoparticle- and Small Molecule-Driven Cell Autophagy.
Toxic gain-of-function mechanisms in C9orf72 ALS-FTD neurons drive autophagy and lysosome dysfunction.
Selective autophagy of macromolecular complexes: what does it take to be taken?
Energy deprivation-induced autophagy and aggrephagy: insights from yeast and mammals.
Autophagy gene expression in skeletal muscle of older individuals is associated with physical performance, muscle volume and mitochondrial function in the study of muscle, mobility and aging (SOMMA).
Yeast Crf1p is an activator with different roles in regulation of target genes.
Lysosomal Degradation Targets Mutant Calreticulin and the Thrombopoietin Receptor in Myeloproliferative Neoplasms.
Fish ubiquitin-specific protease 8 (USP8) inhibits IFN production through autophagy-lysosomal dependent degradation of IRF7.
A mechanism that transduces lysosomal damage signals to stress granule formation for cell survival.
Morphological and biochemical characteristics associated with autophagy in gastrointestinal diseases.
Impaired reprogramming of the autophagy flux in maturing dendritic cells from crohn disease patients with core autophagy gene-related polymorphisms.
ROS-responsive nano-medicine for navigating autophagy to enhance targeted therapy of inflammatory bowel disease.
Variant-specific effects of GBA1 mutations on dopaminergic neuron proteostasis.
Perilipin 2 inhibits replication of hepatitis B virus deoxyribonucleic acid by regulating autophagy under high-fat conditions.
Selective degradation of PL2L60 by metabolic stresses‑induced autophagy suppresses multi‑cancer growth.
miR-584-5p / Ykt6 - mediated autophagy - lysosome - exosome pathway as a critical route affecting the toxic effects of lead on HK-2 cells.
Heme oxygenase activates calcium release from the endoplasmic reticulum of bovine mammary epithelial cells to promote TFEB entry into the nucleus to reduce the intracellular load of Mycoplasma bovis.
Urolithin a inhibits breast cancer progression via activating TFEB-mediated mitophagy in tumor macrophages.
Next questions in autophagy.
Autophagy-dependent lysosomal calcium overload and the ATP5B-regulated lysosomes-mitochondria calcium transmission induce liver insulin resistance under perfluorooctane sulfonate exposure.
PI3K/AKT/mTOR signaling pathway: an important driver and therapeutic target in triple-negative breast cancer.
FoxG1 as a Potential Therapeutic Target for Alzheimer's Disease: Modulating NLRP3 Inflammasome via AMPK/mTOR Autophagy Pathway.
OPN silencing reduces hypoxic pulmonary hypertension via PI3K-AKT-induced protective autophagy.
ANKFY1 bridges ATG2A-mediated lipid transfer from endosomes to phagophores.
Altered lipid homeostasis is associated with cerebellar neurodegeneration in SNX14 deficiency.
Accumulation of APP C-terminal fragments causes endolysosomal dysfunction through the dysregulation of late endosome to lysosome-ER contact sites.
A phosphodiesterase 4 (PDE4) inhibitor, amlexanox, reduces neuroinflammation and neuronal death after pilocarpine-induced seizure.
Targeting PNPO to suppress tumor growth via inhibiting autophagic flux and to reverse paclitaxel resistance in ovarian cancer.
Targeting the undruggables-the power of protein degraders.
Amino acid transporter SLC7A5 regulates cell proliferation and secretary cell differentiation and distribution in the mouse intestine.
Inhibition of autophagosome-lysosome fusion contributes to TDCIPP-induced Aβ1-42 production in N2a-APPswe cells.
IL-33 Accelerates Chronic Atrophic Gastritis through AMPK-ULK1 Axis Mediated Autolysosomal Degradation of GKN1.
The emerging role of CARM1 in cancer.
Atorvastatin reduces calcification in valve interstitial cells via the NF-κB signalling pathway by promoting Atg5-mediated autophagy.
Onco-Circuit Addiction and Onco-Nutrient mTORC1 Signaling Vulnerability in a Model of Aggressive T Cell Malignancy.
ULK1-dependent phosphorylation of PKM2 antagonizes O-GlcNAcylation and regulates the Warburg effect in breast cancer.
Stasimon/Tmem41b is required for cell proliferation and adult mouse survival.
ALKBH5 suppresses autophagic flux via N6-methyladenosine demethylation of ZKSCAN3 mRNA in acute pancreatitis.
Rapamycin improves the survival of epilepsy model cells by blocking phosphorylation of mTOR base on computer simulations and cellular experiments.
Cdk8/CDK19 promotes mitochondrial fission through Drp1 phosphorylation and can phenotypically suppress pink1 deficiency in Drosophila.
AMPK restricts HHV-6A replication by inhibiting glycolysis and mTOR signaling.
RNF31 alleviates liver steatosis by promoting p53/BNIP3-related mitophagy in hepatocytes.

Adv Sci (Weinh). 2024 Apr 19. e2400446

Defective Lamtor5 Leads to Autoimmunity by Deregulating v-ATPase and Lysosomal Acidification.

Wei Zhang, Zhou Sha, Yunzhe Tang, Cuiyuan Jin, Wenhua Gao, Changmai Chen, Lang Yu, Nianyin Lv, Shijia Liu, Feng Xu, Dandan Wang, Liyun Shi.

  Despite accumulating evidence linking defective lysosome function with autoimmune diseases, how the catabolic machinery is regulated to maintain immune homeostasis remains unknown. Late endosomal/lysosomal adaptor, MAPK and mTOR activator 5 (Lamtor5) is a subunit of the Ragulator mediating mechanistic target of rapamycin complex 1 (mTORC1) activation in response to amino acids, but its action mode and physiological role are still unclear. Here it is demonstrated that Lamtor5 level is markedly decreased in peripheral blood mononuclear cells (PBMCs) of patients with systemic lupus erythematosus (SLE). In parallel, the mice with myeloid Lamtor5 ablation developed SLE-like manifestation. Impaired lysosomal function and aberrant activation of mTORC1 are evidenced in Lamtor5 deficient macrophages and PBMCs of SLE patients, accompanied by blunted autolysosomal pathway and undesirable inflammatory responses. Mechanistically, it is shown that Lamtor5 is physically associated with ATP6V1A, an essential subunit of vacuolar H+-ATPase (v-ATPase), and promoted the V0/V1 holoenzyme assembly to facilitate lysosome acidification. The binding of Lamtor5 to v-ATPase affected the lysosomal tethering of Rag GTPase and weakened its interaction with mTORC1 for activation. Overall, Lamtor5 is identified as a critical factor for immune homeostasis by intergrading v-ATPase activity, lysosome function, and mTOR pathway. The findings provide a potential therapeutic target for SLE and/or other autoimmune diseases.

Keywords:  autoimmunity; lamtor5; lysosome; v‐ATPase

DOI:  https://doi.org/10.1002/advs.202400446
Autophagy. 2024 Apr 18. 1-2

Autophagy cooperates with PDGFRA to support oncogenic growth signaling.

Joanne E Simpson, Noor Gammoh.

  Macroautophagy (referred to as autophagy hereafter) is a highly conserved catabolic process which sequesters intracellular substrates for lysosomal degradation. Autophagy-related proteins have been shown to be involved in various aspects of tumor development by engaging with multiple cellular substrates. We recently uncovered a novel role for autophagy in regulating the signaling and levels of PDGFRA, a receptor tyrosine kinase amplified in several cancers. We discovered that PDGFRA can be targeted to autophagic degradation by binding the autophagy cargo receptor SQSTM1. Surprisingly, PDGFRA-mediated signaling is perturbed in the absence of autophagy despite enhanced receptor levels. We show that this is due to disrupted trafficking of the receptor to late endosomes where signaling activity persists. Conversely, prolonged autophagy inhibition results in a transcriptional downregulation of Pdgfra as a result of inhibited signaling activity demonstrating that short- and long-term autophagy inhibition have opposing effects on receptor levels. We further investigated the consequence of PDGFRA regulation by autophagy using a mouse model for gliomagenesis where we observed a disruption in PDGFA-driven tumor formation when autophagy is inhibited. Activation of downstream signaling through Pten mutation overrides the need for autophagy during tumor development suggesting a genotype-specific role for autophagy during tumorigenesis. Altogether, our findings provide a novel mechanism through which autophagy can support tumor growth.

Keywords:  Cancer; PDGFRA; endocytosis; glioblastoma; receptor tyrosine kinases; signaling

DOI:  https://doi.org/10.1080/15548627.2024.2338572
Ren Fail. 2024 Dec;46(1): 2338933

TXNIP deficiency attenuates renal fibrosis by modulating mTORC1/TFEB-mediated autophagy in diabetic kidney disease.

Yunxia Du, Ming Wu, Shan Song, Yawei Bian, Yonghong Shi.

  Thioredoxin-interacting protein (TXNIP) is an important regulatory protein for thioredoxin (TRX) that elicits the generation of reactive oxygen species (ROS) by inhibiting the redox function of TRX. Abundant evidence suggests that TXNIP is involved in the fibrotic process of diabetic kidney disease (DKD). However, the potential mechanism of TXNIP in DKD is not yet well understood. In this study, we found that TXNIP knockout suppressed renal fibrosis and activation of mammalian target of rapamycin complex 1 (mTORC1) and restored transcription factor EB (TFEB) and autophagy activation in diabetic kidneys. Simultaneously, TXNIP interference inhibited epithelial-to-mesenchymal transformation (EMT), collagen I and fibronectin expression, and mTORC1 activation, increased TFEB nuclear translocation, and promoted autophagy restoration in HK-2 cells exposed to high glucose (HG). Rapamycin, an inhibitor of mTORC1, increased TFEB nuclear translocation and autophagy in HK-2 cells under HG conditions. Moreover, the TFEB activators, curcumin analog C1 and trehalose, effectively restored HG-induced autophagy, and abrogated HG-induced EMT and collagen I and fibronectin expression in HK-2 cells. Taken together, these findings suggest that TXNIP deficiency ameliorates renal fibrosis by regulating mTORC1/TFEB-mediated autophagy in diabetic kidney diseases.

Keywords:  Autophagy; TFEB; TXNIP; diabetic kidney disease; mTORC1

DOI:  https://doi.org/10.1080/0886022X.2024.2338933
Cell Mol Life Sci. 2024 Apr 17. 81(1): 184

The impact of nanomaterials on autophagy across health and disease conditions.

Ida Florance, Marco Cordani, Parya Pashootan, Mohammad Amin Moosavi, Ali Zarrabi, Natarajan Chandrasekaran.

  Autophagy, a catabolic process integral to cellular homeostasis, is constitutively active under physiological and stress conditions. The role of autophagy as a cellular defense response becomes particularly evident upon exposure to nanomaterials (NMs), especially environmental nanoparticles (NPs) and nanoplastics (nPs). This has positioned autophagy modulation at the forefront of nanotechnology-based therapeutic interventions. While NMs can exploit autophagy to enhance therapeutic outcomes, they can also trigger it as a pro-survival response against NP-induced toxicity. Conversely, a heightened autophagy response may also lead to regulated cell death (RCD), in particular autophagic cell death, upon NP exposure. Thus, the relationship between NMs and autophagy exhibits a dual nature with therapeutic and environmental interventions. Recognizing and decoding these intricate patterns are essential for pioneering next-generation autophagy-regulating NMs. This review delves into the present-day therapeutic potential of autophagy-modulating NMs, shedding light on their status in clinical trials, intervention of autophagy in the therapeutic applications of NMs, discusses the potency of autophagy for application as early indicator of NM toxicity.

Keywords:  Autophagic flux; Autophagy blockade; Environmental toxicity; Nanoparticles; Nanoplastics; Regulated cell death

DOI:  https://doi.org/10.1007/s00018-024-05199-y
Small. 2024 Apr 15. e2310966

All Roads Lead to Rome: Comparing Nanoparticle- and Small Molecule-Driven Cell Autophagy.

Xiaofei Zhou, Iliana E Medina-Ramirez, Gaoxing Su, Yin Liu, Bing Yan.

  Autophagy, vital for removing cellular waste, is triggered differently by small molecules and nanoparticles. Small molecules, like rapamycin, non-selectively activate autophagy by inhibiting the mTOR pathway, which is essential for cell regulation. This can clear damaged components but may cause cytotoxicity with prolonged use. Nanoparticles, however, induce autophagy, often causing oxidative stress, through broader cellular interactions and can lead to a targeted form known as "xenophagy." Their impact varies with their properties but can be harnessed therapeutically. In this review, the autophagy induced by nanoparticles is explored and small molecules across four dimensions: the mechanisms behind autophagy induction, the outcomes of such induction, the toxicological effects on cellular autophagy, and the therapeutic potential of employing autophagy triggered by nanoparticles or small molecules. Although small molecules and nanoparticles each induce autophagy through different pathways and lead to diverse effects, both represent invaluable tools in cell biology, nanomedicine, and drug discovery, offering unique insights and therapeutic opportunities.

Keywords:  autophagy regulators; compounds; nanoparticles; signaling pathways; targeted therapy

DOI:  https://doi.org/10.1002/smll.202310966
Autophagy. 2024 Apr 18. 1-3

Toxic gain-of-function mechanisms in C9orf72 ALS-FTD neurons drive autophagy and lysosome dysfunction.

Jimmy Beckers, Philip Van Damme.

  Hexanucleotide repeat expansions in the C9orf72 gene are the primary genetic cause for both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two related neurodegenerative diseases. Significant advances in the elucidation of the disease mechanisms responsible for C9orf72 ALS-FTD have revealed both a toxic gain-of-function and a loss-of-function mechanism as possible underlying disease cause. As the differential contribution of both gain and loss of function in C9orf72 ALS-FTD pathogenesis remains debated, we investigated disease mechanisms in motor neurons derived from both authentic human patient C9orf72 ALS-FTD iPSCs as well as a C9orf72 knockout iPSC line. We found that patient neurons presented with less motile and enlarged lysosomes, a decrease in autophagic flux and an increase in SQSTM1/p62 puncta and insoluble TARDBP/TDP-43 species. Importantly, we found that C9orf72 knockout barely has any influence on these phenotypes and mainly results in impaired endosomal maturation. Together, our data suggest that toxic gain-of-function, rather than loss-of-function, mechanisms in C9orf72 ALS-FTD impair the autophagy-lysosome system in neurons.

Keywords:  Autophagy; C9orf72; amyotrophic lateral sclerosis; endosome; frontotemporal dementia; lysosome

DOI:  https://doi.org/10.1080/15548627.2024.2340415
J Mol Biol. 2024 Apr 16. pii: S0022-2836(24)00169-4. [Epub ahead of print] 168574

Selective autophagy of macromolecular complexes: what does it take to be taken?

Javier Lizarrondo, Florian Wilfling.

  Proteins are known to perform an astonishing array of functions thanks to their ability to cooperate and modulate each other's properties. Inside cells, proteins can assemble into large multi-subunit complexes to carry out complex cellular functions. The correct assembly and maintenance of the functional state of macromolecular protein complexes is crucial for human health. Failure to do so leads to loss of function and potential accumulation of harmful materials, which is associated with a variety of human diseases such as neurodegeneration and cancer. Autophagy engulfs cytosolic material in autophagosomes, and therefore is best suited to eliminate intact macromolecular complexes without disassembling them, which could interfere with de novo assembly. In this review, we discuss the role of autophagy in the selective degradation of macromolecular complexes. We highlight the current state of knowledge for different macromolecular complexes and their selective autophagic degradation. We emphasize the gaps in our understanding of what it takes for these large macromolecular complexes to be degraded and point to future work that may shed light on the regulation of the selective degradation of macromolecular complexes by autophagy.

Keywords:  LLPS; Selective; autophagy; cargo-recognition; phase separation; protein complexes; proteostasis

DOI:  https://doi.org/10.1016/j.jmb.2024.168574
J Zhejiang Univ Sci B. 2024 Apr 07. 1-5

Energy deprivation-induced autophagy and aggrephagy: insights from yeast and mammals.

Siyu Fan, Yingcong Chen, Weijing Yao, Cong Yi.

  Autophagy plays a crucial role in maintaining cellular homeostasis in response to various stimuli. Compared to research on nutrient deprivation-induced autophagy, the understanding of the molecular mechanisms and physiological/pathological significance of autophagy triggered by energy deprivation remains limited. A primary focus of our lab is to elucidate how cells sense energy deprivation and initiate autophagy. Using the model organisms Saccharomyces cerevisiae and mammalian cells, we found that cellular reactive oxygen species (ROS), DNA damage sensor Mec1, and mitochondrial aerobic respiration play essential roles in the autophagy induced by energy deprivation. This review aims to provide a concise overview of these research findings.

Keywords:  Autophagy; Chaperonin-containing TCP-1, subunit 2 (CCT2); Glucose starvation; Solid aggrephagy

DOI:  https://doi.org/10.1631/jzus.B2300884
Aging Cell. 2024 Apr 16. e14118

Autophagy gene expression in skeletal muscle of older individuals is associated with physical performance, muscle volume and mitochondrial function in the study of muscle, mobility and aging (SOMMA).

Paul M Coen, Zhiguang Huo, Gregory J Tranah, Haley N Barnes, Xiping Zhang, Christopher A Wolff, Kevin Wu, Peggy M Cawthon, Russell T Hepple, Frederico G S Toledo, Daniel S Evans, Olaya Santiago-Fernández, Ana Maria Cuervo, Stephen B Kritchevsky, Anne B Newman, Steven R Cummings, Karyn A Esser.

  Autophagy is essential for proteostasis, energetic balance, and cell defense and is a key pathway in aging. Identifying associations between autophagy gene expression patterns in skeletal muscle and physical performance outcomes would further our knowledge of mechanisms related with proteostasis and healthy aging. Muscle biopsies were obtained from participants in the Study of Muscle, Mobility, and Aging (SOMMA). For 575 participants, RNA was sequenced and expression of 281 genes related to autophagy regulation, mitophagy, and mTOR/upstream pathways was determined. Associations between gene expression and outcomes including mitochondrial respiration in muscle fiber bundles (MAX OXPHOS), physical performance (VO2 peak, 400 m walking speed, and leg power), and thigh muscle volume, were determined using negative binomial regression models. For autophagy, key transcriptional regulators including TFE3 and NFKB-related genes (RELA, RELB, and NFKB1) were negatively associated with outcomes. On the contrary, regulators of oxidative metabolism that also promote overall autophagy, mitophagy, and pexophagy (PPARGC1A, PPARA, and EPAS1) were positively associated with multiple outcomes. In line with this, several mitophagy, fusion, and fission-related genes (NIPSNAP2, DNM1L, and OPA1) were also positively associated with outcomes. For mTOR pathway and related genes, expression of WDR59 and WDR24, both subunits of GATOR2 complex (an indirect inhibitor of mTORC1), and PRKAG3, which is a regulatory subunit of AMPK, were negatively correlated with multiple outcomes. Our study identifies autophagy and selective autophagy such as mitophagy gene expression patterns in human skeletal muscle related to physical performance, muscle volume, and mitochondrial function in older persons which may lead to target identification to preserve mobility and independence.

Keywords:  aging; autophagy; gene expression; mTor; mitochondria; mobility; oxidative metabolism

DOI:  https://doi.org/10.1111/acel.14118
Yeast. 2024 Apr 19.

Yeast Crf1p is an activator with different roles in regulation of target genes.

Sanjay Kumar, Muneera Mashkoor, Priya Balamurugan, Anne Grove.

  Under stress conditions, ribosome biogenesis is downregulated. This process requires that expression of ribosomal RNA, ribosomal protein, and ribosome biogenesis genes be controlled in a coordinated fashion. The mechanistic Target of Rapamycin Complex 1 (mTORC1) participates in sensing unfavorable conditions to effect the requisite change in gene expression. In Saccharomyces cerevisiae, downregulation of ribosomal protein genes involves dissociation of the activator Ifh1p in a process that depends on Utp22p, a protein that also functions in pre-rRNA processing. Ifh1p has a paralog, Crf1p, which was implicated in communicating mTORC1 inhibition and hence was perceived as a repressor. We focus here on two ribosomal biogenesis genes, encoding Utp22p and the high mobility group protein Hmo1p, both of which are required for communication of mTORC1 inhibition to target genes. Crf1p functions as an activator on these genes as evidenced by reduced mRNA abundance and RNA polymerase II occupancy in a crf1Δ strain. Inhibition of mTORC1 has distinct effects on expression of HMO1 and UTP22; for example, on UTP22, but not on HMO1, the presence of Crf1p promotes the stable depletion of Ifh1p. Our data suggest that Crf1p functions as a weak activator, and that it may be required to prevent re-binding of Ifh1p to some gene promoters after mTORC1 inhibition in situations when Ifh1p is available. We propose that the inclusion of genes encoding proteins required for mTORC1-mediated downregulation of ribosomal protein genes in the same regulatory circuit as the ribosomal protein genes serves to optimize transcriptional responses during mTORC1 inhibition.

Keywords:  Hmo1p; Ifh1p; Sfp1p; Utp22p; gene regulation; mTORC1

DOI:  https://doi.org/10.1002/yea.3939
Blood Adv. 2024 Apr 19. pii: bloodadvances.2023011432. [Epub ahead of print]

Lysosomal Degradation Targets Mutant Calreticulin and the Thrombopoietin Receptor in Myeloproliferative Neoplasms.

Amanpreet Kaur, Arunkumar Venkatesan, Malathi Kandarpa, Moshe Talpaz, Malini Raghavan.

Somatic mutants of calreticulin (CRT) drive myeloproliferative neoplasms (MPNs) via binding to the thrombopoietin receptor (MPL) and aberrant activation of the JAK/STAT pathway. Compared with healthy donors, platelets from MPN patients with CRT mutations display low cell surface MPL. Additionally, co-expression of MPL with an MPN-linked CRT mutant (CRTDel52) reduces cell surface MPL, suggesting that CRTDel52 may induce MPL degradation. We show that lysosomal degradation is relevant to the turnover of CRTDel52 and MPL. Furthermore, CRTDel52 increases the lysosomal localization and degradation of MPL. Mammalian target of rapamycin (mTOR) inhibitors reduce cellular CRTDel52, MPL and secreted CRTDel52 levels, and impair CRTDel52-mediated cell proliferation. mTOR inhibition also reduces colony formation and differentiation of CD34+ cells from MPN patients but not healthy donors. Together, these findings indicate low surface MPL as a biomarker of mutant CRT-mediated MPN and induced degradation of CRTDel52 and MPL as an avenue for therapeutic intervention.

DOI: https://doi.org/10.1182/bloodadvances.2023011432
Dev Comp Immunol. 2024 Apr 16. pii: S0145-305X(24)00053-3. [Epub ahead of print] 105181

Fish ubiquitin-specific protease 8 (USP8) inhibits IFN production through autophagy-lysosomal dependent degradation of IRF7.

Chu-Jing Zhou, Can Zhang, Long-Feng Lu, Shun Li.

Interferon regulatory factor 7 (IRF7) is considered the master regulator of virus-induced interferon (IFN) production. However, to avoid an autoimmune response, the expression of IRF7 must be tightly controlled. In this study, we report that zebrafish ubiquitin-specific protease 8 (USP8) promotes IRF7 degradation through an autophagy-lysosome-dependent pathway to inhibit IFN production. First, zebrafish usp8 is induced upon spring viremia of carp virus (SVCV) infection and polyinosinic/polycytidylic acid (poly I:C) stimulation. Second, overexpression of USP8 suppresses SVCV or poly I:C-mediated IFN expression. Mechanistically, USP8 interacts with IRF7 and promotes its degradation via an autophagy-lysosome-dependent pathway. Finally, USP8 significantly suppresses cellular antiviral responses and enhances SVCV proliferation. In summary, our discoveries offer a perspective on the role of zebrafish USP8 and provide additional understanding of the regulation of IRF7 in host antiviral immune response.

DOI: https://doi.org/10.1016/j.dci.2024.105181
bioRxiv. 2024 Apr 02. pii: 2024.03.29.587368. [Epub ahead of print]

A mechanism that transduces lysosomal damage signals to stress granule formation for cell survival.

Jacob Duran, Suttinee Poolsup, Lee Allers, Monica Rosas Lemus, Qiuying Cheng, Jing Pu, Michelle Salemi, Brett Phinney, Jingyue Jia.

Lysosomal damage poses a significant threat to cell survival. Our previous work has reported that lysosomal damage induces stress granule (SG) formation. However, the importance of SG formation in determining cell fate and the precise mechanisms through which lysosomal damage triggers SG formation remains unclear. Here, we show that SG formation is initiated via a novel calcium-dependent pathway and plays a protective role in promoting cell survival in response to lysosomal damage. Mechanistically, we demonstrate that during lysosomal damage, ALIX, a calcium-activated protein, transduces lysosomal damage signals by sensing calcium leakage to induce SG formation by controlling the phosphorylation of eIF2α. ALIX modulates eIF2α phosphorylation by regulating the association between PKR and its activator PACT, with galectin-3 exerting a negative effect on this process. We also found this regulatory event of SG formation occur on damaged lysosomes. Collectively, these investigations reveal novel insights into the precise regulation of SG formation triggered by lysosomal damage, and shed light on the interaction between damaged lysosomes and SGs. Importantly, SG formation is significant for promoting cell survival in the physiological context of lysosomal damage inflicted by SARS-CoV-2 ORF3a, adenovirus infection, Malaria hemozoin, proteopathic tau as well as environmental hazard silica.

DOI: https://doi.org/10.1101/2024.03.29.587368
World J Gastroenterol. 2024 Mar 21. 30(11): 1524-1532

Morphological and biochemical characteristics associated with autophagy in gastrointestinal diseases.

Yi-Fan Chang, Jia-Jing Li, Tao Liu, Chong-Qing Wei, Li-Wei Ma, Vladimir N Nikolenko, Wei-Long Chang.

  Autophagy is a cellular catabolic process characterized by the formation of double-membrane autophagosomes. Transmission electron microscopy is the most rigorous method to clearly visualize autophagic engulfment and degradation. A large number of studies have shown that autophagy is closely related to the digestion, secretion, and regeneration of gastrointestinal (GI) cells. However, the role of autophagy in GI diseases remains controversial. This article focuses on the morphological and biochemical characteristics of autophagy in GI diseases, in order to provide new ideas for their diagnosis and treatment.

Keywords:  Autophagy; Biochemical characteristics; Gastrointestinal diseases; Morphological study; Subcellular structure; Transmission electron microscopy

DOI:  https://doi.org/10.3748/wjg.v30.i11.1524
Autophagy. 2024 Apr 18. 1-17

Impaired reprogramming of the autophagy flux in maturing dendritic cells from crohn disease patients with core autophagy gene-related polymorphisms.

Gaëlle Quiniou, Leslie Andromaque, Rémi Duclaux-Loras, Océane Dinet, Ornella Cervantes, Mallorie Verdet, Camille Meunier, Gilles Boschetti, Christophe Viret, Stéphane Nancey, Mathias Faure, Aurore Rozières.

  Crohn disease (CD) is an inflammatory bowel disease whose pathogenesis involves inappropriate immune responses toward gut microbiota on genetically predisposed backgrounds. Notably, CD is associated with single-nucleotide polymorphisms affecting several genes involved in macroautophagy/autophagy, the catabolic process that ensures the degradation and recycling of cytosolic components and microorganisms. In a clinical translation perspective, monitoring the autophagic activity of CD patients will require some knowledge on the intrinsic functional status of autophagy. Here, we focused on monocyte-derived dendritic cells (DCs) to characterize the intrinsic quantitative features of the autophagy flux. Starting with DCs from healthy donors, we documented a reprogramming of the steady state flux during the transition from the immature to mature status: both the autophagosome pool size and the flux were diminished at the mature stage while the autophagosome turnover remained stable. At the cohort level, DCs from CD patients were comparable to control in term of autophagy flux reprogramming capacity. However, the homozygous presence of ATG16L1 rs2241880 A>G (T300A) and ULK1 rs12303764 (G/T) polymorphisms abolished the capacity of CD patient DCs to reprogram their autophagy flux during maturation. This effect was not seen in the case of CD patients heterozygous for these polymorphisms, revealing a gene dose dependency effect. In contrast, the NOD2 rs2066844 c.2104C>T (R702W) polymorphism did not alter the flux reprogramming capacity of DCs. The data, opening new clinical translation perspectives, indicate that polymorphisms affecting autophagy-related genes can differentially influence the capacity of DCs to reprogram their steady state autophagy flux when exposed to proinflammatory challenges.Abbreviation: BAFA1: bafilomycin A1, CD: Crohn disease; DC: dendritic cells; HD: healthy donor; iDCs: immature DCs; IL: interleukin; J: autophagosome flux; LPS: lipopolysaccharide; MHC: major histocompatibility complex; nA: autophagosome pool size; SNPs: single-nucleotide polymorphisms; PCA: principal component analysis; TLR: toll like receptor; τ: transition time; TNF: tumor necrosis factor.

Keywords:  Autophagy flux; Crohn disease; dendritic cells; inflammation; single nucleotide polymorphism

DOI:  https://doi.org/10.1080/15548627.2024.2338574
Int J Pharm. 2024 Apr 12. pii: S0378-5173(24)00351-X. [Epub ahead of print] 124117

ROS-responsive nano-medicine for navigating autophagy to enhance targeted therapy of inflammatory bowel disease.

You Chen, Juewen Feng, Yang Chen, Chuanhe Xia, Min Yao, Wenxing Ding, Xiang Li, Xiuzhi Fu, Shulei Zheng, Yin Ma, Jiafeng Zou, Minbo Lan, Feng Gao.

  Inflammatory bowel disease (IBD) is a chronic gastrointestinal disorder characterized by immune dysregulation and intestinal inflammation. Rapamycin (Ra), an mTORC1 pathway inhibitor, has shown promise for autophagy induction in IBD therapy but is associated with off-target effects and toxicity. To address these issues, we developed an oral liposome responsive to reactive oxygen species (ROS) using lipids and amphiphilic materials. We combined ketone thiol (TK) for ROS responsive and hyaluronic acid (HA) with high affinity for CD44 receptors to prepare rapamycin-loaded nanoparticle (Ra@TH). Owing to its ROS responsive characteristic, Ra@TH can achieve inflammatory colonic targeting. Additionally, Ra@TH can induce autophagy by inhibiting the mTORC1 pathway, leading to the clearance of damaged organelles, pathogenic microorganisms and oxidative stress products. Simultaneously, it also collaboratively inhibits the NF-κB pathway suppressed by the removal of ROS resulting from TK cleavage, thereby mediating the expression of inflammatory factors. Furthermore, Ra@TH enhances the expression of typical tight junction proteins, synergistically restoring intestinal barrier function. Our research not only expands the understanding of autophagy in IBD treatment but also introduces a promising therapeutic approach for IBD patients.

Keywords:  Colonic targeting; Inflammatory bowel disease; Navigating autophagy; ROS-responsive; Rapamycin

DOI:  https://doi.org/10.1016/j.ijpharm.2024.124117
J Neurochem. 2024 Apr 20.

Variant-specific effects of GBA1 mutations on dopaminergic neuron proteostasis.

G Onal, G Yalçın-Çakmaklı, C E Özçelik, I Boussaad, U Ö Ş Şeker, Hugo J R Fernandes, H Demir, R Krüger, B Elibol, S Dökmeci, M M Salman.

  Glucocerebrosidase 1 (GBA1) mutations are the most important genetic risk factors for Parkinson's disease (PD). Clinically, mild (e.g., p.N370S) and severe (e.g., p.L444P and p.D409H) GBA1 mutations have different PD phenotypes, with differences in age at disease onset, progression, and the severity of motor and non-motor symptoms. We hypothesize that GBA1 mutations cause the accumulation of α-synuclein by affecting the cross-talk between cellular protein degradation mechanisms, leading to neurodegeneration. Accordingly, we tested whether mild and severe GBA1 mutations differentially affect the degradation of α-synuclein via the ubiquitin-proteasome system (UPS), chaperone-mediated autophagy (CMA), and macroautophagy and differentially cause accumulation and/or release of α-synuclein. Our results demonstrate that endoplasmic reticulum (ER) stress and total ubiquitination rates were significantly increased in cells with severe GBA1 mutations. CMA was found to be defective in induced pluripotent stem cell (iPSC)-derived dopaminergic neurons with mild GBA1 mutations, but not in those with severe GBA1 mutations. When examining macroautophagy, we observed reduced formation of autophagosomes in cells with the N370S and D409H GBA1 mutations and impairments in autophagosome-lysosome fusion in cells with the L444P GBA1 mutation. Accordingly, severe GBA1 mutations were found to trigger the accumulation and release of oligomeric α-synuclein in iPSC-derived dopaminergic neurons, primarily as a result of increased ER stress and defective macroautophagy, while mild GBA1 mutations affected CMA, which is mainly responsible for the degradation of the monomeric form of α-synuclein. Overall, our findings provide new insight into the molecular basis of the clinical variability in PD associated with different GBA1 mutations.

Keywords:  GBA1; Gaucher disease; Parkinson's disease; iPSC‐derived neurons; macroautophagy; α‐Synuclein

DOI:  https://doi.org/10.1111/jnc.16114
World J Virol. 2024 Mar 25. 13(1): 90384

Perilipin 2 inhibits replication of hepatitis B virus deoxyribonucleic acid by regulating autophagy under high-fat conditions.

M Victoria Delpino, Jorge Quarleri.

  Hepatitis B virus (HBV) infection poses a global health concern without a definitive cure; however, antiviral medications can effectively suppress viral replication. This study delves into the intricate interplay between lipid metabolism and HBV replication, implicating molecular mechanisms such as the stearoyl coenzyme A desaturase 1 autophagy pathway, SAC1-like phosphatidylinositol phosphatase, and galectin-9 mediated selective autophagy of viral core proteins in regulating HBV replication. Within lipid droplets, perilipin 2 (PLIN2) emerges as a pivotal guardian, with its overexpression protecting against autophagy and downregulation stimulating triglyceride catabolism through the autophagy pathway. This editorial discusses the correlation between hepatic steatosis and HBV replication, emphasizing the role of PLIN2 in this process. The study underscores the multifaceted roles of lipid metabolism, autophagy, and perilipins in HBV replication, shedding light on potential therapeutic avenues.

Keywords:  Autophagy; Hepatitis B virus; Liver; Non-alcoholic fatty liver disease; Perilipin 2

DOI:  https://doi.org/10.5501/wjv.v13.i1.90384
Oncol Rep. 2024 Mar;pii: 41. [Epub ahead of print]51(3):

Selective degradation of PL2L60 by metabolic stresses‑induced autophagy suppresses multi‑cancer growth.

Lei Sun, Fu Hui, Gao-Yan Tang, Hai-Lian Shen, Xue-Lei Cao, Jian-Xin Gao, Lin-Feng Li.

  It has been reported that PL2L60 proteins, a product of PIWIL2 gene which might be activated by an intragenic promoter, could mediate a common pathway specifically for tumorigenesis. In the present study, it was further identified by using western blot assay that the PL2L60 proteins could be degraded in cancer cells through a mechanism of selective autophagy in response to oxidative stress. The PL2L60 was downregulated in various types of cancer cells under the hypoxic condition independently of HIF‑1α, resulting in apoptosis of cancer cells. Inhibition of autophagy by small interfering RNA targeting of either Beclin‑1 (BECN1) or Atg5 resulted in restoration of PL2L60 expression in hypoxic cancer cell. The hypoxic degradation of PL2L60 was also blocked by the attenuation of the autophagosome membrane protein Atg8/microtubule‑associated protein 1 light chain 3 (LC3) or autophagy cargo protein p62 expression. Surprisingly, Immunofluorescence analysis demonstrated that LC3 could be directly bound to PL2L60 and was required for the transport of PL2L60 from the nucleus to the cytoplasm for lysosomal flux under basal or activated autophagy in cancer cells. Moreover, flow cytometric analysis displayed that knocking down of PL2L60 mRNA but not PIWIL2 mRNA effectively inhibited cancer cell proliferation and promoted apoptosis of cancer cells. The similar results were obtained from in vivo tumorigenic experiment, in which PL2L60 downregulation in necroptosis areas was confirmed by immunohistochemistry. These results suggested that various cancer could be suppressed by promoting autophagy. The present study revealed a key role of autophagic degradation of PL2L60 in hypoxia‑induced cancer cell death, which could be used as a novel therapeutic target of cancer.

Keywords:  PL2L60; autophagic cell death; autophagy; cancer; hypoxia

DOI:  https://doi.org/10.3892/or.2024.8700
Ecotoxicol Environ Saf. 2024 Apr 17. pii: S0147-6513(24)00398-1. [Epub ahead of print]276 116322

miR-584-5p / Ykt6 - mediated autophagy - lysosome - exosome pathway as a critical route affecting the toxic effects of lead on HK-2 cells.

Yiren Xiong, Zuqing Hu, Di Ouyang, Meilin Tang, Jiayi He, Shanshan He, Renyi Liu, Zhenjie Gao, Ying Chen, Dalin Hu.

  Lead is a widespread environmental pollutant with serious adverse effects on human health, but the mechanism underlying its toxicity remains elusive. This study aimed to investigate the role of miR-584-5p / Ykt6 axis in the toxic effect of lead on HK-2 cells and the related mechanism. Our data suggested that lead exposure caused significant cytotoxicity, DNA and chromosome damage to HK-2 cells. Mechanistically, lead exposure down-regulated miR-584-5p and up-regulated Ykt6 expression, consequently, autophagosomal number and autophagic flux increased, lysosomal number and activity decreased, exosomal secretion increased. Interestingly, when miR-584-5p level was enhanced with mimic, autophagosomal number and autophagic flux decreased, lysosomal number and activity increased, ultimately, exosomal secretion was down-regulated, which resulted in significant aggravated toxic effects of lead. Further, directly blocking exosomal secretion with inhibitor GW4869 also resulted in exacerbated toxic effects of lead. Herein, we conclude that miR-584-5p / Ykt6 - mediated autophagy - lysosome - exosome pathway may be a critical route affecting the toxic effects of lead on HK-2 cells. We provide a novel insight into the mechanism underlying the toxicity of lead on human cells.

Keywords:  Autophagy; Exosomes; Lead; Lysosomes; MiR-584–5p /Ykt6 axis; Toxic effects

DOI:  https://doi.org/10.1016/j.ecoenv.2024.116322
Microbiol Res. 2024 Apr 16. pii: S0944-5013(24)00128-9. [Epub ahead of print]284 127727

Heme oxygenase activates calcium release from the endoplasmic reticulum of bovine mammary epithelial cells to promote TFEB entry into the nucleus to reduce the intracellular load of Mycoplasma bovis.

Maolin Xu, Zimeng Zhu, Siyu Meng, Haoxia Li, Anrui Wang, Herman W Barkema, Eduardo R Cobo, John P Kastelic, Muhammad Asfandyar Khan, Jian Gao, Bo Han.

  Heme oxygenase HO-1 (HMOX) regulates cellular inflammation and apoptosis, but its role in regulation of autophagy in Mycoplasma bovis infection is unknown. The objective was to determine how the HO-1/CO- Protein kinase RNA-like endoplasmic reticulum kinase (PERK)-Ca2+- transcription factor EB (TFEB) signaling axis induces autophagy and regulates clearance of M. bovis by bovine mammary epithelial cells (bMECs). M. bovis inhibited autophagy and lysosomal biogenesis in bMECs and suppressed HO-1 protein and expression of related proteins, namely nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associated protein 1 (keap1). Activation of HO-1 and its production of carbon monoxide (CO) were required for induction of autophagy and clearance of intracellular M. bovis. Furthermore, when HO-1 was deficient, CO sustained cellular autophagy. HO-1 activation increased intracellular calcium (Ca2+) and cytosolic localization activity of TFEB via PERK. Knockdown of PERK or chelation of intracellular Ca2+ inhibited HO-1-induced M. bovis autophagy and clearance. M. bovis infection affected nuclear localization of lysosomal TFEB in the MiT/TFE transcription factor subfamily, whereas activation of HO-1 mediated dephosphorylation and intranuclear localization of TFEB, promoting autophagy, lysosomal biogenesis and autophagic clearance of M. bovis. Nuclear translocation of TFEB in HO-1 was critical to induce M. bovis transport and survival of infected bMECs. Furthermore, the HO-1/CO-PERK-Ca2+-TFEB signaling axis induced autophagy and M. bovis clearance, providing a viable approach to treat persistent M. bovis infections.

Keywords:  Autophagy; Ca(2+); HO-1; Mycoplasma bovis; TFEB; bMECs

DOI:  https://doi.org/10.1016/j.micres.2024.127727
J Adv Res. 2024 Apr 12. pii: S2090-1232(24)00153-X. [Epub ahead of print]

Urolithin a inhibits breast cancer progression via activating TFEB-mediated mitophagy in tumor macrophages.

Bowen Zheng, Yuying Wang, Baian Zhou, Fengyuan Qian, Diya Liu, Danrong Ye, Xiqian Zhou, Lin Fang.

  INTRODUCTION: Urolithin A (UA) is a naturally occurring compound that is converted from ellagitannin-like precursors in pomegranates and nuts by intestinal flora. Previous studies have found that UA exerts tumor-suppressive effects through antitumor cell proliferation and promotion of memory T-cell expansion, but its role in tumor-associated macrophages remains unknown.OBJECTIVES: Our study aims to reveal how UA affects tumor macrophages and tumor cells to inhibit breast cancer progression.
METHODS: Observe the effect of UA treatment on breast cancer progression though in vivo and in vitro experiments. Western blot and PCR assays were performed to discover that UA affects tumor macrophage autophagy and inflammation. Co-ip and Molecular docking were used to explore specific molecular mechanisms.
RESULTS: We observed that UA treatment could simultaneously inhibit harmful inflammatory factors, especially for InterleuKin-6 (IL-6) and tumor necrosis factor α (TNF-α), in both breast cancer cells and tumor-associated macrophages, thereby improving the tumor microenvironment and delaying tumor progression. Mechanistically, UA induced the key regulator of autophagy, transcription factor EB (TFEB), into the nucleus in a partially mTOR-dependent manner and inhibited the ubiquitination degradation of TFEB, which facilitated the clearance of damaged mitochondria via the mitophagy-lysosomal pathway in macrophages under tumor supernatant stress, and reduced the deleterious inflammatory factors induced by the release of nucleic acid from damaged mitochondria. Molecular docking and experimental studies suggest that UA block the recognition of TFEB by 1433 and induce TFEB nuclear localization. Notably, UA treatment demonstrated inhibitory effects on tumor progression in multiple breast cancer models.
CONCLUSION: Our study elucidated the anti-breast cancer effect of UA from the perspective of tumor-associated macrophages. Specifically, TFEB is a crucial downstream target in macrophages.

Keywords:  Breast cancer; Mitophagy; TFEB; Tumor-associated macrophages; Urolithin A

DOI:  https://doi.org/10.1016/j.jare.2024.04.010
Nat Cell Biol. 2024 Apr 19.

Next questions in autophagy.

Ana Maria Cuervo, Zvulun Elazar, Chantell Evans, Liang Ge, Malene Hansen, Marja Jäättelä, Jin Rui Amos Liang, Ben Loos, Noboru Mizushima, Anna Katharina Simon, Sharon Tooze, Tamotsu Yoshimori, Shuhei Nakamura.

DOI: https://doi.org/10.1038/s41556-024-01404-z
Ecotoxicol Environ Saf. 2024 Apr 15. pii: S0147-6513(24)00394-4. [Epub ahead of print]276 116318

Autophagy-dependent lysosomal calcium overload and the ATP5B-regulated lysosomes-mitochondria calcium transmission induce liver insulin resistance under perfluorooctane sulfonate exposure.

Jixun Li, Yu Ma, Tianming Qiu, Jianyu Wang, Jingyuan Zhang, Xiance Sun, Liping Jiang, Qiujuan Li, Xiaofeng Yao.

  Perfluorooctane sulfonate (PFOS), an officially listed persistent organic pollutant, is a widely distributed perfluoroalkyl substance. Epidemiological studies have shown that PFOS is intimately linked to the occurrence of insulin resistance (IR). However, the detailed mechanism remains obscure. In previous studies, we found that mitochondrial calcium overload was concerned with hepatic IR induced by PFOS. In this study, we found that PFOS exposure noticeably raised lysosomal calcium in L-02 hepatocytes from 0.5 h. In the PFOS-cultured L-02 cells, inhibiting autophagy alleviated lysosomal calcium overload. Inhibition of mitochondrial calcium uptake aggravated the accumulation of lysosomal calcium, while inhibition of lysosomal calcium outflowing reversed PFOS-induced mitochondrial calcium overload and IR. Transient receptor potential mucolipin 1 (TRPML1), the calcium output channel of lysosomes, interacted with voltage-dependent anion channel 1 (VDAC1), the calcium intake channel of mitochondria, in the PFOS-cultured cells. Moreover, we found that ATP synthase F1 subunit beta (ATP5B) interacted with TRPML1 and VDAC1 in the L-02 cells and the liver of mice under PFOS exposure. Inhibiting ATP5B expression or restraining the ATP5B on the plasma membrane reduced the interplay between TRPML1 and VDAC1, reversed the mitochondrial calcium overload and deteriorated the lysosomal calcium accumulation in the PFOS-cultured cells. Our research unveils the molecular regulation of the calcium crosstalk between lysosomes and mitochondria, and explains PFOS-induced IR in the context of activated autophagy.

Keywords:  ATP synthase F(1) subunit beta; Insulin resistance; Lysosomal calcium; Mitochondrial calcium; Perfluorooctane sulfonate

DOI:  https://doi.org/10.1016/j.ecoenv.2024.116318
Breast Cancer. 2024 Apr 17.

PI3K/AKT/mTOR signaling pathway: an important driver and therapeutic target in triple-negative breast cancer.

Huan-Ping Zhang, Rui-Yuan Jiang, Jia-Yu Zhu, Ke-Na Sun, Yuan Huang, Huan-Huan Zhou, Ya-Bing Zheng, Xiao-Jia Wang.

  Triple-negative breast cancer (TNBC) is a highly heterogeneous tumor lacking estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression. It has higher aggressiveness and metastasis than other subtypes, with limited effective therapeutic strategies, leading to a poor prognosis. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) signaling pathway is prevalently over-activated in human cancers and contributes to breast cancer (BC) growth, survival, proliferation, and angiogenesis, which could be an interesting therapeutic target. This review summarizes the PI3K/AKT/mTOR signaling pathway activation mechanism in TNBC and discusses the relationship between its activation and various TNBC subtypes. We also report the latest clinical studies on kinase inhibitors related to this pathway for treating TNBC. Our review discusses the issues that need to be addressed in the clinical application of these inhibitors.

Keywords:  AKT; PI3K; PTEN; Targeted therapy; Triple-negative breast cancer

DOI:  https://doi.org/10.1007/s12282-024-01567-5
Cell Mol Neurobiol. 2024 Apr 17. 44(1): 35

FoxG1 as a Potential Therapeutic Target for Alzheimer's Disease: Modulating NLRP3 Inflammasome via AMPK/mTOR Autophagy Pathway.

Qi Yun, Si-Fei Ma, Wei-Ning Zhang, Meng Gu, Jia Wang.

  An increasing body of research suggests that promoting microglial autophagy hinders the neuroinflammation initiated though the NLRP3 inflammasome activation in Alzheimer's disease (AD). The function of FoxG1, a crucial transcription factor involved in cell survival by regulating mitochondrial function, remains unknown during the AD process and neuroinflammation occurs. In the present study, we firstly found that Aβ peptides induced AD-like neuroinflammation upregulation and downregulated the level of autophagy. Following low-dose Aβ25-35 stimulation, FoxG1 expression and autophagy exhibited a gradual increase. Nevertheless, with high-concentration Aβ25-35 treatment, progressive decrease in FoxG1 expression and autophagy levels as the concentration of Aβ25-35 escalated. In addition, FoxG1 has a positive effect on cell viability and autophagy in the nervous system. In parallel with the Aβ25-35 stimulation, we employed siRNA to decrease the expression of FoxG1 in N2A cells. A substantial reduction in autophagy level (Beclin1, LC3II, SQSTM1/P62) and a notable growth in inflammatory response (NLRP3, TNF-α, and IL-6) were observed. In addition, we found FoxG1 overexpression owned the effect on the activation of AMPK/mTOR autophagy pathway and siRNA-FoxG1 successfully abolished this effect. Lastly, FoxG1 suppressed the NLRP3 inflammasome and enhanced the cognitive function in AD-like mouse model induced by Aβ25-35. Confirmed by cellular and animal experiments, FoxG1 suppressed NLRP3-mediated neuroinflammation, which was strongly linked to autophagy regulated by AMPK/mTOR. Taken together, FoxG1 may be a critical node in the pathologic progression of AD and has the potential to serve as therapeutic target.

Keywords:  AMPK/mTOR; Alzheimer’s disease; Autophagy; FoxG1; NLRP3; β-amyloid

DOI:  https://doi.org/10.1007/s10571-024-01467-4
Sci Rep. 2024 04 15. 14(1): 8670

OPN silencing reduces hypoxic pulmonary hypertension via PI3K-AKT-induced protective autophagy.

Rui Zhou, Ran Li, Qi Ding, Yuwei Zhang, Hui Yang, Ying Han, Chuanchuan Liu, Jie Liu, Shenglan Wang.

Hypoxic pulmonary hypertension (HPH) is a pulmonary vascular disease primarily characterized by progressive pulmonary vascular remodeling in a hypoxic environment, posing a significant clinical challenge. Leveraging data from the Gene Expression Omnibus (GEO) and human autophagy-specific databases, osteopontin (OPN) emerged as a differentially expressed gene, upregulated in cardiovascular diseases such as pulmonary arterial hypertension (PAH). Despite this association, the precise mechanism by which OPN regulates autophagy in HPH remains unclear, prompting the focus of this study. Through biosignature analysis, we observed significant alterations in the PI3K-AKT signaling pathway in PAH-associated autophagy. Subsequently, we utilized an animal model of OPNfl/fl-TAGLN-Cre mice and PASMCs with OPN shRNA to validate these findings. Our results revealed right ventricular hypertrophy and elevated mean pulmonary arterial pressure (mPAP) in hypoxic pulmonary hypertension model mice. Notably, these effects were attenuated in conditionally deleted OPN-knockout mice or OPN-silenced hypoxic PASMCs. Furthermore, hypoxic PASMCs with OPN shRNA exhibited increased autophagy compared to those in hypoxia alone. Consistent findings from in vivo and in vitro experiments indicated that OPN inhibition during hypoxia reduced PI3K expression while increasing LC3B and Beclin1 expression. Similarly, PASMCs exposed to hypoxia and PI3K inhibitors had higher expression levels of LC3B and Beclin1 and suppressed AKT expression. Based on these findings, our study suggests that OPNfl/fl-TAGLN-Cre effectively alleviates HPH, potentially through OPN-mediated inhibition of autophagy, thereby promoting PASMCs proliferation via the PI3K-AKT signaling pathway. Consequently, OPN emerges as a novel therapeutic target for HPH.

DOI: https://doi.org/10.1038/s41598-024-59367-y
Cell Discov. 2024 Apr 16. 10(1): 43

ANKFY1 bridges ATG2A-mediated lipid transfer from endosomes to phagophores.

Bin Wei, Yuhui Fu, Xiuzhi Li, Fang Chen, Yiqing Zhang, Hanmo Chen, Mindan Tong, Linsen Li, Yi Pan, Shen Zhang, She Chen, Xiaoxia Liu, Qing Zhong.

Macroautophagy is a process that cells engulf cytosolic materials by autophagosomes and deliver them to lysosomes for degradation. The biogenesis of autophagosomes requires ATG2 as a lipid transfer protein to transport lipids from existing membranes to phagophores. It is generally believed that endoplasmic reticulum is the main source for lipid supply of the forming autophagosomes; whether ATG2 can transfer lipids from other organelles to phagophores remains elusive. In this study, we identified a new ATG2A-binding protein, ANKFY1. Depletion of this endosome-localized protein led to the impaired autophagosome growth and the reduced autophagy flux, which largely phenocopied ATG2A/B depletion. A pool of ANKFY1 co-localized with ATG2A between endosomes and phagophores and depletion of UVRAG, ANKFY1 or ATG2A/B led to reduction of PI3P distribution on phagophores. Purified recombinant ANKFY1 bound to PI3P on membrane through its FYVE domain and enhanced ATG2A-mediated lipid transfer between PI3P-containing liposomes. Therefore, we propose that ANKFY1 recruits ATG2A to PI3P-enriched endosomes and promotes ATG2A-mediated lipid transfer from endosomes to phagophores. This finding implicates a new lipid source for ATG2A-mediated phagophore expansion, where endosomes donate PI3P and other lipids to phagophores via lipid transfer.

DOI: https://doi.org/10.1038/s41421-024-00659-y
JCI Insight. 2024 Apr 16. pii: e168594. [Epub ahead of print]

Altered lipid homeostasis is associated with cerebellar neurodegeneration in SNX14 deficiency.

Yijing Zhou, Vanessa B Sanchez, Peining Xu, Thomas Roule, Marco Flores-Mendez, Brianna Ciesielski, Donna Yoo, Hiab Teshome, Teresa Jimenez, Shibo Liu, Mike Henne, Tim O'Brien, Ye He, Clementina Mesaros, Naiara Akizu.

  Dysregulated lipid homeostasis is emerging as a potential cause of neurodegenerative disorders. However, evidence of errors in lipid homeostasis as a pathogenic mechanism of neurodegeneration remains limited. Here, we show that cerebellar neurodegeneration caused by Sorting Nexin 14 (SNX14) deficiency is associated with lipid homeostasis defects. Recent studies indicate that SNX14 is an inter-organelle lipid transfer protein that regulates lipid transport, lipid droplet (LD) biogenesis, and fatty acid desaturation, suggesting that human SNX14 deficiency belongs to an expanding class of cerebellar neurodegenerative disorders caused by altered cellular lipid homeostasis. To test this hypothesis, we generated a mouse model that recapitulates human SNX14 deficiency at a genetic and phenotypic level. We demonstrate that cerebellar Purkinje cells (PCs) are selectively vulnerable to SNX14 deficiency while forebrain regions preserve their neuronal content. Ultrastructure and lipidomic studies reveal widespread lipid storage and metabolism defects in SNX14 deficient mice. However, pre-degenerating SNX14 deficient cerebella show a unique accumulation of acylcarnitines and depletion of triglycerides. Furthermore, defects in LD content and telolysosome enlargement in pre-degenerating PCs, suggest lipotoxicity as a pathogenic mechanism of SNX14 deficiency. Our work shows a selective cerebellar vulnerability to altered lipid homeostasis and provides a mouse model for future therapeutic studies.

Keywords:  Lysosomes; Monogenic diseases; Neurodegeneration; Neuroscience

DOI:  https://doi.org/10.1172/jci.insight.168594
Dev Cell. 2024 Apr 12. pii: S1534-5807(24)00199-0. [Epub ahead of print]

Accumulation of APP C-terminal fragments causes endolysosomal dysfunction through the dysregulation of late endosome to lysosome-ER contact sites.

Marine Bretou, Ragna Sannerud, Abril Escamilla-Ayala, Tom Leroy, Céline Vrancx, Zoë P Van Acker, Anika Perdok, Wendy Vermeire, Inge Vorsters, Sophie Van Keymolen, Michelle Maxson, Benjamin Pavie, Keimpe Wierda, Eeva-Liisa Eskelinen, Wim Annaert.

  Neuronal endosomal and lysosomal abnormalities are among the early changes observed in Alzheimer's disease (AD) before plaques appear. However, it is unclear whether distinct endolysosomal defects are temporally organized and how altered γ-secretase function or amyloid precursor protein (APP) metabolism contribute to these changes. Inhibiting γ-secretase chronically, in mouse embryonic fibroblast and hippocampal neurons, led to a gradual endolysosomal collapse initiated by decreased lysosomal calcium and increased cholesterol, causing downstream defects in endosomal recycling and maturation. This endolysosomal demise is γ-secretase dependent, requires membrane-tethered APP cytoplasmic domains, and is rescued by APP depletion. APP C-terminal fragments (CTFs) localized to late endosome/lysosome-endoplasmic reticulum contacts; an excess of APP-CTFs herein reduced lysosomal Ca2+ refilling from the endoplasmic reticulum, promoting cholesterol accretion. Tonic regulation by APP-CTFs provides a mechanistic explanation for their cellular toxicity: failure to timely degrade APP-CTFs sustains downstream signaling, instigating lysosomal dyshomeostasis, as observed in prodromal AD. This is the opposite of substrates such as Notch, which require intramembrane proteolysis to initiate signaling.

Keywords:  APP proteolysis; APP-CTF; endolysosomal homeostasis; late endosome/lysosome-endoplasmic reticulum contact sites; lysosomal Ca(2+); presenilins; primary hippocampal neurons; γ-secretase; γ-secretase inhibitor

DOI:  https://doi.org/10.1016/j.devcel.2024.03.030
Neurotherapeutics. 2024 Apr 16. pii: S1878-7479(24)00043-6. [Epub ahead of print] e00357

A phosphodiesterase 4 (PDE4) inhibitor, amlexanox, reduces neuroinflammation and neuronal death after pilocarpine-induced seizure.

Hyun Wook Yang, A Ra Kho, Song Hee Lee, Beom Seok Kang, Min Kyu Park, Chang Jun Lee, Se Wan Park, Seo Young Woo, Dong Yeon Kim, Hyun Ho Jung, Bo Young Choi, Won Il Yang, Hong Ki Song, Hui Chul Choi, Jin Kyu Park, Sang Won Suh.

  Epilepsy, a complex neurological disorder, is characterized by recurrent seizures caused by aberrant electrical activity in the brain. Central to this study is the role of lysosomal dysfunction in epilepsy, which can lead to the accumulation of toxic substrates and impaired autophagy in neurons. Our focus is on phosphodiesterase-4 (PDE4), an enzyme that plays a crucial role in regulating intracellular cyclic adenosine monophosphate (cAMP) levels by converting it into adenosine monophosphate (AMP). In pathological states, including epilepsy, increased PDE4 activity contributes to a decrease in cAMP levels, which may exacerbate neuroinflammatory responses. We hypothesized that amlexanox, an anti-inflammatory drug and non-selective PDE4 inhibitor, could offer neuroprotection by addressing lysosomal dysfunction and mitigating neuroinflammation, ultimately preventing neuronal death in epileptic conditions. Our research utilized a pilocarpine-induced epilepsy animal model to investigate amlexanox's potential benefits. Administered intraperitoneally at a dose of 100 mg/kg daily following the onset of a seizure, we monitored its effects on lysosomal function, inflammation, neuronal death, and cognitive performance in the brain. Tissue samples from various brain regions were collected at predetermined intervals for a comprehensive analysis. The study's results were significant. Amlexanox effectively improved lysosomal function, which we attribute to the modulation of zinc's influx into the lysosomes, subsequently enhancing autophagic processes and decreasing the release of inflammatory factors. Notably, this led to the attenuation of neuronal death in the hippocampal region. Additionally, cognitive function, assessed through the modified neurological severity score (mNSS) and the Barnes maze test, showed substantial improvements after treatment with amlexanox. These promising outcomes indicate that amlexanox has potential as a therapeutic agent in the treatment of epilepsy and related brain disorders. Its ability to combat lysosomal dysfunction and neuroinflammation positions it as a potential neuroprotective intervention. While these findings are encouraging, further research and clinical trials are essential to fully explore and validate the therapeutic efficacy of amlexanox in epilepsy management.

Keywords:  Autophagy; Epilepsy; Lysosome; Neuro-inflammation; Phosphodiesterase4; cAMP

DOI:  https://doi.org/10.1016/j.neurot.2024.e00357
Apoptosis. 2024 Apr 13.

Targeting PNPO to suppress tumor growth via inhibiting autophagic flux and to reverse paclitaxel resistance in ovarian cancer.

Xin Li, Wencai Guan, Huiqiang Liu, Jia Yuan, Fanchen Wang, Bin Guan, Junyu Chen, Qi Lu, Guoxiong Xu, Lingyun Zhang.

  Our previous study showed that pyridoxine 5'-phosphate oxidase (PNPO) is a tissue biomarker of ovarian cancer (OC) and has a prognostic implication but detailed mechanisms remain unclear. The current study focused on PNPO-regulated lysosome/autophagy-mediated cellular processes and the potential role of PNPO in chemoresistance. We found that PNPO was overexpressed in OC cells and was a prognostic factor in OC patients. PNPO significantly promoted cell proliferation via the regulation of cyclin B1 and phosphorylated CDK1 and shortened the G2M phase in a cell cycle. Overexpressed PNPO enhanced the biogenesis and perinuclear distribution of lysosomes, promoting the degradation of autophagosomes and boosting the autophagic flux. Further, an autolysosome marker LAMP2 was upregulated in OC cells. Silencing LAMP2 suppressed cell growth and induced cell apoptosis. LAMP2-siRNA blocked PNPO action in OC cells, indicating that the function of PNPO on cellular processes was mediated by LAMP2. These data suggest the existence of the PNPO-LAMP2 axis. Moreover, silencing PNPO suppressed xenographic tumor formation. Chloroquine counteracted the promotion effect of PNPO on autophagic flux and inhibited OC cell survival, facilitating the inhibitory effect of PNPO-shRNA on tumor growth in vivo. Finally, PNPO was overexpressed in paclitaxel-resistant OC cells. PNPO-siRNA enhanced paclitaxel sensitivity in vitro and in vivo. In conclusion, PNPO has a regulatory effect on lysosomal biogenesis that in turn promotes autophagic flux, leading to OC cell proliferation, and tumor formation, and is a paclitaxel-resistant factor. These data imply a potential application by targeting PNPO to suppress tumor growth and reverse PTX resistance in OC.

Keywords:  Autophagy; Chemoresistance; Lysosome; Pyridox(am)ine-5'-phosphate oxidase; Reversal; Tumorigenesis

DOI:  https://doi.org/10.1007/s10495-024-01956-3
Sci Bull (Beijing). 2024 Mar 29. pii: S2095-9273(24)00212-3. [Epub ahead of print]

Targeting the undruggables-the power of protein degraders.

Chao Zhang, Yongbo Liu, Guangchen Li, Zhouli Yang, Chi Han, Xiuyun Sun, Chunquan Sheng, Ke Ding, Yu Rao.

  Undruggable targets typically refer to a class of therapeutic targets that are difficult to target through conventional methods or have not yet been targeted, but are of great clinical significance. According to statistics, over 80% of disease-related pathogenic proteins cannot be targeted by current conventional treatment methods. In recent years, with the advancement of basic research and new technologies, the development of various new technologies and mechanisms has brought new perspectives to overcome challenging drug targets. Among them, targeted protein degradation technology is a breakthrough drug development strategy for challenging drug targets. This technology can specifically identify target proteins and directly degrade pathogenic target proteins by utilizing the inherent protein degradation pathways within cells. This new form of drug development includes various types such as proteolysis targeting chimera (PROTAC), molecular glue, lysosome-targeting Chimaera (LYTAC), autophagosome-tethering compound (ATTEC), autophagy-targeting chimera (AUTAC), autophagy-targeting chimera (AUTOTAC), degrader-antibody conjugate (DAC). This article systematically summarizes the application of targeted protein degradation technology in the development of degraders for challenging drug targets. Finally, the article looks forward to the future development direction and application prospects of targeted protein degradation technology.

Keywords:  DAC; LYTAC; Molecule glue; PROTAC; Targeted protein degradation; Undruggables

DOI:  https://doi.org/10.1016/j.scib.2024.03.056
Int J Biol Sci. 2024 ;20(6): 2187-2201

Amino acid transporter SLC7A5 regulates cell proliferation and secretary cell differentiation and distribution in the mouse intestine.

Lingyu Bao, Liezhen Fu, Yijun Su, Zuojia Chen, Zhaoyi Peng, Lulu Sun, Frank J Gonzalez, Chuan Wu, Hongen Zhang, Bingyin Shi, Yun-Bo Shi.

  The intestine is critical for not only processing nutrients but also protecting the organism from the environment. These functions are mainly carried out by the epithelium, which is constantly being self-renewed. Many genes and pathways can influence intestinal epithelial cell proliferation. Among them is mTORC1, whose activation increases cell proliferation. Here, we report the first intestinal epithelial cell (IEC)-specific knockout (ΔIEC) of an amino acid transporter capable of activating mTORC1. We show that the transporter, SLC7A5, is highly expressed in mouse intestinal crypt and Slc7a5ΔIEC reduces mTORC1 signaling. Surprisingly, adult Slc7a5ΔIEC intestinal crypts have increased cell proliferation but reduced mature Paneth cells. Goblet cells, the other major secretory cell type in the small intestine, are increased in the crypts but reduced in the villi. Analyses with scRNA-seq and electron microscopy have revealed dedifferentiation of Paneth cells in Slc7a5ΔIEC mice, leading to markedly reduced secretory granules with little effect on Paneth cell number. Thus, SLC7A5 likely regulates secretory cell differentiation to affect stem cell niche and indirectly regulate cell proliferation.

Keywords:  amino acid transporter; intestine; mTORC1 signaling pathway; organ homeostasis; stem cell

DOI:  https://doi.org/10.7150/ijbs.94297
Heliyon. 2024 Apr 30. 10(8): e26832

Inhibition of autophagosome-lysosome fusion contributes to TDCIPP-induced Aβ1-42 production in N2a-APPswe cells.

Chunli Zou, Tingting Yang, Xinfeng Huang, Xiaohu Ren, Chen Yang, Benhong Xu, Jianjun Liu.

  Alzheimer's disease is the most common form of dementia and is characterized by cognitive impairment. The disruption of autophagosome-lysosome function has been linked to the pathogenesis of Alzheimer's disease. Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) is a widely used organophosphorus flame retardant that has the potential to cause neuronal damage. We found that TDCIPP significantly increased the expression of β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1), presenilin-1 (PS1) and Aβ42. Proteomic studies with TMT labeling revealed changes in the profiles of N2a-APPswe cells after exposure to TDCIPP. Proteomic and bioinformatics analyses revealed that lysosomal proteins were dysregulated in N2a-APPswe cells after treatment with TDCIPP. The LC3, P62, CTSD, and LAMP1 levels were increased after TDCIPP exposure, and dysregulated protein expression was validated by Western blotting. The exposure to TDCIPP led to the accumulation of autophagosomes, and this phenomenon was enhanced in the presence of chloroquine (CQ). Our results revealed for the first time that TDCIPP could be a potential environmental risk factor for AD development. The inhibition of autophagosome-lysosome fusion may have a significant impact on the generation of Aβ1-42 in response to TDCIPP.

Keywords:  Alzheimer's disease; Autophagy; Aβ42; TDCIPP

DOI:  https://doi.org/10.1016/j.heliyon.2024.e26832
Int J Biol Sci. 2024 ;20(6): 2323-2338

IL-33 Accelerates Chronic Atrophic Gastritis through AMPK-ULK1 Axis Mediated Autolysosomal Degradation of GKN1.

Kewei Liu, Hongxia Huang, Mengyuan Xiong, Qiaojiao Wang, Xiantao Chen, Yinqiong Feng, Hang Ma, Wanqun Chen, Xuegang Li, Xiaoli Ye.

  Chronic atrophic gastritis (CAG) is a complex disease characterized by atrophy and inflammation in gastric mucosal tissue, especially with high expression of interleukins. However, the interaction and mechanisms between interleukins and gastric mucosal epithelial cells in CAG remain largely elusive. Here, we elucidate that IL-33 stands out as the predominant inflammatory factor in CAG, and its expression is induced by H. pylori and MNNG through the ROS-STAT3 signaling pathway. Furthermore, our findings reveal that the IL-33/ST2 axis is intricately involved in the progression of CAG. Utilizing phosphoproteomics mass spectrometry, we demonstrate that IL-33 enhances autophagy in gastric epithelial cells through the phosphorylation of AMPK-ULK1 axis. Notably, inhibiting autophagy alleviates CAG severity, while augmentation of autophagy exacerbates the disease. Additionally, ROS scavenging emerges as a promising strategy to ameliorate CAG by reducing IL-33 expression and inhibiting autophagy. Intriguingly, IL-33 stimulation promotes GKN1 degradation through the autolysosomal pathway. Clinically, the combined measurement of IL-33 and GKN1 in serum shows potential as diagnostic markers. Our findings unveil an IL-33-AMPK-ULK1 regulatory mechanism governing GKN1 protein stability in CAG, presenting potential therapeutic targets for its treatment.

Keywords:  AMPK; Autophagy; Chronic Atrophic Gastritis.; GKN1; IL-33; ULK1

DOI:  https://doi.org/10.7150/ijbs.93573
Cell Oncol (Dordr). 2024 Apr 15.

The emerging role of CARM1 in cancer.

Zizhuo Xie, Yuan Tian, Xiaohan Guo, Na Xie.

  Coactivator-associated arginine methyltransferase 1 (CARM1), pivotal for catalyzing arginine methylation of histone and non-histone proteins, plays a crucial role in developing various cancers. CARM1 was initially recognized as a transcriptional coregulator by orchestrating chromatin remodeling, transcription regulation, mRNA splicing and stability. This diverse functionality contributes to the recruitment of transcription factors that foster malignancies. Going beyond its established involvement in transcriptional control, CARM1-mediated methylation influences a spectrum of biological processes, including the cell cycle, metabolism, autophagy, redox homeostasis, and inflammation. By manipulating these physiological functions, CARM1 becomes essential in critical processes such as tumorigenesis, metastasis, and therapeutic resistance. Consequently, it emerges as a viable target for therapeutic intervention and a possible biomarker for medication response in specific cancer types. This review provides a comprehensive exploration of the various physiological functions of CARM1 in the context of cancer. Furthermore, we discuss potential CARM1-targeting pharmaceutical interventions for cancer therapy.

Keywords:  Arginine methylation; Biomarker; CARM1; Therapeutic target; Tumorigenesis

DOI:  https://doi.org/10.1007/s13402-024-00943-9
Eur J Histochem. 2024 Apr 12. 68(2):

Atorvastatin reduces calcification in valve interstitial cells via the NF-κB signalling pathway by promoting Atg5-mediated autophagy.

Menghui Chen, Su Liu.

Aortic valve calcification (AVC) is a common cardiovascular disease and a risk factor for sudden death. However, the potential mechanisms and effective therapeutic drugs need to be explored. Atorvastatin is a statin that can effectively prevent cardiovascular events by lowering cholesterol levels. However, whether atorvastatin can inhibit AVC by reducing low-density lipoprotein (LDL) and its possible mechanism of action require further exploration. In the current study, we constructed an in vitro AVC model by inducing calcification of the valve interstitial cells. We found that atorvastatin significantly inhibited osteogenic differentiation, reduced the deposition of calcium nodules in valve interstitial cells, and enhanced autophagy in calcified valve interstitial cells, manifested by increased expression levels of the autophagy proteins Atg5 and LC3B-II/I and the formation of smooth autophagic flow. Atorvastatin inhibited the NF-κB signalling pathway and the expression of inflammatory factors mediated by NF-κB in calcified valve interstitial cells. The activation of the NF-κB signalling pathway led to the reversal of atorvastatin's effect on enhancing autophagy and alleviating valve interstitial cell calcification. In conclusion, atorvastatin inhibited the NF-κB signalling pathway by upregulating autophagy, thereby alleviating valve interstitial cell calcification, which was conducive to improving AVC.

DOI: https://doi.org/10.4081/ejh.2024.3983
bioRxiv. 2024 Apr 04. pii: 2024.04.03.587917. [Epub ahead of print]

Onco-Circuit Addiction and Onco-Nutrient mTORC1 Signaling Vulnerability in a Model of Aggressive T Cell Malignancy.

Xinxin Wang, Andrew E Cornish, Mytrang H Do, Julia S Brunner, Ting-Wei Hsu, Zijian Xu, Isha Malik, Chaucie Edwards, Kristelle J Capistrano, Xian Zhang, Mark H Ginsberg, Lydia W S Finley, Megan S Lim, Steven M Horwitz, Ming O Li.

How genetic lesions drive cell transformation and whether they can be circumvented without compromising function of non-transformed cells are enduring questions in oncology. Here we show that in mature T cells-in which physiologic clonal proliferation is a cardinal feature- constitutive MYC transcription and Tsc1 loss in mice modeled aggressive human malignancy by reinforcing each other's oncogenic programs. This cooperation was supported by MYC-induced large neutral amino acid transporter chaperone SLC3A2 and dietary leucine, which in synergy with Tsc1 deletion overstimulated mTORC1 to promote mitochondrial fitness and MYC protein overexpression in a positive feedback circuit. A low leucine diet was therapeutic even in late-stage disease but did not hinder T cell immunity to infectious challenge, nor impede T cell transformation driven by constitutive nutrient mTORC1 signaling via Depdc5 loss. Thus, mTORC1 signaling hypersensitivity to leucine as an onco-nutrient enables an onco-circuit, decoupling pathologic from physiologic utilization of nutrient acquisition pathways.

DOI: https://doi.org/10.1101/2024.04.03.587917
Oncogene. 2024 Apr 17.

ULK1-dependent phosphorylation of PKM2 antagonizes O-GlcNAcylation and regulates the Warburg effect in breast cancer.

Zibin Zhou, Xiyuan Zheng, Jianxin Zhao, Aiyun Yuan, Zhuan Lv, Guangcan Shao, Bin Peng, Meng-Qiu Dong, Quan Xu, Xingzhi Xu, Jing Li.

Pyruvate kinase M2 (PKM2) is a central metabolic enzyme driving the Warburg effect in tumor growth. Previous investigations have demonstrated that PKM2 is subject to O-linked β-N-acetylglucosamine (O-GlcNAc) modification, which is a nutrient-sensitive post-translational modification. Here we found that unc-51 like autophagy activating kinase 1 (ULK1), a glucose-sensitive kinase, interacts with PKM2 and phosphorylates PKM2 at Ser333. Ser333 phosphorylation antagonizes PKM2 O-GlcNAcylation, promotes its tetramer formation and enzymatic activity, and decreases its nuclear localization. As PKM2 is known to have a nuclear role in regulating c-Myc, we also show that PKM2-S333 phosphorylation inhibits c-Myc expression. By downregulating glucose consumption and lactate production, PKM2 pS333 attenuates the Warburg effect. Through mouse xenograft assays, we demonstrate that the phospho-deficient PKM2-S333A mutant promotes tumor growth in vivo. In conclusion, we identified a ULK1-PKM2-c-Myc axis in inhibiting breast cancer, and a glucose-sensitive phosphorylation of PKM2 in modulating the Warburg effect.

DOI: https://doi.org/10.1038/s41388-024-03035-y
Biochem Biophys Res Commun. 2024 Apr 16. pii: S0006-291X(24)00459-5. [Epub ahead of print]712-713 149923

Stasimon/Tmem41b is required for cell proliferation and adult mouse survival.

Maria J Carlini, Meaghan Van Alstyne, Hua Yang, Shubhi Yadav, Neil A Shneider, Livio Pellizzoni.

  Stasimon/Tmem41b is a transmembrane protein with phospholipid scrambling activity that resides in the endoplasmic reticulum and has been implicated in autophagy, lipid metabolism, and viral replication. Stasimon/Tmem41b has also been linked to the function of sensory-motor circuits and the pathogenesis of spinal muscular atrophy. However, the early embryonic lethality of constitutive knockout in mice has hindered the analysis of spatial and temporal requirements of Stasimon/Tmem41b in vivo. To address this, we developed a novel mouse line harboring a conditional knockout allele of the Stasimon/Tmem41b gene in which exon 4 has been flanked by loxP sites (Stas/Tmem41bCKO). Cre-mediated recombination of Stas/Tmem41bCKO generates a functionally null allele (Stas/Tmem41bΔ4) resulting in loss of protein expression and embryonic lethality in the homozygous mouse mutant. Here, using a ubiquitously expressed, tamoxifen inducible Cre recombinase in the homozygous Stas/Tmem41bCKO mice, we demonstrate that postnatal depletion of Stasimon/Tmem41b rapidly arrests weight gain in adult mice and causes motor dysfunction and death approximately three weeks after tamoxifen treatment. Moreover, we show that depletion of Stasimon/Tmem41b severely affects cell proliferation in mouse embryonic fibroblasts. This study provides new insights into the essential requirement of Stasimon/Tmem41b for cellular and organismal fitness and expands the experimental toolkit to investigate its functions in the mammalian system.

Keywords:  Cell proliferation; Endoplasmic reticulum (ER); Lipid homeostasis; Phospholipid scramblase; Spinal muscular atrophy (SMA); Stasimon/Tmem41b

DOI:  https://doi.org/10.1016/j.bbrc.2024.149923
World J Gastroenterol. 2024 Mar 28. 30(12): 1764-1776

ALKBH5 suppresses autophagic flux via N6-methyladenosine demethylation of ZKSCAN3 mRNA in acute pancreatitis.

Tao Zhang, Shuai Zhu, Geng-Wen Huang.

  BACKGROUND: Increasing evidence has demonstrated that N6-methyladenosine (m6A) RNA modification plays an essential role in a wide range of pathological conditions. Impaired autophagy is a critical hallmark of acute pancreatitis (AP).AIM: To explore the role of the m6A modification of ZKSCAN3 in the regulation of autophagy in AP.
METHODS: The AP mouse cell model was established by cerulein-treated mouse pancreatic acinar cells (MPC-83), and the results were confirmed by the levels of amylase and inflammatory factors. Autophagy activity was evaluated by specific identification of the autophagy-related microstructure and the expression of autophagy-related genes. ZKSCAN3 and ALKBH5 were knocked down to study the function in AP. A m6A RNA binding protein immunoprecipitation assay was used to study how the m6A modification of ZKSCAN3 mRNA is regulated by ALKBH.
RESULTS: The increased expression of amylase and inflammatory factors in the supernatant and the accumulation of autophagic vacuoles verified that the AP mouse cell model was established. The downregulation of LAMP2 and upregulation of LC3-II/I and SQSTM1 demonstrated that autophagy was impaired in AP. The expression of ZKSCAN3 was upregulated in AP. Inhibition of ZKSCAN3 increased the expression of LAMP2 and decreased the expression of the inflammatory factors, LC3-II/I and SQSTM1. Furthermore, ALKBH5 was upregulated in AP. Knockdown of ALKBH5 downregulated ZKSCAN3 expression and restored decreased autophagic flux in AP. Notably, the bioinformatic analysis revealed 23 potential m6A modification sites on ZKSCAN3 mRNA. The m6A modification of ZKSCAN3 mRNA was significantly decreased in AP. Knockdown of ALKBH5 increased the modification of ZKSCAN3 mRNA, which confirmed that ALKBH5 upregulated ZKSCAN3 expression in a m6A-dependent manner.
CONCLUSION: ALKBH5 inhibits autophagic flux through m6A demethylation of ZKSCAN3 mRNA in AP, thereby aggravating the severity of the disease.

Keywords:  ALKBH5; Acute pancreatitis; Autophagy; N6-methyladenosine; ZKSCAN3

DOI:  https://doi.org/10.3748/wjg.v30.i12.1764
Neurochem Int. 2024 Apr 17. pii: S0197-0186(24)00073-1. [Epub ahead of print] 105746

Rapamycin improves the survival of epilepsy model cells by blocking phosphorylation of mTOR base on computer simulations and cellular experiments.

Kezhou Li, Jun-Feng Cao, Yunli Gong, Li Xiong, Mei Wu, Yue Qi, Xiran Ying, Dengxin Liu, Xuntai Ma, Xiao Zhang.

  PURPOSE: Epilepsy is a chronic brain dysfunction characterized by recurrent epileptic seizures. Rapamycin is a naturally occurring macrolide from Streptomyces hygroscopicus, and rapamycin may provide a protective effect on the nervous system by affecting mTOR. Therefore, we investigated the pharmacologic mechanism of rapamycin treating epilepsy through bioinformatics analysis, cellular experiments and supercomputer simulation.METHODS: Bioinformatics analysis was used to analyze targets of rapamycin treating epilepsy. We established epilepsy cell model by HT22 cells. RT-qPCR, WB and IF were used to verify the effects of rapamycin on mTOR at gene level and protein level. Computer simulations were used to model and evaluate the stability of rapamycin binding to mTOR protein.
RESULTS: Bioinformatics indicated mTOR played an essential role in signaling pathways of cell growth and cell metabolism. Cellular experiments showed that rapamycin could promote cell survival, and rapamycin did not have an effect on mRNA expression of mTOR. However, rapamycin was able to significantly inhibit the phosphorylation of mTOR at protein level. Computer simulations indicated that rapamycin was involved in the treatment of epilepsy through regulating phosphorylation of mTOR at protein level.
CONCLUSION: We found that rapamycin was capable of promoting the survival of epilepsy cells by inhibiting the phosphorylation of mTOR at protein level, and rapamycin did not have an effect on mRNA expression of mTOR. In addition to the traditional study that rapamycin affects mTORC1 complex by acting on FKBP12, this study found rapamycin could also directly block the phosphorylation of mTOR, therefore affecting the assembly of mTORC1 complex and mTOR signaling pathway.

Keywords:  Bioinformatics; Cellular experiments; Epilepsy; Molecular docking; Molecular dynamics; Phosphorylation; Rapamycin; mTOR

DOI:  https://doi.org/10.1016/j.neuint.2024.105746
Nat Commun. 2024 Apr 18. 15(1): 3326

Cdk8/CDK19 promotes mitochondrial fission through Drp1 phosphorylation and can phenotypically suppress pink1 deficiency in Drosophila.

Jenny Zhe Liao, Hyung-Lok Chung, Claire Shih, Kenneth Kin Lam Wong, Debdeep Dutta, Zelha Nil, Catherine Grace Burns, Oguz Kanca, Ye-Jin Park, Zhongyuan Zuo, Paul C Marcogliese, Katherine Sew, Hugo J Bellen, Esther M Verheyen.

Cdk8 in Drosophila is the orthologue of vertebrate CDK8 and CDK19. These proteins have been shown to modulate transcriptional control by RNA polymerase II. We found that neuronal loss of Cdk8 severely reduces fly lifespan and causes bang sensitivity. Remarkably, these defects can be rescued by expression of human CDK19, found in the cytoplasm of neurons, suggesting a non-nuclear function of CDK19/Cdk8. Here we show that Cdk8 plays a critical role in the cytoplasm, with its loss causing elongated mitochondria in both muscles and neurons. We find that endogenous GFP-tagged Cdk8 can be found in both the cytoplasm and nucleus. We show that Cdk8 promotes the phosphorylation of Drp1 at S616, a protein required for mitochondrial fission. Interestingly, Pink1, a mitochondrial kinase implicated in Parkinson's disease, also phosphorylates Drp1 at the same residue. Indeed, overexpression of Cdk8 significantly suppresses the phenotypes observed in flies with low levels of Pink1, including elevated levels of ROS, mitochondrial dysmorphology, and behavioral defects. In summary, we propose that Pink1 and Cdk8 perform similar functions to promote Drp1-mediated fission.

DOI: https://doi.org/10.1038/s41467-024-47623-8
Virology. 2024 Apr 09. pii: S0042-6822(24)00101-6. [Epub ahead of print]595 110080

AMPK restricts HHV-6A replication by inhibiting glycolysis and mTOR signaling.

Xiaodi Yang, Siyu Tian, Zhujiang Min, Emanuela Garbarino, Jingjing Ma, Junli Jia, Huamin Tang, Lingyun Li.

  AMP-activated protein kinase (AMPK) is a cellular energy sensor regulating metabolic homeostasis. In this study, we investigated the role of AMPK in response to human herpesvirus 6A (HHV-6A) infection. We show that HHV-6A infection significantly downregulates the active phosphorylated state of AMPK in infected T cells. Pharmacological activation of AMPK highly attenuated HHV-6A propagation. Mechanistically, we found that the activation of AMPK by AICAR blocked HHV-6-induced glycolysis by inhibiting glucose metabolism and lactate secretion, as well as decreasing expressions of key glucose transporters and glycolytic enzymes. In addition, mTOR signaling has been inactivated in HHV-6A infected T cells by AICAR treatment. We also showed that HHV-6A infection of human umbilical cord blood mononuclear cells (CBMCs) reduced AMPK activity whereas the activation of AMPK by metformin drastically reduced HHV-6A DNA replication and virions production. Taken together, this study demonstrates that AMPK is a promising antiviral therapeutic target against HHV-6A infection.

Keywords:  AMPK; Glycolysis; HHV-6A; Virus replication; mTOR signaling

DOI:  https://doi.org/10.1016/j.virol.2024.110080
Free Radic Biol Med. 2024 Apr 12. pii: S0891-5849(24)00385-X. [Epub ahead of print]

RNF31 alleviates liver steatosis by promoting p53/BNIP3-related mitophagy in hepatocytes.

Yifei Chen, Fuji Yang, Yujie Shi, Jingyu Sheng, Yanjin Wang, Liting Zhang, Jing Zhou, Yi Jin, Yongmin Yan.

  BACKGROUND & AIMS: Non-alcoholic fatty liver disease (NAFLD) is one of the liver illnesses that may be affected by mitophagy, which is the selective removal of damaged mitochondria. RNF31, an E3 ubiquitin ligase, is carcinogenic in many malignancies. However, the influence of RNF31 on mitochondrial homeostasis and NAFLD development remains unknown.METHODS: Oleic-palmitic acid treated hepatocytes and high-fat diet (HFD)-fed mice were established to observe the effect of RNF31 on hepatocyte mitophagy and steatosis. Mitophagy processes were comprehensively assessed by mt-Keima fluorescence imaging, while global changes in hepatic gene expression were measured by RNA-seq.
RESULTS: The present study discovered a reduction in RNF31 expression in lipotoxic hepatocytes with mitochondrial dysfunction. The observed decrease in RNF31 expression was associated with reduced mitochondrial membrane potential, disturbed mitophagy, and increased steatosis. Additionally, the findings indicated that RNF31 is a pivotal factor in the initiation of mitophagy and the facilitation of mitochondrial homeostasis, resulting in a decrease in steatosis in lipotoxic hepatocytes. Mechanistically, RNF31 enhanced p53 ubiquitination and subsequent proteasomal degradation. Down-regulation of p53 led to increased expression of the mitophagy receptor protein BCL2 and adenovirus E1B 19 kDa-interacting protein 3 (BNIP3), thereby promoting mitophagy in hepatocytes. Furthermore, it was demonstrated that the transportation of RNF31 via small extracellular vesicles derived from mesenchymal stem cells (referred to as sEV) had a substantial influence on reducing hepatic steatosis and restoring liver function in HFD-fed mice.
CONCLUSIONS: The findings highlight RNF31's essential role in the regulation of mitochondrial homeostasis in hepatocytes, emphasizing its potential as a therapeutic target for NAFLD.

Keywords:  Extracellular vesicles; Mitophagy; RNF31; Steatosis

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.04.214