bims-lysosi Biomed News
on Lysosomes and signaling
Issue of 2020‒10‒18
forty-three papers selected by
Stephanie Fernandes
Max Planck Institute for Biology of Ageing
  1. The GATOR-Rag GTPase pathway inhibits mTORC1 activation by lysosome-derived amino acids.
  2. LRRK2 and the Endolysosomal System in Parkinson's Disease.
  3. Inappropriate cathepsin K secretion promotes its enzymatic activation driving heart and valve malformation.
  4. The lysosomal membrane - export of metabolites and beyond.
  5. SMAD3 promotes autophagy dysregulation by triggering lysosome depletion in tubular epithelial cells in diabetic nephropathy.
  6. A dysfunctional endolysosomal pathway common to two sub-types of demyelinating Charcot-Marie-Tooth disease.
  7. Treatment for Lysosomal Storage Disorders.
  8. Inhibition of class I PI3K enhances chaperone-mediated autophagy.
  9. Cathepsin D deficiency in mammary epithelium transiently stalls breast cancer by interference with mTORC1 signaling.
  10. Brain Penetrable Inhibitors of Ceramide Galactosyltransferase for the Treatment of Lysosomal Storage Disorders.
  11. Human iPSC-Based Models for the Development of Therapeutics Targeting Neurodegenerative Lysosomal Storage Diseases.
  12. Failures of Endochondral Ossification in the Mucopolysaccharidoses.
  13. A single injection of an optimized AAV vector into cerebrospinal fluid corrects neurological disease in a murine model of GM1 gangliosidosis.
  14. Phosphatidylinositol 4,5-bisphosphate in the Control of Membrane Trafficking.
  15. Combined valve replacement and aortocoronary bypass in an adult mucopolysaccharidosis type VII patient.
  16. Inositol requiring enzyme 1 alpha (IRE1a) links palmitate-induced mTOR activation and lipotoxicity in Hepatocytes.
  17. Early indicators of disease progression in Fabry disease that may indicate the need for disease-specific treatment initiation: findings from the opinion-based PREDICT-FD modified Delphi consensus initiative.
  18. RegX3 Activates whiB3 Under Acid Stress and Subverts Lysosomal Trafficking of Mycobacterium tuberculosis in a WhiB3-Dependent Manner.
  19. [Fabry disease].
  20. mTORC1/2 signaling is downregulated by amino acid-free culture of mouse preimplantation embryos and is only partially restored by amino acid re-addition.
  21. Body composition and 6 minute walking ability in late-onset Pompe disease patients after 9 years of enzyme replacement therapy.
  22. A late-onset male Fabry disease patient with somatic mosaicism of a classical GLA mutation: a case report.
  23. Parkinsonism in Patients with Neuronopathic (Type 3) Gaucher Disease: A Case Series.
  24. The promise of mTOR as a therapeutic target pathway in idiopathic pulmonary fibrosis.
  25. Parallel global profiling of plant TOR dynamics reveals a conserved role for LARP1 in translation.
  26. mTOR Signaling in Metabolism and Cancer.
  27. Amino Acid Sensing in Metabolic Homeostasis and Health.
  28. TBC1D15/RAB7-regulated mitochondria-lysosome interaction confers cardioprotection against acute myocardial infarction-induced cardiac injury.
  29. Tuberous Sclerosis Complex as Disease Model for Investigating mTOR-Related Gliopathy During Epileptogenesis.
  30. Interrogation of kinase genetic interactions provides a global view of PAK1-mediated signal transduction pathways.
  31. BNIP3L/Nix-induced mitochondrial fission, mitophagy, and impaired myocyte glucose uptake are abrogated by PRKA/PKA phosphorylation.
  32. Mycobacterium tuberculosis Calcium Pump CtpF Modulates the Autophagosome in an mTOR-Dependent Manner.
  33. A MicroRNA Linking Human Positive Selection and Metabolic Disorders.
  34. Therapeutic Potential of PI3K/AKT/mTOR Pathway in Gastrointestinal Stromal Tumors: Rationale and Progress.
  35. The Ccr4-Not complex regulates TORC1 signaling and mitochondrial metabolism by promoting vacuole V-ATPase activity.
  36. The role of Immunity in Fabry Disease and Hypertension: A Review of a Novel Common Pathway.
  37. A Phase 2/3 Trial of Pabinafusp Alfa, IDS Fused with Anti-Human Transferrin Receptor Antibody, Targeting Neurodegeneration in MPS-II.
  38. HSP70 interacts with Rheb, inhibiting mTORC1 signaling.
  39. Modular metabolite assembly in C. elegans depends on carboxylesterases and formation of lysosome-related organelles.
  40. Ciliary localization of folliculin mediated via a kinesin-2-binding motif is required for its functions in mTOR regulation and tumor suppression.
  41. Translation of Tudor-SN, a novel terminal oligo-pyrimidine (TOP) mRNA, is regulated by the mTORC1 pathway in cardiomyocytes.
  42. Nucleus distribution of cathepsin B in senescent microglia promotes brain aging through degradation of sirtuins.
  43. Ribosome profiling in mouse hippocampus: plasticity-induced regulation and bidirectional control by TSC2 and FMRP.
  1. Science. 2020 Oct 16. 370(6514): 351-356
    The GATOR-Rag GTPase pathway inhibits mTORC1 activation by lysosome-derived amino acids.
    Geoffrey G Hesketh, Fotini Papazotos, Judy Pawling, Dushyandi Rajendran, James D R Knight, Sebastien Martinez, Mikko Taipale, Daniel Schramek, James W Dennis, Anne-Claude Gingras.
      The mechanistic target of rapamycin complex 1 (mTORC1) couples nutrient sufficiency to cell growth. mTORC1 is activated by exogenously acquired amino acids sensed through the GATOR-Rag guanosine triphosphatase (GTPase) pathway, or by amino acids derived through lysosomal degradation of protein by a poorly defined mechanism. Here, we revealed that amino acids derived from the degradation of protein (acquired through oncogenic Ras-driven macropinocytosis) activate mTORC1 by a Rag GTPase-independent mechanism. mTORC1 stimulation through this pathway required the HOPS complex and was negatively regulated by activation of the GATOR-Rag GTPase pathway. Therefore, distinct but functionally coordinated pathways control mTORC1 activity on late endocytic organelles in response to distinct sources of amino acids.
    DOI:  https://doi.org/10.1126/science.aaz0863
  2. J Parkinsons Dis. 2020 Oct 02.
    LRRK2 and the Endolysosomal System in Parkinson's Disease.
    Madalynn L Erb, Darren J Moore.
      Mutations in leucine-rich repeat kinase 2 (LRRK2) cause autosomal dominant familial Parkinson's disease (PD), with pathogenic mutations enhancing LRRK2 kinase activity. There is a growing body of evidence indicating that LRRK2 contributes to neuronal damage and pathology both in familial and sporadic PD, making it of particular interest for understanding the molecular pathways that underlie PD. Although LRRK2 has been extensively studied to date, our understanding of the seemingly diverse functions of LRRK2 throughout the cell remains incomplete. In this review, we discuss the functions of LRRK2 within the endolysosomal pathway. Endocytosis, vesicle trafficking pathways, and lysosomal degradation are commonly disrupted in many neurodegenerative diseases, including PD. Additionally, many PD-linked gene products function in these intersecting pathways, suggesting an important role for the endolysosomal system in maintaining protein homeostasis and neuronal health in PD. LRRK2 activity can regulate synaptic vesicle endocytosis, lysosomal function, Golgi network maintenance and sorting, vesicular trafficking and autophagy, with alterations in LRRK2 kinase activity serving to disrupt or regulate these pathways depending on the distinct cell type or model system. LRRK2 is critically regulated by at least two proteins in the endolysosomal pathway, Rab29 and VPS35, which may serve as master regulators of LRRK2 kinase activity. Investigating the function and regulation of LRRK2 in the endolysosomal pathway in diverse PD models, especially in vivo models, will provide critical insight into the cellular and molecular pathophysiological mechanisms driving PD and whether LRRK2 represents a viable drug target for disease-modification in familial and sporadic PD.
    Keywords:  Leucine-rich repeat kinase 2; Parkinson’s disease; endocytosis; lysosomes; trans-Golgi network; vesicular trafficking
    DOI:  https://doi.org/10.3233/JPD-202138
  3. JCI Insight. 2020 Oct 15. pii: 133019. [Epub ahead of print]5(20):
    Inappropriate cathepsin K secretion promotes its enzymatic activation driving heart and valve malformation.
    Po-Nien Lu, Trevor Moreland, Courtney J Christian, Troy C Lund, Richard A Steet, Heather Flanagan-Steet.
      Although congenital heart defects (CHDs) represent the most common birth defect, a comprehensive understanding of disease etiology remains unknown. This is further complicated since CHDs can occur in isolation or as a feature of another disorder. Analyzing disorders with associated CHDs provides a powerful platform to identify primary pathogenic mechanisms driving disease. Aberrant localization and expression of cathepsin proteases can perpetuate later-stage heart diseases, but their contribution toward CHDs is unclear. To investigate the contribution of cathepsins during cardiovascular development and congenital disease, we analyzed the pathogenesis of cardiac defects in zebrafish models of the lysosomal storage disorder mucolipidosis II (MLII). MLII is caused by mutations in the GlcNAc-1-phosphotransferase enzyme (Gnptab) that disrupt carbohydrate-dependent sorting of lysosomal enzymes. Without Gnptab, lysosomal hydrolases, including cathepsin proteases, are inappropriately secreted. Analyses of heart development in gnptab-deficient zebrafish show cathepsin K secretion increases its activity, disrupts TGF-β-related signaling, and alters myocardial and valvular formation. Importantly, cathepsin K inhibition restored normal heart and valve development in MLII embryos. Collectively, these data identify mislocalized cathepsin K as an initiator of cardiac disease in this lysosomal disorder and establish cathepsin inhibition as a viable therapeutic strategy.
    Keywords:  Cardiovascular disease; Cell Biology; Development; Lysosomes; Proteases
    DOI:  https://doi.org/10.1172/jci.insight.133019
  4. FEBS J. 2020 Oct 17.
    The lysosomal membrane - export of metabolites and beyond.
    Sönke Rudnik, Markus Damme.
      Lysosomes are degradative organelles in eukaryotic cells mediating the hydrolytic catabolism of various macromolecules to small basic building blocks. These low molecular weight metabolites are transported across the lysosomal membrane and re-used in the cytoplasm and other organelles for biosynthetic pathways. Even though in the past 20 years our understanding of the lysosomal membrane regarding various transporters, other integral- and peripheral-membrane proteins, the lipid composition but also its turnover has greatly improved, there are still many unresolved questions concerning key aspects of the function of the lysosomal membrane. These include a possible function of lysosomes as a cellular storage compartment, yet unidentified transporters mediating the export e.g. of various amino acids, mechanisms mediating the transport of lysosomal membrane proteins from the Golgi apparatus to lysosomes, and the turnover of lysosomal membrane proteins. We here review the current knowledge about the lysosomal membrane and identify some of the open questions that need to be solved in the future for a comprehensive and complete understanding of how lysosomes communicate with other organelles, cellular processes, and pathways.
    Keywords:  Accessory subunits; Lysosomal Membrane; Lysosomal Storage Diseases; Transporter
    DOI:  https://doi.org/10.1111/febs.15602
  5. Autophagy. 2020 Oct 12. 1-20
    SMAD3 promotes autophagy dysregulation by triggering lysosome depletion in tubular epithelial cells in diabetic nephropathy.
    Chen Yang, Xiao-Cui Chen, Zhi-Hang Li, Hong-Luan Wu, Kai-Peng Jing, Xiao-Ru Huang, Lin Ye, Biao Wei, Hui-Yao Lan, Hua-Feng Liu.
      Macroautophagy/autophagy dysregulation has been noted in diabetic nephropathy; however, the regulatory mechanisms controlling this process remain unclear. In this study, we showed that SMAD3 (SMAD family member 3), the key effector of TGFB (transforming growth factor beta)-SMAD signaling, induces lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis. The pharmacological inhibition or genetic deletion of SMAD3 restored lysosome biogenesis activity by alleviating the suppression of TFEB, thereby protecting lysosomes from depletion and improving autophagic flux in renal tubular epithelial cells in diabetic nephropathy. Mechanistically, we found that SMAD3 directly binds to the 3'-UTR of TFEB and inhibits its transcription. Silencing TFEB suppressed lysosome biogenesis and resulted in a loss of the protective effects of SMAD3 inactivation on lysosome depletion under diabetic conditions. In conclusion, SMAD3 promotes lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis; this may be an important mechanism underlying autophagy dysregulation in the progression of diabetic nephropathy. Abbreviations: AGEs: advanced glycation end products; ATP6V1H: ATPase H+ transporting V1 subunit H; CTSB: cathepsin B; ChIP: chromatin immunoprecipitation; Co-BSA: control bovine serum albumin; DN: diabetic nephropathy; ELISA: enzyme-linked immunosorbent assay; FN1: fibronectin 1; HAVCR1/TIM1/KIM-1: hepatitis A virus cellular receptor 1; LAMP1: lysosomal associated membrane protein 1; LMP: lysosome membrane permeabilization; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; NC: negative control; SIS3: specific inhibitor of SMAD3; SMAD3: SMAD family member 3; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TECs: tubular epithelial cells; TFEB: transcription factor EB; TGFB1: transforming growth factor beta 1; TGFBR1: transforming growth factor beta receptor 1; UTR: untranslated region; VPS11: VPS11 core subunit of CORVET and HOPS complexes.
    Keywords:  Autophagy; SMAD3; TFEB; diabetic nephropathy; lysosome; tubular epithelial cell
    DOI:  https://doi.org/10.1080/15548627.2020.1824694
  6. Acta Neuropathol Commun. 2020 Oct 15. 8(1): 165
    A dysfunctional endolysosomal pathway common to two sub-types of demyelinating Charcot-Marie-Tooth disease.
    James R Edgar, Anita K Ho, Matilde Laurá, Rita Horvath, Mary M Reilly, J Paul Luzio, Rhys C Roberts.
      Autosomal dominant mutations in LITAF are responsible for the rare demyelinating peripheral neuropathy, Charcot-Marie-Tooth disease type 1C (CMT1C). The LITAF protein is expressed in many human cell types and we have investigated the consequences of two different LITAF mutations in primary fibroblasts from CMT1C patients using confocal and electron microscopy. We observed the appearance of vacuolation/enlargement of late endocytic compartments (late endosomes and lysosomes). This vacuolation was also observed after knocking out LITAF from either control human fibroblasts or from the CMT1C patient-derived cells, consistent with it being the result of loss-of-function mutations in the CMT1C fibroblasts. The vacuolation was similar to that previously observed in fibroblasts from CMT4J patients, which have autosomal recessive mutations in FIG4. The FIG4 protein is a component of a phosphoinositide kinase complex that synthesises phosphatidylinositol 3,5-bisphosphate on the limiting membrane of late endosomes. Phosphatidylinositol 3,5-bisphosphate activates the release of lysosomal Ca2+ through the cation channel TRPML1, which is required to maintain the homeostasis of endosomes and lysosomes in mammalian cells. We observed that a small molecule activator of TRPML1, ML-SA1, was able to rescue the vacuolation phenotype of LITAF knockout, FIG4 knockout and CMT1C patient fibroblasts. Our data describe the first cellular phenotype common to two different subtypes of demyelinating CMT and are consistent with LITAF and FIG4 functioning on a common endolysosomal pathway that is required to maintain the homeostasis of late endosomes and lysosomes. Although our experiments were on human fibroblasts, they have implications for our understanding of the molecular pathogenesis and approaches to therapy in two subtypes of demyelinating Charcot-Marie-Tooth disease.
    Keywords:  Charcot–Marie–Tooth; Endosome; LITAF; Lysosome; Peripheral neuropathy; Phosphoinositide
    DOI:  https://doi.org/10.1186/s40478-020-01043-z
  7. Curr Pharm Des. 2020 Oct 15.
    Treatment for Lysosomal Storage Disorders.
    Jayesh Sheth, Aadhira A Nair.
      Lysosomal storage disorders comprise a group of approximately 70 types of inherited diseases resulting due to lysosomal gene defects. The outcome of the defect is a deficiency in either of the three: namely lysosomal enzymes, activator protein, or transmembrane protein as a result of which there is an unwanted accumulation of biomolecules inside the lysosomes. The pathophysiology of these conditions is complex affecting several organ systems and nervous system involvement in a majority of cases. Several research studies have well elucidated the mechanism underlying the disease condition leading to the development in devising the treatment strategies for the same. Currently, these approaches aim to reduce the severity of symptoms or delay the disease progression but do not provide a complete cure. The main treatment methods include Enzyme replacement therapy, Bone marrow transplantation, Substrate reduction therapy, use of molecular chaperones, and Gene therapy. This review article presents an elaborate description of these strategies and discusses the ongoing studies for the same.
    Keywords:  BMT; ERT; Lysosomal storage disorders; Lysosomes; SRT; chaperones; enzyme; gene therapy; transplantation
    DOI:  https://doi.org/10.2174/1381612826666201015154932
  8. J Cell Biol. 2020 Dec 07. pii: e202001031. [Epub ahead of print]219(12):
    Inhibition of class I PI3K enhances chaperone-mediated autophagy.
    S Joseph Endicott, Zachary J Ziemba, Logan J Beckmann, Dennis N Boynton, Richard A Miller.
      Chaperone-mediated autophagy (CMA) is the most selective form of lysosomal proteolysis, where individual peptides, recognized by a consensus motif, are translocated directly across the lysosomal membrane. CMA regulates the abundance of many disease-related proteins, with causative roles in neoplasia, neurodegeneration, hepatosteatosis, and other pathologies relevant to human health and aging. At the lysosomal membrane, CMA is inhibited by Akt-dependent phosphorylation of the CMA regulator GFAP. The INS-PI3K-PDPK1 pathway regulates Akt, but its role in CMA is unclear. Here, we report that inhibition of class I PI3K or PDPK1 activates CMA. In contrast, selective inhibition of class III PI3Ks does not activate CMA. Isolated liver lysosomes from mice treated with either of two orally bioavailable class I PI3K inhibitors, pictilisib or buparlisib, display elevated CMA activity, and decreased phosphorylation of lysosomal GFAP, with no change in macroautophagy. The findings of this study represent an important first step in repurposing class I PI3K inhibitors to modulate CMA in vivo.
    DOI:  https://doi.org/10.1083/jcb.202001031
  9. Nat Commun. 2020 10 12. 11(1): 5133
    Cathepsin D deficiency in mammary epithelium transiently stalls breast cancer by interference with mTORC1 signaling.
    Stephanie Ketterer, Julia Mitschke, Anett Ketscher, Manuel Schlimpert, Wilfried Reichardt, Natascha Baeuerle, Maria Elena Hess, Patrick Metzger, Melanie Boerries, Christoph Peters, Bernd Kammerer, Tilman Brummer, Florian Steinberg, Thomas Reinheckel.
      Cathepsin D (CTSD) is a lysosomal protease and a marker of poor prognosis in breast cancer. However, the cells responsible for this association and the function of CTSD in cancer are still incompletely understood. By using a conditional CTSD knockout mouse crossed to the transgenic MMTV-PyMT breast cancer model we demonstrate that CTSD deficiency in the mammary epithelium, but not in myeloid cells, blocked tumor development in a cell-autonomous manner. We show that lack of CTSD impaired mechanistic Target of Rapamycin Complex 1 (mTORC1) signaling and induced reversible cellular quiescence. In line, CTSD-deficient tumors started to grow with a two-month delay and quiescent Ctsd-/- tumor cells re-started proliferation upon long-term culture. This was accompanied by rewiring of oncogenic gene expression and signaling pathways, while mTORC1 signaling remained permanently disabled in CTSD-deficient cells. Together, these studies reveal a tumor cell-autonomous effect of CTSD deficiency, and establish a pivotal role of this protease in the cellular response to oncogenic stimuli.
    DOI:  https://doi.org/10.1038/s41467-020-18935-2
  10. ACS Med Chem Lett. 2020 Oct 08. 11(10): 2010-2016
    Brain Penetrable Inhibitors of Ceramide Galactosyltransferase for the Treatment of Lysosomal Storage Disorders.
    Sukanthini Thurairatnam, Sungtaek Lim, Robert H Barker, Yong Mi Choi-Sledeski, Bradford H Hirth, John Jiang, John E Macor, Elina Makino, Sachin Maniar, Kwon Musick, James R Pribish, Mark Munson.
      Metachromatic leukodystrophy (MLD) is a rare, genetic lysosomal storage disorder caused by the deficiency of arylsulfatase A enzyme, which results in the accumulation of sulfatide in the lysosomes of the tissues of central and peripheral nervous systems, leading to progressive demyelination and neurodegeneration. Currently there is no cure for this disease, and the only approved therapy, hematopoietic stem cell transplant, has limitations. We proposed substrate reduction therapy (SRT) as a novel approach to treat this disease, by inhibiting ceramide galactosyltransferase enzyme (UGT8). This resulted in the identification of a thienopyridine scaffold as a starting point to initiate medicinal chemistry. Further optimization of hit compound 1 resulted in the identification of brain penetrable, orally bioavailable compound 19, which showed efficacy in the in vivo pharmacodynamic models, indicating the potential to treat MLD with UGT8 inhibitors.
    DOI:  https://doi.org/10.1021/acsmedchemlett.0c00120
  11. Front Mol Biosci. 2020 ;7 224
    Human iPSC-Based Models for the Development of Therapeutics Targeting Neurodegenerative Lysosomal Storage Diseases.
    Marco Luciani, Angela Gritti, Vasco Meneghini.
      Lysosomal storage diseases (LSDs) are a group of rare genetic conditions. The absence or deficiency of lysosomal proteins leads to excessive storage of undigested materials and drives secondary pathological mechanisms including autophagy, calcium homeostasis, ER stress, and mitochondrial abnormalities. A large number of LSDs display mild to severe central nervous system (CNS) involvement. Animal disease models and post-mortem tissues partially recapitulate the disease or represent the final stage of CNS pathology, respectively. In the last decades, human models based on induced pluripotent stem cells (hiPSCs) have been extensively applied to investigate LSD pathology in several tissues and organs, including the CNS. Neural stem/progenitor cells (NSCs) derived from patient-specific hiPSCs (hiPS-NSCs) are a promising tool to define the effects of the pathological storage on neurodevelopment, survival and function of neurons and glial cells in neurodegenerative LSDs. Additionally, the development of novel 2D co-culture systems and 3D hiPSC-based models is fostering the investigation of neuron-glia functional and dysfunctional interactions, also contributing to define the role of neurodevelopment and neuroinflammation in the onset and progression of the disease, with important implications in terms of timing and efficacy of treatments. Here, we discuss the advantages and limits of the application of hiPS-NSC-based models in the study and treatment of CNS pathology in different LSDs. Additionally, we review the state-of-the-art and the prospective applications of NSC-based therapy, highlighting the potential exploitation of hiPS-NSCs for gene and cell therapy approaches in the treatment of neurodegenerative LSDs.
    Keywords:  cell therapy; central nervous system; drug discovery; gene therapy; induced pluripotent stem cells; lysosomal storage disorders; neural stem cells; organoids
    DOI:  https://doi.org/10.3389/fmolb.2020.00224
  12. Curr Osteoporos Rep. 2020 Oct 16.
    Failures of Endochondral Ossification in the Mucopolysaccharidoses.
    Zhirui Jiang, Sharon Byers, Margret L Casal, Lachlan J Smith.
      PURPOSE OF REVIEW: The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders characterized by abnormal accumulation of glycosaminoglycans (GAGs) in cells and tissues. MPS patients frequently exhibit failures of endochondral ossification during postnatal growth leading to skeletal deformity and short stature. In this review, we outline the current understanding of the cellular and molecular mechanisms underlying failures of endochondral ossification in MPS and discuss associated treatment challenges and opportunities.RECENT FINDINGS: Studies in MPS patients and animal models have demonstrated that skeletal cells and tissues exhibit significantly elevated GAG storage from early in postnatal life and that this is associated with impaired cartilage-to-bone conversion in primary and secondary ossification centers, and growth plate dysfunction. Recent studies have begun to elucidate the underlying cellular and molecular mechanisms, including impaired chondrocyte proliferation and hypertrophy, diminished growth factor signaling, disrupted cell cycle progression, impaired autophagy, and increased cell stress and apoptosis. Current treatments such as hematopoietic stem cell transplantation and enzyme replacement therapy fail to normalize endochondral ossification in MPS. Emerging treatments including gene therapy and small molecule-based approaches hold significant promise in this regard. Failures of endochondral ossification contribute to skeletal deformity and short stature in MPS patients, increasing mortality and reducing quality of life. Early intervention is crucial for effective treatment, and there is a critical need for new approaches that normalize endochondral ossification by directly targeting affected cells and signaling pathways.
    Keywords:  Endochondral ossification; Growth plate; Lysosomal storage disorder; Mucopolysaccharidosis; Short stature; Skeletal deformity
    DOI:  https://doi.org/10.1007/s11914-020-00626-y
  13. Hum Gene Ther. 2020 Oct 12.
    A single injection of an optimized AAV vector into cerebrospinal fluid corrects neurological disease in a murine model of GM1 gangliosidosis.
    Christian Hinderer, Brenden Nosratbakhsh, Nathan Katz, James M Wilson.
      GM1 gangliosidosis is a rare neurodegenerative lysosomal storage disease caused by loss-of-function mutations in the gene encoding beta galactosidase (β-gal). There are no approved treatments for GM1 gangliosidosis. Previous studies in animal models have demonstrated that adeno-associated viral (AAV) vector-mediated gene transfer to the brain can restore β-gal expression and prevent the onset of neurological signs. We developed an optimized AAV vector expressing human β-gal and evaluated the efficacy of a single intracerebroventricular injection of this vector into the cerebrospinal fluid (CSF) of a murine disease model. AAV vector administration into the CSF increased β-gal activity in the brain, reduced neuronal lysosomal storage lesions, prevented onset of neurological signs and gait abnormalities, and increased survival. These findings demonstrate the potential therapeutic activity of this vector and support subsequent clinical development for the treatment of GM1 gangliosidosis.
    DOI:  https://doi.org/10.1089/hum.2018.206
  14. Int J Biol Sci. 2020 ;16(15): 2761-2774
    Phosphatidylinositol 4,5-bisphosphate in the Control of Membrane Trafficking.
    Suhua Li, Chinmoy Ghosh, Yanli Xing, Yue Sun.
      Phosphoinositides are membrane lipids generated by phosphorylation on the inositol head group of phosphatidylinositol. By specifically distributed to distinct subcellular membrane locations, different phosphoinositide species play diverse roles in modulating membrane trafficking. Among the seven known phosphoinositide species, phosphatidylinositol 4,5-bisphosphate (PI4,5P2) is the one species most abundant at the plasma membrane. Thus, the PI4,5P2 function in membrane trafficking is first identified in controlling plasma membrane dynamic-related events including endocytosis and exocytosis. However, recent studies indicate that PI4,5P2 is also critical in many other membrane trafficking events such as endosomal trafficking, hydrolases sorting to lysosomes, autophagy initiation, and autophagic lysosome reformation. These findings suggest that the role of PI4,5P2 in membrane trafficking is far beyond just plasma membrane. This review will provide a concise synopsis of how PI4,5P2 functions in multiple membrane trafficking events. PI4,5P2, the enzymes responsible for PI4,5P2 production at specific subcellular locations, and distinct PI4,5P2 effector proteins compose a regulation network to control the specific membrane trafficking events.
    Keywords:  5P2; PI4; PIPK; autophagy; endosome; lysosome; membrane trafficking
    DOI:  https://doi.org/10.7150/ijbs.49665
  15. Cardiovasc Pathol. 2020 Oct 09. pii: S1054-8807(20)30101-0. [Epub ahead of print] 107297
    Combined valve replacement and aortocoronary bypass in an adult mucopolysaccharidosis type VII patient.
    Josef Marek, Petr Kuchynka, Vladimir Mikulenka, Tomas Palecek, Jakub Sikora, Helena Hulkova, Lukas Lambert, Hana Linkova, David Zemanek, Marketa Tesarova, Ales Linhart, Jiri Zeman, Martin Magner.
      Mucopolysaccharidosis type VII (MPS VII) is a rare autosomal recessive lysosomal storage disorder. MPS VII is caused by mutations in the GUSB gene that encodes β-glucuronidase. Adult MPS VII patients present with musculoskeletal abnormalities, coarse features, and corneal clouding. Cardiac and valvular impairment are common; however, severe valvular disease necessitating surgery has not yet been reported. We present a 32-year-old male MPS VII patient admitted to our hospital with decompensated heart failure. We identified aortic valve disease with severe stenosis (valve area 0.69 cm2) and moderate regurgitation. Severe mitral valve stenosis (valve area 1cm2) with moderate to severe regurgitation was also found in the patient. In addition, an occlusion of the right coronary artery (RCA) was documented. The patient underwent surgical replacement of the mitral and aortic valves with mechanical prostheses and implantation of a venous bypass graft to his RCA. The surgery led to a significant improvement of his clinical symptoms. Six months after the procedure, both mechanical valves function normally. Histopathological assessment identified chronic inflammatory infiltrates, fibrosis and calcifications in both resected valves. Foamy cytoplasmic transformation was most evident in the valvular interstitial cells. The ultrastructural vacuolar abnormality seen in these cells corresponded to storage changes observed in other MPSs. In conclusion, we describe clinical findings and valvular pathology in an MPS VII patient with the first-reported successful combined surgical valve replacement and myocardial revascularization. The histological and ultrastructural analyses revealed that the lysosomal storage predominantly affected the valvular interstitial cells.
    Keywords:  Sly syndrome; cardiac surgery; cardiomyopathy; coronary artery disease; mucopolysaccharidosis type VII; valve replacement; valvular disease
    DOI:  https://doi.org/10.1016/j.carpath.2020.107297
  16. Am J Physiol Cell Physiol. 2020 Oct 14.
    Inositol requiring enzyme 1 alpha (IRE1a) links palmitate-induced mTOR activation and lipotoxicity in Hepatocytes.
    Yingli Chen, Alexandra Griffiths, Jun Wang, Tingting Zhang, Qing Song, Zhenyuan Song.
      Hepatic lipotoxicity, hepatocyte dysfunction/cell death induced by saturated fatty acids (SFA), plays a central role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD); however, the underlying mechanisms remain unclear. Palmitate is the most abundant SFA in the circulation. In this study, via a small-scale screening of chemical inhibitors using AML12 hepatocytes, we identified mTOR complex 1 (mTORC1) to be a culprit in palmitate-induced cell death in hepatocytes in that mTOR inhibition is protective against palmitate-induced cell death. The protective effects of mTORC1 inhibition are independent of autophagy induction as autophagy inhibition failed to ablate the mTORC1 inhibitor-conferred protection. We have previously reported that the endonuclease activity of inositol-requiring enzyme 1a (IRE1a), one of three canonical signaling pathways of endoplasmic reticulum (ER) stress, was implicated in palmitate-induced cell death in hepatocytes. The continuous mechanistic investigation in this study revealed that IRE1α is a downstream target of mTORC1 activation upon palmitate exposure and the inhibition of either its endonuclease activity or kinase activity protected against the lipotoxic effect of palmitate. Our research further uncovered that protein palmitoylation is potentially involved in palmitate-induced mTORC1 activation and lipotoxicity in hepatocytes. 2-bromopalmitate, a protein palmitoylation inhibitor, ameliorated palmitate-triggered mTORC1 activation, concomitant with prevention of lipotoxicity in hepatocytes. Collectively, our data have identified that mTORC1 and ER stress are coordinately implicated in hepatocyte cell death in response to palmitate exposure and suggests that this pathway may potentially serve as a therapeutic target for the treatment of NAFLD as well as other metabolic disorders involving lipotoxicity.
    Keywords:  ER stress; IRE1alpha; Lipotoxicity; Palmitate; mTORC1
    DOI:  https://doi.org/10.1152/ajpcell.00165.2020
  17. BMJ Open. 2020 Oct 10. 10(10): e035182
    Early indicators of disease progression in Fabry disease that may indicate the need for disease-specific treatment initiation: findings from the opinion-based PREDICT-FD modified Delphi consensus initiative.
    Derralynn A Hughes, Patricio Aguiar, Patrick B Deegan, Fatih Ezgu, Andrea Frustaci, Olivier Lidove, Aleš Linhart, Jean-Claude Lubanda, James C Moon, Kathleen Nicholls, Dau-Ming Niu, Albina Nowak, Uma Ramaswami, Ricardo Reisin, Paula Rozenfeld, Raphael Schiffmann, Einar Svarstad, Mark Thomas, Roser Torra, Bojan Vujkovac, David G Warnock, Michael L West, Jack Johnson, Mark J Rolfe, Sandro Feriozzi.
      OBJECTIVES: The PRoposing Early Disease Indicators for Clinical Tracking in Fabry Disease (PREDICT-FD) initiative aimed to reach consensus among a panel of global experts on early indicators of disease progression that may justify FD-specific treatment initiation.DESIGN AND SETTING: Anonymous feedback from panellists via online questionnaires was analysed using a modified Delphi consensus technique. Questionnaires and data were managed by an independent administrator directed by two non-voting cochairs. First, possible early indicators of renal, cardiac and central/peripheral nervous system (CNS/PNS) damage, and other disease and patient-reported indicators assessable in routine clinical practice were compiled by the cochairs and administrator from panellists' free-text responses. Second, the panel scored indicators for importance (5-point scale: 1=not important; 5=extremely important); indicators scoring ≥3 among >75% of panellists were then rated for agreement (5-point scale: 1=strongly disagree; 5=strongly agree). Indicators awarded an agreement score ≥4 by >67% of panellists achieved consensus. Finally, any panel-proposed refinements to consensus indicator definitions were adopted if >75% of panellists agreed.
    RESULTS: A panel of 21 expert clinicians from 15 countries provided information from which 83 possible current indicators of damage (kidney, 15; cardiac, 15; CNS/PNS, 13; other, 16; patient reported, 24) were compiled. Of 45 indicators meeting the importance criteria, consensus was reached for 29 and consolidated as 27 indicators (kidney, 6; cardiac, 10; CNS/PNS, 2; other, 6; patient reported, 3) including: (kidney) elevated albumin:creatinine ratio, histological damage, microalbuminuria; (cardiac) markers of early systolic/diastolic dysfunction, elevated serum cardiac troponin; (CNS/PNS) neuropathic pain, gastrointestinal symptoms suggestive of gastrointestinal neuropathy; (other) pain in extremities/neuropathy, angiokeratoma; (patient-reported) febrile crises, progression of symptoms/signs. Panellists revised and approved proposed chronologies of when the consensus indicators manifest. The panel response rate was >95% at all stages.
    CONCLUSIONS: PREDICT-FD captured global opinion regarding current clinical indicators that could prompt FD-specific treatment initiation earlier than is currently practised.
    Keywords:  cardiomyopathy; chronic renal failure; genetics; stroke medicine
    DOI:  https://doi.org/10.1136/bmjopen-2019-035182
  18. Front Microbiol. 2020 ;11 572433
    RegX3 Activates whiB3 Under Acid Stress and Subverts Lysosomal Trafficking of Mycobacterium tuberculosis in a WhiB3-Dependent Manner.
    Amar Chandra Mahatha, Soumya Mal, Debayan Majumder, Sudipto Saha, Abhirupa Ghosh, Joyoti Basu, Manikuntala Kundu.
      Two-component systems (TCSs) are central to the ability of Mycobacterium tuberculosis to respond to stress. One such paired TCS is SenX3-RegX3, which responds to phosphate starvation. Here we show that RegX3 is required for M. tuberculosis to withstand low pH, one of the challenges encountered by the bacterium in the host environment, and that RegX3 activates the cytosolic redox sensor WhiB3 to launch an appropriate response to acid stress. We show that the whiB3 promoter of M. tuberculosis harbors a RegX3 binding motif. Electrophoretic mobility shift assays (EMSAs) show that phosphorylated RegX3 (RegX3-P) (but not its unphosphorylated counterpart) binds to this motif, whereas a DNA binding mutant, RegX3 (K204A) fails to do so. Mutation of the putative RegX3 binding motif on the whiB3 promoter, abrogates the binding of RegX3-P. The significance of this binding is established by demonstrating that the expression of whiB3 is significantly attenuated under phosphate starvation or under acid stress in the regX3-inactivated mutant, ΔregX3. Green fluorescent protein (GFP)-based reporter assays further confirm the requirement of RegX3 for the activation of the whiB3 promoter. The compromised survival of ΔregX3 under acid stress and its increased trafficking to the lysosomal compartment are reversed upon complementation with either regX3 or whiB3, suggesting that RegX3 exerts its effects in a WhiB3-dependent manner. Finally, using an in vitro granuloma model, we show that granuloma formation is compromised in the absence of regX3, but restored upon complementation with either regX3 or whiB3. Our findings provide insight into an important role of RegX3 in the network that regulates the survival of M. tuberculosis under acid stress similar to that encountered in its intracellular niche. Our results argue strongly in favor of a role of the RegX3-WhiB3 axis in establishment of M. tuberculosis infection.
    Keywords:  Mycobacterium tuberculosis; acid stress; gene expression; granuloma formation; lysosomal trafficking; two-component systems
    DOI:  https://doi.org/10.3389/fmicb.2020.572433
  19. Rev Prat. 2020 May;70(5): 537-540
    [Fabry disease].
    Benjamin Subran, Clémence Montagner, Jonathan London, Olivier Lidove, Wladimir Mauhin.
      Fabry disease. Fabry disease is an X-linked disorder in which lysosomal alpha-galactosidase A is lacking, leading to enzyme-substrate accumulation and tissues dysfunction. Acroparesthesia, angiokeratoma, familial nephropathy or hypertrophic cardiomyopathy should suggest Fabry disease. Enzymatic assay allows diagnosis in men but genetic assay is needed for women. Enzyme replacement therapy is available since 2001 and a pharmacologic chaperone since 2016.
    Keywords:  Fabry disease
  20. Am J Physiol Cell Physiol. 2020 Oct 14.
    mTORC1/2 signaling is downregulated by amino acid-free culture of mouse preimplantation embryos and is only partially restored by amino acid re-addition.
    Radu C Zamfirescu, Margot L Day, Michael B Morris.
      Development of the mammalian preimplantation embryo is influenced by autocrine/paracrine factors and availability of nutrients. Deficiencies of these during in vitro culture reduce the success of assisted reproductive technologies. The mTORC1 pathway integrates external and internal signals, including those by amino acids (AAs), to promote normal preimplantation development. For this reason, AAs are often included in embryo culture media. In this study, we examined how withdrawal and addition of AAs to culture media modulate mTORC1 pathway activity compared to its activity in mouse embryos developed in vivo. Phosphorylation of signalling components downstream of mTORC1, namely p70S6K, RPS6 and 4E-BP1, and that of Akt, which lies upstream of mTORC1, changed significantly across stages of embryos developed in vivo. For freshly isolated blastocysts placed in vitro, the absence of AAs in culture medium, even for a few hours, decreased mTORC1 signalling, which could only be partially restored by their addition. Long-term culture of early embryos to blastocysts in the absence of AAs decreased mTORC1 signalling to a greater extent and again this could only be partially restored by their inclusion. This failure to fully restore is probably due to decreased PI3K/Akt/mTORC2 signalling in culture, as indicated by decreased P-AktS473. mTORC2 lies upstream of mTORC1 and is insensitive to AAs, and its reduced activity probably results from loss of maternal/autocrine factors. These data highlight reduced mTORC1/2 signalling activity correlating with compromised development in vitro and show that addition of AAs can only partially offset these effects.
    Keywords:  Akt; Preimplantation embryo; amino acids; mTOR; proline
    DOI:  https://doi.org/10.1152/ajpcell.00385.2020
  21. Int J Neurosci. 2020 Oct 12. 1-15
    Body composition and 6 minute walking ability in late-onset Pompe disease patients after 9 years of enzyme replacement therapy.
    Gerasimos Terzis, Georgios Papadimas, Argyro Krase, Eleni Kontou, Ioannis Arnaoutis, Constantinos Papadopoulos.
      Pompe disease is a rare autosomal recessive disorder caused by the deficiency of acid α-glycosidase resulting in accumulation of glycogen in the lysosomes. The late-onset form of the disease (LOPD) causes primarily progressive muscle weakness and respiratory insufficiency. Enzyme replacement therapy (ERT) introduced in 2006, showed mild improvement or stabilization of the symptoms although long-term data are limited. Aim of the study was to describe the progression of body composition and walking ability in LOPD patients receiving ERT consistently for 9 years. Lean body mass, bone mineral density, body fat and 6 minute walking distance were assessed in three male and three female LOPD patients (height 165.8 ± 11.2cm, age 42.3 ± 11.8yrs, body mass 71.1 ± 20.8kg, at study entry), every three years, for 9 years since ERT initiation (T0, T3, T6, T9). Total body and upper extremities' lean mass remained unchanged (P < 0.05), but it was decreased for the lower extremities (T3:13.06 ± 3.848kg vs. T9:11.63 ± 3.49kg, P < 0.05). Lean body mass was not significantly different after 9 years of ERT compared to before the ERT initiation (T0 to T9). Bone mineral density remained unchanged. Percent body fat increased (T0:39.1 ± 10.3%, vs. T9:43.1 ± 10.4%, P < 0.05). Six minute walking distance tended to increase after 3 years of ERT and decreased gradually thereafter, with no difference between T0-T9. Lean mass of the lower extremities adjusted for body weight was significantly correlated with 6 minute walking distance (r = 0.712, P < 0.05). The current data show that enzyme replacement therapy may preserve lean body mass, bone mineral density and walking capacity in LOPD patients.
    Keywords:  Lysosomal disease; dual x-ray absorptiometry; functional capacity; neuromuscular disease
    DOI:  https://doi.org/10.1080/00207454.2020.1835902
  22. Ann Palliat Med. 2020 Sep 27. pii: apm-19-635. [Epub ahead of print]
    A late-onset male Fabry disease patient with somatic mosaicism of a classical GLA mutation: a case report.
    Eun Hui Bae, Jong Moon Choi, Chang Seok Ki, Seong Kwon Ma, Han-Wook Yoo, Soo Wan Kim.
      Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene (GLA). Male patients of FD develop early sign and symptoms in childhood or adolescence. However, "de novo somatic mosaicism" is rare and might be developed a relatively mild phenotype despite carrying a classic type. A 34-year-old male patient visited with foamy urine. Renal biopsy findings were consistent with FD. Leukocyte α-galactosidase activity was markedly reduced at 5.3 nmol/hr/mg (normal range, 25-126). Sequence analysis of the patient's GLA gene identified mosaicism for the mutation GLA[NM_000169.2] c.820=/G>C. This mutation results in a substitution of the amino acid in position 274 from glycine to arginine. However, no family members showed FD-related symptoms, and the daughter of the patient was also tested for paternity and was identified as a real biological daughter, but DNA sequence analysis for FD showed no mutations. Based on these results, we diagnosed the patients as de novo mutation with somatic mosaicism. Next generation sequencing turned out that 58% of the readings had the mutated allele in buccal cells, 84% in blood, and 85% in urine, when 100% should be expected in a hemizygous affected male confirming the presence of somatic mosaicisms. The patient has been on treatment for enzyme replacement therapy (agalsidase-β, 1.0 mg/kg biweekly) for past 9 years and has maintained normal renal function (serum creatinine 1.0 mg/dL) with mild albuminuria (123 mg/g Cr). Therefore, this case suggests somatic mosaicism is one of important phenotype modifiers.
    Keywords:  De novo mutation; Fabry disease; Somatic mosaicism; case report; next generation sequencing; α-galactosidase A, GLA gene
    DOI:  https://doi.org/10.21037/apm-19-635
  23. Mov Disord Clin Pract. 2020 Oct;7(7): 834-837
    Parkinsonism in Patients with Neuronopathic (Type 3) Gaucher Disease: A Case Series.
    Emory Ryan, Dominick Amato, Jennifer J MacKenzie, Ellen Sidransky, Grisel Lopez.
      Background: The link between Parkinson's disease (PD), the second most common neurodegenerative disorder, and nonneuronopathic Gaucher disease (GD) is well established. Currently, PD is primarily associated with nonneuronopathic GD; however, with currently available treatments, patients with chronic neuronopathic GD, who historically had a shortened life span, are now living well into their 50s and beyond.Cases: We highlight 4 patients with chronic neuronopathic GD with parkinsonian features, describing their GD genotype and phenotype as well as the presentation and progression of their parkinsonism. Symptoms presented in their fourth or fifth decade of life, and include unilateral bradykinesia and/or tremor. Of the patients, 3 had cognitive impairment. The fourth patient has not shown cognitive decline 6 years after PD onset.
    Conclusion: This small series highlights that PD is not exclusively associated with nonneuronopathic GD and that as the chronic neuronopathic GD population ages, the clinical spectrum and heterogeneity of neurological manifestations may include parkinsonism.
    Keywords:  lysosomal storage disorders, GBA1, neurodegeneration, Parkinson's disease
    DOI:  https://doi.org/10.1002/mdc3.13031
  24. Eur Respir Rev. 2020 Sep 30. pii: 200269. [Epub ahead of print]29(157):
    The promise of mTOR as a therapeutic target pathway in idiopathic pulmonary fibrosis.
    Manuela Platé, Delphine Guillotin, Rachel C Chambers.
      Idiopathic pulmonary fibrosis (IPF) is characterised by the progressive deposition of excessive extracellular matrix proteins within the lung parenchyma and represents the most rapidly progressive and fatal of all fibrotic conditions. Current anti-fibrotic drugs approved for the treatment of IPF fail to halt disease progression and have significant side-effect profiles. Therefore, there remains a pressing need to develop novel therapeutic strategies for IPF. Mammalian target of rapamycin (mTOR) forms the catalytic subunit of two complexes, mTORC1 and mTORC2. mTORC1 acts as critical cellular sensor which integrates intracellular and extracellular signals to reciprocally regulate a variety of anabolic and catabolic processes. The emerging evidence for a critical role for mTORC1 in influencing extracellular matrix production, metabolism, autophagy and senescence in the setting of IPF highlights this axis as a novel therapeutic target with the potential to impact multiple IPF pathomechanisms.
    DOI:  https://doi.org/10.1183/16000617.0269-2020
  25. Elife. 2020 Oct 15. pii: e58795. [Epub ahead of print]9
    Parallel global profiling of plant TOR dynamics reveals a conserved role for LARP1 in translation.
    M Regina Scarpin, Samuel Leiboff, Jacob Oliver Brunkard.
      TARGET OF RAPAMYCIN (TOR) is a protein kinase that coordinates eukaryotic metabolism. In mammals, TOR specifically promotes translation of ribosomal protein mRNAs when amino acids are available to support protein synthesis. The mechanisms controlling translation downstream from TOR remain contested, however, and are largely unexplored in plants. To define these mechanisms in plants, we globally profiled the plant TOR-regulated transcriptome, translatome, proteome, and phosphoproteome. We found that TOR regulates ribosome biogenesis in plants at multiple levels, but through mechanisms that do not directly depend on 5' oligopyrimidine tract motifs (5'TOPs) found in mammalian ribosomal protein mRNAs. We then show that the TOR-LARP1-5'TOP signaling axis is conserved in plants and regulates expression of a core set of eukaryotic 5'TOP mRNAs, as well as new, plant-specific 5'TOP mRNAs. Our study illuminates ancestral roles of the TOR-LARP1-5'TOP metabolic regulatory network and provides evolutionary context for ongoing debates about the molecular function of LARP1.
    Keywords:  A. thaliana; cell biology; plant biology
    DOI:  https://doi.org/10.7554/eLife.58795
  26. Cells. 2020 Oct 13. pii: E2278. [Epub ahead of print]9(10):
    mTOR Signaling in Metabolism and Cancer.
    Shile Huang.
      The mechanistic/mammalian target of rapamycin (mTOR), a serine/threonine kinase, is a central regulator for human physiological activity. Deregulated mTOR signaling is implicated in a variety of disorders, such as cancer, obesity, diabetes, and neurodegenerative diseases. The papers published in this special issue summarize the current understanding of the mTOR pathway and its role in the regulation of tissue regeneration, regulatory T cell differentiation and function, and different types of cancer including hematologic malignancies, skin, prostate, breast, and head and neck cancer. The findings highlight that targeting the mTOR pathway is a promising strategy to fight against certain human diseases.
    Keywords:  Akt; PI3K; mTOR; photodynamic therapy; regulatory T cells; tissue regeneration; tumor
    DOI:  https://doi.org/10.3390/cells9102278
  27. Endocr Rev. 2020 Oct 14. pii: bnaa026. [Epub ahead of print]
    Amino Acid Sensing in Metabolic Homeostasis and Health.
    Xiaoming Hu, Feifan Guo.
      Sensing and responding to changes in nutrient levels, including those of glucose, lipids and amino acids, by the body is necessary for survival. Accordingly, perturbations in nutrient sensing are tightly linked with human pathologies, particularly metabolic diseases such as obesity, type 2 diabetes mellitus and other complications of metabolic syndromes. The conventional view is that amino acids are fundamental elements for protein and peptide synthesis, while recent studies have revealed that amino acids are also important bioactive molecules that play key roles in signaling pathway and metabolic regulation. Different pathways that sense intracellular and extracellular levels of amino acids are integrated and coordinated at the organismal level, and together, these pathways maintain whole metabolic homeostasis. In this review, we discuss the studies describing how important sensing signals respond to amino acid availability and how these sensing mechanisms modulate metabolic processes, including energy, glucose and lipid metabolism. We further discuss whether dysregulation of amino acid sensing signals can be targeted to promote metabolic disorders, and discuss how to translate these mechanisms to treat human diseases. This review will help to enhance our overall understanding of the correlation between amino acid sensing and metabolic homeostasis, which would be important implications for human health.
    Keywords:  GCN2; amino acids; mTORC1; metabolic homeostasis; sensing signals
    DOI:  https://doi.org/10.1210/endrev/bnaa026
  28. Theranostics. 2020 ;10(24): 11244-11263
    TBC1D15/RAB7-regulated mitochondria-lysosome interaction confers cardioprotection against acute myocardial infarction-induced cardiac injury.
    Wenjun Yu, Shiqun Sun, Haixia Xu, Congye Li, Jun Ren, Yingmei Zhang.
      Rationale: Ischemic heart disease remains a primary threat to human health, while its precise etiopathogenesis is still unclear. TBC domain family member 15 (TBC1D15) is a RAB7 GTPase-activating protein participating in the regulation of mitochondrial dynamics. This study was designed to explore the role of TBC1D15 in acute myocardial infarction (MI)-induced cardiac injury and the possible mechanism(s) involved. Methods: Mitochondria-lysosome interaction was evaluated using transmission electron microscopy and live cell time-lapse imaging. Mitophagy flux was measured by fluorescence and western blotting. Adult mice were transfected with adenoviral TBC1D15 through intra-myocardium injection prior to a 3-day MI procedure. Cardiac morphology and function were evaluated at the levels of whole-heart, cardiomyocytes, intracellular organelles and cell signaling transduction. Results: Our results revealed downregulated level of TBC1D15, reduced systolic function, overt infarct area and myocardial interstitial fibrosis, elevated cardiomyocyte apoptosis and mitochondrial damage 3 days after MI. Overexpression of TBC1D15 restored cardiac systolic function, alleviated infarct area and myocardial interstitial fibrosis, reduced cardiomyocyte apoptosis and mitochondrial damage although TBC1D15 itself did not exert any myocardial effect in the absence of MI. Further examination revealed that 3-day MI-induced accumulation of damaged mitochondria was associated with blockade of mitochondrial clearance because of enlarged defective lysosomes and subsequent interrupted mitophagy flux, which were attenuated by TBC1D15 overexpression. Mechanistic studies showed that 3-day MI provoked abnormal mitochondria-lysosome contacts, leading to lysosomal enlargement and subsequently disabled lysosomal clearance of damaged mitochondria. TBC1D15 loosened the abnormal mitochondria-lysosome contacts through both the Fis1 binding and the RAB7 GAPase-activating domain of TBC1D15, as TBC1D15-dependent beneficial responses were reversed by interference with either of these two domains both in vitro and in vivo. Conclusions: Our findings indicated a pivotal role of TBC1D15 in acute MI-induced cardiac anomalies through Fis1/RAB7 regulated mitochondria-lysosome contacts and subsequent lysosome-dependent mitophagy flux activation, which may provide a new target in the clinical treatment of acute MI.
    Keywords:  Mitochondria-lysosome contacts; Mitophagy flux; Myocardial infarction; RAB7; TBC1D15
    DOI:  https://doi.org/10.7150/thno.46883
  29. Front Neurol. 2020 ;11 1028
    Tuberous Sclerosis Complex as Disease Model for Investigating mTOR-Related Gliopathy During Epileptogenesis.
    Till S Zimmer, Diede W M Broekaart, Victoria-Elisabeth Gruber, Erwin A van Vliet, Angelika Mühlebner, Eleonora Aronica.
      Tuberous sclerosis complex (TSC) represents the prototypic monogenic disorder of the mammalian target of rapamycin (mTOR) pathway dysregulation. It provides the rational mechanistic basis of a direct link between gene mutation and brain pathology (structural and functional abnormalities) associated with a complex clinical phenotype including epilepsy, autism, and intellectual disability. So far, research conducted in TSC has been largely neuron-oriented. However, the neuropathological hallmarks of TSC and other malformations of cortical development also include major morphological and functional changes in glial cells involving astrocytes, oligodendrocytes, NG2 glia, and microglia. These cells and their interglial crosstalk may offer new insights into the common neurobiological mechanisms underlying epilepsy and the complex cognitive and behavioral comorbidities that are characteristic of the spectrum of mTOR-associated neurodevelopmental disorders. This review will focus on the role of glial dysfunction, the interaction between glia related to mTOR hyperactivity, and its contribution to epileptogenesis in TSC. Moreover, we will discuss how understanding glial abnormalities in TSC might give valuable insight into the pathophysiological mechanisms that could help to develop novel therapeutic approaches for TSC or other pathologies characterized by glial dysfunction and acquired mTOR hyperactivation.
    Keywords:  astrocyte; epilepsy; epileptogenesis; glia; mammalian target of rapamycin (mTOR); microglia; oligodendrocyte; tuberous sclerosis (TSC)
    DOI:  https://doi.org/10.3389/fneur.2020.01028
  30. J Biol Chem. 2020 Oct 15. pii: jbc.RA120.014831. [Epub ahead of print]
    Interrogation of kinase genetic interactions provides a global view of PAK1-mediated signal transduction pathways.
    Jae-Hong Kim, Yeojin Seo, Myungjin Jo, Hyejin Jeon, Young-Seop Kim, Eun-Jung Kim, Donggun Seo, Won-Ha Lee, Sang Ryong Kim, Nozomu Yachie, Quan Zhong, Marc Vidal, Frederick P Roth, Kyoungho Suk.
      Kinases are critical components of intracellular signaling pathways and have been extensively investigated in regards to their roles in cancer. p21-activated kinase-1 (PAK1) is a serine/threonine kinase that has been previously implicated in numerous biological processes, such as cell migration, cell cycle progression, cell motility, invasion, and angiogenesis, in glioma and other cancers. However, the signaling network linked to PAK1 is not fully defined. We previously reported a large-scale yeast genetic interaction screen using toxicity as a readout to identify candidate PAK1 genetic interactions. En masse transformation of the PAK1 gene into 4,653 homozygous diploid S. cerevisiae yeast deletion mutants identified approximately 400 candidates that suppressed yeast toxicity. Here we selected 19 candidate PAK1 genetic interactions that had human orthologs and were expressed in glioma for further examination in mammalian cells, brain slice cultures, and orthotopic glioma models. RNAi and pharmacological inhibition of potential PAK1 interactors confirmed that DPP4, KIF11, mTOR, PKM2, SGPP1, TTK, and YWHAE regulate PAK1-induced cell migration, and revealed the importance of genes related to the mitotic spindle, proteolysis, autophagy, and metabolism in PAK1-mediated glioma cell migration, drug resistance, and proliferation. AKT1 was further identified as a downstream mediator of the PAK1-TTK genetic interaction. Taken together, these data provide a global view of PAK1-mediated signal transduction pathways and point to potential new drug targets for glioma therapy.
    Keywords:  PAK1; cell migration; cell proliferation; drug resistance; genetic interaction; glioma; kinase; molecular cell biology; signal transduction
    DOI:  https://doi.org/10.1074/jbc.RA120.014831
  31. Autophagy. 2020 Oct 12. 1-16
    BNIP3L/Nix-induced mitochondrial fission, mitophagy, and impaired myocyte glucose uptake are abrogated by PRKA/PKA phosphorylation.
    Simone C da Silva Rosa, Matthew D Martens, Jared T Field, Lucas Nguyen, Stephanie M Kereliuk, Yan Hai, Donald Chapman, William Diehl-Jones, Michel Aliani, Adrian R West, James Thliveris, Saeid Ghavami, Christof Rampitsch, Vernon W Dolinsky, Joseph W Gordon.
      Lipotoxicity is a form of cellular stress caused by the accumulation of lipids resulting in mitochondrial dysfunction and insulin resistance in muscle. Previously, we demonstrated that the mitophagy receptor BNIP3L/Nix is responsive to lipotoxicity and accumulates in response to a high-fat (HF) feeding. To provide a better understanding of this observation, we undertook gene expression array and shot-gun metabolomics studies in soleus muscle from rodents on an HF diet. Interestingly, we observed a modest reduction in several autophagy-related genes. Moreover, we observed alterations in the fatty acyl composition of cardiolipins and phosphatidic acids. Given the reported roles of these phospholipids and BNIP3L in mitochondrial dynamics, we investigated aberrant mitochondrial turnover as a mechanism of impaired myocyte insulin signaling. In a series of gain-of-function and loss-of-function experiments in rodent and human myotubes, we demonstrate that BNIP3L accumulation triggers mitochondrial depolarization, calcium-dependent activation of DNM1L/DRP1, and mitophagy. In addition, BNIP3L can inhibit insulin signaling through activation of MTOR-RPS6KB/p70S6 kinase inhibition of IRS1, which is contingent on phosphatidic acids and RHEB. Finally, we demonstrate that BNIP3L-induced mitophagy and impaired glucose uptake can be reversed by direct phosphorylation of BNIP3L by PRKA/PKA, leading to the translocation of BNIP3L from the mitochondria and sarcoplasmic reticulum to the cytosol. These findings provide insight into the role of BNIP3L, mitochondrial turnover, and impaired myocyte insulin signaling during an overfed state when overall autophagy-related gene expression is reduced. Furthermore, our data suggest a mechanism by which exercise or pharmacological activation of PRKA may overcome myocyte insulin resistance. Abbreviations: BCL2: B cell leukemia/lymphoma 2; BNIP3L/Nix: BCL2/adenovirus E1B interacting protein 3-like; DNM1L/DRP1: dynamin 1-like; FUNDC1: FUN14 domain containing 1; IRS1: insulin receptor substrate 1; MAP1LC3A/LC3: microtubule-associated protein 1 light chain 3 alpha; MFN1: mitofusin 1; MFN2: mitofusin 2; MTOR: mechanistic target of rapamycin kinase; OPA1: OPA1 mitochondrial dynamin like GTPase; PDE4i: phosphodiesterase 4 inhibitor; PLD1: phospholipase D1; PLD6: phospholipase D family member 6; PRKA/PKA: protein kinase, AMP-activated; PRKCD/PKCδ: protein kinase C, delta; PRKCQ/PKCθ: protein kinase C, theta; RHEB: Ras homolog enriched in brain; RPS6KB/p70S6K: ribosomal protein S6 kinase; SQSTM1/p62: sequestosome 1; YWHAB/14-3-3β: tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein beta.
    Keywords:  Insulin signaling; MTOR; Nix; PKA; mitochondria; mitophagy; muscle
    DOI:  https://doi.org/10.1080/15548627.2020.1821548
  32. Front Cell Infect Microbiol. 2020 ;10 461
    Mycobacterium tuberculosis Calcium Pump CtpF Modulates the Autophagosome in an mTOR-Dependent Manner.
    Rajni Garg, Salik Miskat Borbora, Harsh Bansia, Sandhya Rao, Prakruti Singh, Rinkee Verma, Kithiganahalli Narayanaswamy Balaji, Valakunja Nagaraja.
      Calcium is a very important second messenger, whose concentration in various cellular compartments is under tight regulation. A disturbance in the levels of calcium in these compartments can play havoc in the cell, as it regulates various cellular processes by direct or indirect mechanisms. Here, we have investigated the functional importance of a calcium transporting P2A ATPase, CtpF of Mycobacterium tuberculosis (Mtb) in the pathogen's interaction with the host. Among its uncanny ways of dealing with the host with umpteen strategies for survival and persistence in humans, CtpF is identified as a new player. The levels of ctpF are upregulated in macrophage stresses like hypoxia, high nitric oxide levels and acidic pH. Using confocal microscopy and fluorimetry, we show that CtpF effluxes calcium in macrophages in early stages of Mtb infection. Downregulation of ctpF expression by conditional knockdown resulted in perturbation of host calcium levels and consequent decreased activation of mTOR. We present a mechanism how calcium efflux by the pathogen inhibits mTOR-dependent autophagy and enhances bacterial survival. Our work highlights how Mtb engages its metal efflux pumps to exploit host autophagic process for its proliferation.
    Keywords:  CtpF; Mycobacterium tuberculosis; autophagy; calcium; mTOR; tuberculosis
    DOI:  https://doi.org/10.3389/fcimb.2020.00461
  33. Cell. 2020 Oct 13. pii: S0092-8674(20)31158-2. [Epub ahead of print]
    A MicroRNA Linking Human Positive Selection and Metabolic Disorders.
    Lifeng Wang, Nasa Sinnott-Armstrong, Alexandre Wagschal, Abigail R Wark, Joao-Paulo Camporez, Rachel J Perry, Fei Ji, Yoojin Sohn, Justin Oh, Su Wu, Jessica Chery, Bahareh Nemati Moud, Alham Saadat, Simon N Dankel, Gunnar Mellgren, Divya Sri Priyanka Tallapragada, Sophie Madlen Strobel, Mi-Jeong Lee, Ryan Tewhey, Pardis C Sabeti, Anne Schaefer, Andreas Petri, Sakari Kauppinen, Raymond T Chung, Alexander Soukas, Joseph Avruch, Susan K Fried, Hans Hauner, Ruslan I Sadreyev, Gerald I Shulman, Melina Claussnitzer, Anders M Näär.
      Positive selection in Europeans at the 2q21.3 locus harboring the lactase gene has been attributed to selection for the ability of adults to digest milk to survive famine in ancient times. However, the 2q21.3 locus is also associated with obesity and type 2 diabetes in humans, raising the possibility that additional genetic elements in the locus may have contributed to evolutionary adaptation to famine by promoting energy storage, but which now confer susceptibility to metabolic diseases. We show here that the miR-128-1 microRNA, located at the center of the positively selected locus, represents a crucial metabolic regulator in mammals. Antisense targeting and genetic ablation of miR-128-1 in mouse metabolic disease models result in increased energy expenditure and amelioration of high-fat-diet-induced obesity and markedly improved glucose tolerance. A thrifty phenotype connected to miR-128-1-dependent energy storage may link ancient adaptation to famine and modern metabolic maladaptation associated with nutritional overabundance.
    DOI:  https://doi.org/10.1016/j.cell.2020.09.017
  34. Cancers (Basel). 2020 Oct 14. pii: E2972. [Epub ahead of print]12(10):
    Therapeutic Potential of PI3K/AKT/mTOR Pathway in Gastrointestinal Stromal Tumors: Rationale and Progress.
    Yi Duan, Johannes Haybaeck, Zhihui Yang.
      Gastrointestinal stromal tumor (GIST) originates from interstitial cells of Cajal (ICCs) in the myenteric plexus of the gastrointestinal tract. Most GISTs arise due to mutations of KIT and PDGFRA gene activation, encoding the receptor tyrosine kinase (RTK). The clinical use of the RTK inhibitor imatinib has significantly improved the management of GIST patients; however, imatinib resistance remains a challenge. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is a critical survival pathway for cell proliferation, apoptosis, autophagy and translation in neoplasms. Constitutive autophosphorylation of RTKs has an impact on the activation of the PI3K/AKT/mTOR pathway. In several preclinical and early-stage clinical trials PI3K/AKT/mTOR signaling inhibition has been considered as a promising targeted therapy strategy for GISTs. Various inhibitory drugs targeting different parts of the PI3K/AKT/mTOR pathway are currently being investigated in phase I and phase II clinical trials. This review highlights the progress for PI3K/AKT/mTOR-dependent mechanisms in GISTs, and explores the relationship between mTOR downstream signals, in particular, eukaryotic initiation factors (eIFs) and the development of GISTs, which may be instrumental for identifying novel therapeutic targets.
    Keywords:  PI3K/AKT/mTOR; eIFs; gastrointestinal stromal tumors; inhibitor
    DOI:  https://doi.org/10.3390/cancers12102972
  35. PLoS Genet. 2020 Oct 16. 16(10): e1009046
    The Ccr4-Not complex regulates TORC1 signaling and mitochondrial metabolism by promoting vacuole V-ATPase activity.
    Hongfeng Chen, P Winston Miller, Daniel L Johnson, R Nicholas Laribee.
      The Ccr4-Not complex functions as an effector of multiple signaling pathways that control gene transcription and mRNA turnover. Consequently, Ccr4-Not contributes to a diverse array of processes, which includes a significant role in cell metabolism. Yet a mechanistic understanding of how it contributes to metabolism is lacking. Herein, we provide evidence that Ccr4-Not activates nutrient signaling through the essential target of rapamycin complex 1 (TORC1) pathway. Ccr4-Not disruption reduces global TORC1 signaling, and it also upregulates expression of the cell wall integrity (CWI) pathway terminal kinase Mpk1. Although CWI signaling represses TORC1 signaling, we find that Ccr4-Not loss inhibits TORC1 independently of CWI activation. Instead, we demonstrate that Ccr4-Not promotes the function of the vacuole V-ATPase, which interacts with the Gtr1 GTPase-containing EGO complex to stimulate TORC1 in response to nutrient sufficiency. Bypassing the V-ATPase requirement in TORC1 activation using a constitutively active Gtr1 mutant fully restores TORC1 signaling in Ccr4-Not deficient cells. Transcriptome analysis and functional studies revealed that loss of the Ccr4 subunit activates the TORC1 repressed retrograde signaling pathway to upregulate mitochondrial activity. Blocking this mitochondrial upregulation in Ccr4-Not deficient cells further represses TORC1 signaling, and it causes synergistic deficiencies in mitochondrial-dependent metabolism. These data support a model whereby Ccr4-Not loss impairs V-ATPase dependent TORC1 activation that forces cells to enhance mitochondrial metabolism to sustain a minimal level of TORC1 signaling necessary for cell growth and proliferation. Therefore, Ccr4-Not plays an integral role in nutrient signaling and cell metabolism by promoting V-ATPase dependent TORC1 activation.
    DOI:  https://doi.org/10.1371/journal.pgen.1009046
  36. High Blood Press Cardiovasc Prev. 2020 Oct 12.
    The role of Immunity in Fabry Disease and Hypertension: A Review of a Novel Common Pathway.
    Rita Del Pinto, Claudio Ferri.
      Fabry disease is a progressive, X-linked inherited lysosomal storage disorder where accumulation of glycosphingolipids increases the risk for early cardiovascular complications, including heart failure, stroke, and end stage renal disease. Besides disease-specific therapy, blood pressure (BP) control is of central importance in Fabry disease to reduce disease progression and improve prognosis. Both Fabry disease and hypertension are characterized by the activation of the innate component of the immune system, with Toll-like receptor 4 (TLR4) as a common trigger to the inflammatory cascade. The renin-angiotensin system (RAS) participates in the establishment of low-grade chronic inflammation and redox unbalance that contribute to organ damage in the long term. Besides exploiting the anti-inflammatory effects of RAS blockade and enzyme replacement therapy, targeted therapies acting on the immune system represent an appealing field of research in these conditions. The aim of this narrative review is to examine the issue of hypertension in the setting of Fabry disease, focusing on the possible determinants of their reciprocal relationship, as well as on the related clinical and therapeutic implications.
    Keywords:  Fabry disease; Hypertension; Immune system; Inflammation; Oxidative stress; Renin-angiotensin system
    DOI:  https://doi.org/10.1007/s40292-020-00414-w
  37. Mol Ther. 2020 Sep 30. pii: S1525-0016(20)30496-2. [Epub ahead of print]
    A Phase 2/3 Trial of Pabinafusp Alfa, IDS Fused with Anti-Human Transferrin Receptor Antibody, Targeting Neurodegeneration in MPS-II.
    Torayuki Okuyama, Yoshikatsu Eto, Norio Sakai, Kimitoshi Nakamura, Tatsuyoshi Yamamoto, Mariko Yamaoka, Toshiaki Ikeda, Sairei So, Kazunori Tanizawa, Hiroyuki Sonoda, Yuji Sato.
      Pabinafusp alfa (JR-141) is a novel enzyme drug that crosses the blood-brain barrier by transcytosis via transferrin receptors. In order to establish its efficacy and safety, a multicenter, single-arm, open-label phase 2/3 clinical trial was conducted in 28 Japanese patients with mucopolysaccharidosis II (MPS-II, Hunter syndrome) by intravenous administrations of 2.0 mg/kg of pabinafusp alfa for 52 weeks. The primary efficacy endpoint was changes in heparan sulfate (HS) concentrations in the cerebrospinal fluid (CSF). Secondary endpoints included assessments of neurocognitive development for central efficacy, and changes in plasma HS and dermatan sulfate (DS) concentrations for peripheral efficacy. HS concentrations in the CSF significantly decreased from baseline to week 52 (p < 0.001), suggesting continuous inhibition of substrate accumulations in the CNS, i.e., hitherto unaddressed progressive neurodegeneration. Evaluations of neurocognitive developments showed positive changes in 21 of the 28 patients. Serum HS and DS concentrations, liver and spleen volumes, and other assessments suggested the peripheral efficacy of pabinafusp alfa was comparable to that of idursulfase. Drug-related adverse events were mild or moderate in severity, transient, and manageable. The results establish delivery across the BBB of pabinafusp alfa as an effective therapeutic for treating both the CNS and peripheral symptoms of patients with MPS-II.
    Keywords:  Hunter syndrome; anti-human transferrin receptor antibody; blood brain barrier; central nervous system; enzyme-replacement therapy; heparan sulfate; iduronate-2-sulfatase; mucopolysaccharidosis II; neurocognitive development; neurocognitive impairment; neurodegeneration; pabinafusp alfa
    DOI:  https://doi.org/10.1016/j.ymthe.2020.09.039
  38. Biochem Biophys Res Commun. 2020 Oct 12. pii: S0006-291X(20)31442-X. [Epub ahead of print]
    HSP70 interacts with Rheb, inhibiting mTORC1 signaling.
    Hyang Hwa Ryu, Sang Hoon Ha.
      The small GTPase Rheb binds and activates mTORC1, which plays a pivotal role in diverse cellular physiologies. To increase our understanding of how Rheb regulates mTORC1 signaling, we set out to identify Rheb binding proteins using shotgun proteomics approaches. In this study, we characterized HSP70, one of the identified proteins, as a new Rheb binding protein. The present study showed that Rheb forms a complex with HSP70 in intact cells. Interestingly, the binding of Rheb to mTORC1 was abolished by HSP70. Furthermore, the stability of Rheb is dramatically decreased by HSP70, and this degradation is proteasome-dependent. As a result, Rheb-dependent mTORC1 activation was decreased by HSP70. Taken together, HSP70 dissociates Rheb from mTORC1 and induces proteasome-dependent degradation, leading to the inhibition of mTORC1 signaling. Our findings suggest that HSP70 is a negative regulator of mTORC1 signaling via interaction with Rheb.
    Keywords:  HSP70; Negative regulation; Rheb; mTORC1
    DOI:  https://doi.org/10.1016/j.bbrc.2020.07.053
  39. Elife. 2020 Oct 16. pii: e61886. [Epub ahead of print]9
    Modular metabolite assembly in C. elegans depends on carboxylesterases and formation of lysosome-related organelles.
    Henry H Le, Chester Jj Wrobel, Sarah M Cohen, Jingfang Yu, Heenam Park, Maximilian J Helf, Brian J Curtis, Joseph C Kruempel, Pedro Reis Rodrigues, Patrick J Hu, Paul W Sternberg, Frank C Schroeder.
      Signaling molecules derived from attachment of diverse metabolic building blocks to ascarosides play a central role in the life history of C. elegans and other nematodes; however, many aspects of their biogenesis remain unclear. Using comparative metabolomics, we show that a pathway mediating formation of intestinal lysosome-related organelles (LROs) is required for biosynthesis of most modular ascarosides as well as previously undescribed modular glucosides. Similar to modular ascarosides, the modular glucosides are derived from highly selective assembly of moieties from nucleoside, amino acid, neurotransmitter, and lipid metabolism, suggesting that modular glucosides, like the ascarosides, may serve signaling functions. We further show that carboxylesterases that localize to intestinal organelles are required for the assembly of both modular ascarosides and glucosides via ester and amide linkages. Further exploration of LRO function and carboxylesterase homologs in C. elegans and other animals may reveal additional new compound families and signaling paradigms.
    Keywords:  C. elegans; biochemistry; chemical biology
    DOI:  https://doi.org/10.7554/eLife.61886
  40. FEBS Lett. 2020 Oct 16.
    Ciliary localization of folliculin mediated via a kinesin-2-binding motif is required for its functions in mTOR regulation and tumor suppression.
    Yunlong Zhang, Ying Liu, Yu Dai, Yazhe Ren, Guangsen Bao, Bo Ai, Yu Jiang.
      Folliculin (FLCN) is a tumor suppressor protein involved in many cellular processes, including cell signaling, apoptosis and autophagy. In ciliated cells, FLCN localizes to primary cilia and controls mTORC1 signaling in response to flow stress. Here, we show that the ciliary localization of FLCN requires its interaction with kinesin-2, the motor protein for anterograde intraflagellar transport. FLCN binds to kinesin-2 through a loop region in the middle of the protein. Single point mutations within this region of FLCN disrupt its kinesin-2 binding and ciliary entry. The mutants lose the ability to suppress the abnormal mTORC1/2 signaling activities and anchorage-independent growth of FLCN-deficient tumor cells. These observations suggest that ciliary localization of FLCN is essential for its function as a tumor suppressor.
    Keywords:  FLCN; cilium; kinesin-2; mTORC1; mTORC2
    DOI:  https://doi.org/10.1002/1873-3468.13959
  41. RNA Biol. 2020 Oct 15. 1-14
    Translation of Tudor-SN, a novel terminal oligo-pyrimidine (TOP) mRNA, is regulated by the mTORC1 pathway in cardiomyocytes.
    Shihu Gan, Chao Su, Jinzheng Ma, Mingxia Liu, Xiaoteng Cui, Lingbiao Xin, Yuanyuan Ren, Xingjie Gao, Lin Ge, Minxin Wei, Jie Yang.
      The mechanisms that regulate cell-cycle arrest of cardiomyocytes during heart development are largely unknown. We have previously identified Tudor staphylococcal nuclease (Tudor-SN) as a cell-cycle regulator and have shown that its expression level was closely related to cell-proliferation capacity. Herein, we found that Tudor-SN was highly expressed in neonatal mouse myocardia, but it was lowly expressed in that of adults. Using Data Base of Transcription Start Sites (DBTSS), we revealed that Tudor-SN was a terminal oligo-pyrimidine (TOP) mRNA. We further confirmed that the translational efficiency of Tudor-SN mRNA was controlled by the mammalian target of rapamycin complex 1 (mTORC1) pathway, as revealed via inhibition of activated mTORC1 in primary neonatal mouse cardiomyocytes and activation of silenced mTORC1 in adult mouse myocardia; additionally, this result was recapitulated in H9c2 cells. We also demonstrated that the downregulation of Tudor-SN in adult myocardia was due to inactivation of the mTORC1 pathway to ensure that heart growth was in proportion to that of the rest of the body. Moreover, we revealed that Tudor-SN participated in the mTORC1-mediated regulation of cardiomyocytic proliferation, which further elucidated the correlation between Tudor-SN and the mTORC1 pathway. Taken together, our findings suggest that the translational efficiency of Tudor-SN is regulated by the mTORC1 pathway in myocardia and that Tudor-SN is involved in mTORC1-mediated regulation of cardiomyocytic proliferation and cardiac development.
    Keywords:  TOP mRNA; Tudor-SN; cardiomyocytic proliferation; cell cycle arrest; mTORC1; translational efficiency
    DOI:  https://doi.org/10.1080/15476286.2020.1827783
  42. Neurobiol Aging. 2020 Sep 19. pii: S0197-4580(20)30278-5. [Epub ahead of print]96 255-266
    Nucleus distribution of cathepsin B in senescent microglia promotes brain aging through degradation of sirtuins.
    Jie Meng, Yicong Liu, Zhen Xie, Hong Qing, Peng Lei, Junjun Ni.
      Cathepsin B (CatB) leakage from the lysosome into the cytosol in senescent microglia is associated with cognitive impairment. However, whether cellular compartmental translocation of CatB is associated with brain aging remains unclear. In the present study, increased CatB was found in the nucleus of CatB-overexpressed microglia followed by L-leucyl-L-leucine methyl ester, a lysosome-destabilizing reagent, and in the nuclear fraction of the cortex and hippocampus from aged mice. Moreover, CatB enzymatic activity examination showed the nuclear CatB exhibited the proteolytic activity to cleave its specific substrates. The amount of sirtuin1 (Sirt1), Sirt6, Sirt7, and p-Sirt1 was decreased in the cortical lysates from aged mice, in parallel with increased expression of proinflammatory mediators, which were diminished by CatB deficiency. Furthermore, intralateral ventricle administration of microglia overexpressed CatB, and treatment with L-leucyl-L-leucine methyl ester induced cognitive impairment in middle-aged mice. These observations suggest that the increase and nucleus translocation of CatB in senescent microglia were involved in the degradation of nuclear Sirts, which induced proinflammatory responses, resulting in cognition impairment.
    Keywords:  Aging; Microglia; Neuroinflammation; Nucleus translocation; Sirtuins
    DOI:  https://doi.org/10.1016/j.neurobiolaging.2020.09.001
  43. Mol Autism. 2020 Oct 14. 11(1): 78
    Ribosome profiling in mouse hippocampus: plasticity-induced regulation and bidirectional control by TSC2 and FMRP.
    Annie Hien, Gemma Molinaro, Botao Liu, Kimberly M Huber, Joel D Richter.
      BACKGROUND: Mutations in TSC2 are the most common cause of tuberous sclerosis (TSC), a disorder with a high incidence of autism and intellectual disability. TSC2 regulates mRNA translation required for group 1 metabotropic glutamate receptor-dependent synaptic long-term depression (mGluR-LTD) and behavior, but the identity of mRNAs responsive to mGluR-LTD signaling is largely unknown.METHODS: We utilized Tsc2+/- mice as a mouse model of TSC and prepared hippocampal slices from these animals. We induced mGluR-LTD synaptic plasticity in slices and processed the samples for RNA-seq and ribosome profiling to identify differentially expressed genes in Tsc2+/- and following mGluR-LTD synaptic plasticity.
    RESULTS: Ribosome profiling reveals that in Tsc2+/- mouse hippocampal slices, the expression of several mRNAs was dysregulated: terminal oligopyrimidine (TOP)-containing mRNAs decreased, while FMRP-binding targets increased. Remarkably, we observed the opposite changes of FMRP binding targets in Fmr1-/y hippocampi. In wild-type hippocampus, induction of mGluR-LTD caused rapid changes in the steady-state levels of hundreds of mRNAs, many of which are FMRP targets. Moreover, mGluR-LTD failed to promote phosphorylation of eukaryotic elongation factor 2 (eEF2) in TSC mice, and chemically mimicking phospho-eEF2 with low cycloheximide enhances mGluR-LTD in TSC mice.
    CONCLUSION: These results suggest a molecular basis for bidirectional regulation of synaptic plasticity and behavior by TSC2 and FMRP. Our study also suggests that altered mGluR-regulated translation elongation contributes to impaired synaptic plasticity in Tsc2+/- mice.
    DOI:  https://doi.org/10.1186/s13229-020-00384-9
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