bims-lysosi Biomed News
on Lysosomes and signaling
Issue of 2020‒11‒01
forty-one papers selected by
Stephanie Fernandes
Max Planck Institute for Biology of Ageing


  1. J Clin Invest. 2020 Oct 29. pii: 135124. [Epub ahead of print]
    McGrath MJ, Eramo MJ, Gurung R, Sriratana A, Gehrig SM, Lynch GS, Lourdes SR, Koentgen F, Feeney SJ, Lazarou M, McLean CA, Mitchell CA.
      The regulation of autophagy-dependent lysosome homeostasis in vivo is unclear. We show the inositol polyphosphate 5-phosphatase INPP5K regulates autophagic lysosome reformation (ALR), a lysosome recycling pathway, in muscle. INPP5K hydrolyses phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) to phosphatidylinositol 4-phosphate (PI(4)P) and INPP5K mutations cause muscular dystrophy by unknown mechanisms. We report loss of INPP5K in muscle causes severe disease, autophagy inhibition and lysosome depletion. Reduced PI(4,5)P2 turnover on autolysosomes in Inpp5k-/- muscle suppresses autophagy and lysosome repopulation via ALR inhibition. Defective ALR in Inpp5k-/- myoblasts was characterised by enlarged autolysosomes and the persistence of hyperextended reformation tubules, structures that participate in membrane-recycling to form lysosomes. Reduced disengagement of the PI(4,5)P2 effector clathrin was observed on reformation tubules which we propose interferes with ALR completion. Inhibition of PI(4,5)P2 synthesis, or expression of wild-type, but not INPP5K-disease mutants in INPP5K-depleted myoblasts restored lysosomal homeostasis. Therefore, bidirectional interconversion of PI(4)P/PI(4,5)P2 on autolysosomes is integral to lysosome replenishment and autophagy function in muscle. Activation of TFEB-dependent de novo lysosome biogenesis did not compensate for loss of ALR in Inpp5k-/- muscle, revealing a dependence on this lysosome recycling pathway. Therefore, in muscle, ALR is indispensable for lysosome homeostasis during autophagy and when defective is associated with muscular dystrophy.
    Keywords:  Autophagy; Cell Biology; Lysosomes; Muscle Biology; Skeletal muscle
    DOI:  https://doi.org/10.1172/JCI135124
  2. Cell Death Differ. 2020 Oct 25.
    Chen X, Guan Y, Zhang Y, Jia Y, Li W, Guo C, Li Y, Wang X, Shi Y, Wang Q, Zhu F, Li Y, Zhang L.
      Transcription factor EB (TFEB) is a master regulator of autophagy and lysosomal biogenesis. The post-translational phosphorylation modulations of TFEB by mTOR and ERK signaling can determine its nucleocytoplasmic shuttling and activity in response to nutrient availability. However, regulations of TFEB at translational level are rarely known. Here, we found that programmed cell death 4 (PDCD4), a tumor suppressor, decreased levels of nuclear TFEB to inhibit lysosome biogenesis and function. Mechanistically, PDCD4 reduces global pool of TFEB by suppressing TFEB translation in an eIF4A-dependent manner, rather than influencing mTOR- and ERK2-dependnet TFEB nucleocytoplasmic shuttling. Both of MA3 domains within PDCD4 are required for TFEB translation inhibition. Furthermore, TFEB is required for PDCD4-mediated lysosomal function suppression. In the tumor microenvironment, PDCD4 deficiency promotes the anti-tumor effect of macrophage via enhancing TFEB expression. Our research reveals a novel PDCD4-dependent TFEB translational regulation and supports PDCD4 as a potential therapeutic target for lysosome dysfunction related diseases.
    DOI:  https://doi.org/10.1038/s41418-020-00646-2
  3. Autophagy. 2020 Oct 28. 1-16
    Xu T, Nicolson S, Sandow JJ, Dayan S, Jiang X, Manning JA, Webb AI, Kumar S, Denton D.
      Macroautophagy/autophagy is a highly conserved lysosomal degradative pathway important for maintaining cellular homeostasis. Much of our current knowledge of autophagy is focused on the initiation steps in this process. Recently, an understanding of later steps, particularly lysosomal fusion leading to autolysosome formation and the subsequent role of lysosomal enzymes in degradation and recycling, is becoming evident. Autophagy can function in both cell survival and cell death, however, the mechanisms that distinguish adaptive/survival autophagy from autophagy-dependent cell death remain to be established. Here, using proteomic analysis of Drosophila larval midguts during degradation, we identify a group of proteins with peptidase activity, suggesting a role in autophagy-dependent cell death. We show that Cp1/cathepsin L-deficient larval midgut cells accumulate aberrant autophagic vesicles due to a block in autophagic flux, yet later stages of midgut degradation are not compromised. The accumulation of large aberrant autolysosomes in the absence of Cp1 appears to be the consequence of decreased degradative capacity as they contain undigested cytoplasmic material, rather than a defect in autophagosome-lysosome fusion. Finally, we find that other cathepsins may also contribute to proper autolysosomal degradation in Drosophila larval midgut cells. Our findings provide evidence that cathepsins play an essential role in the autolysosome to maintain basal autophagy flux by balancing autophagosome production and turnover.
    Keywords:   Drosophila ; Autophagy; cell death; lysosome; midgut; proteome
    DOI:  https://doi.org/10.1080/15548627.2020.1838105
  4. Mol Cell. 2020 Oct 15. pii: S1097-2765(20)30686-9. [Epub ahead of print]
    Lees JA, Li P, Kumar N, Weisman LS, Reinisch KM.
      The phosphoinositide PI(3,5)P2, generated exclusively by the PIKfyve lipid kinase complex, is key for lysosomal biology. Here, we explore how PI(3,5)P2 levels within cells are regulated. We find the PIKfyve complex comprises five copies of the scaffolding protein Vac14 and one copy each of the lipid kinase PIKfyve, generating PI(3,5)P2 from PI3P and the lipid phosphatase Fig4, reversing the reaction. Fig4 is active as a lipid phosphatase in the ternary complex, whereas PIKfyve within the complex cannot access membrane-incorporated phosphoinositides due to steric constraints. We find further that the phosphoinositide-directed activities of both PIKfyve and Fig4 are regulated by protein-directed activities within the complex. PIKfyve autophosphorylation represses its lipid kinase activity and stimulates Fig4 lipid phosphatase activity. Further, Fig4 is also a protein phosphatase acting on PIKfyve to stimulate its lipid kinase activity, explaining why catalytically active Fig4 is required for maximal PI(3,5)P2 production by PIKfyve in vivo.
    Keywords:  lipid kinase; lipid phosphatase; phosphoinositide homeostasis
    DOI:  https://doi.org/10.1016/j.molcel.2020.10.003
  5. Autophagy. 2020 Oct 28.
    Zhang X, Wei M, Fan J, Yan W, Zha X, Song H, Wan R, Yin Y, Wang W.
      Macroautophagy/autophagy is vital for neuronal homeostasis and functions. Accumulating evidence suggest that autophagy is impaired during cerebral ischemia, contributing to neuronal dysfunction and neurodegeneration. However, the outcomes after transient modification in autophagy machinery are not fully understood. This study investigated the effects of ischemic stress on autophagy and synaptic structures using a rat model of oxygen-glucose deprivation (OGD) in hippocampal neurons and a mouse model of middle cerebral artery occlusion (MCAO). Upon acute ischemia, an initial autophagy modification occurred in an upregulation manner. Following, the number of lysosomes increased, as well as lysosomal volume, indicating dysfunctional lysosomal storage. These changes were prevented by inhibiting autophagy via 3-methyladenine (3-MA) treatment or ATG7 (autophagy related 7) knockdown, or were mimicked by rapamycin (RAPA), a known activator of autophagy. This suggests that dysfunctional lysosomal storage is associated with the early burst of autophagy. Dysfunctional lysosomal storage contributed to autophagy dysfunction because the basal level of MTOR-dependent lysosomal biogenesis in the reperfusion was not sufficient to clear undegraded cargoes after transient autophagy upregulation. Further investigation revealed that impairment of synaptic ultra-structures, accompanied by dysfunctional lysosomal storage, may result from a failure in dynamic turnover of synaptic proteins. This indicates a vital role of autophagy-lysosomal machinery in the maintenance of synaptic structures. This study supports previous evidence that dysfunctional lysosomal storage may occur following the upregulation of autophagy in neurons. Appropriate autophagosome-lysosomal functioning is vital for maintenance of neuronal synaptic function and impacts more than the few known synaptic proteins.
    Keywords:  functional lysosomal storage; lysosomal-associated membrane protein 1 (LAMP1); lysosome; middle cerebral artery occlusion (MCAO); neurons; oxygen-glucose deprivation (OGD); synaptic plasticity
    DOI:  https://doi.org/10.1080/15548627.2020.1840796
  6. Am J Med Genet C Semin Med Genet. 2020 Oct 27.
    Espejo-Mojica AJ, Rodríguez-López A, Li R, Zheng W, Alméciga-Díaz CJ, Dulcey-Sepúlveda C, Combariza G, Barrera LA.
      GM2 gangliosidosis, Tay-Sachs and Sandhoff diseases, are lysosomal storage disorders characterized by the lysosomal accumulation of GM2 gangliosides. This accumulation is due to deficiency in the activity of the β-hexosaminidases Hex-A or Hex-B, which are dimeric hydrolases formed by αβ or ββ subunits, respectively. These disorders show similar clinical manifestations that range from mild systemic symptoms to neurological damage and premature death. There is still no effective therapy for GM2 gangliosidoses, but some therapeutic alternatives, as enzyme replacement therapy, have being evaluated. Previously, we reported the production of active human recombinant β-hexosaminidases (rhHex-A and rhHex-B) in the methylotrophic yeast Pichia pastoris. In this study, we evaluated in vitro the cellular uptake, intracellular delivery to lysosome, and reduction of stored substrates. Both enzymes were taken-up via endocytic pathway mediated by mannose and mannose-6-phosphate receptors and delivered to lysosomes. Noteworthy, rhHex-A diminished the levels of stored lipids and lysosome mass in fibroblasts from Tay-Sachs patients. Overall, these results confirm the potential of P. pastoris as host to produce recombinant β-hexosaminidases intended to be used in the treatment of GM2 gangliosidosis.
    Keywords:  GM2 gangliosidosis; Pichia pastoris; enzyme replacement therapy; recombinant hexosaminidases
    DOI:  https://doi.org/10.1002/ajmg.c.31849
  7. Int J Mol Sci. 2020 Oct 22. pii: E7819. [Epub ahead of print]21(21):
    Benetó N, Vilageliu L, Grinberg D, Canals I.
      Sanfilippo syndrome or mucopolysaccharidosis III is a lysosomal storage disorder caused by mutations in genes responsible for the degradation of heparan sulfate, a glycosaminoglycan located in the extracellular membrane. Undegraded heparan sulfate molecules accumulate within lysosomes leading to cellular dysfunction and pathology in several organs, with severe central nervous system degeneration as the main phenotypical feature. The exact molecular and cellular mechanisms by which impaired degradation and storage lead to cellular dysfunction and neuronal degeneration are still not fully understood. Here, we compile the knowledge on this issue and review all available animal and cellular models that can be used to contribute to increase our understanding of Sanfilippo syndrome disease mechanisms. Moreover, we provide an update in advances regarding the different and most successful therapeutic approaches that are currently under study to treat Sanfilippo syndrome patients and discuss the potential of new tools such as induced pluripotent stem cells to be used for disease modeling and therapy development.
    Keywords:  Sanfilippo syndrome; animal models; cellular models; heparan sulfate; induced pluripotent stem cells; lysosomal storage disorders; mucopolysaccharidosis III; therapeutic approaches
    DOI:  https://doi.org/10.3390/ijms21217819
  8. Cell Death Differ. 2020 Oct 27.
    Cho JH, Kim K, Kim SA, Park S, Park BO, Kim JH, Kim SY, Kwon MJ, Han MH, Lee SB, Park BC, Park SG, Kim JH, Kim S.
      The mammalian Target of Rapamycin (mTOR) pathway regulates a variety of physiological processes, including cell growth and cancer progression. The regulatory mechanisms of these signals are extremely complex and comprise many feedback loops. Here, we identified the deubiquitinating enzyme ovarian tumor domain-containing protein 5 (OTUD5) as a novel positive regulator of the mTOR complex (mTORC) 1 and 2 signaling pathways. We demonstrated that OTUD5 stabilized β-transducin repeat-containing protein 1 (βTrCP1) proteins via its deubiquitinase (DUB) activity, leading to the degradation of Disheveled, Egl-10, and pleckstrin domain-containing mTOR-interacting protein (DEPTOR), which is an inhibitory protein of mTORC1 and 2. We also showed that mTOR directly phosphorylated OTUD5 and activated its DUB activity. RNA sequencing analysis revealed that OTUD5 regulates the downstream gene expression of mTOR. Additionally, OTUD5 depletion elicited several mTOR-related phenotypes such as decreased cell size and increased autophagy in mammalian cells as well as the suppression of a dRheb-induced curled wing phenotype by RNA interference of Duba, a fly ortholog of OTUD5, in Drosophila melanogaster. Furthermore, OTUD5 knockdown inhibited the proliferation of the cancer cell lines with mutations activating mTOR pathway. Our results suggested a positive feedback loop between OTUD5 and mTOR signaling pathway.
    DOI:  https://doi.org/10.1038/s41418-020-00649-z
  9. J Bone Miner Res. 2020 Oct 30.
    Di Zanni E, Palagano E, Lagostena L, Strina D, Rehman A, Abinun M, De Somer L, Martire B, Brown J, Kariminejad A, Balasubramanian S, Baynam G, Gurrieri F, Pisanti MA, De Maggio I, Abboud MR, Chiesa R, Burren CP, Villa A, Sobacchi C, Picollo A.
      ClC-7 is a chloride-proton antiporter of the CLC protein family. In complex with its accessory protein Ostm-1, ClC-7 localizes to lysosomes and to the osteoclasts' ruffled border, where it plays a critical role in acidifying the resorption lacuna during bone resorption. Gene inactivation in mice causes severe osteopetrosis, neurodegeneration and lysosomal storage disease. Mutations in the human CLCN7 gene are associated with diverse forms of osteopetrosis. The functional evaluation of ClC-7 variants might be informative with respect to their pathogenicity, but the cellular localization of the protein hampers this analysis. Here we investigated the functional effects of thirteen CLCN7 mutations identified in thirteen new patients with severe or mild osteopetrosis, and a known ADO2 mutation. We mapped the mutated amino acid residues in the homology model of ClC-7 protein, assessed the lysosomal co-localization of ClC-7 mutants and Ostm1 through confocal microscopy, and performed patch-clamp recordings on plasma-membrane-targeted mutant ClC-7. Finally, we analyzed these results together with the patients' clinical features and suggested a correlation between the lack of ClC-7/Ostm1 in lysosomes and severe neurodegeneration.
    Keywords:  chloride-proton exchanger; lysosomal localization; missense mutations; osteoclast; osteopetrosis
    DOI:  https://doi.org/10.1002/jbmr.4200
  10. Biochem J. 2020 Oct 30. 477(20): 3963-3983
    Lübke T, Damme M.
      Sulfatases constitute a family of enzymes that specifically act in the hydrolytic degradation of sulfated metabolites by removing sulfate monoesters from various substrates, particularly glycolipids and glycosaminoglycans. A common essential feature of all known eukaryotic sulfatases is the posttranslational modification of a critical cysteine residue in their active site by oxidation to formylglycine (FGly), which is mediated by the FGly-generating enzyme in the endoplasmic reticulum and is indispensable for catalytic activity. The majority of the so far described sulfatases localize intracellularly to lysosomes, where they act in different catabolic pathways. Mutations in genes coding for lysosomal sulfatases lead to an accumulation of the sulfated substrates in lysosomes, resulting in impaired cellular function and multisystemic disorders presenting as lysosomal storage diseases, which also cover the mucopolysaccharidoses and metachromatic leukodystrophy. Bioinformatics analysis of the eukaryotic genomes revealed, besides the well described and long known disease-associated sulfatases, additional genes coding for putative enzymes with sulfatases activity, including arylsulfatase G as well as the arylsulfatases H, I, J and K, respectively. In this article, we review current knowledge about lysosomal sulfatases with a special focus on the just recently characterized family members arylsulfatase G and arylsulfatase K.
    Keywords:  formyl glycine-generating enzyme; glycosaminoglycans; lysosomal storage disease; lysosomes; mucopolysaccharidosis; sulfatase
    DOI:  https://doi.org/10.1042/BCJ20200586
  11. Mol Genet Metab Rep. 2020 Dec;25 100660
    Katja K, Inga V, Ramona L, Almuth C, Maria MN.
      Mucopolysaccharidosis type I (MPS I) is a rare lysosomal storage disease caused by biallelic mutations in IDUA, the gene coding for the lysosomal enzyme alpha L-iduronidase. Clinically MPS I is a chronic progressive multisystem disease typically presenting with coarse facial features, skeletal deformities, joint contractures, and multi-organ involvement. Hurler syndrome (MPS IH) represents the severe end of the spectrum of mucopolysaccharidosis type I and is characterized by central nervous system involvement leading to childhood dementia. Here we report on a severe affected MPS IH patient who is homozygous for a splice site mutation (c.158 + 1G > A) in the IDUA gene. Further analyses revealed maternal uniparental disomy of chromosome 4 with partial isodisomy of the telomeric end of chromosome 4 (4.p16.3p15.2), representing an extraordinary mode of inheritance with a much lower re-occurrence risk for MPS I in the family.
    Keywords:  Chromosome 4; IDUA; Mucopolysaccharidosis type I (MPS I); Partial maternal isodisomy; UPD
    DOI:  https://doi.org/10.1016/j.ymgmr.2020.100660
  12. Front Cell Dev Biol. 2020 ;8 587961
    Huang XH, Ma Y, Zheng MM, Chen N, Hu MN, Wu LY, Zheng Y, Lou YL, Xie DL.
      The marine bacterium Vibrio vulnificus causes potentially fatal bloodstream infections, typically in patients with chronic liver diseases. The inflammatory response and anti-bacterial function of phagocytes are crucial for limiting bacterial infection in the human hosts. How V. vulnificus affects macrophages after phagocytosis is unclear. In this report, we found that the bactericidal activity of macrophages to internalize V. vulnificus was dependent on mammalian target of rapamycin (mTOR) and NOD-like receptor (NLR) family pyrin domain containing 3 (NLRP3) interaction. Additionally, the NLRP3 expression was dependent on mTORC1 activation. Inhibited mTORC1 or absence of NLRP3 in macrophages impaired V. vulnificus-induced phagosome acidification and phagolysosome formation, leading to a reduction of intracellular bacterial clearance. mTORC1 signaling overactivation could increase NLRP3 expression and restore insufficient phagosome acidification. Together, these findings indicate that the intracellular bactericidal activity of macrophages responding to V. vulnificus infection is tightly controlled by the crosstalk of NLRP3 and mTOR and provide critical insight into the host bactericidal activity basis of clearance of V. vulnificus through lyso/phagosome.
    Keywords:  NLRP3; Vibrio vulnificus; acidification; bactericidal activity; mTOR; phagolysosome
    DOI:  https://doi.org/10.3389/fcell.2020.587961
  13. Mol Pharm. 2020 Oct 28.
    Santi M, Finamore F, Cecchettini A, Santorelli FM, Doccini S, Rocchiccioli S, Signore G.
      Infantile neural ceroid lipofuscinosis (INCL) is a lysosomal storage disorder characterized by mutations in the CLN1 gene that leads to lack of the lysosomal enzyme palmitoyl-protein thioesterase-1 (PPT1), which causes the progressive death of cortical neurons. Enzyme replacement therapy (ERT) is one of the most promising treatments, but its translation toward a clinical use is hampered by the need to deliver the enzyme to the central nervous system and a more detailed understanding of its capability to restore physiologic conditions at the biochemical and protein level, beyond the simple regulation of enzymatic activity. Targeted nanoparticles can promote protein delivery to the central nervous system and affect biological pathways inside cells. Here, we describe an innovative peptide-based stealth nanoparticle that inhibits serum protein adsorption exploiting transferrin-driven internalization to convey the PPT1 enzyme to transferrin receptor-mediated pathways (endocytosis in this work, or transcytosis, in perspective, in vivo). These enzyme-loaded nanoparticles were able to restore stable levels of enzymatic activity in CLN1 patient's fibroblasts, comparable with the free enzyme, demonstrating that delivery after encapsulation in the nanocarrier does not alter uptake or intracellular trafficking. We also investigate, for the first time, dysregulated pathways of proteome and palmitoylome and their alteration upon enzyme delivery. Our nanoparticles were able of halving palmitoylated protein levels restoring conditions similar to the normal cells. From proteomic analysis, we also highlighted the reduction of the different groups of proteins after treatments with the free or encapsulated enzyme. In conclusion, our system is able to deliver the enzyme to a model of CLN1 disease restoring normal conditions in cells. Investigation of molecular details of pathologic state and enzyme-based correction reveals dysregulated pathways with unprecedented details for CLN1. Finally, we unveil for the first time the dysregulation landscape of palmitoylome and proteome in primary patient-derived fibroblasts and their modifications in response to enzyme administration. These findings will provide a guideline for the validation of future therapeutic strategies based on enzyme replacement therapy or acting at different metabolic levels.
    Keywords:  blood brain barrier (BBB); enzyme replacement therapy (ERT); liposomes; lysosomal storage disorders (LSDs); peptide aptamers
    DOI:  https://doi.org/10.1021/acs.molpharmaceut.0c00615
  14. Mol Genet Metab Rep. 2020 Dec;25 100652
    Lee FS, Yen HJ, Niu DM, Hung GY, Lee CY, Yeh YC, Chen PC, Chang SK, Yang CF.
      Objective: To provide strategies for monitoring and treating severe lung involvement in Gaucher disease.Study design: We reviewed the chart of a 5-year-old boy who developed rapidly progressive, severe infiltrative lung involvement of Gaucher disease (GD) and improved after allogeneic hematopoietic stem cell transplant (HSCT), along with other case studies reported before December 2019. He was diagnosed with GD (homozygous mutation at c.1448 T > C, p.L483P), and started receiving enzyme replacement therapy (ERT) at 17 months old. He developed respiratory distress symptoms after 45 months of ERT; chest imaging reported diffuse interstitial infiltration of the bilateral lungs and consolidations at the right lungs. Allogeneic HSCT using cells from a matched unrelated donor was performed four months upon progressive respiratory symptoms.
    Results: His respiratory symptoms subsided in one month; chest imaging improvement, pulmonary function test improvement, and normalized activity of β-glucocerebrosidase were reported in three months.
    Conclusion: This is the first report of a patient who received early and regular ERT but developed severe infiltrative lung involvement and recovered after allogeneic HSCT. Based on study results, we suggest regular chest imaging, even for asymptomatic patients. For patients with severe lung involvement, rapid deterioration, and unresponsive to higher ERT dosages, allogeneic HSCT should be considered.
    Keywords:  CXR, Chest X-ray; ERT, Enzyme replacement therapy; FEF, Forced expiratory flow; FEV, Forced expiratory volume; FVC, Forced vital capacity; GD, Gaucher disease; Glucocerebrosidase; HRCT, High-resolution computed tomography; HSCT, Allogeneic hematopoietic stem cell transplant; Infiltrative lung disease; Lysosomal storage disease; PEF, Peak expiratory flow
    DOI:  https://doi.org/10.1016/j.ymgmr.2020.100652
  15. Life Sci Alliance. 2020 Dec;pii: e202000815. [Epub ahead of print]3(12):
    Zachari M, Longo M, Ganley IG.
      Autophagy is a crucial homeostatic mechanism that mediates the degradation of damaged or excess intracellular components. Such components are engulfed and sequestered into double membrane autophagosomes, which deliver their contents to lysosomes for degradation. Autophagy plays a role in numerous human disorders and its pharmacological targeting by small molecules offers therapeutic potential. The serine/threonine kinase ULK1 (and its homologue ULK2) is the most upstream component of the autophagic machinery and is required for autophagy initiation. Here, we use the most selective and potent published ULK1 inhibitors to gain insights into ULK1 kinase function during autophagy. Treatment with all inhibitors blocked autophagy but also resulted in the limited formation of initial autophagosome-like structures, which appeared abnormal in size and did not traffic to lysosomes. We found that upon ULK1 inhibition, phosphatidylinositol-3-phosphate-binding proteins are still recruited to forming autophagosomes, implying that ULK1 activity is not essential for VPS34 activation. We conclude that the kinase activity of ULK1 is important in regulating autophagosome maturation, by the phosphorylation of currently unidentified key substrates.
    DOI:  https://doi.org/10.26508/lsa.202000815
  16. Cancer Res. 2020 Oct 28. pii: canres.1998.2020. [Epub ahead of print]
    Xiao Y, Rabien A, Buschow R, Amstislavskiy V, Busch J, Kilic E, Villegas SL, Timmermann B, Schütte M, Mielke T, Yaspo ML, Jung K, Meierhofer D.
      Chromophobe renal cell carcinoma (chRCC) accounts for approximately 5% of all renal cancers and around 30% of chRCC cases have mutations in TP53. ChRCC is poorly supported by microvessels and has markably lower glucose uptake than clear cell RCC (ccRCC) and papillary RCC (pRCC). Currently, the metabolic status and mechanisms by which this tumor adapts to nutrient-poor microenvironments remain to be investigated. In this study, we performed proteome and metabolome profiling of chRCC tumors and adjacent kidney tissues and identified major metabolic alterations in chRCC tumors, including the classical Warburg effect, the downregulation of gluconeogenesis and amino acid metabolism, and the upregulation of protein degradation and endocytosis. ChRCC cells depended on extracellular macromolecules as an amino acid source by activating endocytosis to sustain cell proliferation and survival. Inhibition of the PLCG2/IP3/Ca2+/PKC pathway significantly impaired the activation of endocytosis for amino acids uptakes into chRCC cells. In chRCC, whole-exome sequencing revealed that TP53 mutations were not related to expression of PLCG2 and activation of endocytosis. Our study provides novel perspectives on metabolic rewiring in chRCC and identifies the PLCG2/IP3/Ca2+/PKC axis as a potential therapeutic target in chRCC patients.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-1998
  17. Mol Genet Metab Rep. 2020 Dec;25 100668
    Jiang Z, Derrick-Roberts ALK, Byers S.
      Bone elongation is driven by chondrocyte proliferation and hypertrophy in the growth plate. Both processes are modulated by multiple signaling pathways including the Indian Hedgehog (IHH) signaling pathway. Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders characterized by accumulation of glycosaminoglycans (GAGs) in multiple tissues and organs, leading to a range of clinical symptoms including bone shortening through mechanisms that are not fully understood. Using MPS VII mice, we previously observed a reduction in the number of proliferating and hypertrophic chondrocytes and a reduced gene expression of Ihh in the tibial growth plate. We further demonstrate here that IHH secretion by MPS VII chondrocytes was reduced both in vitro and in vivo. While normal chondrocytes showed no response to exogenous IHH, proliferation of MPS VII chondrocytes was stimulated in response to exogenous IHH in vitro. This was accompanied by an elevated gene expression of patched receptor (Ptch1). The results from this study suggested that reduced proliferation in MPS VII growth plate may be partially due to dysfunction of the IHH signaling pathway.
    Keywords:  Bone shortening; Chondrocyte proliferation; Growth plate; Indian hedgehog (IHH); Mucopolysaccharidosis (MPS)
    DOI:  https://doi.org/10.1016/j.ymgmr.2020.100668
  18. Onco Targets Ther. 2020 ;13 10515-10523
    Zhu X, Xu A, Zhang Y, Huo N, Cong R, Ma L, Chu Z, Tang Z, Kang X, Xian S, Xu X.
      Background: Renal cell cancer (RCC) is one of the most lethal malignancies of the kidney in adults. mTOR (mammalian target of rapamycin) signaling pathway plays a pivotal role in RCC tumorigenesis and progression and inhibitors targeting the mTOR pathway have been widely used in advanced RCC treatment. Therefore, it is of great significance to explore the potential regulators of the mTOR pathway as RCC therapeutic targets.Materials and Methods: Bioinformatics analysis was used to screen out the most significant differentially expressed genes in the RCC dataset of The Cancer Genome Atlas (TCGA). Real-time PCR and Western-blot analysis were utilized to examine the expression of inositol-1,4,5-trisphosphate-3-kinase-A (ITPKA) in four RCC cell lines and one human embryonic kidney cell line. Cell counting Kit-8 and colony formation assay were performed to estimate the effect of ITPKA on the proliferation ability of RCC cells. Wound healing and Transwell assays were used to test the effect of ITPKA on RCC cell migration and invasion. Xenograft formation assay was performed in nude mice to investigate the effect of ITPKA in vivo. mTORC1 pathway inhibitor was added to explore the mechanisms by which ITPKA regulates RCC cell growth and progression.
    Results: Based on bioinformatics analysis, ITPKA is screened out as one of the most significant differentially expressed genes in RCC. ITPKA is upregulated and positively correlated with RCC malignancy and poorer prognosis. ITPKA promotes RCC growth, migration and invasion in cultured cells, and accelerates tumor growth in nude mice. Mechanistically, ITPKA stimulates the mTORC1 signaling pathway which is a requirement for ITPKA modulation of RCC cell proliferation, migration and invasion.
    Conclusion: Our data demonstrate a critical regulatory role of the ITPKA in RCC and suggest that ITPKA/mTORC1 axis may be a promising target for diagnosis and treatment of RCC.
    Keywords:  ITPKA1; RCC; growth; mTORC1 pathway; migration and invasion
    DOI:  https://doi.org/10.2147/OTT.S266095
  19. Commun Biol. 2020 Oct 27. 3(1): 620
    Wu PH, Onodera Y, Giaccia AJ, Le QT, Shimizu S, Shirato H, Nam JM.
      Enhanced invasiveness, a critical determinant of metastasis and poor prognosis, has been observed in cancer cells that survive cancer therapy, including radiotherapy. Here, we show that invasiveness in radiation-surviving cancer cells is associated with alterations in lysosomal exocytosis caused by the enhanced activation of Arl8b, a small GTPase that regulates lysosomal trafficking. The binding of Arl8b with its effector, SKIP, is increased after radiation through regulation of BORC-subunits. Knockdown of Arl8b or BORC-subunits decreases lysosomal exocytosis and the invasiveness of radiation-surviving cells. Notably, high expression of ARL8B and BORC-subunit genes is significantly correlated with poor prognosis in breast cancer patients. Sp1, an ATM-regulated transcription factor, is found to increase BORC-subunit genes expression after radiation. In vivo experiments show that ablation of Arl8b decreases IR-induced invasive tumor growth and distant metastasis. These findings suggest that BORC-Arl8b-mediated lysosomal trafficking is a target for improving radiotherapy by inhibiting invasive tumor growth and metastasis.
    DOI:  https://doi.org/10.1038/s42003-020-01339-9
  20. Mol Genet Metab Rep. 2020 Dec;25 100663
    Bonesteele G, Gargus JJ, Curtin E, Tang M, Rosenbloom B, Kimonis V.
      Gaucher disease type 1 (GD1) is the most common lysosomal storage disease and affects nearly 1 in 40,000 live births. In addition, it is the most common genetic disorder in the Ashkenazi Jewish population with phenotypic variation presenting in early childhood to asymptomatic nonagenarians. There have been a number of studies showing an increased risk of certain malignancies in patients, especially non- Hodgkin's lymphoma (NHL) and multiple myeloma. We describe a 66-year-old Ashkenazi Jewish male with GD1 who was first started on enzyme replacement therapy (ERT) with imiglucerase for GD1 at age 57 years, followed a year later by the diagnosis of diffuse large b-cell non-Hodgkin's lymphoma (DLBCL). He was treated with R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone, plus the monoclonal antibody rituximab), however relapsed and developed myelodysplasia necessitating an allo-stem-cell transplantation but succumbed to severe graft vs. host disease. In addition, we also describe a 38-year-old Ashkenazi Jewish male with GD1 who was diagnosed with DLBCL at age 22 years with Gaucher disease diagnosed on pre-treatment bone marrow biopsy which was confirmed by enzyme assay and genotyping. At age 24 years, he was started on ERT with imiglucerase and at age 35 years, he switched to eliglustat. He has remained in remission from the lymphoma. A meta-analysis of the literature will be elaborated upon and we will discuss the relationship of GD1 to NHL and discuss more recent information regarding lyso-GL1 and the development of NHL and multiple myeloma.
    Keywords:  B-cell lymphoma; GBA1; Imiglucerase; Non-Hodgkin's lymphoma; Thrombocytopenia; lysoGL-1
    DOI:  https://doi.org/10.1016/j.ymgmr.2020.100663
  21. Cancer Med. 2020 Oct 27.
    Sakamoto H, Yamasaki T, Sumiyoshi T, Takeda M, Shibasaki N, Utsunomiya N, Arakaki R, Akamatsu S, Kobayashi T, Inoue T, Kamba T, Nakamura E, Ogawa O.
      Resistance to the mechanistic target of rapamycin (mTOR) inhibitors, which are a standard treatment for advanced clear cell renal cell carcinoma (ccRCC), eventually develops in most cases. In this study, we established a patient-derived xenograft (PDX) model which acquired resistance to the mTOR inhibitor temsirolimus, and explored the underlying mechanisms of resistance acquisition. Temsirolimus was administered to PDX model mice, and one cohort of PDX models acquired resistance after repeated passages. PDX tumors were genetically analyzed by whole-exome sequencing and detected several genetic alterations specific to resistant tumors. Among them, mutations in ANKRD12 and DNMT1 were already identified in the early passage of a resistant PDX model, and we focused on a DNMT1 mutation as a potential candidate for developing the resistant phenotype. While DNMT1 expression in temsirolimus-resistant tumors was comparable with the control tumors, DNMT enzyme activity was decreased in resistant tumors compared with controls. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9-mediated heterozygous knockdown of DNMT1 in the temsirolimus-sensitive ccRCC (786-O) cell line was shown to result in a temsirolimus-resistant phenotype in vitro and in vivo. Integrated gene profiles using methylation and microarray analyses of PDX tumors suggested a global shift for the hypomethylation status including promotor regions, and showed the upregulation of several molecules that regulate the mTOR pathway in temsirolimus-resistant tumors. Present study showed the feasibility of PDX model to explore the mechanisms of mTOR resistance acquisition and suggested that genetic alterations, including that of DNMT1, which alter the methylation status in cancer cells, are one of the potential mechanisms of developing resistance to temsirolimus.
    DOI:  https://doi.org/10.1002/cam4.3578
  22. Mol Genet Metab Rep. 2020 Dec;25 100662
    Sugiura K, Kubo T, Ochi Y, Baba Y, Hirota T, Yamasaki N, Kitaoka H.
      Background: Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disease caused by a deficiency of the lysosomal enzyme α-L-iduronidase. Cardiac manifestations such as valvular heart disease are associated with poor prognosis. There have been only a few reports on the effect of long-term enzyme replacement therapy (ERT) for adult patients with the attenuated form of MPS I (Scheie syndrome) and cardiac involvement.Methods: We retrospectively reviewed four adult patients of Scheie syndrome for which ERT was performed in our hospital. We investigated the findings of electrocardiography and echocardiography for the four patients performed before and 10 years after the initiation of ERT to evaluate the efficacy for ERT in Scheie syndrome.
    Results: The ages of the patients at the initiation of ERT ranged from 26 to 46 years. The mean follow-up period was 129 months (121 to 134 months). Two patients underwent valve replacement surgery before the initiation of ERT. One patient had gradual progressive aortic valve stenosis and mitral valve stenosis during the course of ERT, and double valve replacement was finally performed. The patient who had started ERT at the youngest age did not develop significant cardiovascular disease. Regarding clinical courses with ERT for a period of 10 years, all four patients survived and they showed relatively stable cardiac conditions although two patients developed sick sinus syndrome after the valvular surgery.
    Conclusions: Valvular disease in patients with Scheie syndrome occur at a young age. In a limited number of the four patients, ERT might contribute the stability of cardiac condition.
    Keywords:  Adults; Enzyme replacement therapy; Mucopolysaccharidosis; Scheie syndrome; Valvular disease
    DOI:  https://doi.org/10.1016/j.ymgmr.2020.100662
  23. Int J Mol Sci. 2020 Oct 23. pii: E7869. [Epub ahead of print]21(21):
    Menkovic I, Boutin M, Alayoubi A, Mercier FE, Rivard GÉ, Auray-Blais C.
      Gaucher disease (GD) is a rare autosomal recessive multisystemic lysosomal storage disorder presenting a marked phenotypic and genotypic variability. GD is caused by a deficiency in the glucocerebrosidase enzyme. The diagnosis of GD remains challenging because of the large clinical spectrum associated with the disease. Moreover, GD biomarkers are often not sensitive enough and can be subject to polymorphic variations. The main objective of this study was to perform a metabolomic study using an ultra-performance liquid chromatography system coupled to a time-of-flight mass spectrometer to identify novel GD biomarkers. Following the analysis of plasma samples from patients with GD, and age- and gender-matched control samples, supervised statistical analyses were used to find the best molecules to differentiate the two groups. Targeted biomarkers were structurally elucidated using accurate mass measurements and tandem mass spectrometry. This metabolomic study was successful in highlighting seven biomarkers associated with GD. Fragmentation tests revealed that these latter biomarkers were lyso-Gb1 (glucosylsphingosine) and four related analogs (with the following modifications on the sphingosine moiety: -C2H4, -H2, -H2+O, and +H2O), sphingosylphosphorylcholine, and N-palmitoyl-O-phosphocholineserine. Based on the plasma biomarker distribution, we suggest the evaluation of this GD biomarker profile, which might facilitate early diagnosis, monitoring, and follow-up of patients.
    Keywords:  Gaucher disease; N-palmitoyl-O-phosphocholineserine; biomarkers; glucosylsphingosine (lyso-Gb1); lyso-Gb1 analogs; mass spectrometry; metabolomics; plasma; sphingosylphosphorylcholine
    DOI:  https://doi.org/10.3390/ijms21217869
  24. Cell Rep. 2020 Oct 27. pii: S2211-1247(20)31305-X. [Epub ahead of print]33(4): 108316
    Nguyen HD, Ticer T, Bastian D, Kuril S, Li H, Du H, Yan C, Yu XZ.
      Graft-versus-host disease (GVHD) limits the success of allogeneic hematopoietic cell transplantation (allo-HCT). Lysosomal acid lipase (LAL) mediates the intrinsic lipolysis of cells to generate free fatty acids (FFAs), which play an essential role in the development, proliferation, and function of T cells. Here, we find that LAL is essential for donor T cells to induce GVHD in murine models of allo-HCT. Specifically, LAL is required for donor T cell survival, differentiation, and alloreactivity in GVHD target organs, but not in lymphoid organs. LAL induces the differentiation of donor T cells toward GVHD pathogenic Th1/Tc1 and Th17 while suppressing regulatory T cell generation. LAL-/- T cells succumb to oxidative stress and become anergic in target organs. Pharmacologically targeting LAL effectively prevents GVHD development while preserving the GVL activity. Thus, the present study reveals the role of LAL in T cell alloresponse and pathogenicity and validates LAL as a target for controlling GVHD and tumor relapse after allo-HCT.
    Keywords:  GVHD; GVL; LAL; T cells; hematopoietic cell transplantation; lipid metabolism; orlistat
    DOI:  https://doi.org/10.1016/j.celrep.2020.108316
  25. J Clin Invest. 2020 Oct 27. pii: 132727. [Epub ahead of print]
    Keane L, Antignano I, Riechers SP, Zollinger R, Dumas AA, Offermann N, Bernis ME, Russ J, Graelmann FJ, McCormick PN, Esser J, Tejera D, Nagano A, Wang J, Chelala C, Biederbick Y, Halle A, Salomoni P, Heneka MT, Capasso M.
      Microglia maintain homeostasis in the brain. However, with age, they become primed and respond more strongly to inflammatory stimuli. We show here that microglia from aged mice upregulated mammalian target of rapamycin (mTOR) complex 1 signaling regulating translation, as well as protein levels of inflammatory mediators. Genetic ablation of mTOR signaling showed a dual, yet contrasting effect on microglia priming: it caused an NF-kB-dependent upregulation of priming genes at mRNA level; however, mice displayed reduced cytokine protein levels, diminished microglia activation and milder sickness behavior. The effect on translation was dependent on reduced phosphorylation of 4EBP1, resulting in decreased binding of eIF4E to eIF4G. Similar changes were present in aged human microglia and in damage-associated microglia, indicating upregulation of mTOR-dependent translation is an essential step licensing microglia priming in aging and neurodegeneration.
    Keywords:  Aging; Cytokines; Inflammation; Macrophages; Translation
    DOI:  https://doi.org/10.1172/JCI132727
  26. J Biol Chem. 2020 Oct 29. pii: jbc.RA120.014248. [Epub ahead of print]
    Walvekar AS, Kadamur G, Sreedharan S, Gupta R, Srinivasan R, Laxman S.
      Methionine, through S-adenosylmethionine, activates a multifaceted growth program in which ribosome biogenesis, carbon metabolism, amino acid and nucleotide biosynthesis are induced. This growth program requires the activity of the Gcn4 transcription factor (called ATF4 in mammals), which facilitates the supply of metabolic precursors that are essential for anabolism. However, how Gcn4 itself is regulated in the presence of methionine is unknown. Here, we discover that Gcn4 protein levels are increased by methionine, despite conditions of high cell growth and translation (where the roles of Gcn4 are not well studied). We demonstrate that this mechanism of Gcn4 induction is independent of transcription, as well as the conventional Gcn2/eIF2α-mediated increased translation of Gcn4. Instead, when methionine is abundant, Gcn4 phosphorylation is decreased, which reduces its ubiquitination and therefore degradation. Gcn4 is dephosphorylated by the protein phosphatase PP2A; our data show that when methionine is abundant, the conserved methyltransferase Ppm1 methylates and alters the activity of the catalytic subunit of PP2A, shifting the balance of Gcn4 towards a dephosphorylated, stable state. The absence of Ppm1 or the loss of the PP2A methylation destabilizes Gcn4 even when methionine is abundant, leading to collapse of the Gcn4-dependent anabolic program. These findings reveal a novel, methionine-dependent signaling and regulatory axis. Here methionine directs a conserved methyltransferase Ppm1, via its target phosphatase PP2A, to selectively stabilize Gcn4. Through this, cells conditionally modify a major phosphatase to stabilize a metabolic master-regulator and drive anabolism.
    Keywords:  Gcn4; S-adenosylmethionine (SAM); Saccharomyces cerevisiae; amino acid; methionine; methyltransferase; nucleotide; protein methylation; protein phosphatase 2 (PP2A)
    DOI:  https://doi.org/10.1074/jbc.RA120.014248
  27. Autophagy. 2020 Oct 30.
    Hwang HY, Shim JS, Kim D, Kwon HJ.
      Macroautophagy/autophagy (hereafter autophagy), the process of mass degradation of unnecessary elements within the cell, is often dysregulated in many diseases such as cancer, atherosclerosis, and neurodegenerative diseases. Hence, autophagy modulating agents have a great potential to be therapeutic agents for the autophagy-related diseases. Here we report that an anti-depressant drug sertraline (Sert) is an autophagy-inducing agent. Mechanistically, Sert potentially binds to and antagonizes the mitochondrial VDAC1 (voltage dependent anion channel 1), resulting in reduced cellular ATP (adenosine triphosphate) level, activation of AMP-activated protein kinase (AMPK) and inhibition of its downstream, MTOR (mechanistic target of rapamycin kinase)-RPS6KB1 (ribosomal protein S6 kinase B1) signaling pathway. Cells lacking VDAC1 expression completely abrogate the modulatory effect of Sert on AMPK-MTOR pathway and autophagy-inducing activity. We further show that Sert suppresses tauopathy by promoting the autophagic degradation of MAPT (microtubule associated protein tau) protein via inducing autophagy. Our study demonstrates the potential of Sert as a novel small molecule autophagy-inducing agent and provides a new drug candidate to treat autophagy related diseases by targeting VDAC1.
    Keywords:  AMPK; DARTS; MAPT; MTOR; Sert; VDAC1; antidepressant; tauopathy
    DOI:  https://doi.org/10.1080/15548627.2020.1841953
  28. J Neuroophthalmol. 2020 Oct 26.
    Bacci GM, Polizzi S, Mari F, Conti V, Caputo R, Guerrini R.
      Tuberous sclerosis complex (TSC) is an autosomal dominant multisystemic disorder caused by mutations in either TSC1 or TSC2 genes and is characterized by hamartomas in multiple organs. The most frequent and best-known ocular manifestation in TSC is the retinal hamartoma. Less frequent ocular manifestations include punched out areas of retinal depigmentation, eyelid angiofibromas, uveal colobomas, papilledema, and sector iris depigmentation. In this article, we report 2 patients carrying known pathogenic variants in the TSC2 gene who exhibited an atypical, unilateral, iris coloboma associated with localized areas of retinal dysembryogenesis.
    DOI:  https://doi.org/10.1097/WNO.0000000000001099
  29. Front Cell Dev Biol. 2020 ;8 577342
    Ueda S, Tamura N, Mima J.
      Membrane tethering is a crucial step to determine the spatiotemporal specificity of secretory and endocytic trafficking pathways in all eukaryotic endomembrane systems. Recent biochemical studies by a chemically-defined reconstitution approach reveal that, in addition to the structurally-diverse classic tethering factors such as coiled-coil tethering proteins and multisubunit tethering complexes, Rab-family small GTPases also retain the inherent membrane tethering functions to directly and physically bridge two distinct lipid bilayers by themselves. Although Rab-mediated membrane tethering reactions are fairly efficient and specific in the physiological context, its mechanistic basis is yet to be understood. Here, to explore whether and how the intrinsic tethering potency of Rab GTPases is controlled by their C-terminal hypervariable region (HVR) domains that link the conserved small GTPase domains (G-domains) to membrane anchors at the C-terminus, we quantitatively compared tethering activities of two representative Rab isoforms in humans (Rab5a, Rab4a) and their HVR-deleted mutant forms. Strikingly, deletion of the HVR linker domains enabled both Rab5a and Rab4a isoforms to enhance their intrinsic tethering potency, exhibiting 5- to 50-fold higher initial velocities of tethering for the HVR-deleted mutants than those for the full-length, wild-type Rabs. Furthermore, we revealed that the tethering activity of full-length Rab5a was significantly reduced by the omission of anionic lipids and cholesterol from membrane lipids and, however, membrane tethering driven by HVR-deleted Rab5a mutant was completely insensitive to the headgroup composition of lipids. Reconstituted membrane tethering assays with the C-terminally-truncated mutants of Rab4a further uncovered that the N-terminal residues in the HVR linker, located adjacent to the G-domain, are critical for regulating the intrinsic tethering activity. In conclusion, our current findings establish that the non-conserved, flexible C-terminal HVR linker domains define membrane tethering potency of Rab-family small GTPases through controlling the close attachment of the globular G-domains to membrane surfaces, which confers the active tethering-competent state of the G-domains on lipid bilayers.
    Keywords:  Rab GTPase; hypervariable region; liposome; membrane tethering; membrane trafficking; reconstitution; small GTPase
    DOI:  https://doi.org/10.3389/fcell.2020.577342
  30. Drug Discov Today. 2020 Oct 21. pii: S1359-6446(20)30430-X. [Epub ahead of print]
    Song JX, Liu J, Jiang Y, Wang ZY, Li M.
      The discovery of transcription factor EB (TFEB) as a master regulator of the autophagy-lysosomal pathway (ALP) has triggered increasing numbers of studies that aim to explore the therapeutic potential of targeting TFEB to treat neurodegenerative disorders (NDs) such as Alzheimer's disease and Parkinson's disease. So far, the findings are exciting and promising. Here, we delineate the dysfunction of the TFEB-mediated ALP in NDs, and we summarize small molecules that have been identified as TFEB activators, along with their protective effects in NDs. We discuss the molecular mechanisms and targets, and the pros and cons of these TFEB activators from the perspective of drug development. Specific and potent small-molecule TFEB activators with ideal brain bioavailability could provide a method for treating NDs.
    Keywords:  Autophagy‐lysosomal pathway; Neurodegenerative disorders; Small molecules; Transcription factor EB
    DOI:  https://doi.org/10.1016/j.drudis.2020.10.013
  31. Cells. 2020 Oct 22. pii: E2342. [Epub ahead of print]9(11):
    Turnham DJ, Bullock N, Dass MS, Staffurth JN, Pearson HB.
      Loss of the tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which negatively regulates the PI3K-AKT-mTOR pathway, is strongly linked to advanced prostate cancer progression and poor clinical outcome. Accordingly, several therapeutic approaches are currently being explored to combat PTEN-deficient tumors. These include classical inhibition of the PI3K-AKT-mTOR signaling network, as well as new approaches that restore PTEN function, or target PTEN regulation of chromosome stability, DNA damage repair and the tumor microenvironment. While targeting PTEN-deficient prostate cancer remains a clinical challenge, new advances in the field of precision medicine indicate that PTEN loss provides a valuable biomarker to stratify prostate cancer patients for treatments, which may improve overall outcome. Here, we discuss the clinical implications of PTEN loss in the management of prostate cancer and review recent therapeutic advances in targeting PTEN-deficient prostate cancer. Deepening our understanding of how PTEN loss contributes to prostate cancer growth and therapeutic resistance will inform the design of future clinical studies and precision-medicine strategies that will ultimately improve patient care.
    Keywords:  PI3K; PTEN; prostate cancer; targeted therapy
    DOI:  https://doi.org/10.3390/cells9112342
  32. Life Sci. 2020 Oct 27. pii: S0024-3205(20)31415-6. [Epub ahead of print] 118662
    Yong CQY, Tang BL.
      The core machinery for vesicular membrane trafficking broadly comprises of coat proteins, RABs, tethering complexes and SNAREs. As cellular membrane traffic modulates key processes of mitogenic signaling, cell migration, cell death and autophagy, its dysregulation could potentially results in increased cell proliferation and survival, or enhanced migration and invasion. Changes in the levels of some components of the core machinery of vesicular membrane trafficking, likely due to gene amplifications and/or alterations in epigenetic factors (such as DNA methylation and micro RNA) have been extensively associated with human cancers. Here, we provide an overview of association of membrane trafficking with cancer, with a focus on mutations and variants of coat proteins, RABs, tethering complex components and SNAREs that have been uncovered in human cancer cells/tissues. The major cellular and molecular cancer-driving or suppression mechanisms associated with these components of the core membrane trafficking machinery shall be discussed.
    Keywords:  Cancer; Coat proteins; RABs; Retromer; SNAREs; Tethering complexes
    DOI:  https://doi.org/10.1016/j.lfs.2020.118662
  33. Int J Neonatal Screen. 2020 Oct 14. pii: E79. [Epub ahead of print]6(4):
    Bilyeu H, Washburn J, Vermette L, Klug T.
      Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome, is a lysosomal storage disorder (LSD) caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS). MPS II satisfies all criteria defined by the Advisory Committee on Heritable Disorders in Newborns and Children (ACHDNC) for inclusion in the Recommended Uniform Screening Panel (RUSP) for newborn screening, apart from the fact that only minimal prospective population screening data are available. This report details the analytical validation, clinical validation, and implementation of a fluorometric assay for measurement of IDS activity in newborn dried blood spot (DBS) specimens at the Missouri State Public Health Laboratory (MSPHL). The assay is performed in a microwell plate format requiring approximately 15 min of hands-on time per plate and an incubation time of two hours. The analytical validation of this assay included linearity, analytical sensitivity, precision, and carry-over testing. Clinical validation was completed using more than 5000 deidentified presumptive normal newborn DBS specimens as well as seven specimens from patients known to be affected with MPS II. Following validation, MSPHL began prospective screening using the IDS assay on 1 November 2018. In the first 18 months of screening (to 30 June 2020), 146,954 specimens were prospectively screened using the method. Two newborns were identified with severe Hunter syndrome and the assay had a presumptive positive rate of 0.022%.
    Keywords:  Hunter syndrome; analytical validation; clinical validation; mucopolysaccharidosis II; newborn screening
    DOI:  https://doi.org/10.3390/ijns6040079
  34. Nat Commun. 2020 Oct 30. 11(1): 5488
    Lee KM, Guerrero-Zotano AL, Servetto A, Sudhan DR, Lin CC, Formisano L, Jansen VM, González-Ericsson P, Sanders ME, Stricker TP, Raj G, Dean KM, Fiolka R, Cantley LC, Hanker AB, Arteaga CL.
      The 17q23 amplicon is associated with poor outcome in ER+ breast cancers, but the causal genes to endocrine resistance in this amplicon are unclear. Here, we interrogate transcriptome data from primary breast tumors and find that among genes in 17q23, PRR11 is a key gene associated with a poor response to therapeutic estrogen suppression. PRR11 promotes estrogen-independent proliferation and confers endocrine resistance in ER+ breast cancers. Mechanistically, the proline-rich motif-mediated interaction of PRR11 with the p85α regulatory subunit of PI3K suppresses p85 homodimerization, thus enhancing insulin-stimulated binding of p110-p85α heterodimers to IRS1 and activation of PI3K. PRR11-amplified breast cancer cells rely on PIK3CA and are highly sensitive to PI3K inhibitors, suggesting that PRR11 amplification confers PI3K dependence. Finally, genetic and pharmacological inhibition of PI3K suppresses PRR11-mediated, estrogen-independent growth. These data suggest ER+/PRR11-amplified breast cancers as a novel subgroup of tumors that may benefit from treatment with PI3K inhibitors and antiestrogens.
    DOI:  https://doi.org/10.1038/s41467-020-19291-x
  35. Autophagy. 2020 Oct 28.
    Zou B, Liu J, Klionsky DJ, Tang D, Kang R.
      Excessive inflammation may lead to irreparable injury and even death, but the key mediators and underlying mechanisms remain unclear. Our recent findings indicate that SQSTM1/p62 (sequestosome 1), a well-known macroautophagy/autophagy receptor, is a lethal inflammatory mediator of sepsis and septic shock. The release of SQSTM1 occurs during tissue damage or microbial invasion through two main ways: one is passive and the other is active. Passive release occurs in the context of GSDMD-mediated pyroptosis. Active SQSTM1 secretion requires two basic steps: the first step is the expression and phosphorylation of SQSTM1 mediated by STING1/STING/TMEM173, and then the unconventional secretion of SQSTM1 by secretory lysosomes. After release, the extracellular SQSTM1 binds to membrane receptor INSR to activate glycolysis, leading to subsequent production of pro-inflammatory cytokines in a transcription factor NFKB-dependent manner. Functionally, genetic deletion or pharmacological inhibition of the SQSTM1-INSR pathway limits tissue damage, systemic inflammation, organ failure, and death in experimental sepsis models in mice. Moreover, the activation of the SQSTM1-INSR pathway is related to the severity of sepsis in patients. These findings highlight a pathological role of extracellular SQSTM1 in infection, inflammation, and immunity.
    Keywords:  DAMP; INSR; SQSTM1; STING1; TLR4; autophagy; immunometabolism; inflammasome; sepsis
    DOI:  https://doi.org/10.1080/15548627.2020.1843253
  36. Front Endocrinol (Lausanne). 2020 ;11 575070
    Ding L, Houben T, Oligschlaeger Y, Bitorina AV, Verwer BJ, Tushuizen ME, Shiri-Sverdlov R.
      Objective: Type 2 diabetes mellitus is a metabolic disorder characterized by insulin resistance. Previous studies in patients demonstrated that plasma levels of cathepsin D (CTSD), which is optimally active in the acidic environment of lysosomes, correlate with insulin resistance. As plasma pH is slightly reduced in type 2 diabetic patients and we have previously shown that plasma CTSD activity is causally linked to insulin levels in vivo, it is likely that the activity of CTSD in plasma will be increased in type 2 diabetes compared to healthy individuals. However, so far the interaction between CTSD activity and levels to postprandial metabolic derangements in type 2 diabetes is not known.Methods: Eighteen type 2 diabetes and 16 age-matched healthy males were given 2 consecutive standardized mixed meals, after which blood samples were collected. Plasma metabolic parameters as well as CTSD levels and activity were measured, and changes in plasma pH was assessed.
    Results: In line with the elevation of plasma free fatty acids (FFA) levels in male type 2 diabetics patients, plasma pH in type 2 diabetic individuals was decreased compared to male healthy individuals. While plasma CTSD levels were similar, plasma CTSD activity was increased in male type 2 diabetic compared to male healthy individuals. Besides, plasma CTSD activity rather than levels significantly correlated with indicators of type 2 diabetes (HbA1c, HOMA-IR and glucose). Furthermore, FFA was also independently associated with plasma CTSD activity (standardized β = 0.493, p = 0.007).
    Conclusions: Despite similar plasma CTSD levels, type 2 diabetic male individuals showed increased plasma CTSD activity compared to healthy males, which was independently linked to plasma FFA levels. Our data therefore point toward plasma CTSD as a metabolic regulator in male type 2 diabetes.
    Keywords:  insulin resistance; metabolism; plasma cathepsin D activity; plasma levels of cathepsin D; plasma pH; type 2 diabetes
    DOI:  https://doi.org/10.3389/fendo.2020.575070
  37. J Clin Endocrinol Metab. 2020 Oct 29. pii: dgaa786. [Epub ahead of print]
    Ni Q, Song J, Wang Y, Sun J, Xie J, Zhang J, Ning G, Wang W, Wang Q.
      CONTEXT: The mTORC1 is crucial for beta cell identity and function in rodents. However, its possible relevance to physiopathology of diabetes in human remains unclear.OBJECTIVE: To understand the participation of mTORC1 in human beta cells in prediabetes and diabetes.
    DESIGN: We evaluated the PS6 immunofluorescence intensity in islets of pancreatic sections from 12 non-diabetic (ND), 11 impaired fasting glucose (IFG) and 11 glycemic-controlled type 2 diabetic (T2D) subjects. We also assessed the dynamic change of mTORC1 activity in beta cells of db/db mice with newly onset of diabetes.
    RESULTS: There exists inter-cellular heterogeneity of mTORC1 activities in human islet. Islet mTORC1 activity was independently and positively correlated with FBG in ND, but not in IFG and T2D. Moreover, we did not detect significant change in mTORC1 activities between T2D and ND. Of note, the islet mTORC1 activities were significantly higher in IFG than in ND. We further stratified IFG according to their islet PS6 levels and found that IFG-PS6 high exhibited remarkably higher Ucn3 and Glut2 expression in their beta cells compared to IFG-PS6 low. Consistently, we also detected a significant increase in mTORC1 activities in prediabetic db/db mice, compared to non-diabetic littermates. Interestingly, mTORC1 activities determined beta cell adaptation or failure in db/db mice: a strong negative correlation was found between islet mTORC1 activities and fasting glucose levels in db/db mice during their progression to diabetes.
    CONCLUSIONS: Our finding highlights a dynamic islet mTORC1 response in beta cell adaption/failure in human T2D.
    Keywords:  beta cell; impaired fasting glucose; mTORC1; type 2 diabetes
    DOI:  https://doi.org/10.1210/clinem/dgaa786
  38. Nat Struct Mol Biol. 2020 Oct 26.
    Maeda S, Yamamoto H, Kinch LN, Garza CM, Takahashi S, Otomo C, Grishin NV, Forli S, Mizushima N, Otomo T.
      De novo formation of the double-membrane compartment autophagosome is seeded by small vesicles carrying membrane protein autophagy-related 9 (ATG9), the function of which remains unknown. Here we find that ATG9A scrambles phospholipids of membranes in vitro. Cryo-EM structures of human ATG9A reveal a trimer with a solvated central pore, which is connected laterally to the cytosol through the cavity within each protomer. Similarities to ABC exporters suggest that ATG9A could be a transporter that uses the central pore to function. Moreover, molecular dynamics simulation suggests that the central pore opens laterally to accommodate lipid headgroups, thereby enabling lipids to flip. Mutations in the pore reduce scrambling activity and yield markedly smaller autophagosomes, indicating that lipid scrambling by ATG9A is essential for membrane expansion. We propose ATG9A acts as a membrane-embedded funnel to facilitate lipid flipping and to redistribute lipids added to the outer leaflet of ATG9 vesicles, thereby enabling growth into autophagosomes.
    DOI:  https://doi.org/10.1038/s41594-020-00520-2
  39. Nat Struct Mol Biol. 2020 Oct 26.
    Matoba K, Kotani T, Tsutsumi A, Tsuji T, Mori T, Noshiro D, Sugita Y, Nomura N, Iwata S, Ohsumi Y, Fujimoto T, Nakatogawa H, Kikkawa M, Noda NN.
      The molecular function of Atg9, the sole transmembrane protein in the autophagosome-forming machinery, remains unknown. Atg9 colocalizes with Atg2 at the expanding edge of the isolation membrane (IM), where Atg2 receives phospholipids from the endoplasmic reticulum (ER). Here we report that yeast and human Atg9 are lipid scramblases that translocate phospholipids between outer and inner leaflets of liposomes in vitro. Cryo-EM of fission yeast Atg9 reveals a homotrimer, with two connected pores forming a path between the two membrane leaflets: one pore, located at a protomer, opens laterally to the cytoplasmic leaflet; the other, at the trimer center, traverses the membrane vertically. Mutation of residues lining the pores impaired IM expansion and autophagy activity in yeast and abolished Atg9's ability to transport phospholipids between liposome leaflets. These results suggest that phospholipids delivered by Atg2 are translocated from the cytoplasmic to the luminal leaflet by Atg9, thereby driving autophagosomal membrane expansion.
    DOI:  https://doi.org/10.1038/s41594-020-00518-w
  40. Cell Death Dis. 2020 Oct 26. 11(10): 918
    Li Q, Cheng H, Liu Y, Wang X, He F, Tang L.
      Damage to intestinal epithelial cells and the induction of cellular apoptosis are characteristics of inflammatory bowel disease. The C-type lectin receptor family member LSECtin promotes apoptotic cell clearance by macrophages and induces the production of anti-inflammatory/tissue growth factors, which direct intestinal repair in experimental colitis. However, the mechanisms by which the phagocytosis of apoptotic cells triggers the pro-repair function of macrophages remain largely undefined. Here, using immunoprecipitation in combination with mass spectrometry to identify LSECtin-interacting proteins, we found that LSECtin interacted with mTOR, exhibiting a role in activating mTORC1. Mechanistically, apoptotic cells enhance the interaction between LSECtin and mTOR, and increase the activation of mTORC1 induced by LSECtin in macrophages. Elevated mTORC1 signaling triggers macrophages to produce anti-inflammatory/tissue growth factors that contribute to the proliferation of epithelial cells and promote the reestablishment of tissue homeostasis. Collectively, our findings suggest that LSECtin-dependent apoptotic cell clearance by macrophages activates mTORC1, and thus contributes to intestinal regeneration and the remission of colitis.
    DOI:  https://doi.org/10.1038/s41419-020-03114-4
  41. Aging (Albany NY). 2020 Oct 27. 12
    Zheng B, Sun X, Chen XF, Chen Z, Zhu WL, Zhu H, Gu DH.
      CC-115 is a dual inhibitor of DNA-PKcs and mTOR, both are valuable therapeutic targets for renal cell carcinoma (RCC). Our results showed that CC-115 inhibited survival and proliferation of established RCC cell lines (786-O and A489) and primary human RCC cells. The dual inhibitor induced selective apoptosis activation in RCC cells, as compared to no cytotoxicity nor apoptotic effects toward normal renal epithelial cells. CC-115 inhibited DNA-PKcs and mTORC1/2 activation in RCC cells. It was however ineffective in DNA-PKcs-mTOR double knockout (DKO) 786-O cells. CC-115 induced feedback autophagy activation in RCC cells. Autophagy inhibitors or Beclin-1/Light chain 3 (LC3) silencing potentiated CC-115-induced anti-RCC cell activity. Conversely, ectopic overexpression of Beclin-1 inhibited CC-115-induced cytotoxicity. At last CC-115 oral administration inhibited 786-O subcutaneous xenograft growth in nude mice. Taken together, dual inhibition of DNA-PKcs and mTOR by CC-115 potently inhibited RCC cell growth.
    Keywords:  CC-115; DNA-PKcs; autophagy; mTOR; renal cell carcinoma
    DOI:  https://doi.org/10.18632/aging.103847