bims-lysosi Biomed News
on Lysosomes and signaling
Issue of 2020‒11‒15
thirty-six papers selected by
Stephanie Fernandes
Max Planck Institute for Biology of Ageing


  1. iScience. 2020 Nov 20. 23(11): 101691
    Contreras PS, Tapia PJ, González-Hódar L, Peluso I, Soldati C, Napolitano G, Matarese M, Heras ML, Valls C, Martinez A, Balboa E, Castro J, Leal N, Platt FM, Sobota A, Winter D, Klein AD, Medina DL, Ballabio A, Alvarez AR, Zanlungo S.
      The transcription factor EB (TFEB) has emerged as a master regulator of lysosomal biogenesis, exocytosis, and autophagy, promoting the clearance of substrates stored in cells. c-Abl is a tyrosine kinase that participates in cellular signaling in physiological and pathophysiological conditions. In this study, we explored the connection between c-Abl and TFEB. Here, we show that under pharmacological and genetic c-Abl inhibition, TFEB translocates into the nucleus promoting the expression of its target genes independently of its well-known regulator, mammalian target of rapamycin complex 1. Active c-Abl induces TFEB phosphorylation on tyrosine and the inhibition of this kinase promotes lysosomal biogenesis, autophagy, and exocytosis. c-Abl inhibition in Niemann-Pick type C (NPC) models, a neurodegenerative disease characterized by cholesterol accumulation in lysosomes, promotes a cholesterol-lowering effect in a TFEB-dependent manner. Thus, c-Abl is a TFEB regulator that mediates its tyrosine phosphorylation, and the inhibition of c-Abl activates TFEB promoting cholesterol clearance in NPC models.
    Keywords:  Biological Sciences; Cell Biology; Molecular Biology
    DOI:  https://doi.org/10.1016/j.isci.2020.101691
  2. Cell Rep. 2020 Nov 10. pii: S2211-1247(20)31360-7. [Epub ahead of print]33(6): 108371
    Carey KL, Paulus GLC, Wang L, Balce DR, Luo JW, Bergman P, Ferder IC, Kong L, Renaud N, Singh S, Kost-Alimova M, Nyfeler B, Lassen KG, Virgin HW, Xavier RJ.
      Transcription factor EB (TFEB) activates lysosomal biogenesis genes in response to environmental cues. Given implications of impaired TFEB signaling and lysosomal dysfunction in metabolic, neurological, and infectious diseases, we aim to systematically identify TFEB-directed circuits by examining transcriptional responses to TFEB subcellular localization and stimulation. We reveal that steady-state nuclear TFEB is sufficient to activate transcription of lysosomal, autophagy, and innate immunity genes, whereas other targets require higher thresholds of stimulation. Furthermore, we identify shared and distinct transcriptional signatures between mTOR inhibition and bacterial autophagy. Using a genome-wide CRISPR library, we find TFEB targets that protect cells from or sensitize cells to lysosomal cell death. BHLHE40 and BHLHE41, genes responsive to high, sustained levels of nuclear TFEB, act in opposition to TFEB upon lysosomal cell death induction. Further investigation identifies genes counter-regulated by TFEB and BHLHE40/41, adding this negative feedback to the current understanding of TFEB regulatory mechanisms.
    Keywords:  BHLHE40; BHLHE41; TFEB; autophagy; gene regulation; lysosome; xenophagy
    DOI:  https://doi.org/10.1016/j.celrep.2020.108371
  3. Nature. 2020 Nov 11.
    Lu XY, Shi XJ, Hu A, Wang JQ, Ding Y, Jiang W, Sun M, Zhao X, Luo J, Qi W, Song BL.
      Cholesterol is an essential lipid and its synthesis is nutritionally and energetically costly1,2. In mammals, cholesterol biosynthesis increases after feeding and is inhibited under fasting conditions3. However, the regulatory mechanisms of cholesterol biosynthesis at the fasting-feeding transition remain poorly understood. Here we show that the deubiquitylase ubiquitin-specific peptidase 20 (USP20) stabilizes HMG-CoA reductase (HMGCR), the rate-limiting enzyme in the cholesterol biosynthetic pathway, in the feeding state. The post-prandial increase in insulin and glucose concentration stimulates mTORC1 to phosphorylate USP20 at S132 and S134; USP20 is recruited to the HMGCR complex and antagonizes its degradation. The feeding-induced stabilization of HMGCR is abolished in mice with liver-specific Usp20 deletion and in USP20(S132A/S134A) knock-in mice. Genetic deletion or pharmacological inhibition of USP20 markedly decreases diet-induced body weight gain, reduces lipid levels in the serum and liver, improves insulin sensitivity and increases energy expenditure. These metabolic changes are reversed by expression of the constitutively stable HMGCR(K248R). This study reveals an unexpected regulatory axis from mTORC1 to HMGCR via USP20 phosphorylation and suggests that inhibitors of USP20 could be used to lower cholesterol levels to treat metabolic diseases including hyperlipidaemia, liver steatosis, obesity and diabetes.
    DOI:  https://doi.org/10.1038/s41586-020-2928-y
  4. Sci Adv. 2020 Nov;pii: eabb2454. [Epub ahead of print]6(46):
    Bonet-Ponce L, Beilina A, Williamson CD, Lindberg E, Kluss JH, Saez-Atienzar S, Landeck N, Kumaran R, Mamais A, Bleck CKE, Li Y, Cookson MR.
      Genetic variation around the LRRK2 gene affects risk of both familial and sporadic Parkinson's disease (PD). However, the biological functions of LRRK2 remain incompletely understood. Here, we report that LRRK2 is recruited to lysosomes after exposure of cells to the lysosome membrane-rupturing agent LLOME. Using an unbiased proteomic screen, we identified the motor adaptor protein JIP4 as an LRRK2 partner at the lysosomal membrane. LRRK2 can recruit JIP4 to lysosomes in a kinase-dependent manner via the phosphorylation of RAB35 and RAB10. Using super-resolution live-cell imaging microscopy and FIB-SEM, we demonstrate that JIP4 promotes the formation of LAMP1-negative tubules that release membranous content from lysosomes. Thus, we describe a new process orchestrated by LRRK2, which we name LYTL (LYsosomal Tubulation/sorting driven by LRRK2), by which lysosomal tubulation is used to release vesicles from lysosomes. Given the central role of the lysosome in PD, LYTL is likely to be disease relevant.
    DOI:  https://doi.org/10.1126/sciadv.abb2454
  5. Mol Biol Rep. 2020 Nov 13.
    Jeger JL.
      Endosomes and lysosomes are membrane-bound organelles crucial for the normal functioning of the eukaryotic cell. The primary function of endosomes relates to the transportation of extracellular material into the intracellular domain. Lysosomes, on the other hand, are primarily involved in the degradation of macromolecules. Endosomes and lysosomes interact through two distinct pathways: kiss-and-run and direct fusion. In addition to the internalization of particles, endosomes also play an important role in cell signaling and autophagy. Disruptions in either of these processes may contribute to cancer development. Lysosomal proteins, such as cathepsins, can play a role in both tumorigenesis and cancer cell apoptosis. Since endosomal and lysosomal biogenesis and signaling are important components of normal cellular growth and proliferation, proteins involved in these processes are attractive targets for cancer research and, potentially, therapeutics. This literature review provides an overview of the endocytic pathway, endolysosome formation, and the interplay between endosomal/lysosomal biogenesis and carcinogenesis.
    Keywords:  Carcinogenesis; Cathepsins; Endocytosis; Endosomes; Lysosomes
    DOI:  https://doi.org/10.1007/s11033-020-05993-4
  6. Bioessays. 2020 Nov 09. e2000187
    Ramaian Santhaseela A, Jayavelu T.
      Extensive studies have attributed the lysosomal localization of the mechanistic target of rapamycin complex 1 (mTORC1) during its activation. However, the exact biological significance of this lysosomal localization of mTORC1 remains ill-defined. Interestingly, findings have shown that localization of the lysosome itself is altered under conditions influencing mTORC1 activity. In this perspective, we hypothesize that the localization of mTORC1 and lysosome could be interconnected in a way that manifests regulation of autophagy that is already under progression at the time of mTORC1 activation. This provides a new possibility for autophagy regulation whose complete mechanistic insights remain to be determined.
    Keywords:  autophagy; lysosome; mechanistic target of rapamycin complex 1; signal transduction
    DOI:  https://doi.org/10.1002/bies.202000187
  7. Osteoarthritis Cartilage. 2020 Nov 05. pii: S1063-4584(20)31162-6. [Epub ahead of print]
    Ansari MY, Ball HC, Wase SJ, Novak K, Haqqi TM.
      OBJECTIVE: Lysosomes are the major catabolic organelle of the cell and regulate the macromolecular and organelle turnover and programmed cell death. Here, we investigated the lysosome dysfunction in cartilage and its role in chondrocytes apoptosis and the associated mechanism.DESIGN: Lysosomal acidification in OA and aged cartilage was determined by LysoSensor staining. Lysosomal function in chondrocytes was blocked by siRNA mediated depletion of LAMP2 or with lysosome inhibitors. Chondrocyte apoptosis was determined by LDH release, Caspase-3/7 activation, TUNEL and PI uptake assays. Loss of mitochondrial membrane potential (MMP/ΔΨM) and mitochondrial superoxide level was determined by JC-1 and MitoSOX staining, respectively. Colocalization of mitochondria with BAX and Cytochrome c was determined by immunostaining. DMM was performed to induce OA in mice.
    RESULTS: Lysosomal acidification was found to be significantly decreased in aged mouse and human and mouse OA cartilage which also showed increased chondrocyte apoptosis. Inhibition of lysosomal function resulted in increased oxidative stress, accumulation of dysfunctional mitochondria and apoptosis in chondrocytes in monolayer and in cartilage explant cultures. Depletion of LAMP2 expression or treatment of chondrocytes with lysosomal function inhibitors increased the expression and mitochondrial translocation of BAX leading to Cytochrome c release. Lysosomal dysfunction-induced apoptosis in chondrocytes was not blocked by antioxidants MitoTempo or DPI but was abrogated by inhibiting BAX.
    CONCLUSION: Lysosomal dysfunction induce apoptosis in chondrocytes through BAX-mediated mitochondrial damage and release of Cytochrome c. Our data points to lysosomal function restoration and/or BAX inhibition in chondrocytes as a therapeutic approach for OA.
    Keywords:  Ageing; Apoptosis; BAX; Lysosomal dysfunction; Mitochondrial dysfunction; Osteoarthritis
    DOI:  https://doi.org/10.1016/j.joca.2020.08.014
  8. Rev Med Interne. 2020 Nov 07. pii: S0248-8663(20)30368-4. [Epub ahead of print]
    Michaud M, Mauhin W, Belmatoug N, Bedreddine N, Garnotel R, Catros F, Lidove O, Gaches F.
      Fabry disease is the second most frequent lysosomal storage disorder. It is a X-linked genetic disease secondary to alpha-galactosidase A enzyme deficiency. This is a progressive and systemic disease that affects both males and females. Classical symptoms and organ involvements are acral pain crisis, cornea verticillata, hypertrophic cardiomyopathy, stroke and chronic kidney disease with proteinuria. Nevertheless, organ damages can be missing or pauci-symptomatic and other common symptoms are poorly recognised, such as gastrointestinal or ear involvement. In classical Fabry disease, symptoms first appear during childhood or teenage in males, but later in females. Patients may have non-classical or late-onset Fabry disease with delayed manifestations or with single-organ involvement. Recognition of Fabry disease is important because treatments are available, but it may be challenging. Diagnosis is easy in males, with dosage of alpha-galactosidase A enzyme activity into leukocytes, but more difficult in females who can express normal residual activity. Other plasmatic biomarkers, such as lyso-globotriaosylceramide (lyso-Gb3), are interesting in females, but need to be associated with GLA gene analysis. In this review, we aimed at summarize the main clinical manifestations of Fabry disease and propose a practical algorithm to know how to diagnose this complex disease.
    Keywords:  Alpha-galactosidase A; Angiokeratoma; Angiokératome; Diagnosis; Diagnostic; Enzyme replacement therapy; Enzymothérapie substitutive; Fabry disease; GLA; Lyso-Gb3; Maladie de Fabry; Migalastat; Traitement; Treatment
    DOI:  https://doi.org/10.1016/j.revmed.2020.08.019
  9. Mol Genet Metab Rep. 2020 Dec;25 100658
    Zapała B, Chmura O, Ciałowicz U, Solnica B, Krajewska-Włodarczyk M, Żuber Z.
      Background and objectives: Mucopolysaccharidosis type VI (MPS VI) is a rare, autosomal recessive lysosomal storage disorder caused by deficient enzymatic activity of N-acetyl galactosamine-4-sulphatase, which is caused by mutations in the arylsulphatase B (ARSB) gene. To date, 163 different types of mutations in the ARSB have been reported. However, the full mutation spectrum in the MPS VI phenotype is still not known. The aim of this study was to perform molecular testing of the ARSB gene in the patient and his family members to confirm MPS VI.Methods: Molecular characterisation of the ARSB gene was performed using Sanger sequencing. We studied a child suspected of having MPS VI and 16 other relatives.
    Results: We identified a C-to-T transition resulting in an exchange of the Arg codon 160 for a premature stop codon (R160*, in exon 2). The transition was in CpG dinucleotides.
    Interpretation and conclusions: The study provided some insights into the genotype-phenotype relationship in MPS VI and the importance of genetic testing when diagnosing MPS, which is not a mandatory test for the diagnosis and only very occasionally performed. Additionally, we present here the history of a family with confirmed MPS VI, which is extremely rare especially in south-eastern Poland. What is more, the position where the mutation is located is very interesting because it is the region of CpG, which is the site of the methylation process. Thus, this opens the possibility of a new approach indicating the involvement of an epigenetic mechanism that should be examined in the context of the pathomechanism of MPS.
    Keywords:  ARSB gene; Genotype-phenotype relationship; Mucopolysaccharidosis
    DOI:  https://doi.org/10.1016/j.ymgmr.2020.100658
  10. Biochim Biophys Acta Mol Cell Biol Lipids. 2020 Nov 09. pii: S1388-1981(20)30247-X. [Epub ahead of print] 158855
    Dichlberger A, Zhou K, Bäck N, Nyholm T, Backman A, Mattjus P, Ikonen E, Blom T.
      Lysosome Associated Protein Transmembrane 4B (LAPTM4B) is a four-membrane spanning ceramide interacting protein that regulates mTORC1 signaling. Here, we show that LAPTM4B is sorted into intraluminal vesicles (ILVs) of multivesicular endosomes (MVEs) and released in small extracellular vesicles (sEVs) into conditioned cell culture medium and human urine. Efficient sorting of LAPTM4B into ILV membranes depends on its third transmembrane domain containing a sphingolipid interaction motif (SLim). Unbiased lipidomic analysis reveals a strong enrichment of glycosphingolipids in sEVs secreted from LAPTM4B knockout cells and from cells expressing a SLim-deficient LAPTM4B mutant. The altered sphingolipid profile is accompanied by a distinct SLim-dependent co-modulation of ether lipid species. The changes in the lipid composition of sEVs derived from LAPTM4B knockout cells is reflected by an increased stability of membrane nanodomains of sEVs. These results identify LAPTM4B as a determinant of the glycosphingolipid profile and membrane properties of sEVs.
    Keywords:  ether lipids; exosomes; extracellular vesicles; glycosphingolipids; membrane nanodomains; sphingolipids
    DOI:  https://doi.org/10.1016/j.bbalip.2020.158855
  11. Front Mol Neurosci. 2020 ;13 586731
    Jiang S, Bhaskar K.
      Tauopathies are a class of neurodegenerative diseases, including Alzheimer's disease (AD), Frontotemporal Dementia (FTD), Progressive Supranuclear Palsy (PSP), Corticobasal Degeneration (CBD), and many others where microtubule-associated protein tau (MAPT or tau) is hyperphosphorylated and aggregated to form insoluble paired helical filaments (PHFs) and ultimately neurofibrillary tangles (NFTs). Autophagic-endolysosomal networks (AELN) play important roles in tau clearance. Excessive soluble neurotoxic forms of tau and tau hyperphosphorylated at specific sites are cleared through the ubiquitin-proteasome system (UPS), Chaperon-mediated Autophagy (CMA), and endosomal microautophagy (e-MI). On the other hand, intra-neuronal insoluble tau aggregates are often degraded within lysosomes by macroautophagy. AELN defects have been observed in AD, FTD, CBD, and PSP, and lysosomal dysfunction was shown to promote the cleavage and neurotoxicity of tau. Moreover, several AD risk genes (e.g., PICALM, GRN, and BIN1) have been associated with dysregulation of AELN in the late-onset sporadic AD. Conversely, tau dissociation from microtubules interferes with retrograde transport of autophagosomes to lysosomes, and that tau fragments can also lead to lysosomal dysfunction. Recent studies suggest that tau is not merely an intra-neuronal protein, but it can be released to brain parenchyma via extracellular vesicles, like exosomes and ectosomes, and thus spread between neurons. Extracellular tau can also be taken up by microglial cells and astrocytes, either being degraded through AELN or propagated via exosomes. This article reviews the complex roles of AELN in the degradation and transmission of tau, potential diagnostic/therapeutic targets and strategies based on AELN-mediated tau clearance and propagation, and the current state of drug development targeting AELN and tau against tauopathies.
    Keywords:  autophagy; degradation; endo-lysosomal systems; glial cells; neuron; tau; tauopathy; transmission
    DOI:  https://doi.org/10.3389/fnmol.2020.586731
  12. Mol Ther. 2020 Nov 10. pii: S1525-0016(20)30610-9. [Epub ahead of print]
    Chen X, Snanoudj-Verber S, Pollard L, Hu Y, Cathey SS, Tikkanen R, Gray SJ.
      Aspartylglucosaminuria (AGU) is an autosomal recessive lysosomal storage disease caused by loss of the enzyme aspartylglucosaminidase (AGA), resulting in AGA substrate accumulation. AGU patients have a slow but progressive neurodegenerative disease course, for which there is no approved disease-modifying treatment. In this study, AAV9/AGA was administered to Aga-/- mice intravenously (IV) or intrathecally (IT), at range of doses, either before or after disease pathology begins. At either treatment age, AAV9/AGA administration led to 1) dose-dependently increased and sustained AGA activity in body fluids and tissues; 2) rapid, sustained, and dose-dependent elimination of AGA substrate in body fluids; 3) significantly rescued locomotor activity; 4) dose-dependent preservation of Purkinje neurons in the cerebellum; and 5) significantly reduced gliosis in the brain. Treated mice had no abnormal neurological phenotype and maintained body weight throughout the whole experiment to 18 months old. In summary, these results demonstrate that treatment of Aga-/- mice with AAV9/AGA is effective and safe, providing strong evidence that AAV9/AGA gene therapy should be considered for human translation. Further, we provide a direct comparison of the efficacy of an IV versus IT approach using AAV9, which should greatly inform the development of similar treatments for other related lysosomal storage diseases.
    DOI:  https://doi.org/10.1016/j.ymthe.2020.11.012
  13. J Cell Physiol. 2020 Nov 10.
    Chen X, Wang D, Sun B, Liu C, Zhu K, Zhang A.
      Arsenic is an environmental toxicant. Its overdose can cause liver damage. Autophagy has been reported to be involved in arsenite (iAs3+ ) cytotoxicity and plays a dual role in cell proliferation and cell death. However, the effect and molecular regulative mechanisms of iAs3+ on autophagy in hepatocytes remains largely unknown. Here, we found that iAs3+ exposure lead to hepatotoxicity by inducing autophagosome and autolysosome accumulation. On the one hand, iAs3+ promoted autophagosome synthesis by inhibiting E2F1/mTOR pathway in L-02 human hepatocytes. On the other, iAs3+ blocked autophagosome degradation partially via suppressing the expression of INPP5E and Rab7 as well as impairing lysosomal activity. More importantly, autophagosome and autolysosome accumulation induced by iAs3+ increased the protein level of E2F7a, which could further inhibit cell viability and induce apoptosis of L-02 cells. The treatment of Ginkgo biloba extract (GBE) effectively reduced autophagosome and autolysosome accumulation and thus alleviated iAs3+ -induced hepatotoxicity. Moreover, GBE could also protect lysosomal activity, promote the phosphorylation level of E2F1 (Ser364 and Thr433) and Rb (Ser780) as well as suppress the protein level of E2F7a in iAs3+ -treated L-02 cells. Taken together, our data suggested that autophagosome and autophagolysosome accumulation play a critical role for iAs3+ -induced hepatotoxicity, and GBE is a promising candidate for intervening iAs3+ induced liver damage by regulating E2F1-autophagy-E2F7a pathway and restoring lysosomal activity.
    Keywords:  E2F1; E2F7a; Ginkgo biloba extract; arsenite; autophagy; liver
    DOI:  https://doi.org/10.1002/jcp.30147
  14. J Pharmacol Exp Ther. 2020 Nov 10. pii: JPET-AR-2020-000309. [Epub ahead of print]
    Collins KP, Witta S, Coy J, Pang Y, Gustafson DL.
      Lysosomes act as a cellular drug sink for weakly basic, lipophilic (lysosomotropic) xenobiotics, with many instances of lysosomal trapping associated with MDR. Lysosomotropic agents have also been shown to activate master lysosomal biogenesis transcription factor EB (TFEB), and ultimately lysosomal biogenesis. We investigated the role of lysosomal biogenesis in the disposition of hydroxychloroquine (HCQ), a hallmark lysosomotropic agent, and observed that modulating the lysosomal volume of human breast cancer cell lines can account for differences in disposition of HCQ. Through use of an in vitro pharmacokinetic (PK) model we characterized total cellular uptake of HCQ within the duration of static equilibrium (1 hour), as well as extended exposure to HCQ that are subject to dynamic equilibrium (>1 hour) wherein HCQ increases the size of the lysosomal compartment through swelling and TFEB-induced lysosomal biogenesis. In addition, we show that pretreatment of cell lines with TFEB-activating agent Torin 1 contributed to an increase of HCQ whole cell concentrations by 1.4 to 1.6-fold, which were also characterized by the in vitro PK model. This investigation into the role of lysosomal volume dynamics in lysosomotropic drug disposition, including the ability of HCQ to modify its own disposition, advances our understanding of how chemically-similar agents may distribute on the cellular level, and examines a key area of lysosomal-mediated MDR and DDI. Significance Statement Hydroxychloroquine is able to modulate its own cellular pharmacokinetic uptake by increasing the cellular lysosomal volume fraction through activation of lysosomal biogenesis master transcription factor EB, and through lysosomal swelling. This concept can be applied to many other lysosomotropic drugs that activate TFEB, such as doxorubicin and other TKI drugs, where these drugs may actively increase their own sequestration within the lysosome to further exacerbate MDR and lead to potential acquired resistance.
    Keywords:  cell models; pharmacokinetic; pharmacokinetic/pharmacodynamic modeling/PKPD
    DOI:  https://doi.org/10.1124/jpet.120.000309
  15. Autophagy. 2020 Nov 08.
    Bensalem J, Hattersley KJ, Hein LK, Tong Teong X, Carosi JM, Hassiotis S, Grose RH, Fourrier C, Heilbronn LK, Sargeant TJ.
      Autophagic flux is a critical cellular process that is vastly under-appreciated in terms of its importance to human health. Preclinical studies have demonstrated that reductions in autophagic flux cause cancer and exacerbate chronic diseases, including heart disease and the pathological hallmarks of dementia. Autophagic flux can be increased by targeting nutrition-related biochemical signaling. To date, translation of this knowledge has been hampered because there has been no way to directly measure autophagic flux in humans. In this study we detail a method whereby human macroautophagic/autophagic flux can be directly measured from human blood samples. We show that whole blood samples can be treated with the lysosomal inhibitor chloroquine, and peripheral blood mononuclear cells isolated from these samples could be used to measure autophagic machinery protein LC3B-II. Blocking of autophagic flux in cells while still in whole blood represents an important advance because it preserves genetic, nutritional, and signaling parameters inherent to the individual. We show this method was reproducible and defined LC3B-II as the best protein to measure autophagic flux in these cells. Finally, we show that this method is relevant to assess intra-individual variation induced by an intervention by manipulating nutrition signaling with an ex vivo treatment of whole blood that comprised leucine and insulin. Significantly, this method will enable the identification of factors that alter autophagic flux in humans, and better aid their translation in the clinic. With further research, it could also be used as a novel biomarker for risk of age-related chronic disease.
    Keywords:  Autophagy; LC3B; PBMC; biomarker; blood; chloroquine; human; lysosome
    DOI:  https://doi.org/10.1080/15548627.2020.1846302
  16. Am J Pathol. 2020 Nov 04. pii: S0002-9440(20)30488-0. [Epub ahead of print]
    Ding X, Zhao T, Lee CC, Yan C, Du H.
      Utilization of proper preclinical models accelerates development of immunotherapeutic and the study of the interplay between human malignant cells and immune cells. Lysosomal acid lipase (LAL) is a critical lipid hydrolase that generates free fatty acids and cholesterol. Ablation of LAL suppresses immune-rejection and allows growth of human lung cancer cells in lal-/- mice. In the lal-/- lymph nodes, the percentages of both T regulatory and B regulatory cells (Tregs and Bregs) are increased with elevated expression of PD-L1, IL-10, and decreased expression of IFNγ. In Tregs and Bregs of the lal-/- lymph nodes, levels of enzymes in glucose and glutamine metabolic pathways are elevated. Pharmacologic inhibitor of pyruvate dehydrogenase (PDH), which controls the transition from glycolysis to the citric acid cycle, effectively reduces Treg and Breg elevation in the lal-/- lymph nodes. Blocking the mammalian target of rapamycin (mTOR) or reactivating peroxisome proliferator-activated receptor gamma (PPARγ), an LAL downstream effector, reduces lal-/- Treg and Breg elevation, PD-L1 expression in lal-/- Tregs and Bregs, and improves human cancer cell rejection. Treatment of PD-L1 antibody also reduces Treg and Breg elevation in the lal-/- lymph nodes and improves human cancer cell rejection. These observations conclude that LAL-regulated lipid metabolism is essential to maintain anti-tumor immunity.
    Keywords:  Bregs; PD-L1; PPARgamma; Tregs; human cancer cell-derived xenografts; lymph node; lysosomal acid lipase; mTOR; metabolic regulation; tumor animal models
    DOI:  https://doi.org/10.1016/j.ajpath.2020.10.007
  17. Autophagy. 2020 Nov 13. 1-17
    Siva Sankar D, Dengjel J.
      Autophagy summarizes evolutionarily conserved, intracellular degradation processes targeting cytoplasmic material for lysosomal degradation. These encompass constitutive processes as well as stress responses, which are often found dysregulated in diseases. Autophagy pathways help in the clearance of damaged organelles, protein aggregates and macromolecules, mediating their recycling and maintaining cellular homeostasis. Protein-protein interaction networks contribute to autophagosome biogenesis, substrate loading, vesicular trafficking and fusion, protein translocations across membranes and degradation in lysosomes. Hypothesis-free proteomic approaches tremendously helped in the functional characterization of protein-protein interactions to uncover molecular mechanisms regulating autophagy. In this review, we elaborate on the importance of understanding protein-protein-interactions of varying affinities and on the strengths of mass spectrometry-based proteomic approaches to study these, generating new mechanistic insights into autophagy regulation. We discuss in detail affinity purification approaches and recent developments in proximity labeling coupled to mass spectrometry, which uncovered molecular principles of autophagy mechanisms. Abbreviations: AMPK: AMP-activated protein kinase; AP-MS: affinity purification-mass spectrometry; APEX2: ascorbate peroxidase-2; ATG: autophagy related; BioID: proximity-dependent biotin identification; ER: endoplasmic reticulum; GFP: green fluorescent protein; iTRAQ: isobaric tag for relative and absolute quantification; MS: mass spectrometry; PCA: protein-fragment complementation assay; PL-MS: proximity labeling-mass spectrometry; PtdIns3P: phosphatidylinositol-3-phosphate; PTM: posttranslational modification; PUP-IT: pupylation-based interaction tagging; RFP: red fluorescent protein; SILAC: stable isotope labeling by amino acids in cell culture; TAP: tandem affinity purification; TMT: tandem mass tag.
    Keywords:  Autophagy; affinity purification; mass spectrometry; protein-protein interactions; proximity labeling; quantitative proteomics
    DOI:  https://doi.org/10.1080/15548627.2020.1847461
  18. Dev Cell. 2020 Nov 09. pii: S1534-5807(20)30797-8. [Epub ahead of print]55(3): 253-254
    Puschmann R, Loewith R.
      In this issue of Developmental Cell, Yang et al. (2020) report that both nutrient- and growth factor-dependent signaling impinge upon the RAG GTPases which in turn control TSC residency time on the lysosome membrane and ultimately mTORC1 activity.
    DOI:  https://doi.org/10.1016/j.devcel.2020.10.007
  19. Science. 2020 Nov 13. 370(6518): 853-856
    Lamper AM, Fleming RH, Ladd KM, Lee ASY.
      Shutoff of global protein synthesis is a conserved response to cellular stresses. This general phenomenon is accompanied by the induction of distinct gene programs tailored to each stress. Although the mechanisms driving repression of general protein synthesis are well characterized, how cells reprogram the translation machinery for selective gene expression remains poorly understood. Here, we found that the noncanonical 5' cap-binding protein eIF3d was activated in response to metabolic stress in human cells. Activation required reduced CK2-mediated phosphorylation near the eIF3d cap-binding pocket. eIF3d controls a gene program enriched in factors important for glucose homeostasis, including members of the mammalian target of rapamycin (mTOR) pathway. eIF3d-directed translation adaptation was essential for cell survival during chronic glucose deprivation. Thus, this mechanism of translation reprogramming regulates the cellular response to metabolic stress.
    DOI:  https://doi.org/10.1126/science.abb0993
  20. Eur J Med Chem. 2020 Oct 24. pii: S0223-5234(20)30938-7. [Epub ahead of print] 112966
    Leser C, Keller M, Gerndt S, Urban N, Chen CC, Schaefer M, Grimm C, Bracher F.
      The members of the TRPML subfamily of non-selective cation channels (TRPML1-3) are involved in the regulation of important lysosomal and endosomal functions, and mutations in TRPML1 are associated with the neurodegenerative lysosomal storage disorder mucolipidosis type IV. For in-depth investigation of functions and (patho)physiological roles of TRPMLs, membrane-permeable chemical tools are urgently needed. But hitherto only two TRPML inhibitors, ML-SI1 and ML-SI3, have been published, albeit without clear information about stereochemical details. In this investigation we developed total syntheses of both inhibitors. ML-SI1 was only obtained as a racemic mixture of inseparable diastereomers and showed activator-dependent inhibitory activity. The more promising tool is ML-SI3, hence ML-SI1 was not further investigated. For ML-SI3 we confirmed by stereoselective synthesis that the trans-isomer is significantly more active than the cis-isomer. Separation of the enantiomers of trans-ML-SI3 further revealed that the (-)-isomer is a potent inhibitor of TRPML1 and TRPML2 (IC50 values 1.6 and 2.3 μM) and a weak inhibitor (IC50 12.5 μM) of TRPML3, whereas the (+)-enantiomer is an inhibitor on TRPML1 (IC50 5.9 μM), but an activator on TRPML 2 and 3. This renders the pure (-)-trans-ML-SI3 more suitable as a chemical tool for the investigation of TRPML1 and 2 than the racemate. The analysis of 12 analogues of ML-SI3 gave first insights into structure-activity relationships in this chemotype, and showed that a broad variety of modifications in both the N-arylpiperazine and the sulfonamide moiety is tolerated. An aromatic analogue of ML-SI3 showed an interesting alternative selectivity profile (strong inhibitor of TRPML1 and strong activator of TRPML2).
    Keywords:  Channel blocker; Indoline; N-arylpiperazine; Stereoselective synthesis; TRPML calcium Channels
    DOI:  https://doi.org/10.1016/j.ejmech.2020.112966
  21. Mol Biol Cell. 2020 Nov 11. mbcE20060356
    Brumfield A, Chaudhary N, Molle D, Wen J, Graumann J, McGraw TE.
      Insulin controls glucose uptake into muscle and fat cells by inducing a net redistribution of GLUT4 from intracellular storage to the plasma membrane (PM). The TBC1D4-RAB10 signaling module is required for insulin-stimulated GLUT4 translocation to the PM, although where it intersects GLUT4 traffic was unknown. Here we demonstrate that TBC1D4-RAB10 functions to control GLUT4 mobilization from a Trans Golgi Network (TGN) storage compartment, establishing that insulin, in addition to regulating the PM proximal effects of GLUT4-containing vesicles docking to and fusion with the PM, also directly regulates the behavior of GLUT4 deeper within the cell. We also show that GLUT4 is retained in an element/domain of the TGN from which newly synthesized lysosomal proteins are targeted to the late endosomes and the ATP7A copper transporter is translocated to the PM by elevated copper. Insulin does not mobilize ATP7A nor does copper mobilize GLUT4, and RAB10 is not required for copper-elicited ATP7A mobilization. Consequently, GLUT4 intracellular sequestration and mobilization by insulin is achieved, in part, through utilizing a region of the TGN devoted to specialized cargo transport in general rather than being specific for GLUT4. Our results define the GLUT4-containing region of the TGN as a sorting and storage site from which different cargo are mobilized by distinct signals through unique molecular machinery.
    DOI:  https://doi.org/10.1091/mbc.E20-06-0356
  22. Cell Rep. 2020 Nov 10. pii: S2211-1247(20)31367-X. [Epub ahead of print]33(6): 108378
    Christiano R, Arlt H, Kabatnik S, Mejhert N, Lai ZW, Farese RV, Walther TC.
      Protein degradation is mediated by an expansive and complex network of protein modification and degradation enzymes. Matching degradation enzymes with their targets and determining globally which proteins are degraded by the proteasome or lysosome/vacuole have been a major challenge. Furthermore, an integrated view of protein degradation for cellular pathways has been lacking. Here, we present an analytical platform that combines systematic gene deletions with quantitative measures of protein turnover to deconvolve protein degradation pathways for Saccharomyces cerevisiae. The resulting turnover map (T-MAP) reveals target candidates of nearly all E2 and E3 ubiquitin ligases and identifies the primary degradation routes for most proteins. We further mined this T-MAP to identify new substrates of ER-associated degradation (ERAD) involved in sterol biosynthesis and to uncover regulatory nodes for sphingolipid biosynthesis. The T-MAP approach should be broadly applicable to the study of other cellular processes, including mammalian systems.
    Keywords:  E2; E3 ligases; ERAD; SILAC; mass spectrometry; proteasome; protein turnover; proteomics; ubiquitin
    DOI:  https://doi.org/10.1016/j.celrep.2020.108378
  23. Eur J Hum Genet. 2020 Nov 08.
    Niño MY, Wijgerde M, de Faria DOS, Hoogeveen-Westerveld M, Bergsma AJ, Broeders M, van der Beek NAME, van den Hout HJM, van der Ploeg AT, Verheijen FW, Pijnappel WWMP.
      Pompe disease is a lysosomal and neuromuscular disorder caused by deficiency of acid alpha-glucosidase (GAA), and causes classic infantile, childhood onset, or adulthood onset phenotypes. The biochemical diagnosis is based on GAA activity assays in dried blood spots, leukocytes, or fibroblasts. Diagnosis can be complicated by the existence of pseudodeficiencies, i.e., GAA variants that lower GAA activity but do not cause Pompe disease. A large-scale comparison between these assays for patient samples, including exceptions and borderline cases, along with clinical diagnoses has not been reported so far. Here we analyzed GAA activity in a total of 1709 diagnostic cases over the past 28 years using a total of 2591 analyses and we confirmed the clinical diagnosis in 174 patients. We compared the following assays: leukocytes using glycogen or 4MUG as substrate, fibroblasts using 4MUG as substrate, and dried blood spots using 4MUG as substrate. In 794 individuals, two or more assays were performed. We found that phenotypes could only be distinguished using fibroblasts with 4MUG as substrate. Pseudodeficiencies caused by the GAA2 allele could be ruled out using 4MUG rather than glycogen as substrate in leukocytes or fibroblasts. The Asian pseudodeficiency could only be ruled out in fibroblasts using 4MUG as substrate. We conclude that fibroblasts using 4MUG as substrate provides the most reliable assay for biochemical diagnosis and can serve to validate results from leukocytes or dried blood spots.
    DOI:  https://doi.org/10.1038/s41431-020-00752-2
  24. Elife. 2020 Nov 12. pii: e58069. [Epub ahead of print]9
    Zhang C, Hao C, Shui G, Li W.
      Low-density lipoprotein receptor (LDLR) in hepatocytes plays a key role in normal clearance of circulating LDL and in whole body cholesterol homeostasis. The trafficking of LDLR is highly regulated in clathrin-dependent endocytosis, endosomal recycling and lysosomal degradation. Current studies focus on its endocytosis and degradation. However, the detailed molecular and cellular mechanisms underlying its endosomal recycling are largely unknown. We found that BLOS1, a shared subunit of BLOC-1 and BORC, is involved in LDLR endosomal recycling. Loss of BLOS1 leads to less membrane LDLR and impairs LDL clearance from plasma in hepatocyte-specific BLOS1 knockout mice. BLOS1 interacts with kinesin-3 motor KIF13A, and BLOS1 acts as a new adaptor for kinesin-2 motor KIF3 to coordinate kinesin-3 and kinesin-2 during the long-range transport of recycling endosomes (REs) to plasma membrane along microtubule tracks to overcome hurdles at microtubule intersections. This provides new insights into RE's anterograde transport and the pathogenesis of dyslipidemia.
    Keywords:  cell biology; mouse
    DOI:  https://doi.org/10.7554/eLife.58069
  25. Biogerontology. 2020 Nov 07.
    Yee Z, Lim SHY, Ng LF, Gruber J.
      Aging animals accumulate insoluble proteins as a consequence of a decline of proteostatic maintenance with age. In Caenorhabditis elegans, for instance, levels of detergent-insoluble proteins increase with age. In longer-lived strains of C. elegans, this accumulation occurs more slowly, implying a link to lifespan determination. We further explored this link and found that detergent-insoluble proteins accumulate more rapidly at higher temperatures, a condition where lifespan is short. We employed a C. elegans strain carrying a GFP transcriptional reporter under the control of a heat shock (hsp-16.2) promoter to investigate the dynamics of proteostatic failure in individual nematodes. We found that early, sporadic activation of hsp-16.2 was predictive of shorter remaining lifespan in individual nematodes. Exposure to rapamycin, resulting in reduced mTOR signaling, delayed spurious expression, extended lifespan, and delayed accumulation of insoluble proteins, suggesting that targets downstream of the mTOR pathway regulate the accumulation of insoluble proteins. We specifically explored ribosomal S6 kinase (rsks-1) as one such candidate and found that RNAi against rsks-1 also resulted in less age-dependent accumulation of insoluble proteins and extended lifespan. Our results demonstrate that inhibition of protein translation via reduced mTOR signaling resulted in slower accumulation of insoluble proteins, delayed proteostatic crisis, and extended lifespan in C. elegans.
    Keywords:  Aging; C. elegans; Heat shock protein; Insoluble proteins; Proteostasis; mTOR
    DOI:  https://doi.org/10.1007/s10522-020-09906-7
  26. Mov Disord Clin Pract. 2020 Nov;7(8): 961-964
    Wu M, Ceponiene R, Bayram E, Litvan I.
      Background: Niemann-Pick disease type C (NPC) is a rare, autosomal recessive lysosomal lipid storage disorder. It may present with cerebellar ataxia, vertical supranuclear gaze palsy, and cognitive impairment, and the age of symptom onset in adult-onset NPC is usually earlier than the fourth decade.Cases: We present 2 patients with adult-onset NPC diagnosed in the seventh decade of life. The slow motor progression and subtle findings of supranuclear vertical gaze palsy and ataxia can lead to a delayed diagnosis and misdiagnosis with parkinsonian disorders, particularly progressive supranuclear palsy.
    Conclusion: This report highlights and differentiates key clinical characteristics between NPC and parkinsonian disorders. It is important to consider NPC in the differential diagnosis when patients present with slowed vertical saccades, vertical supranuclear gaze palsy, ataxia, and cognitive impairment present at any age. This will allow appropriate and prompt treatment with miglustat and novel experimental therapies.
    Keywords:  Niemann‐Pick disease type C, adult‐onset, differential diagnosis, supranuclear vertical gaze palsy
    DOI:  https://doi.org/10.1002/mdc3.13085
  27. Elife. 2020 11 10. pii: e55994. [Epub ahead of print]9
    Gnanapradeepan K, Leu JI, Basu S, Barnoud T, Good M, Lee JV, Quinn WJ, Kung CP, Ahima R, Baur JA, Wellen KE, Liu Q, Schug ZT, George DL, Murphy ME.
      The Pro47Ser variant of p53 (S47) exists in African-descent populations and is associated with increased cancer risk in humans and mice. Due to impaired repression of the cystine importer Slc7a11, S47 cells show increased glutathione (GSH) accumulation compared to cells with wild -type p53. We show that mice containing the S47 variant display increased mTOR activity and oxidative metabolism, as well as larger size, improved metabolic efficiency, and signs of superior fitness. Mechanistically, we show that mTOR and its positive regulator Rheb display increased association in S47 cells; this is due to an altered redox state of GAPDH in S47 cells that inhibits its ability to bind and sequester Rheb. Compounds that decrease glutathione normalize GAPDH-Rheb complexes and mTOR activity in S47 cells. This study reveals a novel layer of regulation of mTOR by p53, and raises the possibility that this variant may have been selected for in early Africa.
    Keywords:  GAPDH; Pro47Ser; Rheb; cancer biology; human; mTOR; metabolism; mouse; p53
    DOI:  https://doi.org/10.7554/eLife.55994
  28. FASEB J. 2020 Nov 13.
    Wei Z, Du Q, Li P, Liu H, Xia M, Chen Y, Bi G, Tang ZH, Cheng X, Lu Y, He R, Laurence A, Wang J, Huang L, Li H, Yang XP.
      Appropriate migration of cytotoxic T effector cells into the tumors is crucial for their antitumor function. Despite the controversial role of PI3K-Akt in CD8+ T cell mTORC1 activation, a link between Akt-mTORC1 signaling and CD8+ trafficking has been demonstrated. We have recently discovered that TCR-induced calcineurin activates DAPK1, which interacts with TSC2 via its death domain and phosphorylates TSC2 via its kinase domain to mediate mTORC1 activation in CD8+ T cells. However, whether DAPK1 regulates CD8+ trafficking into tumors remains unclear. Here, using pharmacological inhibitor and genetic approaches, we found that like rapamycin, inhibition of DAPK1 activity led to enhanced expression of the homing receptors CD62L and CCR7. Deletion of either kinase domain or death domain in the T cell compartment reduced the T cell activation and maintained the expression of CD62L and CCR7. DAPK1-DD-deficient mice were more susceptible to tumor growth and deficiency of DAPK1 activity significantly reduced the migratory ability of CD8+ into the tumors. These data revealed a crucial role of DAPK1-mTORC1 in mediating CD8+ trafficking and antitumor function.
    Keywords:  Akt; CD8+ T cells; DAPK1; mTORC1; trafficking
    DOI:  https://doi.org/10.1096/fj.201903067RR
  29. Proc Natl Acad Sci U S A. 2020 Nov 10. pii: 202010723. [Epub ahead of print]
    Zhang H, Zoued A, Liu X, Sit B, Waldor MK.
      Organelle remodeling is critical for cellular homeostasis, but host factors that control organelle function during microbial infection remain largely uncharacterized. Here, a genome-scale CRISPR/Cas9 screen in intestinal epithelial cells with the prototypical intracellular bacterial pathogen Salmonella led us to discover that type I IFN (IFN-I) remodels lysosomes. Even in the absence of infection, IFN-I signaling modified the localization, acidification, protease activity, and proteomic profile of lysosomes. Proteomic and genetic analyses revealed that multiple IFN-I-stimulated genes including IFITM3, SLC15A3, and CNP contribute to lysosome acidification. IFN-I-dependent lysosome acidification was associated with elevated intracellular Salmonella virulence gene expression, rupture of the Salmonella-containing vacuole, and host cell death. Moreover, IFN-I signaling promoted in vivo Salmonella pathogenesis in the intestinal epithelium where Salmonella initiates infection, indicating that IFN-I signaling can modify innate defense in the epithelial compartment. We propose that IFN-I control of lysosome function broadly impacts host defense against diverse viral and microbial pathogens.
    Keywords:  Salmonella pathogenesis; intestinal epithelium; lysosome; mucosal defense; type I interferon
    DOI:  https://doi.org/10.1073/pnas.2010723117
  30. Acta Pharm Sin B. 2020 Oct;10(10): 1880-1903
    Alu A, Han X, Ma X, Wu M, Wei Y, Wei X.
      Lysosome is a ubiquitous acidic organelle fundamental for the turnover of unwanted cellular molecules, particles, and organelles. Currently, the pivotal role of lysosome in regulating cell death is drawing great attention. Over the past decades, we largely focused on how lysosome influences apoptosis and autophagic cell death. However, extensive studies showed that lysosome is also prerequisite for the execution of regulated necrosis (RN). Different types of RN have been uncovered, among which, necroptosis, ferroptosis, and pyroptosis are under the most intensive investigation. It becomes a hot topic nowadays to target RN as a therapeutic intervention, since it is important in many patho/physiological settings and contributing to numerous diseases. It is promising to target lysosome to control the occurrence of RN thus altering the outcomes of diseases. Therefore, we aim to give an introduction about the common factors influencing lysosomal stability and then summarize the current knowledge on the role of lysosome in the execution of RN, especially in that of necroptosis, ferroptosis, and pyroptosis.
    Keywords:  Ferroptosis; Lysosome; Necroptosis; Pyroptosis; Regulated necrosis
    DOI:  https://doi.org/10.1016/j.apsb.2020.07.003
  31. Cell Death Dis. 2020 Nov 12. 11(11): 976
    Cui D, Dai X, Gong L, Chen X, Wang L, Xiong X, Zhao Y.
      DEP-domain containing mTOR-interacting protein (DEPTOR), a natural mTOR inhibitor, has essential roles in several processes, including cell growth, metabolism, apoptosis, and immunity. DEPTOR expression has been shown to be diversely controlled at transcriptional levels in cell- and context-specific manners. However, whether there is a general mechanism for the regulation of DEPTOR expression remains largely unknown. Here, we report that DEPTOR is a downstream target of the tumor suppressor, p53, whose activity is positively correlated with DEPTOR expression both in vitro in cell cultures and in vivo in mouse tissues. Mechanistically, p53 directly binds to the DEPTOR promoter and transactivates its expression. Depletion of the p53-binding site on the DEPTOR promoter by CRISPR-Cas9 technology decreases DEPTOR expression and promotes cell proliferation and survival by activating AKT signaling. Importantly, inhibition of AKT by small molecular inhibitors or genetic knockdown abrogates the induction of cell growth and survival induced by deletion of the p53-binding region on the DEPTOR promoter. Furthermore, p53, upon activation by the genotoxic agent doxorubicin, induces DEPTOR expression, leading to cancer cell resistance to doxorubicin. Together, DEPTOR is a direct p53 downstream target and contributes to p53-mediated inhibition of cell proliferation, survival, and chemosensitivity.
    DOI:  https://doi.org/10.1038/s41419-020-03185-3
  32. Circulation. 2020 Nov 13.
    Simon JN, Vrellaku B, Monterisi S, Chu SM, Rawlings N, Lomas O, Marchal GA, Waithe D, Syeda F, Gajendragadkar PR, Jayaram R, Sayeed R, Channon KM, Fabritz L, Swietach P, Zaccolo M, Eaton P, Casadei B.
      Background: Kinase oxidation is a critical signalling mechanism through which changes in the intracellular redox state alter cardiac function. In the myocardium, type-1 protein kinase A (PKARIα) can be reversibly oxidized, forming interprotein disulfide bonds within the holoenzyme complex. However, the effect of PKARIα disulfide formation on downstream signaling in the heart, particularly under states of oxidative stress such as ischemia and reperfusion (I/R), remains unexplored. Methods: Atrial tissue obtained from patients before and after cardiopulmonary bypass and reperfusion and left ventricular (LV) tissue from mice subjected to I/R or sham surgery were used to assess PKARIα disulfide formation by immunoblot. To determine the impact of disulfide formation on PKARIα catalytic activity and sub-cellular localization, live-cell fluorescence imaging and stimulated emission depletion super-resolution microscopy were performed in prkar1 knock-out mouse embryonic fibroblasts, neonatal myocytes or adult LV myocytes isolated from 'redox dead' (Cys17Ser) PKARIα knock-in mice and their wild-type littermates. Comparison of intracellular calcium dynamics between genotypes was assessed in fura2-loaded LV myocytes whereas I/R-injury was assessed ex vivo. Results: In both humans and mice, myocardial PKARIα disulfide formation was found to be significantly increased (2-fold in humans, p=0.023; 2.4-fold in mice, p<0.001) in response to I/R in vivo. In mouse LV cardiomyocytes, disulfide-containing PKARIα was not found to impact catalytic activity, but instead led to enhanced A-kinase-anchoring protein (AKAP) binding with preferential localization of the holoenzyme to the lysosome. Redox-dependent regulation of lysosomal two pore channels (TPC) by PKARIα was sufficient to prevent global calcium release from the sarcoplasmic reticulum in LV myocytes, without affecting intrinsic ryanodine receptor leak or phosphorylation. Absence of I/R-induced PKARIα disulfide formation in "redox dead" knock-in mouse hearts resulted in larger infarcts (2-fold, p<0.001) and a concomitant reduction in LV contractile recovery (1.6-fold, p<0.001), which was prevented by administering the lysosomal TPC inhibitor Ned-19 at the time of reperfusion. Conclusions: Disulfide-modification targets PKARIα to the lysosome where it acts as a gatekeeper for TPC-mediated triggering of global calcium release. In the post-ischemic heart, this regulatory mechanism is critical for protecting from extensive injury and offers a novel target for the design of cardioprotective therapeutics.
    DOI:  https://doi.org/10.1161/CIRCULATIONAHA.120.046761
  33. Dev Cell. 2020 Nov 09. pii: S1534-5807(20)30796-6. [Epub ahead of print]55(3): 298-313.e10
    Dermit M, Dodel M, Lee FCY, Azman MS, Schwenzer H, Jones JL, Blagden SP, Ule J, Mardakheh FK.
      Translation of ribosomal protein-coding mRNAs (RP-mRNAs) constitutes a key step in ribosome biogenesis, but the mechanisms that modulate RP-mRNA translation in coordination with other cellular processes are poorly defined. Here, we show that subcellular localization of RP-mRNAs acts as a key regulator of their translation during cell migration. As cells migrate into their surroundings, RP-mRNAs localize to the actin-rich cell protrusions. This localization is mediated by La-related protein 6 (LARP6), an RNA-binding protein that is enriched in protrusions. Protrusions act as hotspots of translation for RP-mRNAs, enhancing RP synthesis, ribosome biogenesis, and the overall protein synthesis in migratory cells. In human breast carcinomas, epithelial-to-mesenchymal transition (EMT) upregulates LARP6 expression to enhance protein synthesis and support invasive growth. Our findings reveal LARP6-mediated mRNA localization as a key regulator of ribosome biogenesis during cell migration and demonstrate a role for this process in cancer progression downstream of EMT.
    Keywords:  EMT; LARP6; La-related proteins; RNA localization; cancer; invasion; protrusion; ribosomal proteins; ribosome biogenesis
    DOI:  https://doi.org/10.1016/j.devcel.2020.10.006
  34. FASEB J. 2020 Nov 13.
    Yang L, Wu Y, Lin S, Dai B, Chen H, Tao X, Li G, Wan J, Pan Y.
      Secretory phospholipase A2 group IB (sPLA2-IB) and M-type phospholipase A2 receptor (PLA2R) are closely associated with proteinuria in idiopathic membranous nephropathy (IMN). Podocytes constitute an important component of glomerular filtration, and high basal autophagy is indispensable for podocyte function. The current study aimed to analyze the relationship between sPLA2-IB and podocyte autophagy in IMN and determine whether sPLA2-IB mediates abnormal autophagy regulation in podocytes. The serum sPLA2-IB level and podocyte autophagy were detected, and clinical data were collected from IMN patients with different proteinuria levels. Then, the effects of sPLA2-IB on autophagy signaling pathways were evaluated in cultured human podocytes treated with sPLA2-IB, rapamycin, p38 inhibition, and PLA2R-siRNA in vitro. We found that IMN patients with nephrotic-range proteinuria have a significantly higher level of sPLA2-IB and fewer autophagosomes than those with non-nephrotic-range proteinuria. In vitro sPLA2-IB-induced insufficient autophagy in podocytes and promoted podocyte injury via activation of the mTOR/ULK1ser757 signaling pathway. Moreover, inhibition of p38 MAPK evidently abrogated sPLA2-IB-induced autophagy and the activation of mTOR/ULK1ser757 . Additionally, PLA2R silencing demonstrated that sPLA2-IB-induced abnormal autophagy was also PLA2R-dependent. In conclusion, the results revealed that sPLA2-IB downregulated autophagy and contributed to podocyte injury via PLA2R though activation of the p38MAPK/mTOR/ULK1ser757 signaling pathway.
    Keywords:  PLA2R; idiopathic membranous nephropathy; podocyte autophagy; sPLA2-IB
    DOI:  https://doi.org/10.1096/fj.202001143R
  35. Nat Commun. 2020 Nov 13. 11(1): 5772
    Lee CH, Song DK, Park CB, Choi J, Kang GM, Shin SH, Kwon I, Park S, Kim S, Kim JY, Dugu H, Park JW, Choi JH, Min SH, Sohn JW, Kim MS.
      Hypothalamic neurons including proopiomelanocortin (POMC)-producing neurons regulate body weights. The non-motile primary cilium is a critical sensory organelle on the cell surface. An association between ciliary defects and obesity has been suggested, but the underlying mechanisms are not fully understood. Here we show that inhibition of ciliogenesis in POMC-expressing developing hypothalamic neurons, by depleting ciliogenic genes IFT88 and KIF3A, leads to adulthood obesity in mice. In contrast, adult-onset ciliary dysgenesis in POMC neurons causes no significant change in adiposity. In developing POMC neurons, abnormal cilia formation disrupts axonal projections through impaired lysosomal protein degradation. Notably, maternal nutrition and postnatal leptin surge have a profound impact on ciliogenesis in the hypothalamus of neonatal mice; through these effects they critically modulate the organization of hypothalamic feeding circuits. Our findings reveal a mechanism of early life programming of adult adiposity, which is mediated by primary cilia in developing hypothalamic neurons.
    DOI:  https://doi.org/10.1038/s41467-020-19638-4
  36. Gene. 2020 Oct 22. pii: S0378-1119(20)30930-6. [Epub ahead of print] 145261
    Yao X, Chen H, Xu B, Lu J, Gu J, Chen F, Ju M, Sun X.
      Radiotherapy is one of the primary therapeutic modalities for patients diagnosed esophageal squamous cell carcinoma(ESCC). Previous studies have shown that chemotherapy resistance could be linked with the overexpression vascular ATPases(V-ATPase) subunits genes. However, it is unknown whether V-ATPase subunits genes play a role in radiotherapy resistance. The aim of this study was to investigate the effect of the ATP6V1C1 in radiotherapy resistance. siRNA and plasmids were used to transfect low expression of ATP6V1C1 in TE13 (human ESCC cell) and high expressed in ECA109 (human ESCC cell), respectively. To observe proliferation, radiosensitivity, apoptosis and DNA-damage response, colony formation assays, EDU assays, flow cytometry and γH2AX assay were used with or without radiation exposure, separately. The quantities of the autophagosomes and autolysosomes by immunofluorescence were calculated. Autophagic microstructure were discovered by transmission electron microscopy, and the study also repeated in vivo by nude mice. Western blot assay was applied to prove changes in relative proteins. We found that suppressing ATP6V1C1 increased the sensitivity of ESCC cells after RT. Silencing ATP6V1C1 with IR suppressed the tumor growth and promoted autophagy. Besides, the underlying mechanism of ATP6V1C1, which is not fatally disrupted, is that ATP6V1C1 with ionizing radiation (IR)decreased apoptosis and inhibited autophagy may by activating mTOR signaling to suppress radiosensitivity for ESCC cells. Thus, we first reported that the ATP6V1C1 may represent a potential radiotherapeutic target by effect on radiation sensitivity for ESCC.
    Keywords:  Autophagy; Esophageal squamous cell carcinoma; Ionizing radiation; Radiosensitivity; V-ATPase
    DOI:  https://doi.org/10.1016/j.gene.2020.145261