bims-lysosi 2021-08-15 papers

bims-lysosi

Biomed News

on Lysosomes and signaling

Issue of 2021–08–15
thirty-two papers selected by
Stephanie Fernandes, Max Planck Institute for Biology of Ageing

Lamin regulates the dietary restriction response via the mTOR pathway in Caenorhabditis elegans.
Lipotoxicity-induced STING1 activation stimulates MTORC1 and restricts hepatic lipophagy.
Glial contribution to cyclodextrin-mediated reversal of cholesterol accumulation in murine NPC1-deficient neurons in vivo.
Who's in control? Principles of Rab GTPase activation in endolysosomal membrane trafficking and beyond.
The zinc finger/RING domain protein Unkempt regulates cognitive flexibility.
MTORC1-dependent crinophagy regulates glucagon content in pancreatic α-cells.
An AMPK-ULK1-PIKFYVE signaling axis for PtdIns5P-dependent autophagy regulation upon glucose starvation.
Chondrocyte Tsc1 controls cranial base bone development by restraining the premature differentiation of synchondroses.
The lysosome as a master regulator of iron metabolism.
The Hippo kinase LATS2 impairs pancreatic β-cell survival in diabetes through the mTORC1-autophagy axis.
Are lysosomes potential therapeutic targets for Parkinson's disease?
ARF GTPases and Their Ubiquitous Role in Intracellular Trafficking Beyond the Golgi.
A neuropathological cell model derived from Niemann-Pick disease type C patient-specific iPSCs shows disruption of the p62/SQSTM1-KEAP1-NRF2 Axis and impaired formation of neuronal networks.
Glycans in autophagy, endocytosis and lysosomal functions.
Deletion of fatty acid amide hydrolase reduces lyso-sulfatide levels but exacerbates metachromatic leukodystrophy in mice.
AMPK-activated ULK1 phosphorylates PIKFYVE to drive formation of PtdIns5P-containing autophagosomes during glucose starvation.
Nicotinamide N-methyltransferase (NNMT) upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes.
Sestrins regulate muscle stem cell metabolic homeostasis.
Metformin Alleviates Hepatic Steatosis and Insulin Resistance in a Mouse Model of High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease by Promoting Transcription Factor EB-Dependent Autophagy.
Two parallel pathways connect glutamine metabolism and mTORC1 activity to regulate glutamoptosis.
SLC15A4 mediates M1-prone metabolic shifts in macrophages and guards immune cells from metabolic stress.
The pathogenesis of mesothelioma is driven by a dysregulated translatome.
Loss of Tsc1 from striatal direct pathway neurons impairs endocannabinoid-LTD and enhances motor routine learning.
Insulin resistance is positively associated with plasma cathepsin D activity in NAFLD patients.
Structure of autoinhibited Akt1 reveals mechanism of PIP3-mediated activation.
Targeting of eIF6-driven translation induces a metabolic rewiring that reduces NAFLD and the consequent evolution to hepatocellular carcinoma.
Molecular basis of mucopolysaccharidosis IVA (Morquio A syndrome): a review and classification of GALNS gene variants and reporting of 68 novel variants.
Glucocerebrosidase Activity is Reduced in Cryopreserved Parkinson's Disease Patient Monocytes and Inversely Correlates with Motor Severity.
Loss of Lysosomal Proteins Progranulin and Prosaposin Associated with Increased Neurofibrillary Tangle Development in Alzheimer Disease.
Interruption of endolysosomal trafficking leads to stroke brain injury.
Organelle Crosstalk Regulators Are Regulated in Diseases, Tumors, and Regulatory T Cells: Novel Classification of Organelle Crosstalk Regulators.
Rheb1 Promotes Glucose-stimulated Insulin Secretion in Human and Mouse β-cells by Upregulating GLUT Expression.

J Cell Sci. 2021 Aug 12. pii: jcs.258428. [Epub ahead of print]

Lamin regulates the dietary restriction response via the mTOR pathway in Caenorhabditis elegans.

Chayki Charar, Sally Metsuyanim-Cohen, Daniel Z Bar.

  Animals subjected to dietary restriction (DR) have reduced body size, low fecundity, slower development, lower fat content and longer life span. We identified lamin as a regulator of multiple dietary restriction phenotypes. Downregulation of lmn-1, the single Caenorhabditis elegans lamin gene, increased animal size and fat content, specifically in DR animals. The LMN-1 protein acts in the mTOR pathway, upstream to RAPTOR and S6K, key component and target of mTOR complex 1 (mTORC1), respectively. DR excludes the mTORC1 activator RAGC-1 from the nucleus. Downregulation of lmn-1 restores RAGC-1 to the nucleus, a necessary step for the activation of the mTOR pathway. These findings further link lamin to metabolic regulation.

Keywords:  Caenorhabditis elegans; Dietary restriction; Lamin; mTOR

DOI:  https://doi.org/10.1242/jcs.258428
Autophagy. 2021 Aug 12. 1-17

Lipotoxicity-induced STING1 activation stimulates MTORC1 and restricts hepatic lipophagy.

Kunpeng Liu, Dongbo Qiu, Xue Liang, Yingqi Huang, Yao Wang, Xin Jia, Kun Li, Jingyuan Zhao, Cong Du, Xiusheng Qiu, Jun Cui, Zhendong Xiao, Yunfei Qin, Qi Zhang.

  Lipid accumulation often leads to lipotoxic injuries to hepatocytes, which can cause nonalcoholic steatohepatitis. The association of inflammation with lipid accumulation in liver tissue has been studied for decades; however, key mechanisms have been identified only recently. In particular, it is still unknown how hepatic inflammation regulates lipid metabolism in hepatocytes. Herein, we found that PA treatment or direct stimulation of STING1 promoted, whereas STING1 deficiency impaired, MTORC1 activation, suggesting that STING1 is involved in PA-induced MTORC1 activation. Mechanistic studies revealed that STING1 interacted with several components of the MTORC1 complex and played an important role in the complex formation of MTORC1 under PA treatment. The involvement of STING1 in MTORC1 activation was dependent on SQSTM1, a key regulator of the MTORC1 pathway. In SQSTM1-deficient cells, the interaction of STING1 with the components of MTORC1 was weak. Furthermore, the impaired activity of MTORC1 via rapamycin treatment or STING1 deficiency decreased the numbers of LDs in cells. PA treatment inhibited lipophagy, which was not observed in STING1-deficient cells or rapamycin-treated cells. Restoration of MTORC1 activity via treatment with amino acids blocked lipophagy and LDs degradation. Finally, increased MTORC1 activation concomitant with STING1 activation was observed in liver tissues of nonalcoholic fatty liver disease patients, which provided clinical evidence for the involvement of STING1 in MTORC1 activation. In summary, we identified a novel regulatory loop of STING1-MTORC1 and explain how hepatic inflammation regulates lipid accumulation. Our findings may facilitate the development of new strategies for clinical treatment of hepatic steatosis.Abbreviations: AA: amino acid; ACTB: actin beta; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; DEPTOR: DEP domain containing MTOR interacting protein; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; FFAs: free fatty acids; GFP: green fluorescent protein; HFD: high-fat diet; HT-DNA: herring testis DNA; IL1B: interleukin 1 beta; LAMP1: lysosomal associated membrane protein 1; LDs: lipid droplets; MAP1LC3: microtubule associated protein 1 light chain 3; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MEFs: mouse embryonic fibroblasts; MLST8: MTOR associated protein, LST8 homolog; MT-ND1: mitochondrially encoded NADH: ubiquinone oxidoreductase core subunit 1; mtDNA: mitochondrial DNA; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NAFL: nonalcoholic fatty liver; NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis; NPCs: non-parenchymal cells; PA: palmitic acid; PLIN2: perilipin 2; RD: regular diet; RELA: RELA proto-oncogene, NF-kB subunit; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase B1; RPTOR: regulatory associated protein of MTOR complex 1; RRAGA: Ras related GTP binding A; RRAGC: Ras related GTP binding C; SQSTM1: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1; TGs: triglycerides; TREX1: three prime repair exonuclease 1.

Keywords:  Lipophagy; MTORC1; NAFLD; STING1; TBK1

DOI:  https://doi.org/10.1080/15548627.2021.1961072
Neurobiol Dis. 2021 Aug 05. pii: S0969-9961(21)00218-7. [Epub ahead of print]158 105469

Glial contribution to cyclodextrin-mediated reversal of cholesterol accumulation in murine NPC1-deficient neurons in vivo.

Amélie Barthelemy, Valérie Demais, Izabela-Cristina Stancu, Eugeniu Vasile, Tom Houben, Michael Reber, Valentina Pallottini, Martine Perraut, Sophie Reibel, Frank W Pfrieger.

  Niemann-Pick type C disease is a rare and fatal lysosomal storage disorder presenting severe neurovisceral symptoms. Disease-causing mutations in genes encoding either NPC1 or NPC2 protein provoke accumulation of cholesterol and other lipids in specific structures of the endosomal-lysosomal system and degeneration of specific cells, notably neurons in the central nervous system (CNS). 2-hydroxypropyl-beta-cyclodextrin (CD) emerged as potential therapeutic approach based on animal studies and clinical data, but the mechanism of action in neurons has remained unclear. To address this topic in vivo, we took advantage of the retina as highly accessible part of the CNS and intravitreal injections as mode of drug administration. Coupling CD to gold nanoparticles allowed us to trace its intracellular location. We report that CD enters the endosomal-lysosomal system of neurons in vivo and enables the release of lipid-laden lamellar inclusions, which are then removed from the extracellular space by specific types of glial cells. Our data suggest that CD induces a concerted action of neurons and glial cells to restore lipid homeostasis in the central nervous system.

Keywords:  Amacrine cells; Astrocytes; Cyclodextrin; Ganglion cells; Inherited metabolic disease; Intravitreal; Lysosome; Microglia; Müller cells; Neutrophil granulocytes

DOI:  https://doi.org/10.1016/j.nbd.2021.105469
J Cell Biol. 2021 Sep 06. pii: e202105120. [Epub ahead of print]220(9):

Who's in control? Principles of Rab GTPase activation in endolysosomal membrane trafficking and beyond.

Ann-Christin Borchers, Lars Langemeyer, Christian Ungermann.

The eukaryotic endomembrane system consists of multiple interconnected organelles. Rab GTPases are organelle-specific markers that give identity to these membranes by recruiting transport and trafficking proteins. During transport processes or along organelle maturation, one Rab is replaced by another, a process termed Rab cascade, which requires at its center a Rab-specific guanine nucleotide exchange factor (GEF). The endolysosomal system serves here as a prime example for a Rab cascade. Along with endosomal maturation, the endosomal Rab5 recruits and activates the Rab7-specific GEF Mon1-Ccz1, resulting in Rab7 activation on endosomes and subsequent fusion of endosomes with lysosomes. In this review, we focus on the current idea of Mon1-Ccz1 recruitment and activation in the endolysosomal and autophagic pathway. We compare identified principles to other GTPase cascades on endomembranes, highlight the importance of regulation, and evaluate in this context the strength and relevance of recent developments in in vitro analyses to understand the underlying foundation of organelle biogenesis and maturation.

DOI: https://doi.org/10.1083/jcb.202105120
Sci Rep. 2021 Aug 11. 11(1): 16299

The zinc finger/RING domain protein Unkempt regulates cognitive flexibility.

Elin Vinsland, Pranetha Baskaran, Simeon R Mihaylov, Carl Hobbs, Hannah Wood, Ihssane Bouybayoune, Kriti Shah, Corinne Houart, Andrew R Tee, Jernej Murn, Cathy Fernandes, Joseph M Bateman.

Correct orchestration of nervous system development is a profound challenge that involves coordination of complex molecular and cellular processes. Mechanistic target of rapamycin (mTOR) signaling is a key regulator of nervous system development and synaptic function. The mTOR kinase is a hub for sensing inputs including growth factor signaling, nutrients and energy levels. Activation of mTOR signaling causes diseases with severe neurological manifestations, such as tuberous sclerosis complex and focal cortical dysplasia. However, the molecular mechanisms by which mTOR signaling regulates nervous system development and function are poorly understood. Unkempt is a conserved zinc finger/RING domain protein that regulates neurogenesis downstream of mTOR signaling in Drosophila. Unkempt also directly interacts with the mTOR complex I component Raptor. Here we describe the generation and characterisation of mice with a conditional knockout of Unkempt (UnkcKO) in the nervous system. Loss of Unkempt reduces Raptor protein levels in the embryonic nervous system but does not affect downstream mTORC1 targets. We also show that nervous system development occurs normally in UnkcKO mice. However, we find that Unkempt is expressed in the adult cerebellum and hippocampus and behavioural analyses show that UnkcKO mice have improved memory formation and cognitive flexibility to re-learn. Further understanding of the role of Unkempt in the nervous system will provide novel mechanistic insight into the role of mTOR signaling in learning and memory.

DOI: https://doi.org/10.1038/s41598-021-95286-y
Autophagy. 2021 Aug 12. 1-2

MTORC1-dependent crinophagy regulates glucagon content in pancreatic α-cells.

Sangam Rajak, Paul M Yen, Rohit A Sinha.

  Hormone synthesis and secretion is a highly regulated process governed by metabolic cues. Although peptide hormone action is largely governed by the rate of its synthesis and secretion by endocrine cells, and the levels of its receptors on the target cells, intracellular degradation of the hormone-containing secretory vesicles by lysosomes (crinophagy) adds an additional layer of regulation. In our recent study, we uncovered the regulatory mechanism governing the crinophagic turnover of GCG (glucagon), a glycoprotein hormone secreted by pancreatic α-cells. Our results showed that inhibition of MTORC1 induces crinophagy-mediated degradation of glucagon and decreases its secretion in response to hypoglycemia. Furthermore, we demonstrated that crinophagy-regulated glucagon turnover does not involve macroautophagy. These results suggest that modulation of crinophagy may serve as a novel therapeutic strategy to regulate hormone secretion in endocrine and metabolic pathologies.

Keywords:  Autophagy; MTORC1; crinophagy; diabetes; glucagon; lysosomes; rapamycin

DOI:  https://doi.org/10.1080/15548627.2021.1961074
Autophagy. 2021 Aug 09. 1-2

An AMPK-ULK1-PIKFYVE signaling axis for PtdIns5P-dependent autophagy regulation upon glucose starvation.

Ying Yang, Daniel J Klionsky.

  Glucose deprivation induces macroautophagy/autophagy primarily through AMPK activation. However, little is known about the exact mechanism of this signaling. A recent study from Dr. David C. Rubinsztein's lab showed that ULK1 is activated by AMPK upon glucose starvation, resulting in the phosphorylation of the lipid kinase PIKFYVE on S1548. The activated PIKFYVE consequently enhances the formation of phosphatidylinositol-5-phosphate (PtdIns5P)-containing autophagosomes, and therefore drives autophagy upregulation. The novel discovery of how ULK1 regulates the non-canonical autophagy signaling (PtdIns5P-dependent autophagy), not only expands our knowledge of autophagy, but also sheds light on therapeutic strategies for curing human disorders, where glucose-induced starvation can play an important role.

Keywords:  Lipid kinase; lysosome; non-canonical autophagy; phosphoinositides; stress

DOI:  https://doi.org/10.1080/15548627.2021.1959240
Bone. 2021 Aug 05. pii: S8756-3282(21)00307-0. [Epub ahead of print] 116142

Chondrocyte Tsc1 controls cranial base bone development by restraining the premature differentiation of synchondroses.

Yuan-Lynn Hsieh, Xiaoxi Wei, Yating Wang, Honghao Zhang, Shuqun Qi, Di Xie, Yuji Mishina, Daniela Mendonça, Nan Hatch, Fei Liu.

  Cranial base bones are formed through endochondral ossification. Synchondroses are growth plates located between cranial base bones that facilitate anterior-posterior growth of the skull. Coordinated proliferation and differentiation of chondrocytes in cranial base synchondroses is essential for cranial base bone growth. Herein, we report that constitutive activation of the mechanistic target of rapamycin complex 1 (mTORC1) signaling via Tsc1 (Tuberous sclerosis 1) deletion in chondrocytes causes abnormal skull development with decreased size and rounded shape. In contrast to decreased anterior-posterior growth of the cranial base, mutant mice also exhibited significant expansion of cranial base synchondroses including the intersphenoid synchondrosis (ISS) and the spheno-occipital synchondrosis (SOS). Cranial base synchondrosis expansion in TSC1-deficient mice was accounted for by expansion in the resting zone due to increased cell number and size without alteration in cell proliferation. Furthermore, our data showed that mTORC1 activity is inhibited in the resting and proliferating zone chondrocytes of wild type mice, and Tsc1 deletion activated mTORC1 signaling of the chondrocytes in the resting zone area. Consequently, the chondrocytes in the resting zone of TSC1-deficient mice acquired characteristics generally attributed to pre-hypertrophic chondrocytes including high mTORC1 activity, increased cell size, and increased expression level of PTH1R (Parathyroid hormone 1 receptor) and IHH (Indian hedgehog). Lastly, treatment with rapamycin, an inhibitor of mTORC1, rescued the abnormality in synchondroses. Our results established an important role for TSC1-mTORC1 signaling in regulating cranial base bone development and showed that chondrocytes in the resting zone of synchondroses are maintained in an mTORC1-inhibitory environment.

Keywords:  ISS; SOS; Tsc1; chondrocyte; cranial base; cranial synchondrosis; endochondral; mTORC1; skull

DOI:  https://doi.org/10.1016/j.bone.2021.116142
Trends Biochem Sci. 2021 Aug 09. pii: S0968-0004(21)00159-6. [Epub ahead of print]

The lysosome as a master regulator of iron metabolism.

Francesca Rizzollo, Sanket More, Peter Vangheluwe, Patrizia Agostinis.

  Intracellular iron fulfills crucial cellular processes, including DNA synthesis and mitochondrial metabolism, but also mediates ferroptosis, a regulated form of cell death driven by lipid-based reactive oxygen species (ROS). Beyond their established role in degradation and recycling, lysosomes occupy a central position in iron homeostasis and integrate metabolic and cell death signals emanating from different subcellular sites. We discuss the central role of the lysosome in preserving iron homeostasis and provide an integrated outlook of the regulatory circuits coupling the lysosomal system to the control of iron trafficking, interorganellar crosstalk, and ferroptosis induction. We also discuss novel studies unraveling how deregulated lysosomal iron-handling functions contribute to cancer, neurodegeneration, and viral infection, and can be harnessed for therapeutic interventions.

Keywords:  cancer; ferroptosis; iron homeostasis; iron trafficking; neurodegenerative diseases; viruses

DOI:  https://doi.org/10.1016/j.tibs.2021.07.003
Nat Commun. 2021 Aug 13. 12(1): 4928

The Hippo kinase LATS2 impairs pancreatic β-cell survival in diabetes through the mTORC1-autophagy axis.

Ting Yuan, Karthika Annamalai, Shruti Naik, Blaz Lupse, Shirin Geravandi, Anasua Pal, Aleksandra Dobrowolski, Jaee Ghawali, Marina Ruhlandt, Kanaka Durga Devi Gorrepati, Zahra Azizi, Dae-Sik Lim, Kathrin Maedler, Amin Ardestani.

Diabetes results from a decline in functional pancreatic β-cells, but the molecular mechanisms underlying the pathological β-cell failure are poorly understood. Here we report that large-tumor suppressor 2 (LATS2), a core component of the Hippo signaling pathway, is activated under diabetic conditions and induces β-cell apoptosis and impaired function. LATS2 deficiency in β-cells and primary isolated human islets as well as β-cell specific LATS2 ablation in mice improves β-cell viability, insulin secretion and β-cell mass and ameliorates diabetes development. LATS2 activates mechanistic target of rapamycin complex 1 (mTORC1), a physiological suppressor of autophagy, in β-cells and genetic and pharmacological inhibition of mTORC1 counteracts the pro-apoptotic action of activated LATS2. We further show a direct interplay between Hippo and autophagy, in which LATS2 is an autophagy substrate. On the other hand, LATS2 regulates β-cell apoptosis triggered by impaired autophagy suggesting an existence of a stress-sensitive multicomponent cellular loop coordinating β-cell compensation and survival. Our data reveal an important role for LATS2 in pancreatic β-cell turnover and suggest LATS2 as a potential therapeutic target to improve pancreatic β-cell survival and function in diabetes.

DOI: https://doi.org/10.1038/s41467-021-25145-x
CNS Neurol Disord Drug Targets. 2021 Aug 09.

Are lysosomes potential therapeutic targets for Parkinson's disease?

A Petese, V Cesaroni, S Cerri, F Blandini.

   BACKGROUND: Parkinson´s disease (PD) is the second most common neurodegenerative disorder, affecting 2-3% of the population over 65 years old. In addition to progressive degeneration of nigrostriatal neurons, the histopathological feature of PD is the accumulation of misfolded α-synuclein protein in abnormal cytoplasmatic inclusions, known as Lewy bodies (LBs). Recently, genome-wide association studies (GWAS) have indicated a clear association of variants within several lysosomal genes with risk for PD. Newly evolving data have been shedding light on the relationship between lysosomal dysfunction and alpha-synuclein aggregation. Defects in lysosomal enzymes could lead to the insufficient clearance of neurotoxic protein materials, possibly leading to selective degeneration of dopaminergic neurons. Specific modulation of lysosomal pathways and their components could be considered a novel opportunity for therapeutic intervention for PD.
AIM: The purpose of this review is to illustrate lysosomal biology and describe the role of lysosomal dysfunction in PD pathogenesis. Finally, the most promising novel therapeutic approaches designed to modulate lysosomal activity, as a potential disease-modifying treatment for PD will be highlighted.

Keywords:  PD GWAS loci; Parkinson's disease; alpha-synuclein; lysosomal pathways; therapeutic approaches

DOI:  https://doi.org/10.2174/1871527320666210809123630
Front Cell Dev Biol. 2021 ;9 679046

ARF GTPases and Their Ubiquitous Role in Intracellular Trafficking Beyond the Golgi.

Petia Adarska, Luis Wong-Dilworth, Francesca Bottanelli.

  Molecular switches of the ADP-ribosylation factor (ARF) GTPase family coordinate intracellular trafficking at all sorting stations along the secretory pathway, from the ER-Golgi-intermediate compartment (ERGIC) to the plasma membrane (PM). Their GDP-GTP switch is essential to trigger numerous processes, including membrane deformation, cargo sorting and recruitment of downstream coat proteins and effectors, such as lipid modifying enzymes. While ARFs (in particular ARF1) had mainly been studied in the context of coat protein recruitment at the Golgi, COPI/clathrin-independent roles have emerged in the last decade. Here we review the roles of human ARF1-5 GTPases in cellular trafficking with a particular emphasis on their roles in post-Golgi secretory trafficking and in sorting in the endo-lysosomal system.

Keywords:  ARF GTPase; COPI; Golgi; TGN; adaptors; clathrin; endosomes; membrane trafficking

DOI:  https://doi.org/10.3389/fcell.2021.679046
Mol Genet Metab Rep. 2021 Sep;28 100784

A neuropathological cell model derived from Niemann-Pick disease type C patient-specific iPSCs shows disruption of the p62/SQSTM1-KEAP1-NRF2 Axis and impaired formation of neuronal networks.

Ryo Saito, Takashi Miyajima, Takeo Iwamoto, Chen Wu, Ken Suzuki, Mohammad Arif Hossain, Miyo Munakata, Takumi Era, Yoshikatsu Eto.

  Niemann-Pick disease type C (NPC) is a rare neurodegenerative disorder caused by a recessive mutation in the NPC1 or NPC2 gene, in which patients exhibit lysosomal accumulation of unesterified cholesterol and glycolipids. Most of the research on NPC has been done in patient-derived skin fibroblasts or mouse models. Therefore, we developed NPC patient neurons derived from induced pluripotent stem cells (iPSCs) to investigate the neuropathological cause of the disease. Although an accumulation of cholesterol and glycolipids, which is characteristic of NPC, was observed in both undifferentiated iPSCs and derived neural stem cells (NSCs), we could not observed the abnormalities in differentiation potential and autophagic activity in such immature cells. However, definite neuropathological features were detected in mature neuronal cells generated from NPC patient-derived iPSCs. Abnormal accumulation of cholesterol and other lipids identified by lipid droplets and number of enlarged lysosomes was more prominent in mature neuronal cells rather than in iPSCs and/or NSCs. Thin-sectioning electron microscopic analysis also demonstrated numerous typical membranous cytoplasmic bodies in mature neuronal cells. Furthermore, TUJ1-positive neurite density was significantly reduced in NPC patient-derived neuronal cells. In addition, disruption of the p62/SQSTM1-KEAP1-NRF2 axis occurred in neurons differentiated from NPC patient-derived iPSCs. These data indicate the impairment of neuronal network formation associated with neurodegeneration in mature neuronal cells derived from patients with NPC.

Keywords:  Cell-based neuropathological model; Induced pluripotent stem cells; Lysosomal storage disorder; Neuronal network density; Niemann−Pick disease type C; p62/SQSTM1−KEAP1−NRF2 axis

DOI:  https://doi.org/10.1016/j.ymgmr.2021.100784
Glycoconj J. 2021 Aug 14.

Glycans in autophagy, endocytosis and lysosomal functions.

Fulvio Reggiori, Hans-Joachim Gabius, Massimo Aureli, Winfried Römer, Sandro Sonnino, Eeva-Liisa Eskelinen.

  Glycans have been shown to function as versatile molecular signals in cells. This prompted us to look at their roles in endocytosis, endolysosomal system and autophagy. We start by introducing the cell biological aspects of these pathways, the concept of the sugar code, and provide an overview on the role of glycans in the targeting of lysosomal proteins and in lysosomal functions. Moreover, we review evidence on the regulation of endocytosis and autophagy by glycans. Finally, we discuss the emerging concept that cytosolic exposure of luminal glycans, and their detection by endogenous lectins, provides a mechanism for the surveillance of the integrity of the endolysosomal compartments, and serves their eventual repair or disposal.

Keywords:  Endolysosomal system; Glycoconjugates; Glycolipids; Glycoproteins; Lectins; Sugar code

DOI:  https://doi.org/10.1007/s10719-021-10007-x
J Biol Chem. 2021 Aug 07. pii: S0021-9258(21)00867-X. [Epub ahead of print] 101064

Deletion of fatty acid amide hydrolase reduces lyso-sulfatide levels but exacerbates metachromatic leukodystrophy in mice.

Claudia Yaghootfam, Bernd Gehrig, Marc Sylvester, Volkmar Gieselmann, Ulrich Matzner.

  An inherited deficiency of arylsulfatase A (ASA) causes the lysosomal storage disease metachromatic leukodystrophy (MLD) characterized by massive intralysosomal storage of the acidic glycosphingolipid sulfatide and progressive demyelination. Lyso-sulfatide, which differs from sulfatide by the lack of the N-linked fatty acid also accumulates in MLD and is considered a key driver of pathology although its concentrations are far below sulfatide levels. However, the metabolic origin of lyso-sulfatide is unknown. We show here that ASA-deficient murine macrophages and microglial cells express an endo-N-deacylase that cleaves the N-linked fatty acid from sulfatide. An ASA-deficient astrocytoma cell line devoid of this activity was used to identify the enzyme by overexpressing 13 deacylases with potentially matching substrate specificities. Hydrolysis of sulfatide was detected only in cells overexpressing the enzyme fatty acid amide hydrolase (FAAH). A cell-free assay with recombinant FAAH confirmed the novel role of this enzyme in sulfatide hydrolysis. Consistent with the in vitro data, deletion of FAAH lowered lyso-sulfatide levels in a mouse model of MLD. Regardless of the established cytotoxicity of lyso-sulfatide and the anti-inflammatory effects of FAAH inhibition seen in mouse models of several neurological diseases, genetic inactivation of FAAH did not mitigate, but rather exacerbated the disease phenotype of MLD mice. This unexpected finding was reflected by worsening of rotarod performance, increase of anxiety-related exploratory activity, aggravation of peripheral neuropathy and reduced life expectancy. Thus, we conclude that FAAH has a protective function in MLD and may represent a novel therapeutic target for treatment of this fatal condition.

Keywords:  Lysosomal storage disease; endo-N-deacylase; fatty acid amide hydrolase; glycospingolipid; lyso-sulfatide; metachromatic leukodystrophy

DOI:  https://doi.org/10.1016/j.jbc.2021.101064
Autophagy. 2021 Aug 12. 1-2

AMPK-activated ULK1 phosphorylates PIKFYVE to drive formation of PtdIns5P-containing autophagosomes during glucose starvation.

Cansu Karabiyik, David C Rubinsztein.

  The induction of macroautophagy/autophagy upon glucose deprivation can occur independently of the PIK3C3/VPS34 complex. Recently, we described a non-canonical signaling pathway involving the kinases AMPK, ULK1 and PIKFYVE that are induced during glucose starvation, leading to the formation of PtdIns5P-containing autophagosomes, resulting in increased autophagy flux and clearance of autophagy substrates. In this cascade, the activation of AMPK leads to ULK1 phosphorylation. ULK1 then phosphorylates PIKFYVE at S1548, leading to its activation and increased PtdIns5P formation, which enables the recruitment of machinery required for autophagosome biogenesis.

Keywords:  AMPK; Autophagy; PIKFYVE; Ptdins5P; ULK1; glucose starvation

DOI:  https://doi.org/10.1080/15548627.2021.1961409
Am J Physiol Cell Physiol. 2021 08 11.

Nicotinamide N-methyltransferase (NNMT) upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes.

Alexandra Griffiths, Jun Wang, Qing Song, Iredia D Iyamu, Lifeng Liu, Jooman Park, Yuwei Jiang, Rong Huang, Zhenyuan Song.

  Defined as the dysfunction and/or cell death caused by toxic lipids accumulation in hepatocytes, hepatic lipotoxicity plays a pathological role in non-alcoholic fatty liver disease. The cellular and molecular mechanisms underlying lipotoxicity remain to be elucidated. In this study, using AML12 cells, a non-transformed murine hepatocyte cell line, exposed to palmitate (a 16-C saturated fatty acid) as an experimental model, we investigated the role and mechanisms of nicotinamide N-methyltransferase (NNMT), a methyltransferase catalyzing nicotinamide methylation and degradation, in hepatic lipotoxicity. We initially identified activating transcription factor 4 (ATF4) as a major transcription factor for hepatic NNMT expression. Here, we demonstrated that palmitate upregulates NNMT expression via activating ATF4 in a mechanistic target of rapamycin complex 1 (mTORC1)-dependent mechanism in that mTORC1 inhibition by both Torin1 and rapamycin attenuated ATF4 activation and NNMT upregulation. We further demonstrated that the mTORC1-dependent ATF4 activation is an integral signaling event of unfolded protein response (UPR) as both ATF4 activation and NNMT upregulation by tunicamycin, a well-documented endoplasmic reticulum (ER) stress inducer, are blunted when hepatocytes were pretreated with Torin1. Importantly, our data uncovered that NNMT upregulation contributes to palmitate-induced hepatotoxicity as NNMT inhibition, via either pharmacological (NNMT inhibitors) or genetic approach (siRNA transfection), provided protection against palmitate lipotoxicity. Our further mechanistic exploration identified protein kinase A (PKA) activation to contribute, at least, partially to the protective effect of NNMT inhibition against lipotoxicity. Collectively, our data demonstrated that NNMT upregulation by the mTORC1-ATF4 pathway activation contributes to the development of lipotoxicity in hepatocytes.

Keywords:  ATF4; Lipotoxicity; NNMT; Palmitate; mTORC1

DOI:  https://doi.org/10.1152/ajpcell.00195.2021
Stem Cell Reports. 2021 Jul 29. pii: S2213-6711(21)00380-5. [Epub ahead of print]

Sestrins regulate muscle stem cell metabolic homeostasis.

Benjamin A Yang, Jesus Castor-Macias, Paula Fraczek, Ashley Cornett, Lemuel A Brown, Myungjin Kim, Susan V Brooks, Isabelle M A Lombaert, Jun Hee Lee, Carlos A Aguilar.

  The health and homeostasis of skeletal muscle are preserved by a population of tissue-resident muscle stem cells (MuSCs) that maintain a state of mitotic and metabolic quiescence in adult tissues. The capacity of MuSCs to preserve the quiescent state declines with aging and metabolic insults, promoting premature activation and stem cell exhaustion. Sestrins are a class of stress-inducible proteins that act as antioxidants and inhibit the activation of the mammalian target of rapamycin complex 1 (mTORC1) signaling complex. Despite these pivotal roles, the role of Sestrins has not been explored in adult stem cells. We show that SESTRIN1,2 loss results in hyperactivation of the mTORC1 complex, increased propensity to enter the cell cycle, and shifts in metabolic flux. Aged SESTRIN1,2 knockout mice exhibited loss of MuSCs and a reduced ability to regenerate injured muscle. These findings demonstrate that Sestrins help maintain metabolic pathways in MuSCs that protect quiescence against aging.

Keywords:  RNA sequencing; aging; mTORC1; metabolism; oxidative stress; reactive oxygen species; regeneration; satellite cells

DOI:  https://doi.org/10.1016/j.stemcr.2021.07.014
Front Pharmacol. 2021 ;12 689111

Metformin Alleviates Hepatic Steatosis and Insulin Resistance in a Mouse Model of High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease by Promoting Transcription Factor EB-Dependent Autophagy.

Dan Zhang, Yicheng Ma, Jianjun Liu, Yi Deng, Bo Zhou, Yu Wen, Mingke Li, Daiyan Wen, Yunyan Ying, Sufeng Luo, Chunjing Shi, Guangyu Pu, Yinglei Miao, Chenggang Zou, Yuanli Chen, Lanqing Ma.

  Nonalcoholic fatty liver disease (NAFLD) results from an abnormal accumulation of lipids within hepatocytes, and is commonly associated with obesity, insulin resistance, and hyperlipidemia. Metformin is commonly used to treat type 2 diabetes mellitus and, in recent years, it was found to play a potential role in the amelioration of NAFLD. However, the mechanisms underlying the protective effect of metformin against NAFLD remain largely unknown. Transcription factor EB (TFEB) is a master transcriptional regulator of lysosomal biogenesis and autophagy and, when activated, is effective against disorders of lipid metabolism. However, the role of TFEB in hepatic steatosis is not well understood. In this report, we demonstrate that the activity of TFEB is reduced in the liver of mice fed a high-fat diet. Metformin treatment significantly reverses the activity of TFEB, and the protective effect of metformin against hepatic steatosis and insulin resistance is dependent on TFEB. We show that metformin-induced autophagy is regulated by TFEB, and our findings reveal that TFEB acts as a mediator, linking metformin with autophagy to reverse NAFLD, and highlight that TFEB may be a promising molecular target for the treatment of NAFLD.

Keywords:  TFEB; autophagy; hepatic steatosis; insulin resistance; metformin; nonalcoholic fatty liver disease

DOI:  https://doi.org/10.3389/fphar.2021.689111
Nat Commun. 2021 08 10. 12(1): 4814

Two parallel pathways connect glutamine metabolism and mTORC1 activity to regulate glutamoptosis.

Clément Bodineau, Mercedes Tomé, Sarah Courtois, Ana S H Costa, Marco Sciacovelli, Benoit Rousseau, Elodie Richard, Pierre Vacher, Carlos Parejo-Pérez, Emilie Bessede, Christine Varon, Pierre Soubeyran, Christian Frezza, Piedad Del Socorro Murdoch, Victor H Villar, Raúl V Durán.

Glutamoptosis is the induction of apoptotic cell death as a consequence of the aberrant activation of glutaminolysis and mTORC1 signaling during nutritional imbalance in proliferating cells. The role of the bioenergetic sensor AMPK during glutamoptosis is not defined yet. Here, we show that AMPK reactivation blocks both the glutamine-dependent activation of mTORC1 and glutamoptosis in vitro and in vivo. We also show that glutamine is used for asparagine synthesis and the GABA shunt to produce ATP and to inhibit AMPK, independently of glutaminolysis. Overall, our results indicate that glutamine metabolism is connected with mTORC1 activation through two parallel pathways: an acute alpha-ketoglutarate-dependent pathway; and a secondary ATP/AMPK-dependent pathway. This dual metabolic connection between glutamine and mTORC1 must be considered for the future design of therapeutic strategies to prevent cell growth in diseases such as cancer.

DOI: https://doi.org/10.1038/s41467-021-25079-4
Proc Natl Acad Sci U S A. 2021 Aug 17. pii: e2100295118. [Epub ahead of print]118(33):

SLC15A4 mediates M1-prone metabolic shifts in macrophages and guards immune cells from metabolic stress.

Toshihiko Kobayashi, Dat Nguyen-Tien, Yuriko Sorimachi, Yuki Sugiura, Takehiro Suzuki, Hitomi Karyu, Shiho Shimabukuro-Demoto, Tatsuki Uemura, Tadashi Okamura, Tomohiko Taguchi, Kohjiro Ueki, Norihiro Kato, Nobuhito Goda, Naoshi Dohmae, Keiyo Takubo, Makoto Suematsu, Noriko Toyama-Sorimachi.

  The amino acid and oligopeptide transporter Solute carrier family 15 member A4 (SLC15A4), which resides in lysosomes and is preferentially expressed in immune cells, plays critical roles in the pathogenesis of lupus and colitis in murine models. Toll-like receptor (TLR)7/9- and nucleotide-binding oligomerization domain-containing protein 1 (NOD1)-mediated inflammatory responses require SLC15A4 function for regulating the mechanistic target of rapamycin complex 1 (mTORC1) or transporting L-Ala-γ-D-Glu-meso-diaminopimelic acid, IL-12: interleukin-12 (Tri-DAP), respectively. Here, we further investigated the mechanism of how SLC15A4 directs inflammatory responses. Proximity-dependent biotin identification revealed glycolysis as highly enriched gene ontology terms. Fluxome analyses in macrophages indicated that SLC15A4 loss causes insufficient biotransformation of pyruvate to the tricarboxylic acid cycle, while increasing glutaminolysis to the cycle. Furthermore, SLC15A4 was required for M1-prone metabolic change and inflammatory IL-12 cytokine productions after TLR9 stimulation. SLC15A4 could be in close proximity to AMP-activated protein kinase (AMPK) and mTOR, and SLC15A4 deficiency impaired TLR-mediated AMPK activation. Interestingly, SLC15A4-intact but not SLC15A4-deficient macrophages became resistant to fluctuations in environmental nutrient levels by limiting the use of the glutamine source; thus, SLC15A4 was critical for macrophage's respiratory homeostasis. Our findings reveal a mechanism of metabolic regulation in which an amino acid transporter acts as a gatekeeper that protects immune cells' ability to acquire an M1-prone metabolic phenotype in inflammatory tissues by mitigating metabolic stress.

Keywords:  amino acid transporter; cytokine; immunometabolism; innate immune cell; macrophage

DOI:  https://doi.org/10.1073/pnas.2100295118
Nat Commun. 2021 Aug 13. 12(1): 4920

The pathogenesis of mesothelioma is driven by a dysregulated translatome.

Stefano Grosso, Alberto Marini, Katarina Gyuraszova, Johan Vande Voorde, Aristeidis Sfakianos, Gavin D Garland, Angela Rubio Tenor, Ryan Mordue, Tanya Chernova, Nobu Morone, Marco Sereno, Claire P Smith, Leah Officer, Pooyeh Farahmand, Claire Rooney, David Sumpton, Madhumita Das, Ana Teodósio, Catherine Ficken, Maria Guerra Martin, Ruth V Spriggs, Xiao-Ming Sun, Martin Bushell, Owen J Sansom, Daniel Murphy, Marion MacFarlane, John P C Le Quesne, Anne E Willis.

Malignant mesothelioma (MpM) is an aggressive, invariably fatal tumour that is causally linked with asbestos exposure. The disease primarily results from loss of tumour suppressor gene function and there are no 'druggable' driver oncogenes associated with MpM. To identify opportunities for management of this disease we have carried out polysome profiling to define the MpM translatome. We show that in MpM there is a selective increase in the translation of mRNAs encoding proteins required for ribosome assembly and mitochondrial biogenesis. This results in an enhanced rate of mRNA translation, abnormal mitochondrial morphology and oxygen consumption, and a reprogramming of metabolic outputs. These alterations delimit the cellular capacity for protein biosynthesis, accelerate growth and drive disease progression. Importantly, we show that inhibition of mRNA translation, particularly through combined pharmacological targeting of mTORC1 and 2, reverses these changes and inhibits malignant cell growth in vitro and in ex-vivo tumour tissue from patients with end-stage disease. Critically, we show that these pharmacological interventions prolong survival in animal models of asbestos-induced mesothelioma, providing the basis for a targeted, viable therapeutic option for patients with this incurable disease.

DOI: https://doi.org/10.1038/s41467-021-25173-7
Cell Rep. 2021 Aug 10. pii: S2211-1247(21)00941-4. [Epub ahead of print]36(6): 109511

Loss of Tsc1 from striatal direct pathway neurons impairs endocannabinoid-LTD and enhances motor routine learning.

Katelyn N Benthall, Katherine R Cording, Alexander H C W Agopyan-Miu, Corinna D Wong, Emily Y Chen, Helen S Bateup.

  Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder that often presents with psychiatric conditions, including autism spectrum disorder (ASD). ASD is characterized by restricted, repetitive, and inflexible behaviors, which may result from abnormal activity in striatal circuits that mediate motor learning and action selection. To test whether altered striatal activity contributes to aberrant motor behaviors in the context of TSC, we conditionally deleted Tsc1 from direct or indirect pathway striatal projection neurons (dSPNs or iSPNs, respectively). We find that dSPN-specific loss of Tsc1 impairs endocannabinoid-mediated long-term depression (eCB-LTD) at cortico-dSPN synapses and strongly enhances corticostriatal synaptic drive, which is not observed in iSPNs. dSPN-Tsc1 KO, but not iSPN-Tsc1 KO, mice show enhanced motor learning, a phenotype observed in several mouse models of ASD. These findings demonstrate that dSPNs are particularly sensitive to Tsc1 loss and suggest that enhanced corticostriatal activation may contribute to altered motor behaviors in TSC.

Keywords:  Tsc1; Tsc2; Tuberous Sclerosis Complex; autism spectrum disorder; corticostriatal synapses; direct pathway; endocannabinoid-LTD; indirect pathway; motor learning; striatum

DOI:  https://doi.org/10.1016/j.celrep.2021.109511
Biomol Concepts. 2021 Aug 09. 12(1): 110-115

Insulin resistance is positively associated with plasma cathepsin D activity in NAFLD patients.

Lingling Ding, Toon J I De Munck, Yvonne Oligschlaeger, Jef Verbeek, Ger H Koek, Tom Houben, Ronit Shiri-Sverdlov.

  Previous studies associated plasma cathepsin D (CTSD) activity with hepatic insulin resistance in overweight and obese humans. Insulin resistance is a major feature of non-alcoholic fatty liver disease (NAFLD) and is one of the multiple hits determining the progression towards non-alcoholic steatohepatitis (NASH). In line, we have previously demonstrated that plasma CTSD levels are increased in NASH patients. However, it is not known whether insulin resistance associates with plasma CTSD activity in NAFLD. To increase our understanding regarding the mechanisms by which insulin resistance mediates NAFLD, fifty-five liver biopsy or MRI-proven NAFLD patients (BMI>25kg/m2) were included to investigate the link between plasma CTSD activity to insulin resistance in NAFLD. We concluded that HOMA-IR and plasma insulin levels are independently associated with plasma CTSD activity in NAFLD patients (standardized coefficient β: 0.412, 95% Cl: 0.142~0.679, p=0.004 and standardized coefficient β: 0.495, 95% Cl: 0.236~0.758, p=0.000, respectively). Together with previous studies, these data suggest that insulin resistance may link to NAFLD via elevation of CTSD activity in plasma. As such, these data pave the way for testing CTSD inhibitors as a pharmacological treatment of NAFLD.

Keywords:  HOMA-IR; Insulin; NAFLD; NASH; lysosomal enzyme; plasma CTSD activity

DOI:  https://doi.org/10.1515/bmc-2021-0011
Proc Natl Acad Sci U S A. 2021 Aug 17. pii: e2101496118. [Epub ahead of print]118(33):

Structure of autoinhibited Akt1 reveals mechanism of PIP3-mediated activation.

Linda Truebestein, Harald Hornegger, Dorothea Anrather, Markus Hartl, Kaelin D Fleming, Jordan T B Stariha, Els Pardon, Jan Steyaert, John E Burke, Thomas A Leonard.

  The protein kinase Akt is one of the primary effectors of growth factor signaling in the cell. Akt responds specifically to the lipid second messengers phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P3] and phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2] via its PH domain, leading to phosphorylation of its activation loop and the hydrophobic motif of its kinase domain, which are critical for activity. We have now determined the crystal structure of Akt1, revealing an autoinhibitory interface between the PH and kinase domains that is often mutated in cancer and overgrowth disorders. This interface persists even after stoichiometric phosphorylation, thereby restricting maximum Akt activity to PI(3,4,5)P3- or PI(3,4)P2-containing membranes. Our work helps to resolve the roles of lipids and phosphorylation in the activation of Akt and has wide implications for the spatiotemporal control of Akt and potentially lipid-activated kinase signaling in general.

Keywords:  Akt; PIP3; kinase; lipid; signaling

DOI:  https://doi.org/10.1073/pnas.2101496118
Nat Commun. 2021 08 12. 12(1): 4878

Targeting of eIF6-driven translation induces a metabolic rewiring that reduces NAFLD and the consequent evolution to hepatocellular carcinoma.

Alessandra Scagliola, Annarita Miluzio, Gabriele Ventura, Stefania Oliveto, Chiara Cordiglieri, Nicola Manfrini, Delia Cirino, Sara Ricciardi, Luca Valenti, Guido Baselli, Roberta D'Ambrosio, Marco Maggioni, Daniela Brina, Alberto Bresciani, Stefano Biffo.

A postprandial increase of translation mediated by eukaryotic Initiation Factor 6 (eIF6) occurs in the liver. Its contribution to steatosis and disease is unknown. In this study we address whether eIF6-driven translation contributes to disease progression. eIF6 levels increase throughout the progression from Non-Alcoholic Fatty Liver Disease (NAFLD) to hepatocellular carcinoma. Reduction of eIF6 levels protects the liver from disease progression. eIF6 depletion blunts lipid accumulation, increases fatty acid oxidation (FAO) and reduces oncogenic transformation in vitro. In addition, eIF6 depletion delays the progression from NAFLD to hepatocellular carcinoma, in vivo. Mechanistically, eIF6 depletion reduces the translation of transcription factor C/EBPβ, leading to a drop in biomarkers associated with NAFLD progression to hepatocellular carcinoma and preserves mitochondrial respiration due to the maintenance of an alternative mTORC1-eIF4F translational branch that increases the expression of transcription factor YY1. We provide proof-of-concept that in vitro pharmacological inhibition of eIF6 activity recapitulates the protective effects of eIF6 depletion. We hypothesize the existence of a targetable, evolutionarily conserved translation circuit optimized for lipid accumulation and tumor progression.

DOI: https://doi.org/10.1038/s41467-021-25195-1
Hum Mutat. 2021 Aug 13.

Molecular basis of mucopolysaccharidosis IVA (Morquio A syndrome): a review and classification of GALNS gene variants and reporting of 68 novel variants.

Alessandra Zanetti, Francesca D'Avanzo, Moeenaldeen AlSayed, Ana Carolina Brusius-Facchin, Yin-Hsiu Chien, Roberto Giugliani, Emanuela Izzo, David C Kasper, Hsiang-Yu Lin, Shuan-Pei Lin, Laura Pollard, Akashdeep Singh, Rodolfo Tonin, Tim Wood, Amelia Morrone, Rosella Tomanin.

  Mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome) is a rare autosomal recessive lysosomal storage disorder caused by mutations in the N-acetylgalactosamine-6-sulfatase (GALNS) gene. We collected, analyzed, and uniformly summarized all published GALNS gene variants, thus updating the previous mutation review by Morrone, et al. 2014. In addition, new variants were communicated by seven reference laboratories in Europe, the Middle East, Latin America, Asia, and the USA. All data were analyzed to determine common alleles, geographic distribution, level of homozygosity, and genotype-phenotype correlation. Moreover, variants were classified according to their pathogenicity as suggested by ACMG. Including those previously published, we assembled 446 unique variants, among which 68 were novel, from 1190 subjects (including newborn screening positive subjects). Variants distribution was missense (65.0%), followed by nonsense (8.1%), splicing (7.2%), small frameshift deletions(del)/insertions(ins) (7.0%), intronic (4.0%), and large del/ins and complex rearrangements (3.8%). Half (50.4%) of the subjects were homozygous, 37.1% were compound heterozygous, and 10.7% had only one variant detected. The novel variants underwent in silico analysis to evaluate their pathogenicity. All variants were submitted to ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/) to make them publicly available. Mutation updates are essential for the correct molecular diagnoses, genetic counselling, prenatal and preimplantation diagnosis, and disease management. This article is protected by copyright. All rights reserved.

Keywords:   GALNS ; MPS IVA; Morquio A syndrome; N-acetylgalactosamine-6-sulfate; lysosomal storage disorder; mucopolysaccharidosis IVA

DOI:  https://doi.org/10.1002/humu.24270
J Parkinsons Dis. 2021 ;11(3): 1157-1165

Glucocerebrosidase Activity is Reduced in Cryopreserved Parkinson's Disease Patient Monocytes and Inversely Correlates with Motor Severity.

Laura P Hughes, Marilia M M Pereira, Deborah A Hammond, John B Kwok, Glenda M Halliday, Simon J G Lewis, Nicolas Dzamko.

   BACKGROUND: Reduced activity of lysosomal glucocerebrosidase is found in brain tissue from Parkinson's disease patients. Glucocerebrosidase is also highly expressed in peripheral blood monocytes where its activity is decreased in Parkinson's disease patients, even in the absence of GBA mutation.
OBJECTIVE: To measure glucocerebrosidase activity in cryopreserved peripheral blood monocytes from 30 Parkinson's disease patients and 30 matched controls and identify any clinical correlation with disease severity.
METHODS: Flow cytometry was used to measure lysosomal glucocerebrosidase activity in total, classical, intermediate, and non-classical monocytes. All participants underwent neurological examination and motor severity was assessed by the Movement Disorders Society Unified Parkinson's Disease Rating Scale.
RESULTS: Glucocerebrosidase activity was significantly reduced in the total and classical monocyte populations from the Parkinson's disease patients compared to controls. GCase activity in classical monocytes was inversely correlated to motor symptom severity.
CONCLUSION: Significant differences in monocyte glucocerebrosidase activity can be detected in Parkinson's disease patients using cryopreserved mononuclear cells and monocyte GCase activity correlated with motor features of disease. Being able to use cryopreserved cells will facilitate the larger multi-site trials needed to validate monocyte GCase activity as a Parkinson's disease biomarker.

Keywords:  Parkinson’s disease; glucocerebrosidase; inflammation; monocyte; toll-like receptor

DOI:  https://doi.org/10.3233/JPD-202508
J Neuropathol Exp Neurol. 2021 Aug 10. pii: nlab056. [Epub ahead of print]

Loss of Lysosomal Proteins Progranulin and Prosaposin Associated with Increased Neurofibrillary Tangle Development in Alzheimer Disease.

Anarmaa Mendsaikhan, Ikuo Tooyama, Geidy E Serrano, Thomas G Beach, Douglas G Walker.

  Alzheimer disease (AD) is a progressive neurodegenerative disease causing cognitive decline in the aging population. To develop disease-modifying treatments, understanding the mechanisms behind the pathology is important, which should include observations using human brain samples. We reported previously on the association of lysosomal proteins progranulin (PGRN) and prosaposin (PSAP) with amyloid plaques in non-demented aged control and AD brains. In this study, we investigated the possible involvement of PGRN and PSAP in tangle formation using human brain tissue sections of non-demented aged control subjects and AD cases and compared with cases of frontotemporal dementia with granulin (GRN) mutations. The study revealed that decreased amounts of PGRN and PSAP proteins were detected even in immature neurofibrillary tangles, while colocalization was still evident in adjacent neurons in all cases. Results suggest that neuronal loss of PGRN preceded loss of PSAP as tangles developed and matured. The GRN mutation cases exhibited almost complete absence of PGRN in most neurons, while PSAP signal was preserved. Although based on correlative data, we suggest that reduced levels of PGRN and PSAP and their interaction in neurons might predispose to accumulation of p-Tau protein.

Keywords:  Alzheimer disease; Neuropathology; Progranulin; Prosaposin; Tangles

DOI:  https://doi.org/10.1093/jnen/nlab056
Exp Neurol. 2021 Aug 04. pii: S0014-4886(21)00235-1. [Epub ahead of print] 113827

Interruption of endolysosomal trafficking leads to stroke brain injury.

Dong Yuan, Kurt Hu, Chun Mun Loke, Hironori Teramoto, Chunli Liu, Bingren Hu.

BACKGROUND AND PURPOSE: Dysfunction of the endolysosomal system can cause cell death. A key molecule for controlling the endolysosomal trafficking activities is the N-ethylmaleimide-sensitive factor (NSF) ATPase. This study investigates the cascades of NSF ATPase inactivation events, endolysosomal damage, cathepsin release, and neuronal death after focal brain ischemia.
METHODS: A total of 62 rats were used in this study. They were subjected to sham surgery or 2 h of focal brain ischemia followed by 1, 4, and 24 h of reperfusion. Confocal microscopy and Western blot analysis were utilized to analyze the levels, redistribution, and co-localization of key proteins of the Golgi apparatus, late endosomes, endolysosomes, and lysosomes. Light and electron microscopy were used to examine the histopathology, protein aggregation, and endolysosomal ultrastructures.
RESULTS: Two hours of focal brain ischemia in rats led to acute neuronal death at the striatal core in 4 h and a slower type of neuronal death in the neocortical area during 1-24 h reperfusion periods. Confocal microscopy showed that NSF immunoreactivity was irreversibly and selectively depleted from most, if not all, post-ischemic penumbral neurons. Western blot analysis further demonstrated that NSF depletion from brain sections was due to its deposition into dense inactive aggregates that could not be recognized by the NSF antibody. Commitantly, the Golgi apparatus was completely fragmented, and cathepsin B (CTSB)-containing endolysosomal structures, as well as p62/SQSTM1- and EEA1-immunopositive structures were massively accumulated in the post-ischemic penumbral neurons. Ultimately, CTSB was released into the cytoplasm and extracellular space, causing stroke brain injury.
CONCLUSION: Stroke Inactivates NSF, resulting in disruption of the reforming of functional endolysosomal compartments, blockade of the endocytic and autophagic pathways, a large scale of CTSB release into the cytoplasm and extracellular space, and stroke brain injury in the rat model.

DOI: https://doi.org/10.1016/j.expneurol.2021.113827
Front Cardiovasc Med. 2021 ;8 713170

Organelle Crosstalk Regulators Are Regulated in Diseases, Tumors, and Regulatory T Cells: Novel Classification of Organelle Crosstalk Regulators.

Ming Liu, Na Wu, Keman Xu, Fatma Saaoud, Eleni Vasilopoulos, Ying Shao, Ruijing Zhang, Jirong Wang, Haitao Shen, William Y Yang, Yifan Lu, Yu Sun, Charles Drummer, Lu Liu, Li Li, Wenhui Hu, Jun Yu, Domenico Praticò, Jianxin Sun, Xiaohua Jiang, Hong Wang, Xiaofeng Yang.

  To examine whether the expressions of 260 organelle crosstalk regulators (OCRGs) in 16 functional groups are modulated in 23 diseases and 28 tumors, we performed extensive -omics data mining analyses and made a set of significant findings: (1) the ratios of upregulated vs. downregulated OCRGs are 1:2.8 in acute inflammations, 1:1 in metabolic diseases, 1:1.2 in autoimmune diseases, and 1:3.8 in organ failures; (2) sepsis and trauma-upregulated OCRG groups such as vesicle, mitochondrial (MT) fission, and mitophagy but not others, are termed as the cell crisis-handling OCRGs. Similarly, sepsis and trauma plus organ failures upregulated seven OCRG groups including vesicle, MT fission, mitophagy, sarcoplasmic reticulum-MT, MT fusion, autophagosome-lysosome fusion, and autophagosome/endosome-lysosome fusion, classified as the cell failure-handling OCRGs; (3) suppression of autophagosome-lysosome fusion in endothelial and epithelial cells is required for viral replications, which classify this decreased group as the viral replication-suppressed OCRGs; (4) pro-atherogenic damage-associated molecular patterns (DAMPs) such as oxidized low-density lipoprotein (oxLDL), lipopolysaccharide (LPS), oxidized-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (oxPAPC), and interferons (IFNs) totally upregulated 33 OCRGs in endothelial cells (ECs) including vesicle, MT fission, mitophagy, MT fusion, endoplasmic reticulum (ER)-MT contact, ER- plasma membrane (PM) junction, autophagosome/endosome-lysosome fusion, sarcoplasmic reticulum-MT, autophagosome-endosome/lysosome fusion, and ER-Golgi complex (GC) interaction as the 10 EC-activation/inflammation-promoting OCRG groups; (5) the expression of OCRGs is upregulated more than downregulated in regulatory T cells (Tregs) from the lymph nodes, spleen, peripheral blood, intestine, and brown adipose tissue in comparison with that of CD4+CD25- T effector controls; (6) toll-like receptors (TLRs), reactive oxygen species (ROS) regulator nuclear factor erythroid 2-related factor 2 (Nrf2), and inflammasome-activated regulator caspase-1 regulated the expressions of OCRGs in diseases, virus-infected cells, and pro-atherogenic DAMP-treated ECs; (7) OCRG expressions are significantly modulated in all the 28 cancer datasets, and the upregulated OCRGs are correlated with tumor immune infiltrates in some tumors; (8) tumor promoter factor IKK2 and tumor suppressor Tp53 significantly modulate the expressions of OCRGs. Our findings provide novel insights on the roles of upregulated OCRGs in the pathogenesis of inflammatory diseases and cancers, and novel pathways for the future therapeutic interventions for inflammations, sepsis, trauma, organ failures, autoimmune diseases, metabolic cardiovascular diseases (CVDs), and cancers.

Keywords:  Treg; cancers and tumors; endothelial cell activation; inflammation; organelle crosstalk; viral infections

DOI:  https://doi.org/10.3389/fcvm.2021.713170
Metabolism. 2021 Aug 07. pii: S0026-0495(21)00163-3. [Epub ahead of print] 154863

Rheb1 Promotes Glucose-stimulated Insulin Secretion in Human and Mouse β-cells by Upregulating GLUT Expression.

Yan Yang, Zixin Cai, Zhenhong Pan, Fen Liu, Dandan Li, Yujiao Ji, Jiaxin Zhong, Hairong Luo, Shanbiao Hu, Lei Song, Shaojie Yu, Ting Li, Jiequn Li, Xianhua Ma, Weiping Zhang, Zhiguang Zhou, Feng Liu, Jingjing Zhang.

Reduced β-cell mass and impaired β-cell function are primary causes of all types of diabetes. However, the intrinsic molecular mechanism that regulates β-cell growth and function remains elusive. Here, we demonstrate that the small GTPase Rheb1 is a critical regulator of glucose-stimulated insulin secretion (GSIS) in β-cells. Rheb1 was highly expressed in mouse and human islets. In addition, β-cell-specific knockout of Rheb1 reduced the β-cell size and mass by suppressing β-cell proliferation and increasing β-cell apoptosis. However, tamoxifen-induced deletion of Rheb1 in β-cells had no significant effect on β-cell mass and size but significantly impaired GSIS. Rheb1 facilitates GSIS in human or mouse islets by upregulating GLUT1 or GLUT2 expression, respectively, in a mTORC1 signaling pathway-dependent manner. Our findings reveal a critical role of Rheb1 in regulating GSIS in β-cells and identified a new target for the therapeutic treatment of diabetes mellitus.

DOI: https://doi.org/10.1016/j.metabol.2021.154863