101
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Fluorescence-Based Assays to Analyse Phosphatidylinositol 5-Phosphate in Autophagy. Methods Enzymol 2017. [PMID: 28253963 DOI: 10.1016/bs.mie.2016.09.062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Autophagosome formation is stimulated by VPS34-dependent PI(3)P formation and by alternative VPS34-independent pathways. We recently described that PI(5)P regulates autophagosome biogenesis and rescues autophagy in VPS34-inactivated cells, suggesting that PI(5)P contributes to canonical autophagy. Our analysis revealed a hitherto unknown functional interplay between PIKfyve and PIPK type II in controlling PI(5)P levels in the context of autophagy. Among phosphoinositides, visualization of PI(5)P in intact cells has remained difficult. While PI(5)P has been implicated in signaling pathways, chromatin organization, bacterial invasion, and cytoskeletal remodeling, our study is the first report showing PI(5)P localization on autophagosomes and early autophagosomal structures when autophagy is induced by nutrient deprivation (amino acids or glucose starvation). We provided a detailed analysis of PI(5)P distribution by the use of super-resolution structured illuminated microscopy. Here, we present a set of tools for detection of PI(5)P during autophagy by confocal microscopy, live-cell imaging, and super-resolution microscopy.
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102
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Lang MJ, Strunk BS, Azad N, Petersen JL, Weisman LS. An intramolecular interaction within the lipid kinase Fab1 regulates cellular phosphatidylinositol 3,5-bisphosphate lipid levels. Mol Biol Cell 2017; 28:858-864. [PMID: 28148651 PMCID: PMC5385934 DOI: 10.1091/mbc.e16-06-0390] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 01/24/2017] [Accepted: 01/24/2017] [Indexed: 11/24/2022] Open
Abstract
There is an intramolecular interaction in the lipid kinase Fab1 in which the upstream CCR domain contacts the Fab1 kinase region. Selected dominant-active alleles disrupt this interaction and result in elevated PI(3,5)P2. These findings suggest a regulatory mechanism that contributes to dynamic control of cellular PI(3,5)P2 synthesis. Phosphorylated phosphoinositide lipids (PPIs) are low-abundance signaling molecules that control signal transduction pathways and are necessary for cellular homeostasis. The PPI phosphatidylinositol (3,5)-bisphosphate (PI(3,5)P2) is essential in multiple organ systems. PI(3,5)P2 is generated from PI3P by the conserved lipid kinase Fab1/PIKfyve. Defects in the dynamic regulation of PI(3,5)P2 are linked to human diseases. However, few mechanisms that regulate PI(3,5)P2 have been identified. Here we report an intramolecular interaction between the yeast Fab1 kinase region and an upstream conserved cysteine-rich (CCR) domain. We identify mutations in the kinase domain that lead to elevated levels of PI(3,5)P2 and impair the interaction between the kinase and CCR domain. We also identify mutations in the CCR domain that lead to elevated levels of PI(3,5)P2. Together these findings reveal a regulatory mechanism that involves the CCR domain of Fab1 and contributes to dynamic control of cellular PI(3,5)P2 synthesis.
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Affiliation(s)
- Michael J Lang
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109.,Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Bethany S Strunk
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Nadia Azad
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Jason L Petersen
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109
| | - Lois S Weisman
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109 .,Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
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103
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Identification of apilimod as a first-in-class PIKfyve kinase inhibitor for treatment of B-cell non-Hodgkin lymphoma. Blood 2017; 129:1768-1778. [PMID: 28104689 DOI: 10.1182/blood-2016-09-736892] [Citation(s) in RCA: 133] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 01/12/2017] [Indexed: 12/15/2022] Open
Abstract
We identified apilimod as an antiproliferative compound by high-throughput screening of clinical-stage drugs. Apilimod exhibits exquisite specificity for phosphatidylinositol-3-phosphate 5-kinase (PIKfyve) lipid kinase and has selective cytotoxic activity in B-cell non-Hodgkin lymphoma (B-NHL) compared with normal cells. Apilimod displays nanomolar activity in vitro, and in vivo studies demonstrate single-agent efficacy as well as synergy with approved B-NHL drugs. Using biochemical and knockdown approaches, and discovery of a kinase domain mutation conferring resistance, we demonstrate that apilimod-mediated cytotoxicity is driven by PIKfyve inhibition. Furthermore, a critical role for lysosome dysfunction as a major factor contributing to apilimod's cytotoxicity is supported by a genome-wide CRISPR screen. In the screen, TFEB (master transcriptional regulator of lysosomal biogenesis) and endosomal/lysosomal genes CLCN7, OSTM1, and SNX10 were identified as important determinants of apilimod sensitivity. These findings thus suggest that disruption of lysosomal homeostasis with apilimod represents a novel approach to treat B-NHL.
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104
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Kim SM, Roy SG, Chen B, Nguyen TM, McMonigle RJ, McCracken AN, Zhang Y, Kofuji S, Hou J, Selwan E, Finicle BT, Nguyen TT, Ravi A, Ramirez MU, Wiher T, Guenther GG, Kono M, Sasaki AT, Weisman LS, Potma EO, Tromberg BJ, Edwards RA, Hanessian S, Edinger AL. Targeting cancer metabolism by simultaneously disrupting parallel nutrient access pathways. J Clin Invest 2016; 126:4088-4102. [PMID: 27669461 PMCID: PMC5096903 DOI: 10.1172/jci87148] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 08/16/2016] [Indexed: 12/23/2022] Open
Abstract
Oncogenic mutations drive anabolic metabolism, creating a dependency on nutrient influx through transporters, receptors, and macropinocytosis. While sphingolipids suppress tumor growth by downregulating nutrient transporters, macropinocytosis and autophagy still provide cancer cells with fuel. Therapeutics that simultaneously disrupt these parallel nutrient access pathways have potential as powerful starvation agents. Here, we describe a water-soluble, orally bioavailable synthetic sphingolipid, SH-BC-893, that triggers nutrient transporter internalization and also blocks lysosome-dependent nutrient generation pathways. SH-BC-893 activated protein phosphatase 2A (PP2A), leading to mislocalization of the lipid kinase PIKfyve. The concomitant mislocalization of the PIKfyve product PI(3,5)P2 triggered cytosolic vacuolation and blocked lysosomal fusion reactions essential for LDL, autophagosome, and macropinosome degradation. By simultaneously limiting access to both extracellular and intracellular nutrients, SH-BC-893 selectively killed cells expressing an activated form of the anabolic oncogene Ras in vitro and in vivo. However, slower-growing, autochthonous PTEN-deficient prostate tumors that did not exhibit a classic Warburg phenotype were equally sensitive. Remarkably, normal proliferative tissues were unaffected by doses of SH-BC-893 that profoundly inhibited tumor growth. These studies demonstrate that simultaneously blocking parallel nutrient access pathways with sphingolipid-based drugs is broadly effective and cancer selective, suggesting a potential strategy for overcoming the resistance conferred by tumor heterogeneity.
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Affiliation(s)
- Seong M. Kim
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Saurabh G. Roy
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Bin Chen
- Department of Chemistry, Université de Montréal, Montréal, Québec, Canada
| | - Tiffany M. Nguyen
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Ryan J. McMonigle
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Alison N. McCracken
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Yanling Zhang
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Satoshi Kofuji
- Departments of Internal Medicine, Neurosurgery, and Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Jue Hou
- Department of Biomedical Engineering, UCI, Irvine, California, USA
| | - Elizabeth Selwan
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Brendan T. Finicle
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Tricia T. Nguyen
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Archna Ravi
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Manuel U. Ramirez
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Tim Wiher
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Garret G. Guenther
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
| | - Mari Kono
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Bethesda, Maryland, USA
| | - Atsuo T. Sasaki
- Departments of Internal Medicine, Neurosurgery, and Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Lois S. Weisman
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Eric O. Potma
- Department of Biomedical Engineering, UCI, Irvine, California, USA
| | | | - Robert A. Edwards
- Department of Pathology, University of California Irvine School of Medicine, Irvine, California, USA
| | - Stephen Hanessian
- Department of Chemistry, Université de Montréal, Montréal, Québec, Canada
- Department of Pharmaceutical Sciences, UCI, Irvine, California, USA
| | - Aimee L. Edinger
- Department of Developmental and Cell Biology, University of California Irvine (UCI), Irvine, California, USA
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105
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Phosphatidylinositol 3,5-bisphosphate: regulation of cellular events in space and time. Biochem Soc Trans 2016; 44:177-84. [PMID: 26862203 DOI: 10.1042/bst20150174] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Phosphorylated phosphatidylinositol lipids are crucial for most eukaryotes and have diverse cellular functions. The low-abundance signalling lipid phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] is critical for cellular homoeostasis and adaptation to stimuli. A large complex of proteins that includes the lipid kinase Fab1-PIKfyve, dynamically regulates the levels of PI(3,5)P2. Deficiencies in PI(3,5)P2 are linked to some human diseases, especially those of the nervous system. Future studies will probably determine new, undiscovered regulatory roles of PI(3,5)P2, as well as uncover mechanistic insights into how PI(3,5)P2 contributes to normal human physiology.
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106
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The amyloid precursor protein (APP) binds the PIKfyve complex and modulates its function. Biochem Soc Trans 2016; 44:185-90. [PMID: 26862204 DOI: 10.1042/bst20150179] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Phosphoinositides are important components of eukaryotic membranes that are required for multiple forms of membrane dynamics. Phosphoinositides are involved in defining membrane identity, mediate cell signalling and control membrane trafficking events. Due to their pivotal role in membrane dynamics, phosphoinositide de-regulation contributes to various human diseases. In this review, we will focus on the newly emerging regulation of the PIKfyve complex, a phosphoinositide kinase that converts the endosomal phosphatidylinositol-3-phosphate [PI(3)P] to phosphatidylinositol-3,5-bisphosphate [PI(3,5)P2)], a low abundance phosphoinositide of outstanding importance for neuronal integrity and function. Loss of PIKfyve function is well known to result in neurodegeneration in both mouse models and human patients. Our recent work has surprisingly identified the amyloid precursor protein (APP), the central molecule in Alzheimer's disease aetiology, as a novel interaction partner of a subunit of the PIKfyve complex, Vac14. Furthermore, it has been shown that APP modulates PIKfyve function and PI(3,5)P2 dynamics, suggesting that the APP gene family functions as regulator of PI(3,5)P2 metabolism. The recent advances discussed in this review suggest a novel, unexpected, β-amyloid-independent mechanism for neurodegeneration in Alzheimer's disease.
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107
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Walker WP, Oehler A, Edinger AL, Wagner KU, Gunn TM. Oligodendroglial deletion of ESCRT-I component TSG101 causes spongiform encephalopathy. Biol Cell 2016; 108:324-337. [PMID: 27406702 DOI: 10.1111/boc.201600014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 07/05/2016] [Accepted: 07/06/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND INFORMATION Vacuolation of the central nervous system (CNS) is observed in patients with transmissible spongiform encephalopathy, HIV-related encephalopathy and some inherited diseases, but the underlying cellular mechanisms remain poorly understood. Mice lacking the mahogunin ring finger-1 (MGRN1) E3 ubiquitin ligase develop progressive, widespread spongiform degeneration of the CNS. MGRN1 ubiquitinates and regulates tumour susceptibility gene 101 (TSG101), a central component of the endosomal trafficking machinery. As loss of MGRN1 is predicted to cause partial TSG101 loss-of-function, we hypothesised that CNS vacuolation in Mgrn1 null mice may be caused by the accumulation of multi-cisternal endosome-like 'class E' vacuolar protein sorting (vps) compartments similar to those observed in Tsg101-depleted cells in culture. RESULTS To test this hypothesis, Tsg101 was deleted from mature oligodendroglia in vivo. This resulted in severe spongiform encephalopathy, histopathologically similar to that observed in Mgrn1 null mutant mice but with a more rapid onset. Vacuoles in the brains of Tsg101-deleted and Mgrn1 mutant mice labelled with endosomal markers, consistent with an endosomal origin. Vacuoles in the brains of mice inoculated with Rocky Mountain Laboratory (RML) prions did not label with these markers, indicating a different origin, consistent with previously published studies that indicate RML prions have a primary effect on neurons and cause vacuolation in an MGRN1-independent manner. Oligodendroglial deletion of Rab7, which mediates late endosome-to-lysosome trafficking and autophagosome-lysosome fusion, did not cause spongiform change. CONCLUSIONS Our data suggest that the formation of multi-cisternal 'class E' vps endosomal structures in oligodendroglia leads to vacuolation. SIGNIFICANCE This work provides the first evidence that disrupting multi-vesicular body formation in oligodendroglia can cause white matter vacuolation and demyelination. HIV is known to hijack the endosomal sorting machinery, suggesting that HIV infection of the CNS may also act through this pathway to cause encephalopathy.
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Affiliation(s)
- Will P Walker
- McLaughlin Research Institute, Great Falls, MT, 59405, USA
| | - Abby Oehler
- Department of Pathology, Institute for Neurodegenerative Diseases, University of California, San Francisco, CA, 94143, USA
| | - Aimee L Edinger
- Department of Developmental and Cell Biology, University of California, Irvine, CA, 92697, USA
| | - Kay-Uwe Wagner
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Teresa M Gunn
- McLaughlin Research Institute, Great Falls, MT, 59405, USA.
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108
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Abstract
Most functions of eukaryotic cells are controlled by cellular membranes, which are not static entities but undergo frequent budding, fission, fusion, and sculpting reactions collectively referred to as membrane dynamics. Consequently, regulation of membrane dynamics is crucial for cellular functions. A key mechanism in such regulation is the reversible recruitment of cytosolic proteins or protein complexes to specific membranes at specific time points. To a large extent this recruitment is orchestrated by phosphorylated derivatives of the membrane lipid phosphatidylinositol, known as phosphoinositides. The seven phosphoinositides found in nature localize to distinct membrane domains and recruit distinct effectors, thereby contributing strongly to the maintenance of membrane identity. Many of the phosphoinositide effectors are proteins that control membrane dynamics, and in this review we discuss the functions of phosphoinositides in membrane dynamics during exocytosis, endocytosis, autophagy, cell division, cell migration, and epithelial cell polarity, with emphasis on protein effectors that are recruited by specific phosphoinositides during these processes.
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Affiliation(s)
- Kay O Schink
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway; , .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway
| | - Kia-Wee Tan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway; , .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway; , .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway.,Centre of Molecular Inflammation Research, Faculty of Medicine, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
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109
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Lystad AH, Simonsen A. Phosphoinositide-binding proteins in autophagy. FEBS Lett 2016; 590:2454-68. [PMID: 27391591 DOI: 10.1002/1873-3468.12286] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 06/28/2016] [Accepted: 07/05/2016] [Indexed: 12/21/2022]
Abstract
Phosphoinositides represent a very small fraction of membrane phospholipids, having fast turnover rates and unique subcellular distributions, which make them perfect for initiating local temporal effects. Seven different phosphoinositide species are generated through reversible phosphorylation of the inositol ring of phosphatidylinositol (PtdIns). The negative charge generated by the phosphates provides specificity for interaction with various protein domains that commonly contain a cluster of basic residues. Examples of domains that bind phosphoinositides include PH domains, WD40 repeats, PX domains, and FYVE domains. Such domains often display specificity toward a certain species or subset of phosphoinositides. Here we will review the current literature of different phosphoinositide-binding proteins involved in autophagy.
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Affiliation(s)
- Alf Håkon Lystad
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Norway
| | - Anne Simonsen
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Norway
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110
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Feijóo-Bandín S, García-Vence M, García-Rúa V, Roselló-Lletí E, Portolés M, Rivera M, González-Juanatey JR, Lago F. Two-pore channels (TPCs): Novel voltage-gated ion channels with pleiotropic functions. Channels (Austin) 2016; 11:20-33. [PMID: 27440385 DOI: 10.1080/19336950.2016.1213929] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Two-pore channels (TPC1-3) comprise a subfamily of the eukaryotic voltage-gated ion channels (VGICs) superfamily that are mainly expressed in acidic stores in plants and animals. TPCS are widespread across the animal kingdom, with primates, mice and rats lacking TPC3, and mainly act as Ca+ and Na+ channels, although it was also suggested that they could be permeable to other ions. Nowadays, TPCs have been related to the development of different diseases, including Parkinson´s disease, obesity or myocardial ischemia. Due to this, their study has raised the interest of the scientific community to try to understand their mechanism of action in order to be able to develop an efficient drug that could regulate TPCs activity. In this review, we will provide an updated view regarding TPCs structure, function and activation, as well as their role in different pathophysiological processes.
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Affiliation(s)
- Sandra Feijóo-Bandín
- a Cellular and Molecular Cardiology Research Unit and Department of Cardiology , Institute of Biomedical Research and University Clinical Hospital , Santiago de Compostela , Spain
| | - María García-Vence
- a Cellular and Molecular Cardiology Research Unit and Department of Cardiology , Institute of Biomedical Research and University Clinical Hospital , Santiago de Compostela , Spain
| | - Vanessa García-Rúa
- a Cellular and Molecular Cardiology Research Unit and Department of Cardiology , Institute of Biomedical Research and University Clinical Hospital , Santiago de Compostela , Spain
| | - Esther Roselló-Lletí
- b Cardiocirculatory Unit, Health Institute of La Fe University Hospital , Valencia , Spain
| | - Manuel Portolés
- b Cardiocirculatory Unit, Health Institute of La Fe University Hospital , Valencia , Spain
| | - Miguel Rivera
- b Cardiocirculatory Unit, Health Institute of La Fe University Hospital , Valencia , Spain
| | - José Ramón González-Juanatey
- a Cellular and Molecular Cardiology Research Unit and Department of Cardiology , Institute of Biomedical Research and University Clinical Hospital , Santiago de Compostela , Spain
| | - Francisca Lago
- a Cellular and Molecular Cardiology Research Unit and Department of Cardiology , Institute of Biomedical Research and University Clinical Hospital , Santiago de Compostela , Spain
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111
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Lenk GM, Szymanska K, Debska-Vielhaber G, Rydzanicz M, Walczak A, Bekiesinska-Figatowska M, Vielhaber S, Hallmann K, Stawinski P, Buehring S, Hsu DA, Kunz WS, Meisler MH, Ploski R. Biallelic Mutations of VAC14 in Pediatric-Onset Neurological Disease. Am J Hum Genet 2016; 99:188-94. [PMID: 27292112 DOI: 10.1016/j.ajhg.2016.05.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 05/02/2016] [Indexed: 01/29/2023] Open
Abstract
In the PI(3,5)P2 biosynthetic complex, the lipid kinase PIKFYVE and the phosphatase FIG4 are bound to the dimeric scaffold protein VAC14, which is composed of multiple heat-repeat domains. Mutations of FIG4 result in the inherited disorders Charcot-Marie-Tooth disease type 4J, Yunis-Varón syndrome, and polymicrogyria with seizures. We here describe inherited variants of VAC14 in two unrelated children with sudden onset of a progressive neurological disorder and regression of developmental milestones. Both children developed impaired movement with dystonia, became nonambulatory and nonverbal, and exhibited striatal abnormalities on MRI. A diagnosis of Leigh syndrome was rejected due to normal lactate profiles. Exome sequencing identified biallelic variants of VAC14 that were inherited from unaffected heterozygous parents in both families. Proband 1 inherited a splice-site variant that results in skipping of exon 13, p.Ile459Profs(∗)4 (not reported in public databases), and the missense variant p.Trp424Leu (reported in the ExAC database in a single heterozygote). Proband 2 inherited two missense variants in the dimerization domain of VAC14, p.Ala582Ser and p.Ser583Leu, that have not been previously reported. Cultured skin fibroblasts exhibited the accumulation of vacuoles that is characteristic of PI(3,5)P2 deficiency. Vacuolization of fibroblasts was rescued by transfection of wild-type VAC14 cDNA. The similar age of onset and neurological decline in the two unrelated children define a recessive disorder resulting from compound heterozygosity for deleterious variants of VAC14.
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Krystyna Szymanska
- Department of Child Psychiatry, Warsaw Medical University, 02-106 Warsaw, Poland; Department of Experimental and Clinical Neuropathology, Medical Research Center, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | | | - Malgorzata Rydzanicz
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland
| | - Anna Walczak
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland
| | | | - Stefan Vielhaber
- Klinik für Neurologie, Universitätsklinikum Magdeburg, 39120 Magdeburg, Germany
| | - Kerstin Hallmann
- Klinik für Epileptologie and Life&Brain Center, Universitätsklinikum Bonn, 53105 Bonn, Germany
| | - Piotr Stawinski
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland; Institute of Physiology and Pathology of Hearing, 05-830 Nadarzyn, Poland
| | | | - David A Hsu
- Department of Neurology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Wolfram S Kunz
- Klinik für Epileptologie and Life&Brain Center, Universitätsklinikum Bonn, 53105 Bonn, Germany
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
| | - Rafal Ploski
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland.
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112
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Takatori S, Fujimoto T. A novel imaging method revealed phosphatidylinositol 3,5-bisphosphate-rich domains in the endosome/lysosome membrane. Commun Integr Biol 2016; 9:e1145319. [PMID: 27195064 PMCID: PMC4857783 DOI: 10.1080/19420889.2016.1145319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 01/18/2016] [Indexed: 11/04/2022] Open
Abstract
We developed a new method to observe distribution of phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P2] using electron microscopy. In freeze-fracture replicas of quick-frozen samples, PtdIns(3,5)P2 was labeled specifically using recombinant ATG18 tagged with glutathione S-transferase and 4×FLAG, which was mixed with an excess of recombinant PX domain to suppress binding of ATG18 to phosphatidylinositol 3-phosphate. Using this method, PtdIns(3,5)P2 was found to be enriched in limited domains in the yeast vacuole and mammalian endosomes. In the yeast vacuole exposed to hyperosmolar stress, PtdIns(3,5)P2 was distributed at a significantly higher density in the intramembrane particle (IMP)-deficient liquid-ordered domains than in the surrounding IMP-rich domains. In mammalian cells, PtdIns(3,5)P2 was observed in endosomes of tubulo-vesicular morphology labeled for RAB5 or RAB7. Notably, distribution density of PtdIns(3,5)P2 in the endosome was significantly higher in the vesicular portion than in the tubular portion. The nano-scale distribution of PtdIns(3,5)P2 revealed in the present study is important to understand its functional roles in the vacuole and endosomes.
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Affiliation(s)
- Sho Takatori
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo , Tokyo, Japan
| | - Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine , Nagoya, Japan
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113
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Hertz DL, Owzar K, Lessans S, Wing C, Jiang C, Kelly WK, Patel J, Halabi S, Furukawa Y, Wheeler HE, Sibley AB, Lassiter C, Weisman L, Watson D, Krens SD, Mulkey F, Renn CL, Small EJ, Febbo PG, Shterev I, Kroetz DL, Friedman PN, Mahoney JF, Carducci MA, Kelley MJ, Nakamura Y, Kubo M, Dorsey SG, Dolan ME, Morris MJ, Ratain MJ, McLeod HL. Pharmacogenetic Discovery in CALGB (Alliance) 90401 and Mechanistic Validation of a VAC14 Polymorphism that Increases Risk of Docetaxel-Induced Neuropathy. Clin Cancer Res 2016; 22:4890-4900. [PMID: 27143689 DOI: 10.1158/1078-0432.ccr-15-2823] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 04/04/2016] [Indexed: 12/13/2022]
Abstract
PURPOSE Discovery of SNPs that predict a patient's risk of docetaxel-induced neuropathy would enable treatment individualization to maximize efficacy and avoid unnecessary toxicity. The objectives of this analysis were to discover SNPs associated with docetaxel-induced neuropathy and mechanistically validate these associations in preclinical models of drug-induced neuropathy. EXPERIMENTAL DESIGN A genome-wide association study was conducted in metastatic castrate-resistant prostate cancer patients treated with docetaxel, prednisone and randomized to bevacizumab or placebo on CALGB 90401. SNPs were genotyped on the Illumina HumanHap610-Quad platform followed by rigorous quality control. The inference was conducted on the cumulative dose at occurrence of grade 3+ sensory neuropathy using a cause-specific hazard model that accounted for early treatment discontinuation. Genes with SNPs significantly associated with neuropathy were knocked down in cellular and mouse models of drug-induced neuropathy. RESULTS A total of 498,081 SNPs were analyzed in 623 Caucasian patients, 50 (8%) of whom experienced grade 3+ neuropathy. The 1,000 SNPs most associated with neuropathy clustered in relevant pathways including neuropathic pain and axonal guidance. An SNP in VAC14 (rs875858) surpassed genome-wide significance (P = 2.12 × 10-8, adjusted P = 5.88 × 10-7). siRNA knockdown of VAC14 in stem cell-derived peripheral neuronal cells increased docetaxel sensitivity as measured by decreased neurite processes (P = 0.0015) and branches (P < 0.0001). Prior to docetaxel treatment, VAC14 heterozygous mice had greater nociceptive sensitivity than wild-type litter mate controls (P = 0.001). CONCLUSIONS VAC14 should be prioritized for further validation of its potential role as a predictor of docetaxel-induced neuropathy and biomarker for treatment individualization. Clin Cancer Res; 22(19); 4890-900. ©2016 AACR.
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Affiliation(s)
- Daniel L Hertz
- Department of Clinical Pharmacy, University of Michigan College of Pharmacy, Ann Arbor, Michigan. UNC Institute for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Kouros Owzar
- Duke Cancer Institute, Durham, North Carolina. Alliance Statistics and Data Center, Duke University, Durham, North Carolina
| | - Sherrie Lessans
- Department of Pain and Translational Symptom Science, University of Maryland School of Nursing, Baltimore, Maryland
| | - Claudia Wing
- Department of Medicine, University of Chicago, Chicago, Illinois
| | - Chen Jiang
- Alliance Statistics and Data Center, Duke University, Durham, North Carolina
| | | | - Jai Patel
- UNC Institute for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Levine Cancer Institute, Carolinas HealthCare System, Charlotte, North Carolina
| | - Susan Halabi
- Duke Cancer Institute, Durham, North Carolina. Alliance Statistics and Data Center, Duke University, Durham, North Carolina
| | - Yoichi Furukawa
- Division of Clinical Genome Research, Advanced Clinical Research Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | | | | | - Cameron Lassiter
- Department of Pain and Translational Symptom Science, University of Maryland School of Nursing, Baltimore, Maryland
| | - Lois Weisman
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan
| | - Dorothy Watson
- Alliance Statistics and Data Center, Duke University, Durham, North Carolina
| | - Stefanie D Krens
- UNC Institute for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Utrecht University, Faculty of Science, Department of Pharmaceutical Sciences, Utrecht, the Netherlands
| | - Flora Mulkey
- Alliance Statistics and Data Center, Duke University, Durham, North Carolina
| | - Cynthia L Renn
- Department of Pain and Translational Symptom Science, University of Maryland School of Nursing, Baltimore, Maryland
| | - Eric J Small
- Department of Medicine, UCSF, San Francisco, California
| | | | - Ivo Shterev
- Department of Biostatistics and Bioinformatics, Duke University, Durham, North Carolina
| | - Deanna L Kroetz
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California
| | - Paula N Friedman
- Department of Medicine, University of Chicago, Chicago, Illinois
| | - John F Mahoney
- Levine Cancer Institute, Carolinas HealthCare System, Charlotte, North Carolina
| | - Michael A Carducci
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University, Baltimore, Maryland
| | - Michael J Kelley
- Durham VA Medical Center, Duke University Medical Center, Durham, North Carolina
| | - Yusuke Nakamura
- Department of Medicine, University of Chicago, Chicago, Illinois. Division of Clinical Genome Research, Advanced Clinical Research Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Michiaki Kubo
- Lab for Genotyping Development, Riken Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Susan G Dorsey
- Department of Pain and Translational Symptom Science, University of Maryland School of Nursing, Baltimore, Maryland
| | - M Eileen Dolan
- Department of Medicine, University of Chicago, Chicago, Illinois
| | | | - Mark J Ratain
- Department of Medicine, University of Chicago, Chicago, Illinois
| | - Howard L McLeod
- UNC Institute for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Personalized Medicine Institute, Moffitt Cancer Center, Tampa, Florida.
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A cell-permeable tool for analysing APP intracellular domain function and manipulation of PIKfyve activity. Biosci Rep 2016; 36:BSR20160040. [PMID: 26934981 PMCID: PMC5293579 DOI: 10.1042/bsr20160040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 03/02/2016] [Indexed: 12/24/2022] Open
Abstract
The mechanisms for regulating PIKfyve complex activity are currently emerging. The PIKfyve complex, consisting of the phosphoinositide kinase PIKfyve (also known as FAB1), VAC14 and FIG4, is required for the production of phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2]. PIKfyve function is required for homoeostasis of the endo/lysosomal system and is crucially implicated in neuronal function and integrity, as loss of function mutations in the PIKfyve complex lead to neurodegeneration in mouse models and human patients. Our recent work has shown that the intracellular domain of the amyloid precursor protein (APP), a molecule central to the aetiology of Alzheimer's disease binds to VAC14 and enhances PIKfyve function. In the present study, we utilize this recent advance to create an easy-to-use tool for increasing PIKfyve activity in cells. We fused APP intracellular domain (AICD) to the HIV TAT domain, a cell-permeable peptide allowing proteins to penetrate cells. The resultant TAT-AICD fusion protein is cell permeable and triggers an increase in PI(3,5)P2 Using the PI(3,5)P2 specific GFP-ML1Nx2 probe, we show that cell-permeable AICD alters PI(3,5)P2 dynamics. TAT-AICD also provides partial protection from pharmacological inhibition of PIKfyve. All three lines of evidence show that the AICD activates the PIKfyve complex in cells, a finding that is important for our understanding of the mechanism of neurodegeneration in Alzheimer's disease.
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115
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A molecular mechanism to regulate lysosome motility for lysosome positioning and tubulation. Nat Cell Biol 2016; 18:404-17. [PMID: 26950892 PMCID: PMC4871318 DOI: 10.1038/ncb3324] [Citation(s) in RCA: 283] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/04/2016] [Indexed: 12/12/2022]
Abstract
To mediate the degradation of bio-macromolecules, lysosomes must traffic towards cargo-carrying vesicles for subsequent membrane fusion or fission. Mutations of the lysosomal Ca2+ channel TRPML1 cause lysosome storage disease (LSD) characterized by disordered lysosomal membrane trafficking in cells. Here we show that TRPML1 activity is required to promote Ca2+-dependent centripetal movement of lysosomes towards the perinuclear region, where autophagosomes accumulate, upon autophagy induction. ALG-2, an EF-hand-containing protein, serves as a lysosomal Ca2+ sensor that associates physically with the minus-end directed dynactin-dynein motor, while PI(3,5)P2, a lysosome-localized phosphoinositide, acts upstream of TRPML1. Furthermore, the PI(3,5)P2-TRPML1-ALG-2-dynein signaling is necessary for lysosome tubulation and reformation. In contrast, the TRPML1 pathway is not required for the perinuclear accumulation of lysosomes observed in many LSDs, which is instead likely caused by secondary cholesterol accumulation that constitutively activates Rab7-RILP-dependent retrograde transport. Collectively, Ca2+ release from lysosomes provides an on-demand mechanism regulating lysosome motility, positioning, and tubulation.
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Ho CY, Choy CH, Botelho RJ. Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation. J Vis Exp 2016. [PMID: 26780479 DOI: 10.3791/53529] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Phosphoinositides (PtdInsPs) are essential signaling lipids responsible for recruiting specific effectors and conferring organelles with molecular identity and function. Each of the seven PtdInsPs varies in their distribution and abundance, which are tightly regulated by specific kinases and phosphatases. The abundance of PtdInsPs can change abruptly in response to various signaling events or disturbance of the regulatory machinery. To understand how these events lead to changes in the amount of PtdInsPs and their resulting impact, it is important to quantify PtdInsP levels before and after a signaling event or between control and abnormal conditions. However, due to their low abundance and similarity, quantifying the relative amounts of each PtdInsP can be challenging. This article describes a method for quantifying PtdInsP levels by metabolically labeling cells with (3)H-myo-inositol, which is incorporated into PtdInsPs. Phospholipids are then precipitated and deacylated. The resulting soluble (3)H-glycero-inositides are further extracted, separated by high-performance liquid chromatography (HPLC), and detected by flow scintillation. The labeling and processing of yeast samples is described in detail, as well as the instrumental setup for the HPLC and flow scintillator. Despite losing structural information regarding acyl chain content, this method is sensitive and can be optimized to concurrently quantify all seven PtdInsPs in cells.
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Affiliation(s)
- Cheuk Y Ho
- Department of Chemistry and Biology, Program in Molecular Science, Ryerson University
| | - Christopher H Choy
- Department of Chemistry and Biology, Program in Molecular Science, Ryerson University
| | - Roberto J Botelho
- Department of Chemistry and Biology, Program in Molecular Science, Ryerson University;
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Currinn H, Guscott B, Balklava Z, Rothnie A, Wassmer T. APP controls the formation of PI(3,5)P(2) vesicles through its binding of the PIKfyve complex. Cell Mol Life Sci 2016; 73:393-408. [PMID: 26216398 PMCID: PMC4706845 DOI: 10.1007/s00018-015-1993-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 06/26/2015] [Accepted: 07/16/2015] [Indexed: 12/05/2022]
Abstract
Phosphoinositides are signalling lipids that are crucial for major signalling events as well as established regulators of membrane trafficking. Control of endosomal sorting and endosomal homeostasis requires phosphatidylinositol-3-phosphate (PI(3)P) and phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2), the latter a lipid of low abundance but significant physiological relevance. PI(3,5)P2 is formed by phosphorylation of PI(3)P by the PIKfyve complex which is crucial for maintaining endosomal homeostasis. Interestingly, loss of PIKfyve function results in dramatic neurodegeneration. Despite the significance of PIKfyve, its regulation is still poorly understood. Here we show that the Amyloid Precursor Protein (APP), a central molecule in Alzheimer's disease, associates with the PIKfyve complex (consisting of Vac14, PIKfyve and Fig4) and that the APP intracellular domain directly binds purified Vac14. We also show that the closely related APP paralogues, APLP1 and 2 associate with the PIKfyve complex. Whether APP family proteins can additionally form direct protein-protein interaction with PIKfyve or Fig4 remains to be explored. We show that APP binding to the PIKfyve complex drives formation of PI(3,5)P2 positive vesicles and that APP gene family members are required for supporting PIKfyve function. Interestingly, the PIKfyve complex is required for APP trafficking, suggesting a feedback loop in which APP, by binding to and stimulating PI(3,5)P2 vesicle formation may control its own trafficking. These data suggest that altered APP processing, as observed in Alzheimer's disease, may disrupt PI(3,5)P2 metabolism, endosomal sorting and homeostasis with important implications for our understanding of the mechanism of neurodegeneration in Alzheimer's disease.
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Affiliation(s)
- Heather Currinn
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
| | - Benjamin Guscott
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
| | - Zita Balklava
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
| | - Alice Rothnie
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
| | - Thomas Wassmer
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK.
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118
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Differential impact of type-1 and type-2 diabetes on control of heart rate in mice. Auton Neurosci 2015; 194:17-25. [PMID: 26725752 DOI: 10.1016/j.autneu.2015.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 11/23/2015] [Accepted: 12/14/2015] [Indexed: 01/14/2023]
Abstract
AIMS Cardiac autonomic dysfunction is a serious complication of diabetes. One consequence is disruption of the normal beat-to-beat regulation of heart rate (HR), i.e. HR variability (HRV). However, our understanding of the disease process has been limited by inconsistent HR/HRV data from previous animal studies. We hypothesized that differences in the method of measurement, time of day, and level of stress account for the differing results across studies. Thus, our aim was to systematically assess HR and HRV in two common diabetic mouse models. METHODS ECG radiotelemetry devices were implanted into db/db (type-2 diabetic), STZ-treated db/+ (type-1 diabetic), and control db/+ mice (n=4 per group). HR and HRV were analyzed over 24 h and during treadmill testing. RESULTS 24 h analysis revealed that db/db mice had an altered pattern of circadian HR changes, and STZ-treated mice had reduced HR throughout. HRV measures linked to sympathetic control were reduced in db/db mice in the early morning and early afternoon, and partially reduced in STZ-treated mice. HR response to treadmill testing was blunted in both models. CONCLUSIONS It is important to consider both time of day and level of stress when assessing HR and HRV in diabetic mice. db/db mice may have altered circadian rhythm of sympathetic control of HR, whereas STZ-treated mice have a relative reduction. This study provides baseline data and a framework for HR analysis that may guide future investigations.
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119
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Hong NH, Qi A, Weaver AM. PI(3,5)P2 controls endosomal branched actin dynamics by regulating cortactin-actin interactions. J Cell Biol 2015; 210:753-69. [PMID: 26323691 PMCID: PMC4555817 DOI: 10.1083/jcb.201412127] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The late endosomal lipid PI(3,5)P2 binds to cortactin through the filamentous actin (F-actin) binding domain of cortactin, leading to removal of cortactin from endosomal actin networks and inhibition of cortactin-mediated branched actin nucleation and stabilization. Branched actin critically contributes to membrane trafficking by regulating membrane curvature, dynamics, fission, and transport. However, how actin dynamics are controlled at membranes is poorly understood. Here, we identify the branched actin regulator cortactin as a direct binding partner of phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) and demonstrate that their interaction promotes turnover of late endosomal actin. In vitro biochemical studies indicated that cortactin binds PI(3,5)P2 via its actin filament-binding region. Furthermore, PI(3,5)P2 competed with actin filaments for binding to cortactin, thereby antagonizing cortactin activity. These findings suggest that PI(3,5)P2 formation on endosomes may remove cortactin from endosome-associated branched actin. Indeed, inhibition of PI(3,5)P2 production led to cortactin accumulation and actin stabilization on Rab7+ endosomes. Conversely, inhibition of Arp2/3 complex activity greatly reduced cortactin localization to late endosomes. Knockdown of cortactin reversed PI(3,5)P2-inhibitor–induced actin accumulation and stabilization on endosomes. These data suggest a model in which PI(3,5)P2 binding removes cortactin from late endosomal branched actin networks and thereby promotes net actin turnover.
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Affiliation(s)
- Nan Hyung Hong
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Aidong Qi
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Alissa M Weaver
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN 37232 Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232 Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232
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120
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Takatori S, Tatematsu T, Cheng J, Matsumoto J, Akano T, Fujimoto T. Phosphatidylinositol 3,5-Bisphosphate-Rich Membrane Domains in Endosomes and Lysosomes. Traffic 2015; 17:154-67. [PMID: 26563567 DOI: 10.1111/tra.12346] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 11/04/2015] [Accepted: 11/04/2015] [Indexed: 02/02/2023]
Abstract
Phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2 ) has critical functions in endosomes and lysosomes. We developed a method to define nanoscale distribution of PtdIns(3,5)P2 using freeze-fracture electron microscopy. GST-ATG18-4×FLAG was used to label PtdIns(3,5)P2 and its binding to phosphatidylinositol 3-phosphate (PtdIns(3)P) was blocked by an excess of the p40(phox) PX domain. In yeast exposed to hyperosmotic stress, PtdIns(3,5)P2 was concentrated in intramembrane particle (IMP)-deficient domains in the vacuolar membrane, which made close contact with adjacent membranes. The IMP-deficient domain was also enriched with PtdIns(3)P, but was deficient in Vph1p, a liquid-disordered domain marker. In yeast lacking either PtdIns(3,5)P2 or its effector, Atg18p, the IMP-deficient, PtdIns(3)P-rich membranes were folded tightly to make abnormal tubular structures, thus showing where the vacuolar fragmentation process is arrested when PtdIns(3,5)P2 metabolism is defective. In HeLa cells, PtdIns(3,5)P2 was significantly enriched in the vesicular domain of RAB5- and RAB7-positive endosome/lysosomes of the tubulo-vesicular morphology. This biased distribution of PtdIns(3,5)P2 was also observed using fluorescence microscopy, which further showed enrichment of a retromer component, VPS35, in the tubular domain. This is the first report to show segregation of PtdIns(3,5)P2 -rich and -deficient domains in endosome/lysosomes, which should be important for endosome/lysosome functionality.
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Affiliation(s)
- Sho Takatori
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan.,Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-8654, Japan
| | - Tsuyako Tatematsu
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan
| | - Jinglei Cheng
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan
| | - Jun Matsumoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan
| | - Takuya Akano
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan
| | - Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan
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Lenk GM, Frei CM, Miller AC, Wallen RC, Mironova YA, Giger RJ, Meisler MH. Rescue of neurodegeneration in the Fig4 null mouse by a catalytically inactive FIG4 transgene. Hum Mol Genet 2015; 25:340-7. [PMID: 26604144 DOI: 10.1093/hmg/ddv480] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/16/2015] [Indexed: 11/13/2022] Open
Abstract
The lipid phosphatase FIG4 is a subunit of the protein complex that regulates biosynthesis of the signaling lipid PI(3,5)P2. Mutations of FIG4 result in juvenile lethality and spongiform neurodegeneration in the mouse, and are responsible for the human disorders Charcot-Marie-Tooth disease, Yunis-Varon syndrome and polymicrogyria with seizures. We previously demonstrated that conditional expression of a wild-type FIG4 transgene in neurons is sufficient to rescue most of the abnormalities of Fig4 null mice, including juvenile lethality and extensive neurodegeneration. To evaluate the contribution of the phosphatase activity to the in vivo function of Fig4, we introduced the mutation p.Cys486Ser into the Sac phosphatase active-site motif CX5RT. Transfection of the Fig4(Cys486Ser) cDNA into cultured Fig4(-/-) fibroblasts was effective in preventing vacuolization. The neuronal expression of an NSE-Fig4(Cys486Ser) transgene in vivo prevented the neonatal neurodegeneration and juvenile lethality seen in Fig4 null mice. These observations demonstrate that the catalytically inactive FIG4 protein provides significant function, possibly by stabilization of the PI(3,5)P2 biosynthetic complex and/or localization of the complex to endolysosomal vesicles. Despite this partial rescue, later in life the NSE-Fig4(Cys486Ser) transgenic mice display significant abnormalities that include hydrocephalus, defective myelination and reduced lifespan. The late onset phenotype of the NSE-Fig4(Cys486Ser) transgenic mice demonstrates that the phosphatase activity of FIG4 has an essential role in vivo.
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Affiliation(s)
| | | | | | | | | | - Roman J Giger
- Department of Cell and Developmental Biology and Department of Neurology, University of Michigan, 4909 Buhl, Ann Arbor, MI 48109-5618, USA
| | - Miriam H Meisler
- Department of Human Genetics, Department of Neurology, University of Michigan, 4909 Buhl, Ann Arbor, MI 48109-5618, USA
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The ML1Nx2 Phosphatidylinositol 3,5-Bisphosphate Probe Shows Poor Selectivity in Cells. PLoS One 2015; 10:e0139957. [PMID: 26460749 PMCID: PMC4604148 DOI: 10.1371/journal.pone.0139957] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 09/17/2015] [Indexed: 01/15/2023] Open
Abstract
Phosphatidylinositol (3,5)-bisphosphate (PtdIns(3,5)P2) is a quantitatively minor phospholipid in eukaryotic cells that plays a fundamental role in regulating endocytic membrane traffic. Despite its clear importance for cellular function and organism physiology, mechanistic details of its biology have so far not been fully elucidated. In part, this is due to a lack of experimental tools that specifically probe for PtdIns(3,5)P2 in cells to unambiguously identify its dynamics and site(s) of action. In this study, we have evaluated a recently reported PtdIns(3,5)P2 biosensor, GFP-ML1Nx2, for its veracity as such a probe. We report that, in live cells, the localization of this biosensor to sub-cellular compartments is largely independent of PtdIns(3,5)P2, as assessed after pharmacological, chemical genetic or genomic interventions that block the lipid's synthesis. We therefore conclude that it is unwise to interpret the localization of ML1Nx2 as a true and unbiased biosensor for PtdIns(3,5)P2.
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123
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Miranda AM, Oliveira TG. Lipids under stress - a lipidomic approach for the study of mood disorders. Bioessays 2015; 37:1226-35. [DOI: 10.1002/bies.201500070] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- André Miguel Miranda
- Life and Health Sciences Research Institute (ICVS); School of Health Sciences; University of Minho; Campus Gualtar Braga Portugal
- ICVS/3B's - PT Government Associate Laboratory; Braga/Guimarães Portugal
| | - Tiago Gil Oliveira
- Life and Health Sciences Research Institute (ICVS); School of Health Sciences; University of Minho; Campus Gualtar Braga Portugal
- ICVS/3B's - PT Government Associate Laboratory; Braga/Guimarães Portugal
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Ikonomov OC, Sbrissa D, Compton LM, Kumar R, Tisdale EJ, Chen X, Shisheva A. The Protein Complex of Neurodegeneration-related Phosphoinositide Phosphatase Sac3 and ArPIKfyve Binds the Lewy Body-associated Synphilin-1, Preventing Its Aggregation. J Biol Chem 2015; 290:28515-28529. [PMID: 26405034 DOI: 10.1074/jbc.m115.669929] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Indexed: 12/14/2022] Open
Abstract
The 5-phosphoinositide phosphatase Sac3, in which loss-of-function mutations are linked to neurodegenerative disorders, forms a stable cytosolic complex with the scaffolding protein ArPIKfyve. The ArPIKfyve-Sac3 heterodimer interacts with the phosphoinositide 5-kinase PIKfyve in a ubiquitous ternary complex that couples PtdIns(3,5)P2 synthesis with turnover at endosomal membranes, thereby regulating the housekeeping endocytic transport in eukaryotes. Neuron-specific associations of the ArPIKfyve-Sac3 heterodimer, which may shed light on the neuropathological mechanisms triggered by Sac3 dysfunction, are unknown. Here we conducted mass spectrometry analysis for brain-derived interactors of ArPIKfyve-Sac3 and unraveled the α-synuclein-interacting protein Synphilin-1 (Sph1) as a new component of the ArPIKfyve-Sac3 complex. Sph1, a predominantly neuronal protein that facilitates aggregation of α-synuclein, is a major component of Lewy body inclusions in neurodegenerative α-synucleinopathies. Modulations in ArPIKfyve/Sac3 protein levels by RNA silencing or overexpression in several mammalian cell lines, including human neuronal SH-SY5Y or primary mouse cortical neurons, revealed that the ArPIKfyve-Sac3 complex specifically altered the aggregation properties of Sph1-GFP. This effect required an active Sac3 phosphatase and proceeded through mechanisms that involved increased Sph1-GFP partitioning into the cytosol and removal of Sph1-GFP aggregates by basal autophagy but not by the proteasomal system. If uncoupled from ArPIKfyve elevation, overexpressed Sac3 readily aggregated, markedly enhancing the aggregation potential of Sph1-GFP. These data identify a novel role of the ArPIKfyve-Sac3 complex in the mechanisms controlling aggregate formation of Sph1 and suggest that Sac3 protein deficiency or overproduction may facilitate aggregation of aggregation-prone proteins, thereby precipitating the onset of multiple neuronal disorders.
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Affiliation(s)
- Ognian C Ikonomov
- Departments of Physiology, Wayne State School of Medicine, Detroit, Michigan 48201
| | - Diego Sbrissa
- Departments of Physiology, Wayne State School of Medicine, Detroit, Michigan 48201
| | - Lauren M Compton
- Departments of Physiology, Wayne State School of Medicine, Detroit, Michigan 48201
| | - Rita Kumar
- Departments of Physiology, Wayne State School of Medicine, Detroit, Michigan 48201; Departments of Emergency Medicine, Wayne State School of Medicine, Detroit, Michigan 48201
| | - Ellen J Tisdale
- Departments of Pharmacology, Wayne State School of Medicine, Detroit, Michigan 48201
| | - Xuequn Chen
- Departments of Physiology, Wayne State School of Medicine, Detroit, Michigan 48201
| | - Assia Shisheva
- Departments of Physiology, Wayne State School of Medicine, Detroit, Michigan 48201.
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Messenger SW, Thomas DD, Cooley MM, Jones EK, Falkowski MA, August BK, Fernandez LA, Gorelick FS, Groblewski GE. Early to Late Endosome Trafficking Controls Secretion and Zymogen Activation in Rodent and Human Pancreatic Acinar Cells. Cell Mol Gastroenterol Hepatol 2015; 1:695-709. [PMID: 26618189 PMCID: PMC4657148 DOI: 10.1016/j.jcmgh.2015.08.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND & AIMS Pancreatic acinar cells have an expanded apical endosomal system, the physiological and pathophysiological significance of which is still emerging. Phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2) is an essential phospholipid generated by PIKfyve, which phosphorylates phosphatidylinositol-3-phosphate (PI(3)P). PI(3,5)P2 is necessary for maturation of early endosomes (EE) to late endosomes (LE). Inhibition of EE to LE trafficking enhances anterograde endosomal trafficking and secretion at the plasma membrane by default through a recycling endosome (RE) intermediate. We assessed the effects of modulating PIKfyve activity on apical trafficking and pancreatitis responses in pancreatic acinar cells. METHODS Inhibition of EE to LE trafficking was achieved using pharmacological inhibitors of PIKfyve, expression of dominant negative PIKfyve K1877E, or constitutively active Rab5-GTP Q79L. Anterograde endosomal trafficking was manipulated by expression of constitutively active and dominant negative Rab11a mutants. The effects of these agents on secretion, endolysosomal exocytosis of lysosome associated membrane protein (LAMP1), and trypsinogen activation in response to high-dose CCK-8, bile acids and cigarette toxin was determined. RESULTS PIKfyve inhibition increased basal and stimulated secretion. Adenoviral overexpression of PIKfyve decreased secretion leading to cellular death. Expression of Rab5-GTP Q79L or Rab11a-GTP Q70L enhanced secretion. Conversely, dominant-negative Rab11a-GDP S25N reduced secretion. High-dose CCK inhibited endolysosomal exocytosis that was reversed by PIKfyve inhibition. PIKfyve inhibition blocked intracellular trypsin accumulation and cellular damage responses to high CCK-8, tobacco toxin, and bile salts in both rodent and human acini. CONCLUSIONS These data demonstrate that EE-LE trafficking acutely controls acinar secretion and the intracellular activation of zymogens leading to the pathogenicity of acute pancreatitis.
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Affiliation(s)
- Scott W. Messenger
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Diana D.H. Thomas
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Michelle M. Cooley
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | - Elaina K. Jones
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | | | - Benjamin K. August
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin
| | | | - Fred S. Gorelick
- Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut,Department of Cell Biology, School of Medicine, Yale University, New Haven, Connecticut,Veterans Administration Connecticut Healthcare, West Haven, Connecticut
| | - Guy E. Groblewski
- Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin,Correspondence Address correspondence to: Guy E. Groblewski, PhD, University of Wisconsin–Madison, Department of Nutritional Sciences, 1415 Linden Drive, Madison, Wisconsin 53706. fax: (608) 262-5860.University of Wisconsin–MadisonDepartment of Nutritional Sciences1415 Linden DriveMadisonWisconsin 53706
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Hayashi K, Sasai M, Iwasaki A. Toll-like receptor 9 trafficking and signaling for type I interferons requires PIKfyve activity. Int Immunol 2015; 27:435-45. [PMID: 25925170 PMCID: PMC4560039 DOI: 10.1093/intimm/dxv021] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 04/17/2015] [Indexed: 12/17/2022] Open
Abstract
Toll-like receptors (TLRs) traffic to distinct membranes for signaling. TLR7 and TLR9 recognize viral nucleic acids in the endosomes and induce robust anti-viral program. Signaling from these TLRs bifurcate at the level of distinct endosomal compartments, namely VAMP3(+) and LAMP(+) endosomes, to mediate the induction of cytokine and type I interferon (IFN) genes, respectively. The formation of the TLR9 endosome competent for IFNs induction requires AP-3. Phosphoinositides (PIs) mark distinct subcellular membranes and control membrane trafficking. However, their role in TLR trafficking and signaling in different dendritic cell (DC) subsets remains unclear. Here, we examined the role of phosphatidylinositol 3P 5-kinase, PIKfyve, in TLR9 trafficking and signaling. We demonstrate that inhibition of PIKfyve activity preferentially blocks TLR9 signaling for type I IFN induction in FLT3L-bone marrow-derived DCs. By confocal microscopy using RAW264.7 cells, we show that trafficking of both TLR9 and CpG to the LAMP1(+) compartment was blocked by PIKfyve inhibitor treatment, whereas their trafficking to the VAMP3(+) endosome remained intact. Further, AP-3 recruitment to TLR9 endosomes was impaired by PIKfyve inhibition. These data indicate that PIKfyve provides critical PIs necessary for the formation of endosome from which TLR9 signals to induce type I IFNs.
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Affiliation(s)
- Kachiko Hayashi
- Howard Hughes Medical Institute, Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, TAC S655B, New Haven, CT 06520, USA
| | - Miwa Sasai
- Howard Hughes Medical Institute, Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, TAC S655B, New Haven, CT 06520, USA Present address: Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
| | - Akiko Iwasaki
- Howard Hughes Medical Institute, Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, TAC S655B, New Haven, CT 06520, USA
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127
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Liu P, Gan W, Chin YR, Ogura K, Guo J, Zhang J, Wang B, Blenis J, Cantley LC, Toker A, Su B, Wei W. PtdIns(3,4,5)P3-Dependent Activation of the mTORC2 Kinase Complex. Cancer Discov 2015; 5:1194-209. [PMID: 26293922 DOI: 10.1158/2159-8290.cd-15-0460] [Citation(s) in RCA: 266] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 08/18/2015] [Indexed: 12/15/2022]
Abstract
UNLABELLED mTOR serves as a central regulator of cell growth and metabolism by forming two distinct complexes, mTORC1 and mTORC2. Although mechanisms of mTORC1 activation by growth factors and amino acids have been extensively studied, the upstream regulatory mechanisms leading to mTORC2 activation remain largely elusive. Here, we report that the pleckstrin homology (PH) domain of SIN1, an essential and unique component of mTORC2, interacts with the mTOR kinase domain to suppress mTOR activity. More importantly, PtdIns(3,4,5)P3, but not other PtdInsPn species, interacts with SIN1-PH to release its inhibition on the mTOR kinase domain, thereby triggering mTORC2 activation. Mutating critical SIN1 residues that mediate PtdIns(3,4,5)P3 interaction inactivates mTORC2, whereas mTORC2 activity is pathologically increased by patient-derived mutations in the SIN1-PH domain, promoting cell growth and tumor formation. Together, our study unravels a PI3K-dependent mechanism for mTORC2 activation, allowing mTORC2 to activate AKT in a manner that is regulated temporally and spatially by PtdIns(3,4,5)P3. SIGNIFICANCE The SIN1-PH domain interacts with the mTOR kinase domain to suppress mTOR activity, and PtdIns(3,4,5)P3 binds the SIN1-PH domain to release its inhibition on the mTOR kinase domain, leading to mTORC2 activation. Cancer patient-derived SIN1-PH domain mutations gain oncogenicity by loss of suppressing mTOR activity as a means to facilitate tumorigenesis.
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Affiliation(s)
- Pengda Liu
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Wenjian Gan
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Y Rebecca Chin
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Kohei Ogura
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Jianping Guo
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Jinfang Zhang
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Bin Wang
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - John Blenis
- Cancer Center at Weill Cornell Medical College and New York-Presbyterian Hospital, New York, New York
| | - Lewis C Cantley
- Cancer Center at Weill Cornell Medical College and New York-Presbyterian Hospital, New York, New York
| | - Alex Toker
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Bing Su
- Shanghai Institute of Immunology, Department of Microbiology and Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China. Department of Immunobiology and the Vascular Biology and Therapeutics Program, Yale University, New Haven, Connecticut.
| | - Wenyi Wei
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
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128
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Hierro A, Gershlick DC, Rojas AL, Bonifacino JS. Formation of Tubulovesicular Carriers from Endosomes and Their Fusion to the trans-Golgi Network. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 318:159-202. [PMID: 26315886 DOI: 10.1016/bs.ircmb.2015.05.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Endosomes undergo extensive spatiotemporal rearrangements as proteins and lipids flux through them in a series of fusion and fission events. These controlled changes enable the concentration of cargo for eventual degradation while ensuring the proper recycling of other components. A growing body of studies has now defined multiple recycling pathways from endosomes to the trans-Golgi network (TGN) which differ in their molecular machineries. The recycling process requires specific sets of lipids, coats, adaptors, and accessory proteins that coordinate cargo selection with membrane deformation and its association with the cytoskeleton. Specific tethering factors and SNARE (SNAP (Soluble NSF Attachment Protein) Receptor) complexes are then required for the docking and fusion with the acceptor membrane. Herein, we summarize some of the current knowledge of the machineries that govern the retrograde transport from endosomes to the TGN.
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Affiliation(s)
- Aitor Hierro
- Structural Biology Unit, CIC bioGUNE, Derio, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - David C Gershlick
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | | | - Juan S Bonifacino
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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129
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Balklava Z, Niehage C, Currinn H, Mellor L, Guscott B, Poulin G, Hoflack B, Wassmer T. The Amyloid Precursor Protein Controls PIKfyve Function. PLoS One 2015; 10:e0130485. [PMID: 26125944 PMCID: PMC4488396 DOI: 10.1371/journal.pone.0130485] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 05/20/2015] [Indexed: 12/27/2022] Open
Abstract
While the Amyloid Precursor Protein (APP) plays a central role in Alzheimer's disease, its cellular function still remains largely unclear. It was our goal to establish APP function which will provide insights into APP's implication in Alzheimer's disease. Using our recently developed proteo-liposome assay we established the interactome of APP's intracellular domain (known as AICD), thereby identifying novel APP interactors that provide mechanistic insights into APP function. By combining biochemical, cell biological and genetic approaches we validated the functional significance of one of these novel interactors. Here we show that APP binds the PIKfyve complex, an essential kinase for the synthesis of the endosomal phosphoinositide phosphatidylinositol-3,5-bisphosphate. This signalling lipid plays a crucial role in endosomal homeostasis and receptor sorting. Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals. Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo. This regulation is required for maintaining endosomal and neuronal function. Our findings establish an unexpected role for APP in the regulation of endosomal phosphoinositide metabolism with dramatic consequences for endosomal biology and important implications for our understanding of Alzheimer's disease.
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Affiliation(s)
- Zita Balklava
- Aston University, School of Life and Health Sciences, Aston Triangle, Birmingham, B4 7ET, United Kingdom
| | - Christian Niehage
- Biotechnologisches Zentrum, TU-Dresden, Tatzberg 47–49, 01307 Dresden, Germany
| | - Heather Currinn
- Aston University, School of Life and Health Sciences, Aston Triangle, Birmingham, B4 7ET, United Kingdom
| | - Laura Mellor
- University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Benjamin Guscott
- Aston University, School of Life and Health Sciences, Aston Triangle, Birmingham, B4 7ET, United Kingdom
| | - Gino Poulin
- University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Bernard Hoflack
- Biotechnologisches Zentrum, TU-Dresden, Tatzberg 47–49, 01307 Dresden, Germany
| | - Thomas Wassmer
- Aston University, School of Life and Health Sciences, Aston Triangle, Birmingham, B4 7ET, United Kingdom
- * E-mail:
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130
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Glade MJ, Smith K. A glance at … exercise and glucose uptake. Nutrition 2015; 31:893-7. [PMID: 25933500 DOI: 10.1016/j.nut.2014.12.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 12/03/2014] [Indexed: 10/24/2022]
Affiliation(s)
| | - Kyl Smith
- Progressive Laboratories Inc., Irving, Texas
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131
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Up-regulation of lysosomal TRPML1 channels is essential for lysosomal adaptation to nutrient starvation. Proc Natl Acad Sci U S A 2015; 112:E1373-81. [PMID: 25733853 DOI: 10.1073/pnas.1419669112] [Citation(s) in RCA: 161] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Upon nutrient starvation, autophagy digests unwanted cellular components to generate catabolites that are required for housekeeping biosynthesis processes. A complete execution of autophagy demands an enhancement in lysosome function and biogenesis to match the increase in autophagosome formation. Here, we report that mucolipin-1 (also known as TRPML1 or ML1), a Ca(2+) channel in the lysosome that regulates many aspects of lysosomal trafficking, plays a central role in this quality-control process. By using Ca(2+) imaging and whole-lysosome patch clamping, lysosomal Ca(2+) release and ML1 currents were detected within hours of nutrient starvation and were potently up-regulated. In contrast, lysosomal Na(+)-selective currents were not up-regulated. Inhibition of mammalian target of rapamycin (mTOR) or activation of transcription factor EB (TFEB) mimicked a starvation effect in fed cells. The starvation effect also included an increase in lysosomal proteostasis and enhanced clearance of lysosomal storage, including cholesterol accumulation in Niemann-Pick disease type C (NPC) cells. However, this effect was not observed when ML1 was pharmacologically inhibited or genetically deleted. Furthermore, overexpression of ML1 mimicked the starvation effect. Hence, lysosomal adaptation to environmental cues such as nutrient levels requires mTOR/TFEB-dependent, lysosome-to-nucleus regulation of lysosomal ML1 channels and Ca(2+) signaling.
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132
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Hammond GRV, Balla T. Polyphosphoinositide binding domains: Key to inositol lipid biology. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:746-58. [PMID: 25732852 DOI: 10.1016/j.bbalip.2015.02.013] [Citation(s) in RCA: 178] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 01/29/2015] [Accepted: 02/17/2015] [Indexed: 01/01/2023]
Abstract
Polyphosphoinositides (PPIn) are an important family of phospholipids located on the cytoplasmic leaflet of eukaryotic cell membranes. Collectively, they are critical for the regulation of many aspects of membrane homeostasis and signaling, with notable relevance to human physiology and disease. This regulation is achieved through the selective interaction of these lipids with hundreds of cellular proteins, and thus the capability to study these localized interactions is crucial to understanding their functions. In this review, we discuss current knowledge of the principle types of PPIn-protein interactions, focusing on specific lipid-binding domains. We then discuss how these domains have been re-tasked by biologists as molecular probes for these lipids in living cells. Finally, we describe how the knowledge gained with these probes, when combined with other techniques, has led to the current view of the lipids' localization and function in eukaryotes, focusing mainly on animal cells. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Tamas Balla
- Section on Molecular Signal Transduction, Eunice Shriver Kennedy National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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133
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Waugh MG. PIPs in neurological diseases. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1066-82. [PMID: 25680866 DOI: 10.1016/j.bbalip.2015.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 01/29/2015] [Accepted: 02/01/2015] [Indexed: 12/19/2022]
Abstract
Phosphoinositide (PIP) lipids regulate many aspects of cell function in the nervous system including receptor signalling, secretion, endocytosis, migration and survival. Levels of PIPs such as PI4P, PI(4,5)P2 and PI(3,4,5)P3 are normally tightly regulated by phosphoinositide kinases and phosphatases. Deregulation of these biochemical pathways leads to lipid imbalances, usually on intracellular endosomal membranes, and these changes have been linked to a number of major neurological diseases including Alzheimer's, Parkinson's, epilepsy, stroke, cancer and a range of rarer inherited disorders including brain overgrowth syndromes, Charcot-Marie-Tooth neuropathies and neurodevelopmental conditions such as Lowe's syndrome. This article analyses recent progress in this area and explains how PIP lipids are involved, to varying degrees, in almost every class of neurological disease. This article is part of a Special Issue entitled Brain Lipids.
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Affiliation(s)
- Mark G Waugh
- Lipid and Membrane Biology Group, Institute for Liver and Digestive Health, UCL, Royal Free Campus, Rowland Hill Street, London NW3 2PF, United Kingdom.
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134
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PI(5)P regulates autophagosome biogenesis. Mol Cell 2015; 57:219-34. [PMID: 25578879 PMCID: PMC4306530 DOI: 10.1016/j.molcel.2014.12.007] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 10/22/2014] [Accepted: 11/25/2014] [Indexed: 01/12/2023]
Abstract
Phosphatidylinositol 3-phosphate (PI(3)P), the product of class III PI3K VPS34, recruits specific autophagic effectors, like WIPI2, during the initial steps of autophagosome biogenesis and thereby regulates canonical autophagy. However, mammalian cells can produce autophagosomes through enigmatic noncanonical VPS34-independent pathways. Here we show that PI(5)P can regulate autophagy via PI(3)P effectors and thereby identify a mechanistic explanation for forms of noncanonical autophagy. PI(5)P synthesis by the phosphatidylinositol 5-kinase PIKfyve was required for autophagosome biogenesis, and it increased levels of PI(5)P, stimulated autophagy, and reduced the levels of autophagic substrates. Inactivation of VPS34 impaired recruitment of WIPI2 and DFCP1 to autophagic precursors, reduced ATG5-ATG12 conjugation, and compromised autophagosome formation. However, these phenotypes were rescued by PI(5)P in VPS34-inactivated cells. These findings provide a mechanistic framework for alternative VPS34-independent autophagy-initiating pathways, like glucose starvation, and unravel a cytoplasmic function for PI(5)P, which previously has been linked predominantly to nuclear roles. PI(5)P positively regulates autophagy PI(5)P is associated with autophagy effectors that bind PI(3)P PI(5)P sustains noncanonical autophagy in PI(3)P-depleted cells PI(5)P is essential for VPS34-independent, glucose-starvation-induced autophagy
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135
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Bridges D, Saltiel AR. Phosphoinositides: Key modulators of energy metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:857-66. [PMID: 25463477 DOI: 10.1016/j.bbalip.2014.11.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/31/2014] [Accepted: 11/10/2014] [Indexed: 12/19/2022]
Abstract
Phosphoinositides are key players in many trafficking and signaling pathways. Recent advances regarding the synthesis, location and functions of these lipids have dramatically improved our understanding of how and when these lipids are generated and what their roles are in animal physiology. In particular, phosphoinositides play a central role in insulin signaling, and manipulation of PtdIns(3,4,5)P₃levels in particular, may be an important potential therapeutic target for the alleviation of insulin resistance associated with obesity and the metabolic syndrome. In this article we review the metabolism, regulation and functional roles of phosphoinositides in insulin signaling and the regulation of energy metabolism. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Dave Bridges
- Departments of Physiology and Pediatrics, University of Tennessee Health Science Center, Memphis, TN, USA; Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, TN, USA.
| | - Alan R Saltiel
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
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136
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Shisheva A, Sbrissa D, Ikonomov O. Plentiful PtdIns5P from scanty PtdIns(3,5)P2 or from ample PtdIns? PIKfyve-dependent models: Evidence and speculation (response to: DOI 10.1002/bies.201300012). Bioessays 2014; 37:267-77. [PMID: 25404370 DOI: 10.1002/bies.201400129] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Recently, we have presented data supporting the notion that PIKfyve not only produces the majority of constitutive phosphatidylinositol 5-phosphate (PtdIns5P) in mammalian cells but that it does so through direct synthesis from PtdIns. Another group, albeit obtaining similar data, suggests an alternative pathway whereby the low-abundance PtdIns(3,5)P2 undergoes hydrolysis by unidentified 3-phosphatases, thereby serving as a precursor for most of PtdIns5P. Here, we review the experimental evidence supporting constitutive synthesis of PtdIns5P from PtdIns by PIKfyve. We further emphasize that the experiments presented in support of the alternative pathway are also compatible with a direct mechanism for PIKfyve-catalyzed synthesis of PtdIns5P. While agreeing with the authors that constitutive PtdIns5P could theoretically be produced from PtdIns(3,5)P2 by 3-dephosphorylation, we argue that until direct evidence for such an alternative pathway is obtained, we should adhere to the existing experimental evidence and quantitative considerations, which favor direct PIKfyve-catalyzed synthesis for most constitutive PtdIns5P.
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Affiliation(s)
- Assia Shisheva
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA
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137
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Activity-dependent PI(3,5)P2 synthesis controls AMPA receptor trafficking during synaptic depression. Proc Natl Acad Sci U S A 2014; 111:E4896-905. [PMID: 25355904 DOI: 10.1073/pnas.1411117111] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Dynamic regulation of phosphoinositide lipids (PIPs) is crucial for diverse cellular functions, and, in neurons, PIPs regulate membrane trafficking events that control synapse function. Neurons are particularly sensitive to the levels of the low abundant PIP, phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2], because mutations in PI(3,5)P2-related genes are implicated in multiple neurological disorders, including epilepsy, severe neuropathy, and neurodegeneration. Despite the importance of PI(3,5)P2 for neural function, surprisingly little is known about this signaling lipid in neurons, or any cell type. Notably, the mammalian homolog of yeast vacuole segregation mutant (Vac14), a scaffold for the PI(3,5)P2 synthesis complex, is concentrated at excitatory synapses, suggesting a potential role for PI(3,5)P2 in controlling synapse function and/or plasticity. PI(3,5)P2 is generated from phosphatidylinositol 3-phosphate (PI3P) by the lipid kinase PI3P 5-kinase (PIKfyve). Here, we present methods to measure and control PI(3,5)P2 synthesis in hippocampal neurons and show that changes in neural activity dynamically regulate the levels of multiple PIPs, with PI(3,5)P2 being among the most dynamic. The levels of PI(3,5)P2 in neurons increased during two distinct forms of synaptic depression, and inhibition of PIKfyve activity prevented or reversed induction of synaptic weakening. Moreover, altering neuronal PI(3,5)P2 levels was sufficient to regulate synaptic strength bidirectionally, with enhanced synaptic function accompanying loss of PI(3,5)P2 and reduced synaptic strength following increased PI(3,5)P2 levels. Finally, inhibiting PI(3,5)P2 synthesis alters endocytosis and recycling of AMPA-type glutamate receptors (AMPARs), implicating PI(3,5)P2 dynamics in AMPAR trafficking. Together, these data identify PI(3,5)P2-dependent signaling as a regulatory pathway that is critical for activity-dependent changes in synapse strength.
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138
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Abstract
UNLABELLED Adenoviruses are frequent causes of pediatric myocarditis. Little is known about the pathogenesis of adenovirus myocarditis, and the species specificity of human adenoviruses has limited the development of animal models, which is a significant barrier to strategies for prevention or treatment. We have developed a mouse model of myocarditis following mouse adenovirus 1 (MAV-1) infection to study the pathogenic mechanisms of this important cause of pediatric myocarditis. Following intranasal infection of neonatal C57BL/6 mice, we detected viral replication and induction of interferon gamma (IFN-γ) in the hearts of infected mice. MAV-1 caused myocyte necrosis and induced substantial cellular inflammation that was composed predominantly of CD3(+) T lymphocytes. Depletion of IFN-γ during acute infection reduced cardiac inflammation in MAV-1-infected mice without affecting viral replication. We observed decreased contractility during acute infection of neonatal mice, and persistent viral infection in the heart was associated with cardiac remodeling and hypertrophy in adulthood. IFN-γ is a proinflammatory mediator during adenovirus-induced myocarditis, and persistent adenovirus infection may contribute to ongoing cardiac dysfunction. IMPORTANCE Studying the pathogenesis of myocarditis caused by different viruses is essential in order to characterize both virus-specific and generalized factors that contribute to disease. Very little is known about the pathogenesis of adenovirus myocarditis, which is a significant impediment to the development of treatment or prevention strategies. We used MAV-1 to establish a mouse model of human adenovirus myocarditis, providing the means to study host and pathogen factors contributing to adenovirus-induced cardiac disease during acute and persistent infection. The MAV-1 model will enable fundamental studies of viral myocarditis, including IFN-γ modulation as a therapeutic strategy.
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139
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Bulley SJ, Clarke JH, Droubi A, Giudici ML, Irvine RF. Exploring phosphatidylinositol 5-phosphate 4-kinase function. Adv Biol Regul 2014; 57:193-202. [PMID: 25311266 PMCID: PMC4359101 DOI: 10.1016/j.jbior.2014.09.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 09/01/2014] [Accepted: 09/02/2014] [Indexed: 11/30/2022]
Abstract
The family of phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks) is emerging from a comparative backwater in inositide signalling into the mainstream, as is their substrate, phosphatidylinositol 5-phosphate (PI5P). Here we review some of the key questions about the PI5P4Ks, their localisation, interaction, and regulation and also we summarise our current understanding of how PI5P is synthesised and what its cellular functions might be. Finally, some of the evidence for the involvement of PI5P4Ks in pathology is discussed.
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Affiliation(s)
- Simon J Bulley
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Jonathan H Clarke
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Alaa Droubi
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK
| | | | - Robin F Irvine
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK.
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140
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Min SH, Suzuki A, Stalker TJ, Zhao L, Wang Y, McKennan C, Riese MJ, Guzman JF, Zhang S, Lian L, Joshi R, Meng R, Seeholzer SH, Choi JK, Koretzky G, Marks MS, Abrams CS. Loss of PIKfyve in platelets causes a lysosomal disease leading to inflammation and thrombosis in mice. Nat Commun 2014; 5:4691. [PMID: 25178411 DOI: 10.1038/ncomms5691] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 07/13/2014] [Indexed: 01/07/2023] Open
Abstract
PIKfyve is essential for the synthesis of phosphatidylinositol-3,5-bisphosphate [PtdIns(3,5)P2] and for the regulation of endolysosomal membrane dynamics in mammals. PtdIns(3,5)P2 deficiency causes neurodegeneration in mice and humans, but the role of PtdIns(3,5)P2 in non-neural tissues is poorly understood. Here we show that platelet-specific ablation of PIKfyve in mice leads to accelerated arterial thrombosis, and, unexpectedly, also to inappropriate inflammatory responses characterized by macrophage accumulation in multiple tissues. These multiorgan defects are attenuated by platelet depletion in vivo, confirming that they reflect a platelet-specific process. PIKfyve ablation in platelets induces defective maturation and excessive storage of lysosomal enzymes that are released upon platelet activation. Impairing lysosome secretion from PIKfyve-null platelets in vivo markedly attenuates the multiorgan defects, suggesting that platelet lysosome secretion contributes to pathogenesis. Our findings identify PIKfyve as an essential regulator for platelet lysosome homeostasis, and demonstrate the contributions of platelet lysosomes to inflammation, arterial thrombosis and macrophage biology.
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Affiliation(s)
- Sang H Min
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Aae Suzuki
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Timothy J Stalker
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Liang Zhao
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Yuhuan Wang
- Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
| | - Chris McKennan
- Proteomics Core, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
| | - Matthew J Riese
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Jessica F Guzman
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Suhong Zhang
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Lurong Lian
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Rohan Joshi
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Ronghua Meng
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Steven H Seeholzer
- Proteomics Core, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
| | - John K Choi
- Department of Pathology, St Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Gary Koretzky
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Michael S Marks
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Charles S Abrams
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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141
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Kim GH, Dayam RM, Prashar A, Terebiznik M, Botelho RJ. PIKfyve Inhibition Interferes with Phagosome and Endosome Maturation in Macrophages. Traffic 2014; 15:1143-63. [DOI: 10.1111/tra.12199] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 07/11/2014] [Accepted: 07/14/2014] [Indexed: 01/17/2023]
Affiliation(s)
- Grace H.E. Kim
- Deparment of Chemistry and Biology and the Molecular Science Program; Ryerson University; Toronto Ontario M5B2K3 Canada
| | - Roya M. Dayam
- Deparment of Chemistry and Biology and the Molecular Science Program; Ryerson University; Toronto Ontario M5B2K3 Canada
| | - Akriti Prashar
- Department of Cell and Systems Biology; University of Toronto at Scarborough; Toronto Ontario M1C 1A4 Canada
| | - Mauricio Terebiznik
- Department of Cell and Systems Biology; University of Toronto at Scarborough; Toronto Ontario M1C 1A4 Canada
| | - Roberto J. Botelho
- Deparment of Chemistry and Biology and the Molecular Science Program; Ryerson University; Toronto Ontario M5B2K3 Canada
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142
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PIKfyve, MTMR3 and their product PtdIns5P regulate cancer cell migration and invasion through activation of Rac1. Biochem J 2014; 461:383-90. [DOI: 10.1042/bj20140132] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have found that the activity of Rac1 is regulated by the lipid PtdIns5P produced by PIKfyve and MTMR3 and that the activities of these druggable enzymes are important for cancer cell migration and invasion.
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143
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Ueda Y. The Role of Phosphoinositides in Synapse Function. Mol Neurobiol 2014; 50:821-38. [DOI: 10.1007/s12035-014-8768-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Accepted: 06/01/2014] [Indexed: 11/30/2022]
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144
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Samie MA, Xu H. Lysosomal exocytosis and lipid storage disorders. J Lipid Res 2014; 55:995-1009. [PMID: 24668941 DOI: 10.1194/jlr.r046896] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Indexed: 12/11/2022] Open
Abstract
Lysosomes are acidic compartments in mammalian cells that are primarily responsible for the breakdown of endocytic and autophagic substrates such as membranes, proteins, and lipids into their basic building blocks. Lysosomal storage diseases (LSDs) are a group of metabolic disorders caused by genetic mutations in lysosomal hydrolases required for catabolic degradation, mutations in lysosomal membrane proteins important for catabolite export or membrane trafficking, or mutations in nonlysosomal proteins indirectly affecting these lysosomal functions. A hallmark feature of LSDs is the primary and secondary excessive accumulation of undigested lipids in the lysosome, which causes lysosomal dysfunction and cell death, and subsequently pathological symptoms in various tissues and organs. There are more than 60 types of LSDs, but an effective therapeutic strategy is still lacking for most of them. Several recent in vitro and in vivo studies suggest that induction of lysosomal exocytosis could effectively reduce the accumulation of the storage materials. Meanwhile, the molecular machinery and regulatory mechanisms for lysosomal exocytosis are beginning to be revealed. In this paper, we first discuss these recent developments with the focus on the functional interactions between lipid storage and lysosomal exocytosis. We then discuss whether lysosomal exocytosis can be manipulated to correct lysosomal and cellular dysfunction caused by excessive lipid storage, providing a potentially general therapeutic approach for LSDs.
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Affiliation(s)
- Mohammad Ali Samie
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
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145
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Schulze U, Vollenbröker B, Braun DA, Van Le T, Granado D, Kremerskothen J, Fränzel B, Klosowski R, Barth J, Fufezan C, Wolters DA, Pavenstädt H, Weide T. The Vac14-interaction network is linked to regulators of the endolysosomal and autophagic pathway. Mol Cell Proteomics 2014; 13:1397-411. [PMID: 24578385 DOI: 10.1074/mcp.m113.034108] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The scaffold protein Vac14 acts in a complex with the lipid kinase PIKfyve and its counteracting phosphatase FIG4, regulating the interconversion of phosphatidylinositol-3-phosphate to phosphatidylinositol-3,5-bisphosphate. Dysfunctional Vac14 mutants, a deficiency of one of the Vac14 complex components, or inhibition of PIKfyve enzymatic activity results in the formation of large vacuoles in cells. How these vacuoles are generated and which processes are involved are only poorly understood. Here we show that ectopic overexpression of wild-type Vac14 as well as of the PIKfyve-binding deficient Vac14 L156R mutant causes vacuoles. Vac14-dependent vacuoles and PIKfyve inhibitor-dependent vacuoles resulted in elevated levels of late endosomal, lysosomal, and autophagy-associated proteins. However, only late endosomal marker proteins were bound to the membranes of these enlarged vacuoles. In order to decipher the linkage between the Vac14 complex and regulators of the endolysosomal pathway, a protein affinity approach combined with multidimensional protein identification technology was conducted, and novel molecular links were unraveled. We found and verified the interaction of Rab9 and the Rab7 GAP TBC1D15 with Vac14. The identified Rab-related interaction partners support the theory that the regulation of vesicular transport processes and phosphatidylinositol-modifying enzymes are tightly interconnected.
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Affiliation(s)
- Ulf Schulze
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany
| | - Beate Vollenbröker
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany
| | - Daniela A Braun
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany
| | - Truc Van Le
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany
| | - Daniel Granado
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany
| | - Joachim Kremerskothen
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany
| | - Benjamin Fränzel
- ‖Analytical Chemistry NC4/72, Biomolecular Mass Spectrometry/Proteincenter, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany
| | - Rafael Klosowski
- ‖Analytical Chemistry NC4/72, Biomolecular Mass Spectrometry/Proteincenter, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany
| | - Johannes Barth
- ‡‡Institute of Plant Biology and Biotechnology, University of Muenster, Schlossplatz 8, D-48143 Muenster, Germany
| | - Christian Fufezan
- ‡‡Institute of Plant Biology and Biotechnology, University of Muenster, Schlossplatz 8, D-48143 Muenster, Germany
| | - Dirk A Wolters
- ‖Analytical Chemistry NC4/72, Biomolecular Mass Spectrometry/Proteincenter, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany
| | - Hermann Pavenstädt
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany;
| | - Thomas Weide
- From the ‡Department of Internal Medicine D, Molecular Nephrology, University Hospital of Muenster, Albert-Schweitzer Campus 1, A14, D-48149 Muenster, Germany;
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146
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Jin N, Mao K, Jin Y, Tevzadze G, Kauffman EJ, Park S, Bridges D, Loewith R, Saltiel AR, Klionsky DJ, Weisman LS. Roles for PI(3,5)P2 in nutrient sensing through TORC1. Mol Biol Cell 2014; 25:1171-85. [PMID: 24478451 PMCID: PMC3967979 DOI: 10.1091/mbc.e14-01-0021] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The protein kinase TORC1 regulates cell growth in response to nutrients. This study demonstrates that phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) is a critical upstream modulator of TORC1 activity in yeast. In this capacity, PI(3,5)P2 is required for TORC1-dependent regulation of autophagy and nutrient-dependent endocytosis. TORC1, a conserved protein kinase, regulates cell growth in response to nutrients. Localization of mammalian TORC1 to lysosomes is essential for TORC1 activation. Phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), an endosomal signaling lipid, is implicated in insulin-dependent stimulation of TORC1 activity in adipocytes. This raises the question of whether PI(3,5)P2 is an essential general regulator of TORC1. Moreover, the subcellular location where PI(3,5)P2 regulates TORC1 was not known. Here we report that PI(3,5)P2 is required for TORC1 activity in yeast and regulates TORC1 on the vacuole (lysosome). Furthermore, we show that the TORC1 substrate, Sch9 (a homologue of mammalian S6K), is recruited to the vacuole by direct interaction with PI(3,5)P2, where it is phosphorylated by TORC1. Of importance, we find that PI(3,5)P2 is required for multiple downstream pathways via TORC1-dependent phosphorylation of additional targets, including Atg13, the modification of which inhibits autophagy, and phosphorylation of Npr1, which releases its inhibitory function and allows nutrient-dependent endocytosis. These findings reveal PI(3,5)P2 as a general regulator of TORC1 and suggest that PI(3,5)P2 provides a platform for TORC1 signaling from lysosomes.
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Affiliation(s)
- Natsuko Jin
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109 Department of Molecular, Cellular, and Developmental Biology and Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109 Department of Internal Medicine and Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109 Department of Molecular Biology, University of Geneva, Geneva 1211, Switzerland Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109
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147
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Abstract
The endolysosomal system and autophagy are essential components of macromolecular turnover in eukaryotic cells. The low-abundance signaling lipid PI(3,5)P2 is a key regulator of this pathway. Analysis of mouse models with defects in PI(3,5)P2 biosynthesis has revealed the unique dependence of the mammalian nervous system on this signaling pathway. This insight led to the discovery of the molecular basis for several human neurological disorders, including Charcot-Marie-Tooth disease and Yunis-Varon syndrome. Spontaneous mutants, conditional knockouts, transgenic lines, and gene-trap alleles of Fig4, Vac14, and Pikfyve (Fab1) in the mouse have provided novel information regarding the role of PI(3,5)P2in vivo. This review summarizes what has been learned from mouse models and highlights the utility of manipulating complex signaling pathways in vivo.
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA.
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148
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Abstract
The first member of the mammalian mucolipin TRP channel subfamily (TRPML1) is a cation-permeable channel that is predominantly localized on the membranes of late endosomes and lysosomes (LELs) in all mammalian cell types. In response to the regulatory changes of LEL-specific phosphoinositides or other cellular cues, TRPML1 may mediate the release of Ca(2+) and heavy metal Fe(2+)/Zn(2+)ions into the cytosol from the LEL lumen, which in turn may regulate membrane trafficking events (fission and fusion), signal transduction, and ionic homeostasis in LELs. Human mutations in TRPML1 result in type IV mucolipidosis (ML-IV), a childhood neurodegenerative lysosome storage disease. At the cellular level, loss-of-function mutations of mammalian TRPML1 or its C. elegans or Drosophila homolog gene results in lysosomal trafficking defects and lysosome storage. In this chapter, we summarize recent advances in our understandings of the cell biological and channel functions of TRPML1. Studies on TRPML1's channel properties and its regulation by cellular activities may provide clues for developing new therapeutic strategies to delay neurodegeneration in ML-IV and other lysosome-related pediatric diseases.
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149
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Abstract
TRPML3 belongs to the MCOLN (TRPML) subfamily of transient receptor potential (TRP) channels comprising three genes in mammals. Since the discovery of the pain sensing, capsaicin- and heat-activated vanilloid receptor (TRPV1), TRP channels have been found to be involved in regulating almost all kinds of our sensory modalities. Thus, TRP channel members are sensitive to heat or cold; they are involved in pain or osmosensation, vision, hearing, or taste sensation. Loss or mutation of TRPML1 can cause retina degeneration and eventually blindness in mice and men (mucolipidosis type IV). Gain-of-function mutations in TRPML3 cause deafness and circling behavior in mice. A special feature of TRPML channels is their intracellular expression. They mostly reside in membranes of organelles of the endolysosomal system such as early and late endosomes, recycling endosomes, lysosomes, or lysosome-related organelles. Although the physiological roles of TRPML channels within the endolysosomal system are far from being fully understood, it is speculated that they are involved in the regulation of endolysosomal pH, fusion/fission processes, trafficking, autophagy, and/or (hormone) secretion and exocytosis.
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150
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Viaud J, Boal F, Tronchère H, Gaits-Iacovoni F, Payrastre B. Phosphatidylinositol 5-phosphate: A nuclear stress lipid and a tuner of membranes and cytoskeleton dynamics. Bioessays 2013; 36:260-72. [DOI: 10.1002/bies.201300132] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Julien Viaud
- Inserm U1048; I2MC and Université Paul Sabatier; Toulouse France
| | - Frédéric Boal
- Inserm U1048; I2MC and Université Paul Sabatier; Toulouse France
| | - Hélène Tronchère
- Inserm U1048; I2MC and Université Paul Sabatier; Toulouse France
| | | | - Bernard Payrastre
- Inserm U1048; I2MC and Université Paul Sabatier; Toulouse France
- CHU de Toulouse; Laboratoire d'Hématologie; Toulouse France
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