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Yuen ELH, Leary AY, Clavel M, Tumtas Y, Mohseni A, Zhao J, Picchianti L, Jamshidiha M, Pandey P, Duggan C, Cota E, Dagdas Y, Bozkurt TO. A RabGAP negatively regulates plant autophagy and immune trafficking. Curr Biol 2024; 34:2049-2065.e6. [PMID: 38677281 DOI: 10.1016/j.cub.2024.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 03/11/2024] [Accepted: 04/02/2024] [Indexed: 04/29/2024]
Abstract
Plants rely on autophagy and membrane trafficking to tolerate stress, combat infections, and maintain cellular homeostasis. However, the molecular interplay between autophagy and membrane trafficking is poorly understood. Using an AI-assisted approach, we identified Rab3GAP-like (Rab3GAPL) as a key membrane trafficking node that controls plant autophagy negatively. Rab3GAPL suppresses autophagy by binding to ATG8, the core autophagy adaptor, and deactivating Rab8a, a small GTPase essential for autophagosome formation and defense-related secretion. Rab3GAPL reduces autophagic flux in three model plant species, suggesting that its negative regulatory role in autophagy is conserved in land plants. Beyond autophagy regulation, Rab3GAPL modulates focal immunity against the oomycete pathogen Phytophthora infestans by preventing defense-related secretion. Altogether, our results suggest that Rab3GAPL acts as a molecular rheostat to coordinate autophagic flux and defense-related secretion by restraining Rab8a-mediated trafficking. This unprecedented interplay between a RabGAP-Rab pair and ATG8 sheds new light on the intricate membrane transport mechanisms underlying plant autophagy and immunity.
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Affiliation(s)
- Enoch Lok Him Yuen
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Alexandre Y Leary
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Marion Clavel
- Gregor Mendel Institute of Molecular Plant Biology, Vienna BioCenter, Dr. Bohr-Gasse, 1030 Vienna, Austria; Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Yasin Tumtas
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Azadeh Mohseni
- Gregor Mendel Institute of Molecular Plant Biology, Vienna BioCenter, Dr. Bohr-Gasse, 1030 Vienna, Austria
| | - Jierui Zhao
- Gregor Mendel Institute of Molecular Plant Biology, Vienna BioCenter, Dr. Bohr-Gasse, 1030 Vienna, Austria
| | - Lorenzo Picchianti
- Gregor Mendel Institute of Molecular Plant Biology, Vienna BioCenter, Dr. Bohr-Gasse, 1030 Vienna, Austria
| | - Mostafa Jamshidiha
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Pooja Pandey
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Cian Duggan
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Ernesto Cota
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Yasin Dagdas
- Gregor Mendel Institute of Molecular Plant Biology, Vienna BioCenter, Dr. Bohr-Gasse, 1030 Vienna, Austria.
| | - Tolga O Bozkurt
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.
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Essandoh K, Teuber JP, Brody MJ. Regulation of cardiomyocyte intracellular trafficking and signal transduction by protein palmitoylation. Biochem Soc Trans 2024; 52:41-53. [PMID: 38385554 PMCID: PMC10903464 DOI: 10.1042/bst20221296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/08/2024] [Accepted: 02/12/2024] [Indexed: 02/23/2024]
Abstract
Despite the well-established functions of protein palmitoylation in fundamental cellular processes, the roles of this reversible post-translational lipid modification in cardiomyocyte biology remain poorly studied. Palmitoylation is catalyzed by a family of 23 zinc finger and Asp-His-His-Cys domain-containing S-acyltransferases (zDHHC enzymes) and removed by select thioesterases of the lysophospholipase and α/β-hydroxylase domain (ABHD)-containing families of serine hydrolases. Recently, studies utilizing genetic manipulation of zDHHC enzymes in cardiomyocytes have begun to unveil essential functions for these enzymes in regulating cardiac development, homeostasis, and pathogenesis. Palmitoylation co-ordinates cardiac electrophysiology through direct modulation of ion channels and transporters to impact their trafficking or gating properties as well as indirectly through modification of regulators of channels, transporters, and calcium handling machinery. Not surprisingly, palmitoylation has roles in orchestrating the intracellular trafficking of proteins in cardiomyocytes, but also dynamically fine-tunes cardiomyocyte exocytosis and natriuretic peptide secretion. Palmitoylation has emerged as a potent regulator of intracellular signaling in cardiomyocytes, with recent studies uncovering palmitoylation-dependent regulation of small GTPases through direct modification and sarcolemmal targeting of the small GTPases themselves or by modification of regulators of the GTPase cycle. In addition to dynamic control of G protein signaling, cytosolic DNA is sensed and transduced into an inflammatory transcriptional output through palmitoylation-dependent activation of the cGAS-STING pathway, which has been targeted pharmacologically in preclinical models of heart disease. Further research is needed to fully understand the complex regulatory mechanisms governed by protein palmitoylation in cardiomyocytes and potential emerging therapeutic targets.
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Affiliation(s)
- Kobina Essandoh
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, U.S.A
| | - James P. Teuber
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, U.S.A
| | - Matthew J. Brody
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, U.S.A
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, U.S.A
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3
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Essandoh K, Subramani A, Ferro OA, Teuber JP, Koripella S, Brody MJ. zDHHC9 Regulates Cardiomyocyte Rab3a Activity and Atrial Natriuretic Peptide Secretion Through Palmitoylation of Rab3gap1. JACC Basic Transl Sci 2023; 8:518-542. [PMID: 37325411 PMCID: PMC10264568 DOI: 10.1016/j.jacbts.2022.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 11/09/2022] [Accepted: 11/15/2022] [Indexed: 02/25/2023]
Abstract
Production and release of natriuretic peptides by the stressed heart reduce cardiac workload by promoting vasodilation, natriuresis, and diuresis, which has been leveraged in the recent development of novel heart-failure pharmacotherapies, yet the mechanisms regulating cardiomyocyte exocytosis and natriuretic peptide release remain ill defined. We found that the Golgi S-acyltransferase zDHHC9 palmitoylates Rab3gap1 resulting in its spatial segregation from Rab3a, elevation of Rab3a-GTP levels, formation of Rab3a-positive peripheral vesicles, and impairment of exocytosis that limits atrial natriuretic peptide release. This novel pathway potentially can be exploited for targeting natriuretic peptide signaling in the treatment of heart failure.
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Affiliation(s)
- Kobina Essandoh
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Olivia A. Ferro
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - James P. Teuber
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - Sribharat Koripella
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - Matthew J. Brody
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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4
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Kerkeni N, Kharrat M, Maazoul F, Boudabous H, M’rad R, Trabelsi M. Novel RAB3GAP1 Mutation in the First Tunisian Family With Warburg Micro Syndrome. J Clin Neurol 2022; 18:214-222. [PMID: 35196747 PMCID: PMC8926778 DOI: 10.3988/jcn.2022.18.2.214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 08/24/2021] [Accepted: 08/24/2021] [Indexed: 11/17/2022] Open
Affiliation(s)
- Nesrine Kerkeni
- University of Tunis El Manar, Faculty of Medicine of Tunis, Laboratory of Human Genetics LR99ES10, Tunis, Tunisia
| | - Maher Kharrat
- University of Tunis El Manar, Faculty of Medicine of Tunis, Laboratory of Human Genetics LR99ES10, Tunis, Tunisia
| | - Faouzi Maazoul
- University of Tunis El Manar, Faculty of Medicine of Tunis, Laboratory of Human Genetics LR99ES10, Tunis, Tunisia
- Department of Congenital and Hereditary Diseases, Charles Nicolle Hospital, Tunis, Tunisia
| | - Hela Boudabous
- Department of Paediatrics, Rabta Hospital, Tunis, Tunisia
| | - Ridha M’rad
- University of Tunis El Manar, Faculty of Medicine of Tunis, Laboratory of Human Genetics LR99ES10, Tunis, Tunisia
- Department of Congenital and Hereditary Diseases, Charles Nicolle Hospital, Tunis, Tunisia
| | - Mediha Trabelsi
- University of Tunis El Manar, Faculty of Medicine of Tunis, Laboratory of Human Genetics LR99ES10, Tunis, Tunisia
- Department of Congenital and Hereditary Diseases, Charles Nicolle Hospital, Tunis, Tunisia
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Global effects of RAB3GAP1 dysexpression on the proteome of mouse cortical neurons. Amino Acids 2021; 53:1339-1350. [PMID: 34363538 DOI: 10.1007/s00726-021-03058-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 07/30/2021] [Indexed: 12/15/2022]
Abstract
Mounting studies have demonstrated that RAB3GAP1 expression is modified in brain diseases with multiple neurobiological functions and processes and acts as a potentially significant target. However, the cellular and molecular events arising from RAB3GAP1 dysexpression are still incompletely understood. In this work, underexpression and overexpression of RAB3GAP1 were first induced into cultured mouse cortical neurons by transfection with lentivirus plasmids. Then we globally explored the effects of RAB3GAP1 dysexpression on the proteome of the neurons through the use of isobaric tag for relative and absolute quantitation (iTRAQ)-based quantitative proteomics with bioinformatics. A total of 364 proteins in the RAB3GAP1-underexpression group and 314 proteins in the RAB3GAP1-overexpression group were identified to be differentially expressed. Subsequent bioinformatics analysis indicated that the proteome functional expression profiles induced by RAB3GAP1 underexpression and overexpression were different, suggesting the potential differences in biological processes and cellular effects. Subsequent intergroup cross-comparison revealed some candidate target proteins regulated directly by RAB3GAP1. Further parallel reaction monitoring (PRM) analysis illustrated that Sub1, Ssrp1, and Top1 proteins might serve as new potentially important linkers in the RAB3GAP1-mediated autophagy pathway in the cortical neurons. Collectively, the current proteomics data furnished new valuable insights to better understand the regulatory molecular mechanism of neuronal RAB3GAP1.
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Mono-ubiquitination of Rabphilin 3A by UBE3A serves a non-degradative function. Sci Rep 2021; 11:3007. [PMID: 33542309 PMCID: PMC7862399 DOI: 10.1038/s41598-021-82319-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 01/11/2021] [Indexed: 01/30/2023] Open
Abstract
Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by brain-specific loss of UBE3A, an E3 ubiquitin protein ligase. A substantial number of possible ubiquitination targets of UBE3A have been identified, although evidence of being direct UBE3A substrates is often lacking. Here we identified the synaptic protein Rabphilin-3a (RPH3A), an effector of the RAB3A small GTPase involved in axonal vesicle priming and docking, as a ubiquitination target of UBE3A. We found that the UBE3A and RAB3A binding sites on RPH3A partially overlap, and that RAB3A binding to RPH3A interferes with UBE3A binding. We confirmed previous observations that RPH3A levels are critically dependent on RAB3A binding but, rather surprisingly, we found that the reduced RPH3A levels in the absence of RAB3A are not mediated by UBE3A. Indeed, while we found that RPH3A is ubiquitinated in a UBE3A-dependent manner in mouse brain, UBE3A mono-ubiquitinates RPH3A and does not facilitate RPH3A degradation. Moreover, we found that an AS-linked UBE3A missense mutation in the UBE3A region that interacts with RPH3A, abrogates the interaction with RPH3A. In conclusion, our results identify RPH3A as a novel target of UBE3A and suggest that UBE3A-dependent ubiquitination of RPH3A serves a non-degradative function.
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Arakel EC, Huranova M, Estrada AF, Rau EM, Spang A, Schwappach B. Dissection of GTPase-activating proteins reveals functional asymmetry in the COPI coat of budding yeast. J Cell Sci 2019; 132:jcs.232124. [PMID: 31331965 PMCID: PMC6737914 DOI: 10.1242/jcs.232124] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 07/12/2019] [Indexed: 12/11/2022] Open
Abstract
The Arf GTPase controls formation of the COPI vesicle coat. Recent structural models of COPI revealed the positioning of two Arf1 molecules in contrasting molecular environments. Each of these pockets for Arf1 is expected to also accommodate an Arf GTPase-activating protein (ArfGAP). Structural evidence and protein interactions observed between isolated domains indirectly suggest that each niche preferentially recruits one of the two ArfGAPs known to affect COPI, i.e. Gcs1/ArfGAP1 and Glo3/ArfGAP2/3, although only partial structures are available. The functional role of the unique non-catalytic domain of either ArfGAP has not been integrated into the current COPI structural model. Here, we delineate key differences in the consequences of triggering GTP hydrolysis through the activity of one versus the other ArfGAP. We demonstrate that Glo3/ArfGAP2/3 specifically triggers Arf1 GTP hydrolysis impinging on the stability of the COPI coat. We show that the Snf1 kinase complex, the yeast homologue of AMP-activated protein kinase (AMPK), phosphorylates the region of Glo3 that is crucial for this effect and, thereby, regulates its function in the COPI-vesicle cycle. Our results revise the model of ArfGAP function in the molecular context of COPI. This article has an associated First Person interview with the first author of the paper. Highlighted Article: The regulatory domain of the COPI-associated ArfGAP Glo3 can stabilize the COPI coat. GTP hydrolysis is necessary to resolve the stabilised state. This mechanism is regulated by phosphorylation.
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Affiliation(s)
- Eric C Arakel
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Martina Huranova
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.,Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic
| | - Alejandro F Estrada
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - E-Ming Rau
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Anne Spang
- Growth and Development, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Blanche Schwappach
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany .,Max-Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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8
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Dejgaard SY, Presley JF. Rab18: new insights into the function of an essential protein. Cell Mol Life Sci 2019; 76:1935-1945. [PMID: 30830238 PMCID: PMC11105521 DOI: 10.1007/s00018-019-03050-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 02/14/2019] [Accepted: 02/19/2019] [Indexed: 12/14/2022]
Abstract
Rab18 is one of the small number of conserved Rab proteins which have been traced to the last eukaryotic common ancestor. It is found in organisms ranging from humans to trypanosomes, and localizes to multiple organelles, including most notably endoplasmic reticulum and lipid droplets. In humans, absence of Rab18 leads to a severe illness known as Warburg-Micro syndrome. Despite this evidence that Rab18 is essential, its role in cells remains mysterious. However, recent studies identifying effectors and interactors of Rab18, are now shedding light on its mechanism of action, suggesting functions related to organelle tethering and to autophagy. In this review, we examine the variety of roles proposed for Rab18 with a focus on new evidence giving insights into the molecular mechanisms it utilizes. Based on this summary of our current understanding, we identify priority areas for further research.
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Affiliation(s)
- Selma Yilmaz Dejgaard
- Department of Medical Biology, Near East University, Nicosia, Cyprus
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, QC, H3A 0C7, Canada
| | - John F Presley
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, QC, H3A 0C7, Canada.
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9
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Niedergang F, Gasman S, Vitale N, Desnos C, Lamaze C. Meeting after meeting: 20 years of discoveries by the members of the Exocytosis-Endocytosis Club. Biol Cell 2017; 109:339-353. [DOI: 10.1111/boc.201700026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/24/2017] [Accepted: 07/24/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Florence Niedergang
- Institut National de la Santé et de la Recherche Médicale (INSERM); U1016 Institut Cochin Paris France
- Centre National de la Recherche Scientifique (CNRS); UMR 8104 Paris France
- Université Paris Descartes, Sorbonne Paris Cité; Paris France
| | - Stéphane Gasman
- Institut des Neurosciences Cellulaires et Intégratives; CNRS UPR3212; Université de Strasbourg; France
- INSERM; 75654 Paris Cedex 13 France
| | - Nicolas Vitale
- Institut des Neurosciences Cellulaires et Intégratives; CNRS UPR3212; Université de Strasbourg; France
- INSERM; 75654 Paris Cedex 13 France
| | - Claire Desnos
- Université Paris Descartes, Sorbonne Paris Cité; Paris France
- CNRS; UMR 8250 Paris France
| | - Christophe Lamaze
- Institut Curie - Centre de Recherche; PSL Research University; Membrane Dynamics and Mechanics of Intracellular Signaling Laboratory; Paris France
- CNRS; UMR 3666 Paris France
- INSERM; U1143 Paris France
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10
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Rasnitsyn A, Doucette L, Seifi M, Footz T, Raymond V, Walter MA. FOXC1 modulates MYOC secretion through regulation of the exocytic proteins RAB3GAP1, RAB3GAP2 and SNAP25. PLoS One 2017; 12:e0178518. [PMID: 28575017 PMCID: PMC5456087 DOI: 10.1371/journal.pone.0178518] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 05/15/2017] [Indexed: 11/19/2022] Open
Abstract
The neurodegenerative disease glaucoma is one of the leading causes of blindness in the world. Glaucoma is characterized by progressive visual field loss caused by retinal ganglion cell (RGC) death. Both surgical glaucoma treatments and medications are available, however, they only halt glaucoma progression and are unable to reverse damage. Furthermore, many patients do not respond well to treatments. It is therefore important to better understand the mechanisms involved in glaucoma pathogenesis. Patients with Axenfeld-Rieger syndrome (ARS) offer important insight into glaucoma progression. ARS patients are at 50% risk of developing early onset glaucoma and respond poorly to treatments, even when surgical treatments are combined with medications. Mutations in the transcription factor FOXC1 cause ARS. Alterations in FOXC1 levels cause ocular malformations and disrupt stress response in ocular tissues, thereby contributing to glaucoma progression. In this study, using biochemical and molecular techniques, we show that FOXC1 regulates the expression of RAB3GAP1, RAB3GAP2 and SNAP25, three genes with central roles in both exocytosis and endocytosis, responsible for extracellular trafficking. FOXC1 positively regulates RAB3GAP1 and RAB3GAP2, while either increase or decrease in FOXC1 levels beyond its normal range results in decreased SNAP25. In addition, we found that FOXC1 regulation of RAB3GAP1, RAB3GAP2 and SNAP25 affects secretion of Myocilin (MYOC), a protein associated with juvenile onset glaucoma and steroid-induced glaucoma. The present work reveals that FOXC1 is an important regulator of exocytosis and establishes a new link between FOXC1 and MYOC-associated glaucoma.
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Affiliation(s)
- Alexandra Rasnitsyn
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Lance Doucette
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Morteza Seifi
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Tim Footz
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Vincent Raymond
- Centre Hospitalier de l'Université Laval (CHUL) Quebec City, Québec, Canada
| | - Michael A. Walter
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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Abstract
Rab proteins are the major regulators of vesicular trafficking in eukaryotic cells. Their activity can be tightly controlled within cells: Regulated by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), they switch between an active GTP-bound state and an inactive GDP-bound state, interacting with downstream effector proteins only in the active state. Additionally, they can bind to membranes via C-terminal prenylated cysteine residues and they can be solubilized and shuttled between membranes by chaperone-like molecules called GDP dissociation inhibitors (GDIs). In this review we give an overview of Rab proteins with a focus on the current understanding of their regulation by GEFs, GAPs and GDI.
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Affiliation(s)
- Matthias P Müller
- a Department of Structural Biochemistry , Max Planck Institute of Molecular Physiology , Dortmund , Germany
| | - Roger S Goody
- a Department of Structural Biochemistry , Max Planck Institute of Molecular Physiology , Dortmund , Germany
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12
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Spang N, Feldmann A, Huesmann H, Bekbulat F, Schmitt V, Hiebel C, Koziollek-Drechsler I, Clement AM, Moosmann B, Jung J, Behrends C, Dikic I, Kern A, Behl C. RAB3GAP1 and RAB3GAP2 modulate basal and rapamycin-induced autophagy. Autophagy 2015; 10:2297-309. [PMID: 25495476 PMCID: PMC4502700 DOI: 10.4161/15548627.2014.994359] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Macroautophagy is a degradative pathway that sequesters and transports cytosolic cargo in autophagosomes to lysosomes, and its deterioration affects intracellular proteostasis. Membrane dynamics accompanying autophagy are mostly elusive and depend on trafficking processes. RAB GTPase activating proteins (RABGAPs) are important factors for the coordination of cellular vesicle transport systems, and several TBC (TRE2-BUB2-CDC16) domain-containing RABGAPs are associated with autophagy. Employing C. elegans and human primary fibroblasts, we show that RAB3GAP1 and RAB3GAP2, which are components of the TBC domain-free RAB3GAP complex, influence protein aggregation and affect autophagy at basal and rapamycin-induced conditions. Correlating the activity of RAB3GAP1/2 with ATG3 and ATG16L1 and analyzing ATG5 punctate structures, we illustrate that the RAB3GAPs modulate autophagosomal biogenesis. Significant levels of RAB3GAP1/2 colocalize with members of the Atg8 family at lipid droplets, and their autophagy modulatory activity depends on the GTPase-activating activity of RAB3GAP1 but is independent of the RAB GTPase RAB3. Moreover, we analyzed RAB3GAP1/2 in relation to the previously reported suppressive autophagy modulators FEZ1 and FEZ2 and demonstrate that both reciprocally regulate autophagy. In conclusion, we identify RAB3GAP1/2 as novel conserved factors of the autophagy and proteostasis network.
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Key Words
- ATG, autophagy-related
- ATG16L1
- ATG3
- BSA, bovine serum albumin
- Bafi, bafilomycin A1
- C. elegans, Caenorhabditis elegans
- CALCOCO2, calcium binding and coiled-coil domain 2
- DAPI, 4’, 6-diamidino-2-phenylindole
- DMSO, dimethyl sulfoxide
- DPH, 1, 6-diphenyl-1, 3, 5-hexatriene
- FEZ, fasciculation and elongation protein zeta
- FEZ1
- FEZ2
- GABARAP, GABA(A) receptor-associated protein
- GEF, guanine nucleotide exchange factor
- GFP, green fluorescent protein
- MAP1LC3, microtubule-associated protein 1 light chain 3
- NBR1, neighbor of BRCA1 gene 1
- PBS, phosphate-buffered saline
- PE, phosphatidylethanolamine
- RAB3GAP1
- RAB3GAP2
- RABGAP, RAB GTPase activating protein
- SQSTM1, sequestosome 1
- TBC domain, TRE2-BUB2-CDC16 domain
- autophagy
- eV, empty vector
- lipid droplets
- proteostasis
- siRNA, small interfering RNA
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Affiliation(s)
- Natalie Spang
- a Institute for Pathobiochemistry ; University Medical Center of the Johannes Gutenberg University ; Mainz , Germany
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13
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Abstract
Micro syndrome (OMIM 60018) and Martsolf syndrome (OMIM 21270) are related rare autosomal recessive disorders characterized by ocular and neurological abnormalities and hypothalamic hypogonadism. Micro syndrome has been associated with causative mutations in three disease genes: RAB3GAP1, RAB3GAP2 and RAB18. Martsolf syndrome has been associated with a mutation in RAB3GAP2. The present review summarizes the current literature on these genes and the proteins they encode.
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Abstract
Small GTPases use GDP/GTP alternation to actuate a variety of functional switches that are pivotal for cell dynamics. The GTPase switch is turned on by GEFs, which stimulate dissociation of the tightly bound GDP, and turned off by GAPs, which accelerate the intrinsically sluggish hydrolysis of GTP. For Ras, Rho, and Rab GTPases, this switch incorporates a membrane/cytosol alternation regulated by GDIs and GDI-like proteins. The structures and core mechanisms of representative members of small GTPase regulators from most families have now been elucidated, illuminating their general traits combined with scores of unique features. Recent studies reveal that small GTPase regulators have themselves unexpectedly sophisticated regulatory mechanisms, by which they process cellular signals and build up specific cell responses. These mechanisms include multilayered autoinhibition with stepwise release, feedback loops mediated by the activated GTPase, feed-forward signaling flow between regulators and effectors, and a phosphorylation code for RhoGDIs. The flipside of these highly integrated functions is that they make small GTPase regulators susceptible to biochemical abnormalities that are directly correlated with diseases, notably a striking number of missense mutations in congenital diseases, and susceptible to bacterial mimics of GEFs, GAPs, and GDIs that take command of small GTPases in infections. This review presents an overview of the current knowledge of these many facets of small GTPase regulation.
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Affiliation(s)
- Jacqueline Cherfils
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Centre deRecherche de Gif, Gif-sur-Yvette, France
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Chen KY, Tsai PC, Liu YW, Lee FJS. Competition between the golgin Imh1p and the GAP Gcs1p stabilizes activated Arl1p at the late-Golgi. J Cell Sci 2012; 125:4586-96. [PMID: 22767516 DOI: 10.1242/jcs.107797] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Golgins play diverse roles in regulating the structure and function of the Golgi. The yeast golgin Imh1p is targeted to the trans-Golgi network (TGN) through interaction of its GRIP domain with GTP-bound Arl1p. Recycling of Arl1p and Imh1p to the cytosol requires the hydrolysis of GTP bound to Arl1p; however, the point at which GTP hydrolysis occurs remains unknown. Here, we report that self-interaction of Imh1p plays a role in modulating spatial inactivation of Arl1p. Deletion of IMH1 in yeast decreases the amount of the GTP-bound Arl1p and results in less Arl1p residing on the TGN. Biochemically, purified Imh1p competes with Gcs1p, an Arl1p GTPase-activating protein (GAP), for binding to Arl1p, thus interfering with the GAP activity of Gcs1p toward Arl1p. Furthermore, we demonstrate that the self-interaction of Imh1p attenuates the Gcs1p-dependent GTP hydrolysis of Arl1p. Thus, we propose that the golgin Imh1p serves as a feedback regulator to modulate the GTP hydrolysis of Arl1p.
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Affiliation(s)
- Kuan-Yu Chen
- Institute of Molecular Medicine, College of Medicine, National Taiwan University and Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan
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16
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Müller M, Pym ECG, Tong A, Davis GW. Rab3-GAP controls the progression of synaptic homeostasis at a late stage of vesicle release. Neuron 2011; 69:749-62. [PMID: 21338884 DOI: 10.1016/j.neuron.2011.01.025] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2010] [Indexed: 12/25/2022]
Abstract
Homeostatic signaling systems stabilize neural function through the modulation of neurotransmitter receptor abundance, ion channel density, and presynaptic neurotransmitter release. Molecular mechanisms that drive these changes are being unveiled. In theory, molecular mechanisms may also exist to oppose the induction or expression of homeostatic plasticity, but these mechanisms have yet to be explored. In an ongoing electrophysiology-based genetic screen, we have tested 162 new mutations for genes involved in homeostatic signaling at the Drosophila NMJ. This screen identified a mutation in the rab3-GAP gene. We show that Rab3-GAP is necessary for the induction and expression of synaptic homeostasis. We then provide evidence that Rab3-GAP relieves an opposing influence on homeostasis that is catalyzed by Rab3 and which is independent of any change in NMJ anatomy. These data define roles for Rab3-GAP and Rab3 in synaptic homeostasis and uncover a mechanism, acting at a late stage of vesicle release, that opposes the progression of homeostatic plasticity.
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Affiliation(s)
- Martin Müller
- Department of Biochemistry and Biophysics, 1550 4th Street, Rock Hall 4th Floor North, University of California, San Francisco, San Francisco, CA 94158, USA
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17
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Barr F, Lambright DG. Rab GEFs and GAPs. Curr Opin Cell Biol 2010; 22:461-70. [PMID: 20466531 DOI: 10.1016/j.ceb.2010.04.007] [Citation(s) in RCA: 337] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 04/05/2010] [Accepted: 04/16/2010] [Indexed: 10/19/2022]
Abstract
Rabs are GTP-binding proteins with conserved functions in membrane trafficking. They are regulated by a diverse group of structurally unrelated GDP-GTP exchange factors (GEFs), and a family of GTP-hydrolysis activating proteins (GAPs) containing the conserved TBC domain. Recent structural and cell biological studies shed new light on the mechanisms of Rab GEF and GAP action, and the cellular trafficking pathways they act in.
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Affiliation(s)
- Francis Barr
- University of Liverpool, Cancer Research Centre, 200 London Road, Liverpool L3 9TA, UK.
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18
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Chia WJ, Tang BL. Emerging roles for Rab family GTPases in human cancer. Biochim Biophys Acta Rev Cancer 2009; 1795:110-6. [PMID: 19425190 DOI: 10.1016/j.bbcan.2008.10.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Member of the Ras-associated binding (Rab) family of small GTPases function as molecular switches regulating vesicular transport in eukaryotes cells. Their pathophysiological roles in human malignancies are less well-known compared to members of Ras and Rho families. Several members of the Rab family have, however, been shown to be aberrantly expressed in various cancer tissues. Recent findings have also revealed , in particular, Rab25 as a determinant of tumor progression and aggressiveness of epithelial cancers. Rab25 associates with alpha5beta1 integrin, and enhances tumor cell invasion by directing the localization of integrin-containing vesicles to the leading edge of matrix invading pseudopodia. We summarized here recent integrin on Rab25 and other Rabs implicated to be involved in a variety of human cancers, and discussed plausible mechanisms of how dysregulation of Rab expression could be tumorigenic or tumor suppressive.
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Affiliation(s)
- Wan Jie Chia
- Department of Biochemistry,Yong Loo Lin School of Medicine, national University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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19
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Chapter 5: rab proteins and their interaction partners. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 274:235-74. [PMID: 19349039 DOI: 10.1016/s1937-6448(08)02005-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Ras superfamily consists of over 150 low molecular weight proteins that cycle between an inactive guanosine diphosphate (GDP)-bound state and an active guanosine triphosphate (GTP)-bound state. They are involved in a variety of signal transduction pathways that regulate cell growth, intracellular trafficking, cell migration, and apoptosis. Several methods have been devised to detect and characterize the interacting partners of small GTPases with the aim of better understanding their physiological function in normal cells and tumor cells. The Rab (Ras analog in brain) proteins form the largest family within the Ras superfamily. Rab proteins regulate vesicular trafficking pathways, behaving as membrane-associated molecular switches. The guanine nucleotide-binding status of Rab proteins is modulated by three different classes of regulatory proteins, which have been extensively studied for the Rab molecules but also for other subfamilies of the Ras superfamily. Furthermore, numerous effector molecules have been isolated especially for the Rab subfamily of proteins, which interact via a Rab-binding domain (RBD) and are recruited afterwards to specific sub-cellular compartments by the Rab proteins.
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20
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Ng EL, Tang BL. Rab GTPases and their roles in brain neurons and glia. ACTA ACUST UNITED AC 2008; 58:236-46. [PMID: 18485483 DOI: 10.1016/j.brainresrev.2008.04.006] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 02/29/2008] [Accepted: 04/06/2008] [Indexed: 12/19/2022]
Affiliation(s)
- Ee Ling Ng
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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21
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Signaling cascades as cellular devices for spatial computations. J Math Biol 2008; 58:35-55. [PMID: 18283462 DOI: 10.1007/s00285-008-0162-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 01/17/2008] [Indexed: 10/22/2022]
Abstract
Signaling networks usually include protein-modification cycles. Cascades of such cycles are the backbones of multiple signaling pathways. Protein gradients emerge from the spatial separation of opposing enzymes, such as kinases and phosphatases, or guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) for GTPase cycles. We show that different diffusivities of an active protein form and an inactive form leads to spatial gradients of protein abundance in the cytoplasm. For a cascade of cycles, using a discrete approximation of the space, we derive an analytical expression for the spatial gradients and show that it converges to an exact solution with decreasing the size of the quantization. Our results facilitate quantitative analysis of the dependence of spatial gradients on the network topology and reaction kinetics. We demonstrate how different cascade designs filter and process the input information to generate precise, complex spatial guidance for multiple GTPase effector processes. Thus, protein-modification cascades may serve as devices to compute complex spatial distributions of target proteins within intracellular space.
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22
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Assmann EM, Alborghetti MR, Camargo MER, Kobarg J. FEZ1 dimerization and interaction with transcription regulatory proteins involves its coiled-coil region. J Biol Chem 2006; 281:9869-81. [PMID: 16484223 DOI: 10.1074/jbc.m513280200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The fasciculation and elongation protein zeta1 (FEZ1) is a mammalian orthologue of the Caenorhabditis elegans protein UNC-76, which is necessary for axon growth in that nematode. In previous studies FEZ1 has been found to interact with protein kinase Czeta, DISC1, the agnoprotein of the human polyomavirus JC virus, and E4B, a U-box-type ubiquitin-protein isopeptide ligase. We reported previously that FEZ1 and its paralogue FEZ2 are proteins that interact with NEK1, a protein kinase involved in polycystic kidney disease and DNA repair mechanisms at the G(2)/M phase of the cell cycle. Here we report the identification of 16 proteins that interact with human FEZ1-(221-396) in a yeast two-hybrid assay of a human fetal brain cDNA library. The 13 interacting proteins of known functions take part either in transcription regulation and chromatin remodeling (6 proteins), the regulation of neuronal cell development (2 proteins) and cellular transport mechanisms (3 proteins) or participate in apoptosis (2 proteins). We were able to confirm eight of the observed interactions by in vitro pull-down assays with recombinant fusion proteins. The confirmed interacting proteins include FEZ1 itself and three transcription controlling proteins (SAP30L, DRAP1, and BAF60a). In mapping studies we found that the C-terminal regions of FEZ1, and especially its coiled-coil region, are involved in its dimerization, its heterodimerization with FEZ2, and in the interaction with 10 of the identified interacting proteins. Our results give further support to the previous speculation of the functional involvement of FEZ1 in neuronal development but suggest further that FEZ1 may also be involved in transcriptional control.
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Affiliation(s)
- Eliana M Assmann
- Centro de Biologia Molecular Estrutural, Laboratório Nacional de Luz Síncrotron, Rua Giuseppe Máximo Scolfaro 10.000, CP 6192, 13084-971 Campinas, SP, Brasil
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23
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Heo JB, Rho HS, Kim SW, Hwang SM, Kwon HJ, Nahm MY, Bang WY, Bahk JD. OsGAP1 functions as a positive regulator of OsRab11-mediated TGN to PM or vacuole trafficking. PLANT & CELL PHYSIOLOGY 2005; 46:2005-18. [PMID: 16230331 DOI: 10.1093/pcp/pci215] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The Ypt/Rab family of small G-proteins is important in regulating vesicular transport. Rabs hydrolyze GTP very slowly on their own and require GTPase-activating proteins (GAPs). Here we report the identification and characterization of OsGAP1, a Rab-specific rice GAP. OsGAP1 strongly stimulated OsRab8a and OsRab11, which are homologs of the mammalian Rab8 and Rab11 proteins that are essential for Golgi to plasma membrane (PM) and trans-Golgi network (TGN) to PM trafficking, respectively. Substitution of two invariant arginines within the catalytic domain of Oryza sativa GTPase-activating protein 1 (OsGAP1) with alanines significantly inhibited its GAP activity. In vivo targeting experiments revealed that OsGAP1 localizes to the TGN or pre-vacuolar compartment (PVC). A yeast expression system demonstrated that wild-type OsGAP1 facilitates O. sativa dissociation inhibitor 3 (OsGDI3)-catalyzed OsRab11 recycling at an early stage, but the OsGAP1(R385A) and (R450A) mutants do not. Thus, GTP hydrolysis is essential for Rab recycling. Moreover, expression of the OsGAP1 mutants in Arabidopsis protoplasts inhibited the trafficking of some cargo proteins, including the PM-localizing H+-ATPase-green fluorescent protein (GFP) and Ca2+-ATPase8-GFP and the central vacuole-localizing Arabidopsis aleurain-like protein (AALP)-GFP. The OsGAP1 mutants caused these proteins to accumulate at the Golgi apparatus. Surprisingly, OsRab11 overproduction relieved the inhibitory effect of the OsGAP1 mutants on vesicular trafficking. OsRab8a had no such effect. Thus, the OsGAP1 mutants may inhibit TGN to PM or central vacuole trafficking because they induce the sequestration of endogenous Rab11. We propose that OsGAP1 facilitates vesicular trafficking from the TGN to the PM or central vacuole by both stimulating the GTPase activity of OsRab11 and increasing the recycling of inactive OsRab11.
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Affiliation(s)
- Jae Bok Heo
- Division of Applied Life Sciences, Graduate School of Gyeongsang National University, Jinju 660-701, Korea
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24
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Giovedì S, Darchen F, Valtorta F, Greengard P, Benfenati F. Synapsin is a novel Rab3 effector protein on small synaptic vesicles. II. Functional effects of the Rab3A-synapsin I interaction. J Biol Chem 2004; 279:43769-79. [PMID: 15265868 DOI: 10.1074/jbc.m404168200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synapsins, a family of neuron-specific phosphoproteins that play an important role in the regulation of synaptic vesicle trafficking and neurotransmitter release, were recently demonstrated to interact with the synaptic vesicle-associated small G protein Rab3A within nerve terminals (Giovedi, S., Vaccaro, P., Valtorta, F., Darchen, F., Greengard, P., Cesareni, G., and Benfenati, F. (2004) J. Biol. Chem. 279, 43760-43768). We have analyzed the functional consequences of this interaction on the biological activities of both proteins and on their subcellular distribution within nerve terminals. The presence of synapsin I stimulated GTP binding and GTPase activity of both purified and endogenous synaptic vesicle-associated Rab3A. Conversely, Rab3A inhibited synapsin I binding to F-actin, as well as synapsin-induced actin bundling and vesicle clustering. Moreover, the amount of Rab3A associated with synaptic vesicles was decreased in synapsin knockout mice, and the presence of synapsin I prevented RabGDI-induced Rab3A dissociation from synaptic vesicles. The results indicate that an interaction between synapsin I and Rab3A exists on synaptic vesicles that modulates the functional properties of both proteins. Given the well recognized importance of both synapsins and Rab3A in synaptic vesicles exocytosis, this interaction is likely to play a major role in the modulation of neurotransmitter release.
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Affiliation(s)
- Silvia Giovedì
- Department of Experimental Medicine, Section of Human Physiology, University of Genova, Via Benedetto XV, 16132, Italy
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25
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Thiagarajan R, Tewolde T, Li Y, Becker PL, Rich MM, Engisch KL. Rab3A negatively regulates activity-dependent modulation of exocytosis in bovine adrenal chromaffin cells. J Physiol 2003; 555:439-57. [PMID: 14694148 PMCID: PMC1664839 DOI: 10.1113/jphysiol.2003.056333] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Members of the Rab family of monomeric GTPases have been implicated in vesicle trafficking, and Rab3A, located on synaptic vesicles in neurones and secretory vesicles in neuroendocrine cells, is likely to be involved in vesicle fusion leading to neurotransmitter release. A hydrolysis-deficient mutant of Rab3A, Rab3AQ81L, has been shown to potently inhibit hormone release. Here we show that the inhibition of hormone release by Rab3AQ81L is activity-dependent. Bovine adrenal chromaffin cells were induced to express Rab3AQ81L and green fluorescent protein by adenoviral gene transfer of a bicistronic construct. Fluorescent cells were stimulated with single depolarizations and trains of depolarizing pulses in whole cell perforated patch clamp recordings, and exocytosis was detected with cell capacitance measurements and carbon fibre amperometry. When single depolarizations were used to evoke exocytosis, cells expressing Rab3AQ81L showed a 50% reduction in response amplitude. When trains of brief depolarizations (10 or 40 ms) were used to evoke exocytosis, responses rapidly declined to zero in cells expressing Rab3AQ81L. Wild-type Rab3A had effects similar to Rab3AQ81L, causing significant inhibition of exocytosis only during repetitive stimulation. Expression of Rab5A did not alter exocytosis evoked by single depolarizations or repetitive stimulation. Applying a long duration depolarization in the middle of a stimulus train revealed that exocytotic efficacy (capacitance increase per amount of calcium influx) was not decreased in Rab3AQ81L-expressing cells. Instead, the activity-dependent increase in exocytotic efficacy observed in control cells did not occur in Rab3AQ81L-expressing cells. Our results suggest that Rab3A in the GTP bound conformation prevents activity-dependent facilitation.
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Affiliation(s)
- Ramachandran Thiagarajan
- Department of Physiology, Emory University School of Medicine, 605-J Whitehead Research Building, 615 Michael Street, Atlanta, GA 30322, USA
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26
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Taraschi TF, O'Donnell M, Martinez S, Schneider T, Trelka D, Fowler VM, Tilley L, Moriyama Y. Generation of an erythrocyte vesicle transport system by Plasmodium falciparum malaria parasites. Blood 2003; 102:3420-6. [PMID: 12869498 DOI: 10.1182/blood-2003-05-1448] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The asexual maturation of Plasmodium falciparum is accompanied by the transport of parasite-encoded proteins to the erythrocyte plasma membrane. Activation of G proteins by treatment with aluminum fluoride produced an accumulation within the erythrocyte cytosol of vesicles coated with Plasmodium homologues of COPII and N-ethylmaleimide-sensitive factor, proteins involved in intracellular transport between the Golgi apparatus and the endoplasmic reticulum. These vesicles contain malarial proteins that appear on the erythrocyte plasma membrane, as well as actin and myosin. It is proposed that the parasite adapted a process well established for intracellular transport to mediate the extracellular movement of its proteins through the erythrocyte cytosol to the surface membrane.
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Affiliation(s)
- Theodore F Taraschi
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA 19107, USA.
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27
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Bernards A. GAPs galore! A survey of putative Ras superfamily GTPase activating proteins in man and Drosophila. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1603:47-82. [PMID: 12618308 DOI: 10.1016/s0304-419x(02)00082-3] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Typical members of the Ras superfamily of small monomeric GTP-binding proteins function as regulators of diverse processes by cycling between biologically active GTP- and inactive GDP-bound conformations. Proteins that control this cycling include guanine nucleotide exchange factors or GEFs, which activate Ras superfamily members by catalyzing GTP for GDP exchange, and GTPase activating proteins or GAPs, which accelerate the low intrinsic GTP hydrolysis rate of typical Ras superfamily members, thus causing their inactivation. Two among the latter class of proteins have been implicated in common genetic disorders associated with an increased cancer risk, neurofibromatosis-1, and tuberous sclerosis. To facilitate genetic analysis, I surveyed Drosophila and human sequence databases for genes predicting proteins related to GAPs for Ras superfamily members. Remarkably, close to 0.5% of genes in both species (173 human and 64 Drosophila genes) predict proteins related to GAPs for Arf, Rab, Ran, Rap, Ras, Rho, and Sar family GTPases. Information on these genes has been entered into a pair of relational databases, which can be used to identify evolutionary conserved proteins that are likely to serve basic biological functions, and which can be updated when definitive information on the coding potential of both genomes becomes available.
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Affiliation(s)
- André Bernards
- Massachusetts General Hospital Cancer Center, Building 149, 13th Street, Charlestown, MA 02129-2000, USA.
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28
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Puertollano R, Randazzo PA, Presley JF, Hartnell LM, Bonifacino JS. The GGAs promote ARF-dependent recruitment of clathrin to the TGN. Cell 2001; 105:93-102. [PMID: 11301005 DOI: 10.1016/s0092-8674(01)00299-9] [Citation(s) in RCA: 226] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The GGAs constitute a family of modular adaptor-related proteins that bind ADP-ribosylation factors (ARFs) and localize to the trans-Golgi network (TGN) via their GAT domains. Here, we show that binding of the GAT domain stabilizes membrane-bound ARF1.GTP due to interference with the action of GTPase-activating proteins. We also show that the hinge and ear domains of the GGAs interact with clathrin in vitro, and that the GGAs promote recruitment of clathrin to liposomes in vitro and to TGN membranes in vivo. These observations suggest that the GGAs could function to link clathrin to membrane-bound ARF.GTP.
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Affiliation(s)
- R Puertollano
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
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