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Martinez-Arroyo O, Flores-Chova A, Sanchez-Garcia B, Redon J, Cortes R, Ortega A. Rab3A/Rab27A System Silencing Ameliorates High Glucose-Induced Injury in Podocytes. BIOLOGY 2023; 12:biology12050690. [PMID: 37237503 DOI: 10.3390/biology12050690] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/04/2023] [Accepted: 05/06/2023] [Indexed: 05/28/2023]
Abstract
Diabetic nephropathy is a major complication in diabetic patients. Podocytes undergo loss and detachment from the basal membrane. Intra- and intercellular communication through exosomes are key processes for maintaining function, and the Rab3A/Rab27A system is an important counterpart. Previously, we observed significant changes in the Rab3A/Rab27A system in podocytes under glucose overload, demonstrating its important role in podocyte injury. We investigated the implication of silencing the Rab3A/Rab27A system in high glucose-treated podocytes and analysed the effect on differentiation, apoptosis, cytoskeletal organisation, vesicle distribution, and microRNA expression in cells and exosomes. For this, we subjected podocytes to high glucose and transfection through siRNAs, and we isolated extracellular vesicles and performed western blotting, transmission electron microscopy, RT-qPCR, immunofluorescence and flow cytometry assays. We found that silencing RAB3A and RAB27A generally leads to a decrease in podocyte differentiation and cytoskeleton organization and an increase in apoptosis. Moreover, CD63-positive vesicles experienced a pattern distribution change. Under high glucose, Rab3A/Rab27A silencing ameliorates some of these detrimental processes, suggesting a differential influence depending on the presence or absence of cellular stress. We also observed substantial expression changes in miRNAs that were relevant in diabetic nephropathy upon silencing and glucose treatment. Our findings highlight the Rab3A/Rab27A system as a key participant in podocyte injury and vesicular traffic regulation in diabetic nephropathy.
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Affiliation(s)
- Olga Martinez-Arroyo
- Cardiometabolic and Renal Risk Research Group, Biomedical Research Institute of Hospital Clinico de Valencia INCLIVA, 46010 Valencia, Spain
| | - Ana Flores-Chova
- Cardiometabolic and Renal Risk Research Group, Biomedical Research Institute of Hospital Clinico de Valencia INCLIVA, 46010 Valencia, Spain
| | - Belen Sanchez-Garcia
- Cardiometabolic and Renal Risk Research Group, Biomedical Research Institute of Hospital Clinico de Valencia INCLIVA, 46010 Valencia, Spain
| | - Josep Redon
- Cardiometabolic and Renal Risk Research Group, Biomedical Research Institute of Hospital Clinico de Valencia INCLIVA, 46010 Valencia, Spain
- CIBEROBN (CIBER of Obesity and Nutrition Physiopathology), Institute of Health Carlos III, Minister of Health, 28029 Madrid, Spain
| | - Raquel Cortes
- Cardiometabolic and Renal Risk Research Group, Biomedical Research Institute of Hospital Clinico de Valencia INCLIVA, 46010 Valencia, Spain
| | - Ana Ortega
- Cardiometabolic and Renal Risk Research Group, Biomedical Research Institute of Hospital Clinico de Valencia INCLIVA, 46010 Valencia, Spain
- CIBERCV (CIBER of Cardiovascular Diseases), Institute of Health Carlos III, Minister of Health, 28029 Madrid, Spain
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2
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Izumi T. In vivo Roles of Rab27 and Its Effectors in Exocytosis. Cell Struct Funct 2021; 46:79-94. [PMID: 34483204 PMCID: PMC10511049 DOI: 10.1247/csf.21043] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
The monomeric GTPase Rab27 regulates exocytosis of a broad range of vesicles in multicellular organisms. Several effectors bind GTP-bound Rab27a and/or Rab27b on secretory vesicles to execute a series of exocytic steps, such as vesicle maturation, movement along microtubules, anchoring within the peripheral F-actin network, and tethering to the plasma membrane, via interactions with specific proteins and membrane lipids in a local milieu. Although Rab27 effectors generally promote exocytosis, they can also temporarily restrict it when they are involved in the rate-limiting step. Genetic alterations in Rab27-related molecules cause discrete diseases manifesting pigment dilution and immunodeficiency, and can also affect common diseases such as diabetes and cancer in complex ways. Although the function and mechanism of action of these effectors have been explored, it is unclear how multiple effectors act in coordination within a cell to regulate the secretory process as a whole. It seems that Rab27 and various effectors constitutively reside on individual vesicles to perform consecutive exocytic steps. The present review describes the unique properties and in vivo roles of the Rab27 system, and the functional relationship among different effectors coexpressed in single cells, with pancreatic beta cells used as an example.Key words: membrane trafficking, regulated exocytosis, insulin granules, pancreatic beta cells.
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Affiliation(s)
- Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
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3
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Arias-Hervert ER, Xu N, Njus M, Murphy GG, Hou Y, Williams JA, Lentz SI, Ernst SA, Stuenkel EL. Actions of Rab27B-GTPase on mammalian central excitatory synaptic transmission. Physiol Rep 2021; 8:e14428. [PMID: 32358861 PMCID: PMC7195558 DOI: 10.14814/phy2.14428] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 03/26/2020] [Accepted: 03/30/2020] [Indexed: 12/20/2022] Open
Abstract
Members of the Rab3 gene family are considered central to membrane trafficking of synaptic vesicles at mammalian central excitatory synapses. Recent evidence, however, indicates that the Rab27B-GTPase, which is highly homologous to the Rab3 family, is also enriched on SV membranes and co-localize with Rab3A and Synaptotagmin at presynaptic terminals. While functional roles of Rab3A have been well-established, little functional information exists on the role of Rab27B in synaptic transmission. Here we report on functional effects of Rab27B at SC-CA1 and DG-MF hippocampal synapses. The data establish distinct functional actions of Rab27B and demonstrate functions of Rab27B that differ between SC-CA1 and DG-MF synapses. Rab27B knockout reduced frequency facilitation compared to wild-type (WT) controls at the DG/MF-CA3 synaptic region, while increasing facilitation at the SC-CA1 synaptic region. Remarkably, Rab27B KO resulted in a complete elimination of LTP at the MF-CA3 synapse with no effect at the SC-CA1 synapse. These actions are similar to those previously reported for Rab3A KO. Specificity of action on LTP to Rab27B was confirmed as LTP was rescued in response to lentiviral infection and expression of human Rab27B, but not to GFP, in the DG in the Rab27B KO mice. Notably, the effect of Rab27B KO on MF-CA3 LTP occurred in spite of continued expression of Rab3A in the Rab27B KO. Overall, the results provide a novel perspective in suggesting that Rab27B and Rab3A act synergistically, perhaps via sequential effector recruitment or signaling for presynaptic LTP expression in this hippocampal synaptic region.
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Affiliation(s)
- Erwin R Arias-Hervert
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA
| | - Nicole Xu
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA
| | - Meredith Njus
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA
| | - Geoff G Murphy
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA.,Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
| | - Yanan Hou
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA
| | - John A Williams
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA.,Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Stephen I Lentz
- Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Stephen A Ernst
- Cell & Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Edward L Stuenkel
- Molecular & Integrative Physiology Department, University of Michigan, Ann Arbor, MI, USA
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4
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Abu-Libdeh B, Mor-Shaked H, Atawna AA, Gillis D, Halstuk O, Shaul-Lotan N, Slae M, Sultan M, Meiner V, Elpeleg O, Harel T. Homozygous variant in MADD, encoding a Rab guanine nucleotide exchange factor, results in pleiotropic effects and a multisystemic disorder. Eur J Hum Genet 2021; 29:977-987. [PMID: 33723354 DOI: 10.1038/s41431-021-00844-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 01/20/2021] [Accepted: 02/24/2021] [Indexed: 12/20/2022] Open
Abstract
Rab proteins coordinate inter-organellar vesicle-mediated transport, facilitating intracellular communication, protein recycling, and signaling processes. Dysfunction of Rab proteins or their direct interactors leads to a wide range of diseases with diverse manifestations. We describe seven individuals from four consanguineous Arab Muslim families with an infantile-lethal syndrome, including failure to thrive (FTT), chronic diarrhea, neonatal respiratory distress, variable pituitary dysfunction, and distal arthrogryposis. Exome sequencing analysis in the independent families, followed by an internal gene-matching process using a local exome database, identified a homozygous splice-site variant in MADD (c.2816 + 1 G > A) on a common haplotype. The variant segregated with the disease in all available family members. Determination of cDNA sequence verified single exon skipping, resulting in an out-of-frame deletion. MADD encodes a Rab guanine nucleotide exchange factor (GEF), which activates RAB3 and RAB27A/27B and is thus a crucial regulator of neuromuscular junctions and endocrine secretory granule release. Moreover, MADD protects cells from caspase-mediated TNF-α-induced apoptosis. The combined roles of MADD and its downstream effectors correlate with the phenotypic spectrum of disease, and call for additional studies to confirm the pathogenic mechanism and to investigate possible therapeutic avenues through modulation of TNF-α signaling.
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Affiliation(s)
- Bassam Abu-Libdeh
- Department of Pediatrics, Makassed Hospital and Faculty of Medicine, Al-Quds University, East Jerusalem, Palestine
| | - Hagar Mor-Shaked
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel.,Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Amir A Atawna
- Department of Neonatology, Makassed Hospital, East Jerusalem, Palestine
| | - David Gillis
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.,Department of Pediatrics, Hadassah Medical Center, Jerusalem, Israel
| | - Orli Halstuk
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel.,Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nava Shaul-Lotan
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
| | - Mordechai Slae
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.,Department of Pediatrics, Hadassah Medical Center, Jerusalem, Israel
| | - Mutaz Sultan
- Department of Pediatrics, Makassed Hospital and Faculty of Medicine, Al-Quds University, East Jerusalem, Palestine
| | - Vardiella Meiner
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel.,Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Orly Elpeleg
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel.,Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Harel
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel. .,Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.
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5
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Ma CIJ, Brill JA. Endosomal Rab GTPases regulate secretory granule maturation in Drosophila larval salivary glands. Commun Integr Biol 2021; 14:15-20. [PMID: 33628358 PMCID: PMC7889263 DOI: 10.1080/19420889.2021.1874663] [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] [Indexed: 02/07/2023] Open
Abstract
Secretory granules (SGs) are organelles responsible for regulated exocytosis of biologically active molecules in professional secretory cells. Maturation of SGs is a crucial process in which cargoes of SGs are processed and activated, allowing them to exert their function upon secretion. Nonetheless, the intracellular trafficking pathways required for SG maturation are not well defined. We recently performed an RNA interference (RNAi) screen in Drosophila larval salivary glands to identify trafficking components needed for SG maturation. From the screen, we identified several Rab GTPases (Rabs) that affect SG maturation. Expression of constitutively active (CA) and dominant-negative (DN) forms narrowed down the Rabs important for this process to Rab5, Rab9 and Rab11. However, none of these Rabs localizes to the limiting membrane of SGs. In contrast, examination of endogenously YFP-tagged Rabs (YRabs) in larval salivary glands revealed that YRab1 and YRab6 localize to the limiting membrane of immature SGs (iSGs) and SGs. These findings provide new insights into how Rab GTPases contribute to the process of SG maturation.
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Affiliation(s)
- Cheng-I Jonathan Ma
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Medical Sciences Building, Toronto, ON, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Medical Sciences Building, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Toronto, ON, Canada
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6
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The RAB3-RIM Pathway Is Essential for the Release of Neuromodulators. Neuron 2019; 104:1065-1080.e12. [PMID: 31679900 DOI: 10.1016/j.neuron.2019.09.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 08/01/2019] [Accepted: 09/10/2019] [Indexed: 12/21/2022]
Abstract
Secretion principles are conserved from yeast to humans, and many yeast orthologs have established roles in synaptic vesicle exocytosis in the mammalian brain. Surprisingly, SEC4 orthologs and their effectors, the exocyst, are dispensable for synaptic vesicle exocytosis. Here, we identify the SEC4 ortholog RAB3 and its neuronal effector, RIM1, as essential molecules for neuropeptide and neurotrophin release from dense-core vesicles (DCVs) in mammalian neurons. Inactivation of all four RAB3 genes nearly ablated DCV exocytosis, and re-expression of RAB3A restored this deficit. In RIM1/2-deficient neurons, DCV exocytosis was undetectable. Full-length RIM1, but not mutants that lack RAB3 or MUNC13 binding, restored release. Strikingly, a short N-terminal RIM1 fragment only harboring RAB3- and MUNC13-interacting domains was sufficient to support DCV exocytosis. We propose that RIM and MUNC13 emerged as mammalian alternatives to the yeast exocyst complex as essential RAB3/SEC4 effectors and organizers of DCV fusion sites by recruiting DCVs via RAB3.
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7
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Liu S, Majeed W, Grigaitis P, Betts MJ, Climer LK, Starkuviene V, Storrie B. Epistatic Analysis of the Contribution of Rabs and Kifs to CATCHR Family Dependent Golgi Organization. Front Cell Dev Biol 2019; 7:126. [PMID: 31428608 PMCID: PMC6687757 DOI: 10.3389/fcell.2019.00126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 06/26/2019] [Indexed: 01/05/2023] Open
Abstract
Multisubunit members of the CATCHR family: COG and NRZ complexes, mediate intra-Golgi and Golgi to ER vesicle tethering, respectively. We systematically addressed the genetic and functional interrelationships between Rabs, Kifs, and the retrograde CATCHR family proteins: COG3 and ZW10, which are necessary to maintain the organization of the Golgi complex. We scored the ability of siRNAs targeting 19 Golgi-associated Rab proteins and all 44 human Kifs, microtubule-dependent motor proteins, to suppress CATCHR-dependent Golgi fragmentation in an epistatic fluorescent microscopy-based assay. We found that co-depletion of Rab6A, Rab6A’, Rab27A, Rab39A and two minus-end Kifs, namely KIFC3 and KIF25, suppressed both COG3- and ZW10-depletion-induced Golgi fragmentation. ZW10-dependent Golgi fragmentation was suppressed selectively by a separate set of Rabs: Rab11A, Rab33B and the little characterized Rab29. 10 Kifs were identified as hits in ZW10-depletion-induced Golgi fragmentation, and, in contrast to the double suppressive Kifs, these were predominantly plus-end motors. No Rabs or Kifs selectively suppressed COG3-depletion-induced Golgi fragmentation. Protein-protein interaction network analysis indicated putative direct and indirect links between suppressive Rabs and tether function. Validation of the suppressive hits by EM confirmed a restored organization of the Golgi cisternal stack. Based on these outcomes, we propose a three-way competitive model of Golgi organization in which Rabs, Kifs and tethers modulate sequentially the balance between Golgi-derived vesicle formation, consumption, and off-Golgi transport.
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Affiliation(s)
- Shijie Liu
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Waqar Majeed
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Pranas Grigaitis
- Centre for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University, Heidelberg, Germany
| | - Matthew J Betts
- Centre for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University, Heidelberg, Germany
| | - Leslie K Climer
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Vytaute Starkuviene
- Centre for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University, Heidelberg, Germany.,Institute of Pharmacology and Molecular Biotechnology (IPMB), Heidelberg University, Heidelberg, Germany.,Institute of Biosciences, Vilnius University Life Sciences Centre, Vilnius, Lithuania
| | - Brian Storrie
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
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8
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Quevedo MF, Bustos MA, Masone D, Roggero CM, Bustos DM, Tomes CN. Grab recruitment by Rab27A-Rabphilin3a triggers Rab3A activation in human sperm exocytosis. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2019; 1866:612-622. [PMID: 30599141 DOI: 10.1016/j.bbamcr.2018.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 11/30/2018] [Accepted: 12/09/2018] [Indexed: 12/12/2022]
Abstract
Sperm must undergo the regulated exocytosis of its dense core granule (the acrosome reaction, AR) to fertilize the egg. We have previously described that Rabs3 and 27 are organized in a RabGEF cascade within the signaling pathway elicited by exocytosis stimuli in human sperm. Here, we report the identity and the role of two molecules that link these secretory Rabs in the RabGEF cascade: Rabphilin3a and GRAB. Like Rab3 and Rab27, GRAB and Rabphilin3a are present, localize to the acrosomal region and are required for calcium-triggered exocytosis in human sperm. Sequestration of either protein with specific antibodies introduced into streptolysin O-permeabilized sperm impairs the activation of Rab3 in the acrosomal region elicited by calcium, but not that of Rab27. Biochemical and functional assays indicate that Rabphilin3a behaves as a Rab27 effector during the AR and that GRAB exhibits GEF activity toward Rab3A. Recombinant, active Rab27A pulls down Rabphilin3a and GRAB from human sperm extracts. Conversely, immobilized Rabphilin3a recruits Rab27 and GRAB; the latter promotes Rab3A activation. The enzymatic activity of GRAB toward Rab3A was also suggested by in silico and in vitro assays with purified proteins. In summary, we describe here a signaling module where Rab27A-GTP interacts with Rabphilin3a, which in turn recruits a guanine nucleotide-exchange activity toward Rab3A. This is the first description of the interaction of Rabphilin3a with a GEF. Because the machinery that drives exocytosis is highly conserved, it is tempting to hypothesize that the RabGEF cascade unveiled here might be part of the molecular mechanisms that drive exocytosis in other secretory systems.
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Affiliation(s)
- María Florencia Quevedo
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Matías Alberto Bustos
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Diego Masone
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Facultad de Ingeniería, Universidad Nacional de Cuyo, Argentina
| | | | - Diego Martín Bustos
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Argentina
| | - Claudia Nora Tomes
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Argentina; Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Argentina.
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9
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Membrane trafficking in osteoclasts and implications for osteoporosis. Biochem Soc Trans 2019; 47:639-650. [PMID: 30837319 PMCID: PMC6490703 DOI: 10.1042/bst20180445] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 02/03/2019] [Accepted: 02/05/2019] [Indexed: 12/20/2022]
Abstract
Osteoclasts are large multinucleated cells exquisitely adapted to resorb bone matrix. Like other eukaryotes, osteoclasts possess an elaborate ensemble of intracellular organelles through which solutes, proteins and other macromolecules are trafficked to their target destinations via membrane-bound intermediaries. During bone resorption, membrane trafficking must be tightly regulated to sustain the structural and functional polarity of the osteoclasts’ membrane domains. Of these, the ruffled border (RB) is most characteristic, functioning as the osteoclasts' secretory apparatus. This highly convoluted organelle is classically considered to be formed by the targeted fusion of acidic vesicles with the bone-facing plasma membrane. Emerging findings disclose new evidence that the RB is far more complex than previously envisaged, possessing discrete subdomains that are serviced by several intersecting endocytic, secretory, transcytotic and autophagic pathways. Bone-resorbing osteoclasts therefore serve as a unique model system for studying polarized membrane trafficking. Recent advances in high-resolution microscopy together with the convergence of genetic and cell biological studies in humans and in mice have helped illuminate the major membrane trafficking pathways in osteoclasts and unmask the core molecular machinery that governs these distinct vesicle transport routes. Among these, small Rab GTPases, their binding partners and members of the endocytic sorting nexin family have emerged as critical regulators. This mini review summarizes our current understanding of membrane trafficking in osteoclasts, the key molecular participants, and discusses how these transport machinery may be exploited for the development of new therapies for metabolic disorders of bone-like osteoporosis.
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10
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Robinson CL, Evans RD, Sivarasa K, Ramalho JS, Briggs DA, Hume AN. The adaptor protein melanophilin regulates dynamic myosin-Va:cargo interaction and dendrite development in melanocytes. Mol Biol Cell 2019; 30:742-752. [PMID: 30699046 PMCID: PMC6589771 DOI: 10.1091/mbc.e18-04-0237] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The regulation of organelle transport by the cytoskeleton is fundamental for eukaryotic survival. Cytoskeleton motors are typically modular proteins with conserved motor and diverse cargo-binding domains. Motor:cargo interactions are often indirect and mediated by adaptor proteins, for example, Rab GTPases. Rab27a, via effector melanophilin (Mlph), recruits myosin-Va (MyoVa) to melanosomes and thereby disperses them into melanocyte dendrites. To better understand how adaptors regulate motor:cargo interaction, we used single melanosome fluorescence recovery after photobleaching (smFRAP) to characterize the association kinetics among MyoVa, its adaptors, and melanosomes. We found that MyoVa and Mlph rapidly recovered after smFRAP, whereas Rab27a did not, indicating that MyoVa and Mlph dynamically associate with melanosomes and Rab27a does not. This suggests that dynamic Rab27a:effector interaction rather than Rab27a melanosome:cytosol cycling regulates MyoVa:melanosome association. Accordingly, a Mlph-Rab27a fusion protein reduced MyoVa smFRAP, indicating that it stabilized melanosomal MyoVa. Finally, we tested the functional importance of dynamic MyoVa:melanosome interaction. We found that whereas a MyoVa-Rab27a fusion protein dispersed melanosomes in MyoVa-deficient cells, dendrites were significantly less elongated than in wild-type cells. Given that dendrites are the prime sites of melanosome transfer from melanocytes to keratinocytes, we suggest that dynamic MyoVa:melanosome interaction is important for pigmentation in vivo.
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Affiliation(s)
| | - Richard D Evans
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Kajana Sivarasa
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Jose S Ramalho
- CEDOC Faculdade de Ciencias Medicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Deborah A Briggs
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Alistair N Hume
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
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11
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Close WL, Glassbrook JE, Gurczynski SJ, Pellett PE. Infection-Induced Changes Within the Endocytic Recycling Compartment Suggest a Roadmap of Human Cytomegalovirus Egress. Front Microbiol 2018; 9:1888. [PMID: 30186245 PMCID: PMC6113367 DOI: 10.3389/fmicb.2018.01888] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 07/27/2018] [Indexed: 12/22/2022] Open
Abstract
Human cytomegalovirus (HCMV) is an important pathogen in developing fetuses, neonates, and individuals with compromised immune systems. Gaps in our understanding of the mechanisms required for virion assembly stand in the way of development of antivirals targeting late stages of viral replication. During infection, HCMV causes a dramatic reorganization of the host endosecretory system, leading to the formation of the cytoplasmic virion assembly complex (cVAC), the site of virion assembly. As part of cVAC biogenesis, the composition and behavior of endosecretory organelles change. To gain more comprehensive understanding of the impact HCMV infection has on components of the cellular endocytic recycling compartment (ERC), we used previously published transcriptional and proteomic datasets to predict changes in the directionality of ERC trafficking. We identified infection-associated changes in gene expression that suggest shifts in the balance between endocytic and exocytic recycling pathways, leading to formation of a secretory trap within the cVAC. Conversely, there was a corresponding shift favoring outbound secretory vesicle trafficking, indicating a potential role in virion egress. These observations are consistent with previous studies describing sequestration of signaling molecules, such as IL-6, and the synaptic vesicle-like properties of mature HCMV virions. Our analysis enabled development of a refined model incorporating old and new information related to the behavior of the ERC during HCMV replication. While limited by the paucity of integrated systems-level data, the model provides an informed basis for development of experimentally testable hypotheses related to mechanisms involved in HCMV virion maturation and egress. Information from such experiments will provide a robust roadmap for rational development of novel antivirals for HCMV and related viruses.
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Affiliation(s)
- William L. Close
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
| | - James E. Glassbrook
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
| | - Stephen J. Gurczynski
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Philip E. Pellett
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
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12
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Gandasi NR, Yin P, Omar-Hmeadi M, Ottosson Laakso E, Vikman P, Barg S. Glucose-Dependent Granule Docking Limits Insulin Secretion and Is Decreased in Human Type 2 Diabetes. Cell Metab 2018; 27:470-478.e4. [PMID: 29414688 DOI: 10.1016/j.cmet.2017.12.017] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/26/2017] [Accepted: 12/23/2017] [Indexed: 01/19/2023]
Abstract
Glucose-stimulated insulin secretion is biphasic, with a rapid first phase and a slowly developing sustained second phase; both are disturbed in type 2 diabetes (T2D). Biphasic secretion results from vastly different release probabilities of individual insulin granules, but the morphological and molecular basis for this is unclear. Here, we show that human insulin secretion and exocytosis critically depend on the availability of membrane-docked granules and that T2D is associated with a strong reduction in granule docking. Glucose accelerated granule docking, and this effect was absent in T2D. Newly docked granules only slowly acquired release competence; this was regulated by major signaling pathways, but not glucose. Gene expression analysis indicated that key proteins involved in granule docking are downregulated in T2D, and overexpression of these proteins increased granule docking. The findings establish granule docking as an important glucose-dependent step in human insulin secretion that is dysregulated in T2D.
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Affiliation(s)
- Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Peng Yin
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Muhmmad Omar-Hmeadi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Emilia Ottosson Laakso
- Diabetes and Endocrinology Unit, Department of Clinical Sciences, Lund University Diabetes Centre, 20502 Malmö, Sweden
| | - Petter Vikman
- Diabetes and Endocrinology Unit, Department of Clinical Sciences, Lund University Diabetes Centre, 20502 Malmö, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden.
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13
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Close WL, Anderson AN, Pellett PE. Betaherpesvirus Virion Assembly and Egress. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1045:167-207. [PMID: 29896668 DOI: 10.1007/978-981-10-7230-7_9] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Virions are the vehicle for cell-to-cell and host-to-host transmission of viruses. Virions need to be assembled reliably and efficiently, be released from infected cells, survive in the extracellular environment during transmission, recognize and then trigger entry of appropriate target cells, and disassemble in an orderly manner during initiation of a new infection. The betaherpesvirus subfamily includes four human herpesviruses (human cytomegalovirus and human herpesviruses 6A, 6B, and 7), as well as viruses that are the basis of important animal models of infection and immunity. Similar to other herpesviruses, betaherpesvirus virions consist of four main parts (in order from the inside): the genome, capsid, tegument, and envelope. Betaherpesvirus genomes are dsDNA and range in length from ~145 to 240 kb. Virion capsids (or nucleocapsids) are geometrically well-defined vessels that contain one copy of the dsDNA viral genome. The tegument is a collection of several thousand protein and RNA molecules packed into the space between the envelope and the capsid for delivery and immediate activity upon cellular entry at the initiation of an infection. Betaherpesvirus envelopes consist of lipid bilayers studded with virus-encoded glycoproteins; they protect the virion during transmission and mediate virion entry during initiation of new infections. Here, we summarize the mechanisms of betaherpesvirus virion assembly, including how infection modifies, reprograms, hijacks, and otherwise manipulates cellular processes and pathways to produce virion components, assemble the parts into infectious virions, and then transport the nascent virions to the extracellular environment for transmission.
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Affiliation(s)
- William L Close
- Department of Microbiology & Immunology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Ashley N Anderson
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Philip E Pellett
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA.
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14
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Neutrophil programming dynamics and its disease relevance. SCIENCE CHINA-LIFE SCIENCES 2017; 60:1168-1177. [PMID: 28971361 DOI: 10.1007/s11427-017-9145-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 07/21/2017] [Indexed: 12/27/2022]
Abstract
Neutrophils are traditionally considered as first responders to infection and provide antimicrobial host defense. However, recent advances indicate that neutrophils are also critically involved in the modulation of host immune environments by dynamically adopting distinct functional states. Functionally diverse neutrophil subsets are increasingly recognized as critical components mediating host pathophysiology. Despite its emerging significance, molecular mechanisms as well as functional relevance of dynamically programmed neutrophils remain to be better defined. The increasing complexity of neutrophil functions may require integrative studies that address programming dynamics of neutrophils and their pathophysiological relevance. This review aims to provide an update on the emerging topics of neutrophil programming dynamics as well as their functional relevance in diseases.
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15
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Close WL, Bhandari A, Hojeij M, Pellett PE. Generation of a novel human cytomegalovirus bacterial artificial chromosome tailored for transduction of exogenous sequences. Virus Res 2017; 242:66-78. [DOI: 10.1016/j.virusres.2017.09.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 09/11/2017] [Accepted: 09/11/2017] [Indexed: 11/25/2022]
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16
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Meng Z, Edman MC, Hsueh PY, Chen CY, Klinngam W, Tolmachova T, Okamoto CT, Hamm-Alvarez SF. Imbalanced Rab3D versus Rab27 increases cathepsin S secretion from lacrimal acini in a mouse model of Sjögren's Syndrome. Am J Physiol Cell Physiol 2016; 310:C942-54. [PMID: 27076615 DOI: 10.1152/ajpcell.00275.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 04/06/2016] [Indexed: 02/04/2023]
Abstract
The mechanism responsible for the altered spectrum of tear proteins secreted by lacrimal gland acinar cells (LGAC) in patients with Sjögren's Syndrome (SS) remains unknown. We have previously identified increased cathepsin S (CTSS) activity as a unique characteristic of tears of patients with SS. Here, we investigated the role of Rab3D, Rab27a, and Rab27b proteins in the enhanced release of CTSS from LGAC. Similar to patients with SS and to the male nonobese diabetic (NOD) mouse model of SS, CTSS activity was elevated in tears of mice lacking Rab3D. Findings of lower gene expression and altered localization of Rab3D in NOD LGAC reinforce a role for Rab3D in suppressing excess CTSS release under physiological conditions. However, CTSS activity was significantly reduced in tears of mice lacking Rab27 isoforms. The reliance of CTSS secretion on Rab27 activity was supported by in vitro findings that newly synthesized CTSS was detected in and secreted from Rab27-enriched secretory vesicles and that expression of dominant negative Rab27b reduced carbachol-stimulated secretion of CTSS in cultured LGAC. High-resolution 3D-structured illumination microscopy revealed microdomains of Rab3D and Rab27 isoforms on the same secretory vesicles but present in different proportions on different vesicles, suggesting that changes in their relative association with secretory vesicles may tailor the vesicle contents. We propose that a loss of Rab3D from secretory vesicles, leading to disproportionate Rab27-to-Rab3D activity, may contribute to the enhanced release of CTSS in tears of patients with SS.
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Affiliation(s)
- Zhen Meng
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Maria C Edman
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Pang-Yu Hsueh
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Chiao-Yu Chen
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Wannita Klinngam
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | | | - Curtis T Okamoto
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Sarah F Hamm-Alvarez
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California; Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California;
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17
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Handley MT, Carpanini SM, Mali GR, Sidjanin DJ, Aligianis IA, Jackson IJ, FitzPatrick DR. Warburg Micro syndrome is caused by RAB18 deficiency or dysregulation. Open Biol 2016; 5:150047. [PMID: 26063829 PMCID: PMC4632505 DOI: 10.1098/rsob.150047] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
RAB18, RAB3GAP1, RAB3GAP2 and TBC1D20 are each mutated in Warburg Micro syndrome, a rare autosomal recessive multisystem disorder. RAB3GAP1 and RAB3GAP2 form a binary ‘RAB3GAP’ complex that functions as a guanine-nucleotide exchange factor (GEF) for RAB18, whereas TBC1D20 shows modest RAB18 GTPase-activating (GAP) activity in vitro. Here, we show that in the absence of functional RAB3GAP or TBC1D20, the level, localization and dynamics of cellular RAB18 is altered. In cell lines where TBC1D20 is absent from the endoplasmic reticulum (ER), RAB18 becomes more stably ER-associated and less cytosolic than in control cells. These data suggest that RAB18 is a physiological substrate of TBC1D20 and contribute to a model in which a Rab-GAP can be essential for the activity of a target Rab. Together with previous reports, this indicates that Warburg Micro syndrome can be caused directly by loss of RAB18, or indirectly through loss of RAB18 regulators RAB3GAP or TBC1D20.
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Affiliation(s)
- Mark T Handley
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Sarah M Carpanini
- Division of Neurobiology, The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
| | - Girish R Mali
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Duska J Sidjanin
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Irene A Aligianis
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Ian J Jackson
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - David R FitzPatrick
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
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18
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Binotti B, Jahn R, Chua JJE. Functions of Rab Proteins at Presynaptic Sites. Cells 2016; 5:E7. [PMID: 26861397 PMCID: PMC4810092 DOI: 10.3390/cells5010007] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 02/03/2016] [Indexed: 01/24/2023] Open
Abstract
Presynaptic neurotransmitter release is dominated by the synaptic vesicle (SV) cycle and entails the biogenesis, fusion, recycling, reformation or turnover of synaptic vesicles-a process involving bulk movement of membrane and proteins. As key mediators of membrane trafficking, small GTPases from the Rab family of proteins play critical roles in this process by acting as molecular switches that dynamically interact with and regulate the functions of different sets of macromolecular complexes involved in each stage of the cycle. Importantly, mutations affecting Rabs, and their regulators or effectors have now been identified that are implicated in severe neurological and neurodevelopmental disorders. Here, we summarize the roles and functions of presynaptic Rabs and discuss their involvement in the regulation of presynaptic function.
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Affiliation(s)
- Beyenech Binotti
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - John Jia En Chua
- Interactomics and Intracellular Trafficking laboratory, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456, Singapore.
- Neurobiology/Ageing Programme, National University of Singapore, Singapore 117456, Singapore.
- Research Group Protein trafficking in synaptic development and function, Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen 37077, Germany.
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19
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Wang HH, Cui Q, Zhang T, Wang ZB, Ouyang YC, Shen W, Ma JY, Schatten H, Sun QY. Rab3A, Rab27A, and Rab35 regulate different events during mouse oocyte meiotic maturation and activation. Histochem Cell Biol 2016; 145:647-57. [PMID: 26791531 DOI: 10.1007/s00418-015-1404-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/31/2015] [Indexed: 01/22/2023]
Abstract
Rab family members play important roles in membrane trafficking, cell growth, and differentiation. Almost all components of the cell endomembrane system, the nucleus, and the plasma membrane are closely related to RAB proteins. In this study, we investigated the distribution and functions of three members of the Rab family, Rab3A, Rab27A, and Rab35, in mouse oocyte meiotic maturation and activation. The three Rab family members showed different localization patterns in oocytes. Microinjection of siRNA, antibody injection, or inhibitor treatment showed that (1) Rab3A regulates peripheral spindle and cortical granule (CG) migration, polarity establishment, and asymmetric division; (2) Rab27A regulates CG exocytosis following MII-stage oocyte activation; and (3) Rab35 plays an important role in spindle organization and morphology maintenance, and thus meiotic nuclear maturation. These results show that Rab proteins play important roles in mouse oocyte meiotic maturation and activation and that different members exert different distinct functions.
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Affiliation(s)
- H H Wang
- College of Life Sciences, Qingdao Agricultural University, Qingdao, 266109, China.,State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.,Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China
| | - Q Cui
- Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China
| | - T Zhang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.,Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China
| | - Z B Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Y C Ouyang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - W Shen
- Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China
| | - J Y Ma
- Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China
| | - H Schatten
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, 65211, USA
| | - Q Y Sun
- College of Life Sciences, Qingdao Agricultural University, Qingdao, 266109, China. .,State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China. .,Institute of Reproductive Sciences, Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, 266109, China.
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20
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Jiang S, Shen D, Jia WJ, Han X, Shen N, Tao W, Gao X, Xue B, Li CJ. GGPPS-mediated Rab27A geranylgeranylation regulates β cell dysfunction during type 2 diabetes development by affecting insulin granule docked pool formation. J Pathol 2015; 238:109-19. [PMID: 26434932 DOI: 10.1002/path.4652] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/19/2015] [Accepted: 09/28/2015] [Indexed: 11/09/2022]
Abstract
Loss of first-phase insulin secretion associated with β cell dysfunction is an independent predictor of type 2 diabetes mellitus (T2DM) onset. Here we found that a critical enzyme involved in protein prenylation, geranylgeranyl pyrophosphate synthase (GGPPS), is required to maintain first-phase insulin secretion. GGPPS shows a biphasic expression pattern in islets of db/db mice during the progression of T2DM: GGPPS is increased during the insulin compensatory period, followed by a decrease during β cell dysfunction. Ggpps deletion in β cells results in typical T2DM β cell dysfunction, with blunted glucose-stimulated insulin secretion and consequent insulin secretion insufficiency. However, the number and size of islets and insulin biosynthesis are unaltered. Transmission electron microscopy shows a reduced number of insulin granules adjacent to the cellular membrane, suggesting a defect in docked granule pool formation, while the reserve pool is unaffected. Ggpps ablation depletes GGPP and impairs Rab27A geranylgeranylation, which is responsible for the docked pool deficiency in Ggpps-null mice. Moreover, GGPPS re-expression or GGPP administration restore glucose-stimulated insulin secretion in Ggpps-null islets. These results suggest that GGPPS-controlled protein geranylgeranylation, which regulates formation of the insulin granule docked pool, is critical for β cell function and insulin release during the development of T2DM.
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Affiliation(s)
- Shan Jiang
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Di Shen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Wen-Jun Jia
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Xiao Han
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, People's Republic of China
| | - Ning Shen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Weiwei Tao
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Xiang Gao
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Bin Xue
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Chao-Jun Li
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
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21
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Bustos MA, Roggero CM, De la Iglesia PX, Mayorga LS, Tomes CN. GTP-bound Rab3A exhibits consecutive positive and negative roles during human sperm dense-core granule exocytosis. J Mol Cell Biol 2015; 6:286-98. [PMID: 25053757 DOI: 10.1093/jmcb/mju021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Exocytosis of mammalian sperm dense-core secretory granule relies on the same fusion molecules as all other secretory cells; one such molecule is the small GTPase Rab3A. Here, we report an in-depth biochemical characterization of the role of Rab3A in secretion by scrutinizing the exocytotic response of streptolysin O-permeabilized human sperm to the acute application of a number of Rab3A-containing constructs and correlating the findings with those gathered with the endogenous protein. Full length, geranylgeranylated, and active Rab3A elicited human sperm exocytosis per se. With Rab3A/Rab22A chimeric proteins, we demonstrated that the carboxy-terminal domain of the Rab3A molecule was necessary and sufficient to promote exocytosis, whereas its amino-terminus prevented calcium-triggered secretion. Interestingly, full length Rab3A halted secretion when added after the docking of the acrosome to the plasma membrane. This effect depended on the inability of Rab3A to hydrolyze GTP. We combined modified immunofluorescence and acrosomal staining protocols to detect membrane fusion and the activation status of endogenous Rab3 simultaneously in individual cells, and found that GTP hydrolysis on endogenous Rab3 was mandatory for fusion pores to open. Our findings contribute to establishing that Rab3 modulates regulated exocytosis differently depending on the nucleotide bound and the exocytosis stage under study.
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Affiliation(s)
- Matías A Bustos
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Carlos M Roggero
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina Present address: Department of Biophysics, UT Southwestern Medical Center, Dallas, TX, USA
| | - Paola X De la Iglesia
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina Present address: Servicio de Patología, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina
| | - Luis S Mayorga
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Claudia N Tomes
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
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22
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Gan KJ, Morihara T, Silverman MA. Atlas stumbled: Kinesin light chain-1 variant E triggers a vicious cycle of axonal transport disruption and amyloid-β generation in Alzheimer's disease. Bioessays 2014; 37:131-41. [DOI: 10.1002/bies.201400131] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Kathlyn J. Gan
- Department of Molecular Biology and Biochemistry; Simon Fraser University; Burnaby BC Canada
| | - Takashi Morihara
- Department of Psychiatry; Graduate School of Medicine; Osaka University; Osaka Japan
| | - Michael A. Silverman
- Department of Molecular Biology and Biochemistry; Simon Fraser University; Burnaby BC Canada
- Department of Biological Sciences; Simon Fraser University; Burnaby BC Canada
- Brain Research Centre; University of British Columbia; Vancouver BC Canada
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23
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Pavlos NJ, Jahn R. Distinct yet overlapping roles of Rab GTPases on synaptic vesicles. Small GTPases 2014; 2:77-81. [PMID: 21776405 DOI: 10.4161/sgtp.2.2.15201] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 02/17/2011] [Indexed: 11/19/2022] Open
Abstract
Exo-endocytotic cycling of synaptic vesicles (SVs) is one of the most intensely studied membrane trafficking pathways. It is governed by sets of conserved proteins including Rab GTPases. Long considered to define the identity and composition of a subcellular organelle, it has become increasingly evident that multiple Rabs co-exist on intracellular compartments, each contributing to its membrane organization and specialised function. Indeed, we have recently demonstrated that at least 11 distinct Rab proteins co-exist on highly purified SVs. These include Rabs involved in exocytosis (Rab3a/b/c and Rab27b) and intermediates of SV recycling such as early endosomes (Rab4, Rab5, Rab10, Rab11b and Rab14). Interestingly, we found that while two of these proteins, namely Rab3a and Rab27b, exhibited differential cycling dynamics on SV membranes; they played complementary roles during Ca(2+)-triggered neurotransmitter release. The implications of these findings in the SV trafficking cycle are discussed.
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Affiliation(s)
- Nathan J Pavlos
- Department of Neurobiology; Max-Planck Institute for Biophysical Chemistry; Göttingen, Germany
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24
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Cazares VA, Subramani A, Saldate JJ, Hoerauf W, Stuenkel EL. Distinct actions of Rab3 and Rab27 GTPases on late stages of exocytosis of insulin. Traffic 2014; 15:997-1015. [PMID: 24909540 DOI: 10.1111/tra.12182] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/04/2014] [Accepted: 06/04/2014] [Indexed: 12/16/2022]
Abstract
Rab GTPases associated with insulin-containing secretory granules (SGs) are key in targeting, docking and assembly of molecular complexes governing pancreatic β-cell exocytosis. Four Rab3 isoforms along with Rab27A are associated with insulin granules, yet elucidation of the distinct roles of these Rab families on exocytosis remains unclear. To define specific actions of these Rab families we employ Rab3GAP and/or EPI64A GTPase-activating protein overexpression in β-cells from wild-type or Ashen mice to selectively transit the entire Rab3 family or Rab27A to a GDP-bound state. Ashen mice carry a spontaneous mutation that eliminates Rab27A expression. Using membrane capacitance measurements we find that GTP/GDP nucleotide cycling of Rab27A is essential for generation of the functionally defined immediately releasable pool (IRP) and central to regulating the size of the readily releasable pool (RRP). By comparison, nucleotide cycling of Rab3 GTPases, but not of Rab27A, is essential for a kinetically rapid filling of the RRP with SGs. Aside from these distinct functions, Rab3 and Rab27A GTPases demonstrate considerable functional overlap in building the readily releasable granule pool. Hence, while Rab3 and Rab27A cooperate to generate release-ready SGs in β-cells, they also direct unique kinetic and functional properties of the exocytotic pathway.
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Affiliation(s)
- Victor A Cazares
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, 48109, USA
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25
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Gandasi NR, Barg S. Contact-induced clustering of syntaxin and munc18 docks secretory granules at the exocytosis site. Nat Commun 2014; 5:3914. [PMID: 24835618 DOI: 10.1038/ncomms4914] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/17/2014] [Indexed: 02/06/2023] Open
Abstract
Docking of secretory vesicles at the plasma membrane is a poorly understood prerequisite for exocytosis. Current models propose raft-like clusters containing syntaxin as docking receptor, but direct evidence for this is lacking. Here we provide quantitative measurements of several exocytosis proteins (syntaxin, SNAP25, munc18, munc13 and rab3) at the insulin granule release site and show that docking coincides with rapid de novo formation of syntaxin1/munc18 clusters at the nascent docking site. Formation of such clusters prevents undocking and is not observed during failed docking attempts. Overexpression of syntaxins' N-terminal Habc-domain competitively interferes with both cluster formation and successful docking. SNAP25 and munc13 are recruited to the docking site more than a minute later, consistent with munc13's reported role in granule priming rather than docking. We conclude that secretory vesicles dock by inducing syntaxin1/munc18 clustering in the target membrane, and find no evidence for preformed docking receptors.
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Affiliation(s)
- Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
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van der Sluijs P, Zibouche M, van Kerkhof P. Late steps in secretory lysosome exocytosis in cytotoxic lymphocytes. Front Immunol 2013; 4:359. [PMID: 24302923 PMCID: PMC3831147 DOI: 10.3389/fimmu.2013.00359] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 10/22/2013] [Indexed: 12/16/2022] Open
Abstract
Natural Killer cells are a subset of cytotoxic lymphocytes that are important in host defense against infections and transformed cells. They exert this function through recognition of target cells by cell surface receptors, which triggers a signaling program that results in a re-orientation of the microtubule organizing center and secretory lysosomes toward the target cell. Upon movement of secretory lysosomes to the plasma membrane and subsequent fusion, toxic proteins are released by secretory lysosomes in the immunological synapse which then enter and kill the target cell. In this minireview we highlight recent progress in our knowledge of late steps in this specialized secretion pathway and address important open questions.
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Affiliation(s)
- Peter van der Sluijs
- Department of Cell Biology, University Medical Center Utrecht , Utrecht , Netherlands
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Khandelwal P, Prakasam HS, Clayton DR, Ruiz WG, Gallo LI, van Roekel D, Lukianov S, Peränen J, Goldenring JR, Apodaca G. A Rab11a-Rab8a-Myo5B network promotes stretch-regulated exocytosis in bladder umbrella cells. Mol Biol Cell 2013; 24:1007-19. [PMID: 23389633 PMCID: PMC3608489 DOI: 10.1091/mbc.e12-08-0568] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 01/29/2013] [Accepted: 01/30/2013] [Indexed: 12/03/2022] Open
Abstract
Multiple Rabs are associated with secretory granules/vesicles, but how these GTPases are coordinated to promote regulated exocytosis is not well understood. In bladder umbrella cells a subapical pool of discoidal/fusiform-shaped vesicles (DFVs) undergoes Rab11a-dependent regulated exocytosis in response to bladder filling. We show that Rab11a-associated vesicles are enmeshed in an apical cytokeratin meshwork and that Rab11a likely acts upstream of Rab8a to promote exocytosis. Surprisingly, expression of Rabin8, a previously described Rab11a effector and guanine nucleotide exchange factor for Rab8, stimulates stretch-induced exocytosis in a manner that is independent of its catalytic activity. Additional studies demonstrate that the unconventional motor protein myosin5B motor (Myo5B) works in association with the Rab8a-Rab11a module to promote exocytosis, possibly by ensuring transit of DFVs through a subapical, cortical actin cytoskeleton before fusion. Our results indicate that Rab11a, Rab8a, and Myo5B function as part of a network to promote stretch-induced exocytosis, and we predict that similarly organized Rab networks will be common to other regulated secretory pathways.
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Affiliation(s)
- Puneet Khandelwal
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | | | - Dennis R. Clayton
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | - Wily G. Ruiz
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | - Luciana I. Gallo
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | - Daniel van Roekel
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | - Stefan Lukianov
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
| | - Johan Peränen
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - James R. Goldenring
- Department of Surgery and Epithelial Biology Center, Vanderbilt University, Nashville, TN 37232
| | - Gerard Apodaca
- Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261
- Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261
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Singh RK, Mizuno K, Wasmeier C, Wavre-Shapton ST, Recchi C, Catz SD, Futter C, Tolmachova T, Hume AN, Seabra MC. Distinct and opposing roles for Rab27a/Mlph/MyoVa and Rab27b/Munc13-4 in mast cell secretion. FEBS J 2013; 280:892-903. [PMID: 23281710 DOI: 10.1111/febs.12081] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 10/31/2012] [Accepted: 11/26/2012] [Indexed: 11/29/2022]
Abstract
Mediator release from mast cells is a critical step in allergic and inflammatory disease. However, the processes regulating the latter stages of granule release are yet to be fully understood. Rab27 small GTPases regulate release of secretory lysosomes in a variety of cells, including mast cell granules. In the present study, using murine bone marrow-derived mast cells (BMMC) from Rab27-deficient mutant mice, we found that, in contrast to Rab27b, Rab27a primarily plays an inhibitory role in regulating degranulation. Immunofluorescence analysis revealed that resting Rab27a-deficient (ashen) BMMCs display abnormal cortical F-actin distribution. Actin disassembly prior to IgE cross-linking increased wild-type BMMC secretion to ashen levels, suggesting that changes in the integrity of cortical F-actin underlie the ashen phenotype. Comparison of the secretory impairment of Rab27b knockout and Rab27a/b double knockout BMMCs highlighted a secondary positive role for Rab27a in enhancing degranulation. Rab27 is known to interact with actin via its effectors melanophilin (Mlph) and myosin Va (MyoVa) in other cell types. To better understand the differing roles of Rab27 proteins, we analysed the secretory phenotype of BMMCs derived from mice lacking Rab27 effector proteins. These experiments revealed that the phenotype of BMMCs deficient in Mlph (leaden) and BMMCs deficient in MyoVa (dilute) resembles the hyper-secretion of ashen BMMCs, while Munc13-4-deficient (jinx) BMMCs phenocopy the Rab27b knockout and double Rab27a/b knockout secretory impairment. We conclude that Rab27a and Rab27b regulate distinct steps in the BMMC degranulation pathway, with Rab27a/Mlph/MyoVa regulating cortical actin stability upstream of Rab27a/b/Munc13-4-dependent granule exocytosis.
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Affiliation(s)
- Rajesh K Singh
- Molecular Medicine, National Heart and Lung Institute, Imperial College London, London, UK
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Liu Y, Zhou Y, Zhu K. Inhibition of glioma cell lysosome exocytosis inhibits glioma invasion. PLoS One 2012; 7:e45910. [PMID: 23029308 PMCID: PMC3461042 DOI: 10.1371/journal.pone.0045910] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 08/27/2012] [Indexed: 11/19/2022] Open
Abstract
Cancer cells invade by secreting enzymes that degrade the extracellular matrix and these are sequestered in lysosomal vesicles. In this study, the effects of the selective lysosome lysing drug GPN and the lysosome exocytosis inhibitor vacuolin-1 on lysosome exocytosis were studied to determine their effect on glioma cell migration and invasion. Both GPN and vacuolin-1 evidently inhibited migration and invasion in transwell experiments and scratch experiments. There are more lysosomes located on the cell membrane of glioma cells than of astrocytes. GPN decreased the lysosome number on the cell membrane. We found that rab27A was expressed in glioma cells, and colocalized with cathepsin D in lysosome. RNAi-Rab27A inhibited lysosome cathepsin D exocytosis and glioma cell invasion in an in vitro assay. Inhibition of cathepsin D inhibited glioma cell migration. The data suggest that the inhibition of lysosome exocytosis from glioma cells plays an important modulatory role in their migration and invasion.
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Affiliation(s)
- Yu Liu
- Department of Pathology, Department of Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Yijiang Zhou
- Department of Pathology, Department of Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Keqing Zhu
- Department of Pathology, Department of Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
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Becherer U, Medart MR, Schirra C, Krause E, Stevens D, Rettig J. Regulated exocytosis in chromaffin cells and cytotoxic T lymphocytes: How similar are they? Cell Calcium 2012; 52:303-12. [DOI: 10.1016/j.ceca.2012.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/27/2012] [Accepted: 04/09/2012] [Indexed: 10/28/2022]
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The interplay between the Rab27A effectors Slp4-a and MyRIP controls hormone-evoked Weibel-Palade body exocytosis. Blood 2012; 120:2757-67. [PMID: 22898601 DOI: 10.1182/blood-2012-05-429936] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Weibel-Palade body (WPB) exocytosis underlies hormone-evoked VWF secretion from endothelial cells (ECs). We identify new endogenous components of the WPB: Rab3B, Rab3D, and the Rab27A/Rab3 effector Slp4-a (granuphilin), and determine their role in WPB exocytosis. We show that Rab3B, Rab3D, and Rab27A contribute to Slp4-a localization to WPBs. siRNA knockdown of Slp4-a, MyRIP, Rab3B, Rab3D, Rab27A, or Rab3B/Rab27A, or overexpression of EGFP-Slp4-a or EGFP-MyRIP showed that Slp4-a is a positive and MyRIP a negative regulator of WPB exocytosis and that Rab27A alone mediates these effects. We found that ECs maintain a constant amount of cellular Rab27A irrespective of the WPB pool size and that Rab27A (and Rab3s) cycle between WPBs and a cytosolic pool. The dynamic redistribution of Rab proteins markedly decreased the Rab27A concentration on individual WPBs with increasing WPB number per cell. Despite this, the probability of WPB release was independent of WPB pool size showing that WPB exocytosis is not determined simply by the absolute amount of Rab27A and its effectors on WPBs. Instead, we propose that the probability of release is determined by the fractional occupancy of WPB-Rab27A by Slp4-a and MyRIP, with the balance favoring exocytosis.
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Rab27 and Rab3 sequentially regulate human sperm dense-core granule exocytosis. Proc Natl Acad Sci U S A 2012; 109:E2057-66. [PMID: 22753498 DOI: 10.1073/pnas.1121173109] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Two so-called "secretory Rabs," Rab3 and Rab27, regulate late steps during dense-core vesicle exocytosis in neuroendocrine cells. Sperm contain a single large dense-core granule that is released by regulated exocytosis (termed the acrosome reaction) during fertilization or on exposure to inducers in vitro. Sperm exocytosis uses the same fusion machinery as neurons and neuroendocrine cells, with an additional requirement for active Rab3. Here we show that Rab27 is also required for the acrosome reaction, as demonstrated by the inability of inducers to elicit exocytosis when streptolysin O-permeabilized human sperm were loaded with inhibitory anti-Rab27 antibodies or the Rab27-GTP binding domain of the effector Slac2-b. The levels of GTP-bound Rab27 increased on initiation of exocytosis, as did the proportion of GTP-bound Rab3A. We have developed a fluorescence microscopy-based method for detecting endogenous Rab3A-GTP and Rab27-GTP in the acrosomal region of human sperm. Challenge with an inducer increased the population of cells exhibiting GTP-bound Rabs in this subcellular domain. Interestingly, introducing recombinant Rab27A loaded with GTP-γ-S into sperm elicited a remarkable increase in the number of cells evincing GTP-bound Rab3A. In the converse condition, recombinant Rab3A did not modify the percentage of Rab27-GTP-containing cells. Furthermore, Rab27A-GTP recruited a Rab3 GDP/GTP exchange factor (GEF) activity. Our findings suggest that Rab27/Rab3A constitutes a Rab-GEF cascade in dense-core vesicle exocytosis.
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Rojo Pulido I, Nightingale TD, Darchen F, Seabra MC, Cutler DF, Gerke V. Myosin Va acts in concert with Rab27a and MyRIP to regulate acute von-Willebrand factor release from endothelial cells. Traffic 2011; 12:1371-82. [PMID: 21740491 DOI: 10.1111/j.1600-0854.2011.01248.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Von-Willebrand factor (vWF) is a highly multimerized hemostatic glycoprotein that is stored in endothelial Weibel-Palade bodies (WPB) and secreted upon cell stimulation to act in recruiting platelets to sites of vessel injury. Only fully matured multimeric vWF represents an efficient anchor for platelets, and endothelial cells have developed mechanisms to prevent release of immature vWF. Full maturation of vWF occurs within WPB following their translocation from a perinuclear site of emergence at the trans-Golgi network (TGN) to the cell periphery. The WPB-associated small GTPase Rab27a is involved in restricting immature WPB exocytosis and we searched for links between Rab27a and the actin cytoskeleton that could anchor WPB inside endothelial cells until they are fully matured. We here identify myosin Va as such link. Myosin Va forms a tripartite complex with Rab27a and its effector MyRIP and depletion of or dominant-negative interference with myosin Va leads to an increase in the ratio of perinuclear to more peripheral WPB. Concomitantly, myosin Va depletion results in an elevated secretion of less-oligomeric vWF from histamine-stimulated endothelial cells. These results indicate that a Rab27a/MyRIP/myosin Va complex is involved in linking WPB to the peripheral actin cytoskeleton of endothelial cells to allow full maturation and prevent premature secretion of vWF.
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Affiliation(s)
- Inés Rojo Pulido
- Institute of Medical Biochemistry, Centre for Molecular Biology of Inflammation, University of Münster, Münster, Germany
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Abstract
Advances in live-cell microscopy have revealed the extraordinarily dynamic nature of intracellular organelles. Moreover, movement appears to be critical in establishing and maintaining intracellular organization and organellar and cellular function. Motility is regulated by the activity of organelle-associated motor proteins, kinesins, dyneins and myosins, which move cargo along polar MT (microtubule) and actin tracks. However, in most instances, the motors that move specific organelles remain mysterious. Over recent years, pigment granules, or melanosomes, within pigment cells have provided an excellent model for understanding the molecular mechanisms by which motor proteins associate with and move intracellular organelles. In the present paper, we discuss recent discoveries that shed light on the mechanisms of melanosome transport and highlight future prospects for the use of pigment cells in unravelling general molecular mechanisms of intracellular transport.
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DJ-1 associates with synaptic membranes. Neurobiol Dis 2011; 43:651-62. [PMID: 21645620 DOI: 10.1016/j.nbd.2011.05.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Revised: 04/30/2011] [Accepted: 05/20/2011] [Indexed: 12/30/2022] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder caused by loss of dopaminergic neurons. Although many reports have suggested that genetic factors are implicated in the pathogenesis of PD, molecular mechanisms underlying selective dopaminergic neuronal degeneration remain unknown. DJ-1 is a causative gene for autosomal recessive form of PARK7-linked early-onset PD. A number of studies have demonstrated that exogenous DJ-1 localizes within mitochondria and the cytosol, and functions as a molecular chaperone, as a transcriptional regulator, and as a cell protective factor against oxidative stress. However, the precise subcellular localization and function of endogenous DJ-1 are not well known. The mechanisms by which mutations in DJ-1 contributes to neuronal degeneration also remain poorly understood. Here we show by immunocytochemistry that DJ-1 distributes to the cytosol and membranous structures in a punctate appearance in cultured cells and in primary neurons obtained from mouse brain. Interestingly, DJ-1 colocalizes with the Golgi apparatus proteins GM130 and the synaptic vesicle proteins such as synaptophysin and Rab3A. Förster resonance energy transfer analysis revealed that a small portion of DJ-1 interacts with synaptophysin in living cells. Although the wild-type DJ-1 protein directly associates with membranes without an intermediary protein, the pathogenic L166P mutation of DJ-1 exhibits less binding to synaptic vesicles. These results indicate that DJ-1 associates with membranous organelles including synaptic membranes to exhibit its normal function.
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Mizuno K, Ramalho JS, Izumi T. Exophilin8 transiently clusters insulin granules at the actin-rich cell cortex prior to exocytosis. Mol Biol Cell 2011; 22:1716-26. [PMID: 21441305 PMCID: PMC3093323 DOI: 10.1091/mbc.e10-05-0404] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 02/09/2011] [Accepted: 03/11/2011] [Indexed: 12/16/2022] Open
Abstract
Exophilin8/MyRIP/Slac2-c is an effector protein of the small GTPase Rab27a and is specifically localized on retinal melanosomes and secretory granules. We investigated the role of exophilin8 in insulin granule trafficking. Exogenous expression of exophilin8 in pancreatic β cells or their cell line, MIN6, polarized (exophilin8-positive) insulin granules at the cell corners, where both cortical actin and the microtubule plus-end-binding protein, EB1, were present. Mutation analyses indicated that the ability of exophilin8 to act as a linker between Rab27a and myosin Va is essential for its granule-clustering activity. Moreover, exophilin8 and exophilin8-associated insulin granules were markedly stable and immobile. Total internal reflection fluorescence microscopy indicated that exophilin8 restricts the motion of insulin granules at a region deeper than that where another Rab27a effector, granuphilin, accumulates docked granules directly attached to the plasma membrane. However, the exophilin8-induced immobility of insulin granules was eliminated upon secretagogue stimulation and did not inhibit evoked exocytosis. Furthermore, exophilin8 depletion prevents insulin granules from being transported close to the plasma membrane and inhibits their fusion. These findings indicate that exophilin8 transiently traps insulin granules into the cortical actin network close to the microtubule plus-ends and supplies them for release during the stimulation.
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Affiliation(s)
- Kouichi Mizuno
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371–8512, Japan
| | - José S. Ramalho
- CEDOC, Faculty of Medical Sciences, NOVA University, 1169–056 Lisbon, Portugal
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371–8512, Japan
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Keratinocyte secretion of cyclophilin B via the constitutive pathway is regulated through its cyclosporin-binding site. J Invest Dermatol 2011; 131:1085-94. [PMID: 21270823 PMCID: PMC3182837 DOI: 10.1038/jid.2010.415] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cyclophilin B (CypB) is an endoplasmic reticulum (ER)-resident member of the cyclophilin family of proteins that bind cyclosporin A (CsA). We report that as in other cell types, CypB trafficked from the ER and was secreted by keratinocytes into the media in response to CsA. Concentrations as low as 1 pM of CsA induced secretion of CypB. Using brefeldin A, we showed that CypB is secreted from keratinocytes via the constitutive secretory pathway. We defined that substitution of tryptophan residue 128 in the CsA-binding site of CypB with alanine resulted in dissociation of CypB(W128A)-green fluorescent protein (GFP) from the ER. Photobleaching studies revealed a significant reduction in the diffusible mobility of CypB(W128A)-GFP compared with CypB(WT)-GFP, consistent with redistribution of CypB(W128A)-GFP into secretory vesicles disconnected from the ER/Golgi network. Furthermore, CsA significantly decreased the mobility of CypB(WT)-GFP but not CypB(W128A)-GFP. These studies demonstrate that therapeutically relevant concentrations of CsA regulate secretion of CypB by keratinocytes, and that a key residue within the CsA-binding site of CypB controls retention of CypB within the ER and regulates entry into the secretory pathway. As keratinocytes express CypB receptors (CD147) and CypB exhibits chemotactic properties, these data have implications for the therapeutic effects of CsA in inflammatory skin disease.
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Quantitative analysis of synaptic vesicle Rabs uncovers distinct yet overlapping roles for Rab3a and Rab27b in Ca2+-triggered exocytosis. J Neurosci 2010; 30:13441-53. [PMID: 20926670 DOI: 10.1523/jneurosci.0907-10.2010] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Rab GTPases are molecular switches that orchestrate protein complexes before membrane fusion reactions. In synapses, Rab3 and Rab5 proteins have been implicated in the exo-endocytic cycling of synaptic vesicles (SVs), but an involvement of additional Rabs cannot be excluded. Here, combining high-resolution mass spectrometry and chemical labeling (iTRAQ) together with quantitative immunoblotting and fluorescence microscopy, we have determined the exocytotic (Rab3a, Rab3b, Rab3c, and Rab27b) and endocytic (Rab4b, Rab5a/b, Rab10, Rab11b, and Rab14) Rab machinery of SVs. Analysis of two closely related proteins, Rab3a and Rab27b, revealed colocalization in synaptic nerve terminals, where they reside on distinct but overlapping SV pools. Moreover, whereas Rab3a readily dissociates from SVs during Ca(2+)-triggered exocytosis, and is susceptible to membrane extraction by Rab-GDI, Rab27b persists on SV membranes upon stimulation and is resistant to GDI-coupled Rab retrieval. Finally, we demonstrate that selective modulation of the GTP/GDP switch mechanism of Rab27b impairs SV recycling, suggesting that Rab27b, probably in concert with Rab3s, is involved in SV exocytosis.
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Counotte DS, Li KW, Wortel J, Gouwenberg Y, Van Der Schors RC, Smit AB, Spijker S. Changes in molecular composition of rat medial prefrontal cortex synapses during adolescent development. Eur J Neurosci 2010; 32:1452-60. [PMID: 20950357 DOI: 10.1111/j.1460-9568.2010.07404.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Postnatal brain development continues throughout adolescence into young adulthood. In particular, synapse strengthening and elimination are prominent processes during adolescence. However, molecular data of this relatively late stage of synaptic development are sparse. In this study, we used iTRAQ (isobaric tag for relative and absolute quantification)-based proteomics and electron microscopy to investigate the molecular composition of a synaptic membrane fraction from adolescent postnatal day (P)34 and P44 and adult (P78) rat medial prefrontal cortex. Differential expression of proteins was most prominent between early adolescence and young adulthood (35%, P34-P78), with an over-representation of cell-membrane proteins during adolescent development (between P34 and P44), and synaptic vesicle proteins between late adolescence and young adulthood (P44-P78). Indicative of the critical period of development, we found that, between P34 and P44, a substantial number of proteins was differentially expressed (14%), much more than during the period after adolescence, i.e. between P44 and P78 (5%). A striking observation was the developmental non-stoichiometric regulation of distinct classes of proteins from the synaptic vesicle and the presynaptic release machinery. Electron microscopy demonstrated a small change in the number of docked vesicles between P34 and P44, but not in the total number of synaptic vesicles and in the size of the vesicle cluster. We conclude that the molecular composition of synapses, and more specifically the synaptic release machinery, of the medial prefrontal cortex changes drastically during adolescent development.
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Affiliation(s)
- Danielle S Counotte
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics & Cognitive Research (CNCR), Neuroscience Campus Amsterdam, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
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40
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Schonn JS, Van Weering JRT, Mohrmann R, Schlüter OM, Südhof TC, De Wit H, Verhage M, Sørensen JB. Rab3 Proteins Involved in Vesicle Biogenesis and Priming in Embryonic Mouse Chromaffin Cells. Traffic 2010; 11:1415-28. [DOI: 10.1111/j.1600-0854.2010.01107.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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41
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Handley MTW, Lian LY, Haynes LP, Burgoyne RD. Structural and functional deficits in a neuronal calcium sensor-1 mutant identified in a case of autistic spectrum disorder. PLoS One 2010; 5:e10534. [PMID: 20479890 PMCID: PMC2866544 DOI: 10.1371/journal.pone.0010534] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 04/15/2010] [Indexed: 11/18/2022] Open
Abstract
Neuronal calcium sensor-1 (NCS-1) is a Ca(2+) sensor protein that has been implicated in the regulation of various aspects of neuronal development and neurotransmission. It exerts its effects through interactions with a range of target proteins one of which is interleukin receptor accessory protein like-1 (IL1RAPL1) protein. Mutations in IL1RAPL1 have recently been associated with autism spectrum disorders and a missense mutation (R102Q) on NCS-1 has been found in one individual with autism. We have examined the effect of this mutation on the structure and function of NCS-1. From use of NMR spectroscopy, it appeared that the R102Q affected the structure of the protein particularly with an increase in the extent of conformational exchange in the C-terminus of the protein. Despite this change NCS-1(R102Q) did not show changes in its affinity for Ca(2+) or binding to IL1RAPL1 and its intracellular localisation was unaffected. Assessment of NCS-1 dynamics indicated that it could rapidly cycle between cytosolic and membrane pools and that the cycling onto the plasma membrane was specifically changed in NCS-1(R102Q) with the loss of a Ca(2+) -dependent component. From these data we speculate that impairment of the normal cycling of NCS-1 by the R102Q mutation could have subtle effects on neuronal signalling and physiology in the developing and adult brain.
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Affiliation(s)
- Mark T. W. Handley
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Lu-Yun Lian
- School of Biological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Lee P. Haynes
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Robert D. Burgoyne
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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Tsuboi T, Kitaguchi T, Karasawa S, Fukuda M, Miyawaki A. Age-dependent preferential dense-core vesicle exocytosis in neuroendocrine cells revealed by newly developed monomeric fluorescent timer protein. Mol Biol Cell 2010; 21:87-94. [PMID: 19889833 PMCID: PMC2801723 DOI: 10.1091/mbc.e09-08-0722] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 10/13/2009] [Accepted: 10/28/2009] [Indexed: 11/11/2022] Open
Abstract
Although it is evident that only a few secretory vesicles accumulating in neuroendocrine cells are qualified to fuse with the plasma membrane and release their contents to the extracellular space, the molecular mechanisms that regulate their exocytosis are poorly understood. For example, it has been controversial whether secretory vesicles are exocytosed randomly or preferentially according to their age. Using a newly developed protein-based fluorescent timer, monomeric Kusabira Green Orange (mK-GO), which changes color with a predictable time course, here we show that small GTPase Rab27A effectors regulate age-dependent exocytosis of secretory vesicles in PC12 cells. When the vesicles were labeled with mK-GO-tagged neuropeptide Y or tissue-type plasminogen activator, punctate structures with green or red fluorescence were observed. Application of high [K(+)] stimulation induced exocytosis of new (green) fluorescent secretory vesicles but not of old (red) vesicles. Overexpression or depletion of rabphilin and synaptotagmin-like protein4-a (Slp4-a), which regulate exocytosis positively and negatively, respectively, disturbed the age-dependent exocytosis of the secretory vesicles in different manners. Our results suggest that coordinate functions of the two effectors of Rab27A, rabphilin and Slp4-a, are required for regulated secretory pathway.
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Affiliation(s)
- Takashi Tsuboi
- *Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo 153-8902, Japan
- Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan
| | - Tetsuya Kitaguchi
- Life Function and Dynamics, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Wako, Saitama 351-0198, Japan
| | - Satoshi Karasawa
- Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan
- Amalgaam Co., Ltd., Itabashi, Tokyo 173-0004, Japan; and
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Atsushi Miyawaki
- Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan
- Life Function and Dynamics, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Wako, Saitama 351-0198, Japan
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APP anterograde transport requires Rab3A GTPase activity for assembly of the transport vesicle. J Neurosci 2009; 29:14534-44. [PMID: 19923287 DOI: 10.1523/jneurosci.1546-09.2009] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The amyloid precursor protein (APP) is anterogradely transported by conventional kinesin in a distinct transport vesicle, but both the biochemical composition of such a vesicle and the specific kinesin-1 motor responsible for transport are poorly defined. APP may be sequentially cleaved by beta- and gamma-secretases leading to accumulation of beta-amyloid (Abeta) peptides in brains of Alzheimer's disease patients, whereas cleavage of APP by alpha-secretases prevents Abeta generation. Here, we demonstrate by time-lapse analysis and immunoisolations that APP is a cargo of a vesicle containing the kinesin heavy chain isoform kinesin-1C, the small GTPase Rab3A, and a specific subset of presynaptic protein components. Moreover, we report that assembly of kinesin-1C and APP in this vesicle type requires Rab3A GTPase activity. Finally, we show cleavage of APP in transport vesicles by alpha-secretase activity, likely mediated by ADAM10. Together, these data indicate that maturation of APP transport vesicles, including recruitment of conventional kinesin, requires Rab3 GTPase activity.
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Abstract
There is now increasing evidence that LDs (lipid droplets) play a central role in the production of infectious HCV (hepatitis C virus) and participate in virus assembly. Two viral proteins, namely core, which forms the capsid, and NS5A (non-structural 5A protein), a component of complexes engaged in viral RNA synthesis, are detected at LD surfaces in infected cells. Interactions between the two proteins may be critical for anchoring RNA replication sites to droplets for initiating virus assembly. The requirements for targeting of core in particular has received considerable attention since the nature of its interaction with LDs could play a key role in determining the efficiency of virion production. As well as attaching to droplets, core is able to alter their intracellular distribution and direct them towards the microtubule organizing centre. Inhibitors that disrupt microtubules block this redistribution by core and there is a concomitant decrease in virus production. Therefore altered dynamics of LDs may contribute to HCV assembly and release. The purpose of targeting LDs by HCV may be linked to their contribution to the formation of VLDLs (very-low-density lipoproteins) in hepatocytes since virus circulating in infected patients is associated with lipoprotein. Thus HCV may utilize the role played by LDs in the formation of lipoprotein particles as part of its life cycle and access this pathway by direct interaction of viral components with these intracellular storage organelles.
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Raffaniello R, Fedorova D, Ip D, Rafiq S. Hsp90 Co-localizes with Rab-GDI-1 and regulates agonist-induced amylase release in AR42J cells. Cell Physiol Biochem 2009; 24:369-78. [PMID: 19910677 DOI: 10.1159/000257429] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2009] [Indexed: 11/19/2022] Open
Abstract
Rab proteins are small GTPases required for vesicle trafficking through the secretory and endocytic pathways. Rab GDP-dissociation inhibitor (rab-GDI) regulates Rab protein function and localization by maintaining Rab proteins in the GDP-bound conformation. Two isoforms of rab-GDI are present in most mammalian cells: GDI-1 and GDI-2. It has recently been demonstrated that a Heat shock protein 90 (Hsp90) chaperone complex regulates the interactions between Rab proteins and Rab-GDI-1. The AR42J cell line is derived from rat pancreatic exocrine tumor cells and develops an acinar-like phenotype when treated with dexamethasone (Dex). The aim of the present study was to examine the expression of rab-GDI isoforms and Hsp90 in AR42J cells in the presence or absence of Dex. Rab-GDI:Hsp90 interactions were also examined. Both rab-GDI isoforms were detected in AR42J cells by immunoblotting. In Dex-treated cells, quantitative immunoblotting revealed that rab-GDI-1 expression increased by 28%, although this change was not statistically significant. Rab-GDI-2 levels were unaltered by Dex treatment. Approximately 21% rab-GDI-1 was membrane associated, whereas rab-GDI-2 was exclusively cytosolic. Dex treatment did not affect the subcellular distribution of rab-GDI isoforms. Hsp90 was present in the cytosolic and membrane fractions of AR42J cells and co-immunoprecipitated with cytosolic rab-GDI-1. Moreover, density gradient centrifugation of AR42J cell membranes revealed that Hsp90 and rab-GDI-1 co-localize on low- and high-density membrane fractions, including amylase-containing secretory granules. The Hsp90 inhibitor, geldanamycin, inhibited CCK-8-induced amylase release from these cells in a dose-dependent manner. Our results indicate that as AR42J cells differentiate into acinar-like cells, rab-GDI isoform expression and localization is not significantly altered. Moreover, our findings suggest that Hsp90 regulates agonist-induced secretion in exocrine cells by interacting with rab-GDI-1.
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Edwards SL, Charlie NK, Richmond JE, Hegermann J, Eimer S, Miller KG. Impaired dense core vesicle maturation in Caenorhabditis elegans mutants lacking Rab2. ACTA ACUST UNITED AC 2009; 186:881-95. [PMID: 19797080 PMCID: PMC2753164 DOI: 10.1083/jcb.200902095] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Uncoordinated movement in Rab2 mutants is caused by impaired retention of cargo on dense core vesicles, not by defective synaptic vesicle release. (Also see the companion article by Sumakovic et al. in this issue.) Despite a key role for dense core vesicles (DCVs) in neuronal function, there are major gaps in our understanding of DCV biogenesis. A genetic screen for Caenorhabditis elegans mutants with behavioral defects consistent with impaired DCV function yielded five mutations in UNC-108 (Rab2). A genetic analysis showed that unc-108 mutations impair a DCV function unrelated to neuropeptide release that, together with neuropeptide release, fully accounts for the role of DCVs in locomotion. An electron microscopy analysis of DCVs in unc-108 mutants, coupled with quantitative imaging of DCV cargo proteins, revealed that Rab2 acts in cell somas during DCV maturation to prevent the loss of soluble and membrane cargo. In Rab2 null mutants, two thirds of these cargoes move to early endosomes via a PI(3)P-dependent trafficking pathway, whereas aggregated neuropeptides are unaffected. These results reveal how neurons solve a challenging trafficking problem using the most highly conserved animal Rab.
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Affiliation(s)
- Stacey L Edwards
- Genetic Models of Disease Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
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Branham MT, Bustos MA, De Blas GA, Rehmann H, Zarelli VEP, Treviño CL, Darszon A, Mayorga LS, Tomes CN. Epac activates the small G proteins Rap1 and Rab3A to achieve exocytosis. J Biol Chem 2009; 284:24825-39. [PMID: 19546222 DOI: 10.1074/jbc.m109.015362] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Exocytosis of the acrosome (the acrosome reaction) relies on cAMP production, assembly of a proteinaceous fusion machinery, calcium influx from the extracellular medium, and mobilization from inositol 1,4,5-trisphosphate-sensitive intracellular stores. Addition of cAMP to human sperm suspensions bypasses some of these requirements and elicits exocytosis in a protein kinase A- and extracellular calcium-independent manner. The relevant cAMP target is Epac, a guanine nucleotide exchange factor for the small GTPase Rap. We show here that a soluble adenylyl cyclase synthesizes the cAMP required for the acrosome reaction. Epac stimulates the exchange of GDP for GTP on Rap1, upstream of a phospholipase C. The Epac-selective cAMP analogue 8-pCPT-2'-O-Me-cAMP induces a phospholipase C-dependent calcium mobilization in human sperm suspensions. In addition, our studies identify a novel connection between cAMP and Rab3A, a secretory granule-associated protein, revealing that the latter functions downstream of soluble adenylyl cyclase/cAMP/Epac but not of Rap1. Challenging sperm with calcium or 8-pCPT-2'-O-Me-cAMP boosts the exchange of GDP for GTP on Rab3A. Recombinant Epac does not release GDP from Rab3A in vitro, suggesting that the Rab3A-GEF activation by cAMP/Epac in vivo is indirect. We propose that Epac sits at a critical point during the exocytotic cascade after which the pathway splits into two limbs, one that assembles the fusion machinery into place and another that elicits intracellular calcium release.
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Affiliation(s)
- María T Branham
- Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología-Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, CC 56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
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Arimura N, Kimura T, Nakamuta S, Taya S, Funahashi Y, Hattori A, Shimada A, Ménager C, Kawabata S, Fujii K, Iwamatsu A, Segal RA, Fukuda M, Kaibuchi K. Anterograde transport of TrkB in axons is mediated by direct interaction with Slp1 and Rab27. Dev Cell 2009; 16:675-86. [PMID: 19460344 DOI: 10.1016/j.devcel.2009.03.005] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 11/25/2008] [Accepted: 03/03/2009] [Indexed: 12/18/2022]
Abstract
The neurotrophin receptors TrkA, TrkB, and TrkC are localized at the surface of the axon terminus and transmit key signals from brain-derived neurotrophic factor (BDNF) for diverse effects on neuronal survival, differentiation, and axon formation. Trk receptors are sorted into axons via the anterograde transport of vesicles and are then inserted into axonal plasma membranes. However, the transport mechanism remains largely unknown. Here, we show that the Slp1/Rab27B/CRMP-2 complex directly links TrkB to Kinesin-1, and that this association is required for the anterograde transport of TrkB-containing vesicles. The cytoplasmic tail of TrkB binds to Slp1 in a Rab27B-dependent manner, and CRMP-2 connects Slp1 to Kinesin-1. Knockdown of these molecules by siRNA reduces the anterograde transport and membrane targeting of TrkB, thereby inhibiting BDNF-induced ERK1/2 phosphorylation in axons. Our data reveal a molecular mechanism for the selective anterograde transport of TrkB in axons and show how the transport is coupled to BDNF signaling.
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Affiliation(s)
- Nariko Arimura
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Showa, Nagoya, Japan
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Nightingale TD, Pattni K, Hume AN, Seabra MC, Cutler DF. Rab27a and MyRIP regulate the amount and multimeric state of VWF released from endothelial cells. Blood 2009; 113:5010-8. [PMID: 19270261 PMCID: PMC2686148 DOI: 10.1182/blood-2008-09-181206] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Accepted: 02/15/2009] [Indexed: 11/20/2022] Open
Abstract
Endothelial cells contain cigar-shaped secretory organelles called Weibel-Palade bodies (WPBs) that play a crucial role in both hemostasis and the initiation of inflammation. The major cargo protein of WPBs is von Willebrand factor (VWF). In unstimulated cells, this protein is stored in a highly multimerized state coiled into protein tubules, but after secretagogue stimulation and exocytosis it unfurls, under shear force, as long platelet-binding strings. Small GTPases of the Rab family play a key role in organelle function. Using siRNA depletion in primary endothelial cells, we have identified a role for the WPB-associated Rab27a and its effector MyRIP. Both these proteins are present on only mature WPBs, and this rab/effector complex appears to anchor these WPBs to peripheral actin. Depletion of either the Rab or its effector results in a loss of peripheral WPB localization, and this destabilization is coupled with an increase in both basal and stimulated secretion. The VWF released from Rab27a-depleted cells is less multimerized, and the VWF strings seen under flow are shorter. Our results indicate that this Rab/effector complex controls peripheral distribution and prevents release of incompletely processed WPB content.
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Affiliation(s)
- Thomas D Nightingale
- Medical Research Council Laboratory of Molecular Cell Biology, Cell Biology Unit, Department of Cell and Developmental Biology, University College London, London, United Kingdom. [corrected]
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A VAMP7/Vti1a SNARE complex distinguishes a non-conventional traffic route to the cell surface used by KChIP1 and Kv4 potassium channels. Biochem J 2009; 418:529-40. [PMID: 19138172 PMCID: PMC2650881 DOI: 10.1042/bj20081736] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The KChIPs (K(+) channel-interacting proteins) are EF hand-containing proteins required for the traffic of channel-forming Kv4 K(+) subunits to the plasma membrane. KChIP1 is targeted, through N-terminal myristoylation, to intracellular vesicles that appear to be trafficking intermediates from the ER (endoplasmic reticulum) to the Golgi but differ from those underlying conventional ER-Golgi traffic. To define KChIP1 vesicles and the traffic pathway followed by Kv4/KChIP1 traffic, we examined their relationship to potential SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) proteins mediating the trafficking step. To distinguish Kv4/KChIP1 from conventional constitutive traffic, we compared it to the traffic of the VSVG (vesicular-stomatitis virus G-protein). Expression of KChIP with single or triple EF hand mutations quantitatively inhibited Kv4/KChIP1 traffic to the cell surface but had no effect on VSVG traffic. KChIP1-expressing vesicles co-localized with the SNARE proteins Vti1a and VAMP7 (vesicle-associated membrane protein 7), but not with the components of two other ER-Golgi SNARE complexes. siRNA (small interfering RNA)-mediated knockdown of Vti1a or VAMP7 inhibited Kv4/KChIP1traffic to the plasma membrane in HeLa and Neuro2A cells. Vti1a and VAMP7 siRNA had no effect on VSVG traffic or that of Kv4.2 when stimulated by KChIP2, a KChIP with different intrinsic membrane targeting compared with KChIP1. The present results suggest that a SNARE complex containing VAMP7 and Vti1a defines a novel traffic pathway to the cell surface in both neuronal and non-neuronal cells.
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