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Villanueva J, Giménez-Molina Y, Gutiérrez LM. Confocal Microscopy Studies of F-Actin Cytoskeleton Distribution and Dynamics Using Fluorescent LifeAct Constructs in Bovine Adrenal Chromaffin Cells. Methods Mol Biol 2023; 2565:297-309. [PMID: 36205902 DOI: 10.1007/978-1-0716-2671-9_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Cultured bovine chromaffin cells have been characterized as a successful model to study changes in the cytoskeleton during the secretory process. In this sense, the distribution and dynamics of the F-actin cytoskeleton can be studied by confocal microscopy using appropriate molecular tools such as LifeAct, a peptide that stains the structures of F-actin. In this work, we describe some methodological protocols making possible to study, under controlled stimulus conditions, the local dynamic changes of F-actin in the cortical zone and also to detect the simultaneous displacements of chromaffin granules and organelles in active zones.
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Affiliation(s)
- José Villanueva
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, Alicante, Spain.
| | - Yolanda Giménez-Molina
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, Alicante, Spain
| | - Luis M Gutiérrez
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, Alicante, Spain
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2
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Morris T, Sue E, Geniesse C, Brieher WM, Tang VW. Synaptopodin stress fiber and contractomere at the epithelial junction. J Cell Biol 2022; 221:213132. [PMID: 35416930 PMCID: PMC9011326 DOI: 10.1083/jcb.202011162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 10/07/2021] [Accepted: 02/09/2022] [Indexed: 12/27/2022] Open
Abstract
The apical junction of epithelial cells can generate force to control cell geometry and perform contractile processes while maintaining barrier function and adhesion. Yet, the structural basis for force generation at the apical junction is not fully understood. Here, we describe two synaptopodin-dependent actomyosin structures that are spatially, temporally, and structurally distinct. The first structure is formed by the retrograde flow of synaptopodin initiated at the apical junction, creating a sarcomeric stress fiber that lies parallel to the apical junction. Contraction of the apical stress fiber is associated with either clustering of membrane components or shortening of junctional length. Upon junction maturation, apical stress fibers are disassembled. In mature epithelial monolayer, a motorized “contractomere” capable of “walking the junction” is formed at the junctional vertex. Actomyosin activities at the contractomere produce a compressive force evident by actin filament buckling and measurement with a new α-actinin-4 force sensor. The motility of contractomeres can adjust junctional length and change cell packing geometry during cell extrusion and intercellular movement. We propose a model of epithelial homeostasis that utilizes contractomere motility to support junction rearrangement while preserving the permeability barrier.
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Affiliation(s)
- Timothy Morris
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - Eva Sue
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - Caleb Geniesse
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - William M Brieher
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
| | - Vivian W Tang
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, IL
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3
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Kang F, Gaisano HY. Imaging Insulin Granule Dynamics in Human Pancreatic β-Cells Using Total Internal Reflection Fluorescence (TIRF) Microscopy. Methods Mol Biol 2022; 2473:79-88. [PMID: 35819760 DOI: 10.1007/978-1-0716-2209-4_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Due to the ultra-thin optical sectioning capability of exclusively illuminating space at the interface where total internal reflection occurs, the TIRF microscope has been indispensable for monitoring biological processes adjacent to the plasma membrane with excellent signal-to-noise ratio. Insulin-containing granules fuse with the plasma membrane to release contents within hundreds of milliseconds, which involves well-orchestrated assembly of SNARE complex and associated proteins. A video-rate multiple-color TIRF microscope offers the unique opportunity to visualize single secretory granule docking and fusion dynamics and can also map its regulators with high spatiotemporal resolution. Here, we describe the basic principles and practical implementation of a fast dual-color TIRF microscope, detailing a how-to guide on imaging and analysis of insulin granule dynamics in human β-cells.
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Affiliation(s)
- Fei Kang
- Department of Medicine, Temerty Faculty of Medicine of the University of Toronto and the Toronto General Hospital Research Institute, Toronto, ON, Canada.
| | - Herbert Y Gaisano
- Department of Medicine, Temerty Faculty of Medicine of the University of Toronto and the Toronto General Hospital Research Institute, Toronto, ON, Canada.
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4
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Runwal G, Edwards RH. The Membrane Interactions of Synuclein: Physiology and Pathology. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2021; 16:465-485. [PMID: 33497259 DOI: 10.1146/annurev-pathol-031920-092547] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Specific proteins accumulate in neurodegenerative disease, and human genetics has indicated a causative role for many. In most cases, however, the mechanisms remain poorly understood. Degeneration is thought to involve a gain of abnormal function, although we do not know the normal function of many proteins implicated. The protein α-synuclein accumulates in the Lewy pathology of Parkinson's disease and related disorders, and mutations in α-synuclein cause degeneration, but we have not known its normal function or how it triggers disease. α-Synuclein localizes to presynaptic boutons and interacts with membranes in vitro. Overexpression slows synaptic vesicle exocytosis, and recent data suggest a normal role for the endogenous synucleins in dilation of the exocytic fusion pore. Disrupted membranes also appear surprisingly prominent in Lewy pathology. Synuclein thus interacts with membranes under both physiological and pathological conditions, suggesting that the normal function of synuclein may illuminate its role in degeneration.
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Affiliation(s)
- Gautam Runwal
- Departments of Neurology and Physiology, Graduate Programs in Cell Biology, Biomedical Sciences and Neuroscience, School of Medicine, University of California, San Francisco, California 94143, USA;
| | - Robert H Edwards
- Departments of Neurology and Physiology, Graduate Programs in Cell Biology, Biomedical Sciences and Neuroscience, School of Medicine, University of California, San Francisco, California 94143, USA;
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5
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Urbina FL, Menon S, Goldfarb D, Edwards R, Ben Major M, Brennwald P, Gupton SL. TRIM67 regulates exocytic mode and neuronal morphogenesis via SNAP47. Cell Rep 2021; 34:108743. [PMID: 33567284 PMCID: PMC7941186 DOI: 10.1016/j.celrep.2021.108743] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 12/09/2020] [Accepted: 01/20/2021] [Indexed: 02/07/2023] Open
Abstract
Neuronal morphogenesis involves dramatic plasma membrane expansion, fueled by soluble N-ethylmaleimide-sensitive factor attachment protein eceptors (SNARE)-mediated exocytosis. Distinct fusion modes described at synapses include full-vesicle fusion (FVF) and kiss-and-run fusion (KNR). During FVF, lumenal cargo is secreted and vesicle membrane incorporates into the plasma membrane. During KNR, a transient fusion pore secretes cargo but closes without membrane addition. In contrast, fusion modes are not described in developing neurons. Here, we resolve individual exocytic events in developing murine cortical neurons and use classification tools to identify four distinguishable fusion modes: two FVF-like modes that insert membrane material and two KNR-like modes that do not. Discrete fluorescence profiles suggest distinct behavior of the fusion pore. Simulations and experiments agree that FVF-like exocytosis provides sufficient membrane material for morphogenesis. We find the E3 ubiquitin ligase TRIM67 promotes FVF-like exocytosis in part by limiting incorporation of the Qb/Qc SNARE SNAP47 into SNARE complexes and, thus, SNAP47 involvement in exocytosis. Urbina et al. identify four exocytic modes in developing neurons: KNRd, KNRi, FVFd, FVFi. Simulations and experiments suggest that FVFi and FVFd provide material for plasma membrane expansion. Deletion of Trim67 decreases FVFi and FVFd while reducing surface area. SNAP47 incorporation into SNARE complexes alters fusion pore behavior, increasing KNRd.
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Affiliation(s)
- Fabio L Urbina
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Shalini Menon
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dennis Goldfarb
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Institute for Informatics, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Reginald Edwards
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - M Ben Major
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Patrick Brennwald
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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6
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Gimenez-Molina Y, García-Martínez V, Villanueva J, Davletov B, Gutiérrez LM. Multiple sclerosis drug FTY-720 toxicity is mediated by the heterotypic fusion of organelles in neuroendocrine cells. Sci Rep 2019; 9:18471. [PMID: 31804600 PMCID: PMC6895052 DOI: 10.1038/s41598-019-55106-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 11/24/2019] [Indexed: 12/29/2022] Open
Abstract
FTY-720 (Fingolimod) was one of the first compounds authorized for the treatment of multiple sclerosis. Among its other activities, this sphingosine analogue enhances exocytosis in neuroendocrine chromaffin cells, altering the quantal release of catecholamines. Surprisingly, the size of chromaffin granules is reduced within few minutes of treatment, a process that is paralleled by the homotypic fusion of granules and their heterotypic fusion with mitochondria, as witnessed by dynamic confocal and TIRF microscopy. Electron microscopy studies support these observations, revealing the fusion of several vesicles with individual mitochondria to form large, round mixed organelles. This cross-fusion is SNARE-dependent, being partially prevented by the expression of an inactive form of SNAP-25. Fused mitochondria exhibit an altered redox potential, which dramatically enhances cell death. Therefore, the cross-fusion of intracellular organelles appears to be a new mechanism to be borne in mind when considering the effect of FTY-720 on the survival of neuroendocrine cells.
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Affiliation(s)
- Yolanda Gimenez-Molina
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante, 03550, Spain
| | - Virginia García-Martínez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante, 03550, Spain
| | - José Villanueva
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante, 03550, Spain
| | - Bazbek Davletov
- Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
| | - Luis M Gutiérrez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante, 03550, Spain.
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Sulzer D, Edwards RH. The physiological role of α-synuclein and its relationship to Parkinson's Disease. J Neurochem 2019; 150:475-486. [PMID: 31269263 PMCID: PMC6707892 DOI: 10.1111/jnc.14810] [Citation(s) in RCA: 193] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 06/03/2019] [Accepted: 06/28/2019] [Indexed: 12/15/2022]
Abstract
The protein α-synuclein has a central role in the pathogenesis of Parkinson's disease (PD). In this review, we discuss recent results concerning its primary function, which appears to be on cell membranes. The pre-synaptic location of synuclein has suggested a role in neurotransmitter release and it apparently associates with synaptic vesicles because of their high curvature. Indeed, synuclein over-expression inhibits synaptic vesicle exocytosis. However, loss of synuclein has not yet been shown to have a major effect on synaptic transmission. Consistent with work showing that synuclein can promote as well as sense membrane curvature, recent analysis of synuclein triple knockout mice now shows that synuclein accelerates dilation of the exocytic fusion pore. This form of regulation affects primarily the release of slowly discharged lumenal cargo such as neural peptides, but presumably also contributes to maintenance of the release site. This article is part of the Special Issue "Synuclein".
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Affiliation(s)
- David Sulzer
- Departments of Psychiatry, Neurology and Pharmacology, Columbia University Medical Center, New York State Psychiatric Institute
| | - Robert H Edwards
- Departments of Neurology and Physiology, Graduate Programs in Cell Biology, Biomedical Sciences and Neuroscience, UCSF School of Medicine
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Guček A, Gandasi NR, Omar-Hmeadi M, Bakke M, Døskeland SO, Tengholm A, Barg S. Fusion pore regulation by cAMP/Epac2 controls cargo release during insulin exocytosis. eLife 2019; 8:41711. [PMID: 31099751 PMCID: PMC6557626 DOI: 10.7554/elife.41711] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 04/28/2019] [Indexed: 12/20/2022] Open
Abstract
Regulated exocytosis establishes a narrow fusion pore as initial aqueous connection to the extracellular space, through which small transmitter molecules such as ATP can exit. Co-release of polypeptides and hormones like insulin requires further expansion of the pore. There is evidence that pore expansion is regulated and can fail in diabetes and neurodegenerative disease. Here, we report that the cAMP-sensor Epac2 (Rap-GEF4) controls fusion pore behavior by acutely recruiting two pore-restricting proteins, amisyn and dynamin-1, to the exocytosis site in insulin-secreting beta-cells. cAMP elevation restricts and slows fusion pore expansion and peptide release, but not when Epac2 is inactivated pharmacologically or in Epac2-/- (Rapgef4-/-) mice. Consistently, overexpression of Epac2 impedes pore expansion. Widely used antidiabetic drugs (GLP-1 receptor agonists and sulfonylureas) activate this pathway and thereby paradoxically restrict hormone release. We conclude that Epac2/cAMP controls fusion pore expansion and thus the balance of hormone and transmitter release during insulin granule exocytosis. Insulin is the hormone that signals to the body to take up sugar from the blood. Specialized cells in the pancreas – known as β-cells – release insulin after a meal. Before that, insulin molecules are stored in tiny granules inside the β-cells; these granules must fuse with the cells’ surface membranes to release their contents. The first step in this process creates a narrow pore that allows small molecules, but not the larger insulin molecules, to seep out. The pore then widens to release the insulin. Since the small molecules are known to act locally in the pancreas, it is possible that this “molecular sieve” is biologically important. Yet it is not clear how the pore widens. One of the problems for people with type 2 diabetes is that they release less insulin into the bloodstream. Two kinds of drugs used to treat these patients work by stimulating β-cells to release their insulin. One way to achieve this is by raising the levels of a small molecule called cAMP, which is well known to help prepare insulin granules for release. The cAMP molecule also seems to slow the widening of the pore, and Gucek et al. have now investigated how this happens at a molecular level. By observing individual granules of human β-cells using a special microscope, Gucek et al. could watch how different drugs affect pore widening and content release. They also saw that cAMP activated a protein called Epac2, which then recruited two other proteins – amisyn and dynamin – to the small pores. These two proteins together then closed the pore, rather than expanding it to let insulin out. Type 2 diabetes patients sometimes have high levels of amisyn in their β-cells, which could explain why they do not release enough insulin. The microscopy experiments also revealed that two common anti-diabetic drugs activate Epac2 and prevent the pores from widening, thereby counteracting their positive effect on insulin release. The combined effect is likely a shift in the balance between insulin and the locally acting small molecules. These findings suggest that two common anti-diabetic drugs activate a common mechanism that may lead to unexpected outcomes, possibly even reducing how much insulin the β-cells can release. Future studies in mice and humans will have to investigate these effects in whole organisms.
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Affiliation(s)
- Alenka Guček
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | | | - Marit Bakke
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | | | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Dynamin 1 Restrains Vesicular Release to a Subquantal Mode In Mammalian Adrenal Chromaffin Cells. J Neurosci 2018; 39:199-211. [PMID: 30381405 DOI: 10.1523/jneurosci.1255-18.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 10/14/2018] [Accepted: 10/15/2018] [Indexed: 12/22/2022] Open
Abstract
Dynamin 1 (dyn1) is required for clathrin-mediated endocytosis in most secretory (neuronal and neuroendocrine) cells. There are two modes of Ca2+-dependent catecholamine release from single dense-core vesicles: full-quantal (quantal) and subquantal in adrenal chromaffin cells, but their relative occurrences and impacts on total secretion remain unclear. To address this fundamental question in neurotransmission area using both sexes of animals, here we report the following: (1) dyn1-KO increased quantal size (QS, but not vesicle size/content) by ≥250% in dyn1-KO mice; (2) the KO-increased QS was rescued by dyn1 (but not its deficient mutant or dyn2); (3) the ratio of quantal versus subquantal events was increased by KO; (4) following a release event, more protein contents were retained in WT versus KO vesicles; and (5) the fusion pore size (d p) was increased from ≤9 to ≥9 nm by KO. Therefore, Ca2+-induced exocytosis is generally a subquantal release in sympathetic adrenal chromaffin cells, implying that neurotransmitter release is generally regulated by dynamin in neuronal cells.SIGNIFICANCE STATEMENT Ca2+-dependent neurotransmitter release from a single vesicle is the primary event in all neurotransmission, including synaptic/neuroendocrine forms. To determine whether Ca2+-dependent vesicular neurotransmitter release is "all-or-none" (quantal), we provide compelling evidence that most Ca2+-induced secretory events occur via the subquantal mode in native adrenal chromaffin cells. This subquantal release mode is promoted by dynamin 1, which is universally required for most secretory cells, including neurons and neuroendocrine cells. The present work with dyn1-KO mice further confirms that Ca2+-dependent transmitter release is mainly via subquantal mode, suggesting that subquantal release could be also important in other types of cells.
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Gimenez-Molina Y, Villanueva J, Francés MDM, Viniegra S, Gutiérrez LM. Multiple Mechanisms Driving F-actin-Dependent Transport of Organelles to and From Secretory Sites in Bovine Chromaffin Cells. Front Cell Neurosci 2018; 12:344. [PMID: 30356839 PMCID: PMC6190647 DOI: 10.3389/fncel.2018.00344] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 09/18/2018] [Indexed: 01/12/2023] Open
Abstract
Neuroendocrine chromaffin cells represent an excellent model to study the molecular mechanisms associated with the exo-endocytotic cycle of neurotransmitter release. In this study, EGFP-Lifeact and confocal microscopy has been used to analyze the re-organization of the cortical F-actin cytoskeleton associated to organelle transport during secretion with unprecedented detail. In these cells secretory events accumulate in temperature-sensitive and myosin II-dependent F-actin expansions and retractions affecting specific regions of the sub-membrane space. Interestingly, not only vesicles but also mitochondria are transported toward the plasmalemma during these expansions. Simultaneously, we found F-actin cytoskeletal retraction withdraws vesicles from the sub-plasmalemmal space, forming novel empty internal spaces into which organelles can be transported. In addition to these well-coordinated, F-actin-myosin II dependent processes that drive the transport of the majority of vesicles, fast transport of chromaffin vesicles was observed, albeit less frequently, which used F-actin comet tails nucleated from the granular membrane. Thus, upon cell stimulation F-actin structures use diverse mechanisms to transport organelles to and from the membrane during the exo-endocytotic cycle taking place in specific areas of cell periphery.
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Affiliation(s)
- Yolanda Gimenez-Molina
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, San Juan de Alicante, Spain
| | - José Villanueva
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, San Juan de Alicante, Spain
| | - Maria Del Mar Francés
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, San Juan de Alicante, Spain
| | - Salvador Viniegra
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, San Juan de Alicante, Spain
| | - Luis M Gutiérrez
- Instituto de Neurociencias, Centro Mixto CSIC-Universidad Miguel Hernández, San Juan de Alicante, Spain
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11
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Wang G, Galli T. Reciprocal link between cell biomechanics and exocytosis. Traffic 2018; 19:741-749. [PMID: 29943478 DOI: 10.1111/tra.12584] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Revised: 06/03/2018] [Accepted: 06/03/2018] [Indexed: 12/16/2022]
Abstract
A cell is able to sense the biomechanical properties of the environment such as the rigidity of the extracellular matrix and adapt its tension via regulation of plasma membrane and underlying actomyosin meshwork properties. The cell's ability to adapt to the changing biomechanical environment is important for cellular homeostasis and also cell dynamics such as cell growth and motility. Membrane trafficking has emerged as an important mechanism to regulate cell biomechanics. In this review, we summarize the current understanding of the role of cell mechanics in exocytosis, and reciprocally, the role of exocytosis in regulating cell mechanics. We also discuss how cell mechanics and membrane trafficking, particularly exocytosis, can work together to regulate cell polarity and motility.
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Affiliation(s)
- Guan Wang
- Membrane Traffic in Healthy & Diseased Brain, Center of Psychiatry and Neurosciences, INSERM U894, Sorbonne Paris-Cité, Université Paris Descartes, Paris, France
| | - Thierry Galli
- Membrane Traffic in Healthy & Diseased Brain, Center of Psychiatry and Neurosciences, INSERM U894, Sorbonne Paris-Cité, Université Paris Descartes, Paris, France
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12
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Takizawa M, Harada K, Nakamura K, Tsuboi T. Transient receptor potential ankyrin 1 channels are involved in spontaneous peptide hormone release from astrocytes. Biochem Biophys Res Commun 2018; 501:988-995. [DOI: 10.1016/j.bbrc.2018.05.097] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 05/15/2018] [Indexed: 12/19/2022]
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13
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Makhmutova M, Liang T, Gaisano H, Caicedo A, Almaça J. Confocal Imaging of Neuropeptide Y-pHluorin: A Technique to Visualize Insulin Granule Exocytosis in Intact Murine and Human Islets. J Vis Exp 2017. [PMID: 28930993 DOI: 10.3791/56089] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Insulin secretion plays a central role in glucose homeostasis under normal physiological conditions as well as in disease. Current approaches to study insulin granule exocytosis either use electrophysiology or microscopy coupled to the expression of fluorescent reporters. However most of these techniques have been optimized for clonal cell lines or require dissociating pancreatic islets. In contrast, the method presented here allows for real time visualization of insulin granule exocytosis in intact pancreatic islets. In this protocol, we first describe the viral infection of isolated pancreatic islets with adenovirus that encodes a pH-sensitive green fluorescent protein (GFP), pHluorin, coupled to neuropeptide Y (NPY). Second, we describe the confocal imaging of islets five days after viral infection and how to monitor the insulin granule secretion. Briefly, the infected islets are placed on a coverslip on an imaging chamber and imaged under an upright laser-scanning confocal microscope while being continuously perfused with extracellular solution containing various stimuli. Confocal images spanning 50 µm of the islet are acquired as time-lapse recordings using a fast-resonant scanner. The fusion of insulin granules with the plasma membrane can be followed over time. This procedure also allows for testing a battery of stimuli in a single experiment, is compatible with both mouse and human islets, and can be combined with various dyes for functional imaging (e.g., membrane potential or cytosolic calcium dyes).
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Affiliation(s)
| | - Tao Liang
- Department of Medicine, University of Toronto
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14
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Gaisano HY. Recent new insights into the role of SNARE and associated proteins in insulin granule exocytosis. Diabetes Obes Metab 2017; 19 Suppl 1:115-123. [PMID: 28880475 DOI: 10.1111/dom.13001] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 04/23/2017] [Accepted: 05/02/2017] [Indexed: 01/22/2023]
Abstract
Initial work on the exocytotic machinery of predocked insulin secretory granules (SGs) in pancreatic β-cells mimicked the SNARE hypothesis work in neurons, which includes SM/SNARE complex and associated priming proteins, fusion clamps and Ca2+ sensors. However, β-cell SGs, unlike neuronal synaptic vesicles, exhibit a biphasic secretory response that requires additional distinct features in exocytosis including newcomer SGs that undergo minimal docking time at the plasma membrane (PM) before fusion and multi-SG (compound) fusion. These exocytotic events are mediated by Munc18/SNARE complexes distinct from that which mediates predocked SG fusion. We review some recent insights in SNARE complex assembly and the promiscuity in SM/SNARE complex formation, whereby both contribute to conferring different insulin SG fusion kinetics. Some SNARE and associated proteins play non-fusion roles, including tethering SGs to Ca2+ channels, SG recruitment from cell interior to PM, and inhibitory SNAREs that block the action of profusion SNAREs. We discuss new insights into how sub-PM cytoskeletal mesh gates SG access to the PM and the targeting of SG exocytosis to PM domains in functionally polarized β-cells within intact islets. These recent developments have major implications on devising clever SNARE replacement therapies that could restore the deficient insulin secretion in diabetic islet β-cells.
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15
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Abstract
Regulated exocytosis can be split into a sequence of steps ending with the formation and the dilation of a fusion pore, a neck-like connection between the vesicle and the plasma membrane. Each of these steps is precisely controlled to achieve the optimal spatial and temporal profile of the release of signalling molecules. At the level of the fusion pore, tuning of the exocytosis can be achieved by preventing its formation, by stabilizing the unproductive narrow fusion pore, by altering the speed of fusion pore expansion and by completely closing the fusion pore. The molecular structure and dynamics of fusion pores have become a major focus of cell research, especially as a promising target for therapeutic strategies. Electrophysiological, optical and electrochemical methods have been used extensively to illuminate how cells regulate secretion at the level of a single fusion pore. Here, we describe recent advances in the structure and mechanisms of the initial fusion pore formation and the progress in therapeutic strategies with the focus on exocytosis.
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Gutiérrez LM, Villanueva J. The role of F-actin in the transport and secretion of chromaffin granules: an historic perspective. Pflugers Arch 2017; 470:181-186. [PMID: 28730385 PMCID: PMC5748413 DOI: 10.1007/s00424-017-2040-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 07/13/2017] [Accepted: 07/14/2017] [Indexed: 12/23/2022]
Abstract
Actin is one of the most ubiquitous protein playing fundamental roles in a variety of cellular processes. Since early in the 1980s, it was evident that filamentous actin (F-actin) formed a peripheral cortical barrier that prevented vesicles to access secretory sites in chromaffin cells in culture. Later, around 2000, it was described that the F-actin structure accomplishes a dual role serving both vesicle transport and retentive purposes and undergoing dynamic transient changes during cell stimulation. The complex role of the F-actin cytoskeleton in neuroendocrine secretion was further evidenced when it has been proved to participate in the scaffold structure holding together the secretory machinery at active sites and participate in the generation of mechanical forces that drive the opening of the fusion pore, during the first decade of the present century. The complex vision of the multiple roles of F-actin in secretion we have acquired to date comes largely from studies performed on traditional 2D cultures of primary cells; however, recent evidences suggest that these may not accurately mimic the 3D in vivo environment, and thus, more work is now needed on adrenomedullary cells kept in a more “native” configuration to fully understand the role of F-actin in regulating chromaffin granule transport and secretion under physiological conditions.
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Affiliation(s)
- Luis M Gutiérrez
- Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández, Sant Joan d'Alacant, 03550, Alicante, Spain.
| | - José Villanueva
- Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández, Sant Joan d'Alacant, 03550, Alicante, Spain
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17
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Papadopulos A. Membrane shaping by actin and myosin during regulated exocytosis. Mol Cell Neurosci 2017; 84:93-99. [PMID: 28536001 DOI: 10.1016/j.mcn.2017.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 04/21/2017] [Accepted: 05/19/2017] [Indexed: 12/01/2022] Open
Abstract
The cortical actin network in neurosecretory cells is a dense mesh of actin filaments underlying the plasma membrane. Interaction of actomyosin with vesicular membranes or the plasma membrane is vital for tethering, retention, transport as well as fusion and fission of exo- and endocytic membrane structures. During regulated exocytosis the cortical actin network undergoes dramatic changes in morphology to accommodate vesicle docking, fusion and replenishment. Most of these processes involve plasma membrane Phosphoinositides (PIP) and investigating the interactions between the actin cortex and secretory structures has become a hotbed for research in recent years. Actin remodelling leads to filopodia outgrowth and the creation of new fusion sites in neurosecretory cells and actin, myosin and dynamin actively shape and maintain the fusion pore of secretory vesicles. Changes in viscoelastic properties of the actin cortex can facilitate vesicular transport and lead to docking and priming of vesicle at the plasma membrane. Small GTPase actin mediators control the state of the cortical actin network and influence vesicular access to their docking and fusion sites. These changes potentially affect membrane properties such as tension and fluidity as well as the mobility of embedded proteins and could influence the processes leading to both exo- and endocytosis. Here we discuss the multitudes of actin and membrane interactions that control successive steps underpinning regulated exocytosis.
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Affiliation(s)
- Andreas Papadopulos
- The Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, 4072, Australia.
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Liang K, Wei L, Chen L. Exocytosis, Endocytosis, and Their Coupling in Excitable Cells. Front Mol Neurosci 2017; 10:109. [PMID: 28469555 PMCID: PMC5395637 DOI: 10.3389/fnmol.2017.00109] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 03/31/2017] [Indexed: 11/13/2022] Open
Abstract
Evoked exocytosis in excitable cells is fast and spatially confined and must be followed by coupled endocytosis to enable sustained exocytosis while maintaining the balance of the vesicle pool and the plasma membrane. Various types of exocytosis and endocytosis exist in these excitable cells, as those has been found from different types of experiments conducted in different cell types. Correlating these diversified types of exocytosis and endocytosis is problematic. By providing an outline of different exocytosis and endocytosis processes and possible coupling mechanisms here, we emphasize that the endocytic pathway may be pre-determined at the time the vesicle chooses to fuse with the plasma membrane in one specific mode. Therefore, understanding the early intermediate stages of vesicle exocytosis may be instrumental in exploring the mechanism of tailing endocytosis.
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Affiliation(s)
- Kuo Liang
- Department of General Surgery, XuanWu Hospital, Capital Medical UniversityBeijing, China
| | - Lisi Wei
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
| | - Liangyi Chen
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
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Arous C, Halban PA. The skeleton in the closet: actin cytoskeletal remodeling in β-cell function. Am J Physiol Endocrinol Metab 2015; 309:E611-20. [PMID: 26286869 DOI: 10.1152/ajpendo.00268.2015] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/11/2015] [Indexed: 01/13/2023]
Abstract
Over the last few decades, biomedical research has considered not only the function of single cells but also the importance of the physical environment within a whole tissue, including cell-cell and cell-extracellular matrix interactions. Cytoskeleton organization and focal adhesions are crucial sensors for cells that enable them to rapidly communicate with the physical extracellular environment in response to extracellular stimuli, ensuring proper function and adaptation. The involvement of the microtubular-microfilamentous cytoskeleton in secretion mechanisms was proposed almost 50 years ago, since when the evolution of ever more sensitive and sophisticated methods in microscopy and in cell and molecular biology have led us to become aware of the importance of cytoskeleton remodeling for cell shape regulation and its crucial link with signaling pathways leading to β-cell function. Emerging evidence suggests that dysfunction of cytoskeletal components or extracellular matrix modification influences a number of disorders through potential actin cytoskeleton disruption that could be involved in the initiation of multiple cellular functions. Perturbation of β-cell actin cytoskeleton remodeling could arise secondarily to islet inflammation and fibrosis, possibly accounting in part for impaired β-cell function in type 2 diabetes. This review focuses on the role of actin remodeling in insulin secretion mechanisms and its close relationship with focal adhesions and myosin II.
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Affiliation(s)
- Caroline Arous
- Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland
| | - Philippe A Halban
- Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland
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20
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Oya M, Kitaguchi T, Harada K, Numano R, Sato T, Kojima M, Tsuboi T. Low glucose-induced ghrelin secretion is mediated by an ATP-sensitive potassium channel. J Endocrinol 2015; 226:25-34. [PMID: 26099355 DOI: 10.1530/joe-15-0090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ghrelin is synthesized in X/A-like cells of the gastric mucosa, which plays an important role in the regulation of energy homeostasis. Although ghrelin secretion is known to be induced by neurotransmitters or hormones or by nutrient sensing in the ghrelin-secreting cells themselves, the mechanism of ghrelin secretion is not clearly understood. In the present study, we found that changing the extracellular glucose concentration from elevated (25 mM) to optimal (10 mM) caused an increase in the intracellular Ca2+ concentration ([Ca2+]i) in ghrelin-secreting mouse ghrelinoma 3-1 (MGN3-1) cells (n=32, P<0.01), whereas changing the glucose concentration from elevated to lowered (5 or 1 mM) had little effect on [Ca2+]i increase. Overexpression of a closed form of an ATP-sensitive K+ (KATP) channel mutant suppressed the 10 mM glucose-induced [Ca2+]i increase (n=8, P<0.01) and exocytotic events (n=6, P<0.01). We also found that a low concentration of a KATP channel opener, diazoxide, with 25 mM glucose induced [Ca2+]i increase (n=23, P<0.01) and ghrelin secretion (n≥3, P<0.05). In contrast, the application of a low concentration of a KATP channel blocker, tolbutamide, significantly induced [Ca2+]i increase (n=15, P<0.01) and ghrelin secretion (n≥3, P<0.05) under 5 mM glucose. Furthermore, the application of voltage-dependent Ca2+ channel inhibitors suppressed the 10 mM glucose-induced [Ca2+]i increase (n≥26, P<0.01) and ghrelin secretion (n≥5, P<0.05). These findings suggest that KATP and voltage-dependent Ca2+ channels are involved in glucose-dependent ghrelin secretion in MGN3-1 cells.
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Affiliation(s)
- Manami Oya
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Tetsuya Kitaguchi
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Kazuki Harada
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Rika Numano
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Takahiro Sato
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Masayasu Kojima
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Takashi Tsuboi
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
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21
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Papadopulos A, Gomez GA, Martin S, Jackson J, Gormal RS, Keating DJ, Yap AS, Meunier FA. Activity-driven relaxation of the cortical actomyosin II network synchronizes Munc18-1-dependent neurosecretory vesicle docking. Nat Commun 2015; 6:6297. [DOI: 10.1038/ncomms7297] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Accepted: 01/14/2015] [Indexed: 01/08/2023] Open
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22
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Flores JA, Balseiro-Gomez S, Cabeza JM, Acosta J, Ramirez-Ponce P, Ales E. A new role for myosin II in vesicle fission. PLoS One 2014; 9:e100757. [PMID: 24959909 PMCID: PMC4069105 DOI: 10.1371/journal.pone.0100757] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/28/2014] [Indexed: 11/19/2022] Open
Abstract
An endocytic vesicle is formed from a flat plasma membrane patch by a sequential process of invagination, bud formation and fission. The scission step requires the formation of a tubular membrane neck (the fission pore) that connects the endocytic vesicle with the plasma membrane. Progress in vesicle fission can be measured by the formation and closure of the fission pore. Live-cell imaging and sensitive biophysical measurements have provided various glimpses into the structure and behaviour of the fission pore. In the present study, the role of non-muscle myosin II (NM-2) in vesicle fission was tested by analyzing the kinetics of the fission pore with perforated-patch clamp capacitance measurements to detect single vesicle endocytosis with millisecond time resolution in peritoneal mast cells. Blebbistatin, a specific inhibitor of NM-2, dramatically increased the duration of the fission pore and also prevented closure during large endocytic events. Using the fluorescent markers FM1-43 and pHrodo Green dextran, we found that NM-2 inhibition greatly arrested vesicle fission in a late phase of the scission event when the pore reached a final diameter of ∼ 5 nm. Our results indicate that loss of the ATPase activity of myosin II drastically reduces the efficiency of membrane scission by making vesicle closure incomplete and suggest that NM-2 might be especially relevant in vesicle fission during compound endocytosis.
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Affiliation(s)
- Juan A. Flores
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Santiago Balseiro-Gomez
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Jose M. Cabeza
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Jorge Acosta
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Pilar Ramirez-Ponce
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Eva Ales
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
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23
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Papadopulos A, Tomatis VM, Kasula R, Meunier FA. The cortical acto-Myosin network: from diffusion barrier to functional gateway in the transport of neurosecretory vesicles to the plasma membrane. Front Endocrinol (Lausanne) 2013; 4:153. [PMID: 24155741 PMCID: PMC3800816 DOI: 10.3389/fendo.2013.00153] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 10/05/2013] [Indexed: 01/14/2023] Open
Abstract
Dysregulation of regulated exocytosis is linked to an array of pathological conditions, including neurodegenerative disorders, asthma, and diabetes. Understanding the molecular mechanisms underpinning neuroexocytosis including the processes that allow neurosecretory vesicles to access and fuse with the plasma membrane and to recycle post-fusion, is therefore critical to the design of future therapeutic drugs that will efficiently tackle these diseases. Despite considerable efforts to determine the principles of vesicular fusion, the mechanisms controlling the approach of vesicles to the plasma membrane in order to undergo tethering, docking, priming, and fusion remain poorly understood. All these steps involve the cortical actin network, a dense mesh of actin filaments localized beneath the plasma membrane. Recent work overturned the long-held belief that the cortical actin network only plays a passive constraining role in neuroexocytosis functioning as a physical barrier that partly breaks down upon entry of Ca(2+) to allow secretory vesicles to reach the plasma membrane. A multitude of new roles for the cortical actin network in regulated exocytosis have now emerged and point to highly dynamic novel functions of key myosin molecular motors. Myosins are not only believed to help bring about dynamic changes in the actin cytoskeleton, tethering and guiding vesicles to their fusion sites, but they also regulate the size and duration of the fusion pore, thereby directly contributing to the release of neurotransmitters and hormones. Here we discuss the functions of the cortical actin network, myosins, and their effectors in controlling the processes that lead to tethering, directed transport, docking, and fusion of exocytotic vesicles in regulated exocytosis.
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Affiliation(s)
- Andreas Papadopulos
- Queensland Brain Institute, The University of Queensland, St Lucia Campus, Brisbane, QLD, Australia
| | - Vanesa M. Tomatis
- Queensland Brain Institute, The University of Queensland, St Lucia Campus, Brisbane, QLD, Australia
| | - Ravikiran Kasula
- Queensland Brain Institute, The University of Queensland, St Lucia Campus, Brisbane, QLD, Australia
| | - Frederic A. Meunier
- Queensland Brain Institute, The University of Queensland, St Lucia Campus, Brisbane, QLD, Australia
- *Correspondence: Frederic A. Meunier, Queensland Brain Institute, The University of Queensland, St Lucia Campus, QBI Building #79, St Lucia, QLD 4072, Australia e-mail:
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Otterstrom J, van Oijen AM. Visualization of membrane fusion, one particle at a time. Biochemistry 2013; 52:1654-68. [PMID: 23421412 DOI: 10.1021/bi301573w] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Protein-mediated fusion between phospholipid bilayers is a fundamental and necessary mechanism for many cellular processes. The short-lived nature of the intermediate states visited during fusion makes it challenging to capture precise kinetic information using classical, ensemble-averaging biophysical techniques. Recently, a number of single-particle fluorescence microscopy-based assays that allow researchers to obtain highly quantitative data about the fusion process by observing individual fusion events in real time have been developed. These assays depend upon changes in the acquired fluorescence signal to provide a direct readout for transitions between the various fusion intermediates. The resulting data yield meaningful and detailed kinetic information about the transitory states en route to productive membrane fusion. In this review, we highlight recent in vitro and in vivo studies of membrane fusion at the single-particle level in the contexts of viral membrane fusion and SNARE-mediated synaptic vesicle fusion. These studies afford insight into mechanisms of coordination between fusion-mediating proteins as well as coordination of the overall fusion process with other cellular processes. The development of single-particle approaches to investigate membrane fusion and their successful application to a number of model systems have resulted in a new experimental paradigm and open up considerable opportunities to extend these methods to other biological processes that involve membrane fusion.
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Affiliation(s)
- Jason Otterstrom
- Harvard Biophysics Program, Harvard Medical School , 240 Longwood Avenue, Boston, Massachusetts 02115, United States
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25
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Oya M, Kitaguchi T, Pais R, Reimann F, Gribble F, Tsuboi T. The G protein-coupled receptor family C group 6 subtype A (GPRC6A) receptor is involved in amino acid-induced glucagon-like peptide-1 secretion from GLUTag cells. J Biol Chem 2012; 288:4513-21. [PMID: 23269670 DOI: 10.1074/jbc.m112.402677] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Although amino acids are dietary nutrients that evoke the secretion of glucagon-like peptide 1 (GLP-1) from intestinal L cells, the precise molecular mechanism(s) by which amino acids regulate GLP-1 secretion from intestinal L cells remains unknown. Here, we show that the G protein-coupled receptor (GPCR), family C group 6 subtype A (GPRC6A), is involved in amino acid-induced GLP-1 secretion from the intestinal L cell line GLUTag. Application of l-ornithine caused an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in GLUTag cells. Application of a GPRC6A receptor antagonist, a phospholipase C inhibitor, or an IP(3) receptor antagonist significantly suppressed the l-ornithine-induced [Ca(2+)](i) increase. We found that the increase in [Ca(2+)](i) stimulated by l-ornithine correlated with GLP-1 secretion and that l-ornithine stimulation increased exocytosis in a dose-dependent manner. Furthermore, depletion of endogenous GPRC6A by a specific small interfering RNA (siRNA) inhibited the l-ornithine-induced [Ca(2+)](i) increase and GLP-1 secretion. Taken together, these findings suggest that the GPRC6A receptor functions as an amino acid sensor in GLUTag cells that promotes GLP-1 secretion.
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Affiliation(s)
- Manami Oya
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
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26
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The plasminogen activation system and the regulation of catecholaminergic function. J Biomed Biotechnol 2012; 2012:721657. [PMID: 23097598 PMCID: PMC3477892 DOI: 10.1155/2012/721657] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 05/17/2012] [Indexed: 11/29/2022] Open
Abstract
The local environment of neurosecretory cells contains the major components of the plasminogen activation system, including the plasminogen activators, tissue plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), as well as binding sites for t-PA, the receptor for u-PA (uPAR), and also the plasminogen activator inhibitor, PAI-1. Furthermore, these cells express specific binding sites for plasminogen, which is available in the circulation and in interstitial fluid. Colocalization of plasminogen and its activators on cell surfaces provides a mechanism for promoting local plasminogen activation. Plasmin is retained on the cell surface where it is protected from its inhibitor, α2-antiplasmin. In neurosecretory cells, localized plasmin activity provides a mechanism for extracellular processing of secreted hormones. Neurotransmitter release from catecholaminergic cells is negatively regulated by cleavage products formed by plasmin-mediated proteolysis. Recently, we have identified a major plasminogen receptor, Plg-RKT. We have found that Plg-RKT is highly expressed in chromaffin cells of the adrenal medulla as well as in other catecholaminergic cells and tissues. Plg-RKT-dependent plasminogen activation plays a key role in regulating catecholaminergic neurosecretory cell function.
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27
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Multiple roles for the actin cytoskeleton during regulated exocytosis. Cell Mol Life Sci 2012; 70:2099-121. [PMID: 22986507 DOI: 10.1007/s00018-012-1156-5] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/28/2012] [Accepted: 08/30/2012] [Indexed: 01/01/2023]
Abstract
Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e., secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane, and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules.
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28
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Villanueva J, Torres V, Torregrosa-Hetland CJ, Garcia-Martinez V, López-Font I, Viniegra S, Gutiérrez LM. F-actin-myosin II inhibitors affect chromaffin granule plasma membrane distance and fusion kinetics by retraction of the cytoskeletal cortex. J Mol Neurosci 2012; 48:328-38. [PMID: 22588981 DOI: 10.1007/s12031-012-9800-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 04/30/2012] [Indexed: 11/25/2022]
Abstract
Chromaffin cell catecholamines are released when specialized secretory vesicles undergo exocytotic membrane fusion. Evidence indicates that vesicle supply and fusion are controlled by the activity of the cortical F-actin-myosin II network. To study in detail cell cortex and vesicle interactions, we use fluorescent labeling with GFP-lifeact and acidotropic dyes in confocal and evanescent wave microscopy. These techniques provide structural details and dynamic images of chromaffin granules caged in a complex cortical structure. Both the movement of cortical structures and granule motion appear to be linked, and this motion can be restricted by the myosin II-specific inhibitor, blebbistatin, and the F-actin stabilizer, jasplakinolide. These treatments also affect the position of the vesicles in relation to the plasma membrane, increasing the distance between them and the fusion sites. Consequently, we observed slower single vesicle fusion kinetics in treated cells after neutralization of acridine orange-loaded granules during exocytosis. Increasing the distance between the granules and the fusion sites appears to be linked to the retraction of the F-actin cytoskeleton when treated with jasplakinolide. Thus, F-actin-myosin II inhibitors appear to slow granule fusion kinetics by altering the position of vesicles after relaxation of the cortical network.
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Affiliation(s)
- José Villanueva
- Instituto de Neurociencias, Centro Mixto Universidad Miguel Hernández-CSIC, Sant Joan d'Alacant, Alicante 03550, Spain
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Heissler SM, Manstein DJ. Nonmuscle myosin-2: mix and match. Cell Mol Life Sci 2012; 70:1-21. [PMID: 22565821 PMCID: PMC3535348 DOI: 10.1007/s00018-012-1002-9] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 04/16/2012] [Accepted: 04/17/2012] [Indexed: 12/31/2022]
Abstract
Members of the nonmuscle myosin-2 (NM-2) family of actin-based molecular motors catalyze the conversion of chemical energy into directed movement and force thereby acting as central regulatory components of the eukaryotic cytoskeleton. By cyclically interacting with adenosine triphosphate and F-actin, NM-2 isoforms promote cytoskeletal force generation in established cellular processes like cell migration, shape changes, adhesion dynamics, endo- and exo-cytosis, and cytokinesis. Novel functions of the NM-2 family members in autophagy and viral infection are emerging, making NM-2 isoforms regulators of nearly all cellular processes that require the spatiotemporal organization of cytoskeletal scaffolding. Here, we assess current views about the role of NM-2 isoforms in these activities including the tight regulation of NM-2 assembly and activation through phosphorylation and how NM-2-mediated changes in cytoskeletal dynamics and mechanics affect cell physiological functions in health and disease.
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Affiliation(s)
- Sarah M. Heissler
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Dietmar J. Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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30
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Gutiérrez LM. New insights into the role of the cortical cytoskeleton in exocytosis from neuroendocrine cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 295:109-37. [PMID: 22449488 DOI: 10.1016/b978-0-12-394306-4.00009-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The cortical cytoskeleton is a dense network of filamentous actin (F-actin) that participates in the events associated with secretion from neuroendocrine cells. This filamentous web traps secretory vesicles, acting as a retention system that blocks the access of vesicles to secretory sites during the resting state, and it mediates their active directional transport during stimulation. The changes in the cortical cytoskeleton that drive this functional transformation have been well documented, particularly in cultured chromaffin cells. At the biochemical level, alterations in F-actin are governed by the activity of molecular motors like myosins II and V and by other calcium-dependent proteins that influence the polymerization and cross-linking of F-actin structures. In addition to modulating vesicle transport, the F-actin cortical network and its associated motor proteins also influence the late phases of the secretory process, including membrane fusion and the release of active substances through the exocytotic fusion pore. Here, we discuss the potential interactions between the F-actin cortical web and proteins such as SNAREs during secretion. We also discuss the role of the cytoskeleton in organizing the molecular elements required to sustain regulated exocytosis, forming a molecular structure that foments the efficient release of neurotransmitters and hormones.
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Affiliation(s)
- Luis M Gutiérrez
- Instituto de Neurociencias, Centro Mixto Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, Alicante, Spain
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31
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Keighron JD, Ewing AG, Cans AS. Analytical tools to monitor exocytosis: a focus on new fluorescent probes and methods. Analyst 2012; 137:1755-63. [DOI: 10.1039/c2an15901e] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Abstract
Biological research has always tremendously benefited from the development of key methodology. In fact, it was the advent of microscopy that shaped our understanding of cells as the fundamental units of life. Microscopic techniques are still central to the elucidation of biological units and processes, but equally important are methods that allow access to the dimension of time, to investigate the dynamics of molecular functions and interactions. Here, fluorescence spectroscopy with its sensitivity to access the single-molecule level, and its large temporal resolution, has been opening up fully new perspectives for cell biology. Here we summarize the key fluorescent techniques used to study cellular dynamics, with the focus on lipid and membrane systems.
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Bond LM, Brandstaetter H, Sellers JR, Kendrick-Jones J, Buss F. Myosin motor proteins are involved in the final stages of the secretory pathways. Biochem Soc Trans 2011; 39:1115-9. [PMID: 21936774 PMCID: PMC3403808 DOI: 10.1042/bst0391115] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In eukaryotes, the final steps in both the regulated and constitutive secretory pathways can be divided into four distinct stages: (i) the 'approach' of secretory vesicles/granules to the PM (plasma membrane), (ii) the 'docking' of these vesicles/granules at the membrane itself, (iii) the 'priming' of the secretory vesicles/granules for the fusion process, and, finally, (iv) the 'fusion' of vesicular/granular membranes with the PM to permit content release from the cell. Recent work indicates that non-muscle myosin II and the unconventional myosin motor proteins in classes 1c/1e, Va and VI are specifically involved in these final stages of secretion. In the present review, we examine the roles of these myosins in these stages of the secretory pathway and the implications of their roles for an enhanced understanding of secretion in general.
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Affiliation(s)
- Lisa M. Bond
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Hemma Brandstaetter
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - James R. Sellers
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | | | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
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Oya M, Suzuki H, Watanabe Y, Sato M, Tsuboi T. Amino acid taste receptor regulates insulin secretion in pancreatic β-cell line MIN6 cells. Genes Cells 2011; 16:608-16. [PMID: 21470345 DOI: 10.1111/j.1365-2443.2011.01509.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amino acids such as L-glutamate and L-arginine are potent stimuli for insulin secretion from pancreatic β-cells. However, the precise molecular mechanisms of amino acid-induced insulin secretion have only partly understood. In this study, we show here that mouse pancreatic β-cell line MIN6 cells expressed amino acid taste receptor (heterodimer of type 1 taste G protein-coupled receptor member 1 and member 3; Tas1R1 and Tas1R3, respectively). We found that administration of L-glutamate or L-arginine to MIN6 cells caused the increase in free intracellular concentrations of both inositol-1,4,5-triphosphate (IP(3)) and Ca(2+) , and umami substance inocinate enhanced the effects of l-glutamate. Effects of amino acids on intracellular IP(3) and Ca(2+) concentration were diminished by application of lactisole, a Tas1R3 receptor antagonist. Furthermore, we investigated the effect of amino acids on the insulin release from MIN6 cells by both ELISA and total internal reflection fluorescence microscopy. Application of L-glutamate or L-arginine significantly increased the release of insulin, whereas inhibited by the application of lactisole. Based on these findings, we propose that heterodimer of Tas1R1 and Tas1R3 is the fundamental receptor for the sensing amino acids and regulates the amino acid-induced insulin secretion in pancreatic β-cells.
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Affiliation(s)
- Manami Oya
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Japan
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Ueno H, Huang X, Tanaka Y, Hirokawa N. KIF16B/Rab14 Molecular Motor Complex Is Critical for Early Embryonic Development by Transporting FGF Receptor. Dev Cell 2011; 20:60-71. [DOI: 10.1016/j.devcel.2010.11.008] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 10/04/2010] [Accepted: 11/10/2010] [Indexed: 11/25/2022]
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