101
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Munc13-1 MUN domain and Munc18-1 cooperatively chaperone SNARE assembly through a tetrameric complex. Proc Natl Acad Sci U S A 2019; 117:1036-1041. [PMID: 31888993 DOI: 10.1073/pnas.1914361117] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Munc13-1 is a large multifunctional protein essential for synaptic vesicle fusion and neurotransmitter release. Its dysfunction has been linked to many neurological disorders. Evidence suggests that the MUN domain of Munc13-1 collaborates with Munc18-1 to initiate SNARE assembly, thereby priming vesicles for fast calcium-triggered vesicle fusion. The underlying molecular mechanism, however, is poorly understood. Recently, it was found that Munc18-1 catalyzes neuronal SNARE assembly through an obligate template complex intermediate containing Munc18-1 and 2 SNARE proteins-syntaxin 1 and VAMP2. Here, using single-molecule force spectroscopy, we discovered that the MUN domain of Munc13-1 stabilizes the template complex by ∼2.1 kBT. The MUN-bound template complex enhances SNAP-25 binding to the templated SNAREs and subsequent full SNARE assembly. Mutational studies suggest that the MUN-bound template complex is functionally important for SNARE assembly and neurotransmitter release. Taken together, our observations provide a potential molecular mechanism by which Munc13-1 and Munc18-1 cooperatively chaperone SNARE folding and assembly, thereby regulating synaptic vesicle fusion.
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102
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Pons-Vizcarra M, Kurps J, Tawfik B, Sørensen JB, van Weering JRT, Verhage M. MUNC18-1 regulates the submembrane F-actin network, independently of syntaxin1 targeting, via hydrophobicity in β-sheet 10. J Cell Sci 2019; 132:jcs.234674. [PMID: 31719162 DOI: 10.1242/jcs.234674] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 11/01/2019] [Indexed: 01/08/2023] Open
Abstract
MUNC18-1 (also known as STXBP1) is an essential protein for docking and fusion of secretory vesicles. Mouse chromaffin cells (MCCs) lacking MUNC18-1 show impaired secretory vesicle docking, but also mistargeting of SNARE protein syntaxin1 and an abnormally dense submembrane F-actin network. Here, we tested the contribution of both these phenomena to docking and secretion defects in MUNC18-1-deficient MCCs. We show that an abnormal F-actin network and syntaxin1 targeting defects are not observed in Snap25- or Syt1-knockout (KO) MCCs, which are also secretion deficient. We identified a MUNC18-1 mutant (V263T in β-sheet 10) that fully restores syntaxin1 targeting but not F-actin abnormalities in Munc18-1-KO cells. MUNC18-2 and -3 (also known as STXBP2 and STXBP3, respectively), which lack the hydrophobic residue at position 263, also did not restore a normal F-actin network in Munc18-1-KO cells. However, these proteins did restore the normal F-actin network when a hydrophobic residue was introduced at the corresponding position. Munc18-1-KO MCCs expressing MUNC18-1(V263T) showed normal vesicle docking and exocytosis. These results demonstrate that MUNC18-1 regulates the F-actin network independently of syntaxin1 targeting via hydrophobicity in β-sheet 10. The abnormally dense F-actin network in Munc18-1-deficient cells is not a rate-limiting barrier in secretory vesicle docking or fusion.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Maria Pons-Vizcarra
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, de Boelelaan 1085, Amsterdam 1081 HV, The Netherlands
| | - Julia Kurps
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, de Boelelaan 1085, Amsterdam 1081 HV, The Netherlands
| | - Bassam Tawfik
- Neurosecretion group, Signaling Laboratory, Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Jakob B Sørensen
- Neurosecretion group, Signaling Laboratory, Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Jan R T van Weering
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Amsterdam UMC, location VUmc, de Boelelaan 1085, Amsterdam 1081 HV, The Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, de Boelelaan 1085, Amsterdam 1081 HV, The Netherlands .,Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Amsterdam UMC, location VUmc, de Boelelaan 1085, Amsterdam 1081 HV, The Netherlands
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103
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Protein Kinase C and Calmodulin Serve As Calcium Sensors for Calcium-Stimulated Endocytosis at Synapses. J Neurosci 2019; 39:9478-9490. [PMID: 31628181 DOI: 10.1523/jneurosci.0182-19.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 08/27/2019] [Accepted: 10/07/2019] [Indexed: 02/04/2023] Open
Abstract
Calcium influx triggers and facilitates endocytosis, which recycles vesicles and thus sustains synaptic transmission. Despite decades of studies, the underlying calcium sensor remained not well understood. Here, we examined two calcium binding proteins, protein kinase C (PKC) and calmodulin. Whether PKC is involved in endocytosis was unclear; whether calmodulin acts as a calcium sensor for endocytosis was neither clear, although calmodulin involvement in endocytosis had been suggested. We generated PKC (α or β-isoform) and calmodulin (calmodulin 2 gene) knock-out mice of either sex and measured endocytosis with capacitance measurements, pHluorin imaging and electron microscopy. We found that these knock-outs inhibited slow (∼10-30 s) and rapid (<∼3 s) endocytosis at large calyx-type calyces, and inhibited slow endocytosis and bulk endocytosis (forming large endosome-like structures) at small conventional hippocampal synapses, suggesting the involvement of PKC and calmodulin in three most common forms of endocytosis-the slow, rapid and bulk endocytosis. Inhibition of slow endocytosis in PKC or calmodulin 2 knock-out hippocampal synapses was rescued by overexpressing wild-type PKC or calmodulin, but not calcium-binding-deficient PKC or calmodulin mutant, respectively, suggesting that calcium stimulates endocytosis by binding with its calcium sensor PKC and calmodulin. PKC and calmodulin 2 knock-out inhibited calcium-dependent vesicle mobilization to the readily releasable pool, suggesting that PKC and calmodulin may mediate calcium-dependent facilitation of vesicle mobilization. These findings shed light on the molecular signaling link among calcium, endocytosis and vesicle mobilization that are crucial in maintaining synaptic transmission and neuronal network activity.SIGNIFICANCE STATEMENT Vesicle fusion releases neurotransmitters to mediate synaptic transmission. To sustain synaptic transmission, fused vesicles must be retrieved via endocytosis. Accumulating evidence suggests that calcium influx triggers synaptic vesicle endocytosis. However, how calcium triggers endocytosis is not well understood. Using genetic tools together with capacitance measurements, optical imaging and electron microscopy, we identified two calcium sensors, including protein kinase C (α and β isoforms) and calmodulin, for the most commonly observed forms of endocytosis: slow, rapid, and bulk. We also found that these two proteins are involved in calcium-dependent vesicle mobilization to the readily releasable pool. These results provide the molecular signaling link among calcium, endocytosis, and vesicle mobilization that are essential in sustaining synaptic transmission and neuronal network activity.
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104
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New observations in neuroscience using superresolution microscopy. J Neurosci 2019; 38:9459-9467. [PMID: 30381437 DOI: 10.1523/jneurosci.1678-18.2018] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 09/12/2018] [Accepted: 09/17/2018] [Indexed: 12/28/2022] Open
Abstract
Superresolution microscopy (SM) techniques are among the revolutionary methods for molecular and cellular observations in the 21st century. SM techniques overcome optical limitations, and several new observations using SM lead us to expect these techniques to have a large impact on neuroscience in the near future. Several types of SM have been developed, including structured illumination microscopy (SIM), stimulated emission depletion microscopy (STED), and photoactivated localization microscopy (PALM)/stochastic optical reconstruction microscopy (STORM), each with special features. In this Minisymposium, experts in these different types of SM discuss the new structural and functional information about specific important molecules in neuroscience that has been gained with SM. Using these techniques, we have revealed novel mechanisms of endocytosis in nerve growth, fusion pore dynamics, and described quantitative new properties of excitatory and inhibitory synapses. Additional powerful techniques, including single molecule-guided Bayesian localization SM (SIMBA) and expansion microscopy (ExM), alone or combined with super-resolution observation, are also introduced in this session.
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105
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Plasticity in exocytosis revealed through the effects of repetitive stimuli affect the content of nanometer vesicles and the fraction of transmitter released. Proc Natl Acad Sci U S A 2019; 116:21409-21415. [PMID: 31570594 DOI: 10.1073/pnas.1910859116] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Electrochemical techniques with disk and nano-tip electrodes, together with calcium imaging, were used to examine the effect of short-interval repetitive stimuli on both exocytosis and vesicular content in a model cell line. We show that the number of events decreases markedly with repeated stimuli suggesting a depletion of exocytosis machinery. However, repetitive stimuli induce a more stable fusion pore, leading to an increased amount of neurotransmitter release. In contrast, the total neurotransmitter content inside the vesicles decreases after repetitive stimuli, resulting in a higher average release fraction from each event. We suggest a possible mechanism regarding a link between activity-induced plasticity and fraction of release.
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106
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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107
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Ca 2+-independent but voltage-dependent quantal catecholamine secretion (CiVDS) in the mammalian sympathetic nervous system. Proc Natl Acad Sci U S A 2019; 116:20201-20209. [PMID: 31530723 DOI: 10.1073/pnas.1902444116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Action potential-induced vesicular exocytosis is considered exclusively Ca2+ dependent in Katz's Ca2+ hypothesis on synaptic transmission. This long-standing concept gets an exception following the discovery of Ca2+-independent but voltage-dependent secretion (CiVDS) and its molecular mechanisms in dorsal root ganglion sensory neurons. However, whether CiVDS presents only in sensory cells remains elusive. Here, by combining multiple independent recordings, we report that [1] CiVDS robustly presents in the sympathetic nervous system, including sympathetic superior cervical ganglion neurons and slice adrenal chromaffin cells, [2] uses voltage sensors of Ca2+ channels (N-type and novel L-type), and [3] contributes to catecholamine release in both homeostatic and fight-or-flight like states; [4] CiVDS-mediated catecholamine release is faster than that of Ca2+-dependent secretion at the quantal level and [5] increases Ca2+ currents and contractility of cardiac myocytes. Together, CiVDS presents in the sympathetic nervous system with potential physiological functions, including cardiac muscle contractility.
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108
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Abstract
Synaptic release of neuropeptides packaged in dense-core vesicles (DCVs) regulates synapses, circuits, and behaviors including feeding, sleeping, and pain perception. Here, synaptic DCV fusion pore openings are imaged without interference from cotransmitting small synaptic vesicles (SSVs) with the use of a fluorogen-activating protein (FAP). Activity-evoked kiss and run exocytosis opens synaptic DCV fusion pores away from active zones that readily conduct molecules larger than most native neuropeptides (i.e., molecular weight [MW] up to, at least, 4.5 kDa). Remarkably, these synaptic fusion pores also open spontaneously in the absence of stimulation and extracellular Ca2+ SNARE perturbations demonstrate different mechanisms for activity-evoked and spontaneous fusion pore openings with the latter sharing features of spontaneous small molecule transmitter release by active zone-associated SSVs. Fusion pore opening at resting synapses provides a mechanism for activity-independent peptidergic transmission.
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109
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Cong J, Fang B, Wang Q, Su Y, Gu T, Luo T. The mechanobiology of actin cytoskeletal proteins during cell-cell fusion. J R Soc Interface 2019; 16:20190022. [PMID: 31337301 DOI: 10.1098/rsif.2019.0022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Myosin II and spectrin β display mechanosensitive accumulations in invasive protrusions during cell-cell fusion of Drosophila myoblasts. The biochemical inhibition and deactivation of these proteins results in significant fusion defects. Yet, a quantitative understanding of how the protrusion geometry and fusion process are linked to these proteins is still lacking. Here we present a quantitative model to interpret the dependence of the protrusion size and the protrusive force on the mechanical properties and microstructures of the actin cytoskeleton and plasma membrane based on a mean-field theory. We build a quantitative linkage between mechanosensitive accumulation of myosin II and fusion pore formation at the tip of the invasive protrusion through local area dilation. The mechanical feedback loop between myosin II and local deformation suggests that myosin II accumulation possibly reduces the energy barrier and the critical radius of fusion pores. We also analyse the effect of spectrin β on maintaining the proper geometry of the protrusions required for the success of cell-cell fusion.
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Affiliation(s)
- Jing Cong
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
| | - Bing Fang
- College of Mechanical and Electronic Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002, People's Republic of China
| | - Qian Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
| | - Yan Su
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
| | - Tianqi Gu
- College of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, People's Republic of China
| | - Tianzhi Luo
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
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110
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Abstract
STimulated emission depletion (STED) nanoscopy has been proposed to extend greatly our capability of using light to study a variety of biological problems with nanometer-scale resolution. However, in practice the unwanted background noise degrades the STED image quality and precludes quantitative analysis. Here, we discuss the underlying sources of the background noise in STED images, and review current approaches to alleviate this problem, such as time-gating, anti-Stokes excitation removal, and off-focus incomplete depletion suppression. Progress in correcting uncorrelated background photons in fluorescence correlation spectroscopy combined with STED (STED-FCS) will also be discussed.
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Affiliation(s)
- Ye Ma
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States of America
| | - Taekjip Ha
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States of America.,Departments of Biophysics and Biophysical Chemistry, Biophysics, Johns Hopkins University, Baltimore, MD, United States of America.,Howard Hughes Medical Institute, Baltimore, MD, United States of America.,Author to whom any correspondence should be addressed
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111
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Ranjbari E, Majdi S, Ewing A. Analytical Techniques: Shedding Light upon Nanometer-Sized Secretory Vesicles. TRENDS IN CHEMISTRY 2019. [DOI: 10.1016/j.trechm.2019.02.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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112
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Taraska JW. A primer on resolving the nanoscale structure of the plasma membrane with light and electron microscopy. J Gen Physiol 2019; 151:974-985. [PMID: 31253697 PMCID: PMC6683668 DOI: 10.1085/jgp.201812227] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 06/10/2019] [Indexed: 12/20/2022] Open
Abstract
Taraska reviews the imaging methods that are being used to understand the structure of the plasma membrane at the molecular level. The plasma membrane separates a cell from its external environment. All materials and signals that enter or leave the cell must cross this hydrophobic barrier. Understanding the architecture and dynamics of the plasma membrane has been a central focus of general cellular physiology. Both light and electron microscopy have been fundamental in this endeavor and have been used to reveal the dense, complex, and dynamic nanoscale landscape of the plasma membrane. Here, I review classic and recent developments in the methods used to image and study the structure of the plasma membrane, particularly light, electron, and correlative microscopies. I will discuss their history and use for mapping the plasma membrane and focus on how these tools have provided a structural framework for understanding the membrane at the scale of molecules. Finally, I will describe how these studies provide a roadmap for determining the nanoscale architecture of other organelles and entire cells in order to bridge the gap between cellular form and function.
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Affiliation(s)
- Justin W Taraska
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
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113
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Chasing Uptake: Super-Resolution Microscopy in Endocytosis and Phagocytosis. Trends Cell Biol 2019; 29:727-739. [PMID: 31227311 DOI: 10.1016/j.tcb.2019.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/14/2019] [Accepted: 05/23/2019] [Indexed: 11/21/2022]
Abstract
Since their invention about two decades ago, super-resolution microscopes have become a method of choice in cell biology. Owing to a spatial resolution below 50 nm, smaller than the size of most organelles, and an order of magnitude better than the diffraction limit of conventional light microscopes, super-resolution microscopy is a powerful technique for resolving intracellular trafficking. In this review we discuss discoveries in endocytosis and phagocytosis that have been made possible by super-resolution microscopy - from uptake at the plasma membrane, endocytic coat formation, and cytoskeletal rearrangements to endosomal maturation. The detailed visualization of the diverse molecular assemblies that mediate endocytic uptake will provide a better understanding of how cells ingest extracellular material.
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114
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Karatekin E, Rothman JE. FEBS Letters Special Issue on Exocytosis and Endocytosis. FEBS Lett 2019; 592:3477-3479. [PMID: 30417372 DOI: 10.1002/1873-3468.13274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Erdem Karatekin
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.,Nanobiology Institute, Yale University, West Haven, CT, USA.,Centre National de la Recherche Scientifique (CNRS), Paris, France
| | - James E Rothman
- Nanobiology Institute, Yale University, West Haven, CT, USA.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, UK
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115
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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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116
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Majdi S, Larsson A, Najafinobar N, Borges R, Ewing AG. Extracellular ATP Regulates the Vesicular Pore Opening in Chromaffin Cells and Increases the Fraction Released During Individual Exocytosis Events. ACS Chem Neurosci 2019; 10:2459-2466. [PMID: 30892011 DOI: 10.1021/acschemneuro.8b00722] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adenosine triphosphate (ATP) is the main energy source for cellular metabolism. Besides that, ATP is a neurotransmitter and a cotransmitter that acts on purinergic receptors present either pre- or postsynaptically. Almost all types of secretory vesicles from any neuron or animal species contain high concentrations of ATP, being an essential factor in the accumulation of neurotransmitters. In this work, we studied the effects of ATP on quantum catecholamine release and vesicular storage in chromaffin cells. We combined three electrochemical methods: conventional amperometry with intracellular vesicle impact electrochemical cytometry and vesicle impact electrochemical cytometry. We found that extracellular ATP increased the released quantal fraction of catecholamine but not its vesicular content. Studying the dynamics of exocytosis events in ATP treated cells showed that ATP affects the release fusion pore. To elucidate the mechanisms of the observed ATP effects, cells and vesicles were pharmacologically treated with suramin (a purinergic blocker) and ARL-67156 (an antagonist of ecto-ATPases). The data indicate that the catecholamine content of vesicles increased compared to control after these drugs. Our data suggest that ATP acting on purinergic receptors increases the quantum releasable size through an increased fusion pore opening and that ARL-67156 and/or suramin protect the vesicle from neurotransmitter leakage by functioning as competitive inhibitors to ATP.
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Affiliation(s)
- Soodabeh Majdi
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 41296 Gothenburg, Sweden
| | - Anna Larsson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 41296 Gothenburg, Sweden
| | - Neda Najafinobar
- Medicinal Chemistry, Respiratory, Inflammation and Autoimmunity, IMED Biotech Unit, AstraZeneca, 43150 Gothenburg, Sweden
| | - Ricardo Borges
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, 38200 Laguna, Tenerife, Spain
| | - Andrew G. Ewing
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 41296 Gothenburg, Sweden
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117
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Qin X, Tsien RW, Park H. Real-time three-dimensional tracking of single synaptic vesicles reveals that synaptic vesicles undergoing kiss-and-run fusion remain close to their original fusion site before reuse. Biochem Biophys Res Commun 2019; 514:1004-1008. [PMID: 31092326 DOI: 10.1016/j.bbrc.2019.05.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 05/04/2019] [Indexed: 01/10/2023]
Abstract
The release of neurotransmitters via the fusion between synaptic vesicles and the presynaptic membrane is an essential step in synaptic transmission. Synaptic vesicles generally undergo two distinct modes of exocytosis called full-collapse fusion and kiss-and-run fusion. In kiss-and-run fusion, the fusion pore of the synaptic vesicle opens transiently without the vesicle collapsing fully into the plasma membrane; thus, each synaptic vesicle can be used multiple times to release neurotransmitters. Despite considerable research, the detailed mechanisms that underlie kiss-and-run fusion remain elusive, particularly the location of synaptic vesicles after kiss-and-run events. To address this question, we performed real-time three-dimensional tracking of single synaptic vesicles labeled with a single quantum dot in the presynaptic terminal of cultured hippocampal neurons and analyzed the three-dimensional trajectories of these vesicles undergoing kiss-and-run fusion. We found that the majority of these synaptic vesicles underwent another exocytosis event within 120 nm of their original fusion site and underwent a second exocytosis event within 10 s of the first fusion event. These results indicate that after kiss-and-run fusion, synaptic vesicles remain relatively close to their original fusion site and can release repeatedly at brief intervals, allowing neurons to maintain neurotransmitter release during bursting activity.
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Affiliation(s)
- Xianan Qin
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Richard W Tsien
- NYU Neuroscience Institute and Department of Physiology and Neuroscience, New York University, New York, NY, 10016, USA
| | - Hyokeun Park
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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118
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Ali T, Bednarska J, Vassilopoulos S, Tran M, Diakonov IA, Ziyadeh-Isleem A, Guicheney P, Gorelik J, Korchev YE, Reilly MM, Bitoun M, Shevchuk A. Correlative SICM-FCM reveals changes in morphology and kinetics of endocytic pits induced by disease-associated mutations in dynamin. FASEB J 2019; 33:8504-8518. [PMID: 31017801 PMCID: PMC6593877 DOI: 10.1096/fj.201802635r] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Dynamin 2 (DNM2) is a GTP-binding protein that controls endocytic vesicle scission and defines a whole class of dynamin-dependent endocytosis, including clathrin-mediated endocytosis by caveoli. It has been suggested that mutations in the DNM2 gene, associated with 3 inherited diseases, disrupt endocytosis. However, how exactly mutations affect the nanoscale morphology of endocytic machinery has never been studied. In this paper, we used live correlative scanning ion conductance microscopy (SICM) and fluorescence confocal microscopy (FCM) to study how disease-associated mutations affect the morphology and kinetics of clathrin-coated pits (CCPs) by directly following their dynamics of formation, maturation, and internalization in skin fibroblasts from patients with centronuclear myopathy (CNM) and in Cos-7 cells expressing corresponding dynamin mutants. Using SICM-FCM, which we have developed, we show how p.R465W mutation disrupts pit structure, preventing its maturation and internalization, and significantly increases the lifetime of CCPs. Differently, p.R522H slows down the formation of CCPs without affecting their internalization. We also found that CNM mutations in DNM2 affect the distribution of caveoli and reduce dorsal ruffling in human skin fibroblasts. Collectively, our SICM-FCM findings at single CCP level, backed up by electron microscopy data, argue for the impairment of several forms of endocytosis in DNM2-linked CNM.-Ali, T., Bednarska, J., Vassilopoulos, S., Tran, M., Diakonov, I. A., Ziyadeh-Isleem, A., Guicheney, P., Gorelik, J., Korchev, Y. E., Reilly, M. M., Bitoun, M., Shevchuk, A. Correlative SICM-FCM reveals changes in morphology and kinetics of endocytic pits induced by disease-associated mutations in dynamin.
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Affiliation(s)
- Tayyibah Ali
- Division of Experimental Medicine, Department of Medicine, Imperial College London, London, United Kingdom
| | - Joanna Bednarska
- Division of Experimental Medicine, Department of Medicine, Imperial College London, London, United Kingdom
| | - Stéphane Vassilopoulos
- Research Center for Myology, Institut de Myologie, UMRS 974, INSERM, Sorbonne Université, Paris, France
| | - Martin Tran
- Division of Experimental Medicine, Department of Medicine, Imperial College London, London, United Kingdom
| | - Ivan A Diakonov
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Azza Ziyadeh-Isleem
- UMRS 1166, INSERM, Institute of Cardiometabolism and Nutrition (ICAN), Paris, France.,UMRS 1166, Sorbonne Universités-Pierre and Marie Curie University (UPMC), Paris, France
| | - Pascale Guicheney
- UMRS 1166, INSERM, Institute of Cardiometabolism and Nutrition (ICAN), Paris, France.,UMRS 1166, Sorbonne Universités-Pierre and Marie Curie University (UPMC), Paris, France
| | - Julia Gorelik
- Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Yuri E Korchev
- Division of Experimental Medicine, Department of Medicine, Imperial College London, London, United Kingdom
| | - Mary M Reilly
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, Queen Square London, United Kingdom
| | - Marc Bitoun
- Research Center for Myology, Institut de Myologie, UMRS 974, INSERM, Sorbonne Université, Paris, France
| | - Andrew Shevchuk
- Division of Experimental Medicine, Department of Medicine, Imperial College London, London, United Kingdom
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119
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Zhu W, Gu C, Dunevall J, Ren L, Zhou X, Ewing AG. Combined Amperometry and Electrochemical Cytometry Reveal Differential Effects of Cocaine and Methylphenidate on Exocytosis and the Fraction of Chemical Release. Angew Chem Int Ed Engl 2019; 58:4238-4242. [PMID: 30688389 PMCID: PMC6519382 DOI: 10.1002/anie.201813717] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 01/08/2019] [Indexed: 11/18/2022]
Abstract
Amperometry with nanotip electrodes has been applied to show cocaine and methylphenidate not only trigger declines in vesicle content and exocytotic catecholamine release in a model cell line but also differentially change the fraction of transmitter released from each individual vesicle. In addition, cocaine accelerates exocytotic release dynamics while they remain unchanged after methylphenidate treatment. The parameters from pre-spike feet for the two drugs are also in opposition, suggesting this aspect of release is affected differentially. As cocaine and methylphenidate are psychostimulants with similar pharmacologic action but have opposite effects on cognition, these results might provide a missing link between the regulation of exocytosis and vesicles and the effect of this regulation on cognition, learning, and memory. A speculative chemical mechanism of the effect of these drugs on vesicle content and exocytosis is presented.
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Affiliation(s)
- Wanying Zhu
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemivägen 1041296GothenburgSweden
- School of PharmacyNanjing Medical UniversityLongmian Avenue 101Nanjing210029China
| | - Chaoyi Gu
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemivägen 1041296GothenburgSweden
| | - Johan Dunevall
- Department of Chemistry and Chemical EngineeringChalmers University of TechnologyKemivägen 1041296GothenburgSweden
| | - Lin Ren
- Department of Chemistry and Chemical EngineeringChalmers University of TechnologyKemivägen 1041296GothenburgSweden
| | - Xuemin Zhou
- School of PharmacyNanjing Medical UniversityLongmian Avenue 101Nanjing210029China
| | - Andrew G. Ewing
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemivägen 1041296GothenburgSweden
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120
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Jimah JR, Hinshaw JE. Structural Insights into the Mechanism of Dynamin Superfamily Proteins. Trends Cell Biol 2019; 29:257-273. [DOI: 10.1016/j.tcb.2018.11.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 10/30/2018] [Accepted: 11/02/2018] [Indexed: 12/28/2022]
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121
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Fezoua-Boubegtiten Z, Hastoy B, Scotti P, Milochau A, Bathany K, Desbat B, Castano S, Oda R, Lang J. The transmembrane domain of the SNARE protein VAMP2 is highly sensitive to its lipid environment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:670-676. [DOI: 10.1016/j.bbamem.2018.12.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/15/2018] [Accepted: 12/17/2018] [Indexed: 12/12/2022]
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122
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Zhu W, Gu C, Dunevall J, Ren L, Zhou X, Ewing AG. Combined Amperometry and Electrochemical Cytometry Reveal Differential Effects of Cocaine and Methylphenidate on Exocytosis and the Fraction of Chemical Release. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201813717] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Wanying Zhu
- Department of Chemistry and Molecular BiologyUniversity of Gothenburg Kemivägen 10 41296 Gothenburg Sweden
- School of PharmacyNanjing Medical University Longmian Avenue 101 Nanjing 210029 China
| | - Chaoyi Gu
- Department of Chemistry and Molecular BiologyUniversity of Gothenburg Kemivägen 10 41296 Gothenburg Sweden
| | - Johan Dunevall
- Department of Chemistry and Chemical EngineeringChalmers University of Technology Kemivägen 10 41296 Gothenburg Sweden
| | - Lin Ren
- Department of Chemistry and Chemical EngineeringChalmers University of Technology Kemivägen 10 41296 Gothenburg Sweden
| | - Xuemin Zhou
- School of PharmacyNanjing Medical University Longmian Avenue 101 Nanjing 210029 China
| | - Andrew G. Ewing
- Department of Chemistry and Molecular BiologyUniversity of Gothenburg Kemivägen 10 41296 Gothenburg Sweden
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123
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Eyring KW, Tsien RW. Direct Visualization of Wide Fusion-Fission Pores and Their Highly Varied Dynamics. Cell 2019; 173:819-821. [PMID: 29727670 DOI: 10.1016/j.cell.2018.04.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In this issue of Cell, Shin et al. report the first live-cell imaging of a fusion pore. Directly visualized pores in neuroendocrine cells can be much larger than expected yet not require vesicular full-collapse. These fusion-fission pores have diverse fates arising from opposing dynamin-driven pore constriction and F-actin-mediated pore expansion.
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Affiliation(s)
- Katherine W Eyring
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University, New York, NY 10016, USA
| | - Richard W Tsien
- Department of Neuroscience and Physiology, Neuroscience Institute, New York University, New York, NY 10016, USA.
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124
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Shi Z, Graber ZT, Baumgart T, Stone HA, Cohen AE. Cell Membranes Resist Flow. Cell 2018; 175:1769-1779.e13. [PMID: 30392960 PMCID: PMC6541487 DOI: 10.1016/j.cell.2018.09.054] [Citation(s) in RCA: 203] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 07/16/2018] [Accepted: 09/26/2018] [Indexed: 02/06/2023]
Abstract
The fluid-mosaic model posits a liquid-like plasma membrane, which can flow in response to tension gradients. It is widely assumed that membrane flow transmits local changes in membrane tension across the cell in milliseconds, mediating long-range signaling. Here, we show that propagation of membrane tension occurs quickly in cell-attached blebs but is largely suppressed in intact cells. The failure of tension to propagate in cells is explained by a fluid dynamical model that incorporates the flow resistance from cytoskeleton-bound transmembrane proteins. Perturbations to tension propagate diffusively, with a diffusion coefficient Dσ ∼0.024 μm2/s in HeLa cells. In primary endothelial cells, local increases in membrane tension lead only to local activation of mechanosensitive ion channels and to local vesicle fusion. Thus, membrane tension is not a mediator of long-range intracellular signaling, but local variations in tension mediate distinct processes in sub-cellular domains.
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Affiliation(s)
- Zheng Shi
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute
| | - Zachary T Graber
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Tobias Baumgart
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Adam E Cohen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute.
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125
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Abbineni PS, Bittner MA, Axelrod D, Holz RW. Chromogranin A, the major lumenal protein in chromaffin granules, controls fusion pore expansion. J Gen Physiol 2018; 151:118-130. [PMID: 30504267 PMCID: PMC6363410 DOI: 10.1085/jgp.201812182] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 11/07/2018] [Indexed: 01/03/2023] Open
Abstract
Upon fusion of the secretory granule with the plasma membrane, small molecules are discharged through the immediately formed narrow fusion pore, but protein discharge awaits pore expansion. Recently, fusion pore expansion was found to be regulated by tissue plasminogen activator (tPA), a protein present within the lumen of chromaffin granules in a subpopulation of chromaffin cells. Here, we further examined the influence of other lumenal proteins on fusion pore expansion, especially chromogranin A (CgA), the major and ubiquitous lumenal protein in chromaffin granules. Polarized TIRF microscopy demonstrated that the fusion pore curvature of granules containing CgA-EGFP was long lived, with curvature lifetimes comparable to those of tPA-EGFP-containing granules. This was surprising because fusion pore curvature durations of granules containing exogenous neuropeptide Y-EGFP (NPY-EGFP) are significantly shorter (80% lasting <1 s) than those containing CgA-EGFP, despite the anticipated expression of endogenous CgA. However, quantitative immunocytochemistry revealed that transiently expressed lumenal proteins, including NPY-EGFP, caused a down-regulation of endogenously expressed proteins, including CgA. Fusion pore curvature durations in nontransfected cells were significantly longer than those of granules containing overexpressed NPY but shorter than those associated with granules containing overexpressed tPA, CgA, or chromogranin B. Introduction of CgA to NPY-EGFP granules by coexpression converted the fusion pore from being transient to being longer lived, comparable to that found in nontransfected cells. These findings demonstrate that several endogenous chromaffin granule lumenal proteins are regulators of fusion pore expansion and that alteration of chromaffin granule contents affects fusion pore lifetimes. Importantly, the results indicate a new role for CgA. In addition to functioning as a prohormone, CgA plays an important role in controlling fusion pore expansion.
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Affiliation(s)
| | - Mary A Bittner
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Daniel Axelrod
- Department of Pharmacology, University of Michigan, Ann Arbor, MI.,Department of Physics, LSA Biophysics, University of Michigan, Ann Arbor, MI
| | - Ronald W Holz
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
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126
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Tse A, Lee AK, Takahashi N, Gong A, Kasai H, Tse FW. Strong stimulation triggers full fusion exocytosis and very slow endocytosis of the small dense core granules in carotid glomus cells. J Neurogenet 2018; 32:267-278. [PMID: 30484390 DOI: 10.1080/01677063.2018.1497629] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Chemosensory glomus cells of the carotid bodies release transmitters, including ATP and dopamine mainly via the exocytosis of small dense core granules (SDCGs, vesicular diameter of ∼100 nm). Using carbon-fiber amperometry, we showed previously that with a modest uniform elevation in cytosolic Ca2+ concentration ([Ca2+]i of ∼0.5 µM), SDCGs of rat glomus cells predominantly underwent a "kiss-and-run" mode of exocytosis. Here, we examined whether a larger [Ca2+]i rise influenced the mode of exocytosis. Activation of voltage-gated Ca2+ channels by a train of voltage-clamped depolarizations which elevated [Ca2+]i to ∼1.6 μM increased the cell membrane capacitance by ∼2.5%. At 30 s after such a stimulus, only 5% of the added membrane was retrieved. Flash photolysis of caged-Ca2+ (which elevated [Ca2+]i to ∼16 μM) increased cell membrane capacitance by ∼13%, and only ∼30% of the added membrane was retrieved at 30 s after the UV flash. When exocytosis and endocytosis were monitored using the two-photon excitation and extracellular polar tracer (TEP) imaging of FM1-43 fluorescence in conjunction with photolysis of caged Ca2+, almost uniform exocytosis was detected over the cell's entire surface and it was followed by slow endocytosis. Immunocytochemistry showed that the cytoplasmic densities of dynamin I, II and clathrin (key proteins that mediate endocytosis) in glomus cells were less than half of those in adrenal chromaffin cells, suggesting that a lower expression of endocytotic machinery may underlie the slow endocytosis in glomus cells. An analysis of the relative change in the signals from two fluorescent dyes that simultaneously monitored the addition of vesicular volume and plasma membrane surface area, suggested that with an intense stimulus, SDCGs of glomus cells underwent full fusion without any significant "compound" exocytosis. Therefore, during a severe hypoxic challenge, glomus granules undergo full fusion for a more complete release of transmitters.
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Affiliation(s)
- Amy Tse
- a Department of Pharmacology and Neuroscience and Metal Health Institute , University of Alberta , Edmonton , Canada
| | - Andy K Lee
- a Department of Pharmacology and Neuroscience and Metal Health Institute , University of Alberta , Edmonton , Canada
| | - Noriko Takahashi
- b Department of Physiology , Kitasato University School of Medicine , Sagamihara , Japan
| | - Alex Gong
- a Department of Pharmacology and Neuroscience and Metal Health Institute , University of Alberta , Edmonton , Canada
| | - Haruo Kasai
- c Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine , The University of Tokyo , Bunkyo-ku , Japan.,d International Research Center for Neurointelligence (WPI-IRCN), UTIAS, The University of Tokyo , Bunkyo-ku , Japan
| | - Frederick W Tse
- a Department of Pharmacology and Neuroscience and Metal Health Institute , University of Alberta , Edmonton , Canada
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127
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Abbineni PS, Axelrod D, Holz RW. Visualization of expanding fusion pores in secretory cells. J Gen Physiol 2018; 150:1640-1646. [PMID: 30470717 PMCID: PMC6279363 DOI: 10.1085/jgp.201812186] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/06/2018] [Indexed: 11/20/2022] Open
Abstract
Abbineni et al. examine recent imaging work on fusion pores and discuss the dynamics of PI-4,5-P2 accumulation on granule membranes.
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Affiliation(s)
- Prabhodh S Abbineni
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI
| | - Daniel Axelrod
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI .,Department of Physics and LSA Biophysics, University of Michigan Medical School, Ann Arbor, MI
| | - Ronald W Holz
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI
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128
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Karatekin E. Toward a unified picture of the exocytotic fusion pore. FEBS Lett 2018; 592:3563-3585. [PMID: 30317539 PMCID: PMC6353554 DOI: 10.1002/1873-3468.13270] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 09/30/2018] [Accepted: 10/10/2018] [Indexed: 11/07/2022]
Abstract
Neurotransmitter and hormone release involve calcium-triggered fusion of a cargo-loaded vesicle with the plasma membrane. The initial connection between the fusing membranes, called the fusion pore, can evolve in various ways, including rapid dilation to allow full cargo release, slow expansion, repeated opening-closing and resealing. Pore dynamics determine the kinetics of cargo release and the mode of vesicle recycling, but how these processes are controlled is poorly understood. Previous reconstitutions could not monitor single pores, limiting mechanistic insight they could provide. Recently developed nanodisc-based fusion assays allow reconstitution and monitoring of single pores with unprecedented detail and hold great promise for future discoveries. They recapitulate various aspects of exocytotic fusion pores, but comparison is difficult because different approaches suggested very different exocytotic fusion pore properties, even for the same cell type. In this Review, I discuss how most of the data can be reconciled, by recognizing how different methods probe different aspects of the same fusion process. The resulting picture is that fusion pores have broadly distributed properties arising from stochastic processes which can be modulated by physical constraints imposed by proteins, lipids and membranes.
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Affiliation(s)
- Erdem Karatekin
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
- Centre National de la Recherche Scientifique (CNRS), Paris, France
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129
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Chanaday NL, Kavalali ET. Time course and temperature dependence of synaptic vesicle endocytosis. FEBS Lett 2018; 592:3606-3614. [DOI: 10.1002/1873-3468.13268] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 10/02/2018] [Accepted: 10/06/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Natali L. Chanaday
- Department of Pharmacology; Vanderbilt Brain Institute; Vanderbilt University; Nashville TN USA
| | - Ege T. Kavalali
- Department of Pharmacology; Vanderbilt Brain Institute; Vanderbilt University; Nashville TN USA
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130
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Wijesooriya CS, Nyamekye CKA, Smith EA. Optical Imaging of the Nanoscale Structure and Dynamics of Biological Membranes. Anal Chem 2018; 91:425-440. [DOI: 10.1021/acs.analchem.8b04755] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
| | - Charles K. A. Nyamekye
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
- The Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States
| | - Emily A. Smith
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
- The Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States
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131
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Söllner TH, Malsam J. Uncovering the "secret" lives of vacuolar fusion pores in living cells. EMBO J 2018; 37:embj.2018100656. [PMID: 30237311 DOI: 10.15252/embj.2018100656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
| | - Jörg Malsam
- Heidelberg University Biochemistry Center, Heidelberg, Germany
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132
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Álvarez de Toledo G, Montes MÁ, Montenegro P, Borges R. Phases of the exocytotic fusion pore. FEBS Lett 2018; 592:3532-3541. [PMID: 30169901 DOI: 10.1002/1873-3468.13234] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 08/25/2018] [Accepted: 08/28/2018] [Indexed: 01/19/2023]
Abstract
Membrane fusion and fission are fundamental processes in living organisms. Membrane fusion occurs through the formation of a fusion pore, which is the structure that connects two lipid membranes during their fusion. Fusion pores can form spontaneously, but cells endow themselves with a set of proteins that make the process of fusion faster and regulatable. The fusion pore starts with a narrow diameter and dilates relatively slowly; it may fluctuate in size or can even close completely, producing a transient vesicle fusion (kiss-and-run), or can finally expand abruptly to release all vesicle contents. A set of proteins control the formation, dilation, and eventual closure of the fusion pore and, therefore, the velocity at which the contents of secretory vesicles are released to the extracellular medium. Thus, the regulation of fusion pore expansion or closure is key to regulate the release of neurotransmitters and hormones. Here, we review the phases of the fusion pore and discuss the implications in the modes of exocytosis.
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Affiliation(s)
| | - María Ángeles Montes
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain
| | - Pablo Montenegro
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, Spain
| | - Ricardo Borges
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, Spain
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133
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Thuringer D, Chanteloup G, Winckler P, Garrido C. The vesicular transfer of CLIC1 from glioblastoma to microvascular endothelial cells requires TRPM7. Oncotarget 2018; 9:33302-33311. [PMID: 30279961 PMCID: PMC6161795 DOI: 10.18632/oncotarget.26048] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 08/16/2018] [Indexed: 01/01/2023] Open
Abstract
Chloride intracellular channel 1 (CLIC1) is highly expressed and secreted by human glioblastoma cells and cell lines such as U87, initiating cell migration and tumor growth. Here, we examined whether CLIC1 could be transferred to human primary microvascular endothelial cells (HMEC). We previously reported that the oncogenic microRNA, miR-5096, increased the release of extracellular vesicles (EVs) by which it increased its own transfer from U87 to surrounding cells. Thus, we also examined its effect on the CLIC1 transfer. In homotypic cultures, miR-5096 did not increase the expression of CLIC1 in U87 nor in HMEC. However, the endothelial CLIC1 level increased after exposure to EVs released by U87, and even more by miR-5096-loaded U87. The EVs-transferred CLIC1 was active in HMEC, promoting endothelial sprouting in matrigel. Cell exposure to EVs induced cytosolic Ca2+ spikes which were dependent on the transient receptor potential melastatin member 7 (TRPM7). TRPM7 silencing prevented Ca2+ spikes and the subsequent CLIC1 delivery into HMEC. Our data suggest that the vesicular transfer of CLIC1 between cells requires TRMP7 expression in recipient endothelial cells. How the vesicular transfer of CLIC1 is modulated in cancer therapy is a future challenge.
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Affiliation(s)
- Dominique Thuringer
- INSERM U1231, Laboratory of Excellence Ligue Nationale contre le Cancer, 21000 Dijon, France.,Université de Bourgogne Franche Comté, 21000 Dijon, France
| | - Gaetan Chanteloup
- INSERM U1231, Laboratory of Excellence Ligue Nationale contre le Cancer, 21000 Dijon, France.,Université de Bourgogne Franche Comté, 21000 Dijon, France
| | - Pascale Winckler
- AgroSup Dijon, PAM UMR, DImaCell Imaging Facility, Université de Bourgogne Franche Comté, 21000 Dijon, France
| | - Carmen Garrido
- INSERM U1231, Laboratory of Excellence Ligue Nationale contre le Cancer, 21000 Dijon, France.,Université de Bourgogne Franche Comté, 21000 Dijon, France.,Centre Georges François Leclerc (CGFL), 21000 Dijon, France
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134
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Actin Remodeling in Regulated Exocytosis: Toward a Mesoscopic View. Trends Cell Biol 2018; 28:685-697. [DOI: 10.1016/j.tcb.2018.04.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/05/2018] [Accepted: 04/13/2018] [Indexed: 01/10/2023]
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135
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D'Agostino M, Risselada HJ, Endter LJ, Comte-Miserez V, Mayer A. SNARE-mediated membrane fusion arrests at pore expansion to regulate the volume of an organelle. EMBO J 2018; 37:embj.201899193. [PMID: 30120144 DOI: 10.15252/embj.201899193] [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: 02/07/2018] [Revised: 06/28/2018] [Accepted: 07/03/2018] [Indexed: 11/09/2022] Open
Abstract
Constitutive membrane fusion within eukaryotic cells is thought to be controlled at its initial steps, membrane tethering and SNARE complex assembly, and to rapidly proceed from there to full fusion. Although theory predicts that fusion pore expansion faces a major energy barrier and might hence be a rate-limiting and regulated step, corresponding states with non-expanding pores are difficult to assay and have remained elusive. Here, we show that vacuoles in living yeast are connected by a metastable, non-expanding, nanoscopic fusion pore. This is their default state, from which full fusion is regulated. Molecular dynamics simulations suggest that SNAREs and the SM protein-containing HOPS complex stabilize this pore against re-closure. Expansion of the nanoscopic pore to full fusion can thus be triggered by osmotic pressure gradients, providing a simple mechanism to rapidly adapt organelle volume to increases in its content. Metastable, nanoscopic fusion pores are then not only a transient intermediate but can be a long-lived, physiologically relevant and regulated state of SNARE-dependent membrane fusion.
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Affiliation(s)
- Massimo D'Agostino
- Département de Biochimie, Université de Lausanne, Epalinges, Switzerland
| | - Herre Jelger Risselada
- Department of Theoretical Physics, Georg-August University, Göttingen, Germany.,Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Laura J Endter
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | | | - Andreas Mayer
- Département de Biochimie, Université de Lausanne, Epalinges, Switzerland
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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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137
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Sharma S, Lindau M. The fusion pore, 60 years after the first cartoon. FEBS Lett 2018; 592:3542-3562. [PMID: 29904915 DOI: 10.1002/1873-3468.13160] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/07/2018] [Accepted: 06/12/2018] [Indexed: 11/10/2022]
Abstract
Neurotransmitter release occurs in the form of quantal events by fusion of secretory vesicles with the plasma membrane, and begins with the formation of a fusion pore that has a conductance similar to that of a large ion channel or gap junction. In this review, we propose mechanisms of fusion pore formation and discuss their implications for fusion pore structure and function. Accumulating evidence indicates a direct role of soluble N-ethylmaleimide-sensitive-factor attachment receptor proteins in the opening of fusion pores. Fusion pores are likely neither protein channels nor purely lipid, but are of proteolipidic composition. Future perspectives to gain better insight into the molecular structure of fusion pores are discussed.
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Affiliation(s)
- Satyan Sharma
- Laboratory for Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Manfred Lindau
- Laboratory for Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.,School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
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