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Phosphatidylinositol-4,5-Biphosphate (PI(4,5)P 2) Is Required for Rapid Endocytosis in Chromaffin Cells. BIOMED RESEARCH INTERNATIONAL 2020; 2020:9692503. [PMID: 32964048 PMCID: PMC7501565 DOI: 10.1155/2020/9692503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 08/17/2020] [Indexed: 12/27/2022]
Abstract
Objective Phosphoinositides play a regulatory role in clathrin-mediated endocytosis. However, their involvement in clathrin-independent endocytosis termed rapid endocytosis (RE), which is the mode of vesicle recycling during neurotransmitter release by transient fusion (known as kiss-and-run), has not been investigated. Here, we used patch-clamp recording of whole-cell membrane capacitance in adrenal chromaffin cells (ACC) to monitor changes of RE kinetics in response to pharmacological alteration of phosphatidylinositol-4,5-biphosphate (PI(4,5)P2) level by phenylarsine oxide (PAO) or antibody against phosphatidylinositol 4-kinase (AbPI4K). Results We found that PAO and AbPI4K significantly abrogated RE kinetics. Infusion of PI(4,5)P2 through the patch pipette potentiated RE kinetics and reversed PAO- and AbPI4K-induced blockade of RE. Similarly, the application of the bifunctional thiol dithiothreitol (DTT) to PAO-treated cells completely prevented the inhibitory effect of PAO on RE. These findings indicate that PI(4,5)P2 is implicated in the signaling (mechanistic) process of RE in ACC.
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2
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Lou X. Sensing Exocytosis and Triggering Endocytosis at Synapses: Synaptic Vesicle Exocytosis-Endocytosis Coupling. Front Cell Neurosci 2018; 12:66. [PMID: 29593500 PMCID: PMC5861208 DOI: 10.3389/fncel.2018.00066] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/26/2018] [Indexed: 12/29/2022] Open
Abstract
The intact synaptic structure is critical for information processing in neural circuits. During synaptic transmission, rapid vesicle exocytosis increases the size of never terminals and endocytosis counteracts the increase. Accumulating evidence suggests that SV exocytosis and endocytosis are tightly connected in time and space during SV recycling, and this process is essential for synaptic function and structural stability. Research in the past has illustrated the molecular details of synaptic vesicle (SV) exocytosis and endocytosis; however, the mechanisms that timely connect these two fundamental events are poorly understood at central synapses. Here we discuss recent progress in SV recycling and summarize several emerging mechanisms by which synapses can “sense” the occurrence of exocytosis and timely initiate compensatory endocytosis. They include Ca2+ sensing, SV proteins sensing, and local membrane stress sensing. In addition, the spatial organization of endocytic zones adjacent to active zones provides a structural basis for efficient coupling between SV exocytosis and endocytosis. Through linking different endocytosis pathways with SV fusion, these mechanisms ensure necessary plasticity and robustness of nerve terminals to meet diverse physiological needs.
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Affiliation(s)
- Xuelin Lou
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
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3
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Myers MD, Ryazantsev S, Hicke L, Payne GS. Calmodulin Promotes N-BAR Domain-Mediated Membrane Constriction and Endocytosis. Dev Cell 2016; 37:162-73. [PMID: 27093085 DOI: 10.1016/j.devcel.2016.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 02/15/2016] [Accepted: 03/16/2016] [Indexed: 10/21/2022]
Abstract
Membrane remodeling by BAR (Bin, Amphiphysin, RVS) domain-containing proteins, such as endophilins and amphiphysins, is integral to the process of endocytosis. However, little is known about the regulation of endocytic BAR domain activity. We have identified an interaction between the yeast Rvs167 N-BAR domain and calmodulin. Calmodulin-binding mutants of Rvs167 exhibited defects in endocytic vesicle release. In vitro, calmodulin enhanced membrane tubulation and constriction by wild-type Rvs167 but not calmodulin-binding-defective mutants. A subset of mammalian N-BAR domains bound calmodulin, and co-expression of calmodulin with endophilin A2 potentiated tubulation in vivo. These studies reveal a conserved role for calmodulin in regulating the intrinsic membrane-sculpting activity of endocytic N-BAR domains.
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Affiliation(s)
- Margaret D Myers
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sergey Ryazantsev
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Linda Hicke
- Molecular Genetics and Microbiology, College of Natural Sciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Gregory S Payne
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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4
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Wen PJ, Grenklo S, Arpino G, Tan X, Liao HS, Heureaux J, Peng SY, Chiang HC, Hamid E, Zhao WD, Shin W, Näreoja T, Evergren E, Jin Y, Karlsson R, Ebert SN, Jin A, Liu AP, Shupliakov O, Wu LG. Actin dynamics provides membrane tension to merge fusing vesicles into the plasma membrane. Nat Commun 2016; 7:12604. [PMID: 27576662 PMCID: PMC5013665 DOI: 10.1038/ncomms12604] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 07/13/2016] [Indexed: 01/22/2023] Open
Abstract
Vesicle fusion is executed via formation of an Ω-shaped structure (Ω-profile), followed by closure (kiss-and-run) or merging of the Ω-profile into the plasma membrane (full fusion). Although Ω-profile closure limits release but recycles vesicles economically, Ω-profile merging facilitates release but couples to classical endocytosis for recycling. Despite its crucial role in determining exocytosis/endocytosis modes, how Ω-profile merging is mediated is poorly understood in endocrine cells and neurons containing small ∼30–300 nm vesicles. Here, using confocal and super-resolution STED imaging, force measurements, pharmacology and gene knockout, we show that dynamic assembly of filamentous actin, involving ATP hydrolysis, N-WASP and formin, mediates Ω-profile merging by providing sufficient plasma membrane tension to shrink the Ω-profile in neuroendocrine chromaffin cells containing ∼300 nm vesicles. Actin-directed compounds also induce Ω-profile accumulation at lamprey synaptic active zones, suggesting that actin may mediate Ω-profile merging at synapses. These results uncover molecular and biophysical mechanisms underlying Ω-profile merging. As vesicles fuse to the plasma membrane, they form intermediate Ω-shaped structures followed by either closure of the pore or full merging with the plasma membrane. Here Wen et al. show that dynamic actin assembly provides membrane tension to promote Ω merging in neuroendocrine cells and synapses.
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Affiliation(s)
- Peter J Wen
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Staffan Grenklo
- Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.,Department of Cell Biology, WGI, Stockholm University, 106 91 Stockholm, Sweden
| | - Gianvito Arpino
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.,Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Xinyu Tan
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Hsien-Shun Liao
- National Institute of Biomedical Imaging and Bioengineering (NIBIB), Bethesda, Maryland 20892, USA
| | - Johanna Heureaux
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Shi-Yong Peng
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Hsueh-Cheng Chiang
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Edaeni Hamid
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Wei-Dong Zhao
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Wonchul Shin
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Tuomas Näreoja
- Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Emma Evergren
- Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Yinghui Jin
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
| | - Roger Karlsson
- Department of Cell Biology, WGI, Stockholm University, 106 91 Stockholm, Sweden
| | - Steven N Ebert
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USA
| | - Albert Jin
- National Institute of Biomedical Imaging and Bioengineering (NIBIB), Bethesda, Maryland 20892, USA
| | - Allen P Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Oleg Shupliakov
- Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.,Institute of Translational Biomedicine, St. Petersburg State University, St. Petersburg 199034, Russia
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA
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5
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Li L, Wu X, Yue HY, Zhu YC, Xu J. Myosin light chain kinase facilitates endocytosis of synaptic vesicles at hippocampal boutons. J Neurochem 2016; 138:60-73. [PMID: 27062289 DOI: 10.1111/jnc.13635] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 03/27/2016] [Accepted: 04/05/2016] [Indexed: 02/07/2023]
Abstract
At nerve terminals, endocytosis efficiently recycles vesicle membrane to maintain synaptic transmission under different levels of neuronal activity. Ca(2+) and its downstream signal pathways are critical for the activity-dependent regulation of endocytosis. An activity- and Ca(2+) -dependent kinase, myosin light chain kinase (MLCK) has been reported to regulate vesicle mobilization, vesicle cycling, and motility in different synapses, but whether it has a general contribution to regulation of endocytosis at nerve terminals remains unknown. We investigated this issue at rat hippocampal boutons by imaging vesicle endocytosis as the real-time retrieval of vesicular synaptophysin tagged with a pH-sensitive green fluorescence protein. We found that endocytosis induced by 200 action potentials (5-40 Hz) was slowed by acute inhibition of MLCK and down-regulation of MLCK with RNA interference, while the total amount of vesicle exocytosis and somatic Ca(2+) channel current did not change with MLCK down-regulation. Acute inhibition of myosin II similarly impaired endocytosis. Furthermore, down-regulation of MLCK prevented depolarization-induced phosphorylation of myosin light chain, an effect shared by blockers of Ca(2+) channels and calmodulin. These results suggest that MLCK facilitates vesicle endocytosis through activity-dependent phosphorylation of myosin downstream of Ca(2+) /calmodulin, probably as a widely existing mechanism among synapses. Our study suggests that MLCK is an important activity-dependent regulator of vesicle recycling in hippocampal neurons, which are critical for learning and memory. The kinetics of vesicle membrane endocytosis at nerve terminals has long been known to depend on activity and Ca(2+) . This study provides evidence suggesting that myosin light chain kinase increases endocytosis efficiency at hippocampal neurons by mediating Ca(2+) /calmodulin-dependent phosphorylation of myosin. The authors propose that this signal cascade may serve as a common pathway contributing to the activity-dependent regulation of vesicle endocytosis at synapses.
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Affiliation(s)
- Lin Li
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta, Georgia, USA
| | - Xiaomei Wu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta, Georgia, USA.,Department of Neurochemistry, Institute of Nautical Medicine, Nantong University, Nantong, Jiangsu, China
| | - Hai-Yuan Yue
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta, Georgia, USA
| | - Yong-Chuan Zhu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta, Georgia, USA
| | - Jianhua Xu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta, Georgia, USA.,Department of Neurology, Medical College of Georgia, Augusta, Georgia, USA
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Wu XS, Zhang Z, Zhao WD, Wang D, Luo F, Wu LG. Calcineurin is universally involved in vesicle endocytosis at neuronal and nonneuronal secretory cells. Cell Rep 2014; 7:982-8. [PMID: 24835995 DOI: 10.1016/j.celrep.2014.04.020] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 03/05/2014] [Accepted: 04/11/2014] [Indexed: 01/28/2023] Open
Abstract
Calcium influx triggers and accelerates endocytosis in nerve terminals and nonneuronal secretory cells. Whether calcium/calmodulin-activated calcineurin, which dephosphorylates endocytic proteins, mediates this process is highly controversial for different cell types, developmental stages, and endocytic forms. Using three preparations that previously produced discrepant results (i.e., large calyx-type synapses, conventional cerebellar synapses, and neuroendocrine chromaffin cells containing large dense-core vesicles), we found that calcineurin gene knockout consistently slowed down endocytosis, regardless of cell type, developmental stage, or endocytic form (rapid or slow). In contrast, calcineurin and calmodulin blockers slowed down endocytosis at a relatively small calcium influx, but did not inhibit endocytosis at a large calcium influx, resulting in false-negative results. These results suggest that calcineurin is universally involved in endocytosis. They may also help explain the discrepancies among previous pharmacological studies. We therefore suggest that calcineurin should be included as a key player in mediating calcium-triggered and -accelerated vesicle endocytosis.
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Affiliation(s)
- Xin-Sheng Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Zhen Zhang
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Wei-Dong Zhao
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Dongsheng Wang
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Fujun Luo
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA.
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7
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Abstract
Neuronal activity triggers endocytosis at synaptic terminals to retrieve efficiently the exocytosed vesicle membrane, ensuring the membrane homeostasis of active zones and the continuous supply of releasable vesicles. The kinetics of endocytosis depends on Ca(2+) and calmodulin which, as a versatile signal pathway, can activate a broad spectrum of downstream targets, including myosin light chain kinase (MLCK). MLCK is known to regulate vesicle trafficking and synaptic transmission, but whether this kinase regulates vesicle endocytosis at synapses remains elusive. We investigated this issue at the rat calyx of Held synapse, where previous studies using whole-cell membrane capacitance measurement have characterized two common forms of Ca(2+)/calmodulin-dependent endocytosis, i.e., slow clathrin-dependent endocytosis and rapid endocytosis. Acute inhibition of MLCK with pharmacological agents was found to slow down the kinetics of both slow and rapid forms of endocytosis at calyces. Similar impairment of endocytosis occurred when blocking myosin II, a motor protein that can be phosphorylated upon MLCK activation. The inhibition of endocytosis was not accompanied by a change in Ca(2+) channel current. Combined inhibition of MLCK and calmodulin did not induce synergistic inhibition of endocytosis. Together, our results suggest that activation of MLCK accelerates both slow and rapid forms of vesicle endocytosis at nerve terminals, likely by functioning downstream of Ca(2+)/calmodulin.
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8
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Wu LG, Hamid E, Shin W, Chiang HC. Exocytosis and endocytosis: modes, functions, and coupling mechanisms. Annu Rev Physiol 2013; 76:301-31. [PMID: 24274740 DOI: 10.1146/annurev-physiol-021113-170305] [Citation(s) in RCA: 279] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Vesicle exocytosis releases content to mediate many biological events, including synaptic transmission essential for brain functions. Following exocytosis, endocytosis is initiated to retrieve exocytosed vesicles within seconds to minutes. Decades of studies in secretory cells reveal three exocytosis modes coupled to three endocytosis modes: (a) full-collapse fusion, in which vesicles collapse into the plasma membrane, followed by classical endocytosis involving membrane invagination and vesicle reformation; (b) kiss-and-run, in which the fusion pore opens and closes; and (c) compound exocytosis, which involves exocytosis of giant vesicles formed via vesicle-vesicle fusion, followed by bulk endocytosis that retrieves giant vesicles. Here we review these exo- and endocytosis modes and their roles in regulating quantal size and synaptic strength, generating synaptic plasticity, maintaining exocytosis, and clearing release sites for vesicle replenishment. Furthermore, we highlight recent progress in understanding how vesicle endocytosis is initiated and is thus coupled to exocytosis. The emerging model is that calcium influx via voltage-dependent calcium channels at the calcium microdomain triggers endocytosis and controls endocytosis rate; calmodulin and synaptotagmin are the calcium sensors; and the exocytosis machinery, including SNARE proteins (synaptobrevin, SNAP25, and syntaxin), is needed to coinitiate endocytosis, likely to control the amount of endocytosis.
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Affiliation(s)
- Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892; ,
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9
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Morgan JR, Comstra HS, Cohen M, Faundez V. Presynaptic membrane retrieval and endosome biology: defining molecularly heterogeneous synaptic vesicles. Cold Spring Harb Perspect Biol 2013; 5:a016915. [PMID: 24086045 DOI: 10.1101/cshperspect.a016915] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The release and uptake of neurotransmitters by synaptic vesicles is a tightly controlled process that occurs in response to diverse stimuli at morphologically disparate synapses. To meet these architectural and functional synaptic demands, it follows that there should be diversity in the mechanisms that control their secretion and retrieval and possibly in the composition of synaptic vesicles within the same terminal. Here we pay particular attention to areas where such diversity is generated, such as the variance in exocytosis/endocytosis coupling, SNAREs defining functionally diverse synaptic vesicle populations and the adaptor-dependent sorting machineries capable of generating vesicle diversity. We argue that there are various synaptic vesicle recycling pathways at any given synapse and discuss several lines of evidence that support the role of the endosome in synaptic vesicle recycling.
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Affiliation(s)
- Jennifer R Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
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10
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Abstract
Following synaptic vesicle exocytosis, neurons retrieve the fused membrane by a process of endocytosis to provide a supply of vesicles for subsequent release and maintain the presynaptic active zone. Rod and cone photoreceptors use a specialized structure called the synaptic ribbon that enables them to sustain high rates of neurotransmitter release. They must also employ mechanisms of synaptic vesicle endocytosis capable of keeping up with release. While much is known about endocytosis at another retinal ribbon synapse, that of the goldfish Mb1 bipolar cell, less is known about endocytosis in photoreceptors. We used capacitance recording techniques to measure vesicle membrane fusion and retrieval in photoreceptors from salamander retinal slices. We found that application of brief depolarizing steps (<100 ms) to cones evoked exocytosis followed by rapid endocytosis with a time constant ∼250 ms. In some cases, the capacitance trace overshot the baseline, indicating excess endocytosis. Calcium had no effect on the time constant, but enhanced excess endocytosis resulting in a faster rate of membrane retrieval. Surprisingly, endocytosis was unaffected by blockers of dynamin, suggesting that cone endocytosis is dynamin independent. This contrasts with synaptic vesicle endocytosis in rods, which was inhibited by the dynamin inhibitor dynasore and GTPγS introduced through the patch pipette, suggesting that the two photoreceptor types employ distinct pathways for vesicle retrieval. The fast kinetics of synaptic vesicle endocytosis in photoreceptors likely enables these cells to maintain a high rate of transmitter release, allowing them to faithfully signal changes in illumination to second-order neurons.
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11
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Yamashita T. Ca2+-dependent regulation of synaptic vesicle endocytosis. Neurosci Res 2012; 73:1-7. [DOI: 10.1016/j.neures.2012.02.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 02/16/2012] [Accepted: 02/17/2012] [Indexed: 01/25/2023]
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Perez Bay AE, Belingheri AV, Alvarez YD, Marengo FD. Membrane cycling after the excess retrieval mode of rapid endocytosis in mouse chromaffin cells. Acta Physiol (Oxf) 2012; 204:403-18. [PMID: 21791014 DOI: 10.1111/j.1748-1716.2011.02340.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM After exocytosis, neuroendocrine cells and neurones keep constant the plasma membrane and the releasable vesicle pools by performing endocytosis and vesicular cycling. Patch-clamp capacitance measurements on chromaffin cells showed that strong Ca(+2) entry activates excess retrieval: a rapid endocytosis process that retrieves more membrane than the one fused by preceding exocytosis. The main purpose of the present experiments was to study the recycling pathway that follows excess retrieval, which is unknown. METHODS Membrane recycling after exocytosis-endocytosis can be studied by fluorescence imaging assays with FM1-43 (Perez Bay et al. Am J Physiol Cell Physiol 2007; 293, C1509). In this work, we used this assay in combination with fluorescent dextrans and specific organelle-targeted antibodies to study the membrane recycling after excess retrieval in mouse chromaffin cells. RESULTS Excess retrieval was observed after the application of high-K(+) or cholinergic agonists during 15 or 30 s in the presence of FM1-43. We found that the excess retrieval membrane pool (defined as endocytosis-exocytosis) was associated with the generation of a non-releasable fraction of membrane (up to 30% of plasma membrane surface) colocalizing with the lysosomal compartment. The excess retrieval membrane pool followed a saturable cytosolic Ca(2+) dependency, and it was suppressed by inhibitors of L-type Ca(2+) channels, endoplasmic reticulum Ca(2+) release and PKC. CONCLUSION Excess retrieval is not associated with the cycling of releasable vesicles, but it is related to the formation of non-releasable endosomes. This process is activated by a concerted contribution of Ca(2+) entry through L-channels and Ca(2+) release from endoplasmic reticulum.
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Affiliation(s)
- A E Perez Bay
- Laboratorio de Fisiología y Biología Molecular, Departamento de Fisiología y Biología Molecular y Celular, Instituto de Fisiología, Biología Molecular y Neurociencias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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13
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Koch M, Holt M. Coupling exo- and endocytosis: an essential role for PIP₂ at the synapse. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1114-32. [PMID: 22387937 DOI: 10.1016/j.bbalip.2012.02.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Revised: 02/12/2012] [Accepted: 02/13/2012] [Indexed: 12/24/2022]
Abstract
Chemical synapses are specialist points of contact between two neurons, where information transfer takes place. Communication occurs through the release of neurotransmitter substances from small synaptic vesicles in the presynaptic terminal, which fuse with the presynaptic plasma membrane in response to neuronal stimulation. However, as neurons in the central nervous system typically only possess ~200 vesicles, high levels of release would quickly lead to a depletion in the number of vesicles, as well as leading to an increase in the area of the presynaptic plasma membrane (and possible misalignment with postsynaptic structures). Hence, synaptic vesicle fusion is tightly coupled to a local recycling of synaptic vesicles. For a long time, however, the exact molecular mechanisms coupling fusion and subsequent recycling remained unclear. Recent work now indicates a unique role for the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)), acting together with the vesicular protein synaptotagmin, in coupling these two processes. In this work, we review the evidence for such a mechanism and discuss both the possible advantages and disadvantages for vesicle recycling (and hence signal transduction) in the nervous system. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Marta Koch
- Laboratory of Neurogenetics, VIB Center for the Biology of Disease and K.U. Leuven Center for Human Genetics, O&N4 Herestraat 49, 3000 Leuven, Belgium
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14
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Uncoupling the roles of synaptotagmin I during endo- and exocytosis of synaptic vesicles. Nat Neurosci 2011; 15:243-9. [PMID: 22197832 PMCID: PMC3435110 DOI: 10.1038/nn.3013] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/14/2011] [Indexed: 11/29/2022]
Abstract
Synaptotagmin I (syt1) is required for normal rates of synaptic vesicle endo- and exocytosis. However, whether the kinetic defects observed during endocytosis in syt1 knock-out neurons are secondary to defective exocytosis, or whether syt1 directly regulates the rate of vesicle retrieval, remains unresolved. In order to address this question, it is necessary to dissociate these two activities. Here, we have uncoupled the function of syt1 in exo- and endocytosis by re-targeting of the protein, or via mutagenesis of its tandem C2-domains; the impact of these manipulations on exo- and endocytosis were analyzed via electrophysiology, in conjunction with optical imaging of the vesicle cycle. These experiments uncovered a direct role for syt1 in endocytosis. Surprisingly, either C2-domain of syt1 - C2A or C2B - was able to function as Ca2+-sensor for endocytosis. Hence, syt1 functions as a dual Ca2+ sensor for both endo- and exocytosis, potentially coupling these two limbs of the vesicle cycle.
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15
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Wu H, Gao SB, Sakurai T, Terakawa S. Fucoidan suppresses endocytosis in cultured HeLa cells. Chin J Integr Med 2011. [PMID: 21853347 DOI: 10.1007/s11655-011-0797-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Indexed: 10/17/2022]
Abstract
OBJECTIVE: To evaluate the effects of fucoidan on endocytosis in cultured HeLa cells: in vitro using live cell imaging. METHODS: A confocal scanning system and an incubation imaging system were used to: observe the effects of fucoidan on the initial (6 h) stages of endocytosis using the fl uorescent probe FM1-43 and inorganic fl uorescent quantum dot (Q-dots). RESULTS: According to the time-lapse images, fucoidan inhibited the: formation of endocytic vesicles in HeLa cells, in which the FM1-43 dye was entrapped. Fucoidan also had an inhibitory effect on the uptake of the Q-dots by the cell membranes of HeLa cells. CONCLUSION: It was concluded: that fucoidan suppresses Ca(2+)-dependent endocytosis in HeLa cells, which may be caused by its inhibitory -effects on agonist-induced Ca(2+) responses.
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Affiliation(s)
- Hong Wu
- The laboratory of Cell Imaging, Henan College of Traditional Chinese Medicine, Zhengzhou, 450002, China,
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16
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Lloyd-Evans E, Platt FM. Lysosomal Ca(2+) homeostasis: role in pathogenesis of lysosomal storage diseases. Cell Calcium 2011; 50:200-5. [PMID: 21724254 DOI: 10.1016/j.ceca.2011.03.010] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 03/21/2011] [Accepted: 03/24/2011] [Indexed: 01/07/2023]
Abstract
Disrupted cellular Ca(2+) signaling is believed to play a role in a number of human diseases including lysosomal storage diseases (LSD). LSDs are a group of ∼50 diseases caused predominantly by mutations in lysosomal proteins that result in accumulation of macromolecules within the lysosome. We recently reported that Niemann-Pick type C (NPC) is the first human disease to be associated with defective lysosomal Ca(2+) uptake and defective NAADP-mediated lysosomal Ca(2+) release. These defects in NPC cells leads to the disruption in endocytosis and subsequent lipid storage that is a feature of this disease. In contrast, Chediak-Higashi Syndrome cells have been reported to have enhanced lysosomal Ca(2+) uptake whilst the TRPML1 protein defective in mucolipidosis type IV is believed to function as a Ca(2+) channel. In this review we provide a summary of the current knowledge on the role of lysosomal Ca(2+) signaling in the pathogenesis of this group of diseases.
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Affiliation(s)
- Emyr Lloyd-Evans
- School of Biosciences, Biomedical Sciences Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, United Kingdom.
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Lariccia V, Fine M, Magi S, Lin MJ, Yaradanakul A, Llaguno MC, Hilgemann DW. Massive calcium-activated endocytosis without involvement of classical endocytic proteins. ACTA ACUST UNITED AC 2011; 137:111-32. [PMID: 21187336 PMCID: PMC3010057 DOI: 10.1085/jgp.201010468] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We describe rapid massive endocytosis (MEND) of >50% of the plasmalemma in baby hamster kidney (BHK) and HEK293 cells in response to large Ca transients. Constitutively expressed Na/Ca exchangers (NCX1) are used to generate Ca transients, whereas capacitance recording and a membrane tracer dye, FM 4–64, are used to monitor endocytosis. With high cytoplasmic adenosine triphosphate (ATP; >5 mM), Ca influx causes exocytosis followed by MEND. Without ATP, Ca transients cause only exocytosis. MEND can then be initiated by pipette perfusion of ATP, and multiple results indicate that ATP acts via phosphatidylinositol-bis 4,5-phosphate (PIP2) synthesis: PIP2 substitutes for ATP to induce MEND. ATP-activated MEND is blocked by an inositol 5-phosphatase and by guanosine 5′-[γ-thio]triphosphate (GTPγS). Block by GTPγS is overcome by the phospholipase C inhibitor, U73122, and PIP2 induces MEND in the presence of GTPγS. MEND can occur in the absence of ATP and PIP2 when cytoplasmic free Ca is clamped to 10 µM or more by Ca-buffered solutions. ATP-independent MEND occurs within seconds during Ca transients when cytoplasmic solutions contain polyamines (e.g., spermidine) or the membrane is enriched in cholesterol. Although PIP2 and cholesterol can induce MEND minutes after Ca transients have subsided, polyamines must be present during Ca transients. MEND can reverse over minutes in an ATP-dependent fashion. It is blocked by brief β-methylcyclodextrin treatments, and tests for involvement of clathrin, dynamins, calcineurin, and actin cytoskeleton were negative. Therefore, we turned to the roles of lipids. Bacterial sphingomyelinases (SMases) cause similar MEND responses within seconds, suggesting that ceramide may be important. However, Ca-activated MEND is not blocked by reagents that inhibit SMases. MEND is abolished by the alkylating phospholipase A2 inhibitor, bromoenol lactone, whereas exocytosis remains robust, and Ca influx causes MEND in cardiac myocytes without preceding exocytosis. Thus, exocytosis is not prerequisite for MEND. From these results and two companion studies, we suggest that Ca promotes the formation of membrane domains that spontaneously vesiculate to the cytoplasmic side.
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Affiliation(s)
- Vincenzo Lariccia
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
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18
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Hilgemann DW, Fine M. Mechanistic analysis of massive endocytosis in relation to functionally defined surface membrane domains. ACTA ACUST UNITED AC 2011; 137:155-72. [PMID: 21242299 PMCID: PMC3032373 DOI: 10.1085/jgp.201010470] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A large fraction of endocytosis in eukaryotic cells occurs without adaptors or dynamins. Here, we present evidence for the involvement of lipid domains in massive endocytosis (MEND) activated by both large Ca transients and amphipathic compounds in baby hamster kidney and HEK293 cells. First, we demonstrate functional coupling of the two MEND types. Ca transients can strongly facilitate detergent-activated MEND. Conversely, an amphipath with dual alkyl chains, ditridecylphthalate, is without effect in the absence of Ca transients but induces MEND to occur within seconds during Ca transients. Ca transients, like amphipaths, enhance the extraction of lipids from cells by β-cyclodextrins. Second, we demonstrate that electrical and/or optical signals generated by selected membrane probes are nearly insensitive to MEND, suggesting that those probes segregate into membrane domains that are not taken up by MEND. Triphenylphosphoniums are increasingly excluded from domains that internalize as the carbon chain length increases from 4 to 12. The small cationic membrane dye, FM 4–64, binds well to domains that internalize, whereas a closely related dye with a larger hydrophobic moiety, di-4-ANEPPDHQ (ANEPPDHQ) is excluded. Multiple carrier-type ionophores and a small amphipathic anion, niflumic acid, are also excluded. Probes with modest MEND sensitivity include the hydrophobic anion, dipicrylamine, carbonyl cyanide m-chlorophenylhydrazone, and NBD-phosphatidylethanolamine. Third, we demonstrate that large Ca transients can strongly enhance the extracellular binding of several membrane probes, monitored electrically or optically, consistent with a more disordered membrane with more amphipath-binding sites. Fluorescence shifts of ANEPPDHQ report increased disorder of the extracellular monolayer after large Ca transients, consistent with an increased propensity of the membrane to phase separate and vesiculate. Collectively, the results indicate that >50% of the outer monolayer is ordered and can be selectively internalized during MEND responses initiated by two very different cell perturbations.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA. donald.hilgemann@-utsouthwestern.edu
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20
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The role of calcium/calmodulin-activated calcineurin in rapid and slow endocytosis at central synapses. J Neurosci 2010; 30:11838-47. [PMID: 20810903 DOI: 10.1523/jneurosci.1481-10.2010] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Although the calcium/calmodulin-activated phosphatase calcineurin may dephosphorylate many endocytic proteins, it is not considered a key molecule in mediating the major forms of endocytosis at synapses-slow, clathrin-dependent and the rapid, clathrin-independent endocytosis. Here we studied the role of calcineurin in endocytosis by reducing calcium influx, inhibiting calmodulin with pharmacological blockers and knockdown of calmodulin, and by inhibiting calcineurin with pharmacological blockers and knock-out of calcineurin. These manipulations significantly inhibited both rapid and slow endocytosis at the large calyx-type synapse in 7- to 10-d-old rats and mice, and slow, clathrin-dependent endocytosis at the conventional cultured hippocampal synapse of rats and mice. These results suggest that calcium influx during nerve firing activates calcium/calmodulin-dependent calcineurin, which controls the speed of both rapid and slow endocytosis at synapses by dephosphorylating endocytic proteins. The calcium/calmodulin/calcineurin signaling pathway may underlie regulation of endocytosis by nerve activity and calcium as reported at many synapses over the last several decades.
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Rosa JM, Gandía L, García AG. Permissive role of sphingosine on calcium-dependent endocytosis in chromaffin cells. Pflugers Arch 2010; 460:901-14. [PMID: 20640579 DOI: 10.1007/s00424-010-0861-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Accepted: 06/22/2010] [Indexed: 01/09/2023]
Abstract
Sphingosine has been shown to modulate neurotransmitter release. Because membrane fusion and fission involve lipid metabolism, we asked here whether sphingosine had a role in regulating endocytosis. To explore this hypothesis, we monitored changes of membrane capacitance (Cm) to study the effects of intracellular sphingosine on membrane retrieval after chromaffin cell stimulation with depolarising pulses (DPs). We found that: (1) sphingosine dialysis through the patch-clamp pipette (SpD) using the whole-cell configuration of the patch-clamp technique (WCC) favours the appearance of a pronounced endocytotic response; (2) SpD-elicited endocytosis was Ca(2+)-dependent but Ba(2+) did not substitute Ca(2+); (3) under WCC, such endocytotic response disappeared with repetitive DPs; (4) in cells preincubated with sphingomyelinase to augment endogenous sphingosine synthesis, and then voltage-clamped under the perforated-patch configuration of the patch-clamp technique (PPC), endocytosis decayed little with repeated stimulation; (5) sphingosine-1-phosphate (S1P), a metabolite of sphingosine, had a meagre effect on endocytosis; and (6) neither dynamin inhibitor dynasore nor calmodulin blocker calmidazolium affected the sphingosine elicited endocytosis. We believe this is the first report showing that sphingosine plays a permissive role in activating Ca(2+)-dependent endocytosis during cell depolarisation. This effect requires high subplasmalemmal cytosolic Ca(2+) concentrations and a cytosolic factor(s) that is dialysed with the pipette solution. Independence of dynamin and calmodulin suggests that sphingosine-dependent endocytosis could be a novel, more direct pathway for vesicle recycling under mild depolarisation stimuli.
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Affiliation(s)
- Juliana M Rosa
- Instituto Teófilo Hernando Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo, 4, 28029, Madrid, Spain
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22
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Developmental shift to a mechanism of synaptic vesicle endocytosis requiring nanodomain Ca2+. Nat Neurosci 2010; 13:838-44. [PMID: 20562869 DOI: 10.1038/nn.2576] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Accepted: 05/12/2010] [Indexed: 11/08/2022]
Abstract
Ca(2+) is thought to be essential for the exocytosis and endocytosis of synaptic vesicles. However, the manner in which Ca(2+) coordinates these processes remains unclear, particularly at mature synapses. Using membrane capacitance measurements from calyx of Held nerve terminals in rats, we found that vesicle endocytosis is initiated primarily in Ca(2+) nanodomains around Ca(2+) channels, where exocytosis is triggered. Bulk Ca(2+) outside of the domain could also be involved in endocytosis at immature synapses, although only after extensive exocytosis at more mature synapses. This bulk Ca(2+)-dependent endocytosis required calmodulin and calcineurin activation at immature synapses, but not at more mature synapses. Similarly, GTP-independent endocytosis, which occurred after extensive exocytosis at immature synapses, became negligible after maturation. We propose that nanodomain Ca(2+) simultaneously triggers exocytosis and endocytosis of synaptic vesicles and that the molecular mechanisms underlying Ca(2+)-dependent endocytosis undergo major developmental changes at this fast central synapse.
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Di Giovanni J, Iborra C, Maulet Y, Lévêque C, El Far O, Seagar M. Calcium-dependent regulation of SNARE-mediated membrane fusion by calmodulin. J Biol Chem 2010; 285:23665-75. [PMID: 20519509 DOI: 10.1074/jbc.m109.096073] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuroexocytosis requires SNARE proteins, which assemble into trans complexes at the synaptic vesicle/plasma membrane interface and mediate bilayer fusion. Ca(2+) sensitivity is thought to be conferred by synaptotagmin, although the ubiquitous Ca(2+)-effector calmodulin has also been implicated in SNARE-dependent membrane fusion. To examine the molecular mechanisms involved, we examined the direct action of calmodulin and synaptotagmin in vitro, using fluorescence resonance energy transfer to assay lipid mixing between target- and vesicle-SNARE liposomes. Ca(2+)/calmodulin inhibited SNARE assembly and membrane fusion by binding to two distinct motifs located in the membrane-proximal regions of VAMP2 (K(D) = 500 nm) and syntaxin 1 (K(D) = 2 microm). In contrast, fusion was increased by full-length synaptotagmin 1 anchored in vesicle-SNARE liposomes. When synaptotagmin and calmodulin were combined, synaptotagmin overcame the inhibitory effects of calmodulin. Furthermore, synaptotagmin displaced calmodulin binding to target-SNAREs. These findings suggest that two distinct Ca(2+) sensors act antagonistically in SNARE-mediated fusion.
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24
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Ca(2+) and calmodulin initiate all forms of endocytosis during depolarization at a nerve terminal. Nat Neurosci 2009; 12:1003-1010. [PMID: 19633667 DOI: 10.1038/nn.2355] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Accepted: 06/01/2009] [Indexed: 11/08/2022]
Abstract
Although endocytosis maintains synaptic transmission, how endocytosis is initiated is unclear. We found that calcium influx initiated all forms of endocytosis at a single nerve terminal in rodents, including clathrin-dependent slow endocytosis, bulk endocytosis, rapid endocytosis and endocytosis overshoot (excess endocytosis), with each being evoked with a correspondingly higher calcium threshold. As calcium influx increased, endocytosis gradually switched from very slow endocytosis to slow endocytosis to bulk endocytosis to rapid endocytosis and to endocytosis overshoot. The calcium-induced endocytosis rate increase was a result of the speeding up of membrane invagination and fission. Pharmacological experiments suggested that the calcium sensor mediating these forms of endocytosis is calmodulin. In addition to its role in recycling vesicles, calcium/calmodulin-initiated endocytosis facilitated vesicle mobilization to the readily releasable pool, probably by clearing fused vesicle membrane at release sites. Our findings provide a unifying mechanism for the initiation of various forms of endocytosis that are critical in maintaining exocytosis.
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25
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The synaptic vesicle cluster: A source of endocytic proteins during neurotransmitter release. Neuroscience 2009; 158:204-10. [DOI: 10.1016/j.neuroscience.2008.03.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/17/2008] [Accepted: 03/18/2008] [Indexed: 12/11/2022]
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26
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Satoh S, Yanagita T, Maruta T, Nemoto T, Yoshikawa N, Kobayashi H, Tono T, Wada A. Proteasomal degradation of IRS-2, but not IRS-1 by calcineurin inhibition: Attenuation of insulin-like growth factor-I-induced GSK-3β and ERK pathways in adrenal chromaffin cells. Neuropharmacology 2008; 55:71-9. [DOI: 10.1016/j.neuropharm.2008.04.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2007] [Revised: 04/14/2008] [Accepted: 04/18/2008] [Indexed: 11/25/2022]
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27
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He Z, Fan J, Kang L, Lu J, Xue Y, Xu P, Xu T, Chen L. Ca2+Triggers a Novel Clathrin-Independent but Actin-Dependent Fast Endocytosis in Pancreatic Beta Cells. Traffic 2008; 9:910-23. [DOI: 10.1111/j.1600-0854.2008.00730.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Borges R, Camacho M, Gillis KD. Measuring secretion in chromaffin cells using electrophysiological and electrochemical methods. Acta Physiol (Oxf) 2008; 192:173-84. [PMID: 18021323 DOI: 10.1111/j.1748-1716.2007.01814.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Our present understanding of exocytosis of catecholamines has benefited tremendously from the arrival of single-cell electrochemical methods (amperometry and voltammetry), electrophysiological techniques (whole-cell and patch capacitance) and from the combination of both techniques (patch amperometry). In this brief review, we will outline the strengths and limitations of amperometric and electrophysiological methods and highlight the major contribution obtained with the use of these techniques in chromaffin cells.
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Affiliation(s)
- R Borges
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, Tenerife, Spain.
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29
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Díaz-Flores L, Gutiérrez R, Varela H, Valladares F, Alvarez-Argüelles H, Borges R. Histogenesis and morphofunctional characteristics of chromaffin cells. Acta Physiol (Oxf) 2008; 192:145-63. [PMID: 18021326 DOI: 10.1111/j.1748-1716.2007.01811.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
This article reviews the current status of research about the histogenesis and morphofunctional characteristics of chromaffin cells in the adrenal medulla. First, this study reports the selective migration, transcription and activation factors, and the morphological events of the chromaffin cell precursors during adrenal medulla development. Subsequently, the morphofunctional characteristics of adrenergic and non-adrenergic cells are considered, with particular reference to the characteristics of chromaffin granules and their biological steps, including their formation, traffic (storage, targeting and docking), exocytosis in the strict sense and recapture. Moreover, the relationship of chromaffin cells with other tissue components of the adrenal medulla is also revised, comprising the ganglion cells, sustentacular cells, nerves and connective-vascular tissue.
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Affiliation(s)
- L Díaz-Flores
- Department of Pathology and Histology, School of Medicine, La Laguna University, Canary Islands, Spain.
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30
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Abstract
Exocytosis occurs via fusion of secretory granules with the cell membrane, whereupon the granule content is at least partially released and the granule membrane is temporarily added to the plasma membrane. Exocytosis is balanced by compensatory endocytosis to achieve net equilibrium of the cell surface area and to recycle and redistribute components of the exocytosis machinery. The underlying molecular mechanisms remain a matter of debate. In this review, we summarize and discuss recent progress in the understanding of compensatory endocytosis, with the focus on chromaffin cells as a useful model for studying mechanisms of regulated secretion.
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Affiliation(s)
- S Barg
- Department of Cell Biology, Division of Medicine, Imperial College, London, UK.
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31
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de Diego AMG, Gandía L, García AG. A physiological view of the central and peripheral mechanisms that regulate the release of catecholamines at the adrenal medulla. Acta Physiol (Oxf) 2008; 192:287-301. [PMID: 18005392 DOI: 10.1111/j.1748-1716.2007.01807.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Here we review the tight neural control of the differential secretion into the circulation, of the adrenal medullary hormones adrenaline and noradrenaline. One or the other catecholamines are differentially released on various stress conditions. This is specifically controlled by central nervous system nuclei at the cortex, hypothalamus and spinal cord. Different firing patterns of splanchnic nerves and nicotinic or muscarinic receptors cause the selective release of noradrenaline or adrenaline, to adapt the body to the 'fight or flight' reaction, or during severe hypoglycaemia, haemorrhage, cold, acute myocardial infarction or other severe stressful conflicts. Endogenously acetylcholine (ACh) released at the splanchnic nerve-chromaffin cell synapse, acting on muscarinic and nicotinic receptors, causes membrane depolarization and action potentials (AP) in chromaffin cells. These changes vary with the animal species, the cell preparation (intact bisected adrenal, adrenal slices, or isolated fresh or cultured cells) or the recording technique (intracellular microelectrodes, patch-clamp, perforated-patch, cell-attached). Conflicting results leave many open questions concerning the actions of ACh on chromaffin cell excitability. The use of adrenal slices and field electrical stimulation will surely provide new insights into these mechanisms. Chromaffin cells have been thoroughly used as models to study the relationship between Ca2+ entry, cytosolic Ca2+ signals, exocytosis and endocytosis, using patch-clamp and amperometric techniques. Cells have been stimulated with single depolarizing pulses (DPs), DP trains and with simulated AP waveforms. These approaches have provided useful information but we have no data on APs generated by pulsatile secretory quanta of ACh, trying to mimic the intermittent and repetitive splanchnic nerve discharge of the neurotransmitter. We present some recent experiments using ultrashort ACh pulses (25 ms), that cause non-desensitizing repetitive APs with each ACh pulse, at low ACh concentrations (30 microM). Ultrashort pulses of a high ACh concentration (1000 microM) causes a single AP followed by a prolonged depolarization. It could be interesting trying to correlate these 'patterns of splanchnic nerve discharge' with Ca2+ signals and exocytosis. This, together with the use of adrenal slices and transmural electrical stimulation of splanchnic nerves will provide new physiologically sound data on the regulation of adrenal medullary secretion.
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Affiliation(s)
- A M G de Diego
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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Oliveria SF, Dell'Acqua ML, Sather WA. AKAP79/150 anchoring of calcineurin controls neuronal L-type Ca2+ channel activity and nuclear signaling. Neuron 2007; 55:261-75. [PMID: 17640527 PMCID: PMC2698451 DOI: 10.1016/j.neuron.2007.06.032] [Citation(s) in RCA: 267] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Revised: 03/27/2007] [Accepted: 06/27/2007] [Indexed: 10/23/2022]
Abstract
Neuronal L-type calcium channels contribute to dendritic excitability and activity-dependent changes in gene expression that influence synaptic strength. Phosphorylation-mediated enhancement of L-type channels containing the CaV1.2 pore-forming subunit is promoted by A-kinase anchoring proteins (AKAPs) that target cAMP-dependent protein kinase (PKA) to the channel. Although PKA increases L-type channel activity in dendrites and dendritic spines, the mechanism of enhancement in neurons remains poorly understood. Here, we show that CaV1.2 interacts directly with AKAP79/150, which binds both PKA and the Ca2+/calmodulin-activated phosphatase calcineurin (CaN). Cotargeting of PKA and CaN by AKAP79/150 confers bidirectional regulation of L-type current amplitude in transfected HEK293 cells and hippocampal neurons. However, anchored CaN dominantly suppresses PKA enhancement of the channel. Additionally, activation of the transcription factor NFATc4 via local Ca2+ influx through L-type channels requires AKAP79/150, suggesting that this signaling complex promotes neuronal L channel signaling to the nucleus through NFATc4.
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Affiliation(s)
- Seth F Oliveria
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
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Harush-Frenkel O, Debotton N, Benita S, Altschuler Y. Targeting of nanoparticles to the clathrin-mediated endocytic pathway. Biochem Biophys Res Commun 2006; 353:26-32. [PMID: 17184736 DOI: 10.1016/j.bbrc.2006.11.135] [Citation(s) in RCA: 390] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 11/16/2006] [Indexed: 02/08/2023]
Abstract
Nanoparticles (NPs) are considered attractive carriers for gene therapy and drug delivery owing to their minor toxic effect and their ability to associate and internalize into mammalian cells. In this study, we compared the endocytosis into HeLa cells of NPs exposing either a negative or positive charge on their surface. The exposed charge significantly affected their ability to internalize as well as the cellular endocytosis mechanism utilized. Negatively charged NPs show an inferior rate of endocytosis and do not utilize the clathrin-mediated endocytosis pathway. On the other hand, positively charged NPs internalize rapidly via the clathrin-mediated pathway. When this pathway is blocked, NPs activate a compensatory endocytosis pathway that results in even higher accumulation of NPs. Overall, the addition of a positive charge to NPs may improve their potential as nanoparticulate carriers for drug delivery.
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Affiliation(s)
- Oshrat Harush-Frenkel
- Departments of Pharmaceutics, The School of Pharmacy, The Hebrew University of Jerusalem, POB 12065, Jerusalem 91120, Israel
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Harata NC, Aravanis AM, Tsien RW. Kiss-and-run and full-collapse fusion as modes of exo-endocytosis in neurosecretion. J Neurochem 2006; 97:1546-70. [PMID: 16805768 DOI: 10.1111/j.1471-4159.2006.03987.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neurotransmitters and hormones are released from neurosecretory cells by exocytosis (fusion) of synaptic vesicles, large dense-core vesicles and other types of vesicles or granules. The exocytosis is terminated and followed by endocytosis (retrieval). More than fifty years of research have established full-collapse fusion and clathrin-mediated endocytosis as essential modes of exo-endocytosis. Kiss-and-run and vesicle reuse represent alternative modes, but their prevalence and importance have yet to be elucidated, especially in neurons of the mammalian CNS. Here we examine various modes of exo-endocytosis across a wide range of neurosecretory systems. Full-collapse fusion and kiss-and-run coexist in many systems and play active roles in exocytotic events. In small nerve terminals of CNS, kiss-and-run has an additional role of enabling nerve terminals to conserve scarce vesicular resources and respond to high-frequency inputs. Full-collapse fusion and kiss-and-run will each contribute to maintaining cellular communication over a wide range of frequencies.
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Affiliation(s)
- Nobutoshi C Harata
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, USA
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35
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Kaneko T, Harasztosi C, Mack AF, Gummer AW. Membrane traffic in outer hair cells of the adult mammalian cochlea. Eur J Neurosci 2006; 23:2712-22. [PMID: 16817874 DOI: 10.1111/j.1460-9568.2006.04796.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Outer hair cells (OHCs), the sensory-motor cells responsible for the extraordinary frequency selectivity and dynamic range of the cochlea, rapidly endocytose membrane and protein at their apical surface. Endocytosis and transcytosis in isolated OHCs from the mature guinea-pig cochlea were investigated using the amphipathic membrane probe FM1-43. We observed membrane transport from the apical surface to both the basolateral wall and the subnuclear pole. By double-labelling with DiOC6, a stain for endoplasmic reticulum, and aspiration of the plasma membrane, we showed that the basolateral target was the subsurface cisternae. The fluorescent signal was about three times weaker at the basal than at the apical pole. The speed of vesicle transport to the subnuclear pole was approximately 0.4 microm/s. Changing extracellular Ca2+ concentration from 25 microM to 2 mM accelerated rapid endocytosis. Extracellular application of BAPTA-AM (25 microM), an intracellular Ca2+ chelator, and TFP (20 microM), a specific inhibitor of calmodulin, reduced endocytic activity, as did depolarization of the whole cell. The presence of extracellular Cd2+ (200 microM), a Ca2+-channel blocker, had no effect on the voltage dependence of endocytosis at the apical pole, and inhibited the voltage dependence at the subnuclear pole. These results suggest that rapid endocytosis is a Ca2+/calmodulin-dependent process, with extracellular Ca2+ entering through voltage-gated Ca2+ channels at the basal pole. The two distinct destinations of endocytosed membrane are consistent with the functional polarization of the OHC, with the basolateral wall being dedicated to electromechanical transduction and the subnuclear pole being dedicated to electrochemical transduction processes.
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Affiliation(s)
- Toshihiko Kaneko
- Department of Otolaryngology, Section of Physiological Acoustics and Communication, University of Tübingen, Elfriede-Aulhorn-Str. 5, 72076, Tübingen, Germany
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Elhamdani A, Azizi F, Solomaha E, Palfrey HC, Artalejo CR. Two mechanistically distinct forms of endocytosis in adrenal chromaffin cells: Differential effects of SH3 domains and amphiphysin antagonism. FEBS Lett 2006; 580:3263-9. [PMID: 16696976 DOI: 10.1016/j.febslet.2006.04.083] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 04/14/2006] [Accepted: 04/25/2006] [Indexed: 10/24/2022]
Abstract
We previously identified two forms of endocytosis using capacitance measurements in chromaffin cells: rapid endocytosis (RE), dynamin-1 dependent but clathrin-independent and slow endocytosis (SE), dynamin-2 and clathrin-dependent. Various recombinant SH3 domains that interact with the proline-rich domain of dynamin were introduced into single cells via the patch pipette. GST-SH3 domains of amphiphysin-1, intersectin-IC, and endophilin-I inhibited SE but had no effect on RE. Grb2-SH3 (N-terminal) or a mutant of amphiphysin-1-SH3 was inactive on either process. These data confirm that dynamin-1 dependent RE is independent of clathrin and show that amphiphysin is exclusively associated with clathrin and dynamin-2-dependent SE.
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Affiliation(s)
- Abdeladim Elhamdani
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
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Elhamdani A, Azizi F, Artalejo CR. Double patch clamp reveals that transient fusion (kiss-and-run) is a major mechanism of secretion in calf adrenal chromaffin cells: high calcium shifts the mechanism from kiss-and-run to complete fusion. J Neurosci 2006; 26:3030-6. [PMID: 16540581 PMCID: PMC6673983 DOI: 10.1523/jneurosci.5275-05.2006] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transient fusion ("kiss-and-run") is accepted as a mode of transmitter release both in central neurons and neuroendocrine cells, but the prevalence of this mechanism compared with full fusion is still in doubt. Using a novel double patch-clamp method (whole cell/cell attached), permitting the recording of unitary capacitance events while stimulating under a variety of conditions including action potentials, we show that transient fusion is the predominant (>90%) mode of secretion in calf adrenal chromaffin cells. Raising intracellular Ca2+ concentration ([Ca]i) from 10 to 200 microM increases the incidence of full fusion events at the expense of transient fusion. Blocking rapid endocytosis that normally terminates transient fusion events also promotes full fusion events. Thus, [Ca]i controls the transition between transient and full fusion, each of which is coupled to different modes of endocytosis.
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Affiliation(s)
- Abdeladim Elhamdani
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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MacDonald PE, Eliasson L, Rorsman P. Calcium increases endocytotic vesicle size and accelerates membrane fission in insulin-secreting INS-1 cells. J Cell Sci 2005; 118:5911-20. [PMID: 16317049 DOI: 10.1242/jcs.02685] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In many cells, endocytotic membrane retrieval is accelerated by Ca2+. The effect of Ca2+ on single endocytotic vesicles and fission pore kinetics was examined by measuring capacitance and conductance changes in small membrane patches of insulin-secreting INS-1 cells. In intact cells, elevation of Ca2+ by glucose stimulation induced a 1.8-fold increase in membrane internalisation. This surprisingly resulted from an increased unitary capacitance of endocytotic vesicles whereas the frequency of endocytosis was unaltered. This effect of glucose was prevented by inhibition of L- or R-type Ca2+ channels. Extracellular (pipette) Ca2+ was found to regulate endocytotic vesicle capacitance in a bimodal manner. Vesicle capacitance was increased at intermediate Ca2+ (2.6 mM), but not at high Ca2+ (10 mM). Similar results were obtained upon direct application of 100 nM and 0.5 mM Ca2+ to the intracellular surface of inside-out excised membrane patches, and in these experiments the increase in vesicle capacitance was prevented by the calcineurin inhibitor deltamethrin. Endocytotic fission pore kinetics were accelerated by Ca2+ in both the intact cells and isolated membrane patches; however, the effect in this case was neither bimodal nor deltamethrin sensitive. Membrane retrieval can therefore be upregulated by a Ca2+-dependent increase in endocytotic vesicle size and acceleration of membrane fission in insulin-secreting INS-1 cells.
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Affiliation(s)
- Patrick E MacDonald
- Division of Diabetes, Metabolism and Endocrinology, Lund University, 221 84 Lund, Sweden.
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Smillie KJ, Evans GJO, Cousin MA. Developmental change in the calcium sensor for synaptic vesicle endocytosis in central nerve terminals. J Neurochem 2005; 94:452-8. [PMID: 15998295 PMCID: PMC2040260 DOI: 10.1111/j.1471-4159.2005.03213.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Synaptic vesicle endocytosis is stimulated by calcium influx in mature central nerve terminals via activation of the calcium-dependent protein phosphatase, calcineurin. However, in different neuronal preparations calcineurin activity is either inhibitory, stimulatory or irrelevant to the process. We addressed this inconsistency by investigating the requirement for calcineurin activity in synaptic vesicle endocytosis during development, using vesicle recycling assays in isolated nerve terminals. We show that endocytosis occurs independently of calcineurin activity in immature nerve terminals, and that a calcineurin requirement develops 2-4 weeks after birth. Calcineurin-independent endocytosis is not due to the absence of calcineurin activity, since calcineurin is present in immature nerve terminals and its substrate, dynamin I, is dephosphorylated on depolarization. Calcineurin-independent endocytosis is calcium-dependent, since substitution of the divalent cation, barium, inhibits the process. Finally, we demonstrated that in primary neuronal cultures derived from neonatal rats, endocytosis that was initially calcineurin-independent developed a calcineurin requirement on maturation in culture. Our data account for the apparent inconsistencies regarding the role of calcineurin in synaptic vesicle endocytosis, and we propose that an unidentified calcium sensor exists to couple calcium influx to endocytosis in immature nerve terminals.
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Affiliation(s)
| | | | - Michael A. Cousin
- Author to whom correspondence should be addressed, Membrane Biology Group, Division of Biomedical and Clinical Laboratory Sciences, George Square, University of Edinburgh, Edinburgh, UK, EH8 9XD, Tel - +44131 6503259, Fax - +44131 6506527, Email -
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Abstract
Neurons communicate with one another through the release of molecules from synaptic vesicles and large dense core granules through the process of exocytosis. During exocytosis, molecules are released to the extracellular space through a fusion pore, which can either dilate, resulting in full fusion, or close, resulting in incomplete exocytosis, often referred to as 'kiss and run' exocytosis. Recently, there has been much interest in the regulation of this process in both neurons and neuroendocrine cells. There has been much recent work that addresses the existence of incomplete exocytosis in neurons and neuroendocrine cells, as well as recent work probing the molecular components and modulation of the fusion pore.
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Affiliation(s)
- Seong An
- Yale University School of Medicine, Department of Cellular and Molecular Physiology, Sterling Hall of Medicine, B-147, 333 Cedar St, New Haven, Connecticut 06520, USA
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Kumashiro S, Lu YF, Tomizawa K, Matsushita M, Wei FY, Matsui H. Regulation of synaptic vesicle recycling by calcineurin in different vesicle pools. Neurosci Res 2005; 51:435-43. [PMID: 15740806 DOI: 10.1016/j.neures.2004.12.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2004] [Revised: 12/21/2004] [Accepted: 12/21/2004] [Indexed: 11/19/2022]
Abstract
The synaptic vesicles keep recycling by the processes of endocytosis and exocytosis to maintain the normal synaptic transmission. The synaptic vesicles are classified as the readily releasable pool (RRP) and the reserve pool (RP). In the endocytosis process, calcineurin (CaN), a Ca2+/calmodulin-dependent protein phosphatase, has been shown to play important roles. However, it is unclear about its roles in different vesicle pools. Here, we investigated the role of CaN in the regulation of vesicle recycling in the RRP and RP. Vesicle recycling was monitored by using fluorescent dyes FM1-43 and FM4-64 in the primary cultures of hippocampal neurons. Inhibition of CaN by FK506 and cyclosporin A suppressed the endocytosis in the RP, but not in the RRP. Inhibition of CaN also restrained the exocytic process triggered by 10 Hz stimulation, but had no effect on 3-5 Hz stimulation-induced exocytosis. FK506 also reduced the total vesicle pool size in the synaptic terminals. A synthesized CaN inhibitory peptide showed the similar effects as FK506 and cyclosporin A. These results revealed a novel mechanism that CaN plays critical roles in the distinct vesicle recycling processes.
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Affiliation(s)
- Susumu Kumashiro
- Department of Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan
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Miyazaki K, Ishizuka T, Yawo H. Synapse-to-synapse variation of calcium channel subtype contributions in large mossy fiber terminals of mouse hippocampus. Neuroscience 2005; 136:1003-14. [PMID: 16226383 DOI: 10.1016/j.neuroscience.2005.08.049] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 07/23/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
Both N- and P/Q-type voltage-dependent calcium channels are involved in fast transmitter release in the hippocampus, but are differentially regulated. Although variable contributions of voltage-dependent calcium channel subtypes to presynaptic Ca2+ influx have been suggested to give a neural network of great diversity, their presence has only been demonstrated in a culture system and has remained unclear in the brain. Here, the individual large mossy fiber presynaptic terminal was labeled with Ca2+/Sr2+-sensitive fluorescent dextrans in the hippocampal slice of the mouse. The fractional contribution of voltage-dependent calcium channel subtypes to presynaptic Ca2+/Sr2+ influx was directly measured by the sensitivity of Ca2+/Sr2+-dependent fluorescent increment to subtype-selective neurotoxins, omega-conotoxin GVIA (an N-type selective blocker), omega-agatoxin IVA (a P/Q-type selective blocker) and SNX-482 (an R-type selective blocker). Synapse-to-synapse comparison of large mossy fiber terminals revealed that the contributions of N- and R-type voltage-dependent calcium channels varied more widely than that of P/Q-type. Even two large mossy fiber presynaptic terminals neighboring on the same axon differed in the fractional contributions of N- and R-type voltage-dependent calcium channels. On the other hand, these terminals were similar in the fractional contributions of P/Q-type voltage-dependent calcium channels. These results provide direct evidence that individual large mossy fiber synapses are differential in the contribution of N- and R-type voltage-dependent calcium channel subtypes to presynaptic Ca2+/Sr2+ influx. We suggest that the synapse-to-synapse variation of presynaptic voltage-dependent calcium channel subtype contributions may be one of the mechanisms amplifying diversity of the hippocampal network.
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Affiliation(s)
- K Miyazaki
- Department of Developmental Biology and Neurosciences, Tohoku University Graduate School of Life Sciences, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
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Marengo FD, Monck JR. Spatial distribution of Ca(2+) signals during repetitive depolarizing stimuli in adrenal chromaffin cells. Biophys J 2004; 85:3397-417. [PMID: 14581241 PMCID: PMC1303617 DOI: 10.1016/s0006-3495(03)74759-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Exocytosis in adrenal chromaffin cells is strongly influenced by the pattern of stimulation. To understand the dynamic and spatial properties of the underlying Ca(2+) signal, we used pulsed laser Ca(2+) imaging to capture Ca(2+) gradients during stimulation by single and repetitive depolarizing stimuli. Short single pulses (10-100 ms) lead to the development of submembrane Ca(2+) gradients, as previously described (F. D. Marengo and J. R. Monck, 2000, Biophysical Journal, 79:1800-1820). Repetitive stimulation with trains of multiple pulses (50 ms each, 2Hz) produce a pattern of intracellular Ca(2+) increase that progressively changes from the typical Ca(2+) gradient seen after a single pulse to a Ca(2+) increase throughout the cell that peaks at values 3-4 times higher than the maximum values obtained at the end of single pulses. After seven or more pulses, the fluorescence increase was typically larger in the interior of the cell than in the submembrane region. The pattern of Ca(2+) gradient was not modified by inhibitors of Ca(2+)-induced Ca(2+) release (ryanodine), inhibitors of IP(3)-induced Ca(2+) release (xestospongin), or treatments designed to deplete intracellular Ca(2+) stores (thapsigargin). However, we found that the large fluorescence increase in the cell interior spatially colocalized with the nucleus. These results can be simulated using mathematical models of Ca(2+) redistribution in which the nucleus takes up Ca(2+) by active or passive transport mechanisms. These results show that chromaffin cells can respond to depolarizing stimuli with different dynamic Ca(2+) signals in the submembrane space, the cytosol, and the nucleus.
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Affiliation(s)
- Fernando D Marengo
- Department of Physiology, UCLA School of Medicine, Los Angeles, California 90095, USA
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Nagy G, Reim K, Matti U, Brose N, Binz T, Rettig J, Neher E, Sørensen JB. Regulation of releasable vesicle pool sizes by protein kinase A-dependent phosphorylation of SNAP-25. Neuron 2004; 41:417-29. [PMID: 14766180 DOI: 10.1016/s0896-6273(04)00038-8] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Revised: 12/02/2003] [Accepted: 01/07/2004] [Indexed: 11/18/2022]
Abstract
Protein kinase A (PKA) is a key regulator of neurosecretion, but the molecular targets remain elusive. We combined pharmacological manipulations of kinase and phosphatase activities with mutational studies on the exocytotic machinery driving fusion of catecholamine-containing vesicles from chromaffin cells. We found that constitutive PKA activity was necessary to maintain a large number of vesicles in the release-ready, so-called primed, state, whereas calcineurin (protein phosphatase 2B) activity antagonized this effect. Overexpression of the SNARE protein SNAP-25a mutated in a PKA phosphorylation site (Thr-138) eliminated the effect of PKA inhibitors on the vesicle priming process. Another, unidentified, PKA target regulated the relative size of two different primed vesicle pools that are distinguished by their release kinetics. Overexpression of the SNAP-25b isoform increased the size of both primed vesicle pools by a factor of two, and mutations in the conserved Thr-138 site had similar effects as in the a isoform.
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Affiliation(s)
- Gábor Nagy
- Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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Chan SA, Smith C. Low frequency stimulation of mouse adrenal slices reveals a clathrin-independent, protein kinase C-mediated endocytic mechanism. J Physiol 2003; 553:707-17. [PMID: 14500763 PMCID: PMC2343636 DOI: 10.1113/jphysiol.2003.053918] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Evidence suggests that chromaffin cells employ separate mechanisms for evoked endocytosis and granule recycling when stimulated at basal (approximately 0.5 Hz) and stress-activated (approximately 15 Hz) rates. Previous studies have focused mainly on elucidating the cellular mechanisms responsible for membrane recycling under conditions similar to the stress-activated state and indicate a clathrin/dephosphin-mediated retrieval via coated pits. However, the mechanism for membrane internalisation at basal stimulus intensity remains largely unexplored. We electrically stimulated chromaffin cells in adrenal tissue slices at the sympathetic basal firing rate and measured cell capacitance in the perforated voltage clamp configuration. A new method for the separation of non-secretory from secretory cell capacitance signals is presented. Simultaneous catecholamine release was measured electrochemically to isolate the exocytic from endocytic components of the capacitance responses. Using this approach we demonstrate that firing patterns that mimic basal sympathetic input results in rapid and graded membrane retrieval. We show that block of the calcium-mediated protein phosphatase 2B, a common step in clathrin-mediated processes, did not alter endocytosis elicited at basal firing levels. We further blocked clathrin-mediated retrieval with a clathrin/dephosphin-disrupting peptide (PP-19) and found endocytosis to be blocked at 15 Hz stimulation but complete and indistinguishable from control cells at 0.5 Hz stimulation. Lastly, pharmacological treatments show that conventional isoforms of protein kinase C (cPKC) are required for the 0.5 Hz-evoked retrieval mechanism. From these data we conclude that unlike endocytosis evoked under stress conditions, basal firing activity results in a clathrin-independent rapid membrane retrieval mediated through conventional isoforms of PKC.
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Affiliation(s)
- Shyue-An Chan
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106-4970, USA
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46
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Abstract
The chemical synapse is a specialized intercellular junction that operates nearly autonomously to allow rapid, specific, and local communication between neurons. Focusing our attention on the presynaptic terminal, we review the current understanding of how synaptic morphology is maintained and then the mechanisms in synaptic vesicle exocytosis and recycling.
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Affiliation(s)
- Venkatesh N Murthy
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
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47
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Baldassarre M, Pompeo A, Beznoussenko G, Castaldi C, Cortellino S, McNiven MA, Luini A, Buccione R. Dynamin participates in focal extracellular matrix degradation by invasive cells. Mol Biol Cell 2003; 14:1074-84. [PMID: 12631724 PMCID: PMC151580 DOI: 10.1091/mbc.e02-05-0308] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The degradation of extracellular matrix (ECM) by matrix metalloproteases is crucial in physiological and pathological cell invasion alike. Degradation occurs at specific sites where invasive cells make contact with the ECM via specialized plasma membrane protrusions termed invadopodia. Herein, we show that the dynamin 2 (Dyn2), a GTPase implicated in the control of actin-driven cytoskeletal remodeling events and membrane transport, is necessary for focalized matrix degradation at invadopodia. Dynamin was inhibited by using two approaches: 1) expression of dominant negative GTPase-impaired or proline-rich domain-deleted Dyn2 mutants; and 2) inhibition of the dynamin regulator calcineurin by cyclosporin A. In both cases, the number and extension of ECM degradation foci were drastically reduced. To understand the site and mechanism of dynamin action, the cellular structures devoted to ECM degradation were analyzed by correlative confocal light-electron microscopy. Invadopodia were found to be organized into a previously undescribed ECM-degradation structure consisting of a large invagination of the ventral plasma membrane surface in close spatial relationship with the Golgi complex. Dyn2 seemed to be concentrated at invadopodia.
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Affiliation(s)
- Massimiliano Baldassarre
- Department of Cell Biology and Oncology, Istituto di Ricerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, S. Maria Imbaro (Chieti), 66030 Italy
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48
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Quetglas S, Iborra C, Sasakawa N, De Haro L, Kumakura K, Sato K, Leveque C, Seagar M. Calmodulin and lipid binding to synaptobrevin regulates calcium-dependent exocytosis. EMBO J 2002; 21:3970-9. [PMID: 12145198 PMCID: PMC126150 DOI: 10.1093/emboj/cdf404] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter release involves the assembly of a heterotrimeric SNARE complex composed of the vesicle protein synaptobrevin (VAMP 2) and two plasma membrane partners, syntaxin 1 and SNAP-25. Calcium influx is thought to control this process via Ca(2+)-binding proteins that associate with components of the SNARE complex. Ca(2+)/calmodulin or phospholipids bind in a mutually exclusive fashion to a C-terminal domain of VAMP (VAMP(77-90)), and residues involved were identified by plasmon resonance spectroscopy. Microinjection of wild-type VAMP(77-90), but not mutant peptides, inhibited catecholamine release from chromaffin cells monitored by carbon fibre amperometry. Pre-incubation of PC12 pheochromocytoma cells with the irreversible calmodulin antagonist ophiobolin A inhibited Ca(2+)-dependent human growth hormone release in a permeabilized cell assay. Treatment of permeabilized cells with tetanus toxin light chain (TeNT) also suppressed secretion. In the presence of TeNT, exocytosis was restored by transfection of TeNT-resistant (Q(76)V, F(77)W) VAMP, but additional targeted mutations in VAMP(77-90) abolished its ability to rescue release. The calmodulin- and phospholipid-binding domain of VAMP 2 is thus required for Ca(2+)-dependent exocytosis, possibly to regulate SNARE complex assembly.
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Affiliation(s)
- Stephanie Quetglas
- Institut National de la Santé et de la Recherche Médicale Unité 464, Université de la Méditerranée, 13916 Marseille Cedex 20, France
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Congar P, Trudeau LE. Perturbation of synaptic vesicle delivery during neurotransmitter release triggered independently of calcium influx. J Physiol 2002; 542:779-93. [PMID: 12154178 PMCID: PMC2290460 DOI: 10.1113/jphysiol.2002.020222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Although much evidence suggests that calcium (Ca(2+)) usually triggers synaptic vesicle exocytosis and neurotransmitter release, the role of Ca(2+) in vesicle endocytosis and in the delivery of fusion-competent vesicles (i.e. mobilisation and/or priming) in nerve terminals remains unclear. To address this issue, we have studied synaptic vesicle dynamics in cultured rat neurones under conditions where neurotransmitter release is triggered independently of Ca(2+) using the secretagogue Ruthenium Red (RR). Using a prolonged stimulation protocol, we find that RR causes a rapid increase in neurotransmitter release followed by a gradually decrementing response. In contrast, when release is triggered by moderate membrane depolarisation caused by saline containing 18 mM K(+), release is sustained. These observations suggest that when release is triggered independently of a rise in Ca(2+), endocytosis or vesicle mobilisation/priming are perturbed. Using FM2-10, a fluorescent indicator of synaptic vesicle cycling, we find that neurotransmitter release triggered by RR is accompanied by both uptake and release of this dye, thereby suggesting that vesicle endocytosis is not blocked. To evaluate whether synaptic vesicle mobilisation/priming is perturbed in the absence of a rise in Ca(2+), we compared the kinetics of FM2-10 loss during prolonged stimulation. While 18 mM K(+) induced gradual and continuous dye loss, RR only induced substantial dye loss during the first minute of stimulation. In the presence of low concentrations of the Ca(2+) ionophore ionomycin, release caused by RR was prolonged. Taken together, these results provide evidence suggesting that, although a rise in intraterminal Ca(2+) is not required for endocytosis, it is essential for the continuous delivery of fusion-competent vesicles and to maintain neurotransmitter release during prolonged stimulation.
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Affiliation(s)
- Patrice Congar
- Département de Pharmacologie, Centre de Recherche en Sciences Neurologiques and Centre de Recherche Fernand Seguin, Faculté de Médecine, Université de Montréal, Québec, Canada
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Affiliation(s)
- Edwin R Chapman
- Department of Physiology, University of Wisconsin, Madison, Wisconsin 53706, USA.
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