1
|
Abstract
Precise and efficient coupling of endocytosis to exocytosis is critical for neurotransmission. The activity-dependent facilitation of endocytosis has been well established for efficient membrane retrieval; however, whether neural activity clamps endocytosis to avoid excessive membrane retrieval remains debatable with the mechanisms largely unknown. The present work provides compelling evidence that synaptotagmin-1 (Syt1) functions as a primary bidirectional Ca2+ sensor to promote slow, small-sized clathrin-mediated endocytosis but inhibit the fast, large-sized bulk endocytosis during elevated neural activity, the disruption of which leads to inefficient vesicle recycling under mild stimulation but excessive membrane retrieval following sustained neurotransmission. Thus, Syt1 serves as a fine-tuning Ca2+ sensor to ensure both efficient and precise coupling of endocytosis to exocytosis in response to different neural activities. Exocytosis and endocytosis are tightly coupled. In addition to initiating exocytosis, Ca2+ plays critical roles in exocytosis–endocytosis coupling in neurons and nonneuronal cells. Both positive and negative roles of Ca2+ in endocytosis have been reported; however, Ca2+ inhibition in endocytosis remains debatable with unknown mechanisms. Here, we show that synaptotagmin-1 (Syt1), the primary Ca2+ sensor initiating exocytosis, plays bidirectional and opposite roles in exocytosis–endocytosis coupling by promoting slow, small-sized clathrin-mediated endocytosis but inhibiting fast, large-sized bulk endocytosis. Ca2+-binding ability is required for Syt1 to regulate both types of endocytic pathways, the disruption of which leads to inefficient vesicle recycling under mild stimulation and excessive membrane retrieval following intense stimulation. Ca2+-dependent membrane tubulation may explain the opposite endocytic roles of Syt1 and provides a general membrane-remodeling working model for endocytosis determination. Thus, Syt1 is a primary bidirectional Ca2+ sensor facilitating clathrin-mediated endocytosis but clamping bulk endocytosis, probably by manipulating membrane curvature to ensure both efficient and precise coupling of endocytosis to exocytosis.
Collapse
|
2
|
Peng YJ, Geng J, Wu Y, Pinales C, Langen J, Chang YC, Buser C, Chang KT. Minibrain kinase and calcineurin coordinate activity-dependent bulk endocytosis through synaptojanin. J Cell Biol 2021; 220:212674. [PMID: 34596663 PMCID: PMC8491876 DOI: 10.1083/jcb.202011028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 07/28/2021] [Accepted: 09/16/2021] [Indexed: 11/22/2022] Open
Abstract
Neurons use multiple modes of endocytosis, including clathrin-mediated endocytosis (CME) and activity-dependent bulk endocytosis (ADBE), during mild and intense neuronal activity, respectively, to maintain stable neurotransmission. While molecular players modulating CME are well characterized, factors regulating ADBE and mechanisms coordinating CME and ADBE activations remain poorly understood. Here we report that Minibrain/DYRK1A (Mnb), a kinase mutated in autism and up-regulated in Down's syndrome, plays a novel role in suppressing ADBE. We demonstrate that Mnb, together with calcineurin, delicately coordinates CME and ADBE by controlling the phosphoinositol phosphatase activity of synaptojanin (Synj) during varying synaptic demands. Functional domain analyses reveal that Synj's 5'-phosphoinositol phosphatase activity suppresses ADBE, while SAC1 activity is required for efficient ADBE. Consequently, Parkinson's disease mutation in Synj's SAC1 domain impairs ADBE. These data identify Mnb and Synj as novel regulators of ADBE and further indicate that CME and ADBE are differentially governed by Synj's dual phosphatase domains.
Collapse
Affiliation(s)
- Yi-Jheng Peng
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA.,Neuroscience Graduate Program, University of Southern California, Los Angeles, CA
| | - Junhua Geng
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Ying Wu
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | | | - Jennifer Langen
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Yen-Ching Chang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | | | - Karen T Chang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA.,Neuroscience Graduate Program, University of Southern California, Los Angeles, CA.,Department of Physiology & Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA
| |
Collapse
|
3
|
The Synaptic Vesicle Cycle Revisited: New Insights into the Modes and Mechanisms. J Neurosci 2020; 39:8209-8216. [PMID: 31619489 DOI: 10.1523/jneurosci.1158-19.2019] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/31/2019] [Accepted: 08/03/2019] [Indexed: 02/01/2023] Open
Abstract
Neurotransmission is sustained by endocytosis and refilling of synaptic vesicles (SVs) locally within the presynapse. Until recently, a consensus formed that after exocytosis, SVs are recovered by either fusion pore closure (kiss-and-run) or clathrin-mediated endocytosis directly from the plasma membrane. However, recent data have revealed that SV formation is more complex than previously envisaged. For example, two additional recycling pathways have been discovered, ultrafast endocytosis and activity-dependent bulk endocytosis, in which SVs are regenerated from the internalized membrane and synaptic endosomes. Furthermore, these diverse modes of endocytosis appear to influence both the molecular composition and subsequent physiological role of individual SVs. In addition, previously unknown complexity in SV refilling and reclustering has been revealed. This review presents a modern view of the SV life cycle and discusses how neuronal subtype, physiological temperature, and individual activity patterns can recruit different endocytic modes to generate new SVs and sculpt subsequent presynaptic performance.
Collapse
|
4
|
Bilkey J, Nahirney PC, Delaney KR. Time and exposure to serotonin affect releasability of recycled vesicles at crayfish claw opener muscle synapses. Synapse 2019; 74:e22136. [PMID: 31574172 DOI: 10.1002/syn.22136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/16/2019] [Accepted: 09/21/2019] [Indexed: 11/10/2022]
Abstract
The crayfish claw opener neuromuscular junction is a biological model for studying presynaptic neuromodulation by serotonin (5HT) and synaptic vesicle recycling. It has been hypothesized that 5HT enhances release by recruiting a population of either previously nonrecycling or "reluctant" vesicles to increase the readily releasable pool. To determine if 5HT activates a distinct population of synaptic vesicles, recycling membranes were labeled with the membrane dye, FM1-43. Unloading (destaining) protocols could not resolve a population of vesicles that were only releasable in the presence of 5HT. Instead, we conclude synaptic vesicles change behavior in axon terminals independent of 5HT, becoming less likely to exocytose and unload dye over periods of >1 hr after recycling. We hypothesized this to be due to the slow conversion of a portion of recycled vesicles to a difficult to release state. The possibility that vesicles in these pools were spatially separated within the terminal was tested using photoconversion of FM1-43 and transmission electron microscopy. The location of FM1-43-labeled vesicles fixed 2 min following 3 min of 20-Hz stimulation did not reveal preferential localization of recycling vesicles specifically near release sites and the distribution of labeled vesicles was not significantly different between early (2 min) and late (180 min) time points. Terminals fixed 30 s following stimulation contained a significant proportion of vesicular structures equivalent in diameter to 2-5 regular vesicles, with multivesicular bodies and calveoli rarely seen, suggesting that endocytosis during sustained release at crayfish terminals occurs via multiple routes, most commonly through large "vesicle" intermediates.
Collapse
Affiliation(s)
- Jessica Bilkey
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Patrick C Nahirney
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - Kerry R Delaney
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| |
Collapse
|
5
|
Song Q, Huang M, Wang B, Kang X, Wang C. Bidirectional regulation of Ca 2+ in exo-endocytosis coupling. SCIENCE CHINA-LIFE SCIENCES 2018; 61:1583-1585. [PMID: 30484064 DOI: 10.1007/s11427-018-9429-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 11/16/2018] [Indexed: 10/27/2022]
Affiliation(s)
- Qian Song
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China
| | - Mingzhu Huang
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.,College of Life Sciences, Liaocheng University, Liaocheng, 252059, China
| | - Bianbian Wang
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.,College of Life Sciences, Liaocheng University, Liaocheng, 252059, China
| | - Xinjiang Kang
- College of Life Sciences, Liaocheng University, Liaocheng, 252059, China.,DOE-Key Lab of Medical Electrophysiology, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China
| | - Changhe Wang
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.
| |
Collapse
|
6
|
Brodin L, Shupliakov O. Retromer in Synaptic Function and Pathology. Front Synaptic Neurosci 2018; 10:37. [PMID: 30405388 PMCID: PMC6207580 DOI: 10.3389/fnsyn.2018.00037] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 10/03/2018] [Indexed: 12/15/2022] Open
Abstract
The retromer complex mediates export of select transmembrane proteins from endosomes to the trans-Golgi network (TGN) or to the plasma membrane. Dysfunction of retromer has been linked with slowly progressing neurodegenerative disorders, including Alzheimer’s and Parkinson’s disease (AD and PD). As these disorders affect synapses it is of key importance to clarify the function of retromer-dependent protein trafficking pathways in pre- and postsynaptic compartments. Here we discuss recent insights into the roles of retromer in the trafficking of synaptic vesicle proteins, neurotransmitter receptors and other synaptic proteins. We also consider evidence that implies synapses as sites of early pathology in neurodegenerative disorders, pointing to a possible role of synaptic retromer dysfunction in the initiation of disease.
Collapse
Affiliation(s)
- Lennart Brodin
- Department of Neuroscience, Karolinska Institutet (KI), Stockholm, Sweden
| | - Oleg Shupliakov
- Department of Neuroscience, Karolinska Institutet (KI), Stockholm, Sweden.,Institute of Translational Biomedicine, St. Petersburg University, St. Petersburg, Russia
| |
Collapse
|
7
|
Tarasov AI, Galvanovskis J, Rorsman O, Hamilton A, Vergari E, Johnson PRV, Reimann F, Ashcroft FM, Rorsman P. Monitoring real-time hormone release kinetics via high-content 3-D imaging of compensatory endocytosis. LAB ON A CHIP 2018; 18:2838-2848. [PMID: 30083680 PMCID: PMC6250124 DOI: 10.1039/c8lc00417j] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 07/26/2018] [Indexed: 05/02/2023]
Abstract
High-content real-time imaging of hormone secretion in tissues or cell populations is a challenging task, which is unlikely to be resolved directly, despite immense translational value. We approach this problem indirectly, using compensatory endocytosis, a process that closely follows exocytosis in the cell, as a surrogate read-out for secretion. The tissue is immobilized in an open-air perifusion chamber and imaged using a two-photon microscope. A fluorescent polar tracer, perifused through the experimental circuit, gets trapped into the cells via endocytosis, and is quantified using a feature-detection algorithm. The signal of the tracer that accumulates into the endocytotic system reliably reflects stimulated exocytosis, which is demonstrated via co-imaging of the latter using existing reporters. A high signal-to-noise ratio and compatibility with multisensor imaging affords the real-time quantification of the secretion at the tissue/population level, whereas the cumulative nature of the signal allows imprinting of the "secretory history" within each cell. The technology works for several cell types, reflects disease progression and can be used for human tissue.
Collapse
Affiliation(s)
- Andrei I Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK. and Oxford National Institute for Health Research, Biomedical Research Centre, Churchill Hospital, Oxford OX3 7LE, UK
| | - Juris Galvanovskis
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK.
| | - Olof Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK.
| | - Alexander Hamilton
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK.
| | - Elisa Vergari
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK.
| | - Paul R V Johnson
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK.
| | - Frank Reimann
- Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, CB2 0QQ UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks road, Oxford, OX1 3PT, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, OX3 7LE, Oxford, UK. and Oxford National Institute for Health Research, Biomedical Research Centre, Churchill Hospital, Oxford OX3 7LE, UK and Institute of Neuroscience of Physiology, Department of Physiology, Metabolic Research Unit, University of Göteborg, Box 430, SE-405 30 Göteborg, Sweden
| |
Collapse
|
8
|
Gan Q, Watanabe S. Synaptic Vesicle Endocytosis in Different Model Systems. Front Cell Neurosci 2018; 12:171. [PMID: 30002619 PMCID: PMC6031744 DOI: 10.3389/fncel.2018.00171] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 06/01/2018] [Indexed: 11/13/2022] Open
Abstract
Neurotransmission in complex animals depends on a choir of functionally distinct synapses releasing neurotransmitters in a highly coordinated manner. During synaptic signaling, vesicles fuse with the plasma membrane to release their contents. The rate of vesicle fusion is high and can exceed the rate at which synaptic vesicles can be re-supplied by distant sources. Thus, local compensatory endocytosis is needed to replenish the synaptic vesicle pools. Over the last four decades, various experimental methods and model systems have been used to study the cellular and molecular mechanisms underlying synaptic vesicle cycle. Clathrin-mediated endocytosis is thought to be the predominant mechanism for synaptic vesicle recycling. However, recent studies suggest significant contribution from other modes of endocytosis, including fast compensatory endocytosis, activity-dependent bulk endocytosis, ultrafast endocytosis, as well as kiss-and-run. Currently, it is not clear whether a universal model of vesicle recycling exist for all types of synapses. It is possible that each synapse type employs a particular mode of endocytosis. Alternatively, multiple modes of endocytosis operate at the same synapse, and the synapse toggles between different modes depending on its activity level. Here we compile review and research articles based on well-characterized model systems: frog neuromuscular junctions, C. elegans neuromuscular junctions, Drosophila neuromuscular junctions, lamprey reticulospinal giant axons, goldfish retinal ribbon synapses, the calyx of Held, and rodent hippocampal synapses. We will compare these systems in terms of their known modes and kinetics of synaptic vesicle endocytosis, as well as the underlying molecular machineries. We will also provide the future development of this field.
Collapse
Affiliation(s)
- Quan Gan
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| |
Collapse
|
9
|
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.
Collapse
Affiliation(s)
- Xuelin Lou
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| |
Collapse
|
10
|
Chang HF, Mannebach S, Beck A, Ravichandran K, Krause E, Frohnweiler K, Fecher-Trost C, Schirra C, Pattu V, Flockerzi V, Rettig J. Cytotoxic granule endocytosis depends on the Flower protein. J Cell Biol 2018; 217:667-683. [PMID: 29288152 PMCID: PMC5800809 DOI: 10.1083/jcb.201706053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 11/09/2017] [Accepted: 11/29/2017] [Indexed: 12/23/2022] Open
Abstract
Cytotoxic T lymphocytes (CTLs) kill target cells by the regulated release of cytotoxic substances from granules at the immunological synapse. To kill multiple target cells, CTLs use endocytosis of membrane components of cytotoxic granules. We studied the potential calcium dependence of endocytosis in mouse CTLs on Flower, which mediates the calcium dependence of synaptic vesicle endocytosis in Drosophila melanogaster Flower is predominantly localized on intracellular vesicles that move to the synapse on target cell contact. Endocytosis is entirely blocked at an early stage in Flower-deficient CTLs and is rescued to wild-type level by reintroducing Flower or by raising extracellular calcium. A Flower mutant lacking binding sites for the endocytic adaptor AP-2 proteins fails to rescue endocytosis, indicating that Flower interacts with proteins of the endocytic machinery to mediate granule endocytosis. Thus, our data identify Flower as a key protein mediating granule endocytosis.
Collapse
Affiliation(s)
- Hsin-Fang Chang
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Stefanie Mannebach
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Andreas Beck
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
- Center of Human and Molecular Biology, Saarland University, Homburg, Germany
| | - Keerthana Ravichandran
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Elmar Krause
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Katja Frohnweiler
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Claudia Fecher-Trost
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Claudia Schirra
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Varsha Pattu
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Veit Flockerzi
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| |
Collapse
|
11
|
Maritzen T, Haucke V. Coupling of exocytosis and endocytosis at the presynaptic active zone. Neurosci Res 2018; 127:45-52. [DOI: 10.1016/j.neures.2017.09.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/13/2017] [Accepted: 08/25/2017] [Indexed: 01/08/2023]
|
12
|
Yao CK, Liu YT, Lee IC, Wang YT, Wu PY. A Ca2+ channel differentially regulates Clathrin-mediated and activity-dependent bulk endocytosis. PLoS Biol 2017; 15:e2000931. [PMID: 28414717 PMCID: PMC5393565 DOI: 10.1371/journal.pbio.2000931] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 03/21/2017] [Indexed: 11/19/2022] Open
Abstract
Clathrin-mediated endocytosis (CME) and activity-dependent bulk endocytosis (ADBE) are two predominant forms of synaptic vesicle (SV) endocytosis, elicited by moderate and strong stimuli, respectively. They are tightly coupled with exocytosis for sustained neurotransmission. However, the underlying mechanisms are ill defined. We previously reported that the Flower (Fwe) Ca2+ channel present in SVs is incorporated into the periactive zone upon SV fusion, where it triggers CME, thus coupling exocytosis to CME. Here, we show that Fwe also promotes ADBE. Intriguingly, the effects of Fwe on CME and ADBE depend on the strength of the stimulus. Upon mild stimulation, Fwe controls CME independently of Ca2+ channeling. However, upon strong stimulation, Fwe triggers a Ca2+ influx that initiates ADBE. Moreover, knockout of rodent fwe in cultured rat hippocampal neurons impairs but does not completely abolish CME, similar to the loss of Drosophila fwe at the neuromuscular junction, suggesting that Fwe plays a regulatory role in regulating CME across species. In addition, the function of Fwe in ADBE is conserved at mammalian central synapses. Hence, Fwe exerts different effects in response to different stimulus strengths to control two major modes of endocytosis.
Collapse
Affiliation(s)
- Chi-Kuang Yao
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
- Neuroscience Program in Academia Sinica, Academia Sinica, Nankang, Taipei, Taiwan
- Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan
- * E-mail:
| | - Yu-Tzu Liu
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - I-Chi Lee
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - You-Tung Wang
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - Ping-Yen Wu
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| |
Collapse
|
13
|
Xie Z, Long J, Liu J, Chai Z, Kang X, Wang C. Molecular Mechanisms for the Coupling of Endocytosis to Exocytosis in Neurons. Front Mol Neurosci 2017; 10:47. [PMID: 28348516 PMCID: PMC5346583 DOI: 10.3389/fnmol.2017.00047] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 02/10/2017] [Indexed: 11/13/2022] Open
Abstract
Neuronal communication and brain function mainly depend on the fundamental biological events of neurotransmission, including the exocytosis of presynaptic vesicles (SVs) for neurotransmitter release and the subsequent endocytosis for SV retrieval. Neurotransmitters are released through the Ca2+- and SNARE-dependent fusion of SVs with the presynaptic plasma membrane. Following exocytosis, endocytosis occurs immediately to retrieve SV membrane and fusion machinery for local recycling and thus maintain the homeostasis of synaptic structure and sustained neurotransmission. Apart from the general endocytic machinery, recent studies have also revealed the involvement of SNARE proteins (synaptobrevin, SNAP25 and syntaxin), synaptophysin, Ca2+/calmodulin, and members of the synaptotagmin protein family (Syt1, Syt4, Syt7 and Syt11) in the balance and tight coupling of exo-endocytosis in neurons. Here, we provide an overview of recent progress in understanding how these neuron-specific adaptors coordinate to ensure precise and efficient endocytosis during neurotransmission.
Collapse
Affiliation(s)
- Zhenli Xie
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China; State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
| | - Jiangang Long
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China
| | - Jiankang Liu
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China
| | - Zuying Chai
- State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
| | - Xinjiang Kang
- State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China; College of Life Sciences, Liaocheng UniversityLiaocheng, China; Key Laboratory of Medical Electrophysiology, Ministry of Education of China, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical UniversityLuzhou, China
| | - Changhe Wang
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China; State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
| |
Collapse
|
14
|
The structure and function of presynaptic endosomes. Exp Cell Res 2015; 335:172-9. [DOI: 10.1016/j.yexcr.2015.04.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 04/23/2015] [Indexed: 11/19/2022]
|
15
|
Structure, Distribution, and Function of Neuronal/Synaptic Spinules and Related Invaginating Projections. Neuromolecular Med 2015; 17:211-40. [PMID: 26007200 DOI: 10.1007/s12017-015-8358-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 05/08/2015] [Indexed: 10/23/2022]
Abstract
Neurons and especially their synapses often project long thin processes that can invaginate neighboring neuronal or glial cells. These "invaginating projections" can occur in almost any combination of postsynaptic, presynaptic, and glial processes. Invaginating projections provide a precise mechanism for one neuron to communicate or exchange material exclusively at a highly localized site on another neuron, e.g., to regulate synaptic plasticity. The best-known types are postsynaptic projections called "spinules" that invaginate into presynaptic terminals. Spinules seem to be most prevalent at large very active synapses. Here, we present a comprehensive review of all kinds of invaginating projections associated with both neurons in general and more specifically with synapses; we describe them in all animals including simple, basal metazoans. These structures may have evolved into more elaborate structures in some higher animal groups exhibiting greater synaptic plasticity. In addition to classic spinules and filopodial invaginations, we describe a variety of lesser-known structures such as amphid microvilli, spinules in giant mossy terminals and en marron/brush synapses, the highly specialized fish retinal spinules, the trophospongium, capitate projections, and fly gnarls, as well as examples in which the entire presynaptic or postsynaptic process is invaginated. These various invaginating projections have evolved to modify the function of a particular synapse, or to channel an effect to one specific synapse or neuron, without affecting those nearby. We discuss how they function in membrane recycling, nourishment, and cell signaling and explore how they might change in aging and disease.
Collapse
|
16
|
Watanabe S, Trimbuch T, Camacho-Pérez M, Rost BR, Brokowski B, Söhl-Kielczynski B, Felies A, Davis MW, Rosenmund C, Jorgensen EM. Clathrin regenerates synaptic vesicles from endosomes. Nature 2014; 515:228-33. [PMID: 25296249 PMCID: PMC4291189 DOI: 10.1038/nature13846] [Citation(s) in RCA: 203] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 09/03/2014] [Indexed: 12/22/2022]
Abstract
Ultrafast endocytosis can retrieve a single, large endocytic vesicle as fast as 50-100 ms after synaptic vesicle fusion. However, the fate of the large endocytic vesicles is not known. Here we demonstrate that these vesicles transition to a synaptic endosome about one second after stimulation. The endosome is resolved into coated vesicles after 3 s, which in turn become small-diameter synaptic vesicles 5-6 s after stimulation. We disrupted clathrin function using RNA interference (RNAi) and found that clathrin is not required for ultrafast endocytosis but is required to generate synaptic vesicles from the endosome. Ultrafast endocytosis fails when actin polymerization is disrupted, or when neurons are stimulated at room temperature instead of physiological temperature. In the absence of ultrafast endocytosis, synaptic vesicles are retrieved directly from the plasma membrane by clathrin-mediated endocytosis. These results may explain discrepancies among published experiments concerning the role of clathrin in synaptic vesicle endocytosis.
Collapse
Affiliation(s)
- Shigeki Watanabe
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah 84112-0840, USA
| | - Thorsten Trimbuch
- Neuroscience Research Center Charité Universitätsmedizin Berlin, Berlin 10117, Germany
| | - Marcial Camacho-Pérez
- Neuroscience Research Center Charité Universitätsmedizin Berlin, Berlin 10117, Germany
| | - Benjamin R Rost
- 1] Neuroscience Research Center Charité Universitätsmedizin Berlin, Berlin 10117, Germany [2] German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - Bettina Brokowski
- Neuroscience Research Center Charité Universitätsmedizin Berlin, Berlin 10117, Germany
| | | | - Annegret Felies
- Neuroscience Research Center Charité Universitätsmedizin Berlin, Berlin 10117, Germany
| | - M Wayne Davis
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah 84112-0840, USA
| | - Christian Rosenmund
- Neuroscience Research Center Charité Universitätsmedizin Berlin, Berlin 10117, Germany
| | - Erik M Jorgensen
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah 84112-0840, USA
| |
Collapse
|
17
|
Bulk endocytosis at neuronal synapses. SCIENCE CHINA-LIFE SCIENCES 2014; 57:378-83. [DOI: 10.1007/s11427-014-4636-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 02/24/2014] [Indexed: 12/16/2022]
|
18
|
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.
Collapse
Affiliation(s)
- Jennifer R Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
| | | | | | | |
Collapse
|
19
|
Abstract
Neurons use a calcium-dependent mechanism to optimize the rate at which synaptic vesicles are recycled.
Collapse
Affiliation(s)
- Melissa A Herman
- is at Neurocure NWFZ , Charité Universitätsmedizin Berlin , Berlin , Germany
| | | |
Collapse
|
20
|
Ovsepian SV, Antyborzec I, O'Leary VB, Zaborszky L, Herms J, Oliver Dolly J. Neurotrophin receptor p75 mediates the uptake of the amyloid beta (Aβ) peptide, guiding it to lysosomes for degradation in basal forebrain cholinergic neurons. Brain Struct Funct 2013; 219:1527-41. [PMID: 23716278 DOI: 10.1007/s00429-013-0583-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 05/15/2013] [Indexed: 12/12/2022]
Abstract
A fascinating yet perhaps overlooked trait of the p75 neurotrophin receptor (p75(NTR)) is its ability to bind ligands with no obvious neurotrophic function. Using cultured basal forebrain (BF) neurons, this study demonstrates selective internalization of amyloid β (Aβ) 1-42 in conjunction with p75(NTR) (labelled with IgG192-Cy3) by cholinergic cells. Active under resting conditions, this process was enhanced by high K(+) stimulation and was insensitive to inhibitors of regulated synaptic activity-tetrodotoxin or botulinum neurotoxins (BoNT type/A and/B). Blockade of sarco-endoplasmic reticulum (SERCA) Ca(2+) ATPase with thapsigargin and CPA or chelation of Ca(2+) with EGTA-AM strongly suppressed the endocytosis of p75(NTR), implicating the role of ER released Ca(2+). The uptake of IgG192-Cy3 was also reduced by T-type Ca(2+) channel blocker mibefradil but not Cd(2+), an indiscriminate blocker of high voltage-activated Ca(2+) currents. A strong co-localization of IgG192-Cy3 with late endosome (Rab7) or lysosome (Lamp1) qualifier proteins suggest these compartments as the primary destination for internalized IgG192 and Aβ. Selective uptake and labeling of BF cholinergic cells with IgG192-Cy3 injected into the prefrontal cortex was verified also in vivo. The significance of these findings in relation to Aβ clearance in the cerebral cortex and pathophysiology of Alzheimer's disease is discussed.
Collapse
Affiliation(s)
- Saak V Ovsepian
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Republic of Ireland,
| | | | | | | | | | | |
Collapse
|
21
|
Morgan JR, Jiang J, Oliphint PA, Jin S, Gimenez LE, Busch DJ, Foldes AE, Zhuo Y, Sousa R, Lafer EM. A role for an Hsp70 nucleotide exchange factor in the regulation of synaptic vesicle endocytosis. J Neurosci 2013; 33:8009-21. [PMID: 23637191 PMCID: PMC3707978 DOI: 10.1523/jneurosci.4505-12.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 03/20/2013] [Accepted: 03/29/2013] [Indexed: 12/28/2022] Open
Abstract
Neurotransmission requires a continuously available pool of synaptic vesicles (SVs) that can fuse with the plasma membrane and release their neurotransmitter contents upon stimulation. After fusion, SV membranes and membrane proteins are retrieved from the presynaptic plasma membrane by clathrin-mediated endocytosis. After the internalization of a clathrin-coated vesicle, the vesicle must uncoat to replenish the pool of SVs. Clathrin-coated vesicle uncoating requires ATP and is mediated by the ubiquitous molecular chaperone Hsc70. In vitro, depolymerized clathrin forms a stable complex with Hsc70*ADP. This complex can be dissociated by nucleotide exchange factors (NEFs) that release ADP from Hsc70, allowing ATP to bind and induce disruption of the clathrin:Hsc70 association. Whether NEFs generally play similar roles in vesicle trafficking in vivo and whether they play such roles in SV endocytosis in particular is unknown. To address this question, we used information from recent structural and mechanistic studies of Hsp70:NEF and Hsp70:co-chaperone interactions to design a NEF inhibitor. Using acute perturbations at giant reticulospinal synapses of the sea lamprey (Petromyzon marinus), we found that this NEF inhibitor inhibited SV endocytosis. When this inhibitor was mutated so that it could no longer bind and inhibit Hsp110 (a NEF that we find to be highly abundant in brain cytosol), its ability to inhibit SV endocytosis was eliminated. These observations indicate that the action of a NEF, most likely Hsp110, is normally required during SV trafficking to release clathrin from Hsc70 and make it available for additional rounds of endocytosis.
Collapse
Affiliation(s)
- Jennifer R. Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Jianwen Jiang
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Paul A. Oliphint
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Suping Jin
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Luis E. Gimenez
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - David J. Busch
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Andrea E. Foldes
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Yue Zhuo
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Rui Sousa
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Eileen M. Lafer
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| |
Collapse
|
22
|
Zakharov AV, Petrov AM, Kotov NV, Zefirov AL. Experimental and modeling investigation of the mechanism of synaptic vesicles recycling. Biophysics (Nagoya-shi) 2012. [DOI: 10.1134/s0006350912040203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
23
|
Abstract
Neurons can sustain high rates of synaptic transmission without exhausting their supply of synaptic vesicles. This property relies on a highly efficient local endocytic recycling of synaptic vesicle membranes, which can be reused for hundreds, possibly thousands, of exo-endocytic cycles. Morphological, physiological, molecular, and genetic studies over the last four decades have provided insight into the membrane traffic reactions that govern this recycling and its regulation. These studies have shown that synaptic vesicle endocytosis capitalizes on fundamental and general endocytic mechanisms but also involves neuron-specific adaptations of such mechanisms. Thus, investigations of these processes have advanced not only the field of synaptic transmission but also, more generally, the field of endocytosis. This article summarizes current information on synaptic vesicle endocytosis with an emphasis on the underlying molecular mechanisms and with a special focus on clathrin-mediated endocytosis, the predominant pathway of synaptic vesicle protein internalization.
Collapse
Affiliation(s)
- Yasunori Saheki
- Department of Cell Biology, Howard Hughes Medical Institute and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06510, USA
| | | |
Collapse
|
24
|
Selvi RB, Chatterjee S, Jagadeesan D, Chaturbedy P, Suma BS, Eswaramoorthy M, Kundu TK. ATP driven clathrin dependent entry of carbon nanospheres prefer cells with glucose receptors. J Nanobiotechnology 2012; 10:35. [PMID: 22857258 PMCID: PMC3479219 DOI: 10.1186/1477-3155-10-35] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 06/20/2012] [Indexed: 11/21/2022] Open
Abstract
Background Intrinsically fluorescent glucose derived carbon nanospheres (CSP) efficiently enter mammalian cells and also cross the blood brain barrier (BBB). However, the mechanistic details of CSP entry inside mammalian cells and its specificity are not known. Results In this report, the biochemical and cellular mechanism of CSP entry into the living cell have been investigated. By employing confocal imaging we show that CSP entry into the mammalian cells is an ATP-dependent clathrin mediated endocytosis process. Zeta potential studies suggest that it has a strong preference for cells which possess high levels of glucose transporters such as the glial cells, thereby enabling it to target individual organs/tissues such as the brain with increased specificity. Conclusion The endocytosis of Glucose derived CSP into mammalian cells is an ATP dependent process mediated by clathrin coated pits. CSPs utilize the surface functional groups to target cells containing glucose transporters on its membrane thereby implicating a potential application for specific targeting of the brain or cancer cells.
Collapse
Affiliation(s)
- Ruthrotha B Selvi
- Transcription and Disease Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O, Bangalore 560 064, India
| | | | | | | | | | | | | |
Collapse
|
25
|
Xue L, Zhang Z, McNeil BD, Luo F, Wu XS, Sheng J, Shin W, Wu LG. Voltage-dependent calcium channels at the plasma membrane, but not vesicular channels, couple exocytosis to endocytosis. Cell Rep 2012; 1:632-8. [PMID: 22813738 DOI: 10.1016/j.celrep.2012.04.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 02/21/2012] [Accepted: 04/11/2012] [Indexed: 01/01/2023] Open
Abstract
Although calcium influx triggers endocytosis at many synapses and non-neuronal secretory cells, the identity of the calcium channel is unclear. The plasma membrane voltage-dependent calcium channel (VDCC) is a candidate, and it was recently proposed that exocytosis transiently inserts vesicular calcium channels at the plasma membrane, thus triggering endocytosis and coupling it to exocytosis, a mechanism suggested to be conserved from sea urchin to human. Here, we report that the vesicular membrane, when inserted into the plasma membrane upon exocytosis, does not generate a calcium current or calcium increase at a mammalian nerve terminal. Instead, VDCCs at the plasma membrane, including the P/Q-type, provide the calcium influx to trigger rapid and slow endocytosis and, thus, couple endocytosis to exocytosis. These findings call for reconsideration of the vesicular calcium channel hypothesis. They are likely to apply to many synapses and non-neuronal cells in which VDCCs control exocytosis, and exocytosis is coupled to endocytosis.
Collapse
Affiliation(s)
- Lei Xue
- National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | | | | | | | | | | | | | | |
Collapse
|
26
|
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]
|
27
|
Abstract
The role of Ca²⁺ in synaptic vesicle endocytosis remains uncertain due to the diversity in various preparations where several forms of endocytosis may contribute variably in different conditions. Although recent studies have demonstrated that Ca²⁺ is important for clathrin-mediated endocytosis (CME), the mechanistic role of Ca²⁺ in CME remains to be elucidated. By monitoring CME of single vesicles in mouse chromaffin cells with cell-attached capacitance measurements that offer millisecond time resolution, we demonstrate that the dynamics of vesicle fission during CME is Ca²⁺ dependent but becomes Ca²⁺ independent in synaptotagmin 1 (Syt1) knock-out cells. Our results thus suggest that Syt1 is necessary for the Ca²⁺ dependence of CME.
Collapse
|
28
|
Abstract
Eps15 homology domain-containing proteins (EHDs) are conserved ATPases implicated in membrane remodeling. Recently, EHD1 was found to be enriched at synaptic release sites, suggesting a possible involvement in the trafficking of synaptic vesicles. We have investigated the role of an EHD1/3 ortholog (l-EHD) in the lamprey giant reticulospinal synapse. l-EHD was detected by immunogold at endocytic structures adjacent to release sites. In antibody microinjection experiments, perturbation of l-EHD inhibited synaptic vesicle endocytosis and caused accumulation of clathrin-coated pits with atypical, elongated necks. The necks were covered with helix-like material containing dynamin. To test whether l-EHD directly interferes with dynamin function, we used fluid-supported bilayers as in vitro assay. We found that l-EHD strongly inhibited vesicle budding induced by dynamin in the constant presence of GTP. l-EHD also inhibited dynamin-induced membrane tubulation in the presence of GTPγS, a phenomenon linked with dynamin helix assembly. Our in vivo results demonstrate the involvement of l-EHD in clathrin/dynamin-dependent synaptic vesicle budding. Based on our in vitro observations, we suggest that l-EHD acts to limit the formation of long, unproductive dynamin helices, thereby promoting vesicle budding.
Collapse
|
29
|
Xiong W, Liu T, Wang Y, Chen X, Sun L, Guo N, Zheng H, Zheng L, Ruat M, Han W, Zhang CX, Zhou Z. An inhibitory effect of extracellular Ca2+ on Ca2+-dependent exocytosis. PLoS One 2011; 6:e24573. [PMID: 22028769 PMCID: PMC3196490 DOI: 10.1371/journal.pone.0024573] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Accepted: 08/14/2011] [Indexed: 11/21/2022] Open
Abstract
Aim Neurotransmitter release is elicited by an elevation of intracellular Ca2+ concentration ([Ca2+]i). The action potential triggers Ca2+ influx through Ca2+ channels which causes local changes of [Ca2+]i for vesicle release. However, any direct role of extracellular Ca2+ (besides Ca2+ influx) on Ca2+-dependent exocytosis remains elusive. Here we set out to investigate this possibility on rat dorsal root ganglion (DRG) neurons and chromaffin cells, widely used models for studying vesicle exocytosis. Results Using photolysis of caged Ca2+ and caffeine-induced release of stored Ca2+, we found that extracellular Ca2+ inhibited exocytosis following moderate [Ca2+]i rises (2–3 µM). The IC50 for extracellular Ca2+ inhibition of exocytosis (ECIE) was 1.38 mM and a physiological reduction (∼30%) of extracellular Ca2+ concentration ([Ca2+]o) significantly increased the evoked exocytosis. At the single vesicle level, quantal size and release frequency were also altered by physiological [Ca2+]o. The calcimimetics Mg2+, Cd2+, G418, and neomycin all inhibited exocytosis. The extracellular Ca2+-sensing receptor (CaSR) was not involved because specific drugs and knockdown of CaSR in DRG neurons did not affect ECIE. Conclusion/Significance As an extension of the classic Ca2+ hypothesis of synaptic release, physiological levels of extracellular Ca2+ play dual roles in evoked exocytosis by providing a source of Ca2+ influx, and by directly regulating quantal size and release probability in neuronal cells.
Collapse
Affiliation(s)
- Wei Xiong
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Tao Liu
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Yeshi Wang
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Xiaowei Chen
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Lei Sun
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Ning Guo
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Hui Zheng
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Lianghong Zheng
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Martial Ruat
- CNRS, UPR9040, Institut de Neurobiologie Alfred Fessard-IFR 2118, Gif sur Yvette, France
| | - Weiping Han
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, Agency for Science, Technology, and Research, Singapore, Singapore
| | - Claire Xi Zhang
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
- * E-mail: (ZZ); (CXZ)
| | - Zhuan Zhou
- State Key Laboratory of Biomembrane Engineering and Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China
- * E-mail: (ZZ); (CXZ)
| |
Collapse
|
30
|
Protein scaffolds in the coupling of synaptic exocytosis and endocytosis. Nat Rev Neurosci 2011; 12:127-38. [DOI: 10.1038/nrn2948] [Citation(s) in RCA: 204] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
31
|
Cárdenas AM, Marengo FD. Rapid endocytosis and vesicle recycling in neuroendocrine cells. Cell Mol Neurobiol 2010; 30:1365-70. [PMID: 21046457 DOI: 10.1007/s10571-010-9579-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 09/02/2010] [Indexed: 11/29/2022]
Abstract
Endocytosis is a crucial process for neuroendocrine cells that ensures membrane homeostasis, vesicle recycling, and hormone release reliability. Different endocytic mechanisms have been described in chromaffin cells, such as clathrin-dependent slow endocytosis and clathrin-independent rapid endocytosis. Rapid endocytosis, classically measured in terms of a fast decrease in membrane capacitance, exhibits two different forms, "rapid compensatory endocytosis" and "excess retrieval." While excess retrieval seems to be associated with formation of long-lasting endosomes, rapid compensatory endocytosis is well correlated with exocytotic activity, and it is regarded as a mechanism associated to rapid vesicle recycling during normal secretory activity. It has been suggested that rapid compensatory endocytosis may be related to the prevalence of a transient fusion mode of exo-endocytosis. In the latter mode, the fusion pore, a nanometric-sized channel formed at the onset of exocytosis, remains open for a few hundred milliseconds and later abruptly closes, releasing a small amount of transmitters. By this mechanism, endocrine cell selectively releases low molecular weight transmitters, and rapidly recycles the secretory vesicles. In this article, we discuss the cellular and molecular mechanisms that define the different forms of exocytosis and endocytosis and their impact on vesicle recycling pathways.
Collapse
Affiliation(s)
- Ana María Cárdenas
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaiso, Chile
| | | |
Collapse
|
32
|
Vos M, Lauwers E, Verstreken P. Synaptic mitochondria in synaptic transmission and organization of vesicle pools in health and disease. Front Synaptic Neurosci 2010; 2:139. [PMID: 21423525 PMCID: PMC3059669 DOI: 10.3389/fnsyn.2010.00139] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 08/09/2010] [Indexed: 12/21/2022] Open
Abstract
Cell types rich in mitochondria, including neurons, display a high energy demand and a need for calcium buffering. The importance of mitochondria for proper neuronal function is stressed by the occurrence of neurological defects in patients suffering from a great variety of diseases caused by mutations in mitochondrial genes. Genetic and pharmacological evidence also reveal a role of these organelles in various aspects of neuronal physiology and in the pathogenesis of neurodegenerative disorders. Yet the mechanisms by which mitochondria can affect neurotransmission largely remain to be elucidated. In this review we focus on experimental data that suggest a critical function of synaptic mitochondria in the function and organization of synaptic vesicle pools, and in neurotransmitter release during intense neuronal activity. We discuss how calcium handling, ATP production and other mitochondrial mechanisms may influence synaptic vesicle pool organization and synaptic function. Given the link between synaptic mitochondrial function and neuronal communication, efforts toward better understanding mitochondrial biology may lead to novel therapeutic approaches of neurological disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and psychiatric disorders that are at least in part caused by mitochondrial deficits.
Collapse
Affiliation(s)
- Melissa Vos
- Department of Molecular and Developmental Genetics VIB, Leuven, Belgium
| | | | | |
Collapse
|
33
|
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.
Collapse
|
34
|
Abstract
Synaptic vesicle 2 (SV2) proteins, critical for proper nervous system function, are implicated in human epilepsy, yet little is known about their function. We demonstrate, using direct approaches, that loss of the major SV2 isoform in a central nervous system nerve terminal is associated with an elevation in both resting and evoked presynaptic Ca(2+) signals. This increase is essential for the expression of the SV2B(-/-) secretory phenotype, characterized by changes in synaptic vesicle dynamics, synaptic plasticity, and synaptic strength. Short-term reproduction of the Ca(2+) phenotype in wild-type nerve terminals reproduces almost all aspects of the SV2B(-/-) secretory phenotype, while rescue of the Ca(2+) phenotype in SV2B(-/-) neurons relieves every facet of the SV2B(-/-) secretory phenotype. Thus, SV2 controls key aspects of synaptic functionality via its ability to regulate presynaptic Ca(2+), suggesting a potential new target for therapeutic intervention in the treatment of epilepsy.
Collapse
|
35
|
Kuromi H, Ueno K, Kidokoro Y. Two types of Ca2+ channel linked to two endocytic pathways coordinately maintain synaptic transmission at the Drosophila synapse. Eur J Neurosci 2010; 32:335-46. [DOI: 10.1111/j.1460-9568.2010.07300.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
|
36
|
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.
Collapse
|
37
|
Preferred sites of exocytosis and endocytosis colocalize during high- but not lower-frequency stimulation in mouse motor nerve terminals. J Neurosci 2009; 29:15308-16. [PMID: 19955383 DOI: 10.1523/jneurosci.4646-09.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The spatial relationship of exocytosis and endocytosis in motor nerve terminals has been explored, with varied results, mostly in fixed preparations and without direct information on the utilization of each exocytic site. We sought to determine these spatial properties in real time using synaptopHluorin (spH) and FM4-64. Earlier we showed that nerve stimulation elicits the appearance of spH fluorescence hot spots, which mark preferred sites of exocytosis. Here we show that nerve stimulation in the presence of the styryl dye FM4-64 evokes hot spots of FM4-64 fluorescence. Their size, density, and rate of appearance are similar to the spH hot spots, but their rate of disappearance after stimulation was much slower (t(1/2) approximately 9 min vs approximately 10 s for spH hot spots), consistent with FM4-64 spots identifying bulk endocytosis and subsequent slow intracellular dispersion of nascent vesicles. Simultaneous imaging of both fluorophores revealed a strong colocalization of spH and FM4-64 spots, but only during high (100 Hz) stimulation. At 40 Hz stimulation, exocytic and endocytic spots did not colocalize. Our results are consistent with the hypothesis that hot spots of endocytosis, possibly in the form of bulk uptake, occur at or very near highly active exocytic sites during high-frequency stimulation.
Collapse
|
38
|
Abstract
Central nerve terminals release neurotransmitter in response to a wide variety of stimuli. Because maintenance of neurotransmitter release is dependent on the continual supply of synaptic vesicles (SVs), nerve terminals possess an array of endocytosis modes to retrieve and recycle SV membrane and proteins. During mild stimulation conditions, single SV retrieval modes such as clathrin-mediated endocytosis predominate. However, during increased neuronal activity, additional SV retrieval capacity is required, which is provided by activity-dependent bulk endocytosis (ADBE). ADBE is the dominant SV retrieval mechanism during elevated neuronal activity. It is a high capacity SV retrieval mode that is immediately triggered during such stimulation conditions. This review will summarize the current knowledge regarding the molecular mechanism of ADBE, including molecules required for its triggering and subsequent steps, including SV budding from bulk endosomes. The molecular relationship between ADBE and the SV reserve pool will also be discussed. It is becoming clear that an understanding of the molecular physiology of ADBE will be of critical importance in attempts to modulate both normal and abnormal synaptic function during intense neuronal activity.
Collapse
Affiliation(s)
- Emma L. Clayton
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD, Scotland, U.K
| | - Michael A. Cousin
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD, Scotland, U.K
| |
Collapse
|
39
|
Affiliation(s)
- Jeremy Dittman
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065; ,
| | - Timothy A. Ryan
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065; ,
| |
Collapse
|
40
|
Yao CK, Lin YQ, Ly CV, Ohyama T, Haueter CM, Moiseenkova-Bell VY, Wensel TG, Bellen HJ. A synaptic vesicle-associated Ca2+ channel promotes endocytosis and couples exocytosis to endocytosis. Cell 2009; 138:947-60. [PMID: 19737521 PMCID: PMC2749961 DOI: 10.1016/j.cell.2009.06.033] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Revised: 04/27/2009] [Accepted: 06/12/2009] [Indexed: 02/06/2023]
Abstract
Synaptic vesicle (SV) exo- and endocytosis are tightly coupled to sustain neurotransmission in presynaptic terminals, and both are regulated by Ca(2+). Ca(2+) influx triggered by voltage-gated Ca(2+) channels is necessary for SV fusion. However, extracellular Ca(2+) has also been shown to be required for endocytosis. The intracellular Ca(2+) levels (<1 microM) that trigger endocytosis are typically much lower than those (>10 microM) needed to induce exocytosis, and endocytosis is inhibited when the Ca(2+) level exceeds 1 microM. Here, we identify and characterize a transmembrane protein associated with SVs that, upon SV fusion, localizes at periactive zones. Loss of Flower results in impaired intracellular resting Ca(2+) levels and impaired endocytosis. Flower multimerizes and is able to form a channel to control Ca(2+) influx. We propose that Flower functions as a Ca(2+) channel to regulate synaptic endocytosis and hence couples exo- with endocytosis.
Collapse
Affiliation(s)
- Chi-Kuang Yao
- Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Hosoi N, Holt M, Sakaba T. Calcium dependence of exo- and endocytotic coupling at a glutamatergic synapse. Neuron 2009; 63:216-29. [PMID: 19640480 DOI: 10.1016/j.neuron.2009.06.010] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 05/13/2009] [Accepted: 06/08/2009] [Indexed: 01/01/2023]
Abstract
The mechanism coupling exocytosis and endocytosis remains to be elucidated at central synapses. Here, we show that the mechanism linking these two processes is dependent on microdomain-[Ca2+](i) similar to that which triggers exocytosis, as well as the exocytotic protein synaptobrevin/VAMP. Furthermore, block of endocytosis has a limited, retrograde action on exocytosis, delaying recruitment of release-ready vesicles and enhancing short-term depression. This effect sets in so rapidly that it cannot be explained by the nonavailability of recycled vesicles. Rather, we postulate that perturbation of a step linking exocytosis and endocytosis temporarily prevents new vesicles from docking at specialized sites for exocytosis.
Collapse
Affiliation(s)
- Nobutake Hosoi
- Independent Junior Research Group of Biophysics of Synaptic Transmission, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | | | | |
Collapse
|
42
|
Clayton EL, Cousin MA. Quantitative monitoring of activity-dependent bulk endocytosis of synaptic vesicle membrane by fluorescent dextran imaging. J Neurosci Methods 2009; 185:76-81. [PMID: 19766140 DOI: 10.1016/j.jneumeth.2009.09.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 09/08/2009] [Accepted: 09/09/2009] [Indexed: 11/20/2022]
Abstract
Activity-dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) retrieval mode in central nerve terminals during periods of intense neuronal activity. Despite this fact there are very few real time assays that report the activity of this critical SV retrieval mode. In this paper we report a simple and quantitative assay of ADBE using uptake of large flourescent dextrans as fluid phase markers. We show that almost all dextran uptake occurs in nerve terminals, using co-localisation with the fluorescent probe FM1-43. We also demonstrate that accumulated dextran cannot be unloaded by neuronal stimulation, indicating its specific loading into bulk endosomes and not SVs. Quantification of dextran uptake was achieved by using thresholding analysis to count the number of loaded nerve terminals, since monitoring the average fluorescence intensity of these nerve terminals did not accurately report the extent of ADBE. Using this analysis we showed that dextran uptake occurs very soon after stimulation and that it does not persist when stimulation terminates. Thus we have devised a simple and quantitative method to monitor ADBE in living neurones, which will be ideal for real time screening of small molecule inhibitors of this key SV retrieval mode.
Collapse
Affiliation(s)
- Emma Louise Clayton
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, Scotland, UK
| | | |
Collapse
|
43
|
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.
Collapse
|
44
|
Cousin MA. Activity-dependent bulk synaptic vesicle endocytosis--a fast, high capacity membrane retrieval mechanism. Mol Neurobiol 2009; 39:185-9. [PMID: 19266323 PMCID: PMC2871594 DOI: 10.1007/s12035-009-8062-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 02/18/2009] [Indexed: 10/21/2022]
Abstract
Central nerve terminals are placed under considerable stress during intense stimulation due to large numbers of synaptic vesicles (SVs) fusing with the plasma membrane. Classical clathrin-dependent SV endocytosis cannot correct for the large increase in nerve terminal surface area in the short term, due to its slow kinetics and low capacity. During such intense stimulation, an additional SV retrieval pathway is recruited called bulk endocytosis. Recent studies have shown that bulk endocytosis fulfils all of the physiological requirements to remedy the acute changes in nerve terminal surface area to allow the nerve terminal to continue to function. This review will summarise the recent developments in the field that characterise the physiology of bulk endocytosis which show that it is a fast, activity-dependent and high capacity mechanism that is essential for the function of central nerve terminals.
Collapse
Affiliation(s)
- M A Cousin
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
| |
Collapse
|
45
|
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]
|
46
|
Abstract
The ability to recycle synaptic vesicles is a crucial property of nerve terminals that allows maintenance of synaptic transmission. Using high-sensitivity optical approaches at hippocampal nerve terminals in dissociated neurons in culture, we show that modulation of endocytosis can be achieved by expansion of the endocytic capacity. Our experiments indicate that the endocytic capacity, the maximum number of synaptic vesicles that can be internalized in parallel at individual synapses, is tightly controlled by intracellular calcium levels. Increasing levels of intracellular calcium, which occurs as firing frequency increases, significantly increases the endocytic capacity. At physiological temperature after 30 Hz firing, these synapses are capable of endocytosing at least approximately 28 vesicles in parallel, each with a time constant of approximately 6 s. This calcium-dependent control of endocytic capacity reveals a potentially useful adaptive response to high-frequency activity to increase endocytic rates under conditions of vesicle pool depletion.
Collapse
|
47
|
Abstract
Bulk endocytosis in central nerve terminals is activated by strong stimulation; however, the speed at which it is initiated and for how long it persists is still a matter of debate. To resolve this issue, we performed a characterization of bulk endocytic retrieval using action potential trains of increasing intensity. Bulk endocytosis was monitored by the loading of the fluorescent dyes FM2-10 and FM1-43, uptake of tetramethylrhodamine-dextran (40 kDa), or morphological analysis of uptake of the fluid-phase marker horseradish peroxidase. When neuronal cultures were subjected to mild stimulation (200 action potentials at 10 Hz), bulk endocytosis was not observed using any of our assay systems. However, when more intense trains of action potentials (400 or 800 action potentials at 40 and 80 Hz, respectively) were applied to neurons, bulk endocytosis was activated immediately, with the majority of bulk endocytosis complete by the end of stimulation. This contrasts with single synaptic vesicle endocytosis, the majority of which occurred after stimulation was terminated. Thus, bulk endocytosis is a fast event that is triggered during strong stimulation and provides the nerve terminal with an appropriate mechanism to meet the demands of synaptic vesicle retrieval during periods of intense synaptic vesicle exocytosis.
Collapse
|
48
|
Perturbation of syndapin/PACSIN impairs synaptic vesicle recycling evoked by intense stimulation. J Neurosci 2008; 28:3925-33. [PMID: 18400891 DOI: 10.1523/jneurosci.1754-07.2008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptic vesicle recycling has been proposed to depend on proteins which coordinate membrane and cytoskeletal dynamics. Here, we examine the role of the dynamin- and N-WASP (neural Wiskott-Aldrich syndrome protein)-binding protein syndapin/PACSIN at the lamprey reticulospinal synapse. We find that presynaptic microinjection of syndapin antibodies inhibits vesicle recycling evoked by intense (5 Hz or more), but not by light (0.2 Hz) stimulation. This contrasts with the inhibition at light stimulation induced by perturbation of amphiphysin (Shupliakov et al., 1997). Inhibition by syndapin antibodies was associated with massive accumulation of membranous cisternae and invaginations around release sites, but not of coated pits at the plasma membrane. Cisternae contained vesicle membrane, as shown by vesicle-associated membrane protein 2 (VAMP2)/synaptobrevin 2 immunolabeling. Similar effects were observed when syndapin was perturbed before onset of massive endocytosis induced by preceding intense stimulation. Selective perturbation of the Src homology 3 domain interactions of syndapin was sufficient to induce vesicle depletion and accumulation of cisternae. Our data show an involvement of syndapin in synaptic vesicle recycling evoked by intense stimulation. We propose that syndapin is required to stabilize the plasma membrane and/or facilitate bulk endocytosis at high release rates.
Collapse
|
49
|
Abstract
Epsin has been suggested to act as an alternate adaptor in several endocytic pathways. Its role in synaptic vesicle recycling remains, however, unclear. Here, we examined the role of epsin in this process by using the lamprey reticulospinal synapse as a model system. We characterized a lamprey ortholog of epsin 1 and showed that it is accumulated at release sites at rest and also at clathrin-coated pits in the periactive zone during synaptic activity. Disruption of epsin interactions, by presynaptic microinjection of antibodies to either the epsin-N-terminal homology domain (ENTH) or the clathrin/AP2 binding region (CLAP), caused profound loss of vesicles in stimulated synapses. CLAP antibody-injected synapses displayed a massive accumulation of distorted coated structures, including coated vacuoles, whereas in synapses perturbed with ENTH antibodies, very few coated structures were found. In both cases coated pits on the plasma membrane showed a shift to early intermediates (shallow coated pits) and an increase in size. Moreover, in CLAP antibody-injected synapses flat clathrin-coated patches occurred on the plasma membrane. We conclude that epsin is involved in clathrin-mediated synaptic vesicle endocytosis. Our results support a model, based on in vitro studies, suggesting that epsin coordinates curvature generation with coat assembly and further indicating that epsin limits clathrin coat assembly to the size of newly formed vesicles. We propose that these functions of epsin 1 provide an additional mechanism for generation of uniformly sized synaptic vesicles.
Collapse
|
50
|
Santos MS, Li H, Voglmaier SM. Synaptic vesicle protein trafficking at the glutamate synapse. Neuroscience 2008; 158:189-203. [PMID: 18472224 DOI: 10.1016/j.neuroscience.2008.03.029] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 02/25/2008] [Accepted: 03/08/2008] [Indexed: 11/27/2022]
Abstract
Expression of the integral and associated proteins of synaptic vesicles is subject to regulation over time, by region, and in response to activity. The process by which changes in protein levels and isoforms result in different properties of neurotransmitter release involves protein trafficking to the synaptic vesicle. How newly synthesized proteins are incorporated into synaptic vesicles at the presynaptic bouton is poorly understood. During synaptogenesis, synaptic vesicle proteins sort through the secretory pathway and are transported down the axon in precursor vesicles that undergo maturation to form synaptic vesicles. Changes in protein content of synaptic vesicles could involve the formation of new vesicles that either mix with the previous complement of vesicles or replace them, presumably by their degradation or inactivation. Alternatively, new proteins could individually incorporate into existing synaptic vesicles, changing their functional properties. Glutamatergic vesicles likely express many of the same integral membrane proteins and share certain common mechanisms of biogenesis, recycling, and degradation with other synaptic vesicles. However, glutamatergic vesicles are defined by their ability to package glutamate for release, a property conferred by the expression of a vesicular glutamate transporter (VGLUT). VGLUTs are subject to regional, developmental, and activity-dependent changes in expression. In addition, VGLUT isoforms differ in their trafficking, which may target them to different pathways during biogenesis or after recycling, which may in turn sort them to different vesicle pools. Emerging data indicate that differences in the association of VGLUTs and other synaptic vesicle proteins with endocytic adaptors may influence their trafficking. These observations indicate that independent regulation of synaptic vesicle protein trafficking has the potential to influence synaptic vesicle protein composition, the maintenance of synaptic vesicle pools, and the release of glutamate in response to changing physiological requirements.
Collapse
Affiliation(s)
- M S Santos
- Department of Psychiatry, University of California School of Medicine, 401 Parnassus Avenue, LPPI-A101, San Francisco, CA 94143-0984, USA
| | | | | |
Collapse
|