Distinct domains of complexin I differentially regulate neurotransmitter release

Xue, Mingshan; Reim, Kerstin; Chen, Xiaocheng; Chao, Hsiao‐Tuan; Deng, Hui; Rizo, Josep; Brose, Nils; Rosenmund, Christian

doi:10.1038/nsmb1292

Cited by 213 publications

(429 citation statements)

References 39 publications

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“…2), which may act on SnARE complexes and on the membrane itself 12,26 . There are a number of other important regulators, including Ras-related Rab proteins and complexins 27 , that impose additional layers of control on the fusion process 13,23 .…”

Section: -2000 Neurotransmitter Moleculesmentioning

confidence: 99%

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

2011

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Communication between nerve cells largely occurs at chemical synapses -specialized sites of cell-cell contact where electrical signals trigger the exocytic release of neurotransmitter, which in turn activates postsynaptic receptor channels. The efficacy with which such chemical signals are transmitted is crucial for the functioning of the nervous system. Modulation of neurotransmission enables nerve cells to respond to a vast range of stimulus patterns. Synaptic activity can also be tremendously diverse; from the fast synapses of the hippocampus, to slow neuropeptide-containing synapses. Indeed, some signalling pathways are active in the absence of stimulation, such as those involved in the processing of sensory information, which transmit tonically at high rates of up to 100 Hz or more 1,2 .Intriguing questions arise from these facts, including how high rates of neurotransmission can be maintained over long periods of time, and what limits the ability of a given synapse to release neurotransmitter during sustained periods of activity. Recent data indicate that in many synapses, exocytosis of neurotransmitter is coupled to endocytosis, and that synapses have evolved a specialized apparatus of scaffolding proteins to comply with these demands. Such scaffolds aid the temporal and spatial coupling of exocytosis and endocytosis, and are crucial for maintaining rapid neurotransmission during sustained activity 3 .Exocytosis of neurotransmitter is triggered by stimulusinduced calcium influx into the nerve terminal 4,5 and the subsequent fusion of synaptic vesicles with the presynaptic plasma membrane at specialized regions called active zones (BOX 1). Exocytosed synaptic vesicle membrane proteins and lipids in turn are recycled at the endocytic or periactive zone (BOX 1) that surrounds the release site, to restore functional synaptic vesicle pools for reuse and to ensure long-term functionality of the synapse 6-8 (FIG. 1). Depending on the type of synapse and the stimulation frequency, several modes of endocytosis with different time constants -for example, fast and slow endocytosisseem to operate 7,9,10 . Clathrin-mediated endocytosis arguably represents the main pathway of synaptic vesicle endocytosis 6,8,11 , although other modes -for example, fast kiss-and-run exocytosis and endocytosis -could operate in parallel.Although the machineries for exocytic membrane fusion 12,13 and for endocytic retrieval of synaptic vesicle membranes have been studied separately in some detail 6,14 , comparatively little is known about the coupling between exocytosis and endocytosis. Here we synthesize recent data from physiological, morphological and biochemical studies in several model systems into hypothetical models for scaffold-based mechanisms underlying exocytic-endocytic coupling.The synaptic vesicle cycle Synaptic vesicle pools. Some defining features of chemical synapses are the presence of one or several clusters of synaptic vesicles in the presynaptic nerve terminal, and ultrastructural specializations at the pre-and postsy...

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Section: -2000 Neurotransmitter Moleculesmentioning

confidence: 99%

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

2011

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“…Although multiple approaches have revealed an essential role of complexin in synaptic fusion [7,[10][11][12][13][14][15], the nature of this role remains unclear. In vertebrate autapses, deletion of complexin selectively impairs fast synchronous neurotransmitter release without changing asynchronous or spontaneous release [7,10]. In in vitro fusion assays, conversely, addition of complexin causes a general block of SNARE-dependent fusion, indicating that complexin is a SNARE clamp [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…Complexin binds to SNARE complexes via its central α-helix, which inserts in an anti-parallel orientation into a groove formed by synaptobrevin/VAMP and syntaxin-1 [8,9]. Although multiple approaches have revealed an essential role of complexin in synaptic fusion [7,[10][11][12][13][14][15], the nature of this role remains unclear. In vertebrate autapses, deletion of complexin selectively impairs fast synchronous neurotransmitter release without changing asynchronous or spontaneous release [7,10].…”

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confidence: 99%

“…S4). Thus, the complexin knock-down greatly impaired fast synchronous but not asynchronous synaptic vesicle fusion, and increased spontaneous fusion, thereby reconciling the divergent phenotypes observed in vertebrate autapses, Drosophila neuromuscular junctions, and in vitro fusion assays [7,[10][11][12][13][14][15].We next examined which complexin sequences mediate spontaneous and evoked fusion (Fig. 1C).…”

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confidence: 99%

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Complexin Controls the Force Transfer from SNARE Complexes to Membranes in Fusion

Maximov

Tang

Yang

et al. 2009

Science

318

489

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Trans-SNARE complexes catalyze fast synaptic vesicle fusion and bind complexin, but the function of complexin binding to SNARE complexes remains unclear. Here we show that in neuronal synapses, complexin simultaneously suppressed spontaneous fusion and activated fast Ca 2+ -evoked fusion. The dual function of complexin required SNARE binding, and additionally involved distinct N-terminal sequences of complexin that localize to the point where trans-SNARE complexes insert into the fusing membranes, suggesting that complexin controls the force that trans-SNARE complexes apply onto the fusing membranes. Consistent with this hypothesis, a mutation in the membrane insertion sequence of the v-SNARE synaptobrevin/VAMP phenocopied the complexin loss-of-function state without impairing complexin-binding to SNARE complexes. Thus, complexin probably activates and clamps the force-transfer from assembled trans-SNARE complexes onto fusing membranes.Synaptic vesicle fusion is driven by assembly of trans-SNARE complexes (or SNAREpins) from syntaxin-1 and SNAP-25 on the plasma membrane, and synaptobrevin/ VAMP on the vesicle membrane [1][2][3]. Ca 2+ then triggers fast synchronous synaptic vesicle fusion by binding to the Ca 2+ -sensor synaptotagmin [4][5][6]. Besides SNARE proteins and synaptotagmin, fast Ca 2+ -triggered fusion requires complexin [7]. Complexin is composed of short N-and C-terminal sequences and two central α-helices. Complexin binds to SNARE complexes via its central α-helix, which inserts in an anti-parallel orientation into a groove formed by synaptobrevin/VAMP and syntaxin-1 [8,9]. Although multiple approaches have revealed an essential role of complexin in synaptic fusion [7,[10][11][12][13][14][15], the nature of this role remains unclear. In vertebrate autapses, deletion of complexin selectively impairs fast synchronous neurotransmitter release without changing asynchronous or spontaneous release [7,10]. In in vitro fusion assays, conversely, addition of complexin causes a general block of SNARE-dependent fusion, indicating that complexin is a SNARE clamp [11][12][13][14]. In Drosophila neuromuscular synapses, deletion of complexin produces a >20-fold increase in spontaneous release but only a small decrease in evoked release [15]. Thus, the role of complexin in fusion is unclear. Moreover, even the importance of complexin SNARE- [16,17]. Here we addressed these questions with two complementary approaches -RNAi-dependent knockdown of complexin with rescue, and replacing wild-type synaptobrevin with specific mutants using synaptobrevin knockout (KO) mice [18].We knocked down complexin expression in cultured cortical neurons using an shRNA that targets both complexin-1 and -2, the only complexin isoforms significantly expressed in these neurons [19]. For this purpose, we used lentiviruses that simultaneously synthesize the complexin shRNA and either GFP, wild-type complexin-1, or 4M-mutant complexin-1 that is unable to bind to SNARE complexes (19,20). Lentivirus expressing GFP without the shRNA ...

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“…23) Mutant (R59H) complexin I exhibits decreased binding to neuronal SNARE complexes. 24) Mutant (R59H) complexin II also exhibits reduced binding to SNARE complexes in mast cells. 20) Inhibitory effects of complexin II on SNAREmediated membrane fusion may depend on its interaction with SNARE complexes in mast cells.…”

Section: Discussionmentioning

confidence: 99%

Effect of Complexin II on Membrane Fusion between Liposomes Containing Mast Cell SNARE Proteins

Tadokoro

Hirashima

Utsunomiya‐Tate

2016

Biological & Pharmaceutical Bulletin

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Mast cells are involved in allergic responses and undergo exocytotic release of inflammatory mediators in response to antigen stimulation. Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are involved in this membrane fusion process; some SNARE-binding proteins regulate SNARE-dependent liposome membrane fusion. SNARE-binding protein complexin II is expressed in mast cells, where it positively regulates exocytotic release after antigen stimulation. We found that complexin II suppressed SNARE-dependent membrane fusion between mast cell SNARE-containing liposomes. This inhibitory effect of complexin II was abolished when we used a structurally divergent mutant (R59H) complexin II, where Arg59 is substituted with histidine. These results suggest that complexin II negatively regulates SNARE-dependent exocytotic membrane fusion in mast cells, and this inhibitory effect is dependent upon Arg59.Key words mast cell; exocytosis; membrane fusion; soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE); degranulation Mast cells are involved in allergic reactions. Cross-linking of FcεRI, the high-affinity receptor for the Fc region of immunoglobulin E, by multivalent antigens increases intracellular Ca 2+ concentration, causing exocytotic inflammatory mediator release from mast cells. 1) Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are involved in this process. 2-9) SNARE-binding proteins also regulate exocytotic release in mast cells. 9,10) Syntaxin-3, -4 and synaptosomal-associated protein 23 kDa (SNAP-23) are SNARE proteins on the plasma membrane (t-SNARE) in mast cells. 2-4) Vesicle associated membrane protein (VAMP)-2, -7, and -8 are SNARE proteins on the secretory vesicles membrane (v-SNARE). 3,4) These t-SNARE and v-SNARE interact with each other and form SNARE complex which induce exocytotic release. [4][5][6] Final stage of exocytosis is membrane fusion process between secretory granule membrane and plasma membrane. SNAP-23/syntaxin-3 or SANP23/syntaxin-4 incorporated liposomes fuse with VAMP-8 but not VAMP-7 incorporated liposomes. 11)Complexins possess an α-helix in their central region that binds to and regulates SNAREs. 12) Complexins I and II are expressed in neuronal cells and may be involved in neurotransmitter release. 13,14) Complexin affects neuronal SNARE-mediated membrane fusion between liposomes. 15,16) Complexin II, but not complexin I, is expressed in mast cells, and exocytotic release after antigen stimulation is suppressed in mast cells where complexin II has been knocked down. 10) To elucidate the molecular mechanism of SNARE-dependent exocytosis in mast cells, we examined effects of complexin II on mast cell SNARE-dependent liposomal membrane fusion that is a simple assay system without other factors derived from cells. 11,[17][18][19] MATERIALS AND METHODS Protein Expression and PurificationFull-length rat syntaxin-3, SNAP-23, VAMP-2 or -8, and complexin II were expressed in Escherichia coli (E....

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Distinct domains of complexin I differentially regulate neurotransmitter release

Cited by 213 publications

References 39 publications

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

Complexin Controls the Force Transfer from SNARE Complexes to Membranes in Fusion

Effect of Complexin II on Membrane Fusion between Liposomes Containing Mast Cell SNARE Proteins

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