Calmodulin Mediates Rapid Recruitment of Fast-Releasing Synaptic Vesicles at a Calyx-Type Synapse

Sakaba, Takeshi; Neher, Erwin

doi:10.1016/s0896-6273(01)00543-8

Cited by 337 publications

(545 citation statements)

References 78 publications

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“…Although the CaM-binding sites of myosin-Va and CaMKII are distinct (Bähler and Rhoads, 2002), their Ca 2ϩ -dependencies for syntaxin-1A binding are very similar. Our current studies also could explain the involvement of CaM in exocytosis (Sakaba and Neher, 2001) and other CaM-dependent interactions (Junge et al, 2004).…”

Section: Cam-dependent Regulation Of Exocytosis Through Ca 2؉ -Dependmentioning

confidence: 52%

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

Watanabe

Nomura

Ohyama

et al. 2005

MBoC

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Myosin-Va is an actin-based processive motor that conveys intracellular cargoes. Synaptic vesicles are one of the most important cargoes for myosin-Va, but the role of mammalian myosin-Va in secretion is less clear than for its yeast homologue, Myo2p. In the current studies, we show that myosin-Va on synaptic vesicles interacts with syntaxin-1A, a t-SNARE involved in exocytosis, at or above 0.3 M Ca 2؉ . Interference with formation of the syntaxin-1A-myosin-Va complex reduces the exocytotic frequency in chromaffin cells. Surprisingly, the syntaxin-1A-binding site was not in the tail of myosin-Va but rather in the neck, a region that contains calmodulin-binding IQ-motifs. Furthermore, we found that syntaxin-1A binding by myosin-Va in the presence of Ca 2؉ depends on the release of calmodulin from the myosin-Va neck, allowing syntaxin-1A to occupy the vacant IQ-motif. Using an anti-myosin-Va neck antibody, which blocks this binding, we demonstrated that the step most important for the antibody's inhibitory activity is the late sustained phase, which is involved in supplying readily releasable vesicles. Our results demonstrate that the interaction between myosin-Va and syntaxin-1A is involved in exocytosis and suggest that the myosin-Va neck contributes not only to the large step size but also to the regulation of exocytosis by Ca 2؉ . INTRODUCTIONMyosin-V, a processive molecular motor, conveys vesicles and other organelles along F-actin (Mercer et al., 1991;Espreafico et al., 1992;Cheney et al., 1993;Reck-Peterson et al., 2000;Vale, 2003). This unconventional myosin is a member of the class-V myosins, which are expressed in all eukaryotic species from yeast to mammals (Reck-Peterson et al., 2000;Matsui, 2003;Vale, 2003). Myosin-V is a dimeric protein (Cheney et al., 1993). Each monomer is composed of a head region, a long neck domain containing six tandem IQ-motifs, and a tail region (Reck-Peterson et al., 2000). The head acts as a plus-end ATPase-dependent molecular motor to move myosin-V along F-actin (Reck-Peterson et al., 2000). The long neck region is thought to act as a lever arm to regulate the motor activity of the head and to maintain the large step size of myosin-V via bound light chains. In higher eukaryotes, the light chains consist mainly of calmodulin (CaM) bound to the IQ-motifs in the neck domain (Cheney et al., 1993;Vale, 2003). In addition, the globular tail of myosin-V interacts with membrane-bound vesicles. In these ways, myosin-V plays a central role in intracellular polarized transport (Reck-Peterson et al., 2000;Matsui, 2003;Vale, 2003).Among the three isoforms of myosin-V in higher vertebrates, myosin-Va is the most abundant, and it is highly enriched in the brain (Espreafico et al., 1992), particularly in the neurons (Tilelli et al., 2003). Several lines of evidence indicate that synaptic vesicles, which undergo the Ca 2ϩ -regulated exocytosis, are one of the most important cargoes for myosin-Va (Prekeris and Terrian, 1997;Bridgman, 1999;Tilelli et al., 2003). In addition, Myo2p, a yeast h...

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Section: Cam-dependent Regulation Of Exocytosis Through Ca 2؉ -Dependmentioning

confidence: 52%

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

Watanabe

Nomura

Ohyama

et al. 2005

MBoC

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“…Calmodulin also mediates rapid recruitment of fast-releasing synaptic vesicles at the calyx of Held 97,98 , further underlining the intimate connection between presynaptic Ca 2+ , release site clearance and endocytosis. other Ca 2+ -binding proteins, such as calcineurin 87,88,99,100 , synaptotagmins, complexins or Munc13 (REFS 12,101) might be additional Ca 2+ effectors facilitating exocytic-endocytic coupling.…”

Section: Calcium Regulationmentioning

confidence: 96%

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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“…The sustained phase of release late during the presynaptic depolarization was presumably attributable to the recruitment of synaptic vesicles. It has been shown that the recruitment of synaptic vesicles has a time constant of 100 -300 ms (Wu and Borst, 1999;Sakaba and Neher, 2001b). When the effect of recruitment was corrected , the slow component saturated earlier during the depolarizing pulse (Fig.…”

Section: Synchronous and Asynchronous Release During A 100 Hz Train Omentioning

confidence: 96%

“…Two sets of readily releasable vesicles (termed fast-releasing and slowly releasing vesicles here) can be distinguished that are distinct with respect to their release probability and speed of recruitment (Wu and Borst, 1999;Sakaba and Neher, 2001b). This study addresses how fast-releasing and slowly releasing vesicles are used during a high-frequency train of AP-like stimuli.…”

Section: Introductionmentioning

confidence: 99%

Roles of the Fast-Releasing and the Slowly Releasing Vesicles in Synaptic Transmission at the Calyx of Held

Sakaba¹

2006

J. Neurosci.

122

150

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In the calyx of Held, fast and slow components of neurotransmitter release can be distinguished during a step depolarization. The two components show different sensitivity to molecular/pharmacological manipulations. Here, their roles during a high-frequency train of action potential (AP)-like stimuli were examined by using both deconvolution of EPSCs and presynaptic capacitance measurements. During a 100 Hz train of AP-like stimuli, synchronous release showed a pronounced depression within the 20 stimuli. Asynchronous release persisted during the train, was variable in its amount, and was more prominent during a 300 Hz train. We have shown previously that slowly releasing vesicles were recruited faster than fast-releasing vesicles after depletion. By further slowing recovery of the fastreleasing vesicles by inhibiting calmodulin-dependent processes (Sakaba and Neher, 2001b), the slowly releasing vesicles were isolated during recovery from vesicle depletion. When a high-frequency train was applied, the isolated slowly releasing vesicles were released predominantly asynchronously. In contrast, synchronous release was mediated mainly by the fast-releasing vesicles. The results suggest that fast-releasing vesicles contribute mainly to synchronous release and that depletion of fast-releasing vesicles shape the synaptic depression of the synchronous phase of EPSCs, whereas slowly releasing vesicles are released mainly asynchronously during highfrequency stimulation. The latter is less subject to depression presumably because of a rapid vesicular recruitment process, which is a characteristic of this component.

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Calmodulin Mediates Rapid Recruitment of Fast-Releasing Synaptic Vesicles at a Calyx-Type Synapse

Cited by 337 publications

References 78 publications

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

Roles of the Fast-Releasing and the Slowly Releasing Vesicles in Synaptic Transmission at the Calyx of Held

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Calmodulin Mediates Rapid Recruitment of Fast-Releasing Synaptic Vesicles at a Calyx-Type Synapse

Cited by 337 publications

References 78 publications

Myosin-Va Regulates Exocytosis through the Submicromolar Ca2+-dependent Binding of Syntaxin-1A

Myosin-Va Regulates Exocytosis through the Submicromolar Ca2+-dependent Binding of Syntaxin-1A

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

Roles of the Fast-Releasing and the Slowly Releasing Vesicles in Synaptic Transmission at the Calyx of Held

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Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A