Allosteric modulation of the presynaptic Ca2+ sensor for vesicle fusion

Lou, Xuelin; Scheuss, Volker; Schneggenburger, Ralf

doi:10.1038/nature03568

Cited by 280 publications

(447 citation statements)

References 29 publications

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“…Such dependence indicates that Ca 2+ -dependent mechanisms may facilitate the recovery of τ fast . Thus, we tested the possibility that acceleration of τ fast recovery is mediated by Ca 2+ -induced activation of phospholipase C (PLC), which activates Munc13s, which are essential mediators of molecular priming (10,12,17). Inclusion of U73122 (10 μM), a PLC inhibitor, in the presynaptic pipette had no effect on the recovery of FRP size after preDP3 (P = 0.48) and preDP10 (P = 0.27; n = 12; Table S1), and partially suppressed it after a preDP30 (42.1 ± 1.9%; n = 12; P < 0.01; Fig.…”

Section: Resultsmentioning

confidence: 99%

“…We show that the mechanism regulating recovery of Ca 2+ sensitivity is distinct from that regulating recovery of the FRP size, in that the former and the latter require activation of Munc13s and the integrity of the cytoskeleton, respectively. The Ca 2+ sensitivity is known to be profoundly affected by phorbol esters, which lower the energy barrier for vesicle fusion (9,10). Munc13 has been identified as a presynaptic receptor of phorbol esters together with PKC (11)(12)(13).…”

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confidence: 99%

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Superpriming of synaptic vesicles after their recruitment to the readily releasable pool

Lee

Neher

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

103

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Recruitment of release-competent vesicles during sustained synaptic activity is one of the major factors governing short-term plasticity. During bursts of synaptic activity, vesicles are recruited to a fast-releasing pool from a reluctant vesicle pool through an actin-dependent mechanism. We now show that newly recruited vesicles in the fast-releasing pool do not respond at full speed to a strong Ca 2+ stimulus, but require approximately 4 s to mature to a "superprimed" state. Superpriming was found to be altered by agents that modulate the function of unc13 homolog proteins (Munc13s), but not by calmodulin inhibitors or actin-disrupting agents. These findings indicate that recruitment and superpriming of vesicles are regulated by separate mechanisms, which require integrity of the cytoskeleton and activation of Munc13s, respectively. We propose that refilling of the fast-releasing vesicle pool proceeds in two steps, rapid actin-dependent "positional priming," which brings vesicles closer to Ca 2+ sources, followed by slower superpriming, which enhances the Ca 2+ sensitivity of primed vesicles.T he release rate of a synaptic vesicle (SV) is governed by two factors, the intrinsic Ca 2+ sensitivity of the vesicle fusion machinery and the distance of the SV to Ca 2+ channels. As Munc13s and Munc18s confer fusion competence on a docked SV, the regulation of release rate by Munc13s and Munc18s is called "molecular priming" (1). It is distinguished from "positional priming," a process that is thought to regulate the proximity of an SV to the calcium source (2, 3). However, it is not known how these two priming mechanisms are manifested in the kinetics of quantal release. Deconvolution analyses of excitatory postsynaptic currents (EPSCs) evoked by long presynaptic depolarizations at the calyx of Held (a giant nerve terminal in the auditory pathway) showed that releasable SVs can be separated into fastreleasing pools (FRPs) and slowly releasing pools (SRPs) (4). The differences in SV priming that underlie the differences in release kinetics between SVs in the FRP and the SRP are currently unclear (3, 5). Wadel et al. (3) found that SVs in the SRP can be released by homogenous Ca 2+ elevation only 1.5 to 2 times slower than SVs in the FRP, even though they are released 10 times slower by depolarization-induced Ca 2+ influx. This was interpreted as evidence that the differences in their release kinetics arise from differences primarily in positional priming. In contrast, Wölfel et al. (5) showed that release with two kinetic components is even observed if the intracellular Ca 2+ concentration is homogenously elevated throughout the calyx terminal, indicating that SVs in the FRP and the SRP differ with regard to their molecular priming.We found recently that SVs in the SRP rapidly convert into the FRP after specific FRP depletion by a short depolarizing pulse (6). Such rapid refilling of the FRP with SRP vesicles, which is referred to as SRP-dependent recovery (SDR), was suppressed by actin depolymerization or inhibition ...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Superpriming of synaptic vesicles after their recruitment to the readily releasable pool

Lee

Neher

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

103

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“…[Ca 2+ ] i was measured by fura-2 ratiometric fluorescence imaging as described previously (39,95). NADPH fluorescence imaging was carried out with the same system as the Ca 2+ imaging (see the Supplemental Methods for details).…”

Section: Discussionmentioning

confidence: 99%

Dynamin 2 regulates biphasic insulin secretion and plasma glucose homeostasis

Fan¹,

Chen²,

Wu³

et al. 2015

Journal of Clinical Investigation

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“…S1). Phorbol esters (synthetic DAG analogs) are widely used to activate the DAG/PKC pathway (3)(4)(5), and require the activation of PKC to potentiate vesicle release in hippocampal neurons (8). We therefore measured the effect of phorbol 12-myristate 13-acetate (PMA) in Syt WT or Syt T112A expressing neurons on spontaneous and AP-evoked release.…”

Section: Phosphorylation Of T112 Is Essential For Phorbol Ester-inducedmentioning

confidence: 99%

“…The diacylglycerol (DAG)/protein kinase C (PKC) cascade is one of the most potent pathways at the presynaptic terminal. Its activation leads to 50-100% potentiation of spontaneous and action potential (AP)-evoked release (3)(4)(5), and is critical for multiple forms of presynaptic plasticity (6)(7)(8). DAG directly activates the vesicle priming factor Munc13-1 (9, 10) and indirectly activates downstream effectors via PKC.…”

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confidence: 99%

Phosphorylation of synaptotagmin-1 controls a post-priming step in PKC-dependent presynaptic plasticity

Jong

Meijer

Saarloos

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Presynaptic activation of the diacylglycerol (DAG)/protein kinase C (PKC) pathway is a central event in short-term synaptic plasticity. Two substrates, Munc13-1 and Munc18-1, are essential for DAGinduced potentiation of vesicle priming, but the role of most presynaptic PKC substrates is not understood. Here, we show that a mutation in synaptotagmin-1 (Syt1 T112A ), which prevents its PKCdependent phosphorylation, abolishes DAG-induced potentiation of synaptic transmission in hippocampal neurons. This mutant also reduces potentiation of spontaneous release, but only if alternative Ca 2+ sensors, Doc2A/B proteins, are absent. However, unlike mutations in Munc13-1 or Munc18-1 that prevent DAG-induced potentiation, the synaptotagmin-1 mutation does not affect pairedpulse facilitation. Furthermore, experiments to probe vesicle priming (recovery after train stimulation and dual application of hypertonic solutions) also reveal no abnormalities. Expression of synaptotagmin-2, which lacks a seven amino acid sequence that contains the phosphorylation site in synaptotagmin-1, or a synaptotagmin-1 variant with these seven residues removed (Syt1 Δ109-116 ), supports normal DAG-induced potentiation. These data suggest that this seven residue sequence in synaptotagmin-1 situated in the linker between the transmembrane and C2A domains is inhibitory in the unphosphorylated state and becomes permissive of potentiation upon phosphorylation. We conclude that synaptotagmin-1 phosphorylation is an essential step in PKC-dependent potentiation of synaptic transmission, acting downstream of the two other essential DAG/PKC substrates, Munc13-1 and Munc18-1.P resynaptic strength changes rapidly during repetitive stimulation [short-term plasticity (STP)] and activation of intracellular signal transduction pathways (1, 2). The diacylglycerol (DAG)/protein kinase C (PKC) cascade is one of the most potent pathways at the presynaptic terminal. Its activation leads to 50-100% potentiation of spontaneous and action potential (AP)-evoked release (3-5), and is critical for multiple forms of presynaptic plasticity (6-8). DAG directly activates the vesicle priming factor Munc13-1 (9, 10) and indirectly activates downstream effectors via PKC. Activation of both Munc13-1 and PKC is essential for this pathway to operate (Fig. 1A) (8, 11). We previously identified Munc18-1 as an essential PKC substrate, because a nonphosphorylatable Munc18-1 mutant completely inhibits PKC-dependent STP (8, 12). Importantly, a phosphomimetic mutation of Munc18-1 cannot fully bypass the requirement for PKC activation, indicating that other PKC substrates must contribute to this form of plasticity (8). These substrates have not been identified to date.Among other presynaptic PKC substrates is synaptotagmin-1 (Syt1, ref. 13). Syt1 is the vesicular Ca 2+ sensor that mediates fast AP-evoked release in the hippocampus (14) and drives a large fraction of spontaneous release (15). In the latter case, Syt1 competes with alternative sensors, in particular Doc2s, for SNARE binding ...

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Allosteric modulation of the presynaptic Ca2+ sensor for vesicle fusion

Cited by 280 publications

References 29 publications

Superpriming of synaptic vesicles after their recruitment to the readily releasable pool

Superpriming of synaptic vesicles after their recruitment to the readily releasable pool

Dynamin 2 regulates biphasic insulin secretion and plasma glucose homeostasis

Phosphorylation of synaptotagmin-1 controls a post-priming step in PKC-dependent presynaptic plasticity

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