Accessory Proteins Stabilize the Acceptor Complex for Synaptobrevin, the 1:1 Syntaxin/SNAP-25 Complex

Weninger, Keith; Bowen, Mark E.; Choi, Ucheor B.; Chu, Steven; Brunger, Axel T.

doi:10.1016/j.str.2007.12.010

Cited by 161 publications

(204 citation statements)

References 70 publications

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“…This model suggests that there may be a direct interaction between CplxI and the 1:1 Syntaxin/ SNAP-25 binary complex. Indeed, this interaction was observed recently (28,29). However, this interaction also stabilizes the 1:1 Syntaxin/SNAP-25 binary complex to promote the formation of SNARE complex, consistent with the facilitating function of CplxI (29).…”

Section: Discussionsupporting

confidence: 68%

“…Indeed, this interaction was observed recently (28,29). However, this interaction also stabilizes the 1:1 Syntaxin/SNAP-25 binary complex to promote the formation of SNARE complex, consistent with the facilitating function of CplxI (29). It is possible that the inhibitory function of the accessory ␣-helix is more pronounced in dmCplx, thus causing a clamp-like effect.…”

Section: Discussionsupporting

confidence: 58%

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Complexins facilitate neurotransmitter release at excitatory and inhibitory synapses in mammalian central nervous system

Xue

Stradomska

Chen

et al. 2008

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

125

149

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Complexins (Cplxs) are key regulators of synaptic exocytosis, but whether they act as facilitators or inhibitors is currently being disputed controversially. We show that genetic deletion of all Cplxs expressed in the mouse brain causes a reduction in Ca 2؉ -triggered and spontaneous neurotransmitter release at both excitatory and inhibitory synapses. Our results demonstrate that at mammalian central nervous system synapses, Cplxs facilitate neurotransmitter release and do not simply act as inhibitory clamps of the synaptic vesicle fusion machinery.Ca 2ϩ trigger ͉ exocytosis ͉ SNARE

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Section: Discussionsupporting

confidence: 68%

Section: Discussionsupporting

confidence: 58%

Complexins facilitate neurotransmitter release at excitatory and inhibitory synapses in mammalian central nervous system

Xue

Stradomska

Chen

et al. 2008

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

125

149

View full text Add to dashboard Cite

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“…complex binding remains uncertain [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].…”

mentioning

confidence: 99%

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

Maximov

Tang

Yang

et al. 2009

Science

315

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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“…SM proteins have also been shown to interact with SNARE binary and SNARE ternary complexes (9)(10)(11), and these interactions require an open Sx binding mode as well as the presence of an N-peptide, the 10-30 residues at the very N terminus of Sx (11)(12)(13)(14). The two binding modes (closed and N-peptide) are thought to be associated with different aspects of SM protein function.…”

mentioning

confidence: 99%

Low-resolution solution structures of Munc18:Syntaxin protein complexes indicate an open binding mode driven by the Syntaxin N-peptide

Christie¹,

Whitten²,

King³

et al. 2012

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

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When nerve cells communicate, vesicles from one neuron fuse with the presynaptic membrane releasing chemicals that signal to the next. Similarly, when insulin binds its receptor on adipocytes or muscle, glucose transporter-4 vesicles fuse with the cell membrane, allowing glucose to be imported. These essential processes require the interaction of SNARE proteins on vesicle and cell membranes, as well as the enigmatic protein Munc18 that binds the SNARE protein Syntaxin. Here, we show that in solution the neuronal protein Syntaxin1a interacts with Munc18-1 whether or not the Syntaxin1a N-peptide is present. Conversely, the adipocyte protein Syntaxin4 does not bind its partner Munc18c unless the N-peptide is present. Solution-scattering data for the Munc18-1:Syntaxin1a complex in the absence of the N-peptide indicates that this complex adopts the inhibitory closed binding mode, exemplified by a crystal structure of the complex. However, when the N-peptide is present, the solution-scattering data indicate both Syntaxin1a and Syntaxin4 adopt extended conformations in complexes with their respective Munc18 partners. The low-resolution solution structure of the open Munc18:Syntaxin binding mode was modeled using data from cross-linking/mass spectrometry, small-angle X-ray scattering, and small-angle neutron scattering with contrast variation, indicating significant differences in Munc18:Syntaxin interactions compared with the closed binding mode. Overall, our results indicate that the neuronal Munc18-1:Syntaxin1a proteins can adopt two alternate and functionally distinct binding modes, closed and open, depending on the presence of the N-peptide, whereas Munc18c:Syntaxin4 adopts only the open binding mode. membrane fusion | protein interactions | small-angle neutron scattering | small-angle X-ray scattering M embrane trafficking is an essential and highly regulated process whereby cargo-carrying vesicles are directed to dock and fuse with specific cell membranes. The process requires soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins on vesicle and target membranes. These interact to form high-affinity SNARE complexes required for docking and membrane fusion (1, 2). Structurally, the SNARE complex is a parallel four-helix bundle comprising helices contributed from several partner SNAREs (3). This helical bundle promotes vesicle fusion by bringing the vesicle and plasma membranes into close proximity and by providing the energy required for membrane fusion (4, 5).In the neuronal synapse, neurotransmitters are released from nerve cells by SNARE-mediated fusion of vesicles with the plasma membrane in response to action potentials. In this process, one of four SNARE helices is contributed by Syntaxin (Sx) 1a, a protein localized at the plasma membrane by a transmembrane helix. In addition to its membrane-anchored SNARE helix (H3), Sx1a has an Habc domain that can bind to the H3 helix (6) forming a closed Sx1a conformation (Fig. 1A). This closed conformation inactivates Sx1a by preventing H3 inter...

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Accessory Proteins Stabilize the Acceptor Complex for Synaptobrevin, the 1:1 Syntaxin/SNAP-25 Complex

Cited by 161 publications

References 70 publications

Complexins facilitate neurotransmitter release at excitatory and inhibitory synapses in mammalian central nervous system

Complexins facilitate neurotransmitter release at excitatory and inhibitory synapses in mammalian central nervous system

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

Low-resolution solution structures of Munc18:Syntaxin protein complexes indicate an open binding mode driven by the Syntaxin N-peptide

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