scholarly journals Munc13-1 MUN domain and Munc18-1 cooperatively chaperone SNARE assembly through a tetrameric complex

2019 ◽  
Vol 117 (2) ◽  
pp. 1036-1041 ◽  
Author(s):  
Tong Shu ◽  
Huaizhou Jin ◽  
James E. Rothman ◽  
Yongli Zhang
Keyword(s):  
Synaptic Vesicle ◽  
Molecular Mechanism ◽  
Single Molecule ◽  
Neurotransmitter Release ◽  
Vesicle Fusion ◽  
Snare Proteins ◽  
Single Molecule Force Spectroscopy ◽  
Multifunctional Protein ◽  
Synaptic Vesicle Fusion ◽  
Template Complex

Munc13-1 is a large multifunctional protein essential for synaptic vesicle fusion and neurotransmitter release. Its dysfunction has been linked to many neurological disorders. Evidence suggests that the MUN domain of Munc13-1 collaborates with Munc18-1 to initiate SNARE assembly, thereby priming vesicles for fast calcium-triggered vesicle fusion. The underlying molecular mechanism, however, is poorly understood. Recently, it was found that Munc18-1 catalyzes neuronal SNARE assembly through an obligate template complex intermediate containing Munc18-1 and 2 SNARE proteins—syntaxin 1 and VAMP2. Here, using single-molecule force spectroscopy, we discovered that the MUN domain of Munc13-1 stabilizes the template complex by ∼2.1 kBT. The MUN-bound template complex enhances SNAP-25 binding to the templated SNAREs and subsequent full SNARE assembly. Mutational studies suggest that the MUN-bound template complex is functionally important for SNARE assembly and neurotransmitter release. Taken together, our observations provide a potential molecular mechanism by which Munc13-1 and Munc18-1 cooperatively chaperone SNARE folding and assembly, thereby regulating synaptic vesicle fusion.

scholarly journals Synaptotagmin 1 clamps synaptic vesicle fusion in mammalian neurons independent of complexin

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Nicholas A. Courtney ◽  
Huan Bao ◽  
Joseph S. Briguglio ◽  
Edwin R. Chapman
Keyword(s):  
Synaptic Vesicle ◽  
Vesicle Fusion ◽  
Snare Proteins ◽  
Major Focus ◽  
C2 Domains ◽  
Releasable Pool ◽  
Readily Releasable Pool ◽  
Synaptotagmin 1 ◽  
Synaptic Vesicle Fusion ◽  
C2a Domain

Abstract Synaptic vesicle (SV) exocytosis is mediated by SNARE proteins. Reconstituted SNAREs are constitutively active, so a major focus has been to identify fusion clamps that regulate their activity in synapses: the primary candidates are synaptotagmin (syt) 1 and complexin I/II. Syt1 is a Ca2+ sensor for SV release that binds Ca2+ via tandem C2-domains, C2A and C2B. Here, we first determined whether these C2-domains execute distinct functions. Remarkably, the C2B domain profoundly clamped all forms of SV fusion, despite synchronizing residual evoked release and rescuing the readily-releasable pool. Release was strongly enhanced by an adjacent C2A domain, and by the concurrent binding of complexin to trans-SNARE complexes. Knockdown of complexin had no impact on C2B-mediated clamping of fusion. We postulate that the C2B domain of syt1, independent of complexin, is the molecular clamp that arrests SVs prior to Ca2+-triggered fusion.

scholarly journals Molecular Mechanisms of Fast Neurotransmitter Release

2018 ◽  
Vol 47 (1) ◽  
pp. 469-497 ◽  
Author(s):  
Axel T. Brunger ◽  
Ucheor B. Choi ◽  
Ying Lai ◽  
Jeremy Leitz ◽  
Qiangjun Zhou
Keyword(s):  
Synaptic Vesicle ◽  
Neurotransmitter Release ◽  
High Speed ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Vesicle Fusion ◽  
Synaptic Proteins ◽  
Functional Studies ◽  
Protein Receptors ◽  
Synaptic Vesicle Fusion

This review summarizes current knowledge of synaptic proteins that are central to synaptic vesicle fusion in presynaptic active zones, including SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors), synaptotagmin, complexin, Munc18 (mammalian uncoordinated-18), and Munc13 (mammalian uncoordinated-13), and highlights recent insights in the cooperation of these proteins for neurotransmitter release. Structural and functional studies of the synaptic fusion machinery suggest new molecular models of synaptic vesicle priming and Ca2+-triggered fusion. These studies will be a stepping-stone toward answering the question of how the synaptic vesicle fusion machinery achieves such high speed and sensitivity.

scholarly journals Munc13 binds and recruits SNAP25 to chaperone SNARE complex assembly

2020 ◽  
Author(s):  
R Venkat Kalyana Sundaram ◽  
Huaizhou Jin ◽  
Feng Li ◽  
Tong Shu ◽  
Jeff Coleman ◽  
...  
Keyword(s):  
Single Molecule ◽  
Optical Tweezer ◽  
Snare Complex ◽  
Snare Proteins ◽  
Synaptic Membrane ◽  
Complex Assembly ◽  
Chaperone Function ◽  
Direct Binding ◽  
Synaptic Vesicle Fusion ◽  
Template Complex

ABSTRACTSynaptic vesicle fusion is mediated by membrane-bridging complexes formed by SNARE proteins - VAMP2 on the vesicle and Syntaxin-1/SNAP25 on the pre-synaptic membrane. Accumulating evidence suggest that chaperones Munc18-1 and Munc13-1 co-operatively catalyze SNARE assembly via an intermediate ‘template’ complex containing Syntaxin-1 and VAMP2. How SNAP25 is chaperoned into this nascent complex remains a mystery. Here we report that Munc13-1 recruits SNAP25 to initiate the ternary SNARE complex assembly by direct binding, as judged by bulk FRET spectroscopy and single-molecule optical tweezer studies. Detailed structure-function analyses show that the binding is mediated by the Munc13-1 MUN domain and is specific for the SNAP25 ‘linker’ region that connects the two SNARE motifs. Consequently, freely diffusing SNAP25 molecules on phospholipid bilayers are concentrated and presumably bound in ~1:1 stoichiometry by the self-assembled Munc13-1 nanoclusters. Our data suggests that Munc13-1’s capacity to bind all three synaptic SNARE proteins likely underlie its chaperone function.

scholarly journals Complexin-1 regulated transition in the assembly of single neuronal SNARE complex

2021 ◽  
Author(s):  
Hao Tongrui ◽  
Feng Nan ◽  
Gong Fan ◽  
Liu Jiaquan ◽  
Lu Ma ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Molecular Mechanism ◽  
Optical Tweezers ◽  
Neurotransmitter Release ◽  
Snare Complex ◽  
Snare Proteins ◽  
Synaptic Vesicle Exocytosis ◽  
Sensitive Factor ◽  
Vesicle Exocytosis ◽  
Vesicle Pool

Neurotransmitter release is mediated by the synaptic vesicle exocytosis. Important proteins in this process have been identified including the molecular machine Synaptic-soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, and other regulators. Complexin (Cpx) is one of the vital regulators in this process. The functions of Cpx are proposed to maintain a proper primed vesicle pool by preventing its premature depletion, which facilitates the vesicle fusion in the presence of Ca2+. However, the molecular mechanism remains unclear. Using dual-trap optical tweezers, we detected the interaction of complexin-1 (CpxI) with SNARE. We found that the CpxI stabilizes partially folded SNARE complexes by competing with C-terminal of Vamp protein and interacting with the C-terminal of t-SNARE complex.

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