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Article Dans Une Revue FEBS Letters Année : 2021

Munc13 binds and recruits SNAP25 to chaperone SNARE complex assembly

Ramalingam Venkat Kalyana Sundaram
Huaizhou Jin
  • Fonction : Auteur
Feng Li
Tong Shu
  • Fonction : Auteur
Jeff Coleman
  • Fonction : Auteur
Jie Yang
Frederic Pincet
Yongli Zhang
James E Rothman
  • Fonction : Auteur
  • PersonId : 1040472
Shyam S Krishnakumar
  • Fonction : Auteur
  • PersonId : 1138410

Résumé

Synaptic vesicle fusion is mediated by SNARE proteins-VAMP2 on the vesicle and Syntaxin-1/ SNAP25 on the pre-synaptic membrane. Chaperones Munc18-1 and Munc13-1 cooperatively catalyze SNARE assembly via an intermediate 'template' complex containing Syntaxin-1 and VAMP2. How SNAP25 enters this reaction 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 bound in ~1:1 stoichiometry by the self-assembled Munc13-1 nano-clusters. Neuronal communication involves the controlled release of neurotransmitters stored in synaptic vesicles (SV) into the neuronal synapse [1-4]. This process is tightly regulated to ensure that the message is timely and precise [3, 4]. SV fusion is catalyzed by the synaptic SNARE (soluble N-ethyl maleimide sensitive factor attachment protein) proteins-VAMP2 on the vesicle membrane (v-SNARE) and Syntaxin-1 and SNAP25 on the plasma membrane (t-SNAREs) [5, 6]. When the vesicle approaches the plasma membrane (PM), the helical SNARE motifs of the cognate v-and t-SNAREs constitutively assemble into a ternary complex that initially bridges and ultimately fuses the two membranes [5-7]. The SNARE complex nucleates into a four-helix bundle at its membrane distal end and progressively assembles ("zippers") towards the membranes, exerting a potent force that ultimately drives the membranes together to fuse into one [6, 8, 9]. Though efficient, under in vitro conditions, the fusion process is artificially slow with its rate being limited by the intrinsic rate of nucleation of SNARE complex [10-12]. In vivo, nucleation is greatly accelerated by two cooperating , specialized molecular chaperones, Munc13 and Munc18 [3, 4, 13, 14].
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Dates et versions

hal-03405619 , version 1 (27-10-2021)

Identifiants

Citer

Ramalingam Venkat Kalyana Sundaram, Huaizhou Jin, Feng Li, Tong Shu, Jeff Coleman, et al.. Munc13 binds and recruits SNAP25 to chaperone SNARE complex assembly. FEBS Letters, 2021, 595, pp.297 - 309. ⟨10.1002/1873-3468.14006⟩. ⟨hal-03405619⟩
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