%0 Journal Article
%T Tomosyns attenuate SNARE assembly and synaptic depression by binding to VAMP2-containing template complexes.
%A Meijer M
%A Öttl M
%A Yang J
%A Subkhangulova A
%A Kumar A
%A Feng Z
%A van Voorst TW
%A Groffen AJ
%A van Weering JRT
%A Zhang Y
%A Verhage M
%J Nat Commun
%V 15
%N 1
%D 2024 Mar 26
%M 38531902
%F 17.694
%R 10.1038/s41467-024-46828-1
%X Tomosyns are widely thought to attenuate membrane fusion by competing with synaptobrevin-2/VAMP2 for SNARE-complex assembly. Here, we present evidence against this scenario. In a novel mouse model, tomosyn-1/2 deficiency lowered the fusion barrier and enhanced the probability that synaptic vesicles fuse, resulting in stronger synapses with faster depression and slower recovery. While wild-type tomosyn-1m rescued these phenotypes, substitution of its SNARE motif with that of synaptobrevin-2/VAMP2 did not. Single-molecule force measurements indeed revealed that tomosyn's SNARE motif cannot substitute synaptobrevin-2/VAMP2 to form template complexes with Munc18-1 and syntaxin-1, an essential intermediate for SNARE assembly. Instead, tomosyns extensively bind synaptobrevin-2/VAMP2-containing template complexes and prevent SNAP-25 association. Structure-function analyses indicate that the C-terminal polybasic region contributes to tomosyn's inhibitory function. These results reveal that tomosyns regulate synaptic transmission by cooperating with synaptobrevin-2/VAMP2 to prevent SNAP-25 binding during SNARE assembly, thereby limiting initial synaptic strength and equalizing it during repetitive stimulation.