Dual inhibition of SNARE complex formation by tomosyn ensures controlled neurotransmitter release

Abstract

Neurotransmitter release from presynaptic nerve terminals is regulated by soluble NSF attachment protein receptor (SNARE) complex–mediated synaptic vesicle fusion. Tomosyn inhibits SNARE complex formation and neurotransmitter release by sequestering syntaxin-1 through its C-terminal vesicle-associated membrane protein (VAMP)–like domain (VLD). However, in tomosyn-deficient mice, the SNARE complex formation is unexpectedly decreased. In this study, we demonstrate that the N-terminal WD-40 repeat domain of tomosyn catalyzes the oligomerization of the SNARE complex. Microinjection of the tomosyn N-terminal WD-40 repeat domain into neurons prevented stimulated acetylcholine release. Thus, tomosyn inhibits neurotransmitter release by catalyzing oligomerization of the SNARE complex through the N-terminal WD-40 repeat domain in addition to the inhibitory activity of the C-terminal VLD.

Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn‐1 gene

“…Another potential reason for the difference in mortality between the VAMP2 and STXBP5/tomosyn‐1 animals may relate to background, since the VAMP‐2 mice were on a pure C57B/6 genetic background. As in the previous studies by Sakisaka et al., 2008, we used null animals and littermate controls on a hybrid genetic background of C57B/6 and BDF1.…”

“…The STXBP5/Tom −/− mice on a 50% 129Sv, 25% C57BL/6, and 25% DBA/2 background were generated as described previously (Sakisaka et al., 2008) and kindly provided by Dr. Yoshimi Takai (Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan). All work with animals was done with approval from the University of Kentucky IACUC.…”

“…All work with animals was done with approval from the University of Kentucky IACUC. Genotyping was performed by PCR using DNA prepared from tail biopsies (Sakisaka et al., 2008); wild‐type littermates were used as controls. These STXBP5/Tom −/− mice were shown to be lacking tomosyn‐1, but none of the other elements of the secretory machinery by quantitative western blotting of different tissues (Sakisaka et al., 2008; Ye et al., 2014).…”

“…These proteins include those that affect the dynamics of the “readily releasable pool” of NT‐containing vesicles, for example, Munc13s, Complexins, SV2s, and STXBP5/tomosyn‐1, as well as those that recycle SNARE complexes, for example, NSF and α‐SNAP (Ashery et al., 2000; Custer, Austin, Sullivan, & Bajjalieh, 2006; Hu et al., 2002; Whiteheart, Schraw, & Matveeva, 2001). STXBP5/tomosyn‐1 is thought to function as a negative regulator of SNARE‐mediated membrane fusion, primarily by sequestering the syntaxin‐1a and SNAP‐25 heterodimer and inhibiting 7SC formation (Ashery, Bielopolski, Barak, & Yizhar, 2009; Sakisaka et al., 2008; Willams et al., 2011). STXBP5/tomosyn‐1's C‐terminal VAMP‐like domain binds the t‐SNARE heterodimer and regulates access to v‐SNAREs.…”

Differential Interaction of Tomosyn with Syntaxin and SNAP25 Depends on Domains in the WD40 β-Propeller Core and Determines Its Inhibitory Activity

“…Tomosyn contains a synaptobrevin-like SNARE motif but lacks a transmembrane anchor, which might preclude the SNARE molecules from forming fusogenic SNARE complexes, thereby inhibiting priming and fusion. It was also claimed that the N-terminal WD40 repeat domain of tomosyn catalyzes oligomerization of the SNARE complex, leading to inhibition of neurotransmitter release (7). Furthermore, it was shown that tomosyn can inhibit exocytosis independently of its SNARE interaction with syntaxin and that the integrity of the WD40 domain is crucial for tomosyn's inhibitory function (8).…”