Accessory and Central α-helices of Complexin Selectively Activate Ca2+ Triggering of Synaptic Exocytosis.

Yi Yu,Su Chen,Xiaoqiang Mo,Jihong Gong,Chenhong Li,Xiaofei Yang

doi:10.3389/fnmol.2018.00061

Abstract

Complexins, binding to assembling soluble NSF-attachment protein receptor (SNARE) complexes, activate Ca2+ triggered exocytosis and clamp spontaneous release in the presynaptic terminal. Functions of complexin are structural dependent and mechanistically distinct. To further understand the functional/structural dependence of complexin, here we show that the accessory and central α-helices of complexin are sufficient in activation of Ca2+ triggered vesicle fusion but not in clamping spontaneous release. Targeting the two α-helices to synaptic vesicle suppresses spontaneous release, thus further emphasizing the importance of curvature membrane localization in clamping function.

Highlights

Neurotransmitter release is mediated by Ca2+ triggered synaptic vesicle fusion
The dissociated cortical neurons were dissected from postnatal day 0 (P0) of WT Kunming mice, dissociated by 0.25% trypsin-EDTA digestion for 12 min at 37◦C, plated at 12 mm diameter circular glass coverslips coated with poly-L-lysine (Sigma), and cultured in MEM (GIBCO) supplemented with 2 v/v% B27 (GIBCO), 0.5 w/v% glucose, 100 mg/l transferrin, 5 v/v% fetal bovine serum (GIBCO) and 2 mM Ara-C (Sigma)
Since all the functions of Cpx were relied on the binding of central α-helix to soluble NSF-attachment protein receptor (SNARE) complex (Maximov et al, 2009), we first examined whether the central α-helix alone could regulate vesicle release

Summary

Introduction

Neurotransmitter release is mediated by Ca2+ triggered synaptic vesicle fusion. Syntaxin-1, SNAP-25 and synaptobrevin/VAMP2 (vesicle-associated membrane protein) form a tight complex that forces membranes into close proximity, and Munc binds to the SNARE complex to catalyze fusion (Südhof and Rothman, 2009). During this process, many other proteins have been involved to promote fusion, including Munc, synaptotagmin and complexin (Cpx; Geppert et al, 1994; McMahon et al, 1995; Wang et al, 2017). Cpx functionally cooperates with synaptotagmin in regulating synaptic exocytosis (McMahon et al, 1995; Reim et al, 2001; Zhou et al, 2017)

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Results

Conclusion