Distinct nanoscale calcium channel and synaptic vesicle topographies contribute to the diversity of synaptic function

Published: 4 August 2019| Version 3 | DOI: 10.17632/fjmp63fgnw.3
Contributors:
Nelson Rebola,
Maria Reva,
Tekla Kirizs,
Andrea Lorincz,
Miklos Szoboszlay,
Gael Moneron,
Zoltán Nusser ,
David DiGregorio

Description

The nanoscale topographical arrangement of voltage-gated calcium channels (VGCC) and synaptic vesicles (SVs) determines synaptic strength and plasticity, but whether distinct spatial distributions underpin diversity of synaptic function is unknown. We performed single bouton Ca2+ imaging, Ca2+ chelator competition, immunogold electron microscopic (EM) localization of VGCCs and the active zone (AZ) protein Munc13-1, at two cerebellar synapses. Unexpectedly, we found that weak synapses exhibited 3-fold more VGCCs than strong synapses, while the coupling distance was 5-fold longer. Reaction-diffusion modelling could explain both functional and structural data with two strikingly different nanotopographical motifs: strong synapses are composed of SVs that are tightly coupled (~10 nm) to VGCC clusters, whereas at weak synapses VGCCs were excluded from the vicinity (~50 nm) of docked vesicles. The distinct VGCC-SV topographical motifs also confer differential sensitivity to neuromodulation. Thus VGCC-SV arrangements are not canonical and their diversity could underlie functional heterogeneity across CNS synapses.

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