Distinct Nanoscale Calcium Channel and Synaptic Vesicle Topographies Contribute to the Diversity of Synaptic Function

Rebola, Nelson and Reva, Maria and Kirizs, Tekla and Szoboszlay, Miklós and Lőrincz, Andrea and Moneron, Gael and Nusser, Zoltán and DiGregorio, David A. (2019) Distinct Nanoscale Calcium Channel and Synaptic Vesicle Topographies Contribute to the Diversity of Synaptic Function. NEURON, 104 (4). pp. 693-710. ISSN 0896-6273 (print); 1097-4199 (online)

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Abstract

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 modeling could explain both functional and structural data with two strikingly different nanotopographical motifs: strong synapses are composed of SVs that are tightly coupled (similar to 10 nm) to VGCC clusters, whereas at weak synapses VGCCs were excluded from the vicinity (similar to 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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