The Number and Distinct Clustering Patterns of Voltage-Gated Calcium Channels in Nerve Terminals.

Kohgaku Eguchi,Ryuichi Shigemoto,Jacqueline Montanaro,Elodie Le Monnier

doi:10.3389/fnana.2022.846615

Kohgaku Eguchi, Ryuichi Shigemoto + Show 2 more

Open Access

https://doi.org/10.3389/fnana.2022.846615

Copy DOI

Abstract

Upon the arrival of action potentials at nerve terminals, neurotransmitters are released from synaptic vesicles (SVs) by exocytosis. CaV2.1, 2.2, and 2.3 are the major subunits of the voltage-gated calcium channel (VGCC) responsible for increasing intraterminal calcium levels and triggering SV exocytosis in the central nervous system (CNS) synapses. The two-dimensional analysis of CaV2 distributions using sodium dodecyl sulfate (SDS)-digested freeze-fracture replica labeling (SDS-FRL) has revealed their numbers, densities, and nanoscale clustering patterns in individual presynaptic active zones. The variation in these properties affects the coupling of VGCCs with calcium sensors on SVs, synaptic efficacy, and temporal precision of transmission. In this study, we summarize how the morphological parameters of CaV2 distribution obtained using SDS-FRL differ depending on the different types of synapses and could correspond to functional properties in synaptic transmission.

Highlights

At a chemical synapse, the arrival of an action potential (AP) at the nerve terminal activates voltagegated calcium channels (VGCCs), thereby inducing Ca2+ influx into the terminal
Previous studies using squid giant synapses and chick ciliary ganglion calyx synapses have proposed that Ca2+ influx through a single VGCC can generate the fusion of an synaptic vesicles (SVs) if the Ca2+ sensor is sufficiently close to the channel (Stanley, 2016)
Sodium dodecyl sulfate-digested FRL studies demonstrate the nanoscale distribution of CaV 2 channels at active zone (AZ) of presynaptic terminals

Summary

INTRODUCTION

The arrival of an action potential (AP) at the nerve terminal activates voltagegated calcium channels (VGCCs), thereby inducing Ca2+ influx into the terminal. Previous studies have demonstrated the number/density of CaV 2.1 channels in the AZs and their clustering (Indriati et al, 2013; Nakamura et al, 2015; Miki et al, 2017; Rebola et al, 2019; Kleindienst et al, 2020), indicating the massive influx of Ca2+ through the clustered channels to effectively increase the Ca2+ level at the nano-spots in the AZs. To estimate clustering patterns accurately, a high labeling efficiency as described earlier is desirable. The 5 nm gold particles conjugated with antiguinea pig IgG (the same one as we verified earlier) were sparsely distributed without clustering, indicating no multiple binding of the secondary antibody to a single primary antibody (Figure 2D).

CONCLUSION

Findings

DATA AVAILABILITY STATEMENT