Nanoscale Structural Plasticity of the Active Zone Matrix Modulates Presynaptic Function

Oleg O Glebov,Rachel E Jackson,Christian M Winterflood,Dylan M Owen,Ellen A Barker,Patrick Doherty,Helge Ewers,Juan Burrone

doi:10.1016/j.celrep.2017.02.064

Oleg O Glebov, Rachel E Jackson + Show 6 more

Open Access

https://doi.org/10.1016/j.celrep.2017.02.064

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Abstract

SummaryThe active zone (AZ) matrix of presynaptic terminals coordinates the recruitment of voltage-gated calcium channels (VGCCs) and synaptic vesicles to orchestrate neurotransmitter release. However, the spatial organization of the AZ and how it controls vesicle fusion remain poorly understood. Here, we employ super-resolution microscopy and ratiometric imaging to visualize the AZ structure on the nanoscale, revealing segregation between the AZ matrix, VGCCs, and putative release sites. Long-term blockade of neuronal activity leads to reversible AZ matrix unclustering and presynaptic actin depolymerization, allowing for enrichment of AZ machinery. Conversely, patterned optogenetic stimulation of postsynaptic neurons retrogradely enhanced AZ clustering. In individual synapses, AZ clustering was inversely correlated with local VGCC recruitment and vesicle cycling. Acute actin depolymerization led to rapid (5 min) nanoscale AZ matrix unclustering. We propose a model whereby neuronal activity modulates presynaptic function in a homeostatic manner by altering the clustering state of the AZ matrix.

Highlights

Synaptic transmission begins with the entry of calcium into the presynaptic terminal through voltage-gated calcium channels (VGCCs), followed by the fusion of neurotransmitter-filled synaptic vesicles (SV) with the presynaptic membrane
Our results show that the active zone (AZ) architecture features largely non-overlapping domains of Bsn-enriched matrix and either VGCCs or Rab3-interacting molecule (RIM)-enriched areas located in close proximity to each other
Nanoscale Imaging of the AZ Structure Confocal microscopy imaging of Bsn and the canonical P/Qtype VGCC pore-forming subunit Cav2.1 shows clear colocalization in punctate structures (Figure 1A), indicating that they both localize to the AZ; this level of resolution is, insufficient to visualize their detailed distribution within the AZ

Summary

Introduction

Synaptic transmission begins with the entry of calcium into the presynaptic terminal through voltage-gated calcium channels (VGCCs), followed by the fusion of neurotransmitter-filled synaptic vesicles (SV) with the presynaptic membrane Both of these events occur at the active zone (AZ), a specialized site in presynaptic boutons that brings together VGCCs and synaptic vesicles within close proximity of each other and of release sites (Su€dhof, 2012). Blockade of postsynaptic activity results in structural changes in hippocampal boutons (Murthy et al, 2001) as well as numerous changes in the levels of AZ proteins in cortical synapses (Lazarevic et al, 2011), lending further support to the idea that the AZ structure is dynamic and controls presynaptic function. The connection between neuronal activity and the precise structure of the AZ has not been formally investigated

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Discussion

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