Nanoscale dynamics of synaptic vesicle trafficking and fusion at the presynaptic active zone

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Abstract

The cytomatrix at the active zone (CAZ) is a macromolecular complex that facilitates the supply of release-ready synaptic vesicles to support neurotransmitter release at synapses. To reveal the dynamics of this supply process in living synapses, we used super-resolution imaging to track single vesicles at voltage-clamped presynaptic terminals of retinal bipolar neurons, whose CAZ contains a specialized structure-the synaptic ribbon-that supports both fast, transient and slow, sustained modes of transmission. We find that the synaptic ribbon serves a dual function as a conduit for diffusion of synaptic vesicles and a platform for vesicles to fuse distal to the plasma membrane itself, via compound fusion. The combination of these functions allows the ribbon-type CAZ to achieve the continuous transmitter release required by synapses of neurons that carry tonic, graded visual signals in the retina.

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Thirumalini Vaithianathan

Department of Neurobiology and Behavior, Stony Brook University, New York, United States

Competing interests
The authors declare that no competing interests exist.
Diane Henry

Department of Neurobiology and Behavior, Stony Brook University, New York, United States

Competing interests
The authors declare that no competing interests exist.
Wendy Akmentin

Department of Neurobiology and Behavior, Stony Brook University, New York, United States

Competing interests
The authors declare that no competing interests exist.
Gary Matthews

Department of Neurobiology and Behavior, Stony Brook University, New York, United States

For correspondence
Gary.G.Matthews@stonybrook.edu

Competing interests
The authors declare that no competing interests exist.

Ethics

Animal experimentation: All animal procedures were in accord with NIH guidelines and followed protocol 247885 approved by the Institutional Animal Care and Use Committee of Stony Brook University.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.