Visual Neuroscience

Review Article

The dynamic architecture of photoreceptor ribbon synapses: Cytoskeletal, extracellular matrix, and intramembrane proteins

AARON J. MERCERa1a2 and WALLACE B. THORESONa1a2 c1

a1 Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska

a2 Department of Pharmacology & Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska

Abstract

Rod and cone photoreceptors possess ribbon synapses that assist in the transmission of graded light responses to second-order bipolar and horizontal cells of the vertebrate retina. Proper functioning of the synapse requires the juxtaposition of presynaptic release sites immediately adjacent to postsynaptic receptors. In this review, we focus on the synaptic, cytoskeletal, and extracellular matrix proteins that help to organize photoreceptor ribbon synapses in the outer plexiform layer. We examine the proteins that foster the clustering of release proteins, calcium channels, and synaptic vesicles in the presynaptic terminals of photoreceptors adjacent to their postsynaptic contacts. Although many proteins interact with one another in the presynaptic terminal and synaptic cleft, these protein–protein interactions do not create a static and immutable structure. Instead, photoreceptor ribbon synapses are remarkably dynamic, exhibiting structural changes on both rapid and slow time scales.

(Received June 06 2011)

(Accepted September 06 2011)

Correspondence:

c1 Address correspondence and reprint requests to: Wallace B. Thoreson, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, 4050 Durham Research Center, Omaha, NE 68198-5840. E-mail: wbthores@unmc.edu