Dual use of the transcriptional repressor (CtBP2)/ribbon synapse (RIBEYE) gene: how prevalent are multifunctional genes?

Abstract

Vertebrates have ribbon synapses in the retina and in other sensory structures that are specialized for rapid, tonic release of synaptic vesicles (1). The lamellar sheets of the ribbon situated at right angles to the plasma membrane are lined with synaptic vesicles that undergo exocytosis under the influence of Ca(2+). Synaptic ribbons act as a conveyer belt to accelerate the release of this ready supply of synaptic vesicles at the presynaptic membranes. Although the protein composition of the terminals of ribbon synapses is generally similar to that of ordinary synapses in nervous tissue, much less is known about the composition of the ribbons themselves. RIM, a universal component of presynaptic active zones that interacts with rab3 on the synaptic vesicle, has been localized to the ribbons (2). In addition, the kinesin motor protein, KIF3A, is associated with the ribbons and other organelles in presynaptic nerve terminals (3). Recently, an approximately 120 kDa protein called RIBEYE has been identified in purified ribbons of bovine retina. The RIBEYE cDNA was cloned and its gene identified in the database.