Ca2+ regulation of Drosophila phototransduction

Abstract

Drosophila vision research has benefited from simultaneous application of genetic, molecular, electrophysiological analyses. The work establishes an essential role of Ca2+ in regulation of phototransduction. Many different proteins are the targets of Ca2+ regulation and these proteins act at multiple steps of the process. These targets include proteins involved in the rhodopsin cycle, proteins responsible for intermediate steps of phototransduction, and the TRP and TRPL light-gated channels. The regulation of these phototransduction components by Ca2+ occurs in three different ways. First, the presence of Ca2+/calmodulin-binding sites in phototransduction-mediating proteins places these proteins under Ca2+ control. Second, a protein kinase C regulated by Ca2+ phosphorylates proteins to modulate their activity. Finally, some proteins contain Ca2+-binding sites and apparently are directly regulated by Ca2+. Here I review the photoreceptor proteins regulated by Ca2+, and summarize current views on the roles of these proteins in the Drosophila photoresponse.