Retinal functions in both vertebrates and invertebrates are regulated by light and a circadian clock. In the horseshoe crab, Limulus polyphemus, the interactions of light and a circadian clock on retinal structure and function are particularly well characterized. The goal of these studies is to clarify the largely unknown biochemical substrates and mechanisms underlying the effects of, and the interactions between, light and the circadian clock on the retina. Two interesting substrates have been identified. One, pp46A, probably participates in a light-driven pathway modulated by the circadian clock. The other pp122, is in a clock-driven pathway that is probably modulated by light. The hypothesis that pp46A quenches the transduction cascade initiated by light and that pp122 is critical for clock-driven changes in the structure of the photoreceptor that occur at night will be investigated. Molecular, biochemical and immunochemical approaches will be applied to characterize these proteins and their functions. The interactions between light and a circadian clock in regulation of proteins critical for retinal function, opsin, pp46A and pp122, will be determined. These studies will provide new knowledge of the biochemical processes that underlie the day to night changes in the retina that are required for normal vision.
