Abstract
Abstract: :
Purpose: To analyze the light-dependent movement of phototransduction proteins between the inner segments and the outer segments of rod photoreceptor cells. Methods: Mice or Xenopus frogs were exposed to light or darkness for various periods of time, killed, their eyes enucleated, fixed, embedded, sectioned and processed for either standard or confocal immunofluorescence microscopy using antibodies against arrestin or beta-Transducin. Results: In the retinas of dark-adapted mice, arrestin is located in the rod inner segment (RIS) and transducin is in the rod outer segment (ROS). In light-adapted retinas, the proteins have reciprocal localizations. The temporal and spatial changes in the subcellular localization of arrestin and ß-transducin are correlated with the amount of light to which the animals are exposed. Using the Xenopus laevis frog and immunofluorescence confocal microscopy, our results also show that in the dark-adapted retina, some arrestin remains in the ROS. The data most dramatically demonstrate that this residual arrestin is highly concentrated in the connecting cilium, the axoneme and the microtubules associated with the disc incisures. Conclusion: These data suggest a structure/function relationship between the light-dependent positional status of arrestin and the elements of the rod photoreceptor cytoskeleton. The massive, rapid, light-induced reciprocal changes in the subcellular concentrations of these proteins must directly affect phototransduction and appear to be a general phenomenon by which photoreceptor cells rapidly and transiently regulate the trafficking and subcellular concentration of a variety of signal transduction proteins within the RIS and ROS. Hereditary mutations in the components of the movement mechanism should lead to defects in vision and possibly blindness.CR: None. Support: NIH grants EY 06085, 13050 and 12190, Presbyterian Health Foundation, a Jules and Doris Stein Professorship from Research to Prevent Blindness to JFM, and by an unrestricted grant from RPB to the Department of Ophthalmology.
Keywords: 384 dark/light adaptation • 474 microscopy: light/fluorescence/immunohistochemistry • 517 photoreceptors