Biology and Biomedical Sciences: Molecular Cell Biology
Date of Award
Doctor of Philosophy (PhD)
Chair and Committee
Kendall J Blumer
ABSTRACT OF THE DISSERTATION
Characterization of the Role of RGS7-family Proteins in Mammalian Retina and Vision
Matthew David Cain
Doctor of Philosophy in Biology and Biomedical Sciences
Molecular Cell Biology
Washington University in St. Louis, 2014
Professor Kendall J. Blumer, Chairperson
GPCR/G protein signaling is a critical component of neuronal signal transduction and function. G protein signaling is regulated by a family of regulator of G protein signaling (RGS) proteins that act as GTPase activating proteins (GAPs) for Gα subunits. In the retina, the R7-RGS family of RGS proteins which specifically act as GAPs toward Gi/o, are critical regulators of phototransduction and ON bipolar cell light responses in the outer retina. While R7-RGS proteins are expressed throughout the inner retina, their function there is unknown. The goal of this dissertation project is to characterize R7-RGS regulation on retina function and vision.
This dissertation is divided into four parts: i) analysis of inner retinal function in mature and developing R7BP-/- retinas, ii) characterization of composition and localization of R7-RGS/R7BP complexes in the dorsal lateral geniculate nucleus (dLGN), iii) characterization of blockade of RGS regulation of Gi2 and Go subunits on outer retina function, and iv) preliminary analysis of the effect of RGS6 ablation on vision. In part i), we found that R7BP is expressed in starburst amacrine cells (SAC) and retinal ganglion cells (RGC). R7BP regulates mesopic RGC light responses and glutamatergic wave burst duration in mature and developing retina, respectively. In part ii), we found that R7PB is expressed in the dLGN. R7BP interacts with RGS6 and RGS7 in lateral geniculate nucleus lysates, but is not necessary for their membrane localization. In part iii), outer retinal phenotypes of RGS-insensitive Gi2 and Go mutant mice were characterized. RGS regulation of Gi2 is necessary for normal rod light responses. Heterozygous expression of RGS-insensitive Go subunits was not sufficient to perturb ON bipolar cell light responses or dendritic morphology. In part iv), we found that RGS6 is expressed in starburst amacrine cells. RGS6 localization to SAC plexi is independent of R7BP. We demonstrated that, although dispensable for normal phototransduction or ON bipolar light responses, RGS6 is necessary for normal spatial vision. Based on these findings, we suggest that RGS regulation of Gi/o signaling is necessary for normal retinal function and that R7-RGS proteins regulate inner retinal function. Additionally, we identified several new candidate circuits to further explore R7-RGS function in the visual system.
Cain, Matthew D., "Characterization of the Role of R7-RGS Proteins in Mammalian Retina and Vision" (2014). All Theses and Dissertations (ETDs). 1288.