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Janis Lem, Fang Yang, Edward Dudek, Jesse Peterson, Jinsong Yang; Light-Regulated PKD Activation Facilitates E-Cadherin/Catenin Complex Formation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):47.
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Light activation of rhodopsin is typically associated with activation of phototransduction signaling. For several GPCRs, in addition to canonical G-protein signaling, alternate G-protein independent signaling pathways have been identified. We recently identified transducin-independent activation of protein kinase D (pPKD) in response to rhodopsin activation, identifying it as a possible alternative rhodopsin signaling pathway. Immunoprecipitation of pPKD from retinas identified α- and β-catenin complex formation. This study further examines light-mediated effects of PKD/catenin complex formation.
Lysates from dark- and light-adapted WT and transducin α-subunit null retinas were immunoprecipitated with pPKD-specific antibodies and immunoblotted with antibodies to E-cadherin, α- or β-catenin. Fluorescent immunohistochemistry was used to co-localize pPKD and catenin proteins in retina sections.
We observed a light-induced increase in pPKD levels. We also observed a correlative increase in pPKD binding to α-catenin, β-catenin and E-cadherin, key components of adherens junctions. Additionally, light-exposed retinas have increased complex formation of α- and β-catenins. Fluorescent immunohistochemistry revealed that active phosphorylated PKD co-localized with β-catenin in the outer limiting membrane.
In addition to classical phototransduction signaling, rhodopsin activation serves a non-visual function in the retina. Our results suggest that light regulates adherens junction formation in the outer limiting membrane of the adult retina. Further studies are required to investigate the physiological relevance of this light-regulated event.
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