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Dominic E Cosgrove, Marisa L Zallocchi, Linda Cheung; Functional Characterization of an Usher Protein/Integrin Interactome in Rod Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3817.
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© ARVO (1962-2015); The Authors (2016-present)
Usher syndrome is the leading genetic cause of deaf/blindness in the world. There are now 10 specific genes associated with three clinical sub-types. The genes encode an array of proteins and protein variants that specifically interact to form Usher protein complexes or “interactomes” with both known and unknown functions. We have identified a novel complex comprised of Usher proteins and integrin α8. In this study we examine whether this signaling complex functions in the light-dependent translocation of the phototransduction protein α-transducin.
Protein interactions were established using a combination of co-localization by immunohistochemistry and co-immunoprecipitation from retinal, cochlear, or zebrafish larval extracts. The functional role of the signaling complex was by analysis of α-transducin translocation thresholds in the presence and absence of the focal adhesion kinase (FAK) inhibitor TAE-226.
Based on a combination of previously published results and those presented in this work, the integrin Usher protein/integrin interactome consists of full length proteins or variants of at least Myosin VIIa (USH1B), Protocadherin 15 (USH1F), calcium integrin binding protein 2 (CIB2, USH1J), whirlin (USH2D), clarin-1 (USH3A), and integrin α8. All of these proteins localize to the periciliary region of rod photoreceptors near the connecting cilium. We found evolutionary conservation of the CIB2/integrin α8, clarin-1/integrin α8 and protocadherin 15/integrin α8 interactions in zebrafish. Treating wild type mice with the FAK inhibitor TAE226 resulted in elevated light thresholds to activate α-transducin translocation. Treatment of shaker-1 mice (MYOVIIA mutants) or Whirlin mutants with TAE226 did not affect light thresholds to activate α-transducin translocation. TAE226 treatment did not affect the localization of Usher proteins comprising the interactome or integrin α8.
A novel Usher protein/integrin α8 interactome exists at the periciliary region of rod photoreceptors that appears to play a role in the regulation of light thresholds required to activate α-transducin translocation. This interactome signals via the integrin signaling intermediate, focal adhesion kinase.
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