Unconventional myosin VIIA is a novel A-kinase-anchoring protein

To gain an insight into the cellular function of the unconventional myosin VIIA, we sought proteins interacting with its tail region, using the yeast two-hybrid system. Here we report on one of the five candidate interactors we identified, namely the type I alpha regulatory subunit (RI alpha) of pro tein kinase A. The interaction of RI alpha with myosin VIIA tail was demons trated by coimmunoprecipitation from transfected HEK293 cells. Analysis of deleted constructs in the yeast two-hybrid system showed that the interacti on of myosin VIIA with RI alpha involves the dimerization domain of RI alph a. In vitro binding assays identified the C-terminal "4.1, ezrin, radixin, moesin" (FERM)-like domain of myosin VIIA as the interacting domain. In hum ans and mice, mutations in the myosin VIIA gene underlie hereditary hearing loss, which may or may not be associated with visual deficiency, Immunohis tofluorescence revealed that myosin VILA and RI alpha are coexpressed in th e outer hair cells of the cochlea and rod photoreceptor cells of the retina . Our results strongly suggest that myosin VILA is a novel protein kinase A -anchoring protein that targets protein kinase A to definite subcellular si tes of these sensory cells.