The cochlear F-box protein OCP1 associates with OCP2 and connexin 26

OCP1 and OCP2 are the most abundant proteins in the organ of Corti. Their distributions map identically to the epithelial gap-junction system, which unites the supporting cell population. Sequence data imply that OCP1 and OCP2 are subunits of an SCF E3 ubiquitin ligase. Consistent with that hypothesis, electrophoretic mobility-shift assays and pull-down assays with immobilized OCP1 demonstrate the formation of an OCP1-OCP2 complex. Sedimentation equilibrium data indicate that the complex is heterodimeric. The coincidence of the OCP1-OCP2 distribution and the epithelial gap-junction system suggests that one or more connexin isoforms may be targets of an SCF(OCP1) complex. Significantly, immobilized OCP1 binds (35)S-labeled connexin 26 (Cx26) produced by in vitro transcription-translation. Moreover, Cx26 can be co-immunoprecipitated from extracts of the organ of Corti by immobilized anti-OCP1, implying that OCP1 and Cx26 may associate in vivo. Given that lesions in the Cx26 gene (GJB2) are the most common cause of hereditary deafness, the OCP1-Cx26 interaction has substantial biomedical relevance.