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.
Henzl
Michael T
MT
Department of Biochemistry, University of Missouri - Columbia, 117 Schweitzer Hall, Columbia, MO 65211, USA. henzlm@missouri.edu
Thalmann
Isolde
I
Larson
John D
JD
Ignatova
Elena G
EG
Thalmann
Ruediger
R
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D000072259:Connexin 26; D017630:Connexins / Q000032:analysis* / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D024202:Electrophoretic Mobility Shift Assay; D044783:F-Box Proteins; D006168:Guinea Pigs; D006801:Humans; D047468:Immunoprecipitation; D016018:Least-Squares Analysis; D009419:Nerve Tissue Proteins; D009925:Organ of Corti / Q000378:metabolism*; D010453:Peptide Synthases / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins; D014157:Transcription Factors / Q000032:analysis* / Q000737:chemistry; D014461:Ultracentrifugation
D018797:Cell Cycle Proteins; D017630:Connexins; D044783:F-Box Proteins; C485508:FBXO2 protein, human; C000607042:GJB2 protein, human; D009419:Nerve Tissue Proteins; D044786:S-Phase Kinase-Associated Proteins; C097351:SKP1 protein, human; D014157:Transcription Factors; D000072259:Connexin 26; D010453:Peptide Synthases