Direct connexin-26 interactions with membrane proteins functionally relevant to the cochlea

Connexin 26, the protein encoded by the GJB2 (Gap junction protein beta 2) gene, is expressed in different tissues, including the cochlea and skin. Pathogenic DNA alterations in GJB2 cause autosomal recessive nonsyndromic hearing loss, whereas some GJB2 variants may lead to deafness-associated skin disorders. Genes encoding proteins of the Connexin26 molecular complex may fit as candidates to explain genetic hearing loss of yet unknown etiology. In search for Connexin26 direct protein partners, 120 million clones of a human fetal brain cDNA library were screened for interaction with full-length Cx26 in a membrane yeast two-hybrid assay. Each Connexin26-interacting protein was submitted to a pipeline of in-silico characterization yielding a total of 40 direct interactors. It was disclosed that the mouse Gjb2 gene orthologue is coexpressed with 38 (95%) and 28 (70%) of the genes encoding Connexin26 interactors, respectively in specific cochlea cell types and embryonic keratinocytes. Interactors expressed in the organ of Corti supporting cells are significantly enriched in the gene ontology class of proteins with transporter activity (N = 10; 26%), seven of which are ion transporters. Nine interactor-encoding genes are either associated with deafness and/or skin disorders or have chromosomal mapping overlapping non-syndromic hearing loss-related loci. Altogether, the Connexin26 membrane interaction network highlights proteins with biological relevance to the physiology of cochlea and skin.