TYROSINE PHOSPHORYLATION OF CONNEXIN-43 BY V-SRC IS MEDIATED BY SH2 AND SH3 DOMAIN INTERACTIONS

Reduction of gap junctional communication in v-src transformed cells i s accompanied by tyrosine phosphorylation of the gap junction protein, connexin 43 (Cx43). Cx43 is phosphorylated on tyrosine by v-Src. The Src homology 3 (SH3) and Src homology 2 (SH2) domains of v-Src mediate interactions with substrate proteins. SH3 domains interact with proli ne-rich peptide motifs. SH2 domains associate with short amino acid se quences containing phosphotyrosine. We present evidence that the SH3 a nd SH2 domains of v-Src bind to proline-rich motifs and a phosphorylat ed tyrosine residue in the C-terminal tail of Cx43. Cx43 bound to the SH3 domain of v-Src, but not c-Src, in vitro. Tyrosine-phosphorylated Cx43 bound to the SH2 domain of v-Src in vitro. v-Src coprecipitated w ith Cx43 from v-src-transformed Rat-1 fibroblasts. Mutations in the SH 3 and SH2 domains of v-Src, and in the proline-rich region or tyrosine 265 of Cx43, reduced interactions between v-Src and Cx43 in vivo. Tyr osine phosphorylation of Cx43 was dependent on the association of v-Sr c and Cx43. These results provide further evidence for the direct invo lvement of v-Src in tyrosine phosphorylation of Cx43 and inhibition of gap junctional communication in v-src-transformed cells.