v-Src-Mediated Phosphorylation of Connexin43 on Tyrosine Disrupts Gap Junctional Communication in Mammalian Cells

Abstract

It is not clear how the v-Src oncoprotein disrupts gap junctional communication (GJC) established by connexin43 (Cx43) in mammalian cells. In this study, an experimental system was established to stably express v-Src and wild type (wt) Cx43, or Y247F, Y265F, or Y247F/Y265F Cx43 mutants in a Cx43 knockout (KO) mouse cell line. When co-expressed with v-Src, the levels of phosphotyrosine (pTyr) from Y247F, Y265F, and Y247F/Y265F Cx43 mutants were reduced to approximately 57%, 10%, and 2% of the level of pTyr from wt Cx43, indicating that Y247 and Y265 were phosphorylation targets of v-Src in vivo. These data also implied that phosphorylation of Cx43 at Y265 was required for efficient phosphorylation of Cx43 at Y247. Most importantly, our measurements of GJC demonstrated that, in contrast to the wt Cx43 gap junction channels, the Y247F, Y265F, and Y247F/Y265F Cx43 channels were resistant to the disruption by v-Src. In conclusion, our studies support a model for processive phosphorylation of Cx43 on tyrosine, at the Y265 site followed by the Y247 site, in mediating the disruption of GJC induced by v-Src in mammalian cells.

Key Words:

• Connexin43
• gap junction
• phosphorylation
• phosphotyrosine
• v-Src