Injury-triggered Akt phosphorylation of Cx43: a ZO-1-driven molecular switch that regulates gap junction size

Abstract

The proteins that form vertebrate gap junctions, the connexins, are highly regulated and have short (< 2 h) half-lives. Phosphorylation of connexin43 (Cx43) is generally known to affect gap junction assembly, channel gating and turnover. After finding dramatic effects on gap junctions with Akt inhibitors, we created an antibody specific for Cx43 phosphorylated on S373, a potential Akt substrate. We found S373 phosphorylation in cells and skin or heart almost exclusively in larger gap junctional structures that increased dramatically after wounding or hypoxia. We were able to mechanistically show that Akt-dependent S373 phosphorylation increases gap junction size and communication by completely eliminating interaction between Cx43 and ZO-1. Thus, phosphorylation on S373 acts as a molecular “switch” to rapidly increase gap junctional communication potentially leading to initiation of activation and migration of keratinocytes or ischemic injury response in skin and heart, respectively.