Regulation of gap junctions by phosphorylation of connexins

Gap junctions are a unique type of intercellular junction found in most animal cell types. Gap junctions permit the intercellular passage of small molecules and have been implicated in diverse biological processes, such as development, cellular metabolism, and cellular growth control. In vertebrates, gap junctions are composed of proteins from the "connexin" gene family. The majority of connexins are modified posttranslationally by phosphorylation, primarily on serine amino acids; however, phosphotyrosine has also been detected in connexin from cells coexpressing nonreceptor tyrosine protein kinases. Connexins are targeted by numerous protein kinases, of which some have been identified: protein kinase C, mitogen-activated protein kinase, and the v-Src tyrosine protein kinase. Phosphorylation has been implicated in the regulation of a broad variety of connexin processes, such as the trafficking, assembly/disassembly, degradation, as well as the gating of gap junction channels. This review examines the consequences of connexin phosphorylation for the regulation of gap junctional communication.