Connexin 43 (Cx43) is a member of the large family of gap junction proteins. Connexins assemble as a hexamer and are transported to the plasma membrane to create a hemichannel that can associate with hemichannels on nearby cells to create cell-to-cell channels. Clusters of these channels assemble to make gap junctions. Gap junction communication is important in development and regulation of cell growth. Phosphorylation of Cx43 is important in regulating assembly and function of gap junctions. Ser368 of Cx43 is phosphorylated by protein kinase C (PKC) after activation by phorbol esters, which decreases cell-to-cell communication. Src can interact with and phosphorylate Cx43 to alter gap junction communication.