The kinases c-Src (Giepmans et al. 2001; Sorgen et al. 2004), PKc (Lin et al. 2003) and MAPK (Mograbi et al. 2003) play an essential role in the phosphorylation of Cx which leads to its degradation. c-Src appears to associate with and phosphorylate Cx43 leading to closure of gap junctions. Evidence suggests that v-src may activate MAPK, which in turn phosphorylates Cx43 on serine sites leading to channel gating (Zhou et al. 1999).