Connexin 37 Growth Suppressive Phenotype is Regulated in a Site-Specific, Phosphorylation-Dependent Manner

Abstract

Connexins support the coordinated function of virtually all tissues in the body through facilitation of intercellular, transmembrane, and intracellular signaling. Connexin 37 (Cx37), which plays a role in vascular development and remodeling, has growth suppressive properties that depend on its channel function and the presence and phosphorylation status of its carboxylterminus (CT). In settings of injury, Cx37 expression is reduced - a change permissive to vascular repair. Serine 319 (S319) is a high probability (>90%) target for phosphorylation by growth factor-activated kinases, and the phosphorylation status of this site is important to the inflammatory response to injury and atherosclerosis. Here, we substituted S319 with alanine or aspartate, to mimic the dephosphorylated (S319A) and phosphorylated (S319D) states, respectively, and transfected rat insulinoma (Rin) cells with these mutants to elucidate the mechanistic basis for phospho-form specific roles of Cx37-S319 in growth control. Both mutants formed functional gap junction channels, but Cx37-S319A relieved the growth suppressive effect of Cx37, whereas Cx37-S319D did not. Altogether, these data suggest that preventing phosphorylation at S319 is sufficient to relieve the growth suppressive effect of Cx37, but the mechanistic basis for this effect is likely through induced changes in protein-protein interactions.