Abstract 139: Post-Translational Modifications of Connexins in Neointimal Formation

Intro Connexins are integrally involved in the process of cell division and atherosclerosis. Recently we identified that connexin 43 (Cx43) could significantly alter smooth muscle cell proliferation in vitro and in vivo. We now investigate the involvement of Cx43 in human neointimal formation and the mechanisms through which it controls cell cycle. Methods Protein interactions between Cx43 were identified in smooth muscle cells through co-immunoprecipitation, immuno-transmission electron microscopy and proximity ligation assays. Novel mice with alanine substitutions at MAPK phosphorylated serines (Cx43-MK4A) were investigated. Samples from diseased and non-diseased human coronary arteries were assessed for level of Cx43 phosphorylation and interactions. Ex vivo saphenous vein explant cultures were used to assess the contribution of Cx43 phosphorylation to human neointimal formation. In vitro studies were performed in human coronary artery smooth muscle cells and in mouse aortic smooth muscle cells from wild type and knockout mice. Results We demonstrate that levels of Cx43 are increased in human atherosclerotic plaques and that neointimal formation in human tissues corresponds to a significant increase in Cx43 phosphorylation and cyclin E interactions. In vitro, Cx43 facilitates trafficking of cyclin E to the nucleus in a manner that is dependent on its MAPK phosphorylation. Discussion Our studies suggest that in human vascular disease and neointimal formation Cx43 interactions with cyclin E are elevated. Further, Cx43 facilitates the transport of the cell cycle promoter cyclin E to the nucleus suggesting that this is a critical component of VSMC proliferation and therefore could be a novel target in the prevention of neointimal formation in human vascular disease.