The carboxyl tail of Cx43 augments p38 mediated cell migration in a gap junction-independent manner.

The expression of connexin 43 (Cx43) has been shown to correlate with an enhanced migration of several cell types such as glioma or neural crest cells, but the mechanism remains unclear. We studied whether Cx43 also affects migration in non-neural cells and whether or not this is related to gap junction formation. Therefore, we analysed the migratory activity of HeLa cells under conditions of controlled connexin (Cx) expression. The expression of Cx43 enhanced their migration significantly as compared to Cx deficient wild-type cells. Expression of only the carboxyl tail of Cx43 (Cx43CT, AA 257-382) without channel forming capacity enhanced migration similarly as the full length protein. In contrast, the expression of the N-terminal part of Cx43 (Cx43NT, AA 1-257), which partially retained the gap junction channel function of Cx43, did not increase migration. The enhanced cell migration of HeLa cells expressing either full length Cx43 or the Cx43CT was associated with an increased activation of the p38 MAP kinase. The additional incubation with a specific inhibitor of p38 activation diminished the migration of HeLa-Cx43 cells to levels of control transfected cells. As a proof of concept, we studied whether Cx43 also modulates the migration of endothelial progenitor cells (EPC) which play an important role in angiogenesis. In these cells, which expressed Cx43 as the only connexin, the downregulation of Cx43 by siRNA resulted in a significantly decreased migration. These results demonstrate that expression of Cx43 augments migration via modulation of p38 MAP kinase activity. The carboxyl tail of Cx43 plays an essential role in this signalling pathway which is independent of gap junction function.