Abstract
The blood vessel wall is a complex structure and is highly modulated by homo- or heterocellular communications, such as cytokine release or cell-cell direct contact. In this study, I aim to elucidate the influence of direct heterocellular contact between endothelial cells (ECs) and smooth muscle cells (SMCs) by using a vascular cell co-culture model that is composed of monolayers of ECs and SMCs on opposite sides of a membrane. Under this co-culture system, the interaction between ECs and SMCs resulted in the phosphorylation of beta-catenin at tyrosine 142 (Tyr142) and serine 45/threonine 41 (Ser45/Thr41). ECs treated with SMC conditional medium induced beta-catenin phosphorylation at Ser45/Thr41 but not at Tyr142. The co-culture with fibroblasts (FBs) did not induce any beta-catenin phosphorylation. Moreover, by pre-treating cells with blocking peptides and using specific siRNA transfection, I demonstrated that connexin 43 modulated the phosphorylatin of beta-catenin-Tyr142 via Fer kinase. Transfecting ECs with siRNA specific for Cx43 or beta-catenin or beta-catenin-Tyr142 constitutive negative mutants inhibited vascular adhesion molecule-1 (VCAM-1) gene expression and thus modulated EC monocyte adhesion. These results indicate that vascular heterocellular communication regulates EC inflammation by inducing beta-catenin-Tyr142 phosphorylation through Cx43/Fer signaling via direct contact effects. My findings provide insights into the complexities of beta-catenin phosphorylation signaling in vascular cells, the mechanisms underlying the EC-SMC cross interaction in modulating signaling and gene expression in ECs and the consequent modulation of their inflammatory functions.