Different modes of endothelial-smooth muscle cell interaction elicit differential β-catenin phosphorylations and endothelial functions

Abstract

beta-Catenin phosphorylation plays important roles in modulating its functions, but the effects of different phosphorylated forms of beta-catenin in response to heterocellular interaction are unclear. Here we investigated whether distinct modes of phosphorylation on vcatenin could be triggered through heterocellular interactions between endothelial cells (ECs) and smooth muscle cells (SMCs), and the consequent modulation of EC functions. ECs were cocultured with SMCs to initiate direct contact and paracrine interaction. EC-SMC coculture induced EC beta-catenin phosphorylations simultaneously at tyrosine 142 (Tyr142) and serine 45/threonine 41 (Ser45/Thr41) at the cytoplasm/nuclei and the membrane, respectively. Treating ECs with SMC-conditional medium induced beta-catenin phosphorylation only at Ser45/Thr41. These findings indicate that different phosphorylation effects of EC-SMC coculture were induced through heterocellular direct contact and paracrine effects, respectively. Using specific blocking peptides, antagonists, and siRNAs, we found that the beta-catenin Tyr142-phosphorylation was mediated by connexin 43/Fer and that the beta-catenin Ser45/Thr41-phosphorylation was mediated by SMC-released bone morphogenetic proteins through VE-cadherin and bone morphogenetic protein receptor-II/Smad5. Transfecting ECs with beta-cateninTyr142 or -Ser45 mutants showed that these two phosphorylated forms of beta-catenin modulate differential EC function: The Tyr142phosphorylated beta-catenin stimulates vascular cell-adhesion molecule-1 expression to increase EC-monocytic adhesion, but the Ser45/Thr41-phosphorylated beta-catenin attenuates VE-cadherin-dependent junction structures to increase EC permeability. Our findings provide new insights into the understanding of regulatory complexities of distinct modes of beta-catenin phosphorylations under EC-SMC interactions and suggest that different phosphorylated forms of beta-catenin play important roles in modulating vascular pathophysiology through different heterocellular interactions.