Role of mDia1 in RAGE signaling and smooth muscle cell migration

Abstract

RAGE (Receptor for Advanced Glycation end Products) plays a pivotal role in the atherosclerotic process. The cytoplasmic binding domain of RAGE interacts with mDia‐1, a member of the formin family involved in actin and microtubule reorganization. Here we report that mDia‐1 is required for RAGE effects on vascular stress. Immunostaining of human and mice atherosclerotic tissue showed mDia‐1 expression in the atherosclerotic plaque, particularly in smooth muscle cells (SMCs). We established primary cultures of murine aortic SMCs from wild type (WT) and mDia1 null mice. Recombinant S100B was used as a prototypic RAGE ligand. We found that compared to control cells, SMCs devoid of mDia‐1 (KO or mdia1 siRNA transfected) showed significant and specific inhibition of S100B‐stimulated superoxide production, lamellopodia formation and cell migration. Interestingly, RAGE induced Rac activity and phosphorylation of AKT and GsK3beta were also greatly inhibited in these cells. In WT cells, blockade of RAGE‐induced ROS production with Diphenyiodinium or dominant negative Rac construct, significantly prevented RAGE‐induced AKT/Gsk3beta phosphorylation and SMCs migration. We concluded that in SMCs, mDia‐1 is essential for RAGE‐induced Rac1 activation and ROS production. ROS may then activate PI3Kinase and induce AKT dependent phosphorylation of GSK3beta, leading to cell migration.