Coronin 1B Regulates Platelet-derived Growth Factor-induced Migration and Reactive Oxygen Species Production

Platelet derived growth factor (PDGF) plays a pivotal role in cardiovascular disease progression, partially by initiating vascular smooth muscle cell (VSMC) migration Lamellipodia formation is the first step in migration and the creation of this actin rich protrusion is under the tight control of actin polymerizing proteins such as the Arp2/3 complex and actin depolymerizing proteins such as cofilin. Studies show that the actin binding proteins known as coronins regulate actin polymerization via binding to and inhibiting the ARP2/3 complex. Coronins are known to regulate various actin dependent cellular processes including migration. However, the existence and role of coronins in vascular smooth muscle cell (VSMC) migration has yet to be determined. Therefore, the goal of this dissertation was to define the mechanism by which coronins regulate platelet-derived growth factor (PDGF)-induced VSMC migration.;Coronin 1B (Coro1B) and 1C (Coro1C) are both expressed in VSMCs at the mRNA and protein levels. Downregulation of Coro1B by siRNA increases PDGF-induced migration, while downregulation of Coro1C has no effect. Through kymograph analysis, it was confirmed that Coro1B-mediated increases in migration are directly linked to increased lamellipodial protraction rate and protrusion distance in VSMC. Additionally, PDGF induces phosphorylation of Coro1B on serine-2 via PKCepsilon, leading to a decrease in the interaction of Coro1B with the Arp2/3 complex. VSMCs transfected with a phospho-deficient S2A-Coro1B mutant showed decreased migration in response to PDGF, suggesting that the phosphorylation of Coro1B is required for the promotion of migration by PDGF. In both the rat and mouse, Coro1B phosphorylation is increased in response to vessel injury in vivo. We also found that the Coro1B phosphorylation state is redox sensitive and dephosphorylation of Coro1B is dependent on an okadaic acid sensitive phosphatase. Furthermore, the knockdown of Coro1B increases PDGF-induced NADPH oxidase-derived ROS production, thereby providing a new avenue by which Coro1B can regulate VSMC migration. Our data support the concept that Coro1B is an important participant in PDGF-induced VSMC migration, a critical step in vascular lesion formation.