Molecular Medicine Phosphorylation of Smooth Muscle 22 Facilitates Angiotensin II–Induced ROS Production Via Activation of the PKC-P47phox Axis Through Release of PKC and Actin Dynamics and Is Associated With Hypertrophy and Hyperplasia of Vascular Smoo

Rationale: We have demonstrated that smooth muscle (SM) 22 inhibits cell proliferation via blocking Ras-ERK1/2 signaling in vascular smooth muscle cells (VSMCs) and in injured arteries. The recent study indicates that SM22 disruption can independently promote arterial inflammation through activation of reactive oxygen species (ROS)-mediated NF-B pathways. However, the mechanisms by which SM22 controls ROS production have not been characterized. Objective: To investigate how SM22 disruption promotes ROS production and to characterize the underlying mechanisms. Methods and Results: ROS level was measured by dihydroethidium staining for superoxide and TBA assay for malondialdehyde, respectively. We showed that downregulation and phosphorylation of SM22 were associated with angiotensin (Ang) II–induced increase in ROS production in VSMCs of rats and human. Ang II induced the phosphorylation of SM22 at Serine 181 in an Ang II type 1 receptor–PKC pathway–dependent manner. Phosphorylated SM22 activated the protein kinase C (PKC)-p47phox axis via 2 distinct pathways: (1) disassociation of PKC from SM22, and in turn binding to p47phox, in the early stage of Ang II stimulation; and (2) acceleration of SM22 degradation through ubiquitin-proteasome, enhancing PKC membrane translocation via induction of actin cytoskeletal dynamics in later oxidative stress. Inhibition of SM22 phosphorylatio