Abstract 16025: Phosphorylation of Endothelial Nitric Oxide Synthase at Ser633 by a Novel Protein Kinase Pim1

Background: Endothelium-derived nitric oxide, which produced by endothelial Nitric Oxide synthase (eNOS), has been implicated in the regulation of a variety of vascular functions, including vessel relaxation, vascular inflammation, and thrombotic formation. The activity of eNOS in endothelia cells (EC) is largely regulated by posttranslational modifications, such as phosphorylation. Indeed, several phosphorylation sites, including Ser114, Thr495, Ser615, Ser633, and Ser1177, Tyr657 (in human), have been identified and phosphorylation of NOS at Ser633 has been implicated in the regulation of eNOS activity in ECs, in response to shear stress and VEGF stimulation. The protein kinase(s) responsible for eNOS phosphorylation at Ser633, however, remains largely unknown. Methods and Results: In this study, we, for the first time, identified a protein kinase, Pim1, as a novel kinase that mediates eNOS phosphorylation at Ser633. The interaction between Pim1 and eNOS was determined by co-IP of Pim1 and eNOS in nativ...