Role of Ca2+/Calmodulin‐dependent Protein Kinase II (CaMKII) in Endothelial Cells

Abstract

Endothelial cell (EC) barrier function and angiogenesis are partially dependent upon increases of intracellular free Ca2+ through G‐protein coupled receptor (GPCR) agonists such as thrombin and vascular endothelial growth factor (VEGF). The goal of these studies is to fully characterize the endogenous CaMKII isoform(s) in endothelial cells, and to test the hypothesis that the multifunctional Ca2+/calmodulin‐dependent serine/threonine protein kinase II (CaMKII), responds to thrombin‐ and VEGF‐stimulated Ca2+ signals and regulates EC barrier function and angiogenesis. For the 1st time, by RT‐PCR and western blotting, we successfully characterized the predominant CaMKII isoform expressed in cultured human umbilical vein endothelial cells (HUVEC) is the delta 6 (δ6) isoform, a novel δ‐isoform lacking the 21aa c‐terminal domain. We utilized siRNA approach to suppress CaMKIIδ6 protein expression and found it attenuated, only low dose (2.5nM) but not high dose (10nM), of thrombin‐induced increase of EC permeability. These data suggest a role of CaMKIIδ6 in mediating changes in barrier function in response to physiological relevant doses of thrombin. By using the same approach, we found that CaMKIIδ6 is pivotal in regulating VEGF induced HUVEC migration through Boyden Chamber. This work was supported by NIH grant to H.A.S (R01 HL‐049426).Grant Funding SourceNIH grant to H.A.S (R01 HL‐049426).