Vascular Endothelial Structural Biochemistry

Vascular endothelium forms a selective barrier and regulates the trafficking of macromolecules and blood cells across the vessel wall. The integrity of the endothelial barrier is highly dependent on the actin– myosin-based endothelial contractile machinery.1,2 Activation of the contractile machinery is triggered by phosphorylation of the regulatory myosin light chains (MLC), which is balanced by endothelial Ca2+– calmodulin-dependent MLC kinase and MLC phosphatase (MLCP).3,4
In the context of the present study MLCP is of special interest. The endothelial MLCP is a heterotrimeric enzyme composed of a catalytic subunit, PP1, a regulatory myosin phosphatase targeting subunit
(MYPT1), and a 20-kDa subunit of yet unknown function.5,6 In smooth muscle cells, it is well established that the activity of MLCP is controlled …show more content…
by Rho kinase (Rock), which phosphorylates MYPT1 at its inhibitory sites,7 and the endogenous inhibitor of PP1, CPI-17 (PKC-potentiated inhibitory protein for PP1 of 17 kDa).8,9 However, in endothelial cells, the regulation of MLCP is not completely