Shear-induced dissociation of Gaq-PECAM-1 at endothelial cell junctions

Summary form only given. As the inner lining of the vessel wall, vascular endothelial cells are poised to act as a signal transduction interface for hemodynamic forces. The molecular mechanisms of the primary force sensing elements of the cell, and the cascade of events that are involved in the mechanochemical signal pathway remain unclear. Activation of the G protein Gaq and the phosphorylation of platelet endothelial cell adhesion molecule-1 (PECAM-1) have been reported to be involved in the early events of shear-induced signaling pathways. Using immunofluorescence and co-immunoprecipitation techniques, we demonstrate here for the first time that Gaq and PECAM-1 co-localize as a complex at the cell-cell junction in primary human umbilical vein endothelial cells. Temporal gradients in shear stress lead to a rapid disassociation and re-association of the Gaq-PECAM-1 complex within 15 sec (0.65 ± 0.059 ratio Gaq/PECAM-1 versus sham control), whereas slowly transitioning fluid flow devoid of temporal gradients does not disrupt the complex (1.04 ± 0.08 ratio Gq/PECAM-1 versus Sham control). Inhibition of protein kinases and tyrosine kinases completely eliminated impulse flow induced Gaq-PECAM-1 disassociation and PECAM-1 phosphorylation. Taken to together, this data may represent a missing link between the primary force sensing elements of the cell, and the downstream mechanochemical transduction pathway.