c-Src interacts with and phosphorylates RelA/p65 to promote thrombin-induced ICAM-1 expression in endothelial cells.

The procoagulant thrombin promotes polymorphonuclear leukocyte (PMN) adhesion to endothelial cells by a mechanism involving expression of intercellular adhesion molecule-1 (ICAM-1) via an NF-κB-dependent pathway. We now provide evidence that activation of c-Src is crucial in signaling thrombin-induced ICAM-1 expression via tyrosine phosphorylation of RelA/p65. Stimulation of human umbilical vein endothelial cells with thrombin resulted in a time-dependent activation of c-Src, with maximal activation occurring at 30 min after thrombin challenge. Inhibition of c-Src by pharmacological and genetic approaches impaired thrombin-induced NF-κB-dependent reporter activity and ICAM-1 expression. Analysis of the NF-κB pathway revealed that the effect of c-Src inhibition occurred independently of IκBα degradation and NF-κB DNA binding function and was not associated with exchange of NF-κB dimers. Phosphorylation of RelA/p65 at Ser536, an event mediating the transcriptional activity of DNA-bound RelA/p65, was also in...