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Am J Physiol Lung Cell Mol Physiol. 2007 Feb;292(2):L396-404. Epub 2006 Sep 29.

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

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  • 1Department of Pediatrics, Lung Biology and Disease Program, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.


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-kappaB-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-kappaB-dependent reporter activity and ICAM-1 expression. Analysis of the NF-kappaB pathway revealed that the effect of c-Src inhibition occurred independently of IkappaBalpha degradation and NF-kappaB DNA binding function and was not associated with exchange of NF-kappaB dimers. Phosphorylation of RelA/p65 at Ser(536), an event mediating the transcriptional activity of DNA-bound RelA/p65, was also insensitive to c-Src inhibition. Interestingly, thrombin induced association of c-Src with RelA/p65, and inhibition of c-Src prevented this response, indicating that this interaction is contingent on activation of c-Src. We also observed that thrombin induced tyrosine phosphorylation of RelA/p65, and this phosphorylation was lost upon inhibition of c-Src, consistent with the requirement of activated c-Src for interaction with RelA/p65. These data implicate an important role of c-Src in phosphorylating RelA/p65 to promote the transcriptional activity of NF-kappaB and thereby ICAM-1 expression in endothelial cells.

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