Csk-Induced Phosphorylation of Src at Tyrosine 530 is Essential for H(2)O(2)-Mediated Suppression of ERK1/2 in Human Umbilical Vein Endothelial Cells

Mitogen-activated protein kinases (MAPKs) are key signal transducers involved in various cellular events such as growth, proliferation, and differentiation. Previous studies have reported that H(2)O(2) leads to phosphorylation of extracellular signal-regulated kinase (ERK), one of the MAPKs in endothelial cells. The current study shows that H(2)O(2) suppressed ERK1/2 activation and phosphorylation at specific concentrations and times in human umbilical vein endothelial cells but not in immortalized mouse aortic endothelial cells or human astrocytoma cell line CRT-MG. Phosphorylation of other MAPK family members (i.e., p38 and JNK) was not suppressed by H(2)O(2). The decrease in ERK1/2 phosphorylation induced by H(2)O(2) was inversely correlated with the level of phosphorylation of Src tyrosine 530. Using siRNA, it was found that H(2)O(2)-induced suppression of ERK1/2 was dependent on Csk. Physiological laminar flow abrogated, but oscillatory flow did not affect, the H(2)O(2)-induced suppression of ERK1/2 phosphorylation. In conclusion, H(2)O(2)-induced Csk translocation to the plasma membrane leads to phosphorylation of Src at the tyrosine 530 residue resulting in a reduction of ERK1/2 phosphorylation. Physiological laminar flow abrogates this effect of H(2)O(2) by inducing phosphorylation of Src tyrosine 419. These findings broaden our understanding of signal transduction mechanisms in the endothelial cells against oxidative stress.