Up-regulation of phosphorylation of focal adhesion kinase and paxillin by combination of substance P and IGF-1 in SV-40 transformed human corneal epithelial cells.

We previously reported that substance P (SP) and insulin-like growth factor-1 (IGF-1) synergistically facilitate corneal epithelial migration in vitro and in vivo. We wanted to determine whether proteins responsible for cellular attachment are activated in corneal epithelial cells. To do this, we examined changes in tyrosine phosphorylation in focal adhesion kinase (FAK) and paxillin in cultured SV-40 transformed human corneal epithelial cells (HCE cells). HCE cells were cultured in the absence or presence of either SP (2 x 10(-5) M) or IGF-1 (10 ng/ml) or both SP and IGF-1. Treatment of HCE cells by either SP or IGF-1 alone did not alter tyrosine phosphorylation in either FAK or paxillin. However, the combination of SP and IGF-1 significantly increased tyrosine phosphorylation in both FAK and paxillin. In contrast, the combination of SP and IGF-1 was not observed to produce synergistic effects on the activation of mitogen-activated protein kinase in HCE. These results show that the synergistic effects of SP and IGF-1 on corneal epithelial wound healing were expressed through activation of the integrin, FAK, and paxillin system.