Maspin regulates endothelial cell adhesion and migration through an integrin signaling pathway

Maspin has been identified as a potent angiogenesis inhibitor. However, the molecular mechanism responsible for its anti-angiogenic property is unclear. In this study, we examined the effect of maspin on endothelial cell (EC) adhesion and migration in a cell culture system. We found that maspin was expressed in blood vessels ECs and human umbilical vein endothelial cells (HUVECs). Maspin significantly enhanced HUVEC cell adhesion to various matrix proteins. This effect was dependent on the activation of integrin β₁, which subsequently led to distribution pattern changes of vinculin and F-actin. These results indicated that maspin affects cell adhesion and cytoskeleton reorganization through an integrin signal transduction pathway. Analysis of HUVECs following maspin treatment revealed increased integrin-linked kinase activities and phosphorylated FAK levels, consistent with increased cell adhesion. Interestingly, when HUVECs were induced to migrate by migration stimulatory factor bFGF, active Rac1 and cdc42 small GTPase levels were decreased dramatically at 30 min following maspin treatment. Using phosphorylated FAK at Tyr³⁹⁷ as an indicator of focal adhesion disassembly, maspin-treated HUVECs had elevated FAK phosphorylation compared with the mock treated control. The results were a reduction in focal adhesion disassembly and the retardation in EC migration. This study uncovers a mechanism by which maspin exerts its effect on EC adhesion and migration through an integrin signal transduction pathway.