MAPKAPK-2-mediated LIM-kinase activation is critical for VEGF-induced actin remodeling and cell migration

Vascular endothelial growth factor- A ( VEGF- A) induces actin reorganization and migration of endothelial cells through a p38 mitogen- activated protein kinase ( MAPK) pathway. LIM- kinase 1 ( LIMK1) induces actin remodeling by phosphorylating and inactivating cofilin, an actin-depolymerizing factor. In this study, we demonstrate that activation of LIMK1 by MAPKAPK- 2 ( MK2; a downstream kinase of p38 MAPK) represents a novel signaling pathway in VEGF- A- induced cell migration. VEGF- A induced LIMK1 activation and cofilin phosphorylation, and this was inhibited by the p38 MAPK inhibitor SB203580. Although p38 phosphorylated LIMK1 at Ser- 310, it failed to activate LIMK1 directly; however, MK2 activated LIMK1 by phosphorylation at Ser- 323. Expression of a Ser- 323-non- phosphorylatable mutant of LIMK1 suppressed VEGF-A-induced stress fiber formation and cell migration; however, expression of a Ser- 323- phosphorylation- mimic mutant enhanced these processes. Knockdown of MK2 by siRNA suppressed VEGF- A- induced LIMK1 activation, stress fiber formation, and cell migration. Expression of kinase- dead LIMK1 suppressed VEGF- A- induced tubule formation. These findings suggest that MK2- mediated LIMK1 phosphorylation/ activation plays an essential role in VEGF- A- induced actin reorganization, migration, and tubule formation of endothelial cells.