Regulation Of Localized Rac Activation In Leading Edge Of Directed Migrating Cells

Rac activation is strongly regulated spacially and temporally in migrating cells,leading to the formation of specific cell protrusion-lamellipodia in leading edge of the cells and generating the pushing force to put the cells forward, but the molecular mechanism of positive regulation of localized Rac activation remains unclear.This project proposes that the phosphorylation of the intracellular a4 integrin inhibits the interaction of a4 with paxillin, thus the signaling pathway paxillin-GIT1-PIX-PAK would be formed, leading to localized Rac activation in leading edge of the migrating cells.In the paper, western blotting clearly showed that the interactions accurately exist between the cytoskeleton proteins GIT1 and paxillin or PIX respectively. Fluorescent colocalization confirmed that the interactions between GIT1 and paxillin or PIX occur in the leading edge of the cells. Rac activation assay elucidated that Rac is in activated state (GTP-bound) under the stimulation of ECM fibronectin, suggesting that the signaling pathway paxillin-GIT1-PIX-PAK led to Rac activation. The results built the experimental basis for the study of regulation mechanism on localized Rac activation in leading edge of directed migrating cells.