Involvement of Caveolin-1 in Fibronectin-Induced Mouse Embryonic Stem Cell Proliferation: Role of FAK, RhoA, PI3K/Akt, and ERK 1/2 Pathways

Fibronectin (FN) is the foremost proliferation-associated extracellular matrix component promoting cell adhesion, migration, and survival. We examined the effect of FN on cell proliferation and the related signaling pathways in mouse embryonic stem (ES) cells. FN increased integrin beta 1, Src, focal adhesion kinase (FAK), and caveolin-1 phosphorylation levels in a time-dependent manner. Phosphorylation of Src, FAK, and caveolin-1 was attenuated by integrin beta 1 neutralizing antibody. Integrin beta 1, Src, and FAK coimmunoprecipitated with caveolin-1 in the presence of FN. In addition, FN increased RhoA and Rho kinase activation, which were completely blocked by PP2, FAK small interfering RNA (siRNA), caveolin-1 siRNA, or the caveolar disruptor methyl-beta-cyclodextrin (M beta CD). FN also increased phosphorylation of Akt and ERK 1/2, which were significantly blocked by either FAK siRNA, caveolin-1 siRNA, M beta CD, GGTI-286 (RhoA inhibitor), or Y-27632 (Rho kinase inhibitor). FN-induced increase of protooncogenes (c-fos, c-myc, and c-Jun) and cell-cycle regulatory proteins (cyclin D1/CDK4 and cyclin E/CDK2) expression levels were attenuated by FAK siRNA or caveolin-1 siRNA. Furthermore, inhibition of each pathway such as integrin beta 1, Src, FAK, caveolin-1, RhoA, Akt, and ERK 1/2 blocked FN-induced [H-3]-thymidine incorporation. We conclude that FN stimulates mouse ES cell proliferation via RhoA-PI3K/Akt-ERK 1/2 pathway through caveolin-1 phosphorylation. J. Cell. Physiol. 226: 267-275, 2010. (C) 2010 Wiley-Liss, Inc.