The small GTPase Ras is involved in growth factor-regulated expression of the alpha 1 integrin subunit in PC12 cells

PC12 cells interact with several growth factors (e. g. EGF, FGF, and NGF) v ia specific tyrosine receptor kinases, resulting in cell proliferation or n euronal differentiation. The small GTPase Ras is known to be involved in do wnstream signaling of these growth factor receptors. Furthermore, cell-matr ix interactions mediated by integrins, as well as integrin-induced signalin g, are also involved in growth factor-stimulated signal transduction in PC1 2 cells. In this study we determined the expression of the alpha1 integrin subunit i n response to EGF and NGF in PC12 wild-type (wt) cells, and in PC12 cells o verexpressing an inactive H-Ras protein (RasN17). In PC12 wt cells, alpha1 integrin expression is upregulated by EGF and NGF. Cell surface expression of alpha1 beta1 integrin is also enhanced in growt h factor-treated cells. This upregulation leads to increased alpha1 beta1 s pecific adhesion to collagen. In cells expressing the dominant-negative Ras N17 variant, alpha1 integrin expression and alpha1 beta1-specific adhesion remain unchanged in response to both growth factors.