The Small GTPase Ras Is Involved in Growth Factor-Regulated Expression of the I-1 Integrin Subunit in PC12 Cells

PC12 cells interact with several growth factors (e. g.EGF, FGF, and NGF) via specific tyrosine receptor kinases,resulting in cell proliferation or neuronal differentiation.The small GTPase Ras is known to be involvedin downstream signaling of these growthfactor receptors. Furthermore, cellmatrix interactionsmediated by integrins, as well as integrininducedsignaling, are also involved in growth factorstimulatedsignal transduction in PC12 cells.In this study we determined the expression of theI-1 integrin subunit in response to EGF and NGF inPC12 wildtype (wt) cells, and in PC12 cells overexpressingan inactive HRas protein (RasN17).In PC12 wt cells, I-1 integrin expression is upregulatedby EGF and NGF. Cell surface expression ofI-1I21 integrin is also enhanced in growth factortreatedcells. This upregulation leads to increased I-1I21-specific adhesion to collagen. In cells expressing thedominantnegative RasN17 variant, I-1 integrin expressionand I-1I21-specific adhesion remain unchangedin response to both growth factors.