FIG. 7.
Induction of β3-integrin by sustained ERK MAP kinase activation. (A to C) NIH 3T3 cells expressing EGFPΔRaf-1:ER were cultured in serum-free medium for 36 h prior to the addition of 10 ng of EGF per ml, 20% (vol/vol) FCS, 1 μM 4-HT, 0.1% (vol/vol) ethanol (EtOH), 50 ng of phorbol esters per ml (PMA), or 10 ng of PDGF per ml for 12 or 24 h. Cell extracts were prepared and probed for the expression of β3-integrin (A), the activation of the ERK MAP kinases (B), and the overall expression of the ERK MAP kinases as a loading control (C) using the appropriate antisera as described in Materials and Methods. (D) NIH 3T3 cells expressing the NGF receptor (65) were either left untreated or treated with 10 ng of NGF per ml for 24 or 48 h, at which time the expression of β3-integrin and p21Cip1 was assessed by Western blotting with the appropriate antisera.