Sustained activation of MAP kinase (p38) in G1E-ER2 cells by membrane isoforms of SCF.

Factor-starved G1E-ER2 cells were cocultured with mitomycin C–treated stromal cells expressing S-SCF, MA-SCF, or MR-SCF for indicated time points. Subsequently, at various times, cell lysates were collected and subjected to Western blot analysis with a rabbit anti–phospho p38 MAP kinase antibody. Bars demonstrate the relative phosphorylation of p38. Data are presented relative to the phosphorylation of p38 by SCF-MA after 10 minutes (with the level at 10 minutes taken as 100). These experiments were performed 2 times with similar results.