Sustained and enhanced activation of MAP kinase (ERK) 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 MAP kinase antibody. Bars show the relative phosphorylation of ERK. Data are presented relative to the phosphorylation of ERK by MA-SCF after 60 minutes (with the level at 60 minutes taken as 100). These experiments were performed at least 3 times with similar results.