FIG. 5.

Physiologic levels of KSR1 promote adipogenesis. (A) KSR1^−/− MEFs expressing increasing levels of KSR1 were serum starved for 4 hours and stimulated with PDGF (25 ng/ml) for 5 min. ERK phosphorylation was assessed by in situ Western blotting as described in Materials and Methods. Data are the means of four independent experiments. (B) Oil Red O staining and Western blot analysis of KSR1^−/− MEFs expressing increasing levels of KSR1 8 days following treatment with differentiation medium to induce adipogenesis as described in Materials and Methods. Whole-cell lysates were probed at 0 and 8 days following induction with differentiation medium with the indicated antibodies. KSR1 level compared to KSR1^+/+ MEFs is indicated. (C) Analysis of MCE in KSR1^−/− MEFs expressing increasing levels of KSR1 by counting cell numbers 0 and 3 days after treatment with differentiation medium. Values are the means of four independent experiments. (D) Oil Red O staining and Western blot analysis of clonal cell populations isolated from the pool of KSR1^−/− MEFs averaging three times the KSR1 levels shown in B. Whole-cell lysates were probed with the indicated antibodies at 0 and 8 days following induction with differentiation medium with the indicated antibodies. KSR1 level compared to KSR1^+/+ MEFs is indicated.