FIG. 7.

Distinct KSR1 concentrations promote the proliferative and adipogenic potential of cells. (A) Growth factor-induced ERK activation (closed squares), cell proliferation (gray triangles), and adipogenic response (open diamonds) were plotted as a percent response versus KSR1 expression level. (B) Relationship between KSR1 level, ERK activation, and adipogenic progression. Deletion of KSR1 blocks early steps in adipogenesis by blocking MDI-stimulated ERK activation. Low levels of KSR1 expression (1-4X) promote ERK- and RSK-mediated C/EBPβ phosphorylation, promoting adipogenesis. Higher levels of KSR1 expression (5-14X) inhibit adipogenic progression by ERK-mediated phosphorylation of PPARγ.