FIG. 6.

Activation of M-Ras by trophic factors in astrocytes. Primary astrocytes were deprived of serum for 48 h and stimulated with bFGF (A), HGF (B), and EGF (C) for the indicated durations (minutes). Cells were solubilized, and about 1.0 to 1.5 mg of total cell lysates was used in affinity pull-down assays to assess the GTP-bound levels (GTP) of M-Ras (upper panel) and H-Ras (lower panel). The levels of total M-Ras and H-Ras are shown (input). The relative levels of GTP-bound M-Ras at peak (5-min, black bars) verses late (90-min, white bars) phase are quantified (right panels). The data are the means ± standard deviations derived from two to four independent mating experiments.