FIGURE 6.

PTPα negatively regulates Ras, Rho GTPases, MAPK, and Akt and is required for p27 accumulation in CG4 cells. A and B, control siRNA or PTPα siRNA treated cells were stimulated with CG4 proliferation medium for 3 h. The amount of Ras, Rac1/Cdc42, and Rho in the pull-down assay as well as in the WCL was determined by immunoblotting with anti-Ras, anti-Rac1, anti-Cdc42, and ant-Rho antibodies, respectively. The numbers at the bottom show the relative amounts of GTP-bound protein normalized to the amount of that protein in the lysate as calculated after densitometric quantification. C, control siRNA or PTPα siRNA-treated cells were stimulated with CG4 proliferation medium for 3 h or 24 h. Phosphorylation of ERK1/2 at T202/Y204, Akt at S473 and JNK1/2/3 at T183/Y185 at 3 h was determined by immunoblotting with anti-ERK1/2 phospho-T202/Y204, anti-Akt phospho-S473, and anti-JNK1/2/3 phospho-T183/Y185 antibodies, respectively. D, control siRNA or PTPα siRNA-treated cells were stimulated with CG4 proliferation medium for 3 h or 24 h. PTPα and p27 expression was determined by immunoblotting with anti-PTPα, anti-p27 and anti-actin antibodies. The numbers at the bottom show the relative band intensities of p27 after normalization to the actin signal.