FIG. 6.

Suppression of TCPTP expression in PTP1B^−/− cells prolongs PI3K/Akt but not MAPK signaling. PTP1B^−/− cells were transfected with TCPTP-specific siRNA1 (A and C), siRNA2m (B), or luciferase control siRNA (Co). At 24 h posttransfection, cells were serum starved and stimulated with 10 nM insulin (INS) as indicated. Cells were lysed in NP-40 buffer and clarified by centrifugation, and proteins were resolved by SDS-PAGE and immunoblotted with the indicated antibodies. In panels A and C the immunoblots are representative of at least three independent experiments. (B) Phosphorylated Akt (Phos-Akt) immunoblots from siRNA2m versus control-transfected cells were quantitated by densitometric analysis and normalized for total Akt protein in the corresponding Akt immunoblots, with the Phos-Akt/Akt ratio in the absence of insulin being set at zero. Units shown are arbitrary and are the means ± standard errors of four independent experiments.