Figure 2

PTPMeg2 enhances dephosphorylation of STAT3. (A) PTPMeg2 decreases the level of pSTAT3. Levels of pSTAT3(Tyr705) were examined in the HEK293T cells transfected with Flag-STAT3 and different forms of PTPMeg2 in the presence or absence of IL-6 (10 ng/ml) for 30 min. (B) PTPMeg2 increases the dephosphorylation of STAT3. HEK293T cells were treated with IL-6 (10 ng/ml) for 30 min, followed by a starvation (shown as withdrawal) for different times. (C) PTPMeg2 promotes the STAT3 dephosphorylation rate. HEK293T cells were treated with IL-6 (10 ng/ml) for 30 min, followed by starvation for different times. The dynamic changes of the pSTAT3 (Tyr705) levels demonstrates the dephosphorylation rate of STAT3. (D) PTPMeg2 mediates STAT3 dephosphorylation in a dose dependent manner. HEK293T cells were transfected with Flag-STAT3 (2 μg/well) and different amounts of PTPMeg2 in a 6 well plate. (E) PTPMeg2 dephosphorylates STAT3 in vitro. Different amounts of purified GST-PTPMeg2 (10, 5 and 2.5 μg/tube) was added to purified pSTAT3 in a PTPase buffer at 37°C for 30 min. pSTAT3 was prepared in HEK293T cells transfected with Flag-STAT3 for 48 h and then stimulated with IL-6 for 30 min. (F) The PTP domain of PTPMeg2 contributes to STAT3 dephosphorylation. Myc-PTP domain, Myc-SEC domain and different deletions of PTPMeg2 were co-transfected with Flag-STAT3 for 48 h before stimulation with 10 ng/ml IL-6 for 30 min.