Figure 1

PTPMeg2 interacts with STAT3. (A) PTPMeg2 was co-immunoprecipitated with STAT3 in mammalian cells. Lysates prepared from HEK293T cells expressing Flag-STAT3 and Myc-PTPMeg2 were precipitated with an anti-Flag antibody and the precipitants were blotted by an anti-Myc antibody. (B) STAT3 interacts with PTPMeg2 physically in vitro. GST or GST-STAT3 fusion proteins were mixed with the Myc-PTPMeg2 prepared from cells (C) PTPMeg2 preferentially interacts with STAT3. Myc-PTPMeg2 was co-expressed with Flag-tagged STAT3 (S3), STAT1 (S1) or STAT5a (S5a) in 293T cells. (D) PTPMeg2 interacts with STAT3 in vivo. Lysates from the mouse brain tissue and breast cancer MCF7 cells were used in co-immunoprecipitation assays to demonstrate the endogenous protein interaction with an anti-STAT3 antibody (C20) and anti-PTPMeg2 rabbit polyclonal antibody. (E) PTPMeg2 interacts with phosphorylated STAT3. A reciprocal immunoprecipitation assay was performed with an anti-Myc antibody or an anti-Flag antibody for the lysates of HEK293T cells under IL-6 stimulation for 30 min. (F) IL-6 induces the interaction of STAT3 and PTPMeg2 in vivo. An immunoprecipitation assay was performed using the endogenous proteins in MCF7 cells stimulated by IL-6 for 30 min. (G) PTPMeg2 decreases the accumulation of pSTAT3 in the nucleus. MCF7 cells transfected with STAT3 and/or PTPMeg2 WT/CS were treated without or with IL-6 for 30 min. Cells were immunostained with an anti-PTPMeg2 (FITC) and an anti-Flag antibody (TRITC, for Flag-STAT3). DAPI was used for nuclear staining. Scale, 10 μm.