Figure 1.

Inhibition of TC-PTP activity is observed in cells but not in in vitro phosphatase assays.A, Western blot analysis of phospho-STAT1 in H358 cells overexpressing TC45, TC45^E/A, and TC35 stimulated with or without IFN-γ for 1 h. The blots are representative of three independent experiments. B, quantification of mean fluorescence intensity of pY⁷⁰¹-STAT1 from Phospho-STAT1 flow cytometry assays. Cells are transfected with mEGFP-TC45 vectors. C, representative calculation of kinetic parameters from absorbance versus time data. Cyan: fitted curve; •: experimental data; data shown are in 60 s intervals. D, graph depicts kinetic curves of TC45 (blue), TC45^E/A (red), and TC35 (green). Data are from three independent replicates. E, top, summary of kinetic parameters determined as in C. Data are the mean of three independent measurements. Mean ± SD. Bottom, bar graphs showing K_m and k_cat as mean ± SD for TC45, TC45^E/A, and TC35 (ordinary ANOVA; ns). IFN-γ, interferon gamma; mEGFP, monomeric enhanced GFP; ns, not significant; STAT, signal transducer and activator of transcription; TC-PTP, T-cell protein tyrosine phosphatase.