Figure 2. Effect of Csk^AS on Lck activity.

(A) Jurkat T cells expressing empty vector, cytoplasmic- or membrane-Csk^AS were serum-starved, pretreated with DMSO or 3-IB-PP1 for 25 minutes, then lysates were prepared directly or following TCR stimulation. Data are representative of three independent experiments. (B) Vector or Csk^AS cells were serum-starved, then pretreated with DMSO or 3-IB-PP1 for 20 minutes. Cells were then stimulated with anti-TCR or vehicle for 2 min prior to fixation and staining for ζ-chain phosphorylation. Histograms show ζ-chain phosphorylation in live, transfected cells. (C) Bar graphs of (B), representing the mean fluorescence intensity (MFI) of phospho-ζ-chain in GFP⁺ transfected cells. (D) Control or membrane-Csk^AS cells were serum-starved and fixed directly or following anti-TCR stimulation or 3-IB-PP1 treatment. Data represent the MFI of phospho-ζ-chain in GFP⁺ transfected cells. Data are representative of at least three independent experiments.