Fig 2.

14-3-3ζ binds more efficiently to serine/threonine-phosphorylated Btk. (A) Namalwa cells at steady state, starved or activated using anti-IgM (20 μg/ml) for 15 min. Btk phosphorylated on S51/T495 was immunoprecipitated from Namalwa cell extracts with an anti- RXRXXpT/S antibody, and the precipitated proteins were detected with an antibody against Btk. (B) The 14-3-3 proteins in Namalwa cells were immunoprecipitated with the anti-pan-14-3-3 antibody and probed for the presence of the phosphorylated S51/T495 by immunoblotting with anti- RXRXXpT/S . Btk was detected by immunoblotting with anti-Btk antibody. Quantitative analysis of the bands indicated by the arrowheads was performed by densitometry analysis using Image J software. The bars represent the means and standard errors (SE) of two independent experiments. **, P < 0.004.