Fig. 6. Impaired ERK signaling in ζPKC–/– B cells. B cells from wild-type or ζPKC–/– mice were stimulated with 20 µg/ml IgM (A and B) for different times or with different concentrations of IgM for 10 min (C and D), after which cell extracts were analyzed by immunoblotting with anti-phospho-ERK and anti-ERK (A), anti-phospho-MEK and anti-MEK (C), or anti-phospho-aPKC and anti-ζPKC and anti-λ/ιPKC (D) antibodies. Cell extracts were also immunoprecipitated with an anti-phospho-p38 antibody, and the enzymatic activity of the immunoprecipitated enzyme was determined as phosphorylation of its substrate ATF-2 with the corresponding anti-phospho-ATF-2 antibody, and the loading control was performed with an anti-p38 antibody (B). These are representative experiments of at least another three with similar results.