Figure 3.

Activities of MAPK upon growth factor withdrawal. IL-3 was removed from cultures (2 × 10⁶ cells) of wt- and btk null-BMMCs for the indicated intervals. Cells were lysed and immunoprecipitated with anti-JNK1, anti-p38, or anti-ERK1. Immune complex kinase assays were done, and reaction products were analyzed by SDS/PAGE and autoradiography. -Fold activities measured by densitometry of the substrate bands are shown after normalized to that of wt cells before starvation. Positions of substrates, GST-c-Jun(1–79) and MBP, are indicated.