Fig. 5. ERK2 dissociates from the LSP1 complex after anti-IgM stimulation. (A) Anti-MEK1 and anti-ERK2 immunoprecipitates from W10 cells (unstimulated or stimulated for 20 minutes with 50 µg/ml anti-IgM) were analyzed for the presence of LSP1. No antibodies were added to control assays using unstimulated cells (cntrl). Equal recovery of MEK1 or ERK2 in unstimulated and stimulated samples was confirmed by western blot analysis using anti-MEK1 (B) or anti-ERK2 (C) antibodies. (D) Anti-LSP1 immunoprecipitates from unstimulated or anti-IgM-stimulated cells were analyzed for the presence of ERK2 without (lanes1-3) or with pretreatment of the cells with 10 µM U0126 (lanes 4-6). Recovery of LSP1 was determined by western blotting of parallel samples using anti-LSP1 (E).