FIG. 4.

B-KSR1 associates with 14-3-3, MEK, and activated MAPK in vivo. (A) B-KSR1 proteins were immunoprecipitated (IP) from lysates of 293 cells coexpressing activated RasV12 and either full-length B-KSR1 (WT) or the isolated amino-terminal domain (N-Term) or isolated catalytic domain (C-Term) of B-KSR1, using a Pyo antibody. In addition, B-KSR1 was immunoprecipitated from lysates of adult mouse brain and kidney tissues using a KSR1 antibody (αKSR). The immunoprecipitates were then examined by immunoblot analysis using KSR, MEK, P-MAPK, and 14-3-3 antibodies to detect endogenous proteins interacting with B-KSR1. (B) Lysates from specialized brain regions were analyzed as for panel A and examined by immunoblot analysis with KSR, MEK, and P-MAPK antibodies.