FIG. 6.

Crkl is essential for Fgf8-induced activation of the cascades of serine/threonine kinases. (A) In vitro kinase assays for Pak, Raf1, and Mek1. Suspension culture of MEFs was stimulated with 10 ng of Fgf8/ml for 10 min, and each protein was immunoprecipitated from cell lysates for in vitro kinase assays. (B) Immunoblot analysis for Fgf8-induced site specific phosphorylation of Pak, Raf1, Mek1, and Erk1/2. Cell lysates were prepared as described above, and phospho-specific antibodies were used to probe phosphorylation events. Total protein levels of each protein are shown in the lower panel for each protein.