SCF induces phosphorylation and down-regulation of Bim protein. (A) BMCMCs were left untreated (–) or treated with SCF (+). Indicated lysates were treated with AP. The SCF-induced mobility shift of Bim was vanished by AP treatment. DMSO indicates dimethyl sulfoxide. (B) [³²P]-orthophosphate–labeled, starved BMC-MCs were left untreated (–) or treated with SCF (+) for 10 minutes. Bim was isolated by immunoprecipitation and separated by SDS–polyacrylamide gel electrophoresis (PAGE). The phosphorylation of Bim was visualized by phosphoimaging. (C) BMCMCs were starved for 24 hours prior to SCF treatment for indicated time periods. Both the levels and duration of phosphorylation and expression of Bim were analyzed by Western blot. Data represent comparable results from 2 to 3 separate experiments.