M-CSF or G-CSF activates the JNK and ERK pathways in Ba/F3 cells. (A) FACS analysis for MCSFR (MR) and GCSFR (GR) in a Ba/F3 subclone transduced with retroviral vectors expressing these receptors. Cells were stained either with anti-MCSFR-PE, biotin-GCSF, and streptavidin-APC (top panel), or separately with biotin-GCSF or biotin-MCSF and streptavidin-PE (bottom panels). (B) Ba/F3(MR,GR) cells were cultured with IL-3 or in its absence (−) for 3 hours (top panel) or 1 hour (bottom panel). Total cellular protein extracts from equal numbers of cells were then subjected to Western blotting for indicated total or phosphorylated proteins (top). (C) Ba/F3(MR,GR) cells removed from IL-3 for 1 hour were cultured for 0 to 120 minutes in M-CSF or G-CSF. Total cellular protein extracts were then subjected to Western blotting for the indicated proteins.