Fig. 10. CD-induced ERK1/2 activity is dependent on a src-like tyrosine kinase. Quiescent R22 cells were preincubated with the indicated inhibitors prior to a 2 hour treatment with CD (10 µM final concentration); control cultures were maintained without additives. Serum-stimulation (FBS to a final concentration of 20%) provided a positive control for ERK activation. The MAPK assay used myelin basic protein (MBP) as the phosphorylation substrate (pMBP; upper panel). Western blot probed with pan-ERK antibodies (middle panel) and Ponceau S staining of MBP (bottom panel) served to confirm equivalent protein loading as well as to confirm normalization of MBP phosphorylation (mean±s.d.) in replicate experiments (histogram).