C2-ceramide stimulates CREB phosphorylation. MC/9 cells treated with the indicated concentrations of SB203580 for 20 minutes were stimulated with C2-ceramide (50 μmol/L) or vehicle alone for 5 minutes. Whole-cell lysates were separated on SDS-PAGE and immunoblot analysis was performed to detect phospho-CREB (A) and reprobed to detect CREB (B).