Synergistic activation of ERK1/2 and p90RSK by SDF-1α in combination with other cytokines.

MO7e cells were incubated for the indicated time periods with SDF-1α (100 ng/mL), GM-CSF (10 ng/mL; GM), SLF (50 ng/mL), or TPO (50 ng/mL) each alone, or with the combination of SDF-1α plus one of these cytokines. Cell lysates were analyzed by Western blotting with phosphospecific antibodies to ERK1/2 (Thr202/Tyr204) or p90RSK (Ser381). The amount of p90RSK is shown as a loading control in the bottom panels. (A) SDF-1α plus GM-CSF. (B) SDF-1α plus SLF. (C) SDF-1α plus TPO. (D,E) Columns represent relative band intensities of phospho-ERK (D) and phospho-RSK (E) ± SD from 3 experiments. *P < .05 (greater than additive).