Interaction between ERK and GSK3β mediates basic fibroblast growth factor-induced apoptosis in SK-N-MC neuroblastoma cells

The Ewing's sarcoma family of tumors ( ESFT) includes Ewing's sarcoma ( ES), Askin's tumor of the chest wall, and peripheral primitive neuroectodermal tumor. Basic fibroblast growth factor ( FGF2) suppresses the growth of ESFT cells and causes their apoptosis. The underlying mechanism is unclear. Using a human peripheral primitive neuroectodermal tumor cell line, SK-N-MC, we demonstrated FGF2 stimulated phosphorylation of ERK1 and ERK2 ( pERK1/2) and GSK3 beta ( pGSK3 beta( Tyr-216)), all of which were primarily retained in the cytoplasm. FGF2 promoted the association between ERK and pGSK3 beta( Tyr-216). Inhibitors for GSK3 beta( TDZD and LiCl) and ERK ( PD98059) protected cells from FGF2-induced apoptosis. On the other hand, inhibitors of GSK3 beta, but not PD98059 decreased ERK/pGSK3 beta( Tyr-216) association and caused a nuclear translocation of pERK1/2. Similarly, expression of a kinase-deficient ( K85R) GSK3 beta or GSK3 beta-small interfering RNA inhibited FGF2-regulated ERK/pGSK3 beta( Tyr-216) association and translocated pERK to the nucleus. Both K85R GSK3 beta and small interfering RNA offered protection against FGF2-induced cell death. In contrast, overexpression of wild-type GSK3 beta sensitized cells to FGF2 cytotoxicity. Hydrogen peroxide and ethanol enhanced FGF2-stimulated pGSK3 beta( Tyr-216), ERK/pGSK3 beta( Tyr-216) association, and cytoplasmic retention of pERK1/2. As a result, they potentiated FGF2-induced cell death. Taken together, our results suggested that FGF2-induced accumulation of pERK1/ 2 in the cytoplasm is toxic for SK-N-MC cells. The formation of an ERK center dot GSK3 beta complex retained pERK1/ 2 in the cytoplasm. In contrast, disruption of the ERK center dot GSK3 beta complex resulted in nuclear translocation of pERK1/ 2 and offered protection.