MECHANISMS OF SIGNAL TRANSDUCTION
Glycogen Synthase Kinase-3β Facilitates Staurosporine- and Heat Shock-induced Apoptosis: PROTECTION BY LITHIUM*

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The potential role of glycogen synthase kinase-3β in modulating apoptosis was examined in human SH-SY5Y neuroblastoma cells. Staurosporine treatment caused time- and concentration-dependent increases in the activities of caspase-3 and caspase-9 but not caspase-1, increased proteolysis of poly(ADP-ribose) polymerase, and induced morphological changes consistent with apoptosis. Overexpression of glycogen synthase kinase-3β to levels 3.5 times that in control cells did not alter basal indices of apoptosis but potentiated staurosporine-induced activation of caspase-3, caspase-9, proteolysis of poly(ADP-ribose) polymerase, and morphological changes indicative of apoptosis. Inhibition of glycogen synthase kinase-3β by lithium attenuated the enhanced staurosporine-induced activation of caspase-3 in cells overexpressing glycogen synthase kinase-3β. In cells subjected to heat shock, caspase-3 activity was more than three times greater in glycogen synthase kinase-3β-transfected than control cells, and this potentiated response was inhibited by lithium treatment. Thus, glycogen synthase kinase-3β facilitated apoptosis induced by two experimental paradigms. These findings indicate that glycogen synthase kinase-3β may contribute to pro-apoptotic-signaling activity, that inhibition of glycogen synthase kinase-3β can contribute to anti-apoptotic-signaling mechanisms, and that the neuroprotective actions of lithium may be due in part to its inhibitory modulation of glycogen synthase kinase-3β.

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This work was supported by National Institute of Health Grants MH38752, AG06569, and NS10795.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.