Glycogen Synthase Kinase 3β-Mediated Apoptosis of Primary Cortical Astrocytes Involves Inhibition of Nuclear Factor κB Signaling

Abstract

Recent studies have revealed a positive correlation between astrocyte apoptosis and rapid disease progression in persons with neurodegenerative diseases. Glycogen synthase kinase 3β (GSK-3β) is a molecular regulator of cell fate in the central nervous system and a target of the phosphatidylinositol 3-kinase (PI-3K) pathway. We have therefore examined the role of the PI-3K pathway, and of GSK-3β, in regulating astrocyte survival. Our studies indicate that inhibition of PI-3K leads to apoptosis in primary cortical astrocytes. Furthermore, overexpression of a constitutively active GSK-3β mutant (S9A) is sufficient to cause astrocyte apoptosis, whereas an enzymatically inactive GSK-3β mutant (K85M) has no effect. In light of reports on the interplay between GSK-3β and nuclear factor κB (NF-κB), and because of the antiapoptotic activity of NF-κB, we examined the effect of GSK-3β overexpression on NF-κB activation. These experiments revealed strong inhibition of NF-κB activation in astrocytes upon overexpression of the S9A, but not the K85M, mutant of GSK-3β. This was accompanied by stabilization of the NF-κB-inhibitory protein, IκBα and down-regulation of IκB kinase (IKK) activity. These findings therefore implicate GSK-3β as a regulator of NF-κB activation in astrocytes and suggest that the pro-apoptotic effects of GSK-3β may be mediated at least in part through the inhibition of NF-κB pathway.

ACKNOWLEDGMENTS

We thank Stephen Dewhurst and Harris Gelbard for guidance and for comments on the manuscript. We thank Morris Birnbaum, Trevor C. Dale, Shao-Cong Sun, and Edward Schwarz for generously providing us reagents.

This work was supported by NIH grants to J.F.S. and H. Gelbard (RO1 MH56838, PO1 MH64570), L.F.S. and S. Dewhurst (R01 NS40315), and A.L.W. and S.B.M. (RO1 NS39039; PO1 MH64570).

J.F.S., L.F.S., and A.L.W. contributed equally to this work.