Glycogen synthase kinase 3-alpha is a multifunctional protein serine kinase. GSK-3 phosphorylates and inactivates glycogen synthase. It has also been implicated in the regulation of cell fate in Dictyostelium and is a component of the Wnt signaling pathway required for Drosophila，Xenopus，and mammalian development. GSK-3 has been shown to regulate Cyclin D1 proteolysis and subcellular localization. GSK-3alpha (GSK-3) regulates the production of amyloid-beta peptides，a major component of the plaques that accumulate with progression of Alzheimer's disease，by phosphorylating Tau proteins. This presents the possibility that defects in GSK-3 signaling can contribute to the onset of Alzheimer’s disease. GSK-3 can be phosphorylated by Akt at Ser21. This phosphorylation of GSK-3 negatively regulates its kinase activity.
