Structural Characterization of the GSK-3β Active Site Using Selective and Non-selective ATP-mimetic Inhibitors

GSK-3β is a regulatory serine/threonine kinase with a plethora of cellular targets. Consequently, selective small molecule inhibitors of GSK-3β may have a variety of therapeutic uses including the treatment of neurodegenerative diseases, type II diabetes and cancer. In order to characterize the active site of GSK-3β, we determined crystal structures of unphosphorylated GSK-3β in complex with selective and non-selective ATP-mimetic inhibitors. Analysis of the inhibitorsʹ interactions with GSK-3β in the structures reveals how the enzyme can accommodate a number of diverse molecular scaffolds. In addition, a conserved water molecule near Thr138 is identified that can serve a functional role in inhibitor binding. Finally, a comparison of the interactions made by selective and non-selective inhibitors highlights residues on the edge of the ATP binding-site that can be used to obtain inhibitor selectivity. Information gained from these structures provides a promising route for the design of second-generation GSK-3β inhibitors.