Evidence for a new binding mode to GSK-3: Allosteric regulation by the marine compound palinurin
Glycogen synthase kinase 3Î² (GSK-3Î²) is widely recognised as a relevant player in the pathogenesis of several highly prevalent disorders such as Alzheimer’s disease, mood disorders, diabetes and cancer. Therefore, this enzyme constitutes a highly attractive therapeutic target for the development of selective inhibitors as new promising drugs for the treatment of these pathologies. We describe here the isolation and biochemical characterization of the marine natural sesquiterpene palinurin as a GSK-3Î² inhibitor. Experimental studies performed for characterizing the inhibitory mechanism indicate that GSK-3Î² inhibition by palinurin cannot be competed out by ATP nor peptide substrate. Molecular modelling techniques have enabled us to propose an unconventional binding mode to GSK-3Î². Moreover, molecular dynamics simulations have identified an allosteric mechanism by which binding of palinurin leads to GSK-3Î² inhibition. The inhibitory activities determined for a series of structurally related analogues support the proposed binding mode of palinurin, which is the first compound described to target this allosteric site. The results offer new opportunities for designing and developing selective inhibitors with novel mechanisms of action. â¶ The biochemical characterization of palinurin as a GSK-3Î² inhibitor is reported. â¶ A non-ATP/substrate-competitive mechanism is found for the inhibition of GSK-3Î². â¶ The enzymatic mode of action is justified by the binding to an unconventional site. â¶ Binding to this site provides a basis to explain the selective inhibition of GSK-3.