Glycogen synthase kinase 3 (GSK3)

Glycogen synthase kinase 3 (GSK3) is a highly conserved serine/threonine protein kinase found in all eukaryotes. It exists primarily as two closely related isoforms—GSK3α and GSK3β—encoded by separate genes but sharing high sequence identity within their catalytic domains. Originally identified for its role in phosphorylating and inhibiting glycogen synthase to regulate glucose storage, it is now recognized as a multifunctional enzyme involved in numerous cellular pathways including signal transduction from insulin and Wnt receptors, cell cycle progression, apoptosis regulation, cellular transport mechanisms, neurodevelopmental processes, and more. Unlike most kinases that are activated upon stimulation, GSK3 is constitutively active under resting conditions and is regulated mainly through inhibitory phosphorylation events triggered by hormones such as insulin via the PI3K/Akt pathway. Dysregulation or hyperactivity of this enzyme has been implicated in several major diseases including type II diabetes mellitus due to impaired insulin signaling; various cancers through effects on cell proliferation; neurodegenerative disorders like Alzheimer’s disease via abnormal tau phosphorylation; and psychiatric illnesses such as bipolar disorder. Because it sits at the intersection of so many critical biological pathways—and because small-molecule inhibitors can modulate its activity—Glycogen synthase kinase 3 remains an important therapeutic target under investigation across multiple fields including endocrinology, oncology, neurology/psychiatry.

Other names

GSK-3Glycogen synthase kinase-3GSK3α (isoform alpha)GSK3β (isoform beta)

Drugs targeting this molecule typically act by inhibiting its serine/threonine kinase activity. For example, - Competitive inhibition at the ATP-binding site. - Allosteric inhibition via phosphorylation of regulatory residues. Lithium acts as a noncompetitive inhibitor by competing with magnesium ions required for enzyme function.