GSK3B

Glycogen synthase kinase 3 beta, also known as GSK3B, is an enzyme that in humans is encoded by the GSK3B gene. In mice, the enzyme is encoded by the GSK-3β gene. Abnormal regulation and expression of GSK3β is associated with an increased susceptibility towards bipolar disorder.

Function

Glycogen synthase kinase-3 (GSK-3) is a proline-directed serine-threonine kinase that was initially identified as a phosphorylating and an inactivating agent of glycogen synthase. Two isoforms, alpha (GSK3A) and beta, show a high degree of amino acid homology. GSK3B is involved in energy metabolism, neuronal cell development, and body pattern formation.

Loss of function mutations

Homozygous disruption of the GSK-3β locus in mice results in embryonic lethality during mid-gestation. This lethality phenotype could be rescued by inhibition of tumor necrosis factor.

Interactions

GSK3B has been shown to interact with:

GSK-3

Glycogen synthase kinase 3 is a serine/threonine protein kinase that mediates the addition of phosphate molecules onto serine and threonine amino acid residues. First discovered in 1980 as a regulatory kinase for its namesake, Glycogen synthase, GSK-3 has since been identified as a kinase for over forty different proteins in a variety of different pathways. In mammals GSK-3 is encoded by two known genes, GSK-3 alpha (GSK3A) and GSK-3 beta (GSK3B). GSK-3 has recently been the subject of much research because it has been implicated in a number of diseases, including Type II diabetes (Diabetes mellitus type 2), Alzheimer's Disease, inflammation, cancer, and bipolar disorder.

Mechanism

GSK-3 functions by phosphorylating a serine or threonine residue on its target substrate. A positively charged pocket adjacent to the active site binds a "priming" phosphate group attached to a serine or threonine four residues C-terminal of the target phosphorylation site. The active site, at residues 181, 200, 97, and 85, binds the terminal phosphate of ATP and transfers it to the target location on the substrate (see figure 1).