A Common Phosphate Binding Site Explains the Unique Substrate Specificity of GSK3 and Its Inactivation by Phosphorylation

Abstract

The inhibition of GSK3 is required for the stimulation of glycogen and protein synthesis by insulin and the specification of cell fate during development. Here, we demonstrate that the insulin-induced inhibition of GSK3 and its unique substrate specificity are explained by the existence of a phosphate binding site in which Arg-96 is critical. Thus, mutation of Arg-96 abolishes the phosphorylation of "primed" glycogen synthase as well as inhibition by PKB-mediated phosphorylation of Ser-9. Hence, the phosphorylated N terminus acts as a pseudosubstrate, occupying the same phosphate binding site used by primed substrates. Significantly, this mutation does not affect phosphorylation of "nonprimed" substrates in the Wnt-signaling pathway (Axin and beta-catenin), suggesting new approaches to design more selective GSK3 inhibitors for the treatment of diabetes.

6-Br-5methylindirubin-3′oxime (5-Me-6-BIO) targeting the leishmanial glycogen synthase kinase-3 (GSK-3) short form affects cell-cycle progression and induces apoptosis-like death: Exploitation of GSK-3 for treating leishmaniasis

“…The catalytic residues Asp200 hGSK-3β, Glu97 hGSK-3β and Lys85 hGSK-3β interacting with each other and with the phosphates of ATP are also conserved as Asp170 LGSK-3s , Glu61 and Lys49 LGSK-3s . The priming phosphate binding site, responsible for optimizing the orientation of primed substrates (Frame et al, 2001) for phosphorylation to occur, is formed in the leishmanial GSK-3s by Arg60, Arg150 and Lys175.…”

Glycogen synthase kinase-3β gene is associated with antidepressant treatment response in Chinese major depressive disorder

“…Both GSK3A and GSK3B are significantly inhibited by phosphorylation on serine-21 and serine-9, respectively, and the downregulation of their constitutive activity may in turn activate the transcription of their target genes. 2 Impairment of this inhibitory control of GSK3 can result in abnormally high GSK3 activity, which may have detrimental effects on neural plasticity and survival. 1 Among the GSK3 isoforms, GSK3B is highly expressed in neural tissue where its expression is regulated during development.…”

AMP-activated protein kinase (AMPK) activating agents cause dephosphorylation of Akt and glycogen synthase kinase-3

“…Akt is activated by dual phosphorylation on Thr308 and Ser473 which is often a downstream consequence of phosphatidylinositol 3-kinase (PI3K) activated by growth factor receptor signaling cascades or cellular stress [22]. Among the most prevalent targets of Akt are the two isoforms of GSK3 which are inhibited by Aktmediated phosphorylation of an N-terminal serine, serine-9 in GSK3b or serine-21 in GSK3a [23,24]. This coupling of Akt and GSK3 leads to inverse changes in their activities, when Akt is activated by phosphorylation it maintains GSK3 in a serine-phosphorylated inhibited state, and decreases in Akt activity lead to dephosphorylation and activation of GSK3.…”