GSK-3 Signaling Pathway

Glycogen synthase kinase 3 (GSK-3) is a multifunctional serine/threonine kinase found in all eukaryotes. GSK-3 is one of the few signaling mediators that play central roles in a diverse range of signaling pathways, including those activated by Wnt, PI3K, growth factors, cytokines, and ligands for G protein-coupled receptors. The PI3K pathway is known for regulating metabolism, cell growth, and cell survival. The PI3K activity is stimulated by diverse oncogenes and growth factor receptors. PI3K-mediated production of PIP3 leads to the activation of Akt. The activation of Akt leads to the phosphorylation of GSK-3, which is active in resting cells, but is inactivated by the phosphorylation. The GSK-3 has been linked to the regulation of an assembly of transcription factors, including β-catenin, NF-κB, c-Jun, CREB, and STAT. Thus, the altered activity of GSK-3 causes various effects on cytokine expression. 

In the absence of Wnt signaling, β-catenin is phosphorylated by CK1 and GSK-3. This phosphorylation leads to recognition by β-TrCP, leading to the ubiquitylation of β-catenin and degradation by the proteasome. Upon binding of a lipid-modified Wnt protein to the receptor complex, a signaling cascade is initiated. LRP is phosphorylated by CK1/CK2 and GSK-3, and Axin is recruited to the plasma membrane. The kinases in the β-catenin destruction complex are inactivated and β-catenin translocates to the nucleus to form an active transcription factor complex with TCF, leading to transcription of a large set of target genes.

Some endogenous growth factors could bind to and activate the tyrosine kinase receptor. This facilitates the recruitment of other proteins (SHC, SOS), which results in the activation of the ERK-MAPK cascade and the inhibition of GSK-3. GSK-3 exerts many cellular effects: it regulates cytoskeletal proteins, and is important in determining cell survival/cell death. GSK-3 has also been identified as a target for the actions of lithium. GSK-3 can inhibit glycogen synthase, the enzyme that catalyzes the transfer of glucose from UDPG to glycogen^[1][2].

Reference:

[1]. Brenner D, et al. Regulation of tumour necrosis factor signalling: live or let die.Nat Rev Immunol. 2015 Jun;15(6):362-74. 
[2]. Conrad M, et al. Regulated necrosis: disease relevance and therapeutic opportunities.Nat Rev Drug Discov. 2016 May;15(5):348-66.