Glycogensynthasekinase-3 (GSK-3) is expressed in all tissues and is a member of the protein kinase family, a group of enzymes that catalyze the transfer of a phosphate group from adenosine triphosphate (ATP) to target substrates. GSK-3 is a ser- ine/threonine kinase, and thus transfers a phosphate group to either the serine or threonine residues of its substrates. The mechanism of phosphorylation regulates various complex biological processes, in- cluding metabolism (glucose regulation),[2-6] cell signaling,[7-9] cellular transport,[10-12] apoptosis,[13-15] proliferation, and intracellular communication. Additional roles for GSK-3 in biological processes are likely to be identified in the future. Phosphorylation is a key regulatory step that initiates, enhances, or inhibits the function of a target substrate. Given the breadth of processes asso- ciated with GSK-3, it is not surprising that GSK-3 has emerged as an important target for drug development and medical imaging in various diseases.
both GP and GS, inactivating the former and activating the latter (Dent et al., 1990; Roach, 1990). Insulin signalling also activates GS via another mechanism: the phosphorylation and inactivation of glycogensynthasekinase-3 (GSK-3), a protein kinase that, when active, phosphorylates and inactivates GS (Sutherland et al., 1993; Summers et al., 1999). When GSK-3 is phosphorylated and inactivated, GS can be dephosphorylated and activated, allowing glycogenesis to occur. In addition to its role in glycogen metabolism, GSK-3 has been shown to be a master kinase and is recognized to have roles in: (i) the Wnt signalling pathway, known to regulate several physiological processes as well as development, embryogenesis and cancer (Ding and Dale, 2002); (ii) protein synthesis (Welsh and Proud, 1993); (iii) the response to DNA damage (Watcharasit et al., 2002); (iv) the immune response (Beals et al., 1997); and (v) regulation of Tau protein in neurodegenerative disease (Medina et al., 2011), among others.
Glycogensynthasekinase 3 (GSK-3) is a ser- ine/tyrosine kinase identified in skeletal muscle. To date, two isoforms of GSK-3 have been reported: the first, 51 kDa (GSK-3α), and the second, 47 kDa (GSK-3β). The activity of GSK-3 can be inhibited by Akt-mediated phosphorylation at Ser21 in GSK-3α and at Ser9 in GSK-3β. The aberrant expression of GSK-3β has been demonstrated in metabolic dis- orders and in hematopoietic stem cell differenti- ation and proliferation . Several studies have been performed by means of cell culture and im- munohistochemistry and have shown that GSK-3β is found significantly accumulated in the nuclei of cells in patients with ALL. Furthermore, selective inhibition of GSK-3β induces cell death mediated by downregulation of the transcriptional activity of hematopoietic nuclear factor kappa-light-chain-en- hancer of activated B cells (NFKB). Thus, GSK-3β inhibitors significantly decreased NFKB expression, generating gene suppression and stimulating apop- tosis in vitro, which suggested its being a novel, in- teresting target in ALL treatment . Even more
Chlamydomonas reinhardtii controls flagellar assembly such that flagella are of an equal and predetermined length. Previous studies demonstrated that lithium, an inhibitor of glycogensynthasekinase 3 (GSK3), induced flagellar elongation, suggesting that a lithium-sensitive signal transduction pathway regulated flagel- lar length (S. Nakamura, H. Takino, and M. K. Kojima, Cell Struct. Funct. 12:369-374, 1987). Here, we demonstrate that lithium treatment depletes the pool of flagellar proteins from the cell body and that the heterotrimeric kinesin Fla10p accumulates in flagella. We identify GSK3 in Chlamydomonas and demonstrate that its kinase activity is inhibited by lithium in vitro. The tyrosine-phosphorylated, active form of GSK3 was enriched in flagella and GSK3 associated with the axoneme in a phosphorylation-dependent manner. The level of active GSK3 correlated with flagellar length; early during flagellar regeneration, active GSK3 increased over basal levels. This increase in active GSK3 was rapidly lost within 30 min of regeneration as the level of active GSK3 decreased relative to the predeflagellation level. Taken together, these results suggest a possible role for GSK3 in regulating the assembly and length of flagella.
Accumulated evidence has suggested that potentiation of cortical GABAergic inhibitory neurotransmission may be a key mechanism in the treatment of schizophrenia. However, the downstream molecular mechanisms related to GABA potentiation remain unexplored. Recent studies have suggested that dopamine D2 receptor antagonists, which are used in the clinical treatment of schizophrenia, modulate protein kinase B (Akt)/glycogensynthasekinase (GSK)-3 signaling. Here we report that activation of GABA B receptors significantly inhibits Akt/GSK-3 signaling in a
Cultured hippocampal neurons exposed to NMDA show a rapid and nearly complete dephosphorylation of phospho-Ser9-GSK-3β, indicating that NMDA receptor signaling activated glycogensynthasekinase-3β (GSK-3β) [7, 8]. In vivo blockage of NMDA receptors by administration of the antagonist increased mouse brain serine-phosphorylation [9, 8]. GSK-3β is a serine/threonine kinase that regulates numerous signaling pathways involved in cell cycle control and cell proliferation, differentiation and apoptosis [10, 11]. It is known to play a proapoptotic role in neurons and other tissues [12-14].
GlycogenSynthaseKinase-3 (GSK-3) is a constitutively active, ubiquitously expressed kinase that acts as a critical regulator of many signaling pathways. These pathways, when dysregulated, have been implicated in many human diseases, including bipolar disorder (BD), cancer, and diabetes. Over 100 putative GSK-3 substrates have been reported, based on direct kinase assays or genetic and pharmacological manipulation of GSK-3, in diverse cell types. Many more have been predicted based upon on the prevalence of the GSK-3 consensus sequence. As a result, there remains an unclear picture of the complete GSK-3 phosphoproteome. We have therefore used a large-scale mass spectrometry approach to analyze global changes in phosphorylation and describe the repertoire of GSK-3 substrates in a single cell type. For our studies, we used stable isotope labeling of amino acids in culture (SILAC) to compare the phosphoproteome of wild-type mouse embryonic stem cells (ESCs) to ESCs completely lacking Gsk3a and Gsk3b expression (Gsk3 DKO). We used titanium oxide chromatography to enrich for phosphorylated peptides. From our analysis, we selected 65 phosphoproteins that exhibited significantly reduced phosphorylation in Gsk3 DKO ESCs as high-confidence candidate
Diabetes mellitus (DM) is a metabolic disorder resulting from a defect in insulin secretion, insulin action, or both. GSK3 was discovered over 20 years ago as one of several protein kinases that phosphorylated and inactivated glycogensynthase, the final enzyme in glycogen biosynthesis. Three isoforms of GSK-3 have been identified in mammalian cells, GSK-3α, GSK- 3β, and GSK 3β2 (a splicing variant of GSK-3β). The β isoforms show a substantial deviation in protein sequence, mostly outside the kinase core (308 residues), but the core has 97% sequence similarity and overall 91% identity. Glycogensynthasekinase (GSK-3β) is a serine/threonine kinase that phosphorylates glycogensynthase and inhibits its activity. Thus, inhibition of GSK-3β is expected to activate glycogensynthase and promote glucose uptake into muscle in that way it decreases the blood glucose level. 1
Glycogensynthasekinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine kinase. It was originally identified as key regulatory kinase that phosphorylates and inhibits glycogensynthase downstream of insulin signaling (Embi et al., 1980). However, it has since been shown to play far broader roles in many cellular processes (Cohen and Frame, 2001; Doble and Woodgett, 2003). There are two mammalian GSK-3 isoforms encoded by distinct genes: GSK-3α and GSK-3β. The two proteins share 97% sequence similarity within their kinase catalytic domains, but differ significantly from one another outside this region (Woodgett, 1990).
invariant APE motif. Mutation of K220 to alanine or methionine has shown that K220 is essential for ILK function in vitro and in vivo. Specifically, K220 of ILK has been shown to be essential for kidney development and function , in enhancing adhesion and focal adhesions during bacterial colonization of epithelial cells , and in cardiac function [13,43]. Although the effect of the ‘‘knock-in’’ K220M mutation of ILK on renal development and function was attributed to an adaptor role of ILK in impaired parvin interaction , it is equally likely that it is due to impaired kinase activity. Indeed, the crystal structure of the ILK kinase domain in complex with a-parvin indicates that the K220 ATP- binding motif is well separated from the a-parvin-contacting residues, M402 and K403 in the G helix, and parvin does not have a direct effect on ATP binding , making it unlikely that the major developmental effect of mutating K220 is solely through a- parvin binding.
GSK-3 β inhibitors may inhibit cell proliferation through modulating cyclin-dependent kinases (CDKs). CDKs bind to cyclins, forming complexes that have protein kinase activ- ity, promoting cell cycle phase transition, initiating DNA synthesis, and regulating cellular transcription and other functions; for example, CDK1 and cyclin B1 accelerate cell division and cell cycle progression via forward regulation. 22,23
3F7Z Protein Preparation: Docking calculations were carried out on 2PRG protein model. Essential hydrogen atoms, Kollman united atom type charges, and solvation parameters were added with the aid of AutoDock tools 25 (Morris, Goodsell et al., 1998). Affinity (grid) maps of 20×20×20 Å grid points and 0.375 Å spacing were generated using the Autogrid program. AutoDock parameter set- and distance- dependent dielectric functions were used in the calculation of the van der Waals and the electrostatic terms, respectively. Figure 2 shows the x-ray co-crystal structure of the Glycogensynthasekinase-3beta protein.
Fig. 4. Hedgehog signaling complex function in Drosophila and mouse. Modes of action of the Hh signaling complex. Matching colors denote homologs. (A) In Drosophila, Cos2 associates with microtubules and scaffolds PKA, CKI and GSK3. This leads to efficient phosphorylation of Ci-155 and limited proteolysis to generate Ci-75. (B) Cos2 binds to the C-tail of Smo when Smo is in its active conformation, leading to the dissociation of PKA, CKI and GSK3. Fu is phosphorylated and in turn phosphorylates Cos2, which might promote the dissociation of Ci-155, leading to activation of Hh target genes. Removal of components of the Hh signaling complex has variable effects on Ci-155 and Ci-75 levels, and the relationship of these protein levels to the activation or repression of Hh target genes is not completely understood. (C) In the mouse, Gli2 and Gli3 are present in small amounts on the primary cilium in the absence of Hh ligand, and the cilium is required for generation of Gli repressors. Kif7 is located at the base of the cilium. (D) Kif7 binds Gli proteins and regulates their translocation to the primary cilium after stimulation of a cell with Hh ligand. Cilia promote activation of Gli2 and Gli3 through unknown mechanisms. Kif7 might also bind Smo, and Smo is required for Kif7 to move up the cilia. The precise makeup of the vertebrate complex in the absence and presence of Hh remains to be determined, although genetic evidence demonstrates that Fu is not an essential part of it. Ci, Cubitus interruptus; CKI, casein kinase I; Cos2, Costal2; FL, full-length; Fu, Fused; GSK3, glycogensynthasekinase 3; Hh, Hedgehog; Kif7, kinesin family member 7; P, phosphate group; PKA, protein kinase A; R, repressor; Smo, Smoothened; Su(fu), Suppressor of fused.
Results: We used AF that was extracted from embryos at 16 days in pregnant SD rat and exposed the AF to the neural cells derived from the embryos of same rat. We found that the treatment of AF to cortical neurons increased the phosphorylation in ERK1/2 that is necessary for fetal neurodevelopment, which was inhibited by the treatment of MEK inhibitors. Moreover, we found the subsequent inhibition of glycogensynthasekinase‑3 (GSK‑3), which is an important determinant of cell fate in neural cells. Indeed, AF increased the neural clustering of cortical neurons, which revealed that the clustered cells were proliferating neural progenitor cells. Accordingly, we confirmed the ability of AF to increase the neural progenitor cells through neurosphere formation. Furthermore, we showed that the ERK/GSK‑3 pathway was involved in AF‑mediated neurosphere enlargement.
The characterization of full-length Tau has shown that the Tau protein can undergo many transitional conforma- tions, and each of the conformations may represent a po- tentially toxic object. Accumulation of the misfolded Tau intermediates in the human brain causes tauopathies, the most common form of AD . The PI3K/ AKT /GSK-3β pathway appears to be crucial for AD because it promotes protein hyper-phosphorylation in Tau. In particular, glycogensynthasekinase-3β (GSK-3β) plays a key role in the neuronal response to stress by phosphorylating and compromising the transcriptional activity of the cAMP re- sponse element binding, which regulates the transcription of the brain-derived neurotrophic factor (BDNF) and other neuropeptides that are important in the regulation of long-term memory and in the maintenance of synaptic plasticity, thereby contributing to the pathology of neuronal degeneration [9,10]. Furthermore, GSK-3β is probably the most documented kinase implicated in the abnormal hyper-phosphorylation of Tau protein.
One postulated mechanism for the anti-migratory effects of LiCl and BIO is through GSK-3 inhibition. Glycogensynthasekinase-3 is thought to be involved in the control of cell migration, through its role in regulating cellular structure alongside microtubule and focal adhesion dynamics (Grimes and Jope, 2001; Sun et al, 2009). In adult HGG, the effect of LiCl and BIO on migration has previously been investigated and their anti-migratory activity has been attributed to their ability to inhibit GSK-3 and stabilise b-catenin via the canonical Wnt signalling pathway (Luo, 2009). In adult glioma models, LiCl has been shown to increase b-catenin reporter activity and b-catenin knockdown has been demonstrated to rescue the anti-migratory effects of BIO (Nowicki et al, 2008; Williams et al, 2011). In our study, we examined b-catenin localisation by IF post treatment of pHGG cells with LiCl and BIO, and observed a marked internalisation of b-catenin to the cytoplasm and nucleus following treatment. This observation has also been noted in adult glioma following LiCl and BIO treatment (Williams, 2011) and provides evidence to support the effectiveness of LiCl and BIO as an inhibitor of GSK-3. Furthermore, western blot analysis of our pHGG lines confirmed that LiCl increased Ser9 phosphorylated GSK-3b (inactivated form) and BIO decreased the activating tyrosine of GSK-3ab.
NAFLD can affect glycogen metabolism , which is the primary storage form of excess energy. Protein phosphatase 1 regulatory subunit 3C (PPP1R3C) is an enzyme that binds to protein phosphatase-1 (PP1) as a regulator which can mediate glycogen metabolism . PPP1R3C encoded protein is called protein targeting to glycogen (PTG) . PTG overexpression can increase glycogen storage . PTG knocked-down could sup- press the cellular glycogen level in mice, and heterozy- gous deletion of PTG in mice also showed glucose and insulin resistance [12, 13]. Glycogensynthasekinase 3β (GSK3β), glycogensynthase (GS) and glycogen phos- phorylase liver type (PYGL) are the down-steam targets of PTG [14, 15]. PTG enhances the de-phosphorylation of GS and causes the activation of glycogen synthesis [16–18]. GSK3β also takes part in regulating the phos- phorylation of GS. PTG is reported to inhibit PYGL ex- pression and phosphorylase (GPa) de-phosphorylation [16, 17], the phosphorylated form of GPa is catalytically active and catalyzes glycogenolysis in liver.
CoQ10 is reported to prevent and treat heart ailments, atherosclerosis, heart failure and coronary artery disease. It also helps in decreasing diabetic complications by increasing the response to oxidative stress, decreasing serum glutaredoxin 1(Grx1) and total antioxidant capacity. Human glycogensynthasekinase 3-β helps in pathogenesis of oxidative stress, mitochondrial dysfunction and disorders related to central nervous system (CNS). It also plays an important role in alternating cellular function[20,21]. Alpha amylase helps in carbohydrate metabolism.
glycogen and lipid metabolism. Biosynthesis of glycogen and lipids is the primary means by which the body stores excess nutrients and is strictly controlled by a complex network of hormones and metabolic signals. Under nor- mal conditions, glycogen is the primary storage form of excess energy. Glycogen production is regulated primarily via enzymes critically involved in glycogen metabolism, including glycogensynthasekinase 3β (GSK3β) and glyco- gen synthase (GS) . However, insulin resistance shifts the major form of energy storage from glycogen to triglyc- erides (TG) in the liver , consistent with reduced GS ac- tivity in patients with type II diabetes . These shifts in energy storage mechanisms increase lipogenesis, enhance cholesterol synthesis, and decrease fatty acid β-oxidation; eventually, such effects may lead to lipotoxicity-induced pancreatic β-cell dysfunction and metabolic syndrome .