Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.26 (GSK)
 6,788 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The inhibitory potencies of bioflavonoids on various tyrosine protein kinases and serine/threonine protein kinases were investigated. The phosphotransferase activity of an oncogene product, pp130fps, and a growth factor receptor, insulin receptor, were inhibited by myricetin, a derivative of quercetin. However, tyrosine kinase activity in the particulate fraction from human platelets (PM-TPK) was resistant to myricetin. Apparent Ki values of myricetin for tyrosine protein kinases of pp130fps and insulin receptor were 1.8 and 2.6 microM, respectively. The Ki values for serine/threonine kinase activities of myosin light chain kinase (MLC-kinase), casein kinase I, casein kinase II, cAMP-dependent protein kinase, and protein kinase C were 1.7 microM, 9.0 microM, 0.6 microM, 27.5 microM, and 12.1 microM, respectively. Lineweaver-Burk plots revealed that myricetin competitively inhibits pp130fps tyrosine kinase, myosin light chain kinase, casein kinase I and II with ATP, but does not inhibit other protein kinases. Since myricetin is a hydroxylated derivative of quercetin, the inhibitory effects of a series of seven flavonoids with various numbers of hydroxy residues were examined. Structure activity studies exhibited that the inhibitory potencies of the flavonoids for tyrosine kinases of pp130fps and insulin receptor correlated with the number of hydroxy residues on the flavone rings (gamma = 0.974 and 0.926, respectively), whereas the hydroxylation influenced to a lesser extent the inhibitory potencies for serine/threonine protein kinase. The hydroxy residues at position 3' and 5' did not affect the activities of cAMP-dependent protein kinase, and protein kinase C, and the hydroxylation at position 5' is detrimental for the inhibition of MLC-kinase, and casein kinase I and II. Thus, flavonoids may be useful tools to elucidate the active site of tyrosine and serine/threonine protein kinases.
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PMID:Differential effects of flavonoids as inhibitors of tyrosine protein kinases and serine/threonine protein kinases. 316 98

WNT-7a induces axonal spreading and branching in developing cerebellar granule neurons. This effect is mediated through the inhibition of GSK-3beta, a serine/threonine kinase and a component of the WNT pathway. Lithium, an inhibitor of GSK-3beta, mimics WNT-7a in granule cells. Here we examined further the effect of GSK-3beta inhibition on cytoskeletal re-organisation. Lithium induces axonal spreading and increases growth cone area and perimeter. This effect is associated with the absence or reduction of stable microtubules in spread areas. Lithium induces the loss of a phosphorylated form of MAP-1B, a microtubule associated protein involved in axonal outgrowth. Down-regulation of the phosphorylated MAP-1B, MAP-1B-P, from axonal processes occurs before axonal remodelling is evident. In vitro phosphorylation assays show that MAP-1B-P is generated by direct phosphorylation of MAP-1B by GSK-3beta. WNT-7a, like lithium, also leads to loss of MAP-1B-P from spread axons and growth cones. Our data suggest that WNT-7a and lithium induce changes in microtubule dynamics by inhibiting GSK-3beta which in turn lead to changes in the phosphorylation of MAP-1B. These findings suggest a novel role for GSK-3beta and WNTs in axonal remodelling and identify MAP-1B as a new target for GSK-3beta and WNT.
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PMID:Inhibition of GSK-3beta leading to the loss of phosphorylated MAP-1B is an early event in axonal remodelling induced by WNT-7a or lithium. 957 Jul 53

Axin is a negative regulator of embryonic axis formation in vertebrates, which acts through a Wnt signal transduction pathway involving the serine/threonine kinase GSK-3 and beta-catenin. Axin has been shown to have distinct binding sites for GSK-3 and beta-catenin and to promote the phosphorylation of beta-catenin and its consequent degradation. This provides an explanation for the ability of Axin to inhibit signaling through beta-catenin. In addition, a more N-terminal region of Axin binds to adenomatous polyposis coli (APC), a tumor suppressor protein that also regulates levels of beta-catenin. Here, we report the results of a yeast two-hybrid screen for proteins that interact with the C-terminal third of Axin, a region in which no binding sites for other proteins have previously been identified. We found that Axin can bind to the catalytic subunit of the serine/threonine protein phosphatase 2A through a domain between amino acids 632 and 836. This interaction was confirmed by in vitro binding studies as well as by co-immunoprecipitation of epitope-tagged proteins expressed in cultured cells. Our results suggest that protein phosphatase 2A might interact with the Axin.APC.GSK-3.beta-catenin complex, where it could modulate the effect of GSK-3 on beta-catenin or other proteins in the complex. We also identified a region of Axin that may allow it to form dimers or multimers. Through two-hybrid and co-immunoprecipitation studies, we demonstrated that the C-terminal 100 amino acids of Axin could bind to the same region as other Axin molecules.
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PMID:Identification of a domain of Axin that binds to the serine/threonine protein phosphatase 2A and a self-binding domain. 992 Aug 88

Although the precise mechanisms contributing to insulin resistance and type 2 diabetes are unknown, it is believed that defects in downstream components of the insulin signaling pathway may be involved. In this work, we hypothesize that a serine/threonine kinase, glycogen synthase kinase-3 (GSK-3), may be pertinent in this regard. To test this hypothesis, we examined GSK-3 activity in two inbred mouse strains known to be susceptible (C57BL/6J) or resistant (A/J) to diet-induced obesity and diabetes. Examination of GSK-3 in fat, liver, and muscle tissues of C57BL/6J mice revealed that GSK-3 activity increased twofold in the epididymal fat tissue and remained unchanged in muscle and liver of mice fed a high-fat diet, compared with their low-fat diet-fed counterparts. In contrast, GSK-3 activity did not change in the epididymal fat tissue of A/J mice, regardless of the type of diet they were fed. In addition, both basal and diet-induced GSK-3 activity was higher (2.3- and 3.2-fold, respectively) in the adipose tissue of C57BL/6J mice compared with that in A/J mice. Taken together, our studies suggest an unsuspected link between increased GSK-3 activity and development of insulin resistance and type 2 diabetes in fat tissue of C57BL/6J mice, and implicate GSK-3 as a potential factor contributing to susceptibility of C57BL/6J mice to diet-induced diabetes.
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PMID:Increased glycogen synthase kinase-3 activity in diabetes- and obesity-prone C57BL/6J mice. 1042 88

We have previously shown that the B cell Ag receptor (BCR) activates phosphatidylinositol (PI) 3-kinase. We now show that a serine/threonine kinase called Akt or protein kinase B is a downstream target of PI 3-kinase in B cells. Akt has been shown to promote cell survival as well as the transcription and translation of proteins involved in cell cycle progression. Using an Ab that specifically recognizes the activated form of Akt that is phosphorylated on serine 473, we show that BCR engagement activates Akt in a PI 3-kinase-dependent manner. These results were confirmed using in vitro kinase assays. Moreover, BCR ligation also induced phosphorylation of Akt of threonine 308, another modification that is required for activation of Akt. In the DT40 chicken B cell line, phosphorylation of Akt on serine 473 was completely dependent on the Lyn tyrosine kinase, while the Syk tyrosine kinase was required for sustained phosphorylation of Akt. Complementary experiments in BCR-expressing AtT20 endocrine cells confirmed that Src kinases are sufficient for BCR-induced Akt phosphorylation, but that Syk is required for sustained phosphorylation of Akt on both serine 473 and threonine 308. In insulin-responsive cells, Akt phosphorylates and inactivates the serine/threonine kinase glycogen synthase kinase-3 (GSK-3). Inactivation of GSK-3 may promote nuclear accumulation of several transcription factors, including NF-ATc. We found that BCR engagement induced GSK-3 phosphorylation and decreased GSK-3 enzyme activity. Thus, BCR ligation initiates a PI 3-kinase/Akt/GSK-3 signaling pathway.
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PMID:The B cell antigen receptor activates the Akt (protein kinase B)/glycogen synthase kinase-3 signaling pathway via phosphatidylinositol 3-kinase. 1043 24

Glycogen synthase kinase 3 (GSK-3) is implicated in multiple biological processes including metabolism, gene expression, cell fate determination, proliferation, and survival. GSK-3 activity is inhibited through phosphorylation of serine 21 in GSK-3 alpha and serine 9 in GSK-3 beta. These serine residues of GSK-3 have been previously identified as targets of protein kinase B (PKB/Akt), a serine/threonine kinase located downstream of phosphatidylinositol 3-kinase. Here, we show that serine 21 in GSK-3 alpha and serine 9 in GSK-3 beta are also physiological substrates of cAMP-dependent protein kinase A. Protein kinase A physically associates with, phosphorylates, and inactivates both isoforms of GSK-3. The results indicate that depending on the stimulatory context, the activity of GSK-3 can be modulated either by growth factors that work through the phosphatidylinositol 3-kinase-protein kinase B cascade or by hormonal stimulation of G protein-coupled receptors that link to changes in intracellular cAMP levels.
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PMID:Phosphorylation and inactivation of glycogen synthase kinase 3 by protein kinase A. 1103 10

Protein kinase C-zeta (PKC-zeta) is a serine/threonine kinase downstream from phosphatidylinositol 3-kinase in insulin signaling pathways. However, specific substrates for PKC-zeta that participate in the biological actions of insulin have not been reported. In the present study, we identified insulin receptor substrate-1 (IRS-1) as a novel substrate for PKC-zeta. Under in vitro conditions, wild-type PKC-zeta (but not kinase-deficient mutant PKC-zeta) significantly phosphorylated IRS-1. This phosphorylation was reversed by treatment with the serine-specific phosphatase, protein phosphatase 2A. In addition, the overexpression of PKC-zeta in NIH-3T3(IR) cells caused significant phosphorylation of cotransfected IRS-1 as demonstrated by [(32)P]orthophosphate labeling experiments. In rat adipose cells, endogenous IRS-1 coimmunoprecipitated with endogenous PKC-zeta, and this association was increased 2-fold upon insulin stimulation. Furthermore, the overexpression of PKC-zeta in NIH-3T3(IR) cells significantly impaired insulin-stimulated tyrosine phosphorylation of cotransfected IRS-1. Importantly, this was accompanied by impaired IRS-1-associated phosphatidylinositol 3-kinase activity. Taken together, our results raise the possibility that IRS-1 is a novel physiological substrate for PKC-zeta. Because PKC-zeta is located downstream from IRS-1 and phosphatidylinositol 3-kinase in established insulin signaling pathways, PKC-zeta may participate in negative feedback pathways to IRS-1 similar to those described previously for Akt and GSK-3.
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PMID:Protein kinase C-zeta phosphorylates insulin receptor substrate-1 and impairs its ability to activate phosphatidylinositol 3-kinase in response to insulin. 1106 44

A competitive fluorescence polarization (FP) assay has been developed for the serine/threonine kinase, AKT. The FP assay has been formatted in a 384-well microtiter plate and automated using a pipeting workstation with performance suitable for high-throughput screening. The assay design utilizes a fluorescent phosphorylated peptide complexed to a product-specific anti-phospho-serine antibody. When unlabeled substrate is phosphorylated, by the kinase, the product competes with the fluorescent phosphorylated peptide for the antibody. The fluorescent phosphorylated peptide is then released from the antibody into solution resulting in a loss in polarization signal. Seven fluorescent phosphorylated peptides and 19 antibodies were evaluated for this assay. RARTSpSFAEPGK-Fl peptide and anti-phospho-GSK-3alpha Ser21 antibody gave the best affinity and change in polarization signal. The apparent kinetic constants were calculated for the FP assay and were consistent with reported values. The FP assay was validated with known inhibitors and the results compared to a radioactive Flashplate transfer assay, utilizing [(33)P]ATP and a biotinylated substrate, also developed in our laboratory. The IC(50) values generated were comparable between the two methods suggesting the competitive FP assay and Flashplate assay have similar sensitivities and abilities to identify inhibitors during screening.
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PMID:Development and validation of a competitive AKT serine/threonine kinase fluorescence polarization assay using a product-specific anti-phospho-serine antibody. 1172 83

Lysophosphatidic acid (LPA) is a natural phospholipid with multiple biological functions. We show here that LPA induces phosphorylation and inactivation of glycogen synthase kinase 3 (GSK-3), a multifunctional serine/threonine kinase. The effect of LPA can be reconstituted by expression of Edg-4 or Edg-7 in cells lacking LPA responses. Compared to insulin, LPA stimulates only modest phosphatidylinositol 3-kinase (PI3K)-dependent activation of protein kinase B (PKB/Akt) that does not correlate with the magnitude of GSK-3 phosphorylation induced by LPA. PI3K inhibitors block insulin- but not LPA-induced GSK-3 phosphorylation. In contrast, the effect of LPA, but not that of insulin or platelet-derived growth factor (PDGF), is sensitive to protein kinase C (PKC) inhibitors. Downregulation of endogenous PKC activity selectively reduces LPA-mediated GSK-3 phosphorylation. Furthermore, several PKC isotypes phosphorylate GSK-3 in vitro and in vivo. To confirm a specific role for PKC in regulation of GSK-3, we further studied signaling properties of PDGF receptor beta subunit (PDGFRbeta) in HEK293 cells lacking endogenous PDGF receptors. In clones expressing a PDGFRbeta mutant wherein the residues that couple to PI3K and other signaling functions are mutated with the link to phospholipase Cgamma (PLCgamma) left intact, PDGF is fully capable of stimulating GSK-3 phosphorylation. The process is sensitive to PKC inhibitors in contrast to the response through the wild-type PDGFRbeta. Therefore, growth factors, such as PDGF, which control GSK-3 mainly through the PI3K-PKB/Akt module, possess the ability to regulate GSK-3 through an alternative, redundant PLCgamma-PKC pathway. LPA and potentially other natural ligands primarily utilize a PKC-dependent pathway to modulate GSK-3.
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PMID:Convergence of multiple signaling cascades at glycogen synthase kinase 3: Edg receptor-mediated phosphorylation and inactivation by lysophosphatidic acid through a protein kinase C-dependent intracellular pathway. 1188 98

Glycogen synthase kinase-3beta (GSK-3beta) is a ubiquitously expressed constitutively active serine/threonine kinase that phosphorylates cellular substrates and thereby regulates a wide variety of cellular functions, including development, metabolism, gene transcription, protein translation, cytoskeletal organization, cell cycle regulation, and apoptosis. The activity of GSK-3beta is negatively regulated by protein kinase B/Akt and by the Wnt signaling pathway. Increasing lines of evidence show that GSK-3beta is an essential negative regulator of cardiac hypertrophy and that the inhibition of GSK-3beta by hypertrophic stimuli is an important mechanism contributing to the development of cardiac hypertrophy. GSK-3beta also plays an important role in regulating cardiac development. In this review, the role of GSK-3beta in cardiac hypertrophy and development and the potential underlying mechanisms are discussed.
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PMID:Glycogen synthase kinase-3beta: a novel regulator of cardiac hypertrophy and development. 1203 94


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