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)

Type 1 protein phosphatases (PP-1) comprise a group of widely distributed enzymes that specifically dephosphorylate serine and threonine residues of certain phosphoproteins. They all contain an isoform of the same catalytic subunit, which has an extremely conserved primary structure. One of the properties of PP-1 that allows one to distinguish them from other serine/threonine protein phosphatases is their sensitivity to inhibition by two proteins, termed inhibitor 1 and inhibitor 2, or modulator. The latter protein can also form a 1:1 complex with the catalytic subunit that slowly inactivates upon incubation. This complex is reactivated in vitro by incubation with MgATP and protein kinase FA/GSK-3. In the cell the type 1 catalytic subunit is associated with noncatalytic subunits that determine the activity, the substrate specificity, and the subcellular location of the phosphatase. PP-1 plays an essential role in glycogen metabolism, calcium transport, muscle contraction, intracellular transport, protein synthesis, and cell division. The activity of PP-1 is regulated by hormones like insulin, glucagon, alpha- and beta-adrenergic agonists, glucocorticoids, and thyroid hormones.
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PMID:The structure, role, and regulation of type 1 protein phosphatases. 135 Feb 40

Several polycations were tested for their abilities to inhibit the activity of glycogen synthase kinase 3 (GSK-3). L-Polylysine was the most powerful inhibitor of GSK-3 with half-maximal inhibition of glycogen synthase phosphorylation occurring at approx. 100 nM. D-Polylysine and histone H1 were also inhibitory, but the concentration dependence was complex, and DL-polylysine was the least effective inhibitor. Spermine caused about 50% inhibition of GSK-3 at 0.7 mM and 70% inhibition at 4 mM. Inhibition of GSK-3 by L-polylysine could be blocked or reversed by heparin. A heat-stable polycation antagonist isolated from swine kidney cortex also blocked the inhibitory effect of L-polylysine on GSK-3 and blocked histone H1 stimulation of protein phosphatase 2A activity. Under the conditions tested, L-polylysine also inhibited GSK-3 catalyzed phosphorylation of type II regulatory subunit of cAMP-dependent protein kinase and a 63 kDa brain protein, but only slightly inhibited phosphorylation of inhibitor 2 or proteolytic fragments of glycogen synthase that contain site 3 (a + b + c). L-Polylysine at a concentration (200 nM) that caused nearly complete inhibition of GSK-3 stimulated casein kinase I and casein kinase II, but had virtually no effect on the catalytic subunit of cAMP-dependent protein kinase. These results suggest that polycations can be useful in controlling GSK-3 activity. Polycations have the potential to decrease the phosphorylation state of glycogen synthase at site 3, both by inhibiting GKS-3 as shown in this study and by stimulating the phosphatase reaction as shown previously (Pelech, S. and Cohen, P. (1985) Eur. J. Biochem. 148, 245-251).
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PMID:Inhibitory effect of polycations on phosphorylation of glycogen synthase by glycogen synthase kinase 3. 254 Aug 33

A form of glycogen synthase kinase designated GSK-M3 was purified 4000-fold from rat skeletal muscle by phosphocellulose, Affi-Gel blue, Sephacryl S-300 and carboxymethyl-Sephadex column chromatography. Separation of GSK-M from the catalytic subunit of the cAMP-dependent protein kinase was facilitated by converting the catalytic subunit to the holoenzyme form by addition of the regulatory subunit prior to the gel filtration step. GSK-M had an apparent Mr 62,000 (based on gel filtration), an apparent Km of 11 microM for ATP, and an apparent Km of 4 microM for rat skeletal muscle glycogen synthase. The kinase had very little activity with 0.2 mM GTP as the phosphate donor. Kinase activity was not affected by the addition of cyclic nucleotides, EGTA, heparin, glucose 6-P, glycogen, or the heat-stable inhibitor of cAMP-dependent protein kinase. Phosphorylation of glycogen synthase from rat skeletal muscle by GSK-M reduced the activity ratio (activity in the absence of Glc-6-P/activity in the presence of Glc-6-P X 100) from 90 to 25% when approximately 1.2 mol of phosphate was incorporated per mole of glycogen synthase subunit. Phosphopeptide maps of glycogen synthase obtained after digestion with CNBr or trypsin showed that this kinase phosphorylated glycogen synthase in serine residues found in the peptides containing the sites known as site 2, which is located in the N-terminal CNBr peptide, and site 3, which is located in the C-terminal CNBr peptide of glycogen synthase. In addition to phosphorylating glycogen synthase, GSK-M phosphorylated inhibitor 2 and activated ATP-Mg-dependent protein phosphatase. Activation of the protein phosphatase by GSK-M was dependent on ATP and was virtually absent when ATP was replaced with GTP. GSK-M had minimal activity toward phosphorylase b, casein, phosvitin, and mixed histones. These data indicate that GSK-M, a major form of glycogen synthase kinase from rat skeletal muscle, differs from the known glycogen synthase kinases isolated from rabbit skeletal muscle.
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PMID:Characterization of GSK-M, a glycogen synthase kinase from rat skeletal muscle. 282 16

Prior phosphorylation of its substrate has been shown to be important for substrate recognition by the protein kinase glycogen synthase kinase-3 (GSK-3). Phosphorylation of glycogen synthase by GSK-3 is known to be enhanced by the previous action of casein kinase II and the sequence -SXXXS(P)- was proposed as the minimal recognition determinant for GSK-3. The glycogen binding subunit of type 1 phosphoprotein phosphatase has been shown to be phosphorylated by cyclic AMP-dependent protein kinase at serine-13 in the sequence KPGFS(5)PQPS(9)RRGS(13)ESSEEVYV (F.B. Caudwell, A. Hiraga, and P. Cohen (1986) FEBS Lett. 194, 85-89). Inspection of the sequence revealed potential GSK-3 sites at residues 5 and 9. Using a synthetic peptide with the above sequence, we found that phosphorylation of serine-13 by cyclic AMP-dependent protein kinase permitted the recognition of serine-9 and serine-5 by GSK-3. The work provides another example of a substrate for GSK-3 and demonstrates that the action of GSK-3 is linked to the presence of phosphate in the substrate and not the action of any particular protein kinase. In the course of the analyses, a novel feature of trypsin cleavage of phosphopeptides was noted. In the sequence -SRRGS(P)- trypsin acted uniquely after the first arginine whereas in the sequence -S(P)RRGS(P)- it cleaved randomly at either arginine residue. The fact that GSK-3 could phosphorylate a peptide derived from a phosphatase subunit also raises the possibility that GSK-3 might be involved in controlling glycogen-associated type 1 phosphatase and, more generally, in mediating cyclic AMP control of protein phosphorylation in cells.
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PMID:Phosphoserine as a recognition determinant for glycogen synthase kinase-3: phosphorylation of a synthetic peptide based on the G-component of protein phosphatase-1. 285 Jul 71

Phosphoprotein phosphatase inhibitor-2 (i-2) was rapidly isolated from mouse diaphragm extracts by the use of specific antibodies. The i-2 so obtained was associated with ATP-Mg and FA/GSK-3 dependent phosphatase activity, supporting the idea that i-2 is in fact a component of this form of phosphatase. Inhibitor-2 isolated from diaphragms incubated with [32P]phosphate contained both phosphoserine (approximately 90%) and phosphothreonine (approximately 10%). Therefore, i-2 is multiply phosphorylated in mouse diaphragm and the potential exists for control of the ATP-Mg-dependent phosphatase via multiple phosphorylation sites in vivo.
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PMID:Phosphoprotein phosphatase inhibitor-2 is phosphorylated at both serine and threonine residues in mouse diaphragm. 392 7

The ATP-Mg-dependent phosphoprotein phosphatase is believed to consist of a catalytic subunit and a regulatory component identified as phosphatase inhibitor-2. It was found in this study that isolated inhibitor-2 was phosphorylated in serine residues by casein kinase II to at least 3 mol of phosphate per mol of inhibitor-2 while another protein kinase, F A/GSK-3, introduced no more than 0.3 mol of phosphate per mol exclusively in threonine residues. Analysis of tryptic digests by high performance liquid chromatography indicated that casein kinase II action resulted in two major (peaks 1 and 2) and two minor phosphopeptides whereas F A/GSK-3 action generated only peak 2. Combined action of the two protein kinases introduced an additional 0.4-0.6 mol of phosphate per mol over that predicted for simple additive behavior. This synergistic phosphorylation was associated with increased phosphate in peak 2 and correlated with unchanged phosphoserine but increased phosphothreonine, to a level approaching 1 mol/mol. ATP-Mg-dependent protein phosphatase was either reconstituted from purified inhibitor-2 and low molecular weight type 1 phosphatase or isolated as an inactive complex (Fc). Both phosphatase complexes were activated by F A/GSK-3 which caused a transient phosphorylation of the inhibitor-2 component. Casein kinase II alone phosphorylated the inhibitor-2 in both phosphatase complexes without affecting the enzyme activity. Exposure to the combination of F A/GSK-3 and casein kinase II resulted in a synergistic phosphorylation. Furthermore, the combined action of the two protein kinases caused a synergistic activation of the phosphatase at submaximal F A/GSK-3 levels. The results suggest that interactions between phosphorylation sites may play a role in the activation of the ATP-Mg-dependent phosphatase, in particular that phosphorylation by casein kinase II at serine can potentiate the phosphorylation of threonine by F A/GSK-3 with subsequent influence on phosphatase activation.
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PMID:Synergistic phosphorylation and activation of ATP-Mg-dependent phosphoprotein phosphatase by F A/GSK-3 and casein kinase II (PC0.7). 609 Apr 57

The conservation in evolution of fundamental signal transduction modules offers a means of isolating genes likely to be involved in plant development. We have amplified by PCR Arabidopsis cDNA and genomic sequences related to the product of the shaggy/zeste-white 3 (sgg) segment polarity gene of Drosophila. This regulatory protein is functionally homologous to glycogen synthase kinase-3 in mammals (GSK-3), which regulates, among others, the DNA-binding activity of the c-jun/AP1 transcription factor. Analysis of PCR products led to the identification of five genes; for two of which, corresponding full-length cDNAs, ASK-alpha and gamma (for Arabidopsis shaggy-related protein kinase), were characterized. The encoded proteins were 70% identical to GSK-3 and sgg over the protein kinase catalytic domain and, after production in Escherichia coli, autophosphorylated mainly on threonine and serine residues, but phosphotyrosine was also detected. ASK-alpha and ASK-gamma also phosphorylated phosphatase inhibitor-2 and myelin basic protein, on threonine and serine, respectively. The high conservation of the protein kinases of GSK-3 family, and their action at the transcriptional level, suggest that the ASK proteins have important functions in higher plants.
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PMID:Arabidopsis homologs of the shaggy and GSK-3 protein kinases: molecular cloning and functional expression in Escherichia coli. 750 23

The major phosphorylation site for both casein kinase-2 (CK2) and casein kinase-1 (CK1) in protein phosphatase-1 (PP-1) inhibitor-2 (I-2) is Ser86. Minor phosphorylation sites affected by either CK2 or CK1 are Ser120/Ser121 and Ser174, respectively. A synthetic peptide of 25 amino acids encompassing residues 67-93 of I-2 is phosphorylated by either CK2 or CK1 at its seryl residue corresponding to Ser86 with higher Vmax and Km values similar to those of the intact protein (9 vs 7.2 microM and 14.2 vs 5.3 microM with CK2 and CK1, respectively). No detectable phosphorylation of this peptide which also includes the glycogen synthase kinase-3 (GSK-3) site (Thr72), could be observed with either GSK-3 or p34cdc2 kinase whether or not its seryl residue equivalent to Ser86 had been previously phosphorylated by CK2. Shorter derivatives of I-2(67-93), encompassing residues 72-93 and 78-93, are also readily phosphorylated by both CK1 and CK2, with phosphorylation efficiencies similar to those of the parent peptide. A synthetic heptadecapeptide reproducing the phosphoacceptor site around Ser120/Ser121 is phosphorylated by CK2, but not to any detectable extent by CK1, with a Km value fivefold higher than that of the corresponding pentadecapeptide including Ser86 (78-93). A synthetic pentadecapeptide (166-180) reproducing the phosphoacceptor site around Ser174 is phosphorylated by CK1 less efficiently than the pentadecapeptide including its main phosphorylation site (78-93) (Km 280 microM vs 33 microM). This peptide is readily phosphorylated by CK2 as well, although it lacks the canonical consensus sequence for CK2 and its Ser174 is almost unaffected by CK2 in intact I-2. These data provide the clear-cut demonstration that the consensus sequence with N-terminal prephosphorylated residue(s), SerP/ThrP-Xaa-Xaa-Ser/Thr, [Flotow, H., Graves, P. R., Wang, A., Fiol, C. J., Roeske, R. W. & Roach, P. J. (1990) J. Biol. Chem. 265, 14264-14269; Meggio, F., Perich, J. W., Reynolds, E. C. & Pinna, L. A. (1991) FEBS Lett. 283, 303-306] is not always required to achieve efficient and high-affinity phosphorylation by CK1. They also show that the specificity determinants for I-2 phosphorylation by either CK2 or CK1, but not by GSK3, are entirely grounded on local structural features of the phosphoacceptor site, being only marginally affected by the overall structure of I-2.
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PMID:Phosphorylation of synthetic fragments of inhibitor-2 of protein phosphatase-1 by casein kinase-1 and -2. Evidence that phosphorylated residues are not strictly required for efficient targeting by casein kinase-1. 805 35

In vitro, the modulator protein (inhibitor-2) slowly converts the catalytic subunit of protein phosphatase-1 (PP-1C) into an inactive 'MgATP-dependent form' that can be reactivated by the transient phosphorylation of modulator with GSK-3/FA. We report here that this modulator-induced inactivation of PP-1C can be blocked by addition (at pH 7.5) of either 0.3 mM NaF or 150 mM NaCl, or by raising the pH to 8.5. Making use of a combination of the latter conditions, we have partially purified a soluble modulator-associated form of PP-1 (PP-1S) from rabbit skeletal muscle as a spontaneously active enzyme that cannot be further activated by kinase GSK-3/FA. These observations argue against a role for the 'MgATP-dependent' form of PP-1S as an inactive reservoir of PP-1C. PP-1S was separated on aminohexyl Sepharose from another active, cytosolic species of PP-1, which appears to be a proteolytic product of the glycogen-bound PP-1G.
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PMID:Native cytosolic protein phosphatase-1 (PP-1S) containing modulator (inhibitor-2) is an active enzyme. 818 83

Phosphorylation of inhibitor 2, the regulatory subunit of the ATP-Mg-dependent protein phosphatase, by glycogen synthase kinase 3 (GSK-3) causes activation of the phosphatase. Prior phosphorylation by casein kinase II has been shown to enhance both phosphorylation and activation of the phosphatase by GSK-3 (DePaoli-Roach, A. A. (1984) J. Biol. Chem. 259, 12144-12152). Reported here is a comparison of the phosphorylation of inhibitor 2 by two defined isoforms of GSK-3, GSK-3 alpha and GSK-3 beta. GSK-3 beta was a significantly better inhibitor 2 kinase than was GSK-3 alpha. The Vmax/Km value for GSK-3 beta was approximately 10-fold higher than that for GSK-3 alpha. GSK-3 beta phosphorylated inhibitor 2 to a stoichiometry of approximately 1.0 mol of phosphate/mol of inhibitor 2. The phosphorylation by GSK-3 beta was determined to be exclusively at Thr-72 on the basis of the inability of the enzyme to modify a mutant inhibitor 2 in which Thr-72 was changed to alanine. Prior phosphorylation by casein kinase II promoted the action of GSK-3 alpha in keeping with earlier reports using undefined GSK-3 preparations. Phosphorylation by GSK-3 beta, in contrast, was unaffected by the previous action of casein kinase II. These results suggest that there can be important differences in substrate recognition by different isoforms of the same protein kinase and may help explain why some reported GSK-3 substrates require prior phosphorylation whereas other do not.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Isoform differences in substrate recognition by glycogen synthase kinases 3 alpha and 3 beta in the phosphorylation of phosphatase inhibitor 2. 828 31


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