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

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)
 ...
PMID:Isoform differences in substrate recognition by glycogen synthase kinases 3 alpha and 3 beta in the phosphorylation of phosphatase inhibitor 2. 828 31

Inhibitor-2 (I-2) is the regulatory subunit of the ATP-Mg-dependent phosphatase, a cytosolic form of type 1 protein phosphatase. Phosphorylation of I-2 at Thr-72 by the protein kinase glycogen synthase kinase-3 (GSK-3) leads to activation of the enzyme. Casein kinase II action was shown to synergistically enhance phosphorylation and activation by GSK-3 (DePaoli-Roach, A.A. (1984) J. Biol. Chem. 259, 12144-12152). Rabbit skeletal muscle and liver I-2 cDNA clones have been isolated. Rabbit skeletal muscle cDNAs could be placed in two subtypes, differing in the length of the 3'-untranslated region. The coding sequence of 612 nucleotides was identical in the two skeletal muscle and the liver cDNAs and predicted a protein of 204 amino acids, consistent with analysis of the purified protein. Northern hybridization analysis indicated that the two mRNAs of 1.7 and 2.7 kilobase pairs were present in all rabbit tissues examined, except in liver, where only the larger transcript was detected, and in testis, where additional transcripts were present. Expression in Escherichia coli of wild-type and phosphorylation site mutants resulted in the production of I-2 polypeptides with apparent M(r) values of approximately 31,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The inhibitory activity of the recombinant proteins was similar to that of native rabbit skeletal muscle I-2 and was unaffected by the substitution of alanine for the GSK-3 site (Thr-72) and for the casein kinase II sites (Ser-86 and Ser-120/121) or by substitution of glutamic acid and aspartic acid for Thr-72 and Ser-86. Recombinant wild-type I-2 and the Ala-120/121 mutant were phosphorylated synergistically by GSK-3 and casein kinase II. The Thr-72 and Ser-86 mutants, however, did not undergo this synergistic phosphorylation. Our studies indicate that Thr-72 is the only GSK-3 site and that Ser-86 is the casein kinase II site required for the potentiation of GSK-3 action. Furthermore, acidic residues cannot substitute for the phosphate group either in enhancing GSK-3 phosphorylation or in activating the phosphatase.
 ...
PMID:Molecular mechanism of the synergistic phosphorylation of phosphatase inhibitor-2. Cloning, expression, and site-directed mutagenesis of inhibitor-2. 828 48

Mg-ATP-dependent protein phosphatase activating factor [kinase FA/glycogen synthase kinase 3 (GSK-3)] has been identified in highly purified clathrin-coated vesicles (CCVs) isolated from pig brain. Kinase FA was found to exist in an inactive state but can be activated by 1% Triton X-100 or 1 M Tris-HCl extraction in brain CCVs. Activation of kinase FA in CCVs is due to disassociation of the kinase from CCVs as demonstrated on sucrose density-gradient ultracentrifugation and Sepharose CL-4B gel filtration. Using purified brain CCVs as substrates, kinase FA enhanced the endogenous phosphorylation of assembly protein complexes in the molecular weight range of 100,000-130,000 severalfold, as demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography. Comparisons with well-defined brain CCV-associated endogenous protein kinases such as pp50 kinase/AP50 and casein kinase 2 provide evidence that kinase FA/GSK-3 represents a third potent and unique CCV-associated protein kinase distinctly different from the previously described CCV protein kinases, suggesting the possible involvement of kinase FA in the regulation of CCV functions in the brain. The results also support the notion that protein kinase FA is involved in cell surface signal transduction in the CNS.
 ...
PMID:Identification and characterization of protein kinase FA/glycogen synthase kinase 3 in clathrin-coated brain vesicles. 838 21

The ATP.Mg-dependent protein phosphatase activating factor (FA) has been identified as a microtubule protein kinase and as a microtubule protein phosphatase activator. FA could phosphorylate microtubule-associated tau protein up to 4 moles of phosphates per mole of protein. However, more than 80% of the phosphates in 32P-tau phosphorylated by FA could be removed by ATP.Mg-dependent protein phosphatase and the tau phosphatase activity was FA-dependent. Functional study further revealed that as a tau kinase, FA could phosphorylate tau and thereby inhibits cross-linking copolymerization of tau with tubulin and actin filaments whereas as a tau phosphatase activating factor, FA could promote copolymerization of tau with tubulin and actin filaments. Taken together, the results provide evidence that a cyclic modulation of cytoskeleton assembly-disassembly can be controlled by FA, representing an efficient cyclic cascade mechanism for rapid structural and functional regulation of cytoskeletal system in the central nervous system.
 ...
PMID:Cyclic modulation of cytoskeleton assembly-disassembly by the ATP.Mg-dependent protein phosphatase activator (kinase FA). 839 3

A systematic analysis reveals that out of 20 protein kinases examined, specific for either Ser/Thr or Tyr, the majority are extremely sensitive to staurosporine, with IC50 values in the low nanomolar range. A few of them however, notably protein kinases CK1 and CK2, mitogen-activated protein (MAP) kinase and protein-tyrosine kinase CSK, are relatively refractory to staurosporine inhibition, exhibiting IC50 values in the micromolar range. With all protein kinases tested, namely PKA, CK1, CK2, MAP kinase (ERK-1), c-Fgr, Lyn, CSK and TPK-IIB/p38Syk, staurosporine inhibition was competitive with respect to ATP, regardless of its inhibitory power. In contrast, either uncompetitive or noncompetitive kinetics of inhibition with respect to the phosphoacceptor substrate were exhibited by Ser/Thr and Tyr-specific protein kinases, respectively, consistent with a different mechanism of catalysis by these two sub-families of kinases. Computer modeling based on PKA crystal structure in conjunction with sequence analysis suggest that the low sensitivity to staurosporine of CK2 may be accounted for by the bulky nature of three residues, Val66, Phe113 and Ile174 which are homologous to PKA Ala70, Met120 and Thr183, respectively. In contrast these PKA residues are either conserved or replaced by smaller ones in protein kinases highly sensitive to staurosporine inhibition. On the other hand, His160 which is homologous to PKA Glu170, appears to be responsible for the unique behaviour of CK2 with respect to a staurosporine derivative (CGP44171A) bearing a negatively charged benzoyl substituent: while CGP44171A is 10- 100-fold less effective than staurosporine against PKA and most of the other protein kinases tested, it is actually more effective than staurosporine for CK2 inhibition, but it looses part of its efficacy if it is tested on a CK2 mutant (H160D) in which His160 has been replaced by Asp. It can be concluded from these data that the catalytic sites of protein kinases are divergent enough as to allow a competitive inhibitor like staurosporine to be fairly selective, a feature that can be enhanced by suitable modifications designed based on the structure of the catalytic site of the kinase.
 ...
PMID:Different susceptibility of protein kinases to staurosporine inhibition. Kinetic studies and molecular bases for the resistance of protein kinase CK2. 852 58

TPK-IIB is a protein kinase that is predominant in the cytosol of spleen and is characterized by a high specific activity toward acidic peptide substrates and a low auto-phosphorylation activity. A prominent 52-kDa component purifies with the kinase [Marin, O., Donella-Deana, A., Brunati, A. M., Fischer, S. & Pinna, L. A. (1991) J. Biol. Chem. 266, 17798-17803]. Here we demonstrate that the 52-kDa protein displays sequence identity with the Miller-Dieker lissencephaly protein (LIS 1). The protein is not related to any known protein kinase and lacks an ATP-binding motif. The ATP binding and phosphotransferase activities of TPK-IIB can be fully accounted for by a minor 38-kDa protein band (p38/TPK-IIB) which can be separated from the 52-kDa protein by Mono-Q/FPLC in the presence of EDTA. Sequence analysis of p38/TPK-IIB reveals a high level of similarity, if not identity, with the catalytic domain of p72syk, a protein-tyrosine kinase implicated in the activation of hematopoietic cells. Antibodies raised against the catalytic domain of p72syk, but not antibodies raised against its N-terminal segment, cross-react with p38/TPK-IIB. The peptide substrate specificity of p72syk is almost identical to that of p38/TPK-IIB, which also supports the classification of TPK-IIB as a close relative (possibly a proteolytic or alternative spliced form) of p72syk. p38/TPK-IIB, however, exhibits a specific activity which is sixfold higher than that of p72syk and appears to be 50-fold more sensitive to inhibition by heparin. Thus, the observation that Ca(2+)-dependent degradation of p72syk by particulate fraction of rat spleen is accompanied by increased catalytic activity and increased sensitivity to heparin would be consistent with the possibility that hyperactive p38/TPK-IIB might be proteolytically generated from p72syk in response to an increase of intracellular Ca2+.
 ...
PMID:The spleen protein-tyrosine kinase TPK-IIB is highly similar to the catalytic domain of p72syk. 884 5

Alzheimer disease is characterized by a specific type of neuronal degeneration in which the microtubule associated protein tau is abnormally hyperphosphorylated causing the disruption of the microtubule network. We have found that the phosphorylation of human tau (tau3L) by A-kinase, GSK-3 or CK-1 inhibits its microtubule assembly-promoting and microtubule-binding activities. However, the inhibition of these activities of tau by GSK-3 is significantly increased if tau is prephosphorylated by A-kinase or CK-1. The most potent inhibition is observed by combination phosphorylation of tau with A-kinase and GSK-3. Under these conditions, only very few microtubules are seen by electron microscopy. Sequencing of 32P-labeled trypsin phosphopeptides from tau prephosphorylated by A-kinase (using unlabeled ATP) and further phosphorylated by GSK-3 in the presence of [gamma-32P]ATP revealed that Ser-195, Ser-198, Ser-199, Ser-202, Thr-205, Thr-231, Ser-235, Ser-262, Ser-356 and Ser-404 are phosphorylated, whereas if tau is not prephosphorylated by A-kinase, GSK-3 phosphorylates it at Thr-181, Ser-184, Ser-262, Ser-356 and Ser-400. These data suggest that (i) prephosphorylation of tau by A-kinase makes additional and different sites accessible for phosphorylation by GSK-3; (ii) phosphorylation of tau at these additional sites further inhibits the biological activity of tau in its ability to bind to microtubules and promote microtubule assembly. Thus a combined role of A-kinase and GSK-3 should be considered in Alzheimer neurofibrillary degeneration.
 ...
PMID:Tau is phosphorylated by GSK-3 at several sites found in Alzheimer disease and its biological activity markedly inhibited only after it is prephosphorylated by A-kinase. 977 88

Paullones constitute a new family of benzazepinones with promising antitumoral properties. They were recently described as potent, ATP-competitive, inhibitors of the cell cycle regulating cyclin-dependent kinases (CDKs). We here report that paullones also act as very potent inhibitors of glycogen synthase kinase-3beta (GSK-3beta) (IC50: 4-80 nM) and the neuronal CDK5/p25 (IC50: 20-200 nM). These two enzymes are responsible for most of the hyperphosphorylation of the microtubule-binding protein tau, a feature observed in the brains of patients with Alzheimer's disease and other neurodegenerative 'taupathies'. Alsterpaullone, the most active paullone, was demonstrated to act by competing with ATP for binding to GSK-3beta. Alsterpaullone inhibits the phosphorylation of tau in vivo at sites which are typically phosphorylated by GSK-3beta in Alzheimer's disease. Alsterpaullone also inhibits the CDK5/p25-dependent phosphorylation of DARPP-32 in mouse striatum slices in vitro. This dual specificity of paullones may turn these compounds into very useful tools for the study and possibly treatment of neurodegenerative and proliferative disorders.
 ...
PMID:Paullones are potent inhibitors of glycogen synthase kinase-3beta and cyclin-dependent kinase 5/p25. 1099 59

The bis-indole indirubin is an active ingredient of Danggui Longhui Wan, a traditional Chinese medicine recipe used in the treatment of chronic diseases such as leukemias. The antitumoral properties of indirubin appear to correlate with their antimitotic effects. Indirubins were recently described as potent (IC(50): 50-100 nm) inhibitors of cyclin-dependent kinases (CDKs). We report here that indirubins are also powerful inhibitors (IC(50): 5-50 nm) of an evolutionarily related kinase, glycogen synthase kinase-3beta (GSK-3 beta). Testing of a series of indoles and bis-indoles against GSK-3 beta, CDK1/cyclin B, and CDK5/p25 shows that only indirubins inhibit these kinases. The structure-activity relationship study also suggests that indirubins bind to GSK-3 beta's ATP binding pocket in a way similar to their binding to CDKs, the details of which were recently revealed by crystallographic analysis. GSK-3 beta, along with CDK5, is responsible for most of the abnormal hyperphosphorylation of the microtubule-binding protein tau observed in Alzheimer's disease. Indirubin-3'-monoxime inhibits tau phosphorylation in vitro and in vivo at Alzheimer's disease-specific sites. Indirubins may thus have important implications in the study and treatment of neurodegenerative disorders. Indirubin-3'-monoxime also inhibits the in vivo phosphorylation of DARPP-32 by CDK5 on Thr-75, thereby mimicking one of the effects of dopamine in the striatum. Finally, we show that many, but not all, reported CDK inhibitors are powerful inhibitors of GSK-3 beta. To which extent these GSK-3 beta effects of CDK inhibitors actually contribute to their antimitotic and antitumoral properties remains to be determined. Indirubins constitute the first family of low nanomolar inhibitors of GSK-3 beta to be described.
 ...
PMID:Indirubins inhibit glycogen synthase kinase-3 beta and CDK5/p25, two protein kinases involved in abnormal tau phosphorylation in Alzheimer's disease. A property common to most cyclin-dependent kinase inhibitors? 1101 32

The mechanism by which lithium (Li(+)) inhibits the protein kinase glycogen synthase kinase-3 (GSK-3) is unknown. Here, we demonstrate that Li(+) is a competitive inhibitor of GSK-3 with respect to magnesium (Mg(2+)), but not to substrate or ATP. This mode of inhibition is conserved between mammalian and Dictyostelium GSK-3 isoforms, and is not experienced with other group I metal ions. As a consequence, the potency of Li(+) inhibition is dependent on Mg(2+) concentration. We also found that GSK-3 is sensitive to chelation of free Mg(2+) by ATP and is progressively inhibited when ATP concentrations exceed that of Mg(2+). Given the cellular concentrations of ATP and Mg(2+), our results indicate that Li(+) will have a greater effect on GSK-3 activity in vivo than expected from in vitro studies and this may be a factor relevant to its use in the treatment of depression.
 ...
PMID:Lithium inhibits glycogen synthase kinase-3 by competition for magnesium. 1116 80


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>