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)

Multifunctional ATP-citrate lyase kinase (ACLK) exhibits several properties that are similar to glycogen-synthase kinase-3 (GSK-3). The molecular cloning of two distinct mammalian GSK-3 cDNAs and a Drosophila melanogaster (fruitfly) homologue, zeste-white3sgg, has established the existence of a GSK-3 subfamily. A multifunctional protein kinase first identified as an ACLK has recently been shown to exhibit several similarities to the alpha- and beta-forms of GSK-3. Here we have used immunological and biochemical analyses to directly compare these enzymes. Thus purified preparations of ACLK isolated from brain and liver preferentially cross-react with anti-GSK-3 alpha antisera and phosphorylate previously defined substrates of GSK-3 at identical sites. Conversely, both alpha- and beta-forms of GSK-3 phosphorylated ATP-citrate lyase at the same site(s) targeted by ACLK. These, and other similarities, demonstrate ACLK to be identical with, or highly related to, GSK-3 alpha, the implications of which are discussed.
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PMID:Identification of multifunctional ATP-citrate lyase kinase as the alpha-isoform of glycogen synthase kinase-3. 133 98

Study of GSK-3 had an inauspicious beginning rooted in intermediary metabolism. However, owing to the fortuitous convergence of several disparate areas of biology, the enzyme now offers unique opportunities for study of the control of a variety cellular processes. While at first sight a role in transcriptional regulation appears unlikely for a protein first identified as acting on glycogen synthase, it is even more surprising that the same protein should be functionally interchangeable with a fruit fly homeotic gene. Such understandable scepticism, however, is based on teleological bias. Glycogen synthase is a critical enzyme regulating glucose storage. The c-Jun oncoprotein may have the potential to transform cells but this does not excuse it from similar mechanisms of control to glycogen synthase. Likewise, homeotic genes play a crucial role in setting up the body plan of an embryo but must also be subject to control. The main difference is that when such control is lost, the result is rather graphic. It is, therefore, only to be expected that regulatory protein kinases will surface in superficially quite unrelated areas and that many of their targets will be 'housekeeping' proteins. Perhaps the most difficult aspect of protein phosphorylation research is the linking of physiological substrates with particular protein kinases, hence reconstructing pathways. No matter how compelling in vitro data appear, there must be demonstration that the protein is targeted by the specific protein kinase in cells, an extremely difficult process. Most progress in this respect has been made using genetic analysis in lower organisms, especially yeast. Here another problem arises: demonstration of biochemical linkages underlying genetic interactions which requires function to be ascribed to genes identified by a gross effect. The challenge is to co-ordinate these two approaches, a strategy currently being employed to further unravel the biological role of GSK-3.
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PMID:Glycogen synthase kinase-3: functions in oncogenesis and development. 133 7

Molecular cloning of glycogen synthase kinase-3 (GSK-3) has demonstrated the existence of a novel form, termed GSK-3 beta, which is highly related to the well characterised GSK-3 alpha protein but derived from a distinct gene. The cDNA cloning also revealed a striking degree of amino acid identity between the two GSK-3 proteins, particularly the beta-form, and the zeste-white3/shaggy (zw3sgg) homeotic gene of Drosophila melanogaster. Abrogation of zw3sgg causes pleiotropic effects on fruitfly development affecting segmental organisation and cell fate determination. In view of the potential importance of GSK-3 beta in mammalian development and the lack of previous characterisation, we have expressed this protein in insect cells using recombinant baculovirus. A rapid purification scheme has been developed yielding essentially pure GSK-3 beta protein in three chromatographic steps. The protein has autonomous protein kinase activity and similar, but not identical, substrate preferences to GSK-3 alpha. Both GSK-3 proteins activate the MgATP-dependent form of protein phosphatase-1 and thus display 'factor A' activity. Since GSK-3 beta exhibits an identical site specificity to GSK-3 alpha with respect to phosphorylation of the proto-oncogene/transcription factors c-jun and c-myc, it is likely that the Drosophila zw3sgg protein kinase has a similar specificity for such transcription factors which may underlie the pleiotropic phenotypes observed when the Drosophila homologue is mutationally inactivated.
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PMID:Baculovirus-mediated expression and characterisation of rat glycogen synthase kinase-3 beta, the mammalian homologue of the Drosophila melanogaster zeste-white 3sgg homeotic gene product. 134 4

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

A highly purified preparation of protein kinase FA (where FA is the activating factor for phosphatase 1)/glycogen synthase kinase 3 from rabbit muscle readily phosphorylated bovine neurofilaments. All three neurofilament proteins, the high, middle, and low molecular proteins (NF-H, NF-M, and NF-L), were phosphorylated when intact filaments were incubated with the kinase. Experiments with individual proteins showed that NF-M was the best substrate. At protein concentrations of 0.13 mg/ml, the initial rate of NF-M phosphorylation was 30% of that observed for glycogen synthase. Km values were 0.24 mg/ml (7 x 10(-7) M tetramer) for glycogen synthase and 0.10 mg/ml (5 x 10(-7) M dimer) for NF-M. Vmax values were 0.36 mumol/min/mg for glycogen synthase and 0.035 mumol/min/mg for NF-M. Dephosphorylated NF-M was phosphorylated only half as much as native NF-M; this is consistent with the known substrate specificity of the kinase. The possible involvement of FA/GSK-3 in the phosphorylation of neurofilaments in vivo is discussed.
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PMID:Phosphorylation of bovine neurofilament proteins by protein kinase FA (glycogen synthase kinase 3). 185 Jul 42

The cDNA encoding the catalytic subunit (C alpha) from mouse cAMP-dependent protein kinase (PK) was expressed in Saccharomyces cerevisiae. By a plasmid swap procedure, we demonstrated that the mammalian C alpha subunit can functionally replace its yeast homolog to maintain the viability of a yeast strain containing genetic disruptions of the three TPK genes encoding the yeast C subunits. C alpha subunit produced in yeast was purified and its biochemical properties were determined. The protein isolated from yeast appears to be myristylated, as has been found for C subunits from higher eukaryotic cells. This system would be useful for studying the biochemistry of the mammalian enzyme in vitro and its biological role in a model in vivo system. These studies demonstrate that the PK substrate(s) required for viability are recognized by the mammalian enzyme. In general terms, these results demonstrate that heterologous proteins with only 50% sequence conservation with their yeast counterparts can be functional in yeast. This is an important result because it validates the use of yeast to identify the biological role of newly cloned genes from heterologous systems, a key tenet of the Human Genome Initiative.
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PMID:Mammalian cAMP-dependent protein kinase functionally replaces its homolog in yeast. 202 31

Recognition of substrates by the protein kinase glycogen synthase kinase 3 (GSK-3) usually requires prior phosphorylation of the substrate. Using a peptide based on the glycogen synthase sequence PRPAS(3a)VPPS (3b)PSLS(3c)RHSS(4)PHQS(5)EDEEEP (where the numbers in parentheses denote sites of phosphorylation), we showed previously that phosphorylation of site 5 by casein kinase II was necessary for GSK-3 to phosphorylate the peptide at sites 3a, 3b, 3c, and 4 (Fiol, C. J., Mahrenholz, A. M., Wang, Y., Roeske, R. W., and Roach, P. J. (1987) J. Biol. Chem. 262, 14042-14048). In the present study, variant peptides were synthesized in which sites 3a, 3b, 3c, and 4 were individually replaced by Ala residues (denoted Ala-3c, etc.). All of the variant peptides were substrates for casein kinase II. The peptide Ala-4,Ser(P)-5 was not a substrate for GSK-3 confirming the minimal recognition sequence for the protein kinase as -SXXXS(P)-. The peptides Ala-3c,Ser(P)-5, Ala-3b,Ser(P)-5, and Ala-3a,Ser(P)-5, however, were all good substrates for GSK-3 with apparent Km values in the range 3-6 microns, comparable with that of the parent peptide. GSK-3 could introduce 1, 2, and 3 phosphates, respectively, into these substrates, always COOH-terminal to the substituted Ala residue. Ala-4,Ser(P)-5 and Ala-3c,Ser(P)-4,Ser(P)-5 were competitive inhibitors for phosphorylation of the parent peptide, with Ki values of 2 and 5 microns, respectively. The data suggest (i) that GSK-3 recognizes serines in the motif -SXXXS(P)-, and (ii) that multiple phosphorylation of the peptide substrate has an obligate order, with the sequential formation of new recognition sequences.
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PMID:Ordered multisite protein phosphorylation. Analysis of glycogen synthase kinase 3 action using model peptide substrates. 215 41

Glycogen synthase kinase-3 (GSK-3) is a protein-serine kinase implicated in the hormonal control of several regulatory proteins including glycogen synthase and the transcription factor c-jun. Two classes of rat brain cDNA for this enzyme have been isolated termed GSK-3 alpha and GSK-3 beta. The alpha-type encodes a 51 kd polypeptide, the sequence of which includes all of the tryptic peptides determined by protein sequence analysis of purified skeletal muscle GSK-3. The novel beta-type cDNA has the potential to encode a 47 kd protein with 85% amino acid identity to GSK-3 alpha. The two types of cDNA are the products of distinct genes as determined by genomic organization and nucleic acid sequence analysis. Both alpha and beta clones exhibit kinase activity when expressed in COS-1 cells and type-specific antibodies to GSK-3 alpha and beta detect proteins of 51 and 47 kd, respectively, in a variety of rat tissue extracts, with highest levels of both in brain. Partial purification of GSK-3 activity from bovine brain results in the isolation of active alpha and beta proteins. The physiological importance of these two proteins in cellular signal transduction is discussed.
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PMID:Molecular cloning and expression of glycogen synthase kinase-3/factor A. 216 70

Addition of glucose or related fermentable sugars to derepressed cells of the yeast Saccharomyces cerevisiae triggers a RAS-mediated cyclic AMP (cAMP) signal that induces a protein phosphorylation cascade. In yeast mutants (tpk1w1, tpk2w1, and tpk3w1) containing reduced activity of cAMP-dependent protein kinase, fermentable sugars, as opposed to nonfermentable carbon sources, induced a permanent hyperaccumulation of cAMP. This finding confirms previous conclusions that fermentable sugars are specific stimulators of cAMP synthesis in yeast cells. Despite the huge cAMP levels present in these mutants, deletion of the gene (BCY1) coding for the regulatory subunit of cAMP-dependent protein kinase severely reduced hyperaccumulation of cAMP. Glucose-induced hyperaccumulation of cAMP was also observed in exponential-phase glucose-grown cells of the tpklw1 and tpk2w1 strains but not the tpk3w1 strain even though addition of glucose to glucose-repressed wild-type cells did not induce a cAMP signal. Investigation of mitochondrial respiration by in vivo 31P nuclear magnetic resonance spectroscopy showed the tpk1w1 and tpk2w1 strains, to be defective in glucose repression. These results are consistent with the idea that the signal transmission pathway from glucose to adenyl cyclase contains a glucose-repressible protein. They also show that a certain level of cAMP-dependent protein phosphorylation is required for glucose repression. Investigation of the glucose-induced cAMP signal and glucose-induced activation of trehalase in derepressed cells of strains containing only one of the wild-type TPK genes indicates that the transient nature of the cAMP signal is due to feedback inhibition by cAMP-dependent protein kinase.
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PMID:Glucose-induced hyperaccumulation of cyclic AMP and defective glucose repression in yeast strains with reduced activity of cyclic AMP-dependent protein kinase. 220 93

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


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