Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Angiotensin II, catecholamines, and vasopressin can stimulate the phosphorylation of 10 hepatic cytosolic proteins via a Ca2+-linked, cyclic AMP-independent mechanism. To explore the role of known Ca2+-sensitive protein kinases in this response, [32P]PO4(3-)-labeled hepatocytes were stimulated with various agonists, the cytoplasmic proteins were separated on two-dimensional gels, and the resulting autoradiographs were computer analyzed. The role of phosphorylase kinase was examined using hepatocytes from gsd/gsd rats which are deficient in this enzyme. The phosphorylation state of phosphorylase was not increased by glucagon, angiotensin II, or vasopressin in hepatocytes from the gsd/gsd animals. The phosphorylation state of all other substrates was changed by glucagon or the Ca2+-linked hormones to the same extent in gsd/gsd hepatocytes as in normal Wistar controls, suggesting that phosphorylase kinase plays a restricted role in the hormone response. The role of the Ca2+- and phospholipid-sensitive protein kinase (protein kinase C) was examined by stimulating hepatocytes with phorbol esters which are thought to activate protein kinase C by substituting for diacylglycerol. Phorbol esters increased the phosphorylation state of 3 of the 10 substrates affected by angiotensin II or vasopressin, but did not stimulate Ca2+ fluxes in hepatocytes. Treatment of hepatocytes with the Ca2+ ionophore A23187 mimicked the effect of the Ca2+-linked hormones on the phosphorylation of the other 7 substrates. The results demonstrate that at least three Ca2+-sensitive protein kinases are involved in the response of hepatocytes to Ca2+-linked hormones. Since these kinases can be activated independently by phorbol esters or A23187, the results imply that hormones such as vasopressin generate two intracellular messengers, diacylglycerol and Ca2+ ion.
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PMID:Evidence for the role of phosphorylase kinase, protein kinase C, and other Ca2+-sensitive protein kinases in the response of hepatocytes to angiotensin II and vasopressin. 623 Mar 57

Isolated rat hepatocytes were incubated in a medium containing 0.1 mM [32P]phosphate (0.1 mCi/ml) before exposure to epinephrine, glucagon or vasopressin. 32P-labeled glycogen synthase was purified from extracts of control or hormone-treated cells by the use of specific antibodies raised to rabbit skeletal muscle glycogen synthase. Analysis of the immunoprecipitates by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicated that a single 32P-labeled polypeptide, apparent Mr 88000, was removed specifically by the antibodies and corresponded to glycogen synthase. Similar electrophoretic analysis of CNBr fragments prepared from the immunoprecipitate revealed that 32P was distributed between two fragments, of apparent Mr 14000 (CB-1) and 28000 (CB-2). Epinephrine, vasopressin or glucagon increased the 32P content of the glycogen synthase subunit. CB-2 phosphorylation was increased by all three hormones while CB-1 was most affected by epinephrine and vasopressin. These effects correlated with a decrease in glycogen synthase activity. From studies using rat liver glycogen synthase, purified by conventional methods and phosphorylated in vitro by individual protein kinases, it was found that electrophoretically similar CNBr fragments could be obtained. However, neither cyclic-AMP-dependent protein kinase nor three different Ca2+-dependent enzymes (phosphorylase kinase, calmodulin-dependent protein kinase, and protein kinase C) were effective in phosphorylating CB-2. The protein kinases most effective towards CB-2 were the Ca2+ and cyclic-nucleotide-independent enzymes casein kinase II (PC0.7) and FA/GSK-3. The results demonstrate that rat liver glycogen synthase undergoes multiple phosphorylation in whole cells and that stimulation of cells by glycogenolytic hormones can modify the phosphorylation of at least two distinct sites in the enzyme. The specificity of the hormones, however, cannot be explained simply by the direct action of any known protein kinase dependent on cyclic nucleotide or Ca2+. Therefore, either control of other protein kinases, such as FA/GSK-3, is involved or phosphatase activity is regulated, or both.
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PMID:Control of glycogen synthase phosphorylation in isolated rat hepatocytes by epinephrine, vasopressin and glucagon. 643 31

Recently, we reported that curcumin (diferuloylmethane) inhibits the growth of several different kinds of tumor cells. In order to investigate the mechanism of this inhibition, we examined the effects of curcumin on different protein kinases: highly purified protein kinase A (PkA), protein kinase C (PkC), protamine kinase (cPK), phosphorylase kinase (PhK), autophosphorylation-activated protein kinase (AK) and pp60c-src tyrosine kinase. While all kinases tested were inhibited by curcumin, only PhK was completely inhibited at relatively lower concentrations. At around 0.1 mM curcumin, PhK, pp60c-src, PkC, PkA, AK, and cPK were inhibited by 98%, 40%, 15%, 10%, 1%, and 0.5%, respectively. Lineweaver-Burk plot analysis indicated that curcumin is a non-competitive inhibitor of PhK with a Ki of 0.075 mM. Overall, our results indicate that curcumin is a potent and selective inhibitor of phosphorylase kinase, a key regulatory enzyme involved in the metabolism of glycogen. This has important implications for the anti-proliferative effects of curcumin.
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PMID:Curcumin is a non-competitive and selective inhibitor of phosphorylase kinase. 751 Nov 11

The regulation of cardiac muscle glycogen metabolism is not well understood. Previous studies have indicated that heart glycogen synthase is heavily phosphorylated in vivo on multiple sites. Using purified enzymes, we have investigated the effect of phosphorylation of different sites on the activity of rat heart glycogen synthase. A convenient procedure was developed for the purification of rat heart glycogen synthase. The enzyme was phosphorylated by selected kinases, and glycogen synthase activity, extent of phosphorylation, and phosphopeptide maps were analyzed. Rat heart glycogen synthase, purified to apparent homogeneity (M(r) 87,000 on SDS-PAGE), had a specific activity of 18 U/mg protein and had an activity ratio of 0.74 (activity in the absence divided by the activity in the presence of glucose 6-P). cAMP-dependent protein kinase, glycogen synthase kinase 3, Ca2+/calmodulin-dependent protein kinase II, protein kinase C, and phosphorylase kinase phosphorylated the enzyme with a concomitant decrease in the activity ratio to values ranging from 0.1 to 0.4. Casein kinase II phosphorylated but did not inactivate glycogen synthase. Six tryptic phosphopeptides, obtained from heart glycogen synthase phosphorylated by the various kinases, were separated by reverse-phase chromatography. The phosphopeptide(s) obtained with each kinase eluted at the same position(s) as corresponding phosphopeptides obtained from rat skeletal muscle glycogen synthase. The study shows that the pattern of phosphorylation and effects on activity are very similar for cardiac and skeletal muscle glycogen synthase. It is suggested that the well known differences in heart and glycogen metabolism may be due to the interplay of kinases and phosphatases which could lead to different phosphorylation and activity states of glycogen synthase.
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PMID:Phosphorylation and inactivation of rat heart glycogen synthase by cAMP-dependent and cAMP-independent protein kinases. 767 Nov 34

Pentosan polysulfate, a polyanionic mucopolysaccharide, which has been shown to exert inhibitory effects on human immunodeficiency virus (HIV-I) replication, inhibited the activities of protein tyrosine kinases from lymphocytes (Jurkat cells) and rat lung in a concentration dependent manner. In addition, the autophosphorylation of p56lck, a lymphocyte associated protein tyrosine kinase from Jurkat cells was also inhibited by pentosan polysulfate (100 micrograms/ml). Furthermore, the activities of protein serine/threonine kinases such as Ca2+, phospholipid-dependent protein kinase (protein kinase C) from human platelets and the catalytic subunit of cAMP-dependent protein kinase from skeletal muscle were also inhibited by this mucopolysaccharide. However, the activity of phosphorylase kinase was not altered. The inhibition of rat lung protein tyrosine kinase was rapid and competitive with respect to ATP with an apparent Ki value of 5-20 micrograms/ml. These results suggest that the ability of pentosan polysulfate to inhibit various protein serine/threonine and tyrosine kinases may be one of the mechanisms by which this compound exerts its inhibitory effect of HIV-I replication.
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PMID:Pentosan polysulfate, a potent anti HIV and anti tumor agent, inhibits protein serine/threonine and tyrosine kinases. 768 45

Calcium- and lipid-dependent protein kinase (PKC) activity in the ovary of the pseudopregnant rat is masked by an endogenous inhibitor of PKC. These studies were undertaken to examine the mechanism of action of the endogenous inhibitor of PKC in the rat ovary. The addition of the phosphatase inhibitors calyculin-A (0.09 nM), microcystin-LR (6.4 nM), and okadaic acid (10 nM) resulted in the loss of PKC inhibitory activity and an increase in basal PKC activity in rat ovarian cytosol. In phosphatase assays, significant dephosphorylation of histone-III-S or myelin basic protein that had been phosphorylated by PKC occurred within 4 min after the addition of ovarian cytosol from the pseudopregnant rat. This dephosphorylation was prevented from the pseudopregnant rat. This dephosphorylation was prevented by the addition of calyculin-A (0.73 nM) and was removed by fractionation of ovarian cytosol on diethylaminoethyl cellulose. No inhibition of PKC activity was observed when the PKC-specific peptides AcMBP-(4-14) and [Ser25]PKC-(19-31) were used as the substrate for phosphorylation. In addition, rat ovarian cytosol did not exhibit phosphatase activity when the peptide AcMBP-(4-14) was used as the substrate. Addition of ovarian cytosol resulted in dephosphorylation of phosphorylase-alpha phosphorylated by phosphorylase kinase, but not dephosphorylation of histone-II-A or histone-VIII-S phosphorylated by PKA. The data suggest that the endogenous inhibitor of PKC in the rat ovary is a protein phosphatase.
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PMID:The endogenous inhibitor of protein kinase-C in the rat ovary is a protein phosphatase. 768 49

Microtubule-associated protein tau from Alzheimer brain has been shown to be phosphorylated at several ser/thr-pro and ser/thr-X sites (Hasegawa, M. et al., J. Biol. Chem. 267, 17047-17054, 1992). Several proline-dependent protein kinases (PDPKs) (MAP kinase, cdc2 kinase, glycogen synthase kinase-3, tubulin-activated protein kinase, and 40 kDa neurofilament kinase) are implicated in the phosphorylation of the ser-thr-pro sites. The identity of the kinase(s) that phosphorylate the ser/thr-X sites are unknown. To identify the latter kinase(s) we have compared the phosphorylation of bovine tau by several brain protein kinases. Stoichiometric phosphorylation of tau was achieved by casein kinase-1, calmodulin-dependent protein kinase II, Gr kinase, protein kinase C and cyclic AMP-dependent protein kinase, but not with casein kinase-2 or phosphorylase kinase. Casein kinase-1 and calmodulin-dependent protein kinase II were the best tau kinases, with greater than 4 mol and 3 mol 32P incorporated, respectively, into each mol of tau. With the sequential addition of these two kinases, 32P incorporation approached 6 mol. Peptide mapping revealed that the different kinases largely phosphorylate different sites on tau. After phosphorylation by casein kinase-1, calmodulin-dependent protein kinase II, Gr kinase, cyclic AMP-dependent protein kinase and casein kinase-2, the mobility of tau isoforms as detected by SDS-PAGE was decreased. Protein kinase C phosphorylation did not produce such a mobility shift. Our results suggest that one or more of the kinases studied here may participate in the hyperphosphorylation of tau in Alzheimer disease.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of the phosphorylation of microtubule-associated protein tau by non-proline dependent protein kinases. 803 84

Neuronal tissue-specific proteins B-50 (GAP-43, neuromodulin) and neurogranin are phosphorylated by phosphorylase kinase with stoichiometries of 0.4 and 0.5 mol of phosphate/mol of protein, respectively. The apparent Km and kcat values determined at pH 8.2 for neurogranin phosphorylation are 28.4 microM and 139.3 min-1, respectively, and for B-50 phosphorylation are 22.8 microM and 33.2 min-1, respectively. As a substrate of phosphorylase kinase, phosphorylase is approximately 44 and approximately 13 times better than B-50 and neurogranin, respectively. Both proteins are better substrates of protein kinase C than of phosphorylase kinase and are phosphorylated on a single site by phosphorylase kinase. The sequence analyses of tryptic phosphopeptides isolated from neurogranin and B-50 phosphorylated by phosphorylase kinase revealed the same amino acid sequence, IQASF, indicating that phosphorylase kinase phosphorylates the calmodulin-binding regulatory regions of B-50 and neurogranin previously known to be phosphorylated by protein kinase C (Coggins, P. J., and Zwiers, H. (1989) J. Neurochem. 53, 1895-1901; Baudier, J., Deloulme, J. C., Dorsselaer, A. V., Black, D., and Matthes, W. D. (1991) J. Biol. Chem. 266, 229-237). In rat brain synaptosomes, a relatively high phosphorylase kinase specific activity is detected, and approximately 32% activity is associated with synaptic membranes where B-50 is localized. In rat brain homogenate and synaptosomal membranes, phosphorylation of a protein that co-migrates with B-50 on SDS-polyacrylamide gel electrophoresis is enhanced in the presence of exogenous phosphorylase kinase.
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PMID:Phosphorylase kinase phosphorylates the calmodulin-binding regulatory regions of neuronal tissue-specific proteins B-50 (GAP-43) and neurogranin. 845 96

B-50/GAP-43 is a growth-associated phosphoprotein enriched in growth cones and in the presynaptic terminal. The expression of the protein is restricted to the nervous system and is highest in the first week after birth. In adult brain, B-50 is enriched in areas with high plasticity. The regulation of expression of the B-50 gene occurs both at the transcriptional and post-transcriptional level by unknown mechanisms. The gene contains 2 regions displaying promoter activity, the most 3' of which (P2) is the active on in vivo. Expression of B-50 in non-neuronal cells results in filopodial extensions whereas antibodies or antisense oligo's to B-50 prevent neurite outgrowth. The protein is important for neuronal pathfinding. Several post-translational modifications have been described, ADP-ribosylation and palmitoylation in the membrane binding domain, phosphorylation by PKC, casein kinase II and phosphorylase kinase, and dephosphorylation by several phosphatases, among which is calcineurin. Interactions of B-50 have been described with calmodulin, PIP kinase, F-actin, and phospholipids. Recent studies indicate that the phosphorylation state and amount of calmodulin bound to B-50 regulate the rate of transmitter release. Induction of long-term potentiation by high frequency stimulation of hippocampal slices results in an increased state of B-50 phosphorylation. This will increase the amount of free calmodulin in the presynaptic terminal and increase the amount of transmitter released. Although B-50 is involved in seemingly unrelated forms of neuronal plasticity, neurite outgrowth and transmitter release, our unifying hypothesis is that the protein plays an (unknown) essential, modulatory role in membrane expansion.
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PMID:Presynaptic phosphoprotein B-50/GAP-43 in neuronal and synaptic plasticity. 886 78

Since protein kinase C (PKC) serves as a receptor for phorbol ester type tumor promoters and oxidants and has unique redox-active cysteine-rich regions, we have determined whether various chemopreventive selenocompounds could affect this enzyme. At lower concentrations, selenite decreased the kinase activity (IC50 = 0.5 microM), while at higher concentrations it decreased phorbol ester binding. However, when the catalytic and regulatory domains of PKC were separated by proteolysis, the catalytic domain retained its sensitivity to selenite, while the regulatory domain lost its sensitivity. Cysteine residues were quantitated in PKC modified with selenite by using 5,5'-dithiobis(2-nitrobenzoic acid) and also by using 2-nitro-5-thiosulfobenzoic acid after sulfitolysis. At lower concentrations, selenite induced a modification of four cysteine residues resulting in the formation of two disulfides, while at higher concentrations it induced a modification of seven to eight cysteine residues resulting in the formation of three to four disulfides. Contrary to selenite, selenocystine and selenodiglutathione (GSSeSG) readily inactivated the kinase activity, but not the phorbol ester binding. These two agents induced a two-stage modification of PKC; a limited modification at low concentrations leads to a loss of affinity for ATP, while an excessive modification at high concentrations leads to a loss of Vmax. Selenocystine and GSSeSG were 100,000-fold more potent than GSSG in inactivating PKC. The isoenzymes alpha, beta, and gamma exhibited an identical susceptibility to these selenocompounds. These results suggested that the cysteine residues present within the catalytic domain of these isoenzymes, although apart in the sequence, may be clustered in the tertiary structure to react with selenite, as well as may be in close proximity to some of the cysteines in the regulatory domain. Selenite did not affect protein kinase A, whereas GSSeSG and selenocystine inactivated the catalytic subunit after dissociation from the regulatory subunit at concentrations 100- and 800-fold, respectively, higher than that required for PKC inactivation. All three selenocompounds did not affect the activities of phosphorylase kinase and protein phosphatase 2A. Taken together, these results suggest that the accessible redox-active cysteine residues present in the PKC catalytic domain can react with certain specificity with redox-active selenocompounds such as selenite, selenocystine, and GSSeSG relative to other protein kinases tested.
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PMID:Cancer-preventive selenocompounds induce a specific redox modification of cysteine-rich regions in Ca(2+)-dependent isoenzymes of protein kinase C. 939 Jan 71


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