Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A purified bovine lung cGMP-binding cGMP-specific phosphodiesterase (cG-BPDE) was rapidly phosphorylated by purified bovine lung cGMP-dependent protein kinase (cGK). Within a physiological concentration range, cGK catalyzed phosphorylation of cG-BPDE at a rate approximately 10 times greater than did equimolar concentrations of purified catalytic subunit of cAMP-dependent protein kinase (cAK). cG-BPDE was a poor substrate for either purified protein kinase C or Ca2+/calmodulin-dependent protein kinase II. Binding of cGMP to the cG-BPDE binding site was required for phosphorylation since (a) phosphorylation of cG-BPDE by the catalytic subunit of cAK was cGMP-dependent, (b) phosphorylation of cG-BPDE in the presence of a cGMP analog specific for activation of cGK was cGMP-dependent, and (c) occupation of the cG-BPDE hydrolytic site with competitive inhibitors did not produce the cGMP-dependent effect. cGMP-dependent phosphorylation of cG-BPDE by both cGK and cAK occurred at serine. Proteolytic digestion of cG-BPDE phosphorylated by either cGK or cAK revealed the same phosphopeptide pattern, suggesting that phosphorylation by the two kinases occurred at the same or adjacent site(s). Tryptic digestion of cG-BPDE phosphorylated by cGK and [gamma-32P]ATP produced a single major phosphopeptide of approximately 2 kDa with the following amino-terminal sequence: Lys-Ile-Ser-Ala-Ser-Glu-Phe-Asp-Arg-Pro-Leu-Arg- Radioactivity was released during the third cycle of Edman degradation. cG-BPDE is one of few specific in vitro cGK substrates of known function to be identified. Elevation of intracellular cGMP may cause phosphorylation of cG-BPDE by modulating the substrate site availability as well as by activating cGK. Such regulation would greatly increase the selectivity of the phosphorylation of cG-BPDE and would represent a unique mechanism of action of a cyclic nucleotide or other second messenger.
J Biol Chem 1990 Sep 05
PMID:Substrate- and kinase-directed regulation of phosphorylation of a cGMP-binding phosphodiesterase by cGMP. 216 96

Phosphorylation of connexin 32, the major liver gap-junction protein, was studied in purified liver gap junctions and in hepatocytes. In isolated gap junctions, connexin 32 was phosphorylated by cAMP-dependent protein kinase (cAMP-PK), by protein kinase C (PKC) and by Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM-PK II). Connexin 26 was not phosphorylated by these three protein kinases. Phosphopeptide mapping of connexin 32 demonstrated that cAMP-PK and PKC primarily phosphorylated a seryl residue in a peptide termed peptide 1. PKC also phosphorylated seryl residues in additional peptides. CA2+/CaM-PK II phosphorylated serine and to a lesser extent, threonine, at sites different from those phosphorylated by the other two protein kinases. A synthetic peptide PSRKGSGFGHRL-amine (residues 228-239 based on the deduced amino acid sequence of rat connexin 32) was phosphorylated by cAMP-PK and by PKC, with kinetic properties being similar to those for other physiological substrates phosphorylated by these enzymes. Ca2+/CaM-PK II did not phosphorylate the peptide. Phosphopeptide mapping and amino acid sequencing of the phosphorylated synthetic peptide indicated that Ser233 of connexin 32 was present in peptide 1 and was phosphorylated by cAMP-PK or by PKC. In hepatocytes labeled with [32P]orthophosphoric acid, treatment with forskolin or 20-deoxy-20-oxophorbol 12,13-dibutyrate (PDBt) resulted in increased 32P-incorporation into connexin 32. Phosphopeptide mapping and phosphoamino acid analysis showed that a seryl residue in peptide 1 was most prominently phosphorylated under basal conditions. Treatment with forskolin or PDBt stimulated the phosphorylation of peptide 1. PDBt treatment also increased the phosphorylation of seryl residues in several other peptides. PDBt did not affect the cAMP-PK activity in hepatocytes. It has previously been shown that phorbol ester reduces dye coupling in several cell types, however in rat hepatocytes, dye coupling was not reduced by treatment with PDBt. Thus, activation of PKC may have differential effects on junctional permeability in different cell types; one source of this variability may be differences in the sites of phosphorylation in different gap-junction proteins.
Eur J Biochem 1990 Sep 11
PMID:Phosphorylation of connexin 32, a hepatocyte gap-junction protein, by cAMP-dependent protein kinase, protein kinase C and Ca2+/calmodulin-dependent protein kinase II. 217 Jan 22

The whole-cell voltage-clamp technique was employed to study the beta-adrenergic modulation of voltage-gated K+ currents in CD8+ human peripheral blood lymphocytes. The beta-receptor agonist, isoproterenol, decreased the peak current amplitude and increased the rate of inactivation of the delayed rectifier K+ current. In addition, isoproterenol decreased the voltage dependence of steady-state inactivation and shifted the steady-state inactivation curve to the left. Isoproterenol, on the other hand, had no significant effect on the steady-state parameters of current activation. The isoproterenol-induced decrease in peak current amplitude was inhibited by the beta-blocker propranolol. Bath application of dibutyryl cAMP (1 mM) mimicked the effects of isoproterenol on both K+ current amplitude and time course of inactivation. Furthermore, the reduction in the peak current amplitude in response to isoproterenol was attenuated when PKI5-24 (2-5 microM), a synthetic peptide inhibitor of cAMP-dependent protein kinase, was present in the pipette solution. The increase in the rate of inactivation of the K+ currents in response to isoproterenol was mimicked by the internal application of GTP-gamma-S (300 microM) and by exposure of the cell to cholera toxin (1 microgram/ml), suggesting the involvement of a G protein. These results demonstrate that the voltage-dependent K+ conductance in T lymphocytes can be modulated by beta-adrenergic stimulation. The effects of beta-agonists, i.e., isoproterenol, appear to be receptor mediated and could involve cAMP-dependent protein kinase as well as G proteins. Since inhibition of the delayed rectifier K+ current has been found to decrease the proliferative response in T lymphocytes, the beta-adrenergic modulation of K+ current may well serve as a feedback control mechanism limiting the extent of cellular proliferation.
J Membr Biol 1990 Sep
PMID:Beta-adrenergic modulation of K+ current in human T lymphocytes. 217 47

Cloned muscarinic acetylcholine m1 and m2 receptors were expressed in stably transfected mouse Y1 adrenal cells and in a variant Y1 line, Kin-8, which is deficient in cAMP-dependent protein kinase activity (PKA-). m1 and m2 receptors were rapidly internalized following exposure of transfected PKA+ or PKA- cells to the muscarinic agonist carbachol. Thus, agonist-dependent internalization of m1 and m2 did not require PKA activity. A differential effect of PKA on regulation by agonist of the m2 receptor, but not the m1 receptor, was unmasked in PKA- cells. The m2 receptor was more sensitive to agonist-dependent internalization, and its rate of internalization was faster in PKA- cells than it was in PKA+ cells. Treatment of PKA+ cells with 8-(4-chlorophenylthio)-cAMP or forskolin did not result in internalization of either m1 or m2 receptors and did not alter the extent of agonist-dependent internalization of m2. These data indicate that the basal activity of PKA may modulate the agonist-dependent internalization of the m2 receptor, but not the m1 receptor. The internalization of the m1 and m2 receptors in both PKA+ and PKA- cells was accompanied by desensitization of functional responses. Exposure of PKA+ cells to 10(-7) M phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, resulted in a 30 +/- 9% decrease in the number of m1 receptors on the cell surface. However, treatment of PKA- cells expressing the m1 receptor did not result in internalization, suggesting that PKA was required for some aspect of PMA-dependent internalization.(ABSTRACT TRUNCATED AT 250 WORDS)
Biochemistry 1990 Sep 11
PMID:Differential regulation by agonist and phorbol ester of cloned m1 and m2 muscarinic acetylcholine receptors in mouse Y1 adrenal cells and in Y1 cells deficient in cAMP-dependent protein kinase. 217 2

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.
Mol Cell Biol 1990 Sep
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

The resolving power of liquid chromatography systems containing 1-pentane sulfonate, previously used to analyze basic hydrophilic peptides related to substrates of cAMP-dependent protein kinase, has been studied with respect to diastereomeric peptides. A set of peptides comprising RRASV and its five diastereomers containing one D-amino acid were used as model compounds. Complete resolution of all the peptides could be accomplished both with ethanol and acetonitrile as organic modifiers. The separation of the various peptides within the set turned out to be only modestly changed under the conditions investigated. These new results clearly demonstrate the potential of the chromatography systems studied.
Int J Pept Protein Res 1990 Sep
PMID:Separation of a complete set of basic, diastereomeric pentapeptides by reversed-phase ion-pair chromatography. 227 54

The present studies examine the effects of in vivo and in situ progesterone treatment in the regulation of site-specific phosphorylation of the chicken oviduct progesterone receptor (PR). By gas-phase protein sequencing we have identified three hormonally regulated phosphorylation sites: Ser-211, Ser-260, and Ser-530. We determined phosphorylation stoichiometries by analyzing the amounts of phosphorylated and dephosphorylated serine at each site. Stoichiometries of sites 211 and 260 were about 20% under basal conditions and increased 1.5-2-fold by in situ progesterone treatment. Site 530 was virtually absent under basal conditions and induced to greater than 33% by in situ progesterone treatment. We tested several protein kinases for phosphorylation of the PR in vitro on these sites or peptides containing these sites. We found that the catalytic subunit of cAMP-dependent protein kinase mimicked the in vivo, hormone-induced altered mobility of PRs in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both the in vivo and in vitro alterations were reversed by alkaline phosphatase. Finally, we showed that cAMP-dependent protein kinase phosphorylated Ser-528.
J Biol Chem 1990 Sep 25
PMID:Hormonal regulation and identification of chicken progesterone receptor phosphorylation sites. 239 63

The phosphoform of the type II regulatory subunit (phospho-RII-cAMP) of cAMP-dependent protein kinase from rat liver was found to possess intrinsic topoisomerase activity towards several DNA substrates such as phi X174, pBR322, SV40, and M13. Like the type I topoisomerases from several eukaryotic cells, phospho-RII X cAMP can relax both positive and negative superhelical turns of phi X174 DNA. Topological isomers with a decreasing number of superhelical turns can be identified as transient products. Conditions under which phospho-RII X cAMP relaxes superhelical phi X174 DNA lead to transient formation of a DNA-phospho-RII X cAMP complex via DNA strand breakage and covalent attachment of the DNA to a tyrosine residue of phospho-RII X cAMP via a phospho-RII X cAMP depends on the presence of cAMP and is altered by changes in the degree of phosphorylation of RII. Both dephosphorylation and removal of cAMP from phospho-RII X cAMP abolish its topoisomerase activity.
Cell 1985 Sep
PMID:The phosphoform of the regulatory subunit RII of cyclic AMP-dependent protein kinase possesses intrinsic topoisomerase activity. 241 19

Effects of glucagon and forskolin on the phosphorylation and changes of activity of carnitine palmitoyltransferase (CPT) have been studied in isolated rat hepatocytes using anti-CPT immunoglobulin. When the activity was determined in lysed hepatocytes after glucagon or forskolin treatment, it was found to be stimulated 30-80% mainly through increased affinity for palmitoyl-CoA. By SDS electrophoresis of the immunoprecipitates, CPT subunit (Mr 69000) was noted to be phosphorylated 4-5-fold with glucagon (1.2 X 10(-7) M) and forskolin (0.1 mM) over control. These results indicate that hepatic ketogenesis is regulated with glucagon by phosphorylation of CPT through cAMP-dependent protein kinase.
FEBS Lett 1985 Sep 02
PMID:Phosphorylation of carnitine palmitoyltransferase and activation by glucagon in isolated rat hepatocytes. 241 97

P19, a group of 19,000 mol wt cytosolic proteins, with apparent isoelectric points of pI 5.9, pI 5.7, and pI 5.4, respectively, was identified in three peptide hormone-producing cell types: AtT20 mouse pituitary tumor cells, RIN-1122 rat insulinoma cells, and hamster insulinoma cells. Secretagogue-dependent phosphorylation of P19 was analyzed in 32P-labeled cells by two-dimensional electrophoresis and autoradiography. The results were quantitated by computer-assisted densitometry. Cellular levels of cAMP and hormone release were measured in parallel incubations. In addition to stimulating ACTH release, CRF raised the cellular level of cAMP and increased the 32P labeling of all three 19,000 mol wt proteins in AtT20 cells. Other agents known to act through cAMP, which included isoproterenol, forskolin, and 8-bromo-cAMP, mimicked the effect of CRF on both ACTH release and phosphorylation of P19. 12-O-Tetra-decanoylphorbol-13-acetate, a tumor-promoting phorbol ester, also stimulated both ACTH release and phosphorylation of P19. In contrast, although 40 mM K+ promoted ACTH release, it did not affect the phosphorylation of P19. Analogous findings were observed in insulinoma cells. Glucagon stimulated insulin release, increased cellular cAMP and promoted phosphorylation of P19 in RIN 1122 cells. 12-O-Tetradecanoylphorbol-13-acetate also enhanced insulin release and the phosphorylation of P19 in these cells. The results obtained with hamster insulinoma cells closely resembled the observations in RIN-1122 cells. In conclusion, P19, an apparently homologous set of cytosolic proteins, undergoes phosphorylation in three peptide hormone-producing cells in response to two groups of secretagogues, the effect of which is probably mediated, in one case, by cAMP-dependent protein kinase and, in the other, by protein kinase C. The data suggest the possibility that P19 participates in a secretory pathway activated by these two effector systems.
Endocrinology 1986 Sep
PMID:P19, a hormonally regulated phosphoprotein of peptide hormone-producing cells: secretagogue-induced phosphorylation in AtT-20 mouse pituitary tumor cells and in rat and hamster insulinoma cells. 242 97


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