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

Protein kinase C catalyzes phosphorylation of the rat skeletal muscle AMP-deaminase in the presence of calcium ions and phosphatidylserine. At the same time, the catalytic subunit of cAMP-dependent protein kinase fails to phosphorylate AMP-deaminase. Ca2+, phosphatidylserine-dependent phosphorylation decreases three-fold (from 0.6 to 0.2 mM) the Km value and does not affect Vmax. Protein kinase C-induced phosphorylation of AMP-deaminase, besides ADP-ribosylation, is suggested to be involved in regulating the AMP-deaminase activity in vivo.
 ...
PMID:Phosphorylation of the skeletal muscle AMP-deaminase by protein kinase C. 229 22

A cell-free system for the study of transcription from the promoter of the phosphoenolpyruvate carboxykinase (GTP) gene by using nuclear extracts from rat tissues was developed. The level of basal transcription from the phosphoenolpyruvate carboxykinase (PEPCK) promoter between -490 and +73 was highest when extracts from liver nuclei, rather than kidney, spleen, and HeLa nuclear extracts, were used. A series of 5' deletions and block mutations were also tested for their effects on basal transcription in vitro. The promoter truncated to -355 had the highest rate of basal transcription, while subsequent deletion to -277 markedly decreased the rate of transcription. Further deletion of the promoter to -134 resulted in a twofold increase in the basal level of transcription compared with that of the promoter deleted to -277. However, subsequent deletion of the NF-1-CCAAT-binding transcription factor binding site or the proximal cyclic AMP (cAMP) regulatory element caused a decrease in basal transcription. Block mutations were inserted into nine specific protein-binding regions of the PEPCK promoter previously shown to be of functional significance or to bind nuclear proteins. Mutation of the TATA box resulted in a 94% decrease in the level of transcription noted with the intact promoter, while sequence substitutions within the proximal cAMP regulatory element decreased the transcription rate to 25%. The addition of the catalytic subunit of cAMP-dependent protein kinase to the in vitro system stimulated transcription from the intact promoter or from a promoter deletion to -109. However, a promoter deletion to -68, which removes the proximal cAMP regulatory element, was unresponsive to added protein kinase catalytic subunit. These findings indicate that the PEPCK promoter between -490 and +73 contains sequences responsive to hormonal and tissue-specific factors in nuclei from rat tissues. The sensitivity of this in vitro transcription system closely mimics the process regulating PEPCK transcription in rat tissues and should make it ideal for testing the function of purified transcription factors.
 ...
PMID:In vitro analysis of promoter elements regulating transcription of the phosphoenolpyruvate carboxykinase (GTP) gene. 230 49

We have previously reported that the cAMP-specific phosphodiesterase activity in washed rat platelets is increased by a short exposure of platelet suspension to PGE1 and 1-methyl-3-isobutyl-xanthine (MIX). We report here that the incubation of washed platelets with forskolin resulted in an increase in the binding of cGMP and the activity of cGMP-phosphodiesterase as well as that of cAMP-specific phosphodiesterase. As for PGE1, MIX potentiated the stimulatory effect of forskolin. The maximal activation of phosphodiesterases by forskolin and MIX occurred after 30 sec of incubation of platelets (with a slow decline thereafter). The activation of phosphodiesterases in intact platelets by forskolin occurred in parallel with the dissociation of a cAMP-dependent protein kinase. Prior incubation of a platelet supernatant with Mg-ATP and cAMP had only a slight effect on cAMP- or cGMP-phosphodiesterase activities, but the presence of MIX during the prior incubation, followed by appropriate dilution, greatly enhanced the activity of the two phosphodiesterases. The phosphodiesterase activation in vitro was inhibited by a non-hydrolysable analogue of ATP, AMP-PNP. Since the cGMP-binding phosphodiesterase activity is enhanced by the catalytic subunit of cAMP-dependent protein kinase in the presence of MIX and absence of cAMP, the effect of MIX cannot be explained in terms of the protection of cAMP from hydrolysis. It is possible that the xanthine increases the susceptibility of the cAMP-specific and cGMP-binding phosphodiesterases to phosphorylation.
 ...
PMID:Activation of cyclic GMP-binding and cyclic AMP-specific phosphodiesterases of rat platelets by a mechanism involving cyclic AMP-dependent phosphorylation. 241 69

Dose-response relations for the increase in the amplitude of Ca current (ICa) on external application of isoprenaline (ISP) and internally applied cyclic AMP (cAMP) or catalytic subunit of cAMP-dependent protein kinase (C subunit) were established in single ventricular cells of the guinea pig. An intracellular dialysis technique was used. The threshold concentration was for ISP 10(-9) M, for cAMP 3 microM (pipette concentration to which 10(-5) M 3-isobutyl-1-methylxanthine was added) and for C subunit around 0.4 microM (pipette concentration). The concentrations for the half-maximal effect were 3.7 X 10(-8) M (ISP), 5.0 microM (cAMP) and 0.95 microM (C subunit) and for the maximum effect 10(-6) M (ISP), 15-20 microM (cAMP) and 3-4 microM (C subunit). For all three agents the maximum increase in the Ca current density was similar (a factor of 3-4), suggesting that they converge on the same site of the Ca channel. Accordingly, the effects of cAMP and C subunit on ICa were non-additive to those of ISP. From these data the relationship both between concentrations of ISP and cAMP and between those of cAMP and active C subunit in terms of their effects on ICa could be estimated and were compared with those obtained in broken cell preparations. A competitive inhibitor of phosphorylation, 5'-adenylyl-imidodiphosphate (5 mM), greatly reduced the effects of ISP and C subunit on ICa. Cell dialysis with 3 mM adenosine-5'-(gamma-thio)-triphosphate, which produces a dephosphorylation-resistant phosphorylation, markedly potentiated the effects of ISP and cAMP on ICa.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:On the mechanism of beta-adrenergic regulation of the Ca channel in the guinea-pig heart. 241 19

Beta adrenergic receptor-mediated vascular smooth muscle relaxation decreases with increasing age. We have examined the mechanism responsible for this phenomenon using rat mesenteric arteries from young (5-6 weeks) and older (10-12 months) rats. The beta adrenergic agonist isoproterenol produced a dose-dependent relaxation of serotonin-constricted mesenteric artery rings from young rats, whereas the maximal ability of isoproterenol to relax arterial rings from the older rats was found to be reduced markedly (92.7 vs. 27.6%, P less than .0001). The relaxation responses caused by acetylcholine and nitroglycerin, which appear to act independently of cyclic AMP (cAMP), are similar in the two groups. The loss in responsiveness of the mesenteric artery to isoproterenol was not explained by a change in beta receptor number in the vessels (29 +/- 4 in young rats vs. 31 +/- 7 fmol/mg of protein in the older rats). The maximal stimulation of cAMP accumulation by isoproterenol was lower in the older vessels; forskolin activated cAMP accumulation equally in the two groups. However, the vessels from the older rats were less sensitive to forskolin-induced vascular relaxation. Also, the ability of dibutyryl cAMP to promote vascular relaxation was diminished in the older vessels. These data suggest that the diminished cAMP accumulation in older vessels in response to isoproterenol might not necessarily in itself explain completely the reduced physiological response and that an additional defect in the beta adrenergic-mediated relaxation in the vascular smooth muscle of older rats may lie at the level of cAMP-dependent protein kinase activation or more distally.
 ...
PMID:Age-related decrease in beta adrenergic receptor-mediated vascular smooth muscle relaxation. 243 92

The intracellular mechanisms by which cardiac Ca current (ICa) and the delayed outward K current (IK) are modulated during beta-adrenergic or muscarinic stimulation were investigated at the level of both single-channel and whole-cell currents in single ventricular myocytes of guinea-pigs. Superfusion of cells with beta-adrenergic agonist increased the amplitude of whole-cell ICa in a dose-dependent manner. In the single-channel recording, neither the amplitude of elementary current nor the total number of active channels was affected but the number of blank records was markedly reduced resulting in a larger amplitude of the ensemble average current. Intracellular dialysis of cells with cyclic AMP (cAMP) or the catalytic (C) subunit of cAMP-dependent protein kinase (cAMP-PK) produced a dose-dependent increase in the amplitude of ICa and IK. A non-hydrolysable ATP analogue, AMP-PNP, reduced whereas ATP gamma S enhanced the effects of beta-agonist on ICa and IK, suggesting an involvement of protein phosphorylation during the enhancement of these currents. The regulatory subunit of cAMP-PK, the heat-stable protein-kinase inhibitor (PKI) and type-1 protein phosphatase antagonized the beta-adrenergic enhancement of ICa and IK, but did not eliminate ICa. Acetylcholine (ACh) reduced the amplitude of ICa when ICa was enhanced by either beta-adrenergic agonist, forskolin or 3-isobutyl-1-methyl-xanthine but did ACh not when ICa was enhanced by intracellular dialysis with cAMP or C subunit, suggesting that muscarinic inhibition occurs at the level of adenylate cyclase. Non-hydrolysable GTP analogue, GMP-PNP, uncoupled both beta-adrenergic and muscarinic modulation of ICa. Pertussis toxin selectively eliminated the effect of ACh on ICa. Based on these results, we concluded that the activities of the Ca channel and the delayed outward K channel are controlled by the action of neurotransmitters, which are mediated by GTP-binding proteins and cAMP-dependent protein phosphorylation. It is suggested that phosphorylation of 'Ca-channel-related protein' leads to an increased open probability without changing the total number of channels or the elementary current amplitude.
 ...
PMID:Intracellular control of calcium and potassium currents in cardiac cells. 243 80

Chloride impermeability of epithelial cells can account for many of the experimental and clinical manifestations of cystic fibrosis (CF). Activation of apical-membrane Cl- channels by cyclic AMP-mediated stimuli is defective in CF airway epithelial cells, despite normal agonist-induced increases in cellular cAMP levels. This defect in Cl- channel regulation has been localized to the apical membrane by exposing the cytoplasmic surface of excised membrane patches to the catalytic subunit (C subunit) of cAMP-dependent protein kinase and ATP. In membranes from normal cells, C-subunit activated Cl- channels with properties identical to those stimulated by cAMP-dependent agonists during cell-attached recording. Activation by the C subunit was not observed in CF membranes, but the presence of Cl- channels was verified by voltage-induced activation. The failure of the C subunit to activate the Cl- channels of CF membranes indicates that the block in their cAMP-mediated activation lies distal to induction of cAMP-dependent protein kinase activity and focuses our attention on the Cl- channel and its membrane-associated regulatory proteins as the probable site of the CF defect.
 ...
PMID:Phosphorylation fails to activate chloride channels from cystic fibrosis airway cells. 244 2

Chloride (Cl-) secretion by the airway epithelium regulates, in part, the quantity and composition of the respiratory tract fluid, thereby facilitating mucociliary clearance. The rate of Cl- secretion is controlled by apical membrane Cl- channels. Apical Cl- channels are opened and Cl- secretion is stimulated by a variety of hormones and neurotransmitters that increase intracellular levels of cyclic AMP (cAMP). In cystic fibrosis (CF), a common lethal genetic disease of Caucasians, airway, sweat-gland duct, secretory-coil and possibly other epithelia are anion impermeable. This abnormality may explain several of the clinical manifestations of the disease. The Cl- impermeability in CF-airway epithelia has been localized to the apical cell membrane, where regulation of Cl- channels is abnormal: hormonal secretagogues stimulate cAMP accumulation appropriately but Cl- channels fail to open. Here we report that the purified catalytic subunit of cAMP-dependent protein kinase plus ATP opens Cl- channels in excised, cell-free patches of membrane from normal cells, but fails to open Cl- channels in CF cells. These results indicate that in normal cells, the cAMP-dependent protein kinase phosphorylates the Cl- channel or an associated regulatory protein, causing the channel to open. The failure of CF Cl- channels to open suggests a defect either in the channel or in such an associated regulatory protein.
 ...
PMID:Cyclic AMP-dependent protein kinase opens chloride channels in normal but not cystic fibrosis airway epithelium. 244 45

Elevation of cyclic AMP (cAMP) content in perfused rat hearts by exposure to glucagon, forskolin, and 1-methyl-3-isobutylxanthine (IBMX) increased rates of protein synthesis during the second hour of perfusion with buffer that contained glucose in the absence of added insulin. When tetrodotoxin was added to arrest contractile activity, glucagon, forskolin, and IBMX still elevated cAMP content and rates of protein synthesis. Perfusion of beating rat hearts at elevated aortic pressure (120 mm Hg vs. 60 mm Hg) also accelerated rates of protein synthesis and raised cAMP content and cAMP-dependent protein kinase activity during the second hour of perfusion. Insulin accelerated rates of protein synthesis in beating hearts during the first and second hour of perfusion but did not increase cAMP content. Elevation of aortic pressure in insulin-treated hearts raised cAMP content but had no further effect on rates of protein synthesis. Perfusion of arrested hearts for as little as 2 minutes at 120 mm Hg resulted in a rapid and sustained increase in cAMP content, cAMP-dependent protein kinase activity, and rate of protein synthesis after 60-120 minutes of additional perfusion at 60 mm Hg. Exposure of arrested hearts to 0.2 mM methacholine, a muscarinic-cholinergic agonist, for 5 minutes before elevation of perfusion pressure blocked the pressure-induced increases in cAMP content, cAMP-dependent protein kinase activity, and rates of protein synthesis. When hearts were removed from pertussis toxin-treated animals, methacholine did not block the effects of forskolin on these same three parameters. These studies indicated that elevation of tissue cAMP by hormone binding, direct activation of adenylate cyclase, or inhibition of phosphodiesterase resulted in acceleration of protein synthesis. Furthermore, the effects of increased aortic pressure to accelerate synthesis appeared to involve a cAMP-dependent mechanism that was independent of changes in contractile activity but could be blocked with a muscarinic-cholinergic agonist. Acceleration of protein synthesis by insulin was not associated with an elevation of cAMP.
 ...
PMID:Increased cyclic AMP content accelerates protein synthesis in rat heart. 247 73

We have studied cyclic AMP-mediated regulation of the beta 2-adrenergic receptor (beta 2AR). The effects of cAMP were assessed in Chinese hamster fibroblast (CHW) cells expressing either the wild type human beta 2AR receptor (CH-beta 2) or mutated forms of the receptor lacking the consensus sequences for phosphorylation by the cAMP-dependent protein kinase. Treatment of the CH-beta 2 cells with the cAMP analogue dibutyryl cAMP (Bt2cAMP) induces a time-dependent "down-regulation" of the number of beta 2AR. This down-regulation of the receptors is accompanied by a decline in the steady state level of beta 2AR mRNA. Moreover, the treatment with Bt2cAMP induces an increase in the phosphorylation level of the membrane-associated beta 2AR. Both the reduction in beta 2AR mRNA and the enhanced phosphorylation of the receptor are rapid and precede the loss of receptor. The down-regulation of beta 2AR induced by Bt2cAMP is concentration-dependent and mimicked by the other biologically active cyclic nucleotide analogue, 8-Br-cAMP, by forskolin, and by the phosphodiesterase inhibitor, isobutylmethylxanthine. In the CHW cell lines expressing receptors lacking the putative protein kinase A phosphorylation sites, the Bt2cAMP-induced phosphorylation of beta 2AR is completely abolished. In these cells the down-regulation of beta 2AR receptor number produced by cAMP is significantly slowed, whereas the reduction in beta 2AR mRNA level is equivalent to that observed in CH-beta 2 cells. These data indicate that there are at least two pathways by which cAMP may decrease the number of beta 2ARs in cells: one involves phosphorylation of the receptor by the cAMP-dependent protein kinase and the other leads to a reduction in steady state beta 2AR mRNA levels.
 ...
PMID:Two distinct pathways for cAMP-mediated down-regulation of the beta 2-adrenergic receptor. Phosphorylation of the receptor and regulation of its mRNA level. 247 47


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