Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of forskolin (FO) and a water-soluble derivative of FO, L858051 (7 beta-desacetyl-7 beta-[gamma-(N-methylpiperazino)-butyryl] forskolin), were compared on calcium currents (ICa) studied by the whole-cell patch-clamp technique in frog ventricular cardiac myocytes. Both FO and L858051 increased ICa, with half-times of 160 +/- 20 sec and 343 +/- 22 sec, respectively. The stimulation was blocked by internal perfusion with inhibitors of protein kinase A. The EC50 for stimulation of ICa was 0.3 microM for FO and 1.0 microM for L858051. The maximal stimulated current was the same for both drugs, 20.3 microA/cm2 and 23.1 microA/cm2, respectively. Internal perfusion with 30-500 microM guanylyl 5'-imidodiphosphate [Gpp(NH)p] suppressed ICa stimulation by low concentrations of FO or L858051. This suppression was due to a rightward shift in the concentration-response curve, with increases in the EC50 values to 11.4 microM for FO and 28.4 microM for L858051. Isoproterenol (ISO) was ineffective in increasing ICa after the FO-stimulated ICa had been reduced by Gpp(NH)p and FO had been washed out. In contrast, after the L858051-stimulated current had been reduced by Gpp(NH)p, ISO stimulated ICa significantly. This stimulation was blocked by inhibitors of protein kinase A and was due to a positive effect of L858051 not shared by FO. A brief application of L858051 after Gpp(NH)p had blocked the ISO response restored the ISO response for at least 30 min. This effect was mimicked by internal perfusion with low concentrations of L858051. We conclude that the ability of brief exposure of L858051, but not FO, to restore the response to ISO after Gpp(NH)p is due to the accumulation of L858051 intracellularly, due to its hydrophilicity. Because internal L858051 and FO are very ineffective in stimulating adenylyl cyclase, whereas internal L858051 can restore the ISO response blocked by Gpp(NH)p, we propose that FO compounds can affect adenylyl cyclase at two sites, one site that is accessible only from the extracellular side that stimulates catalytic activity and another that is accessible from the intracellular side that increases beta-agonist efficacy in the presence of Gpp(NH)p.
Mol Pharmacol 1992 May
PMID:Differences in effects of forskolin and an analog on calcium currents in cardiac myocytes suggest intra- and extracellular sites of action. 131 1

Calf thymus Topo I is found to be associated with three active breakdown products, resolved from intact enzyme, which do not appear to be unique to one extraction procedure. They are phosphoproteins, whose enzymatic activity can be modulated through changes in phosphorylation, and which can be phosphorylated 'in vitro', by N II protein kinase, in the same five sites as the intact enzyme. Different amounts of 32P incorporated are observed however, in the corresponding sites. We conclude: 1. proteolysis is probably an 'in vivo' phenomenon, as the Topo I smaller species are observed, during isolation from the earlier crude fractions, and as a minimum of them is always present, even if precautions are taken to minimize proteolysis; 2. a specific regulatory role in the DNA relaxational activity might be played by N II protein kinase phosphorylation, indeed, in the smaller species; 3. the different degrees of 32P incorporation, in analogous phosphorylation sites, might represent a different signal for modulating the gene expression.
Mol Biol Rep 1992 May
PMID:Specific regulatory role of phosphorylation of calf thymus DNA-topoisomerase I smaller forms on the relaxational activity expression. Phosphorylation role on Topo I smaller forms activity. 131 99

The aim of the present study was to further elucidate the physiological role of the calcium-calmodulin (Ca(2+)-Cm)-dependent protein kinase system on phospholamban phosphorylation in the intact functioning heart. The effect of increasing extracellular calcium concentration [Ca]o on phospholamban phosphorylation (PHPL) was studied under different experimental conditions: (a) regular twitches and ryanodine induced-tetani both in the presence and in the absence of 3 x 10(-8) M isoproterenol and (b) Post-stimulation potentiation (PSP), i.e. the potentiation of contractility that follows a period of rapid repetitive stimulation. In the regular twitch, the increase in [Ca]o enhanced contractility both, in the absence and in the presence of beta-stimulation without changing basal or isoproterenol stimulated cAMP levels respectively. This increase in contractility was accompanied by a significant enhancement of PHPL-from 90.6 +/- 16.4 to 216 +/- 35.2 pmols 32Pi/mg protein at 0.25 and 3.85 mM [Ca]o respectively-only when isoproterenol was present. The calmodulin antagonist W-7 significantly decreased the isoproterenol-induced phosphorylation of phospholamban at [Ca]o 1.35 mM. Similar results were obtained under tetanic conditions. When myocardial contractility was enhanced by PSP up to ten-times with respect to the regular twitch, no detectable effect in PHPL was observed. Indirect evidence obtained from skinned rat cardiac trabeculae suggested that the failure of the cAMP-independent mechanisms to phosphorylate phospholamban is not related to a deficient increase in intracellular calcium. The results support the notion that the increase in intracellular calcium induces an increase in PHPL only at high intracellular cAMP levels.
J Mol Cell Cardiol 1992 Apr
PMID:Phosphorylation of phospholamban in the intact heart. A study on the physiological role of the Ca(2+)-calmodulin-dependent protein kinase system. 132 Jan 29

Corpora lutea of rats, like those of many other species, contain two sub-populations of luteal cells. In this report we sought to determine whether the luteinizing hormone (LH)- and beta-adrenergic cAMP signal transduction pathways known to be present in rat corpora lutea were segregated into separate luteal cell types. Results showed that large rat luteal cells, obtained on day 3 of pregnancy, exhibited elevated LH- and most notably epinephrine-stimulated adenylyl cyclase activities but equivalent cAMP-dependent catalytic protein kinase and total regulatory subunit cAMP binding activities compared to small luteal cells. Progesterone production by the large cell was greater than that by the small cell but both cells were equally sensitive to stimulation of progesterone by LH. However, neither the large nor the small rat luteal cell produced significant progesterone in response to epinephrine despite a marked epinephrine-stimulated adenylyl cyclase in both cell populations. The LH-stimulated progesterone synthetic response of the two sub-populations of rat luteal cells is more similar to that of the developing monkey corpus luteum and contrasts sharply with that of ruminants.
Mol Cell Endocrinol 1992 Jun
PMID:The cAMP-dependent signalling cascade in the two luteal cell types of the pregnant rat corpus luteum. 132 69

It is unclear whether reported fluctuations in the level of adenosine 3',5'-cyclic monophosphate (cAMP) during a single cardiac cycle in ventricular muscle are associated with distal changes in cAMP-dependent processes. The degree of cAMP variation and its effect, if any, on biochemical sequelae during the cardiac cycle, were investigated by determining the level of cAMP and the activity ratios of cAMP-dependent protein kinase and glycogen phosphorylase in the rat ventricular myocardium. Isolated perfused hearts contracting at 240 beats/min and free of exogenously administered catecholamines were freeze-clamped, utilizing an automated clamping device capable of freezing the entire heart in less than 50 ms. The cardiac cycle was segmented into phases utilizing three different segmentation schemes. No significant difference was detected between phases regardless of the method of segmentation for cAMP, cAMP-dependent protein kinase, or glycogen phosphorylase levels. These results suggest that the levels of cAMP and the activities of cAMP-dependent protein kinase and glycogen phosphorylase do not vary significantly during a single cardiac cycle in the mammalian myocardium.
J Mol Cell Cardiol 1992 May
PMID:Lack of oscillations in cyclic AMP, cAMP-protein kinase and glycogen phosphorylase during the cardiac cycle in perfused rat hearts. 132 13

Smooth muscle preparations of human aorta or pig coronary arteries contain nearly equal amounts of cGMP-dependent protein kinase isozymes (cGMP kinase I alpha and I beta). In order to understand the roles of these isozymes in relaxing vascular smooth muscle, several new cGMP analogs were synthesized and tested for potencies in activating each enzyme and in relaxing pig coronary arteries. Analogs modified with a derivatized phenylthio group at the 8-position were as much as 72-fold more potent in activating purified cGMP kinase I alpha than cGMP kinase I beta. Electron-donating substituents, such as hydroxy, amino, and methoxy, on the phenyl ring enhanced the potencies of these analogs in activating cGMP kinase I alpha. The most potent of these cGMP analogs [8-(4-hydroxyphenylthio)-cGMP] was 17 times more potent (EC50 = 1.1 microM) as a muscle relaxant than the most efficacious analog tested previously. Among derivatives with an 8-halo group, 8-iodo-cGMP was the most potent compound (Ka = 9 nM for I alpha and 122 nM for I beta) for both I alpha and I beta. Analogs modified at the 1,N2-position or at both the 1,N2-and 8-positions of cGMP were highly potent for activating both isozymes. Within this group, 8-I-beta-phenyl-1,N2-etheno-cGMP had Ka values of 22 nM and 17 nM for cGMP kinase I alpha and I beta, respectively, whereas the Ka values of cGMP were 110 nM and 250 nM for the two isozymes. 8-I-beta-phenyl-1,N2-etheno-cGMP was the most potent muscle relaxant tested, with EC50 of 0.4 microM. For all cGMP analogs tested, there was a positive correlation between potency for activation of cGMP kinase I alpha and that for relaxation of pig coronary arteries. Assuming that the kinase assay conditions yielded a cyclic nucleotide specificity similar to that which would exist in intact cells, it was concluded that the cGMP kinase I alpha isozyme mediates the relaxation of pig coronary artery smooth muscle caused by cGMP elevation. However, an additional role for cGMP kinase I beta in the relaxation process could not be ruled out.
Mol Pharmacol 1992 Jul
PMID:Relaxation of pig coronary arteries by new and potent cGMP analogs that selectively activate type I alpha, compared with type I beta, cGMP-dependent protein kinase. 132 50

Growth of S49 wild-type (WT) lymphoma cells for 24 hr with 3 nM epinephrine produces a very pronounced attenuation of cAMP accumulation in response to subsequent challenges with much higher concentrations of the catecholamine [Mol. Pharmacol. 36:459-464 (1989)]. We report here the effects of this treatment, in S49 WT, cyc-, and kin- cells, on the responsiveness of adenylate cyclase in partially purified membranes. The desensitization of adenylate cyclase in the S49 WT cells after 24-hr treatment was homologous, in that only responses to epinephrine were attenuated. The EC50 for epinephrine stimulation of adenylate cyclase was 54 +/- 8% (mean +/- standard error) higher in treated cells than in controls, and there was a 32 +/- 3% reduction in Vmax at supramaximal epinephrine concentrations. The treatment also caused a 34 +/- 9% reduction in the levels of the beta-adrenergic receptor (beta AR), which was of a sufficient magnitude to account for the homologous desensitization seen. The 24-hr treatment had similar effects in S49 kin- cells, where we observed a 28 +/- 4% decrease in Vmax, a 35 +/- 6% increase in EC50 for epinephrine stimulation of adenylate cyclase, and a 25 +/- 3% decrease in beta AR. In contrast, the 24-hr treatment had no measurable effect on adenylate cyclase activity in S49 cyc- cells. That is, the responsivity of adenylate cyclase reconstituted with Gs from S49 WT cells was not attenuated, although beta AR levels were significantly decreased. The desensitization of S49 cells with the 24-hr treatment was additive with that mediated by the cAMP-dependent protein kinase (cAPK). Further, unlike the cAPK-mediated attenuation, it was relatively insensitive to the levels of free Mg2+ in the adenylate cyclase reaction mixture. The characteristics of the desensitization produced by 24-hr treatment with 3 nM epinephrine, together with the observation that it is similar in S49 WT and kin- cells, demonstrates that the process in WT cells is, at least in part, independent of the rapid cAPK-mediated desensitization. It is also most likely that it is unrelated to the rapid cAMP-independent processes involving sequestration/internalization or the beta AR kinase, because those mechanisms require much higher receptor occupancies than the 0.2% occurring with 3 nM epinephrine. Thus, 24-hr treatment appears to produce attenuation of adenylate cyclase by causing down-regulation of beta AR, without involving any other known form of desensitization.
Mol Pharmacol 1992 Jul
PMID:Beta-adrenergic receptor levels and function after growth of S49 lymphoma cells in low concentrations of epinephrine. 132 52

Experiments were carried out to obtain information about the mechanism underlying the fast action of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in skeletal muscle. N-2'-o-dibutyryladenosine-3',5'-cyclic monophosphate (dbcAMP), similarly as 1,25(OH)2D3 (5 x 10(-10) M), rapidly increased 45Ca uptake by soleus muscle from vitamin D-deficient chicks (+25% and +98% at 3 min and 10 min, respectively) in a dose-dependent manner. The effects of the cAMP analog (10 microM) and 1,25(OH)2D3 could be abolished by the Ca(2+)-channel blocker nifedipine and the calmodulin antagonist flufenazine. Calmodulin binding by two muscle microsomal proteins of 28 kDa and 30 kDa was stimulated within 1 min of exposure of the tissue to 1,25(OH)2D3. Direct effects of the sterol on membrane calmodulin binding were shown with isolated microsomes. The 1,25(OH)2D3-mediated rise of [125I]calmodulin binding to microsomal membranes was dependent on the presence of medium ATP. Forskolin (10 microM) and cAMP (10 microM) also increased [125I]calmodulin binding (+75% and +64%, respectively, with respect to controls). Pretreatment of microsomal membranes with cAMP-dependent protein kinase inhibitor (1 microgram/ml) or addition of alkaline phosphates (1 U/ml) after hormonal treatment caused complete inhibition of 1,25(OH)2D3-induced [125I]calmodulin binding to microsomal membrane proteins. These results imply modifications of membrane protein phosphorylation through the cAMP signal pathway and in turn of calmodulin binding in the mechanism by which 1,25(OH)2D3 rapidly stimulates skeletal muscle Ca2+ uptake.
Mol Cell Endocrinol 1992 Mar
PMID:Regulation of Ca2+ uptake in skeletal muscle by 1,25-dihydroxyvitamin D3: role of phosphorylation and calmodulin. 132 29

The role of the phosphorylation and dephosphorylation of sarcolemma and that of the alteration of membrane lipids in the endotoxin-induced impairment of the ATP-dependent Ca2+ transport in canine cardiac sarcolemma were investigated. The results indicate that the ATP-dependent Ca2+ transport in canine cardiac sarcolemma was decreased by 30-35% 4 h after endotoxin administration. Phosphorylation of sarcolemma by the catalytic subunit of the cAMP-dependent protein kinase or calmodulin stimulated ATP-dependent Ca2+ transport in both groups, however, the phosphorylation-stimulated activities remained significantly lower in endotoxic animals. Dephosphorylation of sarcolemma decreased ATP-dependent Ca2+ transport in both groups, yet, the time required to reach maximal dephosphorylation was reduced from 120 to 90 min 4 h post-endotoxin. Analysis of sarcolemmal membranes reveals that phosphatidylcholine and phosphatidylethanolamine contents were decreased while their respective lysophosphatide levels were increased significantly after endotoxin injection. Digestion of control heart sarcolemma with phospholipase A2 inhibited Ca2+ transport and the inhibition was reversible by phosphatidylcholine. The inhibition caused by the in vivo administration of endotoxin was completely reversible by the addition of phosphatidylcholine. Based on these data, it is concluded that endotoxin administration impairs ATP-dependent Ca2+ transport in canine cardiac sarcolemma and that the impairment may be due to i) a defective phosphorylation of sarcolemma; ii) a reduced number of Ca2+ pumps; iii) an accelerated dephosphorylation of sarcolemma; and iv) an alteration in membrane phospholipid profile in response to phospholipase A activation.
Mol Cell Biochem 1992 Jun 26
PMID:Heart sarcolemmal Ca2+ transport in endotoxin shock: II. Mechanism of impairment in ATP-dependent Ca2+ transport. 132 89

The regulation of the guinea-pig pancreatic acinar plasma membrane Ca2+ pump by protein kinase A, protein kinase C and calmodulin was investigated. The results were compared with the effects of these regulators on the high affinity Ca(2+)-ATPase found in this membrane preparation. The catalytic subunit of cyclic AMP-dependent protein kinase stimulated Ca2+ transport 2-fold, but had no effect on Ca(2+)-dependent ATPase activity. Purified protein kinase C, the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate and diacylglycerol derivative, 1-stearoyl-2-arachidonoyl-sn-glycerol, failed to stimulate the Ca(2+)-uptake but augmented the Ca(2+)-dependent ATPase activity. Exogenously added calmodulin failed to stimulate either activity. In addition, two antagonists of calmodulin activity, trifluoperazine and compound 48/80 produced a concentration-dependent inhibition of Ca(2+)-transport. These data suggest the presence of endogenous calmodulin within guinea-pig pancreatic acinar plasma membranes. Both calmodulin antagonists failed to influence the Ca(2+)-dependent ATPase activity. The ability of boiled extracts from guinea-pig pancreatic acinar plasma membranes to stimulate the Ca(2+)-ATPase activity in calmodulin-depleted erythrocyte plasma membranes confirmed the presence of endogenous calmodulin. Our results imply a role for calmodulin and cAMP-dependent protein kinase, but not protein kinase C, in the regulation of Ca2+ efflux from pancreatic acinar cells. These results also provide further evidence suggesting that the high affinity Ca(2+)-ATPase does not catalyze the plasma membrane Ca(2+)-transport activity observed in pancreatic acini.
Mol Cell Biochem 1992 Jun 26
PMID:Regulation of calcium transport in pancreatic acinar plasma membranes from guinea pig. 132 90


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