Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

1. To address the questions of whether beta-adrenoreceptor stimulation can augment ATP-sensitive potassium current (IK(ATP)), and what the mechanism of such an effect might be, action potentials and whole-cell ionic currents were recorded from adult cat cardiac ventricular myocytes using a conventional whole-cell patch technique. 2. An outwardly directed, ohmic, non-inactivating, glyburide (10 microM)-sensitive current reversing near the reversal potential for potassium (EK) developed slowly (10-25 min) in cells dialysed with an ATP-free pipette (intracellular) solution. During this time, action potential duration markedly decreased while the resting membrane potential hyperpolarized closer to EK. Extended (> 30 min) periods of internal dialysis with ATP-free solution eventually resulted in run-down of the outward current. 3. Externally applied isoprenaline (1 microM) caused a rapidly developing (< or = 60 s), sustained enhancement of a glyburide (10 microM)-sensitive IK(ATP) in cells internally dialysed with ATP-free solution. IK(ATP) remained elevated even after the isoprenaline was removed, and subsequent applications of the beta-agonist failed to increase IK(ATP) further. Half-maximal isoprenaline stimulation of IK(ATP) occurred at a concentration of approximate of 1.5 nM. 4. Pretreatment with propranolol (1 microM) prevented the enhancement of IK(ATP) by a beta-agonist. 5. Isoprenaline-induced IK(ATP) could be blocked by either internal application of GDP-beta-S (2-5 mM) or pretreatment with cholera toxin (1-10 microgram ml-1, > 18 h). Pretreatment with pertussis toxin (1-2 microgram ml-1, > 18 h) did not attenuate the isoprenaline response, whereas internally applied GTP-gamma-S (100 microM) or F- (20 mM) caused IK(ATP) to increase rapidly in the absence of the beta-agonist. 6. Although externally applied forskolin (10 microM) also stimulated IK(ATP), neither 1,9-dideoxyforskolin (10 microM) nor 8-(4-chlorophenylthio)-cAMP (200 microM) had any effect on the current. Internal application of the adenylate cyclase inhibitor 2'-deoxyadenosine-3'-monophosphate (100 microM) resulted in a reduction in the response to isoprenaline, while internal application of a protein kinase A inhibitor (PKI5-24, 22.5 microM) did not attenuate the response to the beta-agonist. 7. IK(ATP) developed slowly during internal dialysis with ATP-free solution.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Enhancement of ATP-sensitive potassium current in cat ventricular myocytes by beta-adrenoreceptor stimulation. 801 90

To examine the effect of isoproterenol on Cl- current and its signal transduction pathway in beta-intercalated cells (beta-IC cell), peanut agglutinin (PNA) positive cells in culture were studied by the whole-cell clamp technique. We identified these cells as beta-IC cells by PNA-binding, cell alkalinization induced by Cl- free in the superfusate, and an increase in intracellular cAMP concentration by isoproterenol, but not by vasopressin. Application of isoproterenol in the voltage-clamp mode induced an activation of Cl- current in a dose-dependent fashion and its threshold concentration was in the order of 0.01 microM and ED50 was about 0.1 microM. This effect of isoproterenol was inhibited by atenolol, a beta-adrenergic blocker. Either extracellular application of forskolin or intracellular application of cAMP mimicked the action of isoproterenol. In the presence of forskolin or cAMP, isoproterenol caused little further activation of Cl- current. A synthetic inhibitor of protein kinase A (5-24 amide) inhibited the Cl- -channel activation by isoproterenol. Isoproterenol failed to activate the current in the presence of intracellular GDP beta S. By contrast, intracellular application of GTP gamma S rendered irreversible the Cl- -channel activation by brief exposure to isoproterenol. The present studies provide direct evidence that in the PNA-binding cell, probably the beta-IC cell, the stimulation of beta-adrenoceptor activates Cl- current through the signal transduction system involving G-protein, adenylate cyclase, cAMP, and protein kinase A.
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PMID:Isoproterenol stimulates Cl- current by a Gs protein-mediated process in beta-intercalated cells isolated from rabbit kidney. 810 76

The outward K+ current induced by step depolarization of freshly dispersed myocytes of guinea-pig taenia coli decreased about 80% upon treatment with 3 mM tetraethylammonium chloride (TEA). Isoproterenol (ISO, 2-5 microM) restored it to a large extent. This restoration did not occur in the presence of propranolol (2 microM). In single-channel recordings from cell-attached patches, the activity of maxi-K+ channel is dominant. When 3 mM TEA is incorporated in the pipette solution, the dominant channel-openings observed had much smaller unitary conductance. On the addition of ISO (2 microM) to the bath solution, but not to the pipette solution, K(+)-channel openings with unitary conductance similar to that without TEA treatment appeared. Cyclic AMP incorporated into the cytoplasm through the pipette was ineffective. These results indicate that ISO release TEA decrease of maxi-K+ channel conductance through some intracellular second messenger system other than adenylyl cyclase-protein kinase A system.
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PMID:Release of TEA blockade of maxi-K+ channels by isoproterenol. 819 80

Whole-cell Ca2+ channel currents in rabbit portal vein cells were recorded using the amphotericin B-perforated patch-clamp technique at 35 degrees C. This technique allowed recording of stable inward currents in the absence of run-down for more than 30 minutes. Depolarizing voltage steps from a holding potential of -70 mV elicited voltage-dependent inward currents. The voltage dependence of inward currents measured in either 2.5 mmol/L Ba(2+)- or 2.5 mmol/L Ca(2+)-containing solution were very similar. However, maximum Ba2+ current (obtained at around +10 mV) was approximately 1.5-fold larger than maximum Ca2+ current. Changing the holding potential from -70 to -40 mV decreased inward currents but did not shift the voltage dependence significantly. Inward currents were also completely blocked by the dihydropyridine Ca2+ channel blocker, nicardipine (10 mumol/L), suggesting the presence of predominantly L-type Ca2+ channels in rabbit portal vein cells. Isoproterenol caused small increases in the amplitude of Ba2+ currents in a concentration-dependent manner (10 nmol/L to 1 mumol/L), which were reversed with propranolol. Forskolin (1 mumol/L) or 8-bromo-cAMP (0.1 mmol/L) also caused small increases in the amplitude of Ba2+ currents, suggesting that the stimulatory actions of isoproterenol are importantly linked to the production of cAMP. Higher concentrations of of isoproterenol (10 mumol/L) or forskolin (10 mumol/L) caused a transient increase in Ba2+ currents followed by f decrease in current amplitude. Higher doses of 8-bromo-cAMP (1 mmol/L) and low doses of 8-bromo-cGMP (0.1 mmol/L) inhibited Ba2+ currents, increased the rate of current inactivation, and produced a negative voltage shift in steady-state availability. These results indicate that low concentrations of intracellular cAMP produce modest increases in Ca2+ channel activity, whereas cGMP and higher concentrations of cAMP result in inhibition of Ca2+ channel activity in vascular smooth muscle cells. The observed similarities of cGMP and high concentrations of cAMP on Ba2+ current amplitude, kinetics, and steady-state inactivation suggest mediation by a common mechanism, possibly involving activation of cGMP-dependent protein kinase.
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PMID:Regulation of Ca2+ channels by cAMP and cGMP in vascular smooth muscle cells. 822 84

Phosphorylation of cardiac myofibrillar proteins by protein kinase C (PKC) in isolated adult rat cardiomyocytes has been compared with that mediated by the cAMP-dependent protein kinase (PKA). PKA activation by beta-adrenoreceptor (isoproterenol) stimulation results in stoichiometric phosphorylation of troponin I (TnI) and C-protein. PKC activation by either 12-O-tetradecanoylphorbol-13-acetate (TPA) or by alpha-adrenoreceptor (phenylephrine plus propranolol) stimulation results in phosphorylation of the same two proteins to similar extents. Two-dimensional phosphopeptide mapping shows that the same sites in TnI are modified by PKC in vitro and in TPA- or alpha-agonist-stimulated cells. These sites are distinct from those phosphorylated in isoproterenol-stimulated cells or by PKA in vitro. Phosphopeptide mapping analysis of C-protein shows that PKC and PKA phosphorylate identical residues in this protein in vitro and in situ. TPA-stimulated phosphorylation in myocytes is associated with a reduction in maximal activity of myofibrillar Ca(2+)-dependent actomyosin MgATPase. Isoproterenol-stimulated phosphorylation has no effect on maximal activity but reduces the Ca2+ sensitivity of the MgATPase. These data demonstrate that TnI and C-protein are phosphorylated in myocardial cells by both PKA and PKC, resulting in different functional consequences in each case.
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PMID:Protein kinase C-mediated phosphorylation of troponin I and C-protein in isolated myocardial cells is associated with inhibition of myofibrillar actomyosin MgATPase. 838 12

The present study was designed to investigate the effect of phospholipase C and compounds known to promote synthesis of cAMP on System A transport activity under basal and insulin-stimulated conditions in the incubated muscle. In parallel, we also examined the effect of these agents on muscle glucose transport activity. Phospholipase C caused marked stimulation of alpha-(methyl)-aminoisobutyric acid (MeAIB--a System-A-specific analogue) uptake uptake and that of 3-O-methylglucose by the incubated muscle. In contrast, the activatory effect of insulin on System A was largely inhibited by phospholipase C. The effects of phospholipase C on transport processes differed from the effects provoked by phorbol esters (TPA), indicating that they are not just a consequence of TPA-sensitive protein kinase C activation. Agents such as isoproterenol, cholera toxin or forskolin, known cAMP inducers, caused glycogen depletion and stimulation of lactate production in the incubated muscle. However, these agents did not alter basal or insulin-stimulated MeAIB uptake. Isoproterenol and cholera toxin did not affect maximal stimulation of 3-O-methylglucose uptake caused by insulin. Our data indicate that System A transport is activated by phospholipase C in skeletal muscle, and that this effect is not due simply to activation of TPA-sensitive isoforms of protein kinase C. The effect of insulin on System A is reduced by either phospholipase C or TPA, which suggests the mediation of protein kinase C. On the basis of the lack of effect of cAMP-inducing agents on insulin-stimulated System A and glucose transport activities, we conclude that cAMP-dependent protein kinase does not cause any generalized blockade of insulin action in skeletal muscle, in contrast to what has been reported in other cell types.
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PMID:Regulation of System A amino-acid transport activity by phospholipase C and cAMP-inducing agents in skeletal muscle: modulation of insulin action. 838 2

The mechanism of action of vasoactive intestinal peptide (VIP) was examined in isolated gastric and taenia coli muscle cells and compared with that of nitric oxide (NO), sodium nitroprusside (SNP), and isoproterenol. In gastric muscle cells, VIP stimulated NO production, increased adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) levels, and induced relaxation in a concentration-dependent fashion. The NO synthase inhibitor NG-nitro-L-arginine abolished NO and cGMP production and partly inhibited relaxation. The soluble guanylate cyclase inhibitor LY 83583 abolished cGMP production and partly inhibited relaxation. (R)-p-adenosine 3',5'-cyclic phosphorothioate [(R)-p-cAMPS], a preferential inhibitor of cAMP-dependent protein kinase (cAK), and KT5823, a preferential inhibitor of cGMP-dependent protein kinase (cGK), partly inhibited relaxation separately and abolished relaxation in combination. The pattern implied that VIP induced relaxation by activation of cAK and by NO-mediated stimulation of cGMP and activation of cGK. In taenia coli muscle cells, VIP did not increase NO production or cGMP levels: relaxation was accompanied by an increase in cAMP and was partly inhibited by (R)-p-cAMPS and KT5823 and abolished by a combination of both inhibitors. Isoproterenol increased only cAMP levels in both cell types, which induced relaxation by activating cAK at low concentrations of agonist and both cAK and cGK at high concentrations in a pattern identical to that observed with VIP in taenia coli muscle cells. SNP and NO increased only cGMP levels in both cell types, which induced relaxation by activating cGK only. We conclude that cAK and cGK can be activated separately and mediate relaxation independently.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Activation of distinct cAMP- and cGMP-dependent pathways by relaxant agents in isolated gastric muscle cells. 838 96

Langendorff-perfused guinea pig ventricles were used to examine the effects of the adenosine agonists, (-)-N-6-phenylisopropyl-adenosine (PIA) and 5'-N-ethylcarboxamidoadenosine and the muscarinic cholinergic agonist, acetylcholine, on the rate of tension development, protein phosphatase inhibitor-1 (PPI-1) activity, and cyclic AMP-dependent protein kinase (PKA) activity ratio. Isoproterenol (10 nM) and forskolin (1 microM) stimulated rate of tension development, PKA activity ratio and PPI-1 activity each approximately 2-fold. Acetylcholine (1 microM) by itself was not effective, but when administered with isoproterenol for forskolin reduced the rate of tension development and PPI-1 activity without decreasing PKA activity ratio. Similarly, both PIA and 5'-N-ethylcarboxamidoadenosine alone were ineffective, but when simultaneously applied with isoproterenol attenuated the isoproterenol-stimulated rate of tension development and PPI-1 activity. PIA reduced PKA activity ratio, whereas 5'-N-ethylcarboxyamidoadenosine failed to do so. However, the effect of PIA on PKA activity ratio was smaller than those seen on rate of tension development and PPI-1 activity. Hence, the present data do not support a cyclic AMP-dependent regulation of PPI-1 activity by adenosine and muscarinic agonists. It is tempting to speculate that adenosine and muscarinic agonists reduce PPI-1 activity by a cyclic AMP-independent mechanism.
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PMID:Comparison of adenosine and muscarinic receptor-mediated effects on protein phosphatase inhibitor-1 activity in the heart. 839 48

Monolayers of SV-40 immortalized human airway epithelial cell lines were stimulated with bradykinin and isoproterenol to study protein phosphorylation responses that accompany ion transport regulation in normal (BEAS) and cystic fibrosis (CF/T43) cells. Phosphorylation responses were analyzed by two-dimensional gel electrophoresis of postmicrosomal supernatant fractions of 32Pi-labeled cells. Isoproterenol increased the labeling of three phosphoproteins of M(r) 17,000, 18,000, and 37,000 that were equivalent to proteins known to undergo cAMP-dependent phosphorylation in T84 cell monolayers. Distinct proteins showed increased phosphorylation with bradykinin, including acidic proteins of M(r) 15,000 and 29,000. These resembled proteins exhibiting Ca(2+)-dependent phosphorylation T84 cells. The CF/T43 and BEAS cell protein phosphorylation responses were indistinguishable. These findings support the concept that the regulation and function of protein kinase A is normal in cystic fibrosis airway epithelia and that the abnormal cAMP-mediated regulation of chloride permeability in these cells is due to altered regulatory or effector proteins.
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PMID:Protein phosphorylation responses in normal and cystic fibrosis airway epithelial cell lines. 839 78

Myocytes isolated from rat hearts that have suffered 35% myocardial infarction (MI) 3 wk prior have lower peak cytosolic Ca2+ concentration ([Ca2+]i) during contraction compared with Sham myocytes, a difference that is amplified by isoproterenol or high extracellular Ca2+ concentration ([Ca2+]o). To evaluate whether reduced [Ca2+]i in MI myocytes is due to decreased Ca2+ entry, we measured [3H]PN-200-110 [dihydropyridine (DHP)] binding and whole cell Ca2+ current (ICa). DHP binding decreased in both sarcolemmal vesicles and intact myocytes from hearts 3 wk after MI. In contrast, ICa was not different between Sham and MI myocytes incubated at 1.8 mM [Ca2+]o. At 5.0 mM [Ca2+]o, ICa increased similarly in Sham and MI myocytes. Steady-state voltage dependence of activation and inactivation were similar between Sham and MI myocytes, as were the fast- and slow-inactivation time constants. Isoproterenol (1 microM) significantly increased ICa in Sham but not in MI myocytes. Forskolin (10 microM) dibutyryl adenosine 3',5'-cyclic monophosphate (5 mM) significantly increased ICa in MI myocytes; the magnitude of ICa increase was similar to that observed in Sham myocytes. We conclude that 1) decreased systolic [Ca2+]i in MI myocytes was not due to reduced Ca2+ entry via L-type Ca2+ channels; 2) discrepancy between DHP binding (decrease) and ICa (no change) results may be explained by higher channel availability and/or increased long-opening modes (mode 2) in MI myocytes; 3) reduction in isoproterenol-induced [Ca2+]i increase in MI myocytes was partly due to decreased ICa, resulting in less Ca2+ release from sarcoplasmic reticulum; 4) the adenylate cyclase-protein kinase A signal-transduction pathway functioned normally in MI myocytes; and 5) decreased beta-adrenergic responsiveness in MI myocytes was likely due to altered coupling by G proteins.
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PMID:Calcium currents in postinfarction rat cardiac myocytes. 857 75


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