Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The role of the cGMP pathway in the modulation of the cardiac L-type Ca2+ current (ICa,L) by nitric oxide (NO) was examined in rat ventricular myocytes. 2. The NO donors DEANO, SIN-1, SNP, SNAP and GSNO had no significant effects on basal ICa,L. However, DEANO (100 microM) inhibited ICa,L after the current had been previously stimulated by either isoprenaline (Iso, 1-10 nM), a beta-adrenergic agonist, or isobutylmethyl-xanthine (IBMX, 10-80 microM), a wide spectrum phosphodiesterase (PDE) inhibitor. 3. The anti-adrenergic effect of DEANO on ICa,L was not mimicked by other NO donors (SIN-1, SNAP and SPNO). 4. The NO-sensitive guanylyl cyclase inhibitor ODQ (10 microM), antagonized the inhibitory effect of DEANO on ICa,L. Likewise, inhibitors of the cGMP-dependent protein kinase (cG-PK), Rp-8-chloro-phenylthio-cGMP (10 microM) and KT5823 (0.1 and 0.3 microM), also abolished the inhibitory effect of DEANO on Iso (1-10 nM)-stimulated ICa,L. 5. Intracellular dialysis with exogenous cAMP (10-100 microM) blunted the inhibitory effect of DEANO (10 and 100 microM) on ICa,L. SNAP and SNP also had no effect on the cAMP-stimulated ICa,L. 6. Pre-treatment of the myocytes with pertussis toxin (0.5 microg ml-1, 4-6 h at 37 degrees C) eliminated the inhibitory effect of DEANO (100 microM) on ICa,L, in the presence of either Iso (0.01 and 1 nM) or IBMX (10-80 microM). 7. These results demonstrate that DEANO produces anti-adrenergic effects in rat ventricular myocytes. This effect of DEANO occurs in a cGMP-dependent manner, and involves activation of cG-PK and regulation of a pertussis toxin-sensitive G protein.
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PMID:G protein-mediated inhibitory effect of a nitric oxide donor on the L-type Ca2+ current in rat ventricular myocytes. 1117 96

Platelets release a soluble factor into blood and conditioned medium (PCM) that decreases vascular endothelial permeability. The objective of this study was to determine the signal-transduction pathway that elicits this decrease in permeability. Permeability-decreasing activity of PCM was assessed by the real-time measurement of electrical resistance across cell monolayers derived from bovine pulmonary arteries and microvessels. Using a desensitization protocol with cAMP/protein kinase A (PKA)-enhancing agents and pharmacological inhibitors, we determined that the activity of PCM is independent of PKA and PKG. Genistein, an inhibitor of tyrosine kinases, prevented the increase in endothelial electrical resistance. Because lysophosphatidic acid (LPA) has been proposed to be responsible for this activity of PCM and is known to activate the G(i) protein, inhibitors of the G protein pertussis toxin and of the associated phosphatidylinositol 3-kinase (PI3K) wortmannin were used. Pertussis toxin and wortmannin caused a 10- to 15-min delay in the characteristic rise in electrical resistance induced by PCM. Inhibition of phosphorylation of extracellular signal-regulated kinase with the mitogen-activated kinase kinase inhibitors PD-98059 and U-0126 did not prevent the activity of PCM. Similar findings with regard to the cAMP protocols and inhibition of G(i) and PI3K were obtained for 1-oleoyl-LPA. These results demonstrate that PCM increases endothelial electrical resistance in vitro via a novel, signal transduction pathway independent of cAMP/PKA and cGMP/PKG. Furthermore, PCM rapidly activates a signaling pathway involving tyrosine phosphorylation, the G(i) protein, and PI3K.
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PMID:Platelet-conditioned medium increases endothelial electrical resistance independently of cAMP/PKA and cGMP/PKG. 1166 60

Using an isolated working heart preparation we show that angiotensin II (ANG II), at concentrations of 10(-10)-10(-7) mol l(-1), elicits negative chronotropism and inotropism in the freshwater eel Anguilla anguilla. The negative inotropism was insensitive to losartan and CGP42112 (AT(1) and AT(2) ANG II receptor antagonists, respectively), and was abrogated by the AT(1) receptor antagonist CV11974, the G protein blocker pertussis toxin (PTx) and the muscarinic antagonist atropine. In contrast, it was not affected by the adrenoceptor antagonists propanolol, sotalol and phentolamine. Using donors (L-arginine) and inhibitors [N(G)-monomethyl-(L)-arginine (L-NMMA), L-N(5)(1-iminoethyl)ornithine ((L)-NIO)] of nitric oxide synthase (NOS), and haemoglobin as NO scavenger, we demonstrate that NO signalling is involved in ANG II-mediated inotropism. Pretreatment with Triton X-100, a detergent that damages the endocardial endothelium (EE), or with 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ), a specific inhibitor of soluble guanylate cyclase, or with the cGMP-activated protein kinase (PKG) inhibitor KT5328, abolished ANG II-mediated inotropism. Thus, ANG II-mediated inotropism occurs via an EE-NO-cGMP-PKG mechanism. ANG II did not affect the mechanical performance influenced by preload changes (i.e. the Frank-Starling response), which in the eel heart is modulated by NO. This EE-paracrine-mediated cardio-suppressive action of endoluminal ANG II suggests that the hormone plays an important intracardiac role in the fish heart.
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PMID:Angiotensin II-induced inotropism requires an endocardial endothelium-nitric oxide mechanism in the in-vitro heart of Anguilla anguilla. 1281 73

We have studied the effects of exogenous human recombinant Vasostatin-1 (VS-1), Vasostatin-2 (VS-2) and the human Chromogranin A (CGA) 7-57 synthetic peptides on the mechanical performance of the isolated and perfused working eel (Anguilla anguilla) heart. Under basal conditions, the three peptides decreased stroke volume (SV) and stroke work (SW), thus exerting negative inotropism. The VS-1-mediated negative inotropism was abolished by exposure to inhibitors of either Gi/o protein (pertussis toxin; PTx) or M1 muscarinic receptors (Pirenzepine) or calcium (Lantanum and Diltiazem) and potassium (Ba2+, 4-aminopyridine, tetraethylammonium, glibenclamide) channels, while it required an intact endocardial endothelium (EE). Using NG-monomethyl-L-arginine (L-NMMA) as an inhibitor of nitric oxide (NO) synthase (NOS), and hemoglobin as a NO scavenger, we demonstrated the obligatory role of NO signaling in mediating the vasostatin response. Pretreatment with either a specific inhibitor of soluble guanylate cyclase (GC) 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ), or the inhibitor of the cGMP-activated protein kinase (PKG) KT5823, abolished the VS-1-mediated inotropism, indicating the cGMP-PKG component as a crucial target of NO signaling. Of note, VS-1 was effective in counteracting the adrenergic (Isoproterenol and Phenylephrine)-mediated positive inotropism. These findings provide the first evidence that vasostatins exert cardiotropic action in fish, thus suggesting their long evolutionary history as well as their species-specific mechanisms of action.
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PMID:Influence of vasostatins, the chromogranin A-derived peptides, on the working heart of the eel (Anguilla anguilla): negative inotropy and mechanism of action. 1547 32

Glucagon, secreted from pancreatic alpha-cells integrated within the islets of Langerhans, is involved in the regulation of glucose metabolism by enhancing the synthesis and mobilization of glucose in the liver. In addition, it has other extrahepatic effects ranging from lipolysis in adipose tissue to the control of satiety in the central nervous system. In this article, we show that the endocrine disruptors bisphenol A (BPA) and diethylstilbestrol (DES), at a concentration of 10(-9) M, suppressed low-glucose-induced intracellular calcium ion ([Ca2+]i) oscillations in alpha-cells, the signal that triggers glucagon secretion. This action has a rapid onset, and it is reproduced by the impermeable molecule estradiol (E2) conjugated to horseradish peroxidase (E-HRP). Competition studies using E-HRP binding in immunocytochemically identified alpha-cells indicate that 17beta-E2, BPA, and DES share a common membrane-binding site whose pharmacologic profile differs from the classical ER. The effects triggered by BPA, DES, and E2 are blocked by the G alpha i- and G alpha o-protein inhibitor pertussis toxin, by the guanylate cyclase-specific inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, and by the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester. The effects are reproduced by 8-bromo-guanosine 3',5'-cyclic monophosphate and suppressed in the presence of the cGMP-dependent protein kinase inhibitor KT-5823. The action of E2, BPA, and DES in pancreatic alpha-cells may explain some of the effects elicited by endocrine disruptors in the metabolism of glucose and lipid.
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PMID:Low doses of bisphenol A and diethylstilbestrol impair Ca2+ signals in pancreatic alpha-cells through a nonclassical membrane estrogen receptor within intact islets of Langerhans. 1607 65

We have examined the effects of the cannabinoid anandamide (AEA) and its stable analog, methanandamide (methAEA), on large-conductance, Ca2+-activated K+ (BK) channels using human embryonic kidney (HEK)-293 cells, in which the alpha-subunit of the BK channel (BK-alpha), both alpha- and beta1-subunits (BK-alphabeta1), or both alpha- and beta4-subunits (BK-alphabeta4) were heterologously expressed. In a whole cell voltage-clamp configuration, each cannabinoid activated BK-alphabeta1 within a similar concentration range. Because methAEA could potentiate BK-alpha, BK-alphabeta1, and BK-alphabeta4 with similar efficacy, the beta-subunits may not be involved at the site of action for cannabinoids. Under cell-attached patch-clamp conditions, application of methAEA to the bathing solution increased BK channel activity; however, methAEA did not alter channel activity in the excised inside-out patch mode even when ATP was present on the cytoplasmic side of the membrane. Application of methAEA to HEK-BK-alpha and HEK-BK-alphabeta1 did not change intracellular Ca2+ concentration. Moreover, methAEA-induced potentiation of BK channel currents was not affected by pretreatment with a CB1 antagonist (AM251), modulators of G proteins (cholera and pertussis toxins) or by application of a selective CB2 agonist (JWH133). Inhibitors of CaM, PKG, and MAPKs (W7, KT5823, and PD-98059) did not affect the potentiation. Application of methAEA to mouse aortic myocytes significantly increased BK channel currents. This study provides the first direct evidence that unknown factors in the cytoplasm mediate the ability of endogenous cannabinoids to activate BK channel currents. Cannabinoids may be hyperpolarizing factors in cells, such as arterial myocytes, in which BK channels are highly expressed.
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PMID:Activation of large-conductance, Ca2+-activated K+ channels by cannabinoids. 1610 1

The molecular mechanisms involved in the Ang-(1-7) [angiotensin-(1-7)] effect on sodium renal excretion remain to be determined. In a previous study, we showed that Ang-(1-7) has a biphasic effect on the proximal tubule Na+-ATPase activity, with the stimulatory effect mediated by the AT1 receptor. In the present study, we investigated the molecular mechanisms involved in the inhibition of the Na+-ATPase by Ang-(1-7). All experiments were carried out in the presence of 0.1 nM losartan to block the AT1 receptor-mediated stimulation. In this condition, Ang-(1-7) at 0.1 nM inhibited the Na+-ATPase activity of the proximal tubule by 54%. This effect was reversed by 10 nM PD123319, a specific antagonist of the AT2 receptor, and by 1 muM GDP[beta-S] (guanosine 5'-[beta-thio]diphosphate), an inhibitor of G protein. Ang-(1-7) at 0.1 M induced [35S]GTP[S] (guanosine 5'-[gamma-[35S]thio]triphosphate) binding and 1 mug/ml pertussis toxin, an inhibitor of G(i/o) protein, reversed the Ang-(1-7) effect. Furthermore, it was observed that the inhibitory effect of Ang-(1-7) on the Na+-ATPase activity was completely reversed by 0.1 microM LY83583, an inhibitor of guanylate cyclase, and by 2 muM KT5823, a PKG (protein kinase G) inhibitor, and was mimicked by 10 nM d-cGMP (dibutyryl cGMP). Ang-(1-7) increased the PKG activity by 152% and this effect was abolished by 10 nM PD123319 and 0.1 microM LY83583. Taken together, these data indicate that Ang-(1-7) inhibits the proximal tubule Na+-ATPase by interaction with the AT2 receptor that subsequently activates the G(i/o) protein/cGMP/PKG pathway.
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PMID:Involvement of the Gi/o/cGMP/PKG pathway in the AT2-mediated inhibition of outer cortex proximal tubule Na+-ATPase by Ang-(1-7). 1639 Mar 32

The aim of the present study was to determine the effect of pertussis toxin (PTX) on inflammatory hypernociception measured by the rat paw pressure test and to elucidate the mechanism involved in this effect. In this test, prostaglandin E(2) (PGE(2)) administered subcutaneously induces hypernociception via a mechanism associated with neuronal cAMP increase. Local intraplantar pre-treatment (30 min before), and post-treatment (5 min after) with PTX (600 ng/paw1, in 100 microL) reduced hypernociception induced by prostaglandin E(2) (100 ng/paw, in 100 microL, intraplantar). Furthermore, local intraplantar pre-treatment (30 min before) with PTX (600 ng/paw, in 100 microL) reduced hypernociception induced by DbcAMP, a stable analogue of cAMP (100 microg/paw, in 100 microL, intraplantar), which indicates that PTX may have an effect other than just G(i)/G(0) inhibition. PTX-induced analgesia was blocked by selective inhibitors of nitric oxide synthase (L-NMMA), guanylyl cyclase (ODQ), protein kinase G (KT5823) and ATP-sensitive K(+) channel (Kir6) blockers (glybenclamide and tolbutamide). In addition, PTX was shown to induce nitric oxide (NO) production in cultured neurons of the dorsal root ganglia. In conclusion, this study shows a peripheral antinociceptive effect of pertussis toxin, resulting from the activation of the arginine/NO/cGMP/PKG/ATP-sensitive K(+) channel pathway.
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PMID:Peripheral antinociceptive effect of pertussis toxin: activation of the arginine/NO/cGMP/PKG/ ATP-sensitive K channel pathway. 1693 Apr 43

We previously reported that atrial natriuretic factor (ANF) stimulates pancreatic secretion through NPR-C receptors coupled to PLC and potentiates secretin response without affecting cAMP levels. In the present study we sought to establish the intracellular signaling mechanism underlying the interaction between both peptides. In isolated pancreatic acini 100 nM ANF abolished cAMP accumulation evoked by any dose of secretin. Lower doses of ANF (1 fM, 1 pM, 1 and 10 nM) dose dependently reduced EC50 secretin-evoked cAMP. Although ANF failed to affect cAMP stimulated by amthamine (selective H2 agonist) or isoproterenol (beta-adrenergic agonist), it abolished VIP-induced cAMP formation. ANF inhibitory effect was prevented by U-73122 (PLC inhibitor) and GF-109203X (PKC inhibitor) but unaltered by PKG and nitric oxide synthase inhibition, supporting that the PLC/PKC pathway mediated the effect. ANF response was mimicked by cANP (4-23 amide) and abolished by pertussis toxin, strongly supporting NPR-C receptor activation. In vivo studies showed that ANF at 0.5 microg x kg(-1) x h(-1) enhanced secretion stimulated by 1 U x kg(-1) x h(-1) secretin but at 1 and 2 microg x kg(-1) x h(-1) it abolished secretin response. However, ANF at such doses failed to modify the secretion evoked by carbachol or CCK. Present results show that ANF negatively modulated secretin secretory response and intracellular signaling through the activation of NPR-C receptors coupled to the PLC/PKC pathway. Furthermore, the finding that ANF also inhibited VIP-evoked cAMP supports a selective modulation of class II G-protein coupled receptors by ANF. Present findings suggest that ANF may play a protective role by reducing secretin response to avoid overstimulation.
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PMID:Atrial natriuretic factor negatively modulates secretin intracellular signaling in the exocrine pancreas. 1697 19

Neuroendocrine regulation of cardiac function involves a population of three types of beta-adrenoceptors (ARs). In various mammalian species, beta1- and beta2-AR stimulation produces an increase in contractility; whereas beta3-AR activation mediates negative inotropic effects. At the moment, nothing is known about the physiological role of beta3-AR in fish. Using an isolated working heart preparation, we show that a beta3-AR selective agonist BRL(37344) (0.1-100 nmol l(-1)) elicits a dose-dependent negative inotropism in the freshwater eel Anguilla anguilla. This effect was insensitive to the beta1/beta2-AR inhibitor nadolol (10 mumol l(-1)), but was blocked by the beta3-AR-specific antagonist SR(59230) (10 nmol l(-1)). The analysis of the percentage of stroke work (SW) variations, in terms of EC(50) values, induced by BRL(37344) alone (10 nmol l(-1)), and in presence of SR(59230) (10 nmol l(-1)), indicated a competitive antagonism of SR(59230). In addition to the classic positive inotropism, the non-specific beta agonist isoproterenol (100 nmol l(-1)) induced, in 30% of the preparations, a negative inotropic effect that was abrogated by pre-treatment with SR(59230), pointing to a beta3-mediated pathway. The BRL(37344)-induced negative inotropic effect was abolished by exposure to a G(i/o) proteins inhibitor pertussis toxin (PTx; 0.01 nmol l(-1)), suggesting a G(i/o)-dependent mechanism. Using L-N5(l-imino-ethyl)ornithine (L-NIO; 10 mumol l(-1)), as a nitric oxide (NO) synthase (NOS) blocker and haemoglobin (Hb; 1 mumol l(-1)), as a NO scavenger, we demonstrated that NO signalling is involved in the BRL(37344)-induced response. Pre-treatment with either an inhibitor of soluble guanylate cyclase (GC) 1H-(1,2,4) oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ; 10 mumol l(-1)), or an inhibitor of the cGMP-activated protein kinase (PKG) KT(5823) (100 nmol l(-1)), abolished the beta3-dependent negative inotropism, indicating the cGMP-PKG component as a crucial target of NO signalling. Taken together, our findings provide functional evidence for the presence of beta3-like adrenoceptors in the eel Anguilla anguilla heart identifying, for the first time in a working fish heart, the beta3-AR-dependent negative inotropy discovered in mammals.
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PMID:Beta3-adrenoceptor in the eel (Anguilla anguilla) heart: negative inotropy and NO-cGMP-dependent mechanism. 1714 85


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