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

Atrial natriuretic peptide, acting through its second messenger guanosine 3',5'-cyclic monophosphate (cGMP), suppresses Na+ absorption across the renal inner-medullary collecting duct and increases urinary Na+ excretion. Patch clamp studies show that cGMP reduces Na+ absorption by inhibiting an amiloride-sensitive cation channel in the apical membrane. We have now examined, using the patch clamp technique, the molecular mechanisms of cGMP inhibition. Cyclic GMP directly and specifically reduced the probability of a single channel being open (open probability, Po) by 39% (inhibition constant, Ki = 7.6 x 10(-7) M) by a phosphorylation-independent mechanism. Cyclic GMP also inhibited the channel by activating cGMP-dependent protein kinase (cGMP-kinase). Exogenous cGMP-kinase completely inhibited the channel by a phosphorylation-dependent mechanism. Activation of a pertussis toxin-sensitive G protein by GTP-gamma-S blocked cGMP-kinase inhibition of the channel. By contrast, cGMP-kinase inhibition of Po was completely reversed by GTP-gamma-S. Taken together with the results of a previous study showing that a G protein activates the cation channel, these data indicate that cGMP-kinase and a G protein sequentially regulate the cation channel. Our results show that atrial natriuretic peptide, acting through cGMP, inhibits Na+ absorption across the inner-medullary collecting duct by a dual mechanism, and that cGMP-kinase inhibits the channel by a pathway involving a G protein.
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PMID:Dual ion-channel regulation by cyclic GMP and cyclic GMP-dependent protein kinase. 169 Mar 55

Cyclic GMP mediates vascular smooth muscle relaxation to a variety of drugs and naturally-occurring substances. The reduction of intracellular Ca2+ levels is believed to underlie this action, but the mechanism of this effect is unknown. In order to test the hypothesis that inhibition of guanine nucleotide-binding protein function is involved in the actions of cGMP, the effects of cGMP-dependent protein kinase on the phosphorylation of both pertussis toxin-sensitive (Gi/Go) and insensitive (Gz) G-proteins were examined in vitro. None of these proteins were effective substrates for either cGMP- or cAMP-dependent protein kinases, despite the fact that assay conditions were designed to detect poorly phosphorylated substrate proteins. In line with these observations, atriopeptin II did not inhibit angiotensin II-treated inositol phosphate formation in cultured vascular smooth muscle cells. These results suggest that phosphorylation by cGMP-dependent protein kinase of these G-proteins is not the major mechanism by which cGMP reduces intracellular Ca2+ levels in vascular smooth muscle.
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PMID:Pertussis toxin-sensitive and insensitive guanine nucleotide binding proteins (G-proteins) are not phosphorylated by cyclic GMP-dependent protein kinase. 183 99

Signal transduction for the characteristic long-term desensitization of glutamate receptors in Purkinje cells was investigated with wedge recordings from rat cerebellar slices. Long-term desensitization was induced specifically in the AMPA-selective subtype of glutamate receptors following brief exposure to 100 microM quisqualate. It was abolished either by treatment of the rat with pertussis toxin or by perfusion of a slice with BAPTA-AM, L-NMMA, hemoglobin, or inhibitor of PKG. Brief application of AMPA alone did not cause desensitization, but in combination with t-ACPD, sodium nitroprusside, or 8-bromo-cGMP, AMPA produced desensitization similar to that induced by quisqualate. These results indicate that the desensitization arises from activation of AMPA receptors in association with activation of metabotropic glutamate receptors, the latter leading to Ca2+ elevation to nitric oxide (NO) production to cGMP synthesis, and eventually to activation of PKG.
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PMID:Messengers mediating long-term desensitization in cerebellar Purkinje cells. 196 3

The phosphodiesterase inhibitors 3-isobutyl-1-methylxanthine (IBMX; 100 microM) and papaverine (100 microM) increased peak L-type Ca current (ICa) more than fivefold in a way similar to isoproterenol, forskolin, or intracellular adenosine 3',5'-cyclic monophosphate in guinea pig ventricular myocytes studied with the whole cell voltage-clamp technique at 22-24 degrees C. IBMX and papaverine could also induce a chloride current. Both drugs caused an apparent increase of ICa inactivation as revealed by 1) a negative shift of the ICa inactivation curve between -40 and 0 mV and 2) a suppression of the relief from inactivation at potentials positive to 0 mV. In the presence of IBMX or papaverine, the amplitudes of both the rapidly and slowly inactivating components of ICa were increased; the effect on the fast component was more pronounced. The drugs did not accelerate the inactivation time course of either component. Carbachol (CCh; 100 microM) reversed the increase in ICa produced by IBMX or papaverine. However, ICa could not be restored to its original magnitude on washout of CCh in the presence of phosphodiesterase inhibitors. In pertussis toxin-treated cells or in the presence of Ly-83583 (1-100 microM), IBMX retained its effect but CCh was unable to reduce ICa. Dialysis with guanosine 3',5'-cyclic monophosphate (cGMP; 0.1-100 microM) or 8-bromoguanosine 3',5'-cyclic monophosphate (30 microM) suppressed the increase of ICa by IBMX; the inhibition by cGMP was additive with that produced by CCh. We suggest that the major part of IBMX and papaverine effect is mediated by phosphodiesterase inhibition and involves an increase in intracellular adenosine 3',5'-cyclic monophosphate levels. CCh reversal of phosphodiesterase inhibitor action probably involves an elevation of cGMP levels and activation of cGMP-dependent protein kinase.
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PMID:Effects of PDE inhibitors and carbachol on the L-type Ca current in guinea pig ventricular myocytes. 769 86

cGMP-dependent protein kinase (cGMP kinase) has been implicated in the regulation of the cytosolic calcium level ([Ca2+]i). In Chinese hamster ovary (CHO) cells stably transfected with the cGMP kinase I alpha (CHO-cGK cells), cGMP kinase suppressed the thrombin-induced increase in inositol 1,4,5-trisphosphate and [Ca2+]i (Ruth, P., Wang, G.-X., Boekhoff, I., May, B., Pfeifer, A., Penner, R., Korth, M., Breer, H., and Hofmann, F. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 2623-2627). Cholecystokinin activated intracellular calcium release via a pertussis toxin (PTX)-insensitive pathway in CHO-cGK cells. cGMP kinase did not attenuate the CCK-stimulated [Ca2+]i. In contrast, cGMP kinase suppressed calcium influx stimulated by insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) via PTX-sensitive pathways. The effects of PTX and cGMP kinase on [Ca2+]i were not additive. 8-Bromo-cGMP had no effect on [Ca2+]i stimulated by IGF-1 or IGF-2 in wild type CHO cells. These results suggested that cGMP kinase inhibited the different signaling pathways by the phosphorylation of a PTX-sensitive G protein. cGMP kinase phosphorylated the alpha subunits of Gi1, Gi2, and Gi3 in vitro. Phosphorylation stoichiometry was 0.4 mol of phosphate/mol of G alpha i1 after reconstitution of heterotrimeric Gi1 in phospholipid vesicles. The alpha subunit of Gi was also phosphorylated in vivo. These results show that cGMP kinase blocks transduction of distinct hormone pathways that signal via PTX-sensitive Gi proteins.
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PMID:Cyclic GMP-dependent protein kinase blocks pertussis toxin-sensitive hormone receptor signaling pathways in Chinese hamster ovary cells. 772 18

Modulation of L-type calcium channels by the five cloned muscarinic receptors was studied by expression of the receptors in NIH 3T3 cells. Application of acetylcholine (ACh) to cells transfected with m1-m5 resulted in a reduction in the L-type calcium current amplitude. Elevations in intracellular cAMP concentrations induced by 8-bromo-cAMP or forskolin resulted in no discernible change in the L-type calcium current. In addition, treatment with Rp-adenosine 3',5'-cyclic monophosphothioate triethylamine (Rp-cAMPS), a protein kinase A (PKA) inhibitor, had no effect on the L-type currents. Conversely, application of phorbol dibutyrate, an activator of protein kinase C (PKC) or 8-bromo-cGMP, an activator of cGMP-dependent protein kinase (PKG), reduced the calcium currents. Incubation of the cells with KT5823, an inhibitor of PKG, resulted in a reduction of the response to 8-bromo-cGMP. The ACh-induced depression of L-type calcium current amplitude was sensitive to pertussis toxin (PTX) in cells transfected with the m2 or m4 receptor subtype. The m2-muscarinic-receptor-induced inhibition of the L-type calcium current was attenuated by preincubation of the cells with 8-bromo-cAMP and was unaffected by KT5823 or by calphostin C. The m1-muscarinic-receptor-induced inhibition of the L-type calcium conductance was insensitive to PTX treatment. However, the m1-induced response was blocked by preincubation of the cells with calphostin C. The present data indicate that the m2 (and possibly also the m4) muscarinic receptors inhibit the L-type calcium conductance by a reduction in cAMP concentration and that the m1 (and possibly also the m3 and m5) muscarinic receptors inhibit the L-type calcium channel via activation of PKC.
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PMID:Inhibition of the L-type calcium channel by the five muscarinic receptors (m1-m5) expressed in NIH 3T3 cells. 900 Apr 30

We have previously reported that the serine protease plasmin generated during contact activation of human plasma triggers biosynthesis of leukotrienes (LTs) in human peripheral monocytes (PMs), but not in polymorphonuclear neutrophils (PMNs). We now show that purified plasmin acts as a potent chemoattractant on human monocytes, but not on PMNs. Human plasmin or plasminogen activated with urokinase, but not active site-blocked plasmin or plasminogen, elicited monocyte migration across polycarbonate membranes. Similarly, stimulation of monocytes with plasmin, but not with active site-blocked plasmin or plasminogen, induced actin polymerization. As assessed by checkerboard analysis, the plasmin-mediated monocyte locomotion was a true chemotaxis. The plasmin-induced chemotactic response was inhibited by the lysine analog trans-4-(aminomethyl)cyclohexane-1-carboxylic acid (t-AMCA), which prevents binding of plasmin/ogen to the appropriate membrane binding sites. In addition, active site-blocked plasmin inhibited monocyte migration triggered by active plasmin. Further, plasmin-induced monocyte chemotaxis was inhibited by pertussis toxin (PTX) and 1-O-hexadecyl-2-O-methyl-rac-glycerol (HMG) and chelerythrine, two structurally unrelated inhibitors of protein kinase C (PKC). Plasmin, but not active site-blocked plasmin or plasminogen, triggered formation of cyclic guanosine monophosphate (cGMP) in monocytes. LY83583, an inhibitor of soluble guanylyl cyclase, inhibited both plasmin-induced cGMP formation and the chemotactic response. The latter effect could be antagonized by 8-bromo-cGMP. In addition, KT5823 and (Rp)-8-(p-chlorophenylthio)guanosine-3',5'-cyclic monophosphorothioate [(Rp)-8-pCPT-cGMPs], two structurally unrelated inhibitors of cGMP-dependent protein kinase, inhibited plasmin-mediated monocyte chemotaxis. Thus, beyond being a stimulus for lipid mediator release, plasmin is a potent and specific chemoattractant for human monocytes acting via a cGMP-dependent mechanism. Therefore, plasmin represents a proinflammatory activator for human monocytes.
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PMID:Plasmin is a potent and specific chemoattractant for human peripheral monocytes acting via a cyclic guanosine monophosphate-dependent pathway. 919 82

We have examined the effects of the tachykinin substance P on the action potential of lamprey mechanosensory dorsal cells. Substance P increased the spike duration and reduced the afterhyperpolarization. These effects were mimicked by stimulation of the dorsal root, which contains tachykinin-like immunoreactive fibres. The tachykinin antagonist spantide II blocked the effects of both substance P and dorsal root stimulation. The spike broadening was voltage-dependent, and was due to the reduction of a 4-aminopyridine-sensitive potassium conductance. The spike broadening was mimicked by G-protein activators and blocked by the G-protein inhibitor GDPbetaS. Pertussis toxin did not block the effects of substance P. The spike broadening was blocked by the protein kinase C and cAMP-dependent protein kinase inhibitor H7, and by the specific protein kinase C antagonist chelerythrine, but not by the cAMP and cGMP-dependent protein kinase inhibitor H8. The phorbol ester phorbol 12,13-dibutyrate mimicked and blocked the effects of substance P, supporting the role of protein kinase C in the spike modulation. The adenylate cyclase activator forskolin and the cAMP agonist SpcAMPs mimicked but did not block the effects of substance P on the spike duration, suggesting that protein kinase A also modulates the dorsal cell action potential, but that substance P acts independently of this pathway. Substance P also increased the excitability of the dorsal cells. This effect was blocked by 4-AP, PDBu and chelerythrine, but not by H8, suggesting that the increase in excitability shares the same intracellular and effector pathways as the spike broadening.
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PMID:Substance P modulates sensory action potentials in the lamprey via a protein kinase C-mediated reduction of a 4-aminopyridine-sensitive potassium conductance. 942 Nov 67

Neuronal alpha1E subunits are thought to form R-type Ca channels. When expressed in human embryonic kidney cells with M2 muscarinic acetylcholine receptors, Ca channels encoded by rabbit alpha1E exhibit striking biphasic modulation. Receptor activation first produces rapid inhibition of current amplitude and activation rate. However, in the continued presence of agonist, alpha1E currents subsequently increase. Kinetic slowing persists during this secondary stimulation phase. After receptor deactivation, kinetic slowing is quickly relieved, and current amplitude over-recovers before returning toward control levels. These features indicate that inhibition and stimulation of alpha1E are separate processes, with stimulation superimposed on inhibition. Pertussis toxin eliminates inhibition without affecting stimulation, demonstrating that inhibition and stimulation involve distinct signaling pathways. Neither inhibition nor stimulation is altered by coexpression of Ca channel beta2a or beta3 subunits. Stimulation is abolished by staurosporine and reduced by intracellular 5'-adenylylimidodiphosphate, suggesting that phosphorylation is required. However, stimulation does not seem to involve cAMP-dependent protein kinase, protein kinase C, cGMP-dependent protein kinase, tyrosine kinases, or phosphoinositide 3-kinases. Stimulation does not require a Ca signal, because it is not specifically altered by varying intracellular Ca buffering or by substituting Ba as the charge carrier. In contrast to those formed by alpha1E, Ca channels formed by alpha1A or alpha1B display only inhibition and no stimulation during prolonged activation of M2 receptors. The dual modulation of alpha1E may confer unique physiological properties on native R-type Ca channels. As one possibility, R-type channels may continue to mediate Ca influx during steady inhibition of N-type and P/Q-type channels by muscarinic or other receptors.
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PMID:Biphasic, opposing modulation of cloned neuronal alpha1E Ca channels by distinct signaling pathways coupled to M2 muscarinic acetylcholine receptors. 1043 38

Prostaglandin E(1) (PGE(1)) has cardioprotective effects on the ischemic-reperfused heart. To clarify the mechanisms underlying the protective action of PGE(1) on myocardium, we examined the effect of PGE(1) on the L-type Ca(2+) current (I(Ca)) using single atrial cells from rabbits. PGE(1) did not show a significant effect on basal I(Ca) but inhibited the I(Ca) prestimulated by isoproterenol (Iso, 30 nM). This inhibition was concentration dependent (EC(50) = 0.027 microM). Both sulprostone, a specific PGE receptor subtype (EP(1) and EP(3)) agonist, and 11-deoxy-PGE(1), an EP(3) agonist, inhibited the Iso-stimulated I(Ca), similar to PGE(1). Pretreatment with pertussis toxin (PTX) abolished the PGE(1) inhibition of I(Ca). Both the application of forskolin plus IBMX and intracellular dialysis with 8-bromoadenosine 3',5'-cyclic monophosphate eliminated the effect of PGE(1). PGE(1) did not show any further inhibition of I(Ca) when the effect of Iso was almost fully antagonized by acetylcholine. Methylene blue (guanylate cyclase inhibitor), KT-5823 (cGMP-dependent protein kinase inhibitor), and erythro-9-(2-hydroxy-3-nonyl)adenine (type II phosphodiesterase inhibitor) did not significantly change the inhibitory effect of PGE(1). These findings suggest that 1) PGE(1) inhibits Iso-stimulated I(Ca) by binding to the EP(3) receptor and 2) the PTX-sensitive and cAMP-dependent pathway is involved in the PGE(1) inhibition of I(Ca), but the nitric oxide-cGMP-dependent pathway is not. The PGE(1)-induced antiadrenergic effect shown in this study may contribute to the PGE(1) protection of myocardium against ischemia.
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PMID:EP receptor-mediated inhibition by prostaglandin E(1) of cardiac L-type Ca(2+) current of rabbits. 1051 71


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