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)

To help define essential interactions of cGMP with the catalytic site, we tested a series of cGMP analogs as competitive inhibitors of each cyclic nucleotide phosphodiesterase (PDE) family known to hydrolyze cGMP (PDE1, PDE2, PDE3, PDE5, and PDE6). IC50 values, relative to cGMP, were used to predict which functional groups of cGMP contribute to binding by the catalytic sites of each isozyme. The results indicate that the N1-nitrogen of cGMP contributes to binding at the catalytic site of all PDEs, probably as a hydrogen donor. All PDEs tested, with the exception of PDE2, also use the 6-oxo group, probably as a hydrogen acceptor. In contrast to other cGMP-binding enzymes, the 2-amino and 2'-hydroxyl groups of cGMP are not major requirements for binding to any PDE. The 8-bromo- and 8-p-chlorophenylthio-substituted analogs inhibit PDE1, PDE2, and PDE6 activity with high relative affinities, suggesting that these PDEs are not sterically hindered with bulky 8-position substitutions and that they do not preferentially bind the anti-conformation of cGMP. PDE3 and PDE5 have reduced apparent affinity for these analogs and therefore either are sterically hindered with these substitutions or bind cGMP in the anti-conformation. Overall, the data show substantial differences in structural requirements for cGMP binding to the catalytic sites of the different PDE families. Comparisons with published data show different structural requirements for binding to the catalytic, compared with noncatalytic, binding domains of PDEs. Even larger differences are seen between the requirements for binding to PDE catalytic sites and those for the cGMP-dependent protein kinase and the cGMP-gated cation channel.
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PMID:Characterization of cyclic nucleotide phosphodiesterases with cyclic GMP analogs: topology of the catalytic domains. 787 41

Early studies in whole heart indicated that cGMP antagonized the positive inotropic effects of catecholamines and cAMP. Since the L-type Ca2+ channel current (ICa) plays a predominant role in the initiation and development of cardiac electrical and contractile activities, regulation of ICa by cGMP pathways has received much attention over the last ten years. Patch-clamp measurements of ICa in isolated cardiac myocytes reveal at least three different cGMP effectors that may participate to different degrees in different animal species and cardiac tissues in the regulation of ICa by cGMP. In frog ventricular myocytes, cGMP inhibits ICa by stimulation of a cGMP-stimulated cAMP phosphodiesterase (PDE2), whereas in rat ventricular myocytes, cGMP predominantly inhibits ICa via a mechanism involving activation of a cGMP-dependent protein kinase (cGMP-PK). In guinea pig, frog and human cardiomyocytes, cGMP can also stimulate ICa via an inhibition of a cGMP-inhibited cAMP phosphodiesterase (PDE3). This effect is most predominant in human atrial myocytes and appears readily during an activation of the soluble guanylate cyclase activity by low concentrations of nitric oxide (NO)-donors. Biochemical characterization of the endogenous phosphodiesterases and cGMP-PK in purified cardiac myocytes provide further evidence in support of these mechanisms of cGMP action on ICa. However, the regulation of cGMP levels by a variety of agents is not always consistent with their effects on contractility. In particular, the participation of cGMP and NO pathways in the regulation of cardiac ICa and contractility by acetylcholine is still questionable.
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PMID:[Regulation of cardiac calcium current by cGMP/NO route]. 886 31

Sulindac sulfone (exisulind), although a nonsteroidal anti-inflammatory drug derivative, induces apoptosis in tumor cells by a mechanism that does not involve cyclooxygenase inhibition. SW480 colon tumor cells contain guanosine 3',5'-monophosphate (cGMP) phosphodiesterase (PDE) isoforms of the PDE5 and PDE2 gene families that are inhibited by exisulind and new synthetic analogues. The analogues maintain rank order of potency for PDE inhibition, apoptosis induction, and growth inhibition. A novel mechanism for exisulind to induce apoptosis is studied involving sustained increases in cGMP levels and cGMP-dependent protein kinase (PKG) induction not found with selective PDE5 or most other PDE inhibitors. Accumulated beta-catenin, shown to be a substrate for PKG, is decreased by exisulind, suggesting a mechanism to explain apoptosis induction in neoplastic cells harboring adenomatous polyposis coli gene mutations.
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PMID:Exisulind induction of apoptosis involves guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition, protein kinase G activation, and attenuated beta-catenin. 1091 34

1. The regulation of the L-type Ca(2+) current (I(Ca)) by intracellular cGMP was investigated in human atrial myocytes using the whole-cell patch-clamp technique. 2. Intracellular application of 0.5 microM cGMP produced a strong stimulation of basal I(Ca) (+64 +/- 5 %, n = 60), whereas a 10-fold higher cGMP concentration induced a 2-fold smaller increase (+36 +/- 8 %, n = 35). 3. The biphasic response of I(Ca) to cGMP was not mimicked by the cGMP-dependent protein kinase (PKG) activator 8-bromoguanosine 3',5' cyclic monophosphate (8-bromo-cGMP, 0.5 or 5 microM), and was not affected by the PKG inhibitor KT 5823 (100 nM). 4. In contrast, cGMP stimulation of I(Ca) was abolished by intracellular perfusion with PKI (10 microM), a selective inhibitor of the cAMP-dependent protein kinase (PKA). 5. Selective inhibition of the cGMP-inhibited phosphodiesterase (PDE3) by extracellular cilostamide (100 nM) strongly enhanced basal I(Ca) in control conditions (+78 +/- 13 %, n = 7) but had only a marginal effect in the presence of intracellular cGMP (+22 +/- 7 % in addition to 0.5 microM cGMP, n = 11; +20 +/- 22 % in addition to 5 microM cGMP, n = 7). 6. Application of erythro-9-[2-hydroxy-3-nonyl]adenine (EHNA, 30 microM), a selective inhibitor of the cGMP-stimulated phosphodiesterase (PDE2), fully reversed the secondary inhibitory effect of 5 microM cGMP on I(Ca) (+99 +/- 16 % stimulation, n = 7). 7. Altogether, these data indicate that intracellular cGMP regulates basal I(Ca) in human atrial myocytes in a similar manner to NO donors. The effect of cGMP involves modulation of the cAMP level and PKA activity via opposite actions of the nucleotide on PDE2 and PDE3.
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PMID:Cyclic GMP regulation of the L-type Ca(2+) channel current in human atrial myocytes. 1138 95

Treatment of cultured adult rat cardiac fibroblasts with interleukin-1beta (IL-1beta) induces the inducible nitric oxide synthase (iNOS) expression, increases nitric oxide (NO) and cGMP production, and attenuates cAMP accumulation in response to isoproterenol by ~50%. Reduced cAMP accumulation is due to NO production: the effect is mimicked by NO donors and prevented by N(G)-monomethyl-L-arginine, an NOS inhibitor. Effects of NO are not restricted to the beta-adrenergic response; the response to forskolin is similarly diminished. NO donors only slightly (12%) decrease forskolin-stimulated adenylyl cyclase (AC) activity in cardiac fibroblast plasma membranes, suggesting that the main effect of NO is not a direct one on AC. An inhibitor of soluble guanylyl cyclase inhibits the effects of IL-1beta and NO donors; inhibition of cGMP-dependent protein kinase is without effect. 3-Isobutyl-1-methylxanthine, a nonspecific phosphodiesterase (PDE) inhibitor, and erythro-9-(2-hydroxy-3-nonyl)adenine, a specific inhibitor of the cGMP-stimulated PDE (PDE2), completely restore cAMP accumulation in sodium nitroprusside-treated fibroblasts and largely reverse the attenuated response in IL-1beta-treated fibroblasts. Although NO reportedly acts by reducing AC activity in some cells, in cardiac fibroblasts NO production decreases cAMP accumulation largely by the cGMP-mediated activation of PDE2.
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PMID:Attenuation of cAMP accumulation in adult rat cardiac fibroblasts by IL-1beta and NO: role of cGMP-stimulated PDE2. 1210 56

The rat formalin assay was used to assess effects of the cyclic guanosine mono-phosphate (cGMP) analog, 8-bromo-cGMP on nociception and cGMP dependent protein kinase I (protein kinase G; PKG-I) expression in lumbar spinal cord. Intrathecal (i.t.) delivery of low doses of 8-bromo-cGMP (0.1-0.25 micromol) reduced nociceptive behavior and formalin-induced upregulation of PKG-I in the spinal cord. Medium doses (0.5-1 micromol i.t.) had no effect and high doses (2.5 micromol i.t.) caused hyperalgesia associated with a further increase of PKG-I expression and a PKG-I clip. To explain these dose-dependent contrary effects we assessed the potential involvement of various cGMP targets: protein kinase G, cyclic nucleotide gated cation channels (CNGs), phosphodiesterases (PDE2 and PDE3) and AMPA-receptors. The PKG inhibitor, Rp-8-bromo-cGMPS did not antagonize the antinociceptive effects of 8-bromo-cGMP but caused antinociception itself. Inhibitors of CNGs, PDE2 and PDE3 had no effect on formalin evoked nociceptive behavior. S-AMPA however, antagonized the antinociceptive effects of 8-bromo-cGMP. Since AMPA receptor currents were found to be reduced by 8-bromo-cGMP in vitro a direct or indirect reduction of AMPA receptor currents might possibly contribute to the antinociceptive effects of 8-bromo-cGMP. On the other hand, 8-bromo-cGMP evoked antinociception appears to be largely independent of PKG-I, CNGs, PDE2 and PDE3. The antinociceptive effects of the PKG inhibitor suggest that a strong PKG activation may be responsible for 'high dose' 8-bromo-cGMP evoked hyperalgesia.
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PMID:Dual effects of spinally delivered 8-bromo-cyclic guanosine mono-phosphate (8-bromo-cGMP) in formalin-induced nociception in rats. 1238 31

Vasodilator-stimulated phosphoprotein (VASP) is a regulator of actin dynamics in platelets and a common substrate of both cAMP- and cGMP-dependent protein kinases (PKA and PKG). Elevations of the cAMP and cGMP concentration have been shown to inhibit platelet aggregation. Intracellular levels of cAMP and cGMP are regulated by the synthesizing system of adenylate cyclases, and hydrolysis by cyclic nucleotide phosphodiesterases (PDEs). The present study examined the effect of the anti-platelet drug, cilostazol, which inhibits PDE3 activity, on VASP phosphorylation in platelets. VASP phosphorylation was examined by immunoblotting with an anti-VASP antibody, M4, and an anti-phospho-VASP antibody, 16C2. Cilostazol phosphorylated VASP at both Ser157 and Ser239 in a concentration-dependent manner, but EHNA (PDE2 inhibitor), dipyridamole and zaprinast (PDE5 inhibitors) did not. Forskolin (adenylate cyclase activator) and sodium nitroprusside (SNP, NO donor) resulted in the VASP phosphorylation, with increase in the cAMP and cGMP level, respectively. Cilostazol increased cAMP, but not cGMP levels, in platelets. EHNA, zaprinast and dipyridamole, had no effect on cAMP and cGMP levels. The PKA/PKG inhibitor, H-89, inhibited VASP phosphorylation by cilostazol. These results demonstrated that cilostazol phosphorylates VASP through the PDE3 inhibition, increase of cAMP level, and PKA activation in platelets.
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PMID:Phosphorylation of the vasodilator-stimulated phosphoprotein (VASP) by the anti-platelet drug, cilostazol, in platelets. 1460 52

The present study addressed the question of whether nitric oxide (NO) participates in regulation of osmotic water permeability in the urinary bladder of the frog Rana temporaria L. Experiments were carried out on isolated, paired hemi-bladders filled with amphibian Ringer solution diluted 1:10 with distilled water. Sodium nitroprusside (SNP, 125-250 micro M), an NO donor, markedly attenuated the increase of osmotic water flow elicited by arginine-vasotocin (AVT) (AVT 10(-10) M: 2.20+/-0.26; AVT plus 200 micro M SNP: 1.21+/-0.15 micro l/min cm(2), n=20, P<0.001). This effect of SNP was apparent only in the presence of 50 micro M zaprinast, an inhibitor of the cGMP-specific phosphodiesterase-5 (PDE5). In the presence of zaprinast, SNP elevated cGMP production significantly both in control and AVT-stimulated urinary bladders, but had no effect on the level of cAMP (AVT 5 x 10(-10) M: 7.6+/-0.6; AVT plus SNP 200 micro M: 7.5+/-0.4 pmol/mg protein, n=8, N.S.). 1 H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ, 25-100 micro M), an inhibitor of soluble guanylate cyclase, enhanced the AVT-induced water flow, decreased the SNP-stimulated increase of cGMP in the bladder tissue and almost abolished the inhibitory effect of SNP on the AVT-induced hydroosmotic response. 8-( p-Chlorophenylthio)-cGMP (8-pCPT-cGMP, 25 or 50 micro M), a membrane-permeable cGMP analogue specific for cGMP-dependent protein kinase (PKG), inhibited, whereas 2 micro M KT-5823, an inhibitor of PKG, significantly stimulated the increase of water flow induced by AVT. The inhibitory effect of SNP on AVT-induced water flow was almost completely reversed by KT-5823, but not by 50-100 micro M erythro-9-[2-hydroxy-3-nonyl]adenine (EHNA), an inhibitor of cGMP-activated PDE2. Immunohistochemistry of urinary bladder slices with antibodies against different types of NO synthase (NOS) revealed a positive immunostaining for neuronal NOS (nNOS) in the mucosal epithelium. These results suggest that in the frog urinary bladder endogenous NO is involved in regulation of water osmotic permeability. NO inhibits the AVT-induced increase of water flow at least partly by activation of PKG, which interferes with the hydroosmotic effect of AVT probably at (a) post-cAMP step(s).
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PMID:Nitric oxide inhibits arginine-vasotocin-induced increase of water osmotic permeability in frog urinary bladder. 1472 76

Biochemical studies have established the presence of a NO pathway in the heart, including sources of NO and various effectors. Several cardiac ion channels have been shown to be modified by NO, such as L-type Ca(2+), ATP-sensitive K(+), and pacemaker f-channels. Some of these effects are mediated by cGMP, through the activity of three main proteins: the cGMP-dependent protein kinase (PKG), the cGMP-stimulated phosphodiesterase (PDE2) and the cGMP-inhibited PDE (PDE3). Other effects appear independent of cGMP, as for instance the NO modulation of the ryanodine receptor-Ca(2+) channel. In the case of the cardiac L-type Ca(2+) channel current (I(Ca,L)), both cGMP-dependent and cGMP-independent effects have been reported, with important tissue and species specificity. For instance, in rabbit sinoatrial myocytes, NO inhibits the beta-adrenergic stimulation of I(Ca,L) through activation of PDE2. In cat and human atrial myocytes, NO potentiates the cAMP-dependent stimulation of I(Ca,L) through inhibition of PDE3. In rabbit atrial myocytes, NO enhances I(Ca,L) in a cAMP-independent manner through the activation of PKG. In ventricular myocytes, NO exerts opposite effects on I(Ca,L): an inhibition mediated by PKG in mammalian myocytes but by PDE2 in frog myocytes; a stimulation attributed to PDE3 inhibition in frog ventricular myocytes but to a direct effect of NO in ferret ventricular myocytes. Finally, NO can also regulate cardiac ion channels by a direct action on G-proteins and adenylyl cyclase.
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PMID:Species- and tissue-dependent effects of NO and cyclic GMP on cardiac ion channels. 1592 94

NMDA receptor-induced cAMP and cGMP are selectively hydrolyzed by PDE4 and PDE2, respectively, in rat primary cerebral cortical and hippocampal cultures. Because cAMP levels regulate the expression of PDE4 in rat primary cortical cultures, we examined the manner in which NMDA receptor activity regulates the age-dependent increase in the expression of PDE4A observed in vivo and in vitro. Inhibiting the activity of NR2B subunit with ifenprodil blocked NMDA receptor-induced cGMP synthesis and increased NMDA receptor-induced cAMP levels in a manner that reduced PDE4 activity. Therefore, NR1/NR2B receptor-induced cGMP signaling is involved in an acute cross-talk regulation of NR1/NR2A receptor-induced cAMP levels, mediated by PDE4. Chronic inhibition of NMDA receptor activity with MK-801 reduced PDE4A1 and PDE4A5 expression and activity in a time-dependent manner; this effect was reversed by adding the PKA activator dbr-cAMP. Inhibiting GABA receptors with bicuculline increased NMDA receptor-induced cAMP synthesis and PDE4A expression in cultures treated between DIV 16 and DIV 21 but not in cultures treated between DIV 8 and DIV 13. This effect was due to a high tone of NMDA receptor-induced cGMP in younger cultures, which negatively regulated the expression of PDE4A by a PKG-mediated process. The present results are consistent with behavioral data showing that both PDE4 and PDE2 are involved in NMDA receptor-mediated memory processes.
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PMID:Changes in NMDA receptor-induced cyclic nucleotide synthesis regulate the age-dependent increase in PDE4A expression in primary cortical cultures. 1740 67


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