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:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The selective 5-HT1A receptor ligand ipsapirone (IPS) induces corticotropin (ACTH) and cortisol secretion in humans. To explore 5-HT1A receptor-mediated hypothalamic-pituitary-adrenal (HPA) system activation in depression, 24 subjects (12 patients with unipolar depression and 12 individually matched controls) were given 0.3 mg/kg IPS or placebo in random order. Compared with controls, the depressed patients exhibited significantly decreased ACTH and cortisol responses to IPS in association with increased basal cortisol secretion. The impaired HPA response following 5-HT1A receptor challenge in unipolar depression could have resulted from glucocorticoid-dependent subsensitivity of the (post-synaptic) 5-HT1A receptor itself and/or from a defective postreceptor signaling pathway [inhibitory guanine nucleotide-binding protein (Gi)-adenylate cyclase complex function], thus supporting the hypothesis that a disintegrated 5-HT and HPA system interaction may be present in depression. Future studies of the HPA response to direct-acting 5-HT1A ligands, such as IPS, should facilitate the assessment of 5-HT/HPA system integrity in various affective disorders and its involvement in psychotropic drug effects.
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PMID:5-HT1A receptor responsivity in unipolar depression. Evaluation of ipsapirone-induced ACTH and cortisol secretion in patients and controls. 197 79

This study tests the hypothesis that atrial natriuretic factor (ANF) and C-ANF(4-23)-NH2 (C-ANF) augment cGMP generation and inhibit both cAMP generation and depolarization-induced catecholamine release in nerve growth factor treated pheochromocytoma cells by a pertussis toxin (PTX)-sensitive mechanism. Synthetic rat ANF(99-126) and the clearance receptor antagonist C-ANF (10(-12)-10(-9) M) inhibited basal and 5 microM vasoactive intestinal peptide (VIP)-induced cAMP generation in a concentration-dependent manner. These actions of ANF and C-ANF were blocked by 12-18 h pretreatment with PTX (100 ng/ml), suggesting ANF receptor coupling to adenylate cyclase via an inhibitory guanine nucleotide-binding protein. Both ANF (10(-11)-10(-9) M) and C-ANF (10(-11)-10(-8) M) also inhibited K(+)-induced catecholamine release in a concentration-dependent manner. ANF (10(-11)-10(-8) M) increased cGMP generation in a concentration-dependent manner but C-ANF did not. The accumulation of cGMP in response to ANF was not altered by treatment with PTX. Therefore, PTX dissociated the increased concentrations of cGMP from the ANF-mediated depression of evoked catecholamine release. C-ANF also dissociated elevations in cGMP concentrations from an ANF-mediated attenuation of evoked catecholamine release. The results of this study indicate that ANF inhibits adrenergic neurotransmission independent of guanylate cyclase.
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PMID:Neuromodulatory effects of atrial natriuretic factor are independent of guanylate cyclase in adrenergic neuronal pheochromocytoma cells. 197 29

In heart failure, an increase in the activity of the sympathetic nervous system takes place to maintain perfusion pressure to vital organs, resulting in increased levels of noradrenaline in the blood of these patients. This permanent stimulation produces a down-regulation of cardiac beta-adrenoceptors. Since noradrenaline acts primarily on the cardiac beta 1-adrenoceptor subtype, beta 1-adrenoceptors decrease in number, whereas the beta 2-adrenoceptor subpopulation remains unchanged in most instances. Consequently, the positive inotropic response to beta-adrenoceptor agonists is diminished. However, there is also a decrease in the positive inotropic effect of beta 2-adrenoceptor agonists, histamine and cAMP-phosphodiesterase inhibitors such as milrinone, whereas the positive inotropic effect of cAMP-independent Na(+)-channel activators such as DPI 206-106 and the effects of cardiac glycosides are not diminished. These observations suggest a more generalised alteration of the cAMP-adenylate cyclase system in the failing heart. Stimulatory guanine nucleotide-binding protein (Gs) couples receptors to adenylate cyclase that stimulate cAMP formation, such as beta-adrenoceptors, histamine receptors and glucagon receptors. In the failing human heart, Gs content has been reported to remain unchanged as compared with that in non-failing myocardium. However, there is a 35%-40% increase in inhibitory guanine nucleotide-binding proteins (Gi), which are involved in the receptor-mediated inhibition of adenylate cyclase. Taken together, two defects of the cAMP-adenylate cyclase system have been identified: an increase in Gi content and a decrease in the number of beta-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Alterations of the cAMP-adenylate cyclase system in the failing human heart. Consequences for the therapy with inotropic drugs]. 197 43

The expression of guanine nucleotide-binding protein (G-protein) genes (Gs alpha, Go alpha, Gi alpha 1, Gi alpha 2, and Gi alpha 3) was examined in the ventricle of cardiomyopathic Syrian hamsters of the Bio14.6 strain (10-35 weeks old). Northern blot analysis of total cellular RNA revealed that all G-protein genes except Gi alpha 1 were expressed in the ventricle of Syrian hamsters. Gs alpha and Gi alpha 2 genes were abundantly expressed. The expression levels of the Gs alpha and Gi alpha 2 messenger RNAs in Bio14.6 ventricles were lower than the levels in ventricles of the F1B hamster strain; the abundance of Go alpha and Gi alpha 3 messenger RNAs did not change markedly. Moreover, the messenger RNA levels of Gs alpha and Gi alpha 2 decreased as the stage of cardiomyopathy progressed. Since G-proteins are linked to adenylate cyclase, these alterations of G-protein messenger RNA levels may be related to reduced contractility of cardiomyopathic heart.
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PMID:Messenger RNA levels of guanine nucleotide-binding proteins are reduced in the ventricle of cardiomyopathic hamsters. 211 26

The proximal tubule of the kidney represents an important location where adenylate cyclase regulates salt and water transport; yet a detailed characterization of the distribution and classification of guanine nucleotide-binding protein (G protein) and adenylate cyclase is lacking. We used purified brush border (20-fold) and basolateral membranes (14-fold) to characterize parathyroid hormone- and G protein-regulated adenylate cyclase and G-protein distribution. Adenylate cyclase was predominantly localized to basolateral membranes, while the 46-kDa alpha subunit of the stimulatory G protein (Gs) was 2-fold higher in brush border membranes than in basolateral membranes. The alpha subunit of the inhibitory G protein (Gi; 41 kDa) was equally distributed on immunoblotting but was 2-fold higher in brush border membranes than in basolateral membranes on radiolabeling with pertussis toxin. A 42-kDa cholera toxin substrate that cross-reacted with antisera to the common alpha subunit of G proteins and to Gs on immunoblotting and that was not immunoprecipitated with two Gi antisera was the most abundant alpha subunit and comprised approximately 1% of the total membrane proteins. These observations suggest that G proteins are important regulators of proximal tubular transport independent of adenylate cyclase.
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PMID:Proximal tubular epithelial cells possess a novel 42-kilodalton guanine nucleotide-binding regulatory protein. 212 Jul 2

Although adenosine is known to activate K+ conduction in atrial tissue, there is still debate as to the involvement of cAMP-dependent mechanisms. In isolated adult guinea pig atrial myocytes, we demonstrate that the highly A1-selective adenosine receptor agonist 2-chloro-N6-cyclopentyladenosine reduced basal cAMP levels by 30-40% in the absence and presence of the nonxanthine phosphodiesterase inhibitor Ro 20-1724. Isoprenaline caused a concentration-dependent increase in cAMP levels, which was more pronounced in the presence of the phosphodiesterase inhibitor. Several adenosine derivatives suppressed the isoprenaline-induced cAMP increase by approximately 80%. The rank order of potency was 2-chloro-N6-cyclopentyladenosine (IC50, 93 nM) greater than (R)-N6-phenylisopropyladenosine (IC50, 309 nM) greater than 5'-N-ethylcarboxamidoadenosine (IC50, 813 nM) much greater than (S)-N6-phenylisopropyladenosine (IC50, 26,300 nM). A similar but complete suppression of the isoprenaline-induced cAMP increase was produced by the muscarinic receptor agonist carbachol (IC50, 398 nM), which like adenosine is known to activate atrial K+ channels. The A1-adenosine receptor-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine antagonized the effect of 2-chloro-N6-cyclopentyladenosine concentration-dependently, with a KB value of 9.6 nM. In atrial myocytes isolated from guinea pigs pretreated with pertussis toxin, the inhibitory effects of adenosine analogs on basal and isoprenaline-stimulated cAMP accumulation were markedly attenuated. It is concluded that the adenosine receptor in guinea pig atrial myocytes, which is known to be linked to K+ channels, is also coupled to adenylate cyclase via a pertussis toxin-sensitive guanine nucleotide-binding protein and shows the characteristics of the A1-adenosine receptor subtype.
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PMID:Pharmacological characterization of the adenylate cyclase-coupled adenosine receptor in isolated guinea pig atrial myocytes. 216 17

We identified receptors for neuropeptide Y (NPY) on an established human neuroblastoma cell line, SK-N-MC, which are functionally coupled to adenylate cyclase through the inhibitory guanine nucleotide-binding protein of adenylate cyclase, Gi. Intact SK-N-MC cells bound radiolabeled NPY with a KD of 2 nM and contained approximately 83,000 receptors/cell. Unlabeled porcine and human NPY and structurally related porcine peptide YY (PYY) competed with labeled NPY for binding to the receptors. NPY inhibited cyclic AMP accumulation in SK-N-MC cells stimulated by isoproterenol, dopamine, vasoactive intestinal peptide, cholera toxin, and forskolin. NPY inhibited isoproterenol-stimulated cyclic AMP production in a dose-dependent manner, with half-maximal inhibition at 0.5 nM NPY. Porcine and human NPY and porcine PYY gave similar dose-response curves. NPY also inhibited basal and isoproterenol-stimulated adenylate cyclase activity in disrupted cells. Pertussis toxin treatment of the cells completely blocked the ability of NPY to inhibit cyclic AMP production and adenylate cyclase activity. The toxin catalyzed the ADP-ribosylation of a 41-kDa protein in SK-N-MC cells that corresponds to Gi. The receptors on SK-N-MC cells appeared to be specific for NPY, as other neurotransmitter drugs, such as alpha-adrenergic, dopaminergic, muscarinic, and serotonergic antagonists, did not compete for either NPY binding or NPY inhibition of adenylate cyclase. Thus, SK-N-MC cells may be a useful model for investigating NPY receptors and NPY-mediated signal transduction.
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PMID:Characterization of functional neuropeptide Y receptors in a human neuroblastoma cell line. 216 71

The Nb2 T lymphoma is unique in that these lymphocytes proliferate in response to prolactin as well as in response to interleukin-2. In this study, we have examined the responsiveness of the adenylate cyclase system in Nb2 cells and the role of this signaling system in regulating proliferation and protein phosphorylation. An analog of cAMP inhibited prolactin-stimulated proliferation and blocked a prolactin-induced decrease in protein phosphorylation. Forskolin, a potent activator of adenylate cyclase in T lymphocytes, did not elevate cAMP levels in Nb2 cells and was not an effective inhibitor of prolactin-induced proliferation. In fact, one preparation of forskolin stimulated proliferation of quiescent Nb2 cells. Like forskolin, prostaglandin E2 did not stimulate cAMP production in Nb2 cells even though it increased cAMP in a preparation of rat peripheral blood lymphocytes. Cholera toxin appeared to ADP-ribosylate a stimulatory guanine nucleotide-binding protein in Nb2 cells, but the toxin did not increase intracellular levels of cAMP nor was it a potent anti-mitogenic agent. Pertussis toxin, an agent that can increase cAMP production through suppression of the inhibitory guanine nucleotide-binding protein, exerted only minor anti-proliferative actions on prolactin-stimulated Nb2 cells. These data suggest that cAMP inhibits Nb2 cell proliferation and prolactin-induced changes in protein phosphorylation but that the adenylate cyclase system in our clone of Nb2 cells responds poorly to agents that normally increase cAMP.
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PMID:Growth and protein phosphorylation in the Nb2 lymphoma: effect of prolactin, cAMP, and agents that activate adenylate cyclase. 216 97

Differentiation of 3T3-L1 cells from fibroblasts to adipocytes is accompanied by increased adenylate cyclase response to lipolytic agents. We used pertussis toxin and specific antibodies to measure the inhibitory guanine nucleotide-binding protein, Gi, and the novel G-protein, Go, in membranes from 3T3-L1 cells. Pertussis toxin-dependent labeling of a 39-40 kDa protein showed an initial 30% rise, followed by an 80% fall during differentiation. Immunoblots showed that 3T3-L1 cells contain Go, as well as Gi, and that changes in the former parallel the changes in pertussis toxin labeling. Changes in Gi and GO may contribute to altered adenylate cyclase response during 3T3-L1 cell differentiation.
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PMID:Changes in the guanine nucleotide-binding proteins, Gi and Go, during differentiation of 3T3-L1 cells. 242 Jun 44

Jakobs, Bauer & Watanabe [(1985) Eur. J. Biochem. 151, 425-430] reported that treatment of platelets with phorbol 12-myristate 13-acetate (PMA) prevented GTP- and agonist-induced inhibition of adenylate cyclase in membranes from the platelets. This was attributed to the phosphorylation of the inhibitory guanine nucleotide-binding protein (Gi) by protein kinase C. In the present study, the effects of PMA on cyclic [3H]AMP formation and protein phosphorylation were studied in intact human platelets labelled with [3H]adenine and [32P]Pi. Incubation mixtures contained indomethacin to block prostaglandin synthesis, phosphocreatine and creatine kinase to remove ADP released from the platelets, and 3-isobutyl-1-methylxanthine to inhibit cyclic AMP phosphodiesterases. Under these conditions, PMA partially inhibited the initial formation of cyclic [3H]AMP induced by prostaglandin E1 (PGE1), but later enhanced cyclic [3H]AMP accumulation by blocking the slow decrease in activation of adenylate cyclase that follows addition of PGE1. PMA had more marked and exclusively inhibitory effects on cyclic [3H]AMP formation induced by prostaglandin D2 and also inhibited the action of forskolin. Adrenaline, high thrombin concentrations and, in the absence of phosphocreatine and creatine kinase, ADP inhibited cyclic [3H]AMP formation induced by PGE1. The actions of adrenaline and thrombin were attenuated by PMA, but that of ADP was little affected, suggesting differences in the mechanisms by which these agonists inhibit adenylate cyclase. sn-1,2-Dioctanoylglycerol (diC8) had effects similar to those of PMA. The actions of increasing concentrations of PMA or diC8 on the modulation of cyclic [3H]AMP formation by PGE1 or adrenaline correlated with intracellular protein kinase C activity, as determined by 32P incorporation into the 47 kDa substrate of the enzyme. Parallel increases in phosphorylation of 20 kDa and 39-41 kDa proteins were also observed. Platelet-activating factor, [Arg8]vasopressin and low thrombin concentrations, all of which inhibit adenylate cyclase in isolated platelet membranes, did not affect cyclic [3H]AMP formation in intact platelets. However, the activation of protein kinase C by these agonists was insufficient to account for their failure to inhibit cyclic [3H]AMP formation. Moreover, high thrombin concentrations simultaneously activated protein kinase C and inhibited cyclic [3H]AMP formation. The results show that, in the intact platelet, the predominant effects of activation of protein kinase C on adenylate cyclase activity are inhibitory, suggesting actions additional to inactivation of Gi.
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PMID:Effects of activation of protein kinase C on the agonist-induced stimulation and inhibition of cyclic AMP formation in intact human platelets. 244 6


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