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 stimulation of adenylate cyclase in various fractions of plasma membranes from rabbit small intestinal epithelium has been studied. In crude plasma membranes cholera toxin activated 5-fold at 10 micrograms/ml; vasoactive intestinal peptide (VIP) activated at concentration from 10(-8) to 10(-7) M, the maximal stimulation being 6-fold. Fluoride activated 10-fold at 10 mM. VIP-stimulated enzyme was inhibited by Ca2+ concentrations in the micromolar range. In the presence of calmodulin a biphasic response was obtained. At low Ca2+ concentration (4 x 10(-9)-6 x 10(-8) M) the enzyme was activated. As the Ca2+ concentration was increased the enzyme was concomitantly inhibited. We have investigated the mechanism by which cholera toxin activates intestinal adenylate cyclase. We have found that cholera toxin catalyzed incorporation of 32P into proteins located in the brush-border membrane whose molecular weights are in the range of 40-45kDa. These membranes bind [3H]GTP with a Kd of 1.8 x 10(-7) M. In contrast, basal lateral membranes do not contain any protein which becomes labeled in a toxin-dependent manner when incubated with cholera toxin and [32P]NAD. The modification of brush-border membrane protein occurred in spite of the absence of adenylate cyclase in these membranes. Adenylate cyclase in basal lateral membranes was poorly activated by cholera toxin as compared to crude plasma membranes. On the other hand, the ability of VIP and fluoride to activate the enzyme was enhanced in basal lateral membranes with respect to crude membranes. The results are discussed in relation to the mechanism by which cholera toxin activates adenylate cyclase in intact intestinal cells.
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PMID:Adenylate cyclase from rabbit small intestine: activation by cholera toxin and interaction with calcium. 400 77

The non-stimulated (basal) adenylate cyclase from bovine brain cortical membranes was purified 10 000-fold to apparent homogeneity by Lubrol PX extraction and two cycles of affinity chromatography on forskolin-agarose. The final product appears as one major band (mol. wt. 115 000) on SDS-polyacrylamide gels. Further identification was achieved by affinity cross-linking using Gs (stimulatory GTP-binding protein) that was [32P]ADP-ribosylated by cholera-toxin/[32P]NAD: cross-linking with disuccinimidyl suberate gave products with mol. wts. of 160 000, approximately 270 000 and higher. The distribution of these products was dependent on the concentration of cross-linker, suggesting aggregation of two or more adenylate cyclase complexes. In contrast, photo-affinity cross-linking with 4-azidobenzoyl-[32P]Gs yielded a single product with a mol. wt. of 160 000. Purified adenylate cyclase was completely unresponsive towards stimulators (GTP-analogs, NaF) acting via Gs suggesting that this component was removed during purification. On the other hand, stimulation by forskolin and by added activated Gs was preserved but to a smaller degree as compared with the crude enzyme. In contrast, the stimulation of Ca2+/calmodulin was only marginal. Purified adenylate cyclase reversibly bound to wheat germ agglutinin-Sepharose. This suggests that bovine brain adenylate cyclase is a glycoprotein.
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PMID:Adenylate cyclase from bovine brain cortex: purification and characterization of the catalytic unit. 409 92

Treatment of intact hepatocytes with islet-activating protein, from Bordatella pertussis, led to a pronounced increase in the ability of glucagon to raise intracellular cyclic AMP concentrations. Islet-activating protein, however, caused no apparent increase in the intracellular concentration of cyclic AMP under basal conditions. These effects were attributed to an enhanced ability of adenylate cyclase, in membranes from hepatocytes treated with islet-activating protein, to be stimulated by glucagon. When forskolin was used to amplify the basal adenylate cyclase activity, elevated GTP concentrations were shown to inhibit adenylate cyclase activity in membranes from control hepatocytes. This inhibitory effect of GTP was abolished if the hepatocytes had been pre-treated with islet activating protein. In isolated liver plasma membranes, islet-activating protein caused the NAD-dependent ribosylation of a Mr-40000 protein, the putative inhibitory guanine nucleotide regulatory protein, Ni. This effect was inhibited if guanosine 5'-[beta-thio]diphosphate rather than GTP was present in the ribosylation incubations. The ability of glucagon to uncouple or desensitize the activity of adenylate cyclase in intact hepatocytes was also blocked by pre-treating hepatocytes with islet-activating protein. Islet-activating protein thus heightens the response of hepatocytes to the stimulatory hormone glucagon. It achieves this by both inhibiting the expression of desensitization and also removing a residual inhibitory input expressed in the presence of glucagon.
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PMID:Islet-activating protein blocks glucagon desensitization in intact hepatocytes. 608 57

It has been proposed elsewhere [Meeker, R.B. & Harden, T. K. (1982) Mol. Pharmacol. 22, 310-319] that muscarinic cholinergic receptor-mediated attenuation of cAMP accumulation occurs through activation of phosphodiesterase in 1321N1 human astrocytoma cells. Pertussis toxin, which ADP-ribosylates the guanine nucleotide regulatory protein involved in receptor-mediated inhibition of adenylate cyclase (Ni), has been utilized to further differentiate between the mechanism of cholinergic regulation of cAMP metabolism in 1321N1 cells and the mechanism involving inhibition of adenylate cyclase in other tissues. Muscarinic receptor-mediated regulation of cAMP accumulation in NG108-15 neuroblastoma-glioma cells occurs through inhibition of adenylate cyclase. Pretreatment of these cells with pertussis toxin completely blocked the capacity of carbachol to attenuate cAMP accumulation. In contrast, concentrations of pertussis toxin two to three orders of magnitude higher than those effective in NG108-15 cells had no effect on muscarinic receptor-mediated attentuation of cAMP accumulation in 1321N1 cells. In addition, no effect of pertussis toxin was observed either on the control rate or the carbachol-stimulated rate of cAMP degradation measured directly in intact 1321N1 cells. A 41,000 Mr protein previously proposed to be the alpha subunit of Ni was labeled during incubation of a plasma membrane fraction from 1321N1 cells with [32P]NAD and pertussis toxin. Pertussis toxin is apparently active in 1321N1 cells, since this protein substrate was not labeled in plasma membrane preparations from cells previously incubated with toxin. Functional activity of Ni was demonstrated by the observation that guanosine 5'-[gamma-thio]triphosphate- and GTP-mediated inhibition of forskolin-stimulated adenylate cyclase activity occurred in cell-free preparations from 1321N1 cells. The inhibitory activity of these guanine nucleotides was lost in membrane preparations from pertussis toxin-treated cells. The data suggest that adenylate cyclase is not involved in cholinergic action in 1321N1 cells and, furthermore, Ni is not involved in muscarinic receptor-mediated activation of phosphodiesterase in these cells. Thus, pertussis toxin can be used to differentiate between two mechanisms of cholinergic regulation of cAMP metabolism.
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PMID:Pertussis toxin differentiates between two mechanisms of attenuation of cyclic AMP accumulation by muscarinic cholinergic receptors. 609 Nov 3

Adrenergic mechanism for phosphorylase activation was gradually converted from an alpha 1- to a beta 2-type during primary culture of rat hepatocytes. beta 2-Receptor-mediated cAMP generation was also much greater in 8-h cultured cells than in fresh cells. Incubation of hepatocyte membranes with [alpha-32P]NAD and the preactivated A-protomer (an active component) of islet-activating protein (IAP), pertussis toxin, resulted in the ADP-ribosylation of a specific IAP substrate protein (Mr = 41,000). This ADP-ribosylation diminished progressively when the membrane-donor hepatocytes had been cultured. The early diminution was interfered with by the addition of nicotinamide or isonicotinamide, a potent inhibitor of ADP-ribosyltransferase, to the culture medium. The decrease of the IAP substrate was well correlated with the potentiation of beta-adrenergic functions under various conditions of culture. beta-Receptor-mediated activation of GTP-dependent membrane adenylate cyclase was, but glucagon-induced activation was not enhanced by either prior culture of hepatocytes or prior exposure of membranes to the A-protomer of IAP. There was no further enhancement, however, when membranes from cultured cells were exposed to the active toxin. Thus, the IAP-susceptible inhibitory guanine nucleotide-regulatory protein is coupled to beta-adrenergic receptors in such a manner as to reduce the degree of activation of cyclase, and the decrease in this IAP substrate may be responsible, at least partly, for development of beta-receptor functions during culture of hepatocytes. Its possible relation to accompanying inhibition of alpha 1-receptor functions is discussed.
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PMID:Conversion of adrenergic mechanism from an alpha- to a beta-type during primary culture of rat hepatocytes. Accompanying decreases in the function of the inhibitory guanine nucleotide regulatory component of adenylate cyclase identified as the substrate of islet-activating protein. 609 73

In neuroblastoma-glioma (NG108-15) hybrid cells, opiates inhibit adenylate cyclase and stimulate a low Km GTPase. It has been postulated that the stimulation of GTPase plays a role in opiate inhibition of adenylate cyclase (Koski, G., and Klee, W. A. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 4185-4189). Treatment of NG108-15 cells with pertussis toxin attenuates receptor-mediated inhibition of adenylate cyclase. The toxin acts by catalyzing the ADP-ribosylation of a 41,000-dalton substrate believed to be a part of the receptor-adenylate cyclase complex. We have found that toxin treatment of NG108-15 results in inhibition of the opiate-stimulated GTPase. The concentration of toxin required for inhibition of this GTPase was similar to that needed for both attenuation of opiate inhibition of adenylate cyclase and ADP ribosylation of the 41,000-dalton substrate. Inhibition of the opiate-induced GTPase by pertussis toxin in isolated membranes required NAD, consistent with the hypothesis that this effect of the toxin resulted from ADP ribosylation of a protein component of the system. Since the opiate-stimulated GTPase is believed to play a role in the receptor-mediated decrease in adenylate cyclase activity, inhibition of this GTPase may be an important part of the mechanism by which the toxin interferes with opiate action on adenylate cyclase.
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PMID:Pertussis toxin inhibits enkephalin stimulation of GTPase of NG108-15 cells. 613 91

Incubation of photolyzed bovine rod outer segment (ROS) membranes with pertussis toxin led to an inhibition of GTPase activity in an NAD-dependent reaction. In the presence of [32P]NAD, pertussis toxin catalyzed the [32P]ADP-ribosylation of a 39-kDa ROS protein and the 39-kDa alpha-subunit of transducin purified from ROS membranes. The decrease in GTPase activity was paralleled by an increase in the extent of [32P]ADP-ribosylation of the 39-kDa ROS protein. [32P]ADP-ribosylation of the 39-kDa protein occurred in both photolyzed and dark ROS membranes. Neither ATP nor guanylyl imidodiphosphate were required for either ADP-ribosylation or inhibition of GTPase. It was demonstrated previously that choleragen catalyzed the NAD-dependent inhibition of ROS GTPase (Abood, M. E., Hurley, J. B., Pappone, M-C., Bourne, H. R., and Stryer, L. (1982) J. Biol. Chem. 257, 10540-10543). Choleragen-catalyzed inhibition of GTPase and [32P]ADP-ribosylation of the 39-kDa protein required guanylyl imidodiphosphate and did not occur in dark ROS membranes. The effects of choleragen and pertussis toxin were not additive. Incubation of ROS with choleragen or pertussis toxin prevented the subsequent [32P]ADP-ribosylation by the homologous but not the heterologous toxin, consistent with the hypothesis that the two toxins act at different sites on the 39-kDa protein. Pertussis toxin is known to ADP-ribosylate the inhibitory guanine nucleotide-binding subunit of adenylate cyclase (Ni) but not the stimulatory subunit (Ns); choleragen is known to ADP-ribosylate Ns but not Ni. Since both toxins ADP-ribosylate the same subunit of transducin, it appears that this protein may possess characteristics of both Ns and Ni.
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PMID:Inhibition of bovine rod outer segment GTPase by Bordetella pertussis toxin. 614 Nov 65

beta-Adrenergic receptors and the inhibitory GTP-binding protein, Gi of the adenylate cyclase system were reconstituted into phospholipid vesicles by the method described previously for reconstituting receptors and the stimulatory GTP-binding protein, Gs (Brandt, D. R., Asano, T., Pedersen, S. E., and Ross, E. M. (1983) Biochemistry 22, 4357-4362). In the receptor-Gi vesicles, beta-adrenergic agonists stimulated both the high-affinity binding of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) to Gi and GTPase activity to an extent similar to that observed in vesicles containing beta-adrenergic receptors and Gs. Stimulation required receptors and displayed appropriate beta-adrenergic specificity. The prior treatment of receptor-Gi vesicles with islet-activating protein (pertussis toxin) plus NAD markedly inhibited both the isoproterenol-stimulated binding of GTP gamma S and the isoproterenol-stimulated GTPase activity. No contamination of Gi by Gs was apparent. These data suggest that receptors that typically stimulate adenylate cyclase activity may also activate the inhibitory system, perhaps as one mechanism of desensitization.
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PMID:Activation of the inhibitory GTP-binding protein of adenylate cyclase, Gi, by beta-adrenergic receptors in reconstituted phospholipid vesicles. 614 12

The adenylate cyclase system consists of stimulatory and inhibitory hormone and drug receptors coupled through different GTP-binding proteins to a catalytic unit, responsible for the synthesis of cAMP from ATP. Pertussis toxin blocks the effect of inhibitory agonists on the catalytic unit by enzymatically inactivating the inhibitory GTP-binding protein (Gi). Study of the inhibitory arm of the cyclase system has been facilitated by the dissection of the overall process of hormonal inhibition of cAMP formation into a series of reactions characteristic of the individual protein components of this complex system; pertussis toxin has proven to be a useful tool with which to study these individual reactions. Exposure of cells or membranes to pertussis toxin in the presence of NAD results in ADP-ribosylation of a 41,000 Da subunit of Gi. ADP-ribosylation of Gi has a number of effects on the overall and partial reactions of the cyclase system, including a loss of a) hormonal inhibition of cAMP formation, b) hormonal stimulation of GTPase and c) agonist-induced release of membrane-bound guanyl nucleotides. In addition, in toxin-treated membranes, the affinity of inhibitory receptors for agonist but not antagonist is decreased with no significant change in receptor number.
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PMID:Pertussis toxin-catalyzed ADP-ribosylation: effects on the coupling of inhibitory receptors to the adenylate cyclase system. 615 92

Several changes were noted in the characteristics of the turkey erythrocyte beta-adrenergic receptor and in the kinetic properties of adenylate cyclase following pretreatment of erythrocyte membranes with isoproterenol and GMP, and thorough washing to remove these agents. The changes include modifications in the binding of agonist (isoproterenol) and in revelation of marked effects of GTP on agonist binding; reduction in the lag in Gpp(NH)p activation of adenylate cyclase; short lived activation by GTP which is lengthened by treatment with cholera toxin and NAD prior to pretreatment with isoproterenol and GMP. Treatment with cholera toxin also shortened the lag in activation by Gpp(NH)p and increased the steady state levels of activation by both Gpp(NH)p and GTP. The following conclusions can be drawn: (i) catecholamines, in the presence of a guanine nucleotide, stimulate the exchange of bound and exogenous nucleotide; (ii) the exchange reaction is involved in both the activation of adenylate cyclase and in the reciprocal effects of hormone and guanine nucleotides on each other's binding: (iii) the beta-adrenergic receptor and nucleotide regulatory components are linked in turkey erythrocyte membranes; (iv) both cholera toxin and catecholamines, although by different mechanisms, stimulate the exchange reaction at the nucleotide regulatory sites.
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PMID:The role of the guanine nucleotide exchange reaction in the regulation of the beta-adrenergic receptor and in the actions of catecholamines and cholera toxin on adenylate cyclase in turkey erythrocyte membranes. 624 4


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