Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To assess whether receptor binding is sufficient to initiate vasopressin receptor endocytosis in cells expressing the vasopressin V1 or V2 receptors, we synthesized a novel fluorescent-labeled vasopressin analog, [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid), 2-(O-ethyl)-D-tyrosine, 4-valine, 8-lysine-N6-carboxytetramethylrhodamine] vasopressin (R-CLVP), that binds to vasopressin receptors but does not activate intracellular events such as the mobilization of intracellular calcium or the activation of adenylate cyclase. We compared the manner in which this analog was endocytosed in cells expressing V1 (A-10, rat smooth muscle cells) or V2 (LLC-PK1, porcine kidney cells) receptors with that of a full agonist, [1-(beta-mercaptopropionic acid), 8-lysine-N6-carboxytetramethylrhodamine] vasopressin (R-MLVP) [Lutz et al. (1990) J. Biol. Chem. 265, 4657-4663; Lutz et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87,6507-6511]. We showed that R-CLVP bound to both types of receptors with good affinity. It failed to increase cyclic AMP concentrations in LLC-PK1 cells and did not increase the mobilization of intracellular calcium in A-10 cells. It bound to the surface of both these cell types in a diffuse manner and it did not undergo receptor endocytosis in either cell type. In contrast, R-MLVP, an agonist that bound to both receptor subtypes and elicited changes in intracellular cyclic AMP and calcium, bound to the surface of these cells in a diffuse manner at early times after exposure, and rapidly underwent endocytosis. We conclude that binding of vasopressin to its receptors alone is insufficient to cause receptor endocytosis, and other events distal to the receptor are required to initiate endocytosis. R-CLVP should be a useful analog in determining the factors responsible for initiating receptor endocytosis.
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PMID:A vasopressin analog that binds but does not activate V1 or V2 vasopressin receptors is not internalized into cells that express V1 or V2 receptors. 130 61

Treatment of rat thoracic aortic smooth muscle cells (A-10) with sodium fluoride (NaF) resulted in inhibition of beta-adrenergic agonist--and forskolin-induced cAMP and ANF-induced cGMP accumulation and stimulation of diacylglycerol (DAG) accumulation. The concentration of NaF and treatment times required to mediate these inhibitory effects were similar to those observed for stimulation of DAG accumulation. Treatment of the cells with NaF also resulted in a loss of [3H]phorbol dibutyrate (PDBu) binding in the cytosolic portion of the cells. In addition, pre-treatment of the cells with NaF resulted in an increase in the adenylate cyclase activity. Pertussis toxin (PT) pre-treatment of the cells did not significantly affect NaF-mediated effects. Pre-treatment of the cells with protein kinase C (PKC) inhibitor staurosporin partially reversed NaF-mediated inhibition of cyclic nucleotides accumulation. These data suggest that inhibition of the formation of agonist-induced cyclic nucleotides by NaF may be due to the formation of DAG and cAMP which lead to the activation of PKC and cAMP-PK, resulting in phosphorylation of key regulatory protein(s) in the cyclic nucleotides pathway.
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PMID:Possible involvement of protein kinase C and cyclic AMP-dependent protein kinase in the sodium fluoride-mediated inhibition of cyclic nucleotide accumulation in smooth muscle cells. 208 Oct 95

Pretreatment of A-10 cells with pertussis toxin had no effect on [arginine]vasopressin-mediated inhibition of cyclic nucleotide accumulation. Pretreatment of the cells with the same concentration of pertussis toxin produced 90-95% inhibition of [32P]ADP ribosylation in membranes, suggesting that these cells possess pertussis-toxin substrate and that the toxin enters the cells to reach its site of action. The functional integrity of the pertussis-toxin substrate in these cells is confirmed by the observation that in these cell membranes increasing concentrations of GTP inhibited basal, forskolin- and NaF-stimulated adenylate cyclase activities, and this inhibition was abolished when the cells were pretreated with pertussis toxin. In addition, thrombin-mediated inhibition of isoprenaline-stimulated cyclic AMP accumulation was also inhibited by pertussis-toxin pretreatment of the cells. These data suggest that, unlike thrombin, [arginine]vasopressin-induced inhibitory effects on cyclic nucleotide accumulation in smooth-muscle cells are not mediated by pertussis-toxin substrate.
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PMID:Inhibition of formation of cyclic AMP and cyclic GMP by vasopressin in smooth-muscle cells is insensitive to pertussis toxin. 284 52

Beta adrenergic receptor agonists and forskolin stimulated cyclic AMP (cAMP) accumulation in cultured rat aortic smooth muscle cells (A-10). Furthermore, these cells display a high density of vasopressin receptors of the vascular (V1) subtype. Addition of vasopressin to these cells inhibited beta adrenergic agonist- and forskolin-stimulated cAMP accumulation by 30 to 40% and by 25 to 35%, respectively. The extent of inhibition was dependent on the concentration of vasopressin used. Half-maximal inhibition of cAMP accumulation by isoproterenol occurred at 8 X 10(-10) M vasopressin. Basal cAMP levels were not affected. The inhibition by arginine vasopressin was mediated by V1 receptors because the V2 renal receptor subtype selective agonists (1-deamino, 8-D-arginine)vasopressin and (1-deamino,4-valine,8-D-arginine)vasopressin were ineffective. Of the antagonists tested, the V1-selective antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid),2-(O-methyl)tyrosine,8-arginine]vasopressin was more potent than the mixed V1/V2 antagonist [1-beta-mercapto--beta, beta-cyclopentamethylenepropionic acid), 2-D-(O-ethyl)tyrosine,4-valine 8-arginine]vasopressin. The V2-selective antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid),2-D-isoleucine,4-valine,8-arginine]vasopressin displayed minimal ability to block the vasopressin-mediated inhibitory effect. These data demonstrate that in rat aortic smooth muscle cells V1 receptors are negatively coupled to adenylate cyclase. The studies presented suggest that the vasoconstrictor activity of vasopressin might involve inhibition of beta adrenergic receptor-mediated vascular relaxation through inhibition of cAMP accumulation.
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PMID:Vascular vasopressin receptors mediate inhibition of beta adrenergic receptor-induced cyclic AMP accumulation. 300 35

Rat aortic smooth muscle cells in culture (A-10; ATCC CRL 1476) exhibited low levels of beta-adrenergic receptors as determined by specific binding of [125I]cyanopindolol ([125I]CYP) and marginal stimulation of adenylate cyclase in plasma membranes by (-)isoproterenol. When these cells were exposed to 5 mM sodium butyrate, the number of beta-adrenergic receptors and the beta-agonist-stimulated adenylate cyclase activity increased markedly. However, basal, GTP, Gpp(NH)p, and fluoride-stimulated activities did not change. The induction of beta-adrenergic receptors and beta-agonist stimulated adenylate cyclase activity was time- and dose-dependent, and was relatively specific for sodium butyrate. Propionate and valerate were less effective than butyrate, while isobutyrate, succinate, and malonate were ineffective. The induction involved RNA and protein synthesis because induction was prevented by treatment with cycloheximide, puromycin, and actinomycin D. Butyrate did not cause a general increase in cell surface receptors, because the number of vasopressin receptors did not change. The sustained presence of butyrate appeared to be necessary for the maintenance of the induced beta-receptors. When butyrate was removed, receptor number and beta-agonist-stimulated adenylate cyclase activity were decreased by 90% over 24 hr. We conclude that the poor response of rat aortic smooth muscle cell plasma membranes to beta-adrenergic agonists is due to the presence of a low number of beta-adrenergic receptors. Butyrate markedly increased the number of beta-receptors which resulted in a proportional increase in beta-agonist-stimulated adenylate cyclase activity. The increase in receptor number was dependent on RNA and protein synthesis. Butyrate treatment did not affect the activity of the cyclase unit and the efficiency of coupling between the receptors and the guanine nucleotide regulatory protein, Ns.
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PMID:Induction of functional beta-adrenergic receptors in rat aortic smooth muscle cells by sodium butyrate. 302 40