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)

Octapamine receptors are widely distributed in invertebrate species, yet little is known about their biochemical structure or tissue localization, in part because there exist no high affinity or irreversible ligands for these receptors. This paper characterizes 2-(2,6-diethyl-4-azidophenylimino)imidazolidine (NC-5Z), a new, high affinity octopamine receptor probe that binds reversibly and, under photolyzing conditions, irreversibly to membrane-associated octopamine receptors. Under reversible conditions NC-5Z is a full agonist, 50-100 times more potent than octopamine in activating the highly enriched and specific octopamine-sensitive adenylate cyclase of the firefly light organ. NC-5Z shows a similar potency in cockroach muscle and thoracic ganglia and in tobacco hornworm nerve cord. Activation of light organ adenylate cyclase by NC-5Z is nonadditive to that caused by octopamine and can be blocked by antagonists, including mainserin (Ki = 0.9 microM), cyproheptadine (Ki = 5 microM), phentolamine (Ki = 20 microM), and propranolol (Ki = 75 microM). These constants agree well with those for the same antagonists in inhibiting stimulation due to octopamine. In physiological studies, NC-5Z mimics the action of, but is more potent than, octopamine in stimulating light emission in intact firefly tails and in disrupting motor behavior and feeding of tobacco hornworms. Under reversible conditions, [3H]NC-5Z, the tritiated derivative of NC-5Z, binds to light organ membranes with an apparent affinity (0.59-0.7 microM) similar to that (0.35-0.7 microM) for NC-5Z in activating adenylate cyclase. Under photolyzing conditions, NC-5Z irreversibly activates light organ adenylate cyclase, and this can be blocked by an excess of octopamine. Under similar conditions, [3H]NC-5Z binds irreversibly to light organ membranes and to membranes from tobacco hornworm nerve ganglia, fat body, and gut. This binding is reduced by prior incubation with octopamine agonists, including octopamine, demethyl-chlordimeform, and 2-(phenylimino)imidazolidines, but not by norepinephrine, dopamine, serotonin, or histamine. Irreversible binding is also reduced by prior incubation with antagonists, most effectively (55% of total binding) by mianserin. The apparent affinity of [3H]NC-5Z for membrane binding, as reflected by its ability to be displaced by mianserin, is altered by GTP. In autoradiographic studies of whole tissue, [3H]NC-5Z shows irreversible, mianserin-displaceable labeling of intact firefly light organs. Taken together, these data indicate that NC-5Z and [3H]NC-5Z are potent and selective agonists of octopamine receptors in a variety of tissues.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Development of a photoaffinity ligand for octopamine receptors. 274 29

We established in culture a clonal strain (44-2C) which produces calcitonin (CT), CT gene-related peptide, neurotensin (NT), and somatostatin (SS). A compendium of experimental data detailing for this strain the differential regulation of NT, CT, and SS synthesis and secretion, adenylate cyclase activation, and cAMP efflux is presented herein. The effects of hypophysiotropic peptides, brain-gut peptides, and catecholamines are described in detail. The effects of steroid hormones, and in particular, that of the synthetic glucocorticoid, dexamethasone, are presented. The effect(s) of basic bovine fibroblast growth factor are also described. In 44-2C cells basic fibroblast growth factor selectively regulates the synthesis and secretion of CT, NT, SS, and cAMP. Moreover, basic fibroblast growth factor enhances the responsiveness of 44-2C cells to neurosecretory peptides such as rat hypothalamic GRF. We conclude that the 44-2C cells are a useful in vitro tool to study the cellular mechanism(s) controlling the differential synthesis and secretion of neuropeptides.
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PMID:The neuropeptide-synthesizing rat 44-2C cell line: regulation of peptide synthesis, secretion, 3,'5'-cyclic adenosine monophosphate efflux, and adenylate cyclase activation. 288 76

Recent experiments using intracellular recording techniques in vitro have revealed that common ionic mechanisms may explain the actions of opioid drugs. Evidence is now available from studies on guinea pig gut myenteric and submucous plexi, from preparations of spinal cord and dorsal root ganglia, from brain slices including the locus coeruleus and from neuroblastoma/glioma hybrid cells. The concensus is that mu opioid receptors activate an outward potassium conductance, possibly by way of adenylate cyclase. Activation of the receptor increases the membrane permeability to potassium ions and thus produces a membrane hyperpolarisation and conductance increase, plus an indirect inhibition of calcium entry during the action potential. Kappa opioids appear to inhibit directly the entry of calcium through voltage-dependent calcium channels, although to date there is no conclusive evidence that this mechanism of action can be extended to neurones of the central nervous system. The mechanism of action of delta opioids has only recently been investigated and initial evidence suggests they increase a potassium conductance similar to that increased by mu opioids. However, work in neuroblastoma x glioma hybrid cells has suggested that in these cells at least, receptor activation depress a component of voltage-dependent calcium current. The link between the receptor and the calcium channel involves a G-protein, Go.
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PMID:The ionic mechanisms underlying opioid actions. 290 85

There is a great need for substances that can act as adjuvants on local mucosal immune responses to perorally (p.o.) administered immunogens and which could be included in future oral vaccines. In this study we show that in mice cholera toxin (CT) is a potent adjuvant on enteric mucosal immune responses to related (cholera B subunit) as well as unrelated (KLH) antigens presented by the p.o. route. The adjuvant action of CT was dose-dependent and was achieved only when CT was given p.o. and together with the antigen. Both priming (memory induction) and boosting of the gut mucosal immune system by the oral route were greatly potentiated by CT. High numbers of specific antibody-producing cells as well as substantial mucosal memory in the lamina propria were stimulated by p.o. priming immunizations if CT adjuvant was included. Anamnestic responses could be elicited by a single p.o. booster immunization for at least 10 weeks and probably much longer. The adjuvant action of CT is suggested to involve activation of adenylate cyclase and cyclic AMP-mediated signals with differential effects on B and regulatory T intestinal lymphocytes. The adjuvant-active dose of CT, 100-500 ng, was lower than the immunogenic dose (2 micrograms) and much below the p.o. dose needed for detectable net fluid secretion in mouse intestine (5-10 micrograms). Cholera B subunit (10 micrograms) administered p.o. together with 500 ng of CT was 50 times more effective in stimulating gut mucosal anti-toxin responses compared with B subunit vaccine alone. Our results suggest that CT or substances that use similar adjuvant mechanisms may substantially increase the mucosal immunogenicity and efficacy of non-replicating oral vaccines.
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PMID:Strong adjuvant properties of cholera toxin on gut mucosal immune responses to orally presented antigens. 302 14

Salmonella typhimurium SR-11 strains lacking adenylate cyclase and the cyclic AMP receptor protein (CRP) due to deletion (delta) mutations in the cya and crp genes, respectively, are avirulent for mice and induce high level protective immunity against subsequent challenge with wild-type virulent S. typhimurium SR-11 cells. The avirulence of these delta cya delta crp mutants has been enhanced by elimination of the 100 kb virulence plasmid pStSR100 without impairing immunogenicity. The present report confirms the avirulence and immunogenicity of these mutant strains, demonstrates that immunization of both four- and eight-week-old mice has no adverse effect on weight gain, and that immunity lasts at least ninety days following initial immunization. Avirulent S. typhimurium strains have been endowed with the ability to produce several streptococcal colonization and virulence antigens for the purpose of constructing recombinant bivalent oral vaccine strains. Important antigenic determinants of the Streptococcus sobrinus surface protein antigen A (SpaA), presumed to be a critical colonization antigen of S. sobrinus, are expressed at high level by the delta cya delta crp S. typhimurium strains. The recombinant vaccine strains are stable in vitro and in animals (for a period of at least eight days) where they localize to the gut-associated lymphoid tissue (GALT).
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PMID:Avirulent Salmonella typhimurium delta cya delta crp oral vaccine strains expressing a streptococcal colonization and virulence antigen. 329 52

Blood and urine samples were collected at timed intervals for up to 120 min after the start of a 30-min infusion of 30 IU bovine parathyroid hormone (PTH) into 6 normal male subjects. Infusions were performed before and after 7 days' treatment with lithium carbonate. A highly significant increase in the maximum renal tubular reabsorption capacity for calcium (TmCa/GFR) from 2.02 +/- 0.04 to 2.17 +/- 0.07 mmol/l (p less than 0.02) produced a significant rise in plasma calcium. Lithium had no effect on basal fasting PTH or nephrogenous cyclic AMP (cAMP). Changes in nephrogenous cAMP and TmP/GFR in response to PTH were not altered by lithium. The absorption of 47Ca following an oral calcium load was increased in 5 out of 6 subjects also treated for 1 week with lithium. These results suggest that lithium has a direct effect on calcium transport, both at the level of the renal tubule and the gut, which is not mediated by stimulation of parathyroid activity or via modification of PTH-stimulated adenylate cyclase.
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PMID:Effect of lithium on the metabolic response to parathyroid hormone. 358 84

An Escherichia coli strain isolated from a patient with severe cholera-like diarrhea elaborates a partly heat-labile enterotoxin shown to cause prompt adenyl cyclase stimulation and isotonic fluid secretion by canine jejunum. Both responses disappear upon removal of the enterotoxin. The duration of action of a submaximal dose of this E. coli enterotoxin was brief, despite sustained exposure to the jejunum, suggesting inactivation of the enterotoxin by its interaction with the mucosa. Inoculation of whole bacterial cultures of this E. coli strain into canine duodenum was followed by bacterial survival and induction of net secretion after 4-7 h. The onset of fluid production was associated with increasing gut mucosal adenyl cyclase activity. Washed bacterial cells could also produce fluid secretion. In vivo multiplication of this enterotoxin-producing E. coli was demonstrated 6-12 h after intraduodenal inoculation of approximately 10(6) organisms. This was associated with fluid secretion. Intestinal fluid production occurred without microscopic pathology in the mucosa.
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PMID:Effect of Escherichia coli on fluid transport across canine small bowel. Mechanism and time-course with enterotoxin and whole bacterial cells. 457 57

Secretin, a gut-brain peptide, elicited cyclic AMP production in a clone of neuroblastoma cells derived from the C1300 mouse tumor. Adenylate cyclase (EC 4.6.1.1) in plasma membranes from these cells was stimulated by secretin greater than vasoactive intestinal peptide greater than peptide histidine isoleucine amide, but not by the related peptides glucagon, gastric inhibitory polypeptide, or human growth hormone releasing factor. Hill coefficients for stimulation approximated one and the response to submaximal peptide concentrations was additive, as expected for hormones competing for a single receptor associated with the enzyme. Binding of 125I-labeled secretin to the neuroblastoma plasma membranes was saturable, time-dependent, and reversible. The KD determined from kinetic and equilibrium binding studies approximated 1 nM. The binding site displayed marked ligand specificity that paralleled that for stimulation of adenylate cyclase. The secretin receptor was regulated by guanine nucleotides, with guanosine 5'-(beta, gamma-imino)-triphosphate being the most potent to accelerate the rate of dissociation of bound secretin. These findings demonstrate the functional association of the secretin receptor with adenylate cyclase in neuronally derived cells.
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PMID:Secretin receptors on neuroblastoma cell membranes: characterization of 125I-labeled secretin binding and association with adenylate cyclase. 632 61

Adaptation to cholera toxin (CT) and the heat-labile enterotoxin (LT) from E. coli is studied in vivo in the rat small intestine. Repeated peroral pretreatment with CT or LT induces protracted inhibition of the intestinal fluid response to these toxins. The CT-induced mucus release from intestinal goblet cells is not influenced by CT pretreatment and the binding of CT to the epithelium remains intact. However, the adenylate cyclase activity, which mediates CT and LT action, is repressed--as judged from the response of this enzyme to both CT, LT and prostaglandin E1. The results suggests that protection against CT and LT acquired in the gut is achieved by desensitization of the adenylate cyclase system.
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PMID:Intestinal adaptation to cyclic AMP-mediated hypersecretion induced by the heat-labile enterotoxin of Vibrio cholerae and Escherichia coli. 632 33

The effects of FMRFamide (Phe-Met-Arg-Phe-NH2), YGG-FMRFamide (Tyr-Gly-Gly-Phe-Met-Arg-Phe-NH2), and Met-enkephalin (Tyr-Gly-Gly-Phe-Met) on the isolated Aplysia anterior gizzard were examined. (i) FMRFamide inhibits spontaneous gut activity. While YGG-FMRFamide also inhibits spontaneous activity it is less potent than FMRFamide. Met-enkephalin does not affect spontaneous gut activity. (ii) FMRFamide inhibits the excitatory response of acetylcholine on both the anterior gizzard of Aplysia and the isolated stomach region of Navanax. (iii) Neither FMRFamide, YGG-FMRFamide, Met-enkephalin, nor acetylcholine stimulated the activity of adenylate cyclase in the Aplysia anterior gizzard.
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PMID:FMRFamide effects on spontaneous and induced contractions of the anterior gizzard in Aplysia. 662 35


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