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)

Changes in the intracellular free calcium ([Ca2+]i) of cultured normal human epidermal keratinocytes (NHEK) were investigated in order to determine whether the adenylate cyclase cAMP (AC) system and phospholipase C activating system are involved in increasing [Ca2+]i. NHEK were obtained from neonatal foreskin and grown in serum-free medium (K-GM) supplemented with 2% bovine pituitary extract. [Ca2+]i was measured by fluorescence ratio imaging microscopy using Fura-2 as the indicator. In the case of the AC system, transient increases in [Ca2+]i were observed in response to stimulation with epinephrine, norepinephrine, isoproterenol and salbutamol. Methoxamine, clonidine and dobutamine did not induce any [Ca2+]i increase. The [Ca2+]i increase evoked by epinephrine was inhibited by pretreatment with propranolol, but not by prazosin or yohimbine, indicating that epinephrine-induced [Ca2+]i elevation via beta 2-adrenergic stimulation. Similar changes were observed when NHEK were stimulated with histamine, adenosine, GTP gamma S, forskolin and dibutyryl cAMP respectively. The absence of extracellular Ca2+ had no effect on the epinephrine-induced [Ca2+]i increase. It appears that activated protein kinase A, based on cAMP accumulation via stimulatory GTP binding protein, elicited the release of Ca2+ from intracellular stores. On the other hand, when drugs known to activate phospholipase C in a wide variety of cell types were tested, a transient increase in [Ca2+]i was demonstrated in response to the addition of thrombin, bradykinin and substance P. This reaction was not affected by the presence of EGTA, suggesting that these drugs raise [Ca2+]i via phosphatidylinositol breakdown. Vasopressin, angiotensin II, serotonin and acetylcholine did not induce any increase in [Ca2+]i. On the basis of these studies, it was concluded that NHEK possess the mechanism which increase [Ca2+]i via AC system and phospholipase C activating system. It seems probable that this rise in [Ca2+]i initiates a calcium-dependent cellular response, such as activation of calcium/calmodulin dependent kinase, and subsequently regulates the proliferation and differentiation of human epidermal keratinocytes.
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PMID:[Changes in the intracellular free calcium of cultured human epidermal keratinocytes]. 171 97

Both nicotine and histamine have been reported to increase cyclic AMP levels in chromaffin cells by Ca(2+)-dependent mechanisms. The present study investigated whether Ca2+ was an adequate and sufficient signal for increasing cyclic AMP in cultured bovine adrenal medullary cells. Depolarization with 50 mM K+ caused a two- to three-fold increase in cellular cyclic AMP levels over 5 min, with no change in extracellular cyclic AMP. This response was abolished by omission of extracellular Ca2+ and by 100 microM methoxyverapamil, and was unaffected by 1 microM tetrodotoxin and by 1 mM isobutylmethylxanthine. Veratridine (40 microM) also increased cellular cyclic AMP levels by two- to fourfold. This response was abolished by either methoxyverapamil or tetrodotoxin. The Ca2+ ionophore A23187 (10-50 microM) had little or no effect on cellular cyclic AMP levels. When the concentration of K+ used to depolarize the cells was reduced to 12-15 mM, the catecholamine release was similar to that induced by 50 microM A23187, and the cyclic AMP response was almost abolished. The results suggest that Ca2+ entry into chromaffin cells is a sufficient stimulus for increasing cellular cyclic AMP production. The possible involvement of a Ca2+/calmodulin-dependent isozyme of adenylate cyclase is discussed.
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PMID:Regulation of cyclic AMP levels by calcium in bovine adrenal medullary cells. 171 56

Biochemical, immunological, and molecular cloning studies have suggested the existence of multiple forms of adenylyl cyclase (EC 4.6.1.1). An adenylyl cyclase cDNA clone (type II) was isolated from a rat brain library and found to encode a protein of 1090 amino acids that was homologous to but distinct from the previously described Ca2+/calmodulin-stimulated adenylyl cyclase from bovine brain. Expression of the type II cDNA in an insect cell line resulted in an increased level of adenylyl cyclase activity that was insensitive to Ca2+/calmodulin. Addition of activated Gs alpha protein to type II-containing membranes increased enzyme activity. The mRNA encoding the type II protein was expressed at high levels in brain tissue and at low levels in olfactory epithelium and lung. The existence of multiple adenylyl cyclase enzymes may provide for complex and distinct modes of biochemical regulation of cAMP levels in the brain.
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PMID:Molecular cloning and characterization of a Ca2+/calmodulin-insensitive adenylyl cyclase from rat brain. 171 47

A possible role for adenylate cyclase and guanine nucleotide-binding proteins (G proteins) in contributing to the chronic actions of lithium on brain function was investigated in rat cerebral cortex. It was found that chronic treatment of rats with lithium (with therapeutically relevant serum levels of approximately 1 mM) increased levels of mRNA and protein for the calmodulin-sensitive (type 1) and calmodulin-insensitive (type 2) forms of adenylate cyclase and decreased levels of mRNA and protein for the inhibitory G-protein subunits Gi alpha 1 and Gi alpha 2. Chronic lithium did not alter levels of other G-protein subunits, including Go alpha, Gs alpha, and G beta. Lithium regulation of adenylate cyclase and Gi alpha was not seen in response to short-term lithium treatment (with final serum levels of approximately 1 mM) or in response to chronic treatment at a lower dose of lithium (with serum levels of approximately 0.5 mM). The results suggest that up-regulation of adenylate cyclase and down-regulation of Gi alpha could represent part of the molecular mechanism by which lithium alters brain function and exerts its clinical actions in the treatment of affective disorders.
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PMID:Chronic lithium regulates the expression of adenylate cyclase and Gi-protein alpha subunit in rat cerebral cortex. 172 May 45

We developed an improved method of linker insertion mutagenesis for introducing 2 or 16 codons into the Bordetella pertussis cyaA gene which encodes a calmodulin-dependent adenylate cyclase. A recombinant kanamycin resistance cassette, containing oligonucleotide linkers, was cloned in plasmids which carried a truncated cyaA gene, fused at its 3' end to the 5' end of the Escherichia coli lacZ gene, specifying the alpha-peptide. This construction permitted a double selection for in-frame insertions by using screening for kanamycin resistance and for lactose-positive phenotype, resulting from alpha-complementation. We showed that most of the two-amino acid insertions within the N-terminal moiety of the catalytic domain of adenylate cyclase abolished enzymatic activity and/or altered the stability of the protein. All two-amino acid insertions within the C-terminal part of adenylate cyclase resulted in fully stable and active enzymes. These results confirm the modular structure of the catalytic domain of adenylate cyclase, previously proposed on the basis of proteolytic studies. Two-amino acid insertions between residues 247-248 and 335-336 were shown to affect the calmodulin responsiveness of adenylate cyclase, suggesting that the corresponding region in the enzyme is involved in the binding of calmodulin or in the process of calmodulin activation. In addition, we have identified within the primary structure of adenylate cyclase several permissive sites which tolerate 16-amino acid insertions without interfering with the catalytic activity or calmodulin binding. By inserting foreign antigenic determinants into these permissive sites the resulting recombinant adenylate cyclase toxin could be used to deliver specific epitopes into antigen-presenting cells.
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PMID:Insertional mutagenesis of Bordetella pertussis adenylate cyclase. 173 31

The calmodulin and calcium dependence of human adenylate cyclase from the second part of the duodenum was assessed in washed particulate preparations of biopsy specimens by investigating (a) the concentration dependent effects of free [Ca2+] on enzyme activity, (b) the effects of exogenous calmodulin on enzyme activity in ethylene glycol bis (b-aminoethyl ether)N,N'-tetra-acetic acid (EGTA) washed particulate preparations, and (c) the effects of calmodulin antagonists on enzyme activity. Both basal (IC50 = 193.75 (57.5) nmol/l (mean (SEM)) and NaF stimulated (IC50 = 188.0 (44.0) nmol/l) adenylate cyclase activity was strongly inhibited by free [Ca2+] greater than 90 nmol/l. Free [Ca2+] less than 90 nmol/l had no effect on adenylate cyclase activity. NaF stimulated adenylate cyclase activity was inhibited by 50% at 2.5 mmol/l EGTA. This inhibition could not be reversed by free Ca2+. The addition of exogenous calmodulin to EGTA (5 mmol/l) washed particulate preparations failed to stimulate adenylate cyclase activity. Trifluoperazine and N-(8-aminohexyl)-5-IODO-1-naphthalene-sulphonamide (IODO 8) did not significantly inhibit basal and NaF stimulated adenylate cyclase activity when measured at concentrations of up to 100 mumol/l. These results suggest that human duodenal adenylate cyclase activity is calmodulin independent but is affected by changes in free [Ca2+].
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PMID:Calmodulin independence of human duodenal adenylate cyclase. 175 61

The effects of Mn2+ and calmodulin were studied on the basal and agonist-modulated adenylate cyclase activity of the guinea pig superior cervical ganglion. The divalent cation strongly stimulates the basal and agonist-modulated enzyme in a concentration-dependent manner. Moreover, in the presence of Mn2+ the inhibitory effects of "high" GTP concentrations and of D-Ala2-Met-enkephalinamide on adenylate cyclase are eliminated, while the stimulation exerted by prostaglandin E2 and the supra-additive activation of the enzyme by the combination of the two drugs are unaffected. In EGTA-washed, calmodulin-depleted membrane preparations, Mn2+ still activates the cyclase but the enkephalin inhibition and the superactivation of the enzyme induced by the combination of opiate and prostaglandin are lost, both in the absence and in the presence of the cation. Reconstituting the depleted membranes with exogenous Ca2+/calmodulin fully restored the enzyme responsivity to the combination and, partially, to the enkephalin. The findings suggest the existence in the guinea pig superior cervical ganglion of both the calmodulin-sensitive and differently regulated calmodulin-insensitive adenylate cyclase.
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PMID:Receptor-mediated supra-additive activation of guinea pig superior cervical ganglion adenylate cyclase: role of Mn2+ ions and calmodulin. 175 35

We have demonstrated that ISO produces part of its negative inotropic action through activation of the plasmalemmal Na+/K+ pump, and reduction of [Na+]i. This action is mediated by the beta-adrenergic receptor through activation of adenylate cyclase. The reduction of [Na+]i is most probably translated to a change in the contractile state of the cell through activation of the Na+/Ca2+ exchanger. While the exchanger is at equilibrium when the cell is at rest, after ISO it would extrude Ca2+ at the expense of the increased Na+ gradient, resulting in a decrease Ca2+ availability and a reduction in the magnitude of subsequent contractions. We have also seen that the previous calcium history of the myoplasm can influence the time course of future calcium transients. Prolonged large increases in [Ca2+]i can accelerate the rate of its removal and depress basal [Ca2+]i levels. This action is most probably mediated through a Ca2+/calmodulin dependent protein kinase. We have observed that MLCK is both necessary and sufficient to produce contraction of Bufo marinus stomach smooth muscle. There is also evidence that an as yet unidentified Ca(2+)-calmodulin dependent protein kinase is acting to limit the magnitude and the duration of the Ca2+ transient by feeding back on processes involved in Ca2+ signal generation.
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PMID:Calcium homeostasis in single intact smooth muscle cells. 180 98

Bordetella pertussis produces a calmodulin-activated adenylate cyclase (AC) that exists in several forms. Only one form of AC, of apparent 200 kDa, is a toxin that penetrates eukaryotic cells and generates uncontrolled levels of intracellular cAMP. Recombination studies in transposon Tn5-insertion mutants of B. pertussis and amino acid sequence homology with alpha-hemolysin of Escherichia coli suggested that AC toxin may also have a hemolytic activity. Here, we demonstrate that only the toxic form of B. pertussis AC possesses hemolytic activity. Immunoblotting of membranes from sheep erythrocytes throughout the process of cell lysis detects the presence and accumulation of only the 200-kDa form of B. pertussis AC. cAMP generation induced by AC toxin in sheep erythrocytes is immediate whereas appearance of hemolysis is delayed by about 1 h and requires a higher level of AC toxin activity. Addition of exogenous calmodulin to sheep erythrocyte incubation medium potentiates the hemolytic activity of AC toxin but blocks cAMP generation. Extracellular Ca2+ at mM concentrations is absolutely required for cAMP generation but not for hemolysis. However, binding of AC toxin to sheep erythrocytes in the absence of exogenous Ca2+ followed by reincubation of cells in a toxin-free buffer containing Ca2+ leads to an immediate rise in intracellular cAMP. Human erythrocytes bind AC toxin and generate cAMP but are resistant to lysis. These results show that binding of AC toxin to erythrocytes can cause both cAMP generation and hemolysis or only one of these depending on conditions applied and cell type used.
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PMID:Adenylate cyclase toxin from Bordetella pertussis. The relationship between induction of cAMP and hemolysis. 184 41

The modulation of neuronal adenylylcyclase by Ca2+, acting via calmodulin, is a long-established example of a positive interaction between the Ca2(+)-mobilizing and cAMP-generating systems. In the present study, concentrations of Ca2+ that stimulate brain adenylylcyclase inhibit the adenylylcyclase of NCB-20 plasma membranes. These inhibitory effects of Ca2+ have been characterized and seem to be exerted at the catalytic unit of the enzyme; they are independent of calmodulin, Gi, and phosphodiesterase. To determine whether this inhibition of adenylylcyclase by Ca2+ could occur in the intact cell, cAMP accumulation was measured in response to bradykinin. Bradykinin, which mobilizes Ca2+ in NCB-20 cells, as a consequence of stimulating inositol phosphate production, causes a transient inhibition of prostaglandin E1 stimulation of cAMP accumulation. The inhibitory action of bradykinin is attenuated significantly by treatment of cells with the cell-permeant Ca2+ chelator, 1,2-bis-(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid. It seems likely that the inhibition of adenylylcyclase by low concentrations of Ca2+ represents a novel means for a negative interaction between Ca2(+)-mobilizing and cAMP-generating systems.
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PMID:Bradykinin stimulates Ca2+ mobilization in NCB-20 cells leading to direct inhibition of adenylylcyclase. A novel mechanism for inhibition of cAMP production. 184 32


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