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Maghsoudi S, Shuaib R, Van Bastelaere B, Dakshinamurti S. Adenylyl cyclase isoforms 5 and 6 in the cardiovascular system: complex regulation and divergent roles. Front Pharmacol 2024; 15:1370506. [PMID: 38633617 PMCID: PMC11021717 DOI: 10.3389/fphar.2024.1370506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Accepted: 03/11/2024] [Indexed: 04/19/2024] Open
Abstract
Adenylyl cyclases (ACs) are crucial effector enzymes that transduce divergent signals from upstream receptor pathways and are responsible for catalyzing the conversion of ATP to cAMP. The ten AC isoforms are categorized into four main groups; the class III or calcium-inhibited family of ACs comprises AC5 and AC6. These enzymes are very closely related in structure and have a paucity of selective activators or inhibitors, making it difficult to distinguish them experimentally. AC5 and AC6 are highly expressed in the heart and vasculature, as well as the spinal cord and brain; AC6 is also abundant in the lungs, kidney, and liver. However, while AC5 and AC6 have similar expression patterns with some redundant functions, they have distinct physiological roles due to differing regulation and cAMP signaling compartmentation. AC5 is critical in cardiac and vascular function; AC6 is a key effector of vasodilatory pathways in vascular myocytes and is enriched in fetal/neonatal tissues. Expression of both AC5 and AC6 decreases in heart failure; however, AC5 disruption is cardio-protective, while overexpression of AC6 rescues cardiac function in cardiac injury. This is a comprehensive review of the complex regulation of AC5 and AC6 in the cardiovascular system, highlighting overexpression and knockout studies as well as transgenic models illuminating each enzyme and focusing on post-translational modifications that regulate their cellular localization and biological functions. We also describe pharmacological challenges in the design of isoform-selective activators or inhibitors for AC5 and AC6, which may be relevant to developing new therapeutic approaches for several cardiovascular diseases.
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Affiliation(s)
- Saeid Maghsoudi
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB, Canada
- Biology of Breathing Group, Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Rabia Shuaib
- Biology of Breathing Group, Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Ben Van Bastelaere
- Biology of Breathing Group, Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Shyamala Dakshinamurti
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB, Canada
- Biology of Breathing Group, Children’s Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
- Section of Neonatology, Department of Pediatrics, Health Sciences Centre, Winnipeg, MB, Canada
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2
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Abstract
Ca(2+) regulates mammalian adenylyl cyclases in a type-specific manner. Stimulatory regulation is moderately well understood. By contrast, even the concentration range over which Ca(2+) inhibits adenylyl cyclases AC5 and AC6 is not unambiguously defined; even less so is the mechanism of inhibition. In the present study, we compared the regulation of Ca(2+)-stimulable and Ca(2+)-inhibitable adenylyl cyclases expressed in Sf9 cells with tissues that predominantly express these activities in the mouse brain. Soluble forms of AC5 containing either intact or truncated major cytosolic domains were also examined. All adenylyl cyclases, except AC2 and the soluble forms of AC5, displayed biphasic Ca(2+) responses, suggesting the presence of two Ca(2+) sites of high ( approximately 0.2 microM) and low affinity ( approximately 0.1 mM). With a high affinity, Ca(2+) (i) stimulated AC1 and cerebellar adenylyl cyclases, (ii) inhibited AC6 and striatal adenylyl cyclase, and (iii) was without effect on AC2. With a low affinity, Ca(2+) inhibited all adenylyl cyclases, including AC1, AC2, AC6, and both soluble forms of AC5. The mechanism of both high and low affinity inhibition was revealed to be competition for a stimulatory Mg(2+) site(s). A remarkable selectivity for Ca(2+) was displayed by the high affinity site, with a K(i) value of approximately 0.2 microM, in the face of a 5000-fold excess of Mg(2+). The present results show that high and low affinity inhibition by Ca(2+) can be clearly distinguished and that the inhibition occurs type-specifically in discrete adenylyl cyclases. Distinction between these sites is essential, or quite spurious inferences may be drawn on the nature or location of high affinity binding sites in the Ca(2+)-inhibitable adenylyl cyclases.
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Affiliation(s)
- J L Guillou
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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3
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Smith JA, Griffin M, Mireylees SE, Long RG. The inhibition of human duodenal adenylate cyclase activity by Ca2+ and the effects of EGTA. FEBS Lett 1993; 327:137-40. [PMID: 8335102 DOI: 10.1016/0014-5793(93)80157-p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
This study demonstrates that the inhibition of adenylate cyclase activity by Ca2+ is enhanced in the presence of increasing [EGTA] (0, 0.3, 1, 2.5 mM) by 2 orders of magnitude. It has been established that this effect is not because of poor Ca2+ buffering by low [EGTA] or high Ca2+ binding by the membrane preparation. It is present irrespective of stimulus. We suggest the enhanced sensitivity of adenylate cyclase to Ca2+ induced by EGTA is caused by the Ca-EGTA complex being a more inhibitory species than Ca2+. Thus consideration of the effects of the Ca-EGTA complex should be made when interpreting the results from experiments involving Ca2+ and EGTA.
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Affiliation(s)
- J A Smith
- Medical Research Centre, City Hospital, Nottingham, UK
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4
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Yovell Y, Kandel ER, Dudai Y, Abrams TW. A quantitative study of the Ca2+/calmodulin sensitivity of adenylyl cyclase in Aplysia, Drosophila, and rat. J Neurochem 1992; 59:1736-44. [PMID: 1402918 DOI: 10.1111/j.1471-4159.1992.tb11005.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Studies in Aplysia and Drosophila have suggested that Ca2+/calmodulin-sensitive adenylyl cyclase may act as a site of convergence for the cellular representations of the conditioned stimulus (Ca2+ influx) and unconditioned stimulus (facilitatory transmitter) during elementary associative learning. This hypothesis predicts that the rise in intracellular free Ca2+ concentration produced by spike activity during the conditioned stimulus will cause an increase in the activity of adenylyl cyclase. However, published values for the Ca2+ sensitivity of Ca2+/calmodulin-sensitive adenylyl cyclase in mammals and in Drosophila vary widely. The difficulty in evaluating whether adenylyl cyclase would be activated by physiological elevations in intracellular Ca2+ levels is in part a consequence of the use of Ca2+/EGTA buffers, which are prone to several types of errors. Using a procedure that minimizes these errors, we have quantified the Ca2+ sensitivity of adenylyl cyclase in membranes from Aplysia, Drosophila, and rat brain with purified species-specific calmodulins. In all three species, adenylyl cyclase was activated by an increase in free Ca2+ concentration in the range caused by spike activity. Ca2+ sensitivity was dependent on both calmodulin concentration and Mg2+ concentration. Mg2+ raised the threshold for adenylyl cyclase activation by Ca2+ but also acted synergistically with Ca2+ to activate maximally adenylyl cyclase.
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Affiliation(s)
- Y Yovell
- Howard Hughes Medical Institute, Columbia University College of Physicians and Surgeons, New York
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5
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Abstract
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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Affiliation(s)
- J A Smith
- Medical Research Centre, City Hospital, Nottingham
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6
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Mittag TW, Tormay A, Podos SM. Manganous chloride stimulation of adenylate cyclase responsiveness in ocular ciliary process membranes. Exp Eye Res 1988; 46:841-51. [PMID: 3143594 DOI: 10.1016/s0014-4835(88)80036-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Manganous chloride was compared with magnesium chloride in supporting maximal stimulations of the adenylate cyclase system in ocular ciliary process membranes by isoproterenol, vasoactive intestinal peptide, sodium fluoride, guanosine 5'-(beta, gamma-imino) triphosphate (GppNHp), or forskolin, and in supporting synergism between isoproterenol and forskolin. The primary effect of Mn2+ (2 mM) was due to an interaction at the catalytic unit. Mn2+ had no significant effect on the function of the GTP-binding stimulatory G-protein (Gs) which couples beta-adrenergic receptors to the catalytic unit of adenylate cyclase. However, Gs-protein function was impaired by Mn2+ relative to Mg2+ when GppNHp was used instead of GTP as the ligand for the Gs-protein. Compared with Mg2+, Mn2+ caused a 4-5.5-fold increase in adenylate cyclase responsiveness to all the activators tested (except GppNHp, where the increase was 2.5-3.5-fold). Thus Mn2+ ions appeared to be intrinsically more effective at divalent cation binding sites on the catalytic unit that control its enzymatic activity. Ciliary process membranes differ from erythrocyte and S49 lymphoma cell membranes where 2 mM Mn2+ strongly inhibits hormone-Gs-protein-mediated stimulations of adenylate cyclase. Divalent cations bound to the catalytic unit also affected the degree of synergism between hormone-activated Gs and forskolin to stimulate adenylate cyclase activity. In the presence of MgCl2 all effective doses of isoproterenol and forskolin in combination showed marked synergism. In contrast, with MnCl2 there was no synergism with high-dose isoproterenol-forskolin combinations, which gave only additive responses.
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Affiliation(s)
- T W Mittag
- Department of Ophthalmology, Mount Sinai School of Medicine, CUNY 10029
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7
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Lahav M, Rennert H, Barzilai D. Inhibition by vanadate of cyclic AMP production in rat corpora lutea incubated in vitro. Life Sci 1986; 39:2557-64. [PMID: 2432373 DOI: 10.1016/0024-3205(86)90109-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Vanadate, a normal constituent of cells, has been reported to affect a variety of enzymes involved in phosphate transfer; the findings regarding adenylate cycle vary with the tissue and experimental system. In the corpus luteum, cyclic AMP (cAMP) stimulates steroidogenesis; and prostaglandin F2 alpha, which induces luteal regression, inhibits luteinizing hormone (LH)-induced cAMP accumulation. We examined the influence of orthovanadate on cAMP concentration in isolated corpora lutea from pseudopregnant rats. With 2 mM vanadate, basal cAMP level was unaffected, but LH-induced cAMP accumulation was inhibited by 45-68%. Lower doses of vanadate (0.2-1 mM) were almost as effective. When added simultaneously with LH, vanadate was inhibitory within 25 min, but no inhibition occurred when vanadate was added for 30 min to tissue pretreated with LH for 60 min. The decrease in cAMP accumulation was observed also when corpora lutea were exposed to vanadate in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.5 mM), indicating that vanadate inhibits cAMP synthesis. Vanadate may increase cytosolic calcium by inhibiting ion pumps in cell membranes. Thus, we examined the effect of vanadate in corpora lutea incubated in calcium-depleted medium and found that vanadate still inhibited cAMP formation. Vanadyl sulfate (0.4 and 2 mM) reduced the LH-induced cAMP accumulation as effectively as vanadate. Thus, the use of vanadate as a tool for exploring physiological regulators of luteal adenylate cyclase should be considered.
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8
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Grigorian GY, Resink TJ, Stucki S, Bühler FR. Calmodulin regulation of adenylate cyclase activity in human platelet membranes. Cell Calcium 1986; 7:261-73. [PMID: 3768941 DOI: 10.1016/0143-4160(86)90005-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The mechanism of calmodulin dependent regulation of adenylate cyclase has been studied in human platelet membranes. Calmodulin activated adenylate cyclase exhibited a biphasic response to both Mg2+ and Ca2+. A stimulatory effect of Mg2 on adenylate cyclase was observed at all Mg2+ concentrations employed, although the degree of activation by calmodulin was progressively decreased with increasing concentrations of Mg2+. These results demonstrate that the Vmax of calmodulin dependent platelet adenylate cyclase can be manipulated by varying the relative concentrations of Mg2+ and Ca2+. The activity of calmodulin stimulated adenylate cyclase was always increased 2-fold above respective levels of activity induced by GTP, Gpp(NH)p and/or PGE. The stimulatory influence of calmodulin was not additive but synergistic to the effects of PGE1, GTP and Gpp(NH)p. GDP beta S inhibited GTP-and Gpp(NH)p stimulation of adenylate cyclase but was without effect on calmodulin stimulation. Since the inhibitory effects of GDP beta S have been ascribed to apparent reduction of active N-protein-catalytic unit (C) complex formation, these results suggest that the magnitude of calmodulin dependent adenylate cyclase activity is proportional to the number of N-protein-C complexes, and that calmodulin interacts with preformed N-protein-C complex to increase its catalytic turnover. Our data do not support existence of two isoenzymes of adenylate cyclase (calmodulin sensitive and calmodulin insensitive) in human platelets.
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9
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Hanski E, Garty NB. Activation of adenylate cyclase by sperm membranes. The role of guanine nucleotide binding proteins. FEBS Lett 1983; 162:447-52. [PMID: 6313428 DOI: 10.1016/0014-5793(83)80805-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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10
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Shima S, Komoriyama K, Hirai M, Kouyama H. beta-Adrenergic stimulation of the adenosine 3',5'-monophosphate system regulated by cholinergic stimuli in the prostate. Biochem Pharmacol 1983; 32:529-33. [PMID: 6189493 DOI: 10.1016/0006-2952(83)90534-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Acetylcholine significantly inhibited isoproterenol-stimulated adenosine 3',5'-monophosphate (cAMP) levels of rat prostatic tissue in a concentration-dependent fashion. Atropine but no hexamethonium reversed the inhibitory action of acetylcholine. Tetracaine and verapamil abolished the inhibitory effect of acetylcholine on isoproterenol-stimulated accumulation of cAMP. Exclusion of calcium also eliminated the effect of acetylcholine. Inhibitory regulation of cAMP levels was reproduced by the divalent cation ionophore A23187. These observations suggest that beta-adrenergic stimulation of the cAMP system of the prostate is regulated by cholinergic stimulation involving a specific muscarinic receptor with calcium-dependent mechanism sensitive to verapamil or tetracaine.
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11
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Shima S, Komoriyama K, Hirai M, Kouyama H. Blockade of heterologous desensitization of prostate adenylate cyclase without blockade of homologous down regulation of receptors or loss of GTP regulation of agonist binding. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32884-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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12
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Braun S, Arad H, Levitzki A. The interaction of Mn2+ with turkey erythrocyte adenylate cyclase. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 705:55-62. [PMID: 6288107 DOI: 10.1016/0167-4838(82)90335-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mn2+ at concentrations below 0.1 mM supports the activation of turkey erythrocyte adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) by beta-agonists or NaF, similarly to Mg2+ at 5.0 mM. At higher concentrations, Mn2+ is strongly inhibitory, as is Mg2+ above 6 mM. Also, Mn2+ with GTP, but in the absence of beta-agonist, is very potent in reversing the Gpp(NH)p permanently active state to the basal state. beta-Receptor (R) to guanyl nucleotide regulatory protein (N) coupling still occurs at inhibitory Mn2+ concentrations, since the intrinsic kinetic parameters which characterize the R to N coupling interrelationship are unaffected by Mn2+ at a wide concentration range. It is suggested that the inhibitory effect of Mn2+ is due to the impairment of the guanyl nucleotide regulatory protein (N) to the catalytic subunit (C) interaction.
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Lasker RD, Downs RW, Aurbach GD. Calcium inhibition of adenylate cyclase: studies in turkey erythrocyte and S49 CYC- cell membranes. Arch Biochem Biophys 1982; 216:345-55. [PMID: 6980630 DOI: 10.1016/0003-9861(82)90220-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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14
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Pinchasi I, Michaelson DM. Adenylate cyclase of Torpedo synaptosomes is inhibited by calcium and not affected by muscarinic ligands. J Neurochem 1982; 38:1223-9. [PMID: 7062048 DOI: 10.1111/j.1471-4159.1982.tb07894.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Cholinergic synaptosomes isolated from the electric organ of Torpedo contain membrane-bound adenylate cyclase activity (approximately 6 pmol/mg protein/min), which is dependent on the presence of guanine nucleotides. The activity is strongly dependent on temperature and only slightly affected by NaCl. The Torpedo adenylate cyclase is completely inhibited by low levels of free Ca2+ (KD approximately 0.5 microM). This effect is not altered by either trifluoperazine or addition of exogenous calmodulin. Ca2+ has no effect on the activation step of the adenylate cyclase by guanyl-5'-yl imidodiphosphate (GppNHp), and Mn2+ abolishes the Ca2+-dependent inhibition of cyclic AMP synthesis. These findings suggest that Ca2+ exerts its effect by direct interaction with a site located on the catalytic subunit. Torpedo synaptosomes contain presynaptic inhibitory muscarinic receptors. The binding of muscarinic agonists to the receptors is modulated (to lower affinity) by GTP. However, muscarinic ligands, examined under a variety of assay conditions, have no effect on adenylate cyclase activity. These results suggest that although both the muscarinic receptor and the adenylate cyclase are coupled to G proteins, they either interact with different G proteins or are situated in different regions of the presynaptic membrane.
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Keenan AK, Gal A, Levitzki A. Reconstitution of the turkey erythrocyte adenylate cyclase sensitivity to 1-epinephrine upon re-insertion of the Lubrol solubilized components into phospholipid vesicles. Biochem Biophys Res Commun 1982; 105:615-23. [PMID: 7092873 DOI: 10.1016/0006-291x(82)91479-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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16
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Bradham LS, Cheung WY. Nucleotide cyclases. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1982; 27:189-231. [PMID: 6124997 DOI: 10.1016/s0079-6603(08)60601-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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17
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Williamson JR, Cooper RH, Hoek JB. Role of calcium in the hormonal regulation of liver metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 639:243-95. [PMID: 7039675 DOI: 10.1016/0304-4173(81)90012-4] [Citation(s) in RCA: 287] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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18
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Ohanian H, Borhanian K, de Farias S, Bennun A. A model for the regulation of brain adenylate cyclase by ionic equilibria. J Bioenerg Biomembr 1981; 13:317-55. [PMID: 7334023 DOI: 10.1007/bf00743209] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Multiple-equilibrium equations were solved to investigate the individual and separate effects of Mg2+, Mn2+, Ca2+, ATP4-, and their complexes on the kinetics of brain adenylate cyclase. The effects of divalent metals and/or ATP4- (in excess of their participation in complex formation) were determined and, from the corresponding apparent affinity values, the following kinetic constants were obtained: Km(MgATP) = 1.0 mM, Ki(ATP4-) = 0.27 mM, Km(MnATP) = 0.07 mM, and Ki(CaATP) = 0.015 mM. MgATP, MnATP, ATP4-, and CaATP were shown to compete for the active site of the enzyme. Hence, it is proposed that endogenous metabolites with a strong ligand activity for divalent metals, such as citrate and some amino acids, become integrated into a metabolite feedback control of the enzyme through the release of ATP4- from MgATP. Ca2+ fluxes may participate in the endogenous regulation of adenylate cyclase by modifying the level of CaATP. The free divalent metals show an order of affinity K0.5(Ca2+) = 0.02 mM, K0.5(Mn2+) = 3.8 mM, K0.5(Mg2+) - 4.7 mM, and an order of activity Mn2+ greater than Mg2+ greater than Ca2+. The data indicate that Mn2+ and Mg2+ ions may compete for a regulatory site distinct from the active site and increase Vm without changing Km(MgATP), Km(MnATP), or Ki(ATP4-). The interactions of ATP4- and CaATP, which act as competitive inhibitors of the reaction of the enzyme with the substrates MgATP and MnATP, and Mg2+ and Mn2+, which act as activators of the enzyme in the absence of hormones, are shown to follow the random rapid equilibrium BiBi group-transfer mechanism of Cleland with the stipulation that neither Mg2+ nor Mn2+, in excess of their respective participation in substrate formation, are obligatorily required for basal activity. ATP4- and CaATP are involved in dead-end inhibition. For MgCl2 saturation curves at constant total ATP concentration, the computer-generated curves based on the RARE BiBi model predict a change in the Hill cooperativity h from a basal value of 2.6, when Mg2+ is not obligatorily required, to 4.0 when the addition of hormones or neurotransmitters induces an obligatory requirement for Mg2+.
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Simonin G, Zachowski A, Huitorel P, Pantaloni D, Paraf A. Stimulation by tubulin of an adenylate cyclase from murine plasmacytoma. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 118:515-9. [PMID: 7297559 DOI: 10.1111/j.1432-1033.1981.tb05549.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Different brain tubulin preparations were shown to stimulate membrane-bound adenylate cyclase from the murine plasmacytoma MOPC 173. Purified tubulin devoid of microtubule-associated proteins and of nucleoside-diphosphate kinase activity was responsible for this stimulation. Activation of the basal adenylate cyclase activity occurred in less than 2 min at 32 degrees C and was amplified by a 4 degree C preincubation of tubulin with plasma membranes. Tubulin affected the Km and the V of the enzyme and was shown to be associated with the membrane during the activation phenomenon. Tubulin was more active on the basal adenylate cyclase activity than that stimulated by fluoride or guanosine 5'-[beta, gamma-imido]triphosphate. GTP has no effect on the tubulin-stimulated enzyme.
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20
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Yurkiv VA, Melikhov VI. Inhibition of adenylate cyclase by Ca++ ions in the jejunal mucosa of rabbits. Bull Exp Biol Med 1980. [DOI: 10.1007/bf00838807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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21
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Piascik M, Wisler P, Johnson C, Potter J. Ca2+-dependent regulation of guinea pig brain adenylate cyclase. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(19)85649-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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22
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The role of calcium in the control of adrenal adenylate cyclase. Enhancement of enzyme activation by guanyl-5'-yl imidodiphosphate. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(19)86070-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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23
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Narayanan N, Wei JW, Sulakhe PV. Differences in the cation sensitivity of adenylate cyclase from heart and skeletal muscle: modification by guanyl nucleotides and isoproterenol. Arch Biochem Biophys 1979; 197:18-29. [PMID: 543714 DOI: 10.1016/0003-9861(79)90213-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Wei JW, Narayanan N, Sulakhe PV. Adenylate cyclase of guinea pig skeletal muscle sarcolemma: comparison of the properties of the enzyme with mg2+ and mn2+ as divalent cation cofactors. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1979; 10:109-16. [PMID: 34539 DOI: 10.1016/0020-711x(79)90105-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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26
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Young JL, Stansfield DA. Gel-filtration analysis of soluble adenylate cyclase from bovine corpus luteum. Biochem J 1978; 175:579-84. [PMID: 743210 PMCID: PMC1186106 DOI: 10.1042/bj1750579] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
1. Sepharose 6B gel-filtration analysis of soluble adenylate cyclase from bovine corpus luteum is described. Both zonal and frontal techniques of analysis were used. 2. Under conditions of zonal analysis recoveries of activity were low. It was concluded that dissociation of two or more components of the adenylate cyclase complex was occurring on the column and that the maintenance of the complex was essential for the high-activity state of the catalytic unit. Two peaks of adenylate cyclase activity, of approximate mol. wts. 45,000 and 160,000 were detected. 3. The theory of frontal analysis (or steady-state gel filtration), applied to the study of the interacting components of the adenylate cyclase complex is discussed, and activity profiles are predicted. Activity profiles obtained experimentally be frontal analysis compared well with the theoretically predicted profile and provide evidence that dissociation of a high-activity complex, with concomitant loss of activity, does occur. Recoveries of activity under conditions of frontal analysis were higher than with zonal analysis. 4. The effects of concentration and removal of detergent on the activity of the soluble enzyme are discussed.
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Tolkovsky AM, Levitzki A. Mode of coupling between the beta-adrenergic receptor and adenylate cyclase in turkey erythrocytes. Biochemistry 1978; 17:3795. [PMID: 212105 DOI: 10.1021/bi00611a020] [Citation(s) in RCA: 299] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The mode of coupling of the beta-adrenergic receptor to the enzyme adenylate cyclase in turkey erythrocyte membranes was analyzed in detail. A number of experimental techniques have been used: (1) measurement of the kinetics of cyclase activation to its permanetly active state in the presence of guanylyl imidodiphosphate, as a function of hormone concentrations; (2) measurement of antagonist and agoinst binding to the beta-adrenergic receptor prior and subsequent to the enzyme activation by hormone and guanylyl imidodiphosphate. On the bases of these two approaches, all the models of receptor to enzyme coupling which involve an equilibrium between the enzyme and the receptor can be rejected. The binding and the kinetic data, however, can be fitted by two diametrically opposed models of receptor to enzyme coupling: (a) the precouped enzyme-receptor model where activation of the enzyme occurs, according to the following scheme: formula (see text) where H is the hormone, RE is the precoupled respetor-enzyme complex, k1 and k2 are the rate constants describing hormone binding, and k is the rate constant characterizing the formation of HRE' from the intermediate HRE. According to this model, the activated complex is composed of all of the interacting species. (b) The other model is the collision coupling mechanism: formula (see test) wheere KH is the horome-receptor dissociation constant, k1 is the bimolecular rate constant governing the formation of HRE, and k3 the rate constant governing the activation of the enzyme. In this case the intermediate never accumulates and constitutes only a small fraction of the total receptor and adenylate cyclase concentrations. In order to establish which of the two mechanisms governs the mode of adenylate cyclase activation by its receptor, a diagnostic experiment was performed: Progressive inactivation of the beta receptor by a specific affinity label was found to cause a decrease in the maximal binding capacity of the receptor and a proportional decrease in the rate of activation, but no change in the maximum level of activity was attained. Progressive inactivation of the enzyme by p-hydroxymercuribenzoate was found not to change the rate of activation nor the capacity of the receptor to bind hormone. Only the maximal level of activation was found to be decreased. These results are not compatible with the precoupled model of receptor and cyclase nor with floating receptor models in which an intermediate of hormone, receptor, and cyclase is in equilibrium with its reactants. The data strongly suggest that the collision coupling is the mode of coupling between the beta receptor and cyclase coupling in turkey erythrocyte membranes.
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Drummond GI, Dunham J. Properties of detergent-dispersed myocardial adenylate cyclase. Arch Biochem Biophys 1978; 189:63-75. [PMID: 708049 DOI: 10.1016/0003-9861(78)90114-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Campbell AK, Siddle K. Effect of replacement of extracellular sodium ions and of D-600 on the activation by adrenalin of adenylate cyclase in intact pigeon erythrocytes. Mol Cell Endocrinol 1978; 11:79-89. [PMID: 680336 DOI: 10.1016/0303-7207(78)90034-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of replacement of extracellular Na+ by Li+, choline K+ or sucrose on cyclic AMP formation in pigeon erythrocytes has been investigated. Replacement of extracellular Na+ by Li+, choline or sucrose but not by K+ inhibited the stimulation by adrenalin of cyclic AMP formation, but had no detectable effect on cyclic AMP content in the absence of adrenalin. This inhibition was observed in the presence or absence of extracellular Ca2+. The relative inhibition caused by Na+ removal decreased with increasing adrenalin concentration. It was concluded that extracellular Na+ or K+ ions were required for maximal activation of adenylate cyclase by low concentrations of adrenalin, and that this effect of monovalent cations may have been due to an effect on the affinity of the receptor for adrenalin. The verapamil derivative D-600 also inhibited the stimulation by adrenalin of cyclic AMP formation. This effect occurred in the absence of extracellular Ca2+ and hence seemed to be unrelated to the inhibition by C-600 of the slow Ca2+ channel in electrically excitable tissues.
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Nielsen ST, Neuman WF. Effects of PTH and Ca2+ on renal adenyl cyclase. JOURNAL OF SUPRAMOLECULAR STRUCTURE 1978; 9:391-8. [PMID: 748683 DOI: 10.1002/jss.400090309] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effects of calcium ion on the adenylate cyclase system was studied in isolated, renal basal-lateral plasma membranes of the rat. Bovine parathyroid hormone (bPTH) and a guanyl triphosphate analogue, Gpp(NH)p were used to stimulate cyclase activity. Under conditions of maximal stimulation, calcium ions inhibited cyclic adenosine monophosphate (cAMP) formation, the formation rate falling exponentially with the calcium concentration. Fifty percent inhibition of either bPTH- or Gpp(NH)p-stimulated activity was given by approximately 50 microns Ca++. Also the Hill coefficient for the inhibition was close to unity in both cases. The concentration of bPTH giving half-maximal stimulation of cAMP formation (1.8 x 10(-8) M) was unchanged by the presence of calcium. These data suggest that calcium acts at some point other than the initial hormone-receptor interaction, presumably decreasing the catalytic efficiency of the enzymic moiety of the membrane complex.
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