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)

Treatment of ROS 17/2.8 cells with dexamethasone (dex) increases (-)isoproterenol (ISO)-, PTH-, cholera toxin-, guanine nucleotide-, NaF-, and forskolin-stimulated adenylate cyclase activity. Enhanced hormone stimulation was first apparent 12 h after dex addition. (-)-[3H]Dihydroalprenolol binding, displaceable by ISO, increased up to 2-fold in dex-treated cells. This effect depended on protein synthesis and closely paralleled the extent and time course of the increase in adenylate cyclase stimulation. In dex-treated cells there was also an increase in the maximum velocity of guanyl-5'-yl imidodiphosphate-stimulated adenylate cyclase, a decrease in the lag time for guanyl-5'-yl imidodiphosphate enzyme activation in the presence of ISO from 3 to 1 min, increased stimulation of adenylate cyclase by cholera toxin, and increased labeling of 47,000 and 42,000 mol wt proteins by [32P]NAD in the presence of cholera toxin. [32P]NAD ribosylation in the presence of pertussis toxin resulted in the labeling of 40,000 mol wt protein, which was also increased by 20-50% in dex-treated cells. However, pertussis toxin treatment did not augment or reduce the effect on hormone stimulation, although it increased the cAMP response to PTH and (-)ISO. These findings suggest that dex increases (-)ISO stimulation of adenylate cyclase in ROS 17/2.8 cells by jointly increasing the number of hormone receptors and the abundance of Gs, the guanine nucleotide binding regulatory protein.
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PMID:Dexamethasone effects on beta-adrenergic receptors and adenylate cyclase regulatory proteins Gs and Gi in ROS 17/2.8 cells. 300 62

The influence of 1,25-dihydroxyvitamin D-3 on the cAMP response to parathyroid hormone was studied in the osteoblast-like rat osteosarcoma cells ROS 17/2.8. The stimulation by parathyroid hormone of cAMP production in intact cells and of adenylate cyclase activity in isolated plasma membranes was attenuated by 1,25-dihydroxyvitamin D-3 treatment. This was associated with a reduction of the stimulatory guanine nucleotide regulatory protein, as demonstrated by a lower response to NaF and guanosine 5'-[beta, gamma-imido]triphosphate, and by a lower activity of solubilized plasma membrane extracts in the reconstitution assay. 1,25-dihydroxyvitamin D-3 blunted also the cAMP response to parathyroid hormone in cells incubated with the glucocorticoid dexamethasone, where a higher activity of the adenylate cyclase catalytic unit was observed. Thus, the two steroids appear to affect distinct levels of the adenylate cyclase system. Furthermore, the two hormones also showed an antagonistic effect upon the production of osteocalcin, an osteoblast-specific extracellular matrix protein. The release of this non-collagenous matrix protein by ROS 17/2.8 cells was increased by 1,25-dihydroxyvitamin D-3 and decreased by dexamethasone.
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PMID:Heterologous desensitization by 1,25-dihydroxyvitamin D-3 of cyclic AMP response to parathyroid hormone in osteoblast-like cells and the role of the stimulatory guanine nucleotide regulatory protein. 301 22

Based on the finding that retinoic acid (RA) increases 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptor number in ROS 17/2 cells, we investigated the effects of RA on the ability of 1,25-(OH)2D3 to regulate alkaline phosphatase activity and PTH-responsive adenylate cyclase in these cells. A maximally effective dose of 1,25-(OH)2D3 (10(-8) M) caused a 75-80% increase in alkaline phosphatase activity and an approximately 70-75% attenuation of the cAMP response to PTH, while RA (10(-6) M) decreased alkaline phosphatase activity by 30-45% and decreased PTH-stimulated cAMP levels by approximately 20%. Preincubation with RA did not enhance the 1,25-(OH)2D3-induced increases in alkaline phosphatase activity. The ED50 values for control and RA-treated cultures were approximately 8 X 10(-10) M and 6 X 10(-10) M, respectively. With regard to PTH responsiveness, the effects of RA preincubation on the 1,25-(OH)2D3 attenuation of cAMP response varied with the concentration of 1,25-(OH)2D3. At low doses (less than 10(-9) M), the effects of 1,25-(OH)2D3 and RA were additive. At higher doses of 1,25-(OH)2D3, the effects of RA and 1,25-(OH)2D3 were not additive, and there were no differences between control- and RA-treated cultures. The ED50 values for control- and RA-treated cultures were 10(-10) M and 3 X 10(-11) M, respectively. None of the above effects were observed using equimolar doses of the vitamin D3 metabolites 24,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3. The data show that pretreating ROS 17/2A cells with RA to increase 1,25-(OH)2D3 receptors does not correspond with a concomitant increase in the cellular responsiveness to 1,25-(OH)2D3, as measured by increases in alkaline phosphatase activity and decreases in PTH-responsive adenylate cyclase.
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PMID:Modulation by retinoic acid of 1,25-dihydroxyvitamin D3 effects on alkaline phosphatase activity and parathyroid hormone responsiveness in an osteoblast-like osteosarcoma cell line. 301 60

Glucocorticoids are known to increase the cyclic AMP response to parathyroid hormone (PTH) in cultured bone organs or bone cells. Using the osteoblast-like cell line ROS 17/2.8, which possesses receptors for both PTH and glucocorticoids, we investigated which component of the complex hormone receptor-guanine nucleotide regulatory unit--adenylate cyclase was affected by dexamethasone treatment. In response to PTH, isoproterenol or forskolin, a compound that is supposed to act directly on the catalytic unit, cyclic AMP production by intact cells and adenylate cyclase activity in purified plasma membrane were markedly increased by dexamethasone. Whereas NaF, guanosine 5'-[beta gamma-imido]triphosphate and Mn/ stimulated adenylate cyclase activity were similarly enhanced in membranes isolated from glucocorticoid-treated cells, the activity of the stimulatory guanine nucleotide regulatory unit, as assessed by reconstitution into membranes from the CYC- clone, which is genetically devoid of this component, was not altered. Thus in osteoblast-like cells dexamethasone appears to increase cyclic AMP synthesis by influencing the catalytic unit. Moreover, since it has been reported that glucocorticoids may produce changes in cell calcium metabolism, we evaluated cytoplasmic free Ca2+ concentration ([Ca2+]i) and intracellular Ca2+ stores mobilizable by the bivalent-cationophore ionomycin, by using the intracellular fluorescent indicator Quin-2. The results indicated that dexamethasone treatment did not influence [Ca2+]i but markedly decreased ionomycin-releasable Ca2+ stores.
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PMID:Increase of adenylate cyclase catalytic-unit activity by dexamethasone in rat osteoblast-like cells. 309 55

Information available at present documents the existence of three well-defined classes of guanine nucleotide binding proteins functioning as signal transducers: Gs and Gi which stimulate and inhibit adenylate cyclase, respectively, and transducin which transmits and amplifies the signal from light-activated rhodopsin to cGMP-dependent phosphodiesterase in ROS membranes. Go is a fourth member of this family. Its function is the least known among GTP binding signal transducing proteins. The family of G proteins has a number of properties in common. All are heterotrimers consisting of three subunits, alpha, beta, and gamma. Each of the subunits may be heterogeneous depending on species and tissue of origin and may be posttranslationally modified covalently. The alpha subunits vary in size from 39 to 52 kDa. The sequences for Gs alpha and transducin alpha have 42% overall homology and those of Gi alpha and Gs alpha 43%, whereas those of Gi alpha and transducin alpha have a higher degree (68%) of homology. All alpha subunits bind guanine nucleotides and are ADP-ribosylated by either pertussis toxin (Gi, transducin, Go) or cholera toxin (Gs, Gi, transducin). Thus, transducin and Gi, which have the highest degree of sequence homology, are also ADP-ribosylated by both toxins. The beta subunits have molecular weights of 36 and 35 kDa, respectively. While Gs, Gi, and Go contain a mixture of both, transducin contains only the larger (36-kDa) beta-polypeptide. The relationship of the 36- and the 35-kDa beta subunits is not defined. Although the complete sequence of the 36-kDa beta subunit of transducin has been deduced from the cDNA sequence, complete sequences of other beta subunits are not yet available so that detailed comparisons cannot be made at present. However, the proteolytic profiles of each class of the beta subunits of different G proteins are indistinguishable. The gamma subunit of bovine transducin has been completely sequenced. It has a Mr of 8400. Again complete sequences of other gamma subunits are not yet available. While the gamma subunits of Gs, Gi, and Go have identical electrophoretic mobility in SDS gels, they differ significantly in this respect from the gamma subunit of transducin. Moreover, crossover experiments point to functional differences between gamma subunits from G protein and transducin complexes. In addition, a role for beta, gamma in anchoring guanine nucleotide binding proteins to membranes has been postulated.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Structural and functional relationships of guanosine triphosphate binding proteins. 313 54

Treatment of ROS 17/2.8 osteosarcoma-derived cells with dexamethasone potentiates the PTH stimulation of adenylate cyclase in these cells, yielding a detectable response to as little as 10 pM PTH. Isoproterenol stimulation was also enhanced. The dexamethasone effect is first apparent at 12 h and increases with time of treatment. The apparent EC50 for dexamethasone is 3 nM. Hydrocortisone and corticosterone act similarly to dexamethasone, but require 30-fold higher concentrations. Dexamethasone treatment produces no change in high affinity phosphodiesterase activity. Glucocorticoid-potentiating effects are much more pronounced in whole cells than in broken cells and do not influence forskolin stimulation. Particulate fractions of dexamethasone-treated cells have higher adenylate cyclase specific activity, but are stimulated by guanyl-5'-yl imidodiphosphate to the same extent as control cells. These findings suggest that the glucocorticoids potentiate hormone responsiveness through promotion of hormone receptor-adenylate cyclase coupling by a mechanism dependent on cellular integrity.
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PMID:The effect of dexamethasone on parathyroid hormone stimulation of adenylate cyclase in ROS 17/2.8 cells. 608 91

The effect of parathyroid hormone (PTH 1-34 bovine) on alkaline phosphatase activity was investigated in an osteoblast-like clonal cell line derived from rat osteosarcoma (ROS 17/2). ROS 17/2 alkaline phosphatase resembled the bone enzyme in levamisole sensitivity and electrophoretic mobility but differed in heat stability. The specific activity of ROS 17/2 alkaline phosphatase increased with time in culture. This increase was inhibited by PTH (1-34) and (-)-isoproterenol in a dose-dependent manner starting at near-physiological hormone concentrations. The ID50 values were 0.02 nM for PTH (1-34) and 1.7 nM for isoproterenol. The two hormones stimulated ROS 17/2 adenylate cyclase, albeit at higher concentrations: Km values were 13 nM for PTH (1-34) and 16 nM for isoproterenol. The rise in alkaline phosphatase was also inhibited by dibutyryl cyclic AMP and 8-bromocyclic AMP (0.1 mM). These findings further document the osteoblastic properties of the ROS 17/2 osteosarcoma cell line, suggest that PTH inhibition of alkaline phosphatase represents a physiological response to the hormone in these cells, and implicate cyclic AMP as a mediator of this PTH effect.
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PMID:Alkaline phosphatase inhibition by parathyroid hormone and isoproterenol in a clonal rat osteosarcoma cell line. Possible mediation by cyclic AMP. 627 55

Our experiments have delineated the flow of information in the cyclic nucleotide cascade of vision of ROS. A single, photoexcited rhodopsin molecule activates several hundred phosphodiesterase molecules in two stages. First, photoexcited rhodopsin (R*) interacts with transducin (T), a peripheral membrane protein consisting of alpha- (39 kD), beta- (36 kD), and gamma- (approximately 10 kD) subunits. R* catalyzes the exchange of GTP for GDP bound to the subunit of transducin. About 500 T alpha- GTPs are produced per photoexcited rhodopsin at low light levels. T alpha-GTP, released from the beta- and gamma-subunits of transducin, then interacts with the phosphodiesterase to relieve the inhibitory constraint imposed by its gamma-subunit. Hydrolysis of GTP bound to T alpha serves to restore the system to the dark state. Transducin is the amplified signal carrier in this light-triggered cascade. The formation of hundreds of T alpha- GTPs is likely to be the first stage of amplification in visual excitation. The photoactivation of the phosphodiesterase in ROS closely resembles the activation of adenylate cyclase in hormone-sensitive cells. Our cholera toxin labeling studies have shown that transducin is akin to the signal-coupling G protein of the adenylate cyclase system. Cholera toxin specifically ADP- ribosylates and inactivates the GTPase activity of T alpha, just as it does with Gs. The action of pertussis toxin on ROS further underscores the homology of the photoreceptor and hormone-responsive systems. It seems likely that transducin, the stimulatory G protein, and the inhibitory G protein are members of the same family of signal-amplifying proteins. The study of the cyclic nucleotide cascade of vision is proving to be rewarding in affording a view of a recurring motif of signal amplification in nature in addition to providing insight into the mechanism of vision.
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PMID:Transducin and the cyclic GMP phosphodiesterase: amplifier proteins in vision. 632 79

The culture media of three cell lines, a human prostate carcinoma (PC3), a rat Leydig cell tumor (Rice-500), and a rat carcinosarcoma (WRC-256), that were derived from tumors associated with humoral hypercalcemia of malignancy (HHM), were examined for stimulation of adenylate cyclase in ROS 17/2.8 osteoblastic cells and for bone resorptive activity in culture. Cells from a nonhypercalcemic variant of the WRC256 tumor served as control. Extracts from three solid human tumors, a lung adenocarcinoma from a patient with HHM and two adenocarcinoma from normocalcemic patients (lung and colon), were also examined for adenylate cyclase stimulation. We found excellent correlation between stimulation of cyclic AMP accumulation in ROS 17/2.8 cells and bone resorbing activity in culture, or production of HHM in vivo. Stimulation of adenylate cyclase by HHM factors was inhibited by the parathyroid hormone competitive inhibitor, [8norleucyl, 18norleucyl, 34tyrosinyl] bovine parathyroid hormone (3-34) amide.
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PMID:Factors associated with humoral hypercalcemia of malignancy stimulate adenylate cyclase in osteoblastic cells. 668 37

1. Mg2+ concentration dependence of adenylate cyclase activity, in a rat osteosarcoma cell line (ROS 2/3), exhibits two apparent affinities with Km values of approx. 2 mM and 10 mM. 2. Only one Mg2+ affinity with a Km value of around 1 mM was apparent at saturating concentrations of: (i) guanosine-5'-(beta, gamma-imido)triphosphate; (ii) parathyroid hormone and GTP; and (iii) (-)-isoproterenol and GTP. 3. Conversely, at saturating concentrations of Mg2+ (40 mM) only high hormone concentrations, acting on low affinity sites, stimulated adenylate cyclase. 4. At saturating concentrations of guanosine-5'-(beta, gamma-imido)triphosphate, hormone stimulation decreased with increasing Mg2+ concentrations and none was seen at 40 mM Mg2+. The findings suggest that hormone stimulation of adenylate cyclase is associated with Mg2+ activation of a 'high hormone affinity' responsive state dependent on triphosphoguanine nucleotide. The hormone effect on Mg2+ affinity fully accounts for hormone stimulation of adenylate cyclase at physiologically relevant concentrations.
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PMID:The role of Mg2+ in hormone stimulation of rat osteosarcoma adenylate cyclase. 693 17


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