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)

Cytochrome P-450scc (P-450scc) catalyzes the cholesterol side-chain cleavage reaction, a rate-limiting enzymatic step for progesterone synthesis in trophoblastic and other steroidogenic cells. Adrenodoxin is the iron/sulfur protein donating electrons to P-450scc during this reaction. We examined the effects of cholera toxin (CT), an activator of adenylate cyclase, and 12-O-tetradecanoylphorbol acetate (TPA), a phorbol ester protein kinase C activator, on the levels of mRNAs encoding P-450scc and adrenodoxin in JEG-3 choriocarcinoma cells. CT induced in a concentration- and time-dependent manner P-450scc and adrenodoxin mRNA levels to 8-fold and 1.5-fold above that of control, respectively. TPA also increased P-450scc and adrenodoxin mRNA levels about 3-fold and 1.5-fold above that of control, respectively. Epidermal growth factor (EGF) was found to weakly induce P-450scc mRNA accumulation with a maximal 20% stimulation above basal levels. The effects of CT and TPA were apparently additive on both mRNAs. The protein synthesis inhibitor cycloheximide diminished basal, CT-, TPA-, and EGF-stimulated P-450scc mRNA accumulation whereas the opposite was observed for the adrenodoxin mRNA. Insulin-like growth factor I (IGF-I) appeared to have no effect on either mRNA. These data indicate that: (1) the accumulation of P-450scc and adrenodoxin mRNAs is mainly controlled by the cyclic adenosine 3',5'-monophosphate (cAMP)-dependent pathway but their stimulation by TPA- and EGF-induced signals may also play a weaker synergistic role; (2) the protein synthesis inhibitor cycloheximide inhibits basal, CT-, TPA- and EGF-stimulated P-450scc mRNA levels while it increases the expression of adrenodoxin mRNA suggesting that in the malignant trophoblasts these two enzyme mRNAs are differentially controlled.
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PMID:Regulation of the cholesterol side-chain cleavage cytochrome P-450 and adrenodoxin mRNAs in cultured choriocarcinoma cells. 131 54

Epidermal growth factor (EGF) treatment of A-431 cells potentiates up to 5-fold the intracellular cyclic AMP (cAMP) accumulation induced by isoproterenol, cholera toxin, forskolin, or 3-isobutyl-1-methylxanthine (IBMX). EGF potentiates cAMP accumulation in several epithelial cell lines which overexpress the EGF receptor including A-431 cells, HSC-1 cells, and MDA-468 cells, and in the A-431-29S clone which expresses a normal complement of EGF receptors. Although EGF potentiates cAMP accumulation, EGF by itself does not measurably alter the basal level of cAMP. EGF rapidly enhances cAMP accumulation (within 1 to 3 min) in A-431 cells treated with these cAMP-elevating agents. EGF potentiation of cAMP accumulation does not reflect enhancement of beta-adrenergic receptor activation and is not a consequence of intracellular cAMP elevation or the concomitant activation of cAMP-dependent protein kinase. Since EGF potentiates accumulation of both intracellular and extracellular cAMP in isoproterenol-treated A-431 cells, EGF does not potentiate intracellular cAMP accumulation by inhibition of cAMP export. EGF potentiation of cAMP accumulation is pertussis toxin-insensitive and does not result from EGF inhibition of cAMP degradation in A-431 cells. These results demonstrate that EGF transmembrane signaling includes an interaction with a component of the adenylate cyclase system and that this interaction stimulates cAMP synthesis resulting in enhancement of cAMP accumulation.
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PMID:Epidermal growth factor potentiates cyclic AMP accumulation in A-431 cells. 169 98

Thyroid function, including growth, is TSH dependent, and most metabolic functions of TSH are thought to be mediated by cAMP. Recently, it has been suggested by several groups that growth may be an exception and that it may not be related to cAMP action. In addition, evidence has accrued indicating that the thyroid-stimulating antibody (TSAb) of Graves' disease, the metabolic actions of which are also cAMP mediated, may not be the goitrogenic agent in that syndrome. To evaluate these concepts, we used functioning rat thyroid cells (FRTL5) in monolayer culture and, as indices of growth, the incorporation of [3H]thymidine ([3H]Tdr) into DNA, the concentration of DNA measured directly, and the percentage of cells in S phase, as assessed by flow cytometry, all studied over 72 h of incubation. TSH, forskolin, and cholera toxin enhanced growth by each criterion and increased the concentration of cAMP in parallel; the effect on cAMP occurred rapidly and was maximal well in advance of influences on growth. In all instances, measures of growth promotion were minimal at 24 h and maximal at 48 h, except for [3H]Tdr incorporation, which was greater at 72 h than at 48 h. 3-Isobutyl-1-methylxanthine (IBMX) and (Bu)2 cAMP were also tested. Both enhanced all indices of growth and were as effective as TSH. Maximal responses to TSH were obtained at 100-200 microU/ml, maximal responses to both IBMX and (Bu)2cAMP occurred at 5 X 10(-4) M, and all three stimulators increased the DNA concentration and [3H]Tdr uptake and induced S phase in at least 20% of all cells in culture. The peak effect on DNA and S phase was consistently at 48 h. Epidermal growth factor (EGF) was shown to increase [3H]Tdr incorporation in a nondose-dependent fashion (10(-10) to 5 X 10(-9) M gave approximately 250% of control) over 1, 2, 3, 5, and 7 days, with no increase in DNA and a slight decrement in the concentration of cAMP. A laboratory standard TSAb-immunoglobulin G was shown to parallel TSH in both increasing cAMP (over 2 h of incubation) and growth stimulation (over 72 h). The data are entirely consistent with the view that TSH-stimulated thyroid growth is mediated by cAMP and that the established action of TSAb on adenylate cyclase is sufficient to explain goiter as well as hyperthyroidism in Graves' disease.
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PMID:Evidence that adenosine 3',5'-monophosphate mediates stimulation of thyroid growth in FRTL5 cells. 242 89

Epidermal growth factor (EGF) stimulated the formation of inositol trisphosphate, inositol bisphosphate, and inositol phosphate in density-arrested BALB/c/3T3 cells pretreated for 1.5-4 h with cholera toxin, a potent activator of adenyl cyclase, and isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor. Concomitant addition of cholera toxin, IBMX, and EGF to cells did not increase inositol phosphate levels, and pretreatment with both agents was more effective than pretreatment with either alone. Pre-exposure of cells to cholera toxin and IBMX also enhanced the increase in inositol phosphates occurring in response to platelet-derived growth factor (PDGF). Preincubation of cells with cholera toxin and IBMX in the presence of cycloheximide abolished the effects of these agents on EGF- and PDGF-stimulated inositol phosphate production as well as the lesser increase in inositol phosphate formation produced by cholera toxin and IBMX in the absence of hormone. Preincubation of cells with cycloheximide did not affect EGF binding or the ability of PDGF to stimulate inositol phosphate formation. Cycloheximide also precluded EGF-induced inositol phosphate production when presented to cells 3 h after addition of cholera toxin and IBMX. These findings show that, under the appropriate conditions, EGF is capable of stimulating inositol phosphate formation in a nontransformed cell line.
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PMID:Epidermal growth factor stimulates formation of inositol phosphates in BALB/c/3T3 cells pretreated with cholera toxin and isobutylmethylxanthine. 244 85

Epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) regulate hormone production in several endocrine cells cultures. We have previously found that 12-O-tetradecanoyl phorbol-13-acetate (TPA), a protein kinase C activator, potentiates the cAMP-mediated secretion of human CB (hCG) in cultured human choriocarcinoma cells. We have now studied whether EGF and IGF-I modify cAMP-mediated hCG secretion in JEG-3 cells, which possess high affinity receptors to these growth factors. EGF, TPA, and cholera toxin (CT), an activator of adenylate cyclase, stimulated the secretion of hCG in a concentration-dependent manner during a 24-h culture period. The maximal effective concentrations of EGF (10 ng/ml), TPA (10 ng/ml), and CT (1.0 ng/ml) exerted 2.3-, 2.4-, and 3.9-fold increase over unstimulated level, respectively. EGF and TPA potentiated the effect of CT on hCG secretion from 3.9- to 7.8-fold and from 3.9- to 14.8-fold, respectively. By contrast, IGF-I was ineffective. During a 24-h culture, EGF and TPA potentiated the effect of CT on cAMP accumulation 1.4-fold and 1.3-fold over the production of CT-treated cells. Time-course studies indicated that these effects on cAMP and hCG were detectable at 3 h and 6 h, and they continued to increase up to 48 h and 72 h, respectively. When added alone, EGF and TPA increased cAMP production y 2.0-fold and 2.5-fold over controls at 24 h. Again, IGF-I was ineffective. Moreover, EGF and TPA potentiated the effect of 8-bromo-cAMP (on hCG production to a similar extent than they did to CT-stimulated hCG production. The binding of [125I]iodo-EGF to the cells was not altered by a 48-h CT-treatment whereas the binding of [125I]iodo-IGF-I was increased by 2.1-fold above untreated cells. Our data show that both EGF and TPA potentiated the effect of CT on hCG secretion in JEG-3 cells, whereas IGF-I had no effect. Although EGF and TPA facilitated CT-stimulated cAMP accumulation, their site of action on cAMP-mediated hCG production is distinct from the adenylate cyclase or EGF-receptor level since EGF and TPA potentiated the hCG secretion stimulated by 8-bromo-cAMP and an increase in cAMP production did not alter the binding properties of EGF-receptor.
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PMID:Epidermal growth factor but not insulin-like growth factor-I potentiates adenosine 3',5'-monophosphate-mediated chorionic gonadotropin secretion by cultured human choriocarcinoma cells. 284 Feb 69

The hormonal regulation of inhibin production by cultured granulosa cells from immature hypophysectomized, estrogen-treated rats was examined using a specific RIA which detects the N-terminal portion of the inhibin alpha-chain. The RIA measured bioactive inhibin of Mr about 32,000 in granulosa cell conditioned media fractionated by fast protein liquid chromatography. In the presence of 10(-7) M androstenedione, FSH stimulated inhibin production in a dose-dependent manner during a 2-day culture. Inclusion of a phosphodiesterase inhibitor decreased the EC50 for FSH from 2.6 to 0.8 ng/ml (n = 3). The stimulatory effect of FSH could be mimicked with forskolin (an adenyl cyclase activator) and with a cAMP analog, (Bu)2cAMP, consistent with FSH action mediated through a cAMP dependent pathway. Intracellular levels of inhibin were unmeasureable, suggesting that inhibin is not stored to any great extent by the granulosa cells. This finding was consistent with in vivo studies which showed that whereas FSH treatment for 2 days doubled serum inhibin levels when compared with basal levels, there was no increase in the concentration of extractable inhibin in ovarian tissue. Granulosa cells which had been exposed to 20 ng/ml FSH for 2 days to induce LH receptors produced inhibin in response to both LH and human CG during the subsequent 2-day culture, with the levels of inhibin equalling the amount inducible by FSH. In contrast, neither PRL nor terbutaline, a beta 2-adrenergic agonist, had any effect on inhibin production even though receptors for these hormones are also induced by FSH. GnRH was found to inhibit the FSH-stimulated production of inhibin (IC50, 10(-7) M), consistent with previous observations that GnRH can act at the ovarian level to inhibit granulosa cell differentiation. This inhibition by GnRH could be reversed by inclusion of a specific GnRH antagonist. On the other hand, another regulatory peptide, vasoactive intestinal peptide, slightly stimulated inhibin production. The effect of several growth factors was also tested. Insulin-like growth factor I raised not only FSH-stimulated inhibin levels, but basal levels as well. Insulin was also effective, but only at 100-fold higher concentration. Epidermal growth factor inhibited FSH-stimulated inhibin production (IC50 = 0.1 ng/ml), whereas fibroblast growth factor had no effect. Thus, granulosa cell inhibin secretion is regulated by FSH and LH but not by PRL, presumably via a cAMP-mediated pathway.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Hormonal regulation of granulosa cell inhibin biosynthesis. 302 19

Epidermal growth factor (EGF) causes rapid increases in free intracellular Ca2+ and stimulates the phosphorylation of 11 cytosolic proteins in hepatocytes. Ten of the 11 cytosolic proteins altered by EGF are identical to those affected by angiotensin II, a hormone that stimulates the breakdown of phosphatidylinositol 4,5-bisphosphate. An increase in the phosphorylation of the other protein, spot c (Mr = 36,000, pI = 5.5), is observed only with EGF. Treatment of intact rats with pertussis toxin to ADP-ribosylate Ni, the inhibitory GTP-binding protein of the adenylate cyclase complex, abolished the effect of EGF on Ca2+ mobilization and on the phosphorylation of the 10 proteins affected in common with angiotensin II. This treatment had minimal effects on the ability of EGF to stimulate the phosphorylation of its unique substrate, spot c. In marked contrast, modification of Ni did not block the ability of angiotensin II to stimulate Ca2+ mobilization or protein phosphorylation. Pretreatment of normal hepatocytes with 4 beta-phorbol 12-myristate 13-acetate blocked all responses to EGF, including the increased phosphorylation of spot c, but had no effect on the responses to angiotensin II. These results imply that Ni or a similar pertussis toxin substrate may mediate the apparent effects of EGF on phosphatidylinositol breakdown and that protein kinase C may regulate a site in the transduction pathway. Angiotensin II appears to use a different signal transduction mechanism to stimulate phosphatidylinositol metabolism in hepatocytes.
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PMID:Pertussis toxin or phorbol 12-myristate 13-acetate can distinguish between epidermal growth factor- and angiotensin-stimulated signals in hepatocytes. 308 11

Thyroid-stimulating hormone (TSH) has been shown to stimulate mitosis in cultures of the continuous thyroid cell strain FRTL-5, and this system may be used to quantify the growth-promoting effects of thyroid stimulators. Removal of TSH from the culture medium led to a progressive decline in the metaphase index (MI) to zero, after 7 days. Thus the cell culture conditions may be manipulated so that metaphases are absent in control cultures, i.e. in the absence of TSH. Restimulation with TSH caused an increase in mitosis only after a lag-phase of 20-24 h. A maximum MI was observed between 40 and 50 h, with a secondary peak between 70 and 75 h. An immunoglobulin G (IgG) preparation from a thyrotoxic patient with a small goitre which was a potent stimulator of adenylate cyclase in these cells produced a similar time-course. A dose-response relationship to TSH was obtained 47 h after addition of the hormone. Significant stimulation was observed with 10 mu. TSH/l, and maximal stimulation with 1 unit TSH/l; the highest dose tested (10 units TSH/1) slightly decreased the MI below the maximum. Stimulation of these cells appeared to be TSH specific, since FSH, human chorionic gonadotrophin, LH and isoproterenol did not induce mitosis. Epidermal growth factor under the experimental conditions employed was unable to induce mitosis. However, an increase in mitosis was observed with the adenylate cyclase stimulator forskolin. These experiments confirm the mitogenic properties of TSH and we describe a metaphase index assay for the detection of thyroid growth promotors.
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PMID:Thyrotrophin stimulation of mitogenesis of the rat thyroid cell strain FRTL-5: a metaphase index assay for the detection of thyroid growth stimulators. 404 May 48

The influence of calcitonin on cell growth was examined in the human breast cancer cell line, T 47D. These cells possess specific high-affinity receptors for calcitonin as well as a sensitive calcitonin-responsive adenylate cyclase. In the T 47D cells, low doses of salmon calcitonin initially stimulated cell growth and the incorporation of [3H]thymidine into acid-insoluble macromolecules. This initial stimulation was followed by an inhibitory effect of calcitonin upon cell proliferation, which occurred during the log phase of growth, was dose dependent, and resulted in prolongation of doubling time from 36 to 90 hr. DNA and protein content correlated well with cell number. By 7 to 9 days of treatment, cell numbers of calcitonin-treated cells reached a mean of 66.5 +/- 3.7% of control (p less than 0.001, n = 8) (range, 51.3 to 82.9%). This biphasic effect of calcitonin on T 47D cells was reproduced by human calcitonin and prostaglandin E2 in the order of potency with which they influence adenylate cyclase. Epidermal growth factor (10(-9)M) and insulin (10(-9)M) stimulated the growth of T 47D cells, but this effect was abolished when either hormone was combined with salmon calcitonin (3 x 10(-10)M). Calcitonin specifically activated type II isoenzyme of cyclic adenosine 3':5'-monophosphate-dependent protein kinase in the T 47D cells. In view of other published data relating activation of this isoenzyme to growth regression in cancer cells, this response to calcitonin may be causally related to the inhibitory effect of the hormone upon cell replication in T 47D cells. The mechanism of the early stimulatory effect of calcitonin upon mitogenesis is not explained, although the possibility of stimulation of activity of type I isoenzyme of cAMP-dependent protein kinase has not been entirely excluded in the present experiments.
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PMID:Calcitonin effects on growth and on selective activation of type II isoenzyme of cyclic adenosine 3':5'-monophosphate-dependent protein kinase in T 47D human breast cancer cells. 618 57

Recent evidence suggests that epidermal growth factor (EGF) may play an important role in the regulation of thyroid growth and function. We have examined the interaction of murine EGF (mEGF) with human and porcine thyroid membranes and compared this with the binding of bovine TSH (bTSH) using 125I-labelled hormones as tracers. The characteristics of the binding of mEGF were found to be similar for human and porcine thyroid membranes. Epidermal growth factor bound with high affinity (affinity constant = 1.4 X 10(9) l/mol); the density of binding sites was low compared with the TSH receptor. At 37 degrees C, the binding of 125I-labelled EGF was maximal at 1 h and was saturable in the presence of unlabelled EGF; half-maximal inhibition was at 1 ng EGF/tube (0.5 nmol/l) using 0.5 mg membrane protein/tube. Unlabelled bTSH had no effect on the binding of labelled EGF. Similarly, unlabelled EGF did not affect the binding of labelled TSH; hence it was concluded that mEGF and bTSH bound to independent sites. Epidermal growth factor had no effect on adenylate cyclase activity in membranes prepared from human non-toxic goitre; increasing concentrations of EGF did not affect basal, TSH-stimulated or fluoride-stimulated enzyme activity.
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PMID:Interaction of epidermal growth factor with receptors on human and porcine thyroid membranes. 633 Feb 67


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