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)

Vasoactive intestinal peptide (VIP) receptors were characterized in epithelial plasma membranes from human small intestine. Native VIP inhibited the binding of 125I-labeled VIP to jejunal membranes, and Scatchard analysis of these data was consistent with the existence of one class of receptor with a dissociation constant of 42 pM and a maximal binding of 256 fmol/mg membrane protein. VIP stimulated adenylyl cyclase activity in human jejunal membranes in the 0.01 nM-1 microM range [half-maximal effective dose = 0.7 nM]. Coupling of VIP receptors with a Gs protein was further assessed by the ability of GTP (10(-8) to 10(-3) M) to inhibit 125I-VIP binding to membranes. 125I-VIP binding was seven to eight times higher in villus cells than in crypt cells. Finally, 125I-VIP binding was detectable throughout the small and large intestines with the highest binding in jejunum. Among the natural peptides structurally related to VIP, some inhibited 125I-VIP binding with the following order of potency: VIP = pituitary adenylate cyclase-activating peptide (PACAP)-27 = PACAP-38 > helodermin >> peptide histidine methionineamide = human growth hormone-releasing factor > secretin. The same order of potency of peptides for inhibiting 125I-VIP or 125I-labeled PACAP was observed, supporting that the two tracers bound to a common VIP-PACAP receptor site. This order of potency was also observed for the stimulation of adenylyl cyclase activity by these peptides. 125I-VIP was cross-linked to membranes using disuccinimidyl suberate. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, one single band of 70,000 mol wt was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of a common VIP-PACAP receptor in human small intestinal epithelium. 838 39

The binding of ovine pituitary adenylate cyclase-activating peptide (PACAP-38) to rat lung membranes was investigated using [125I]PACAP-38 as radioligand. Binding was rapid at 37 degrees C, reversible, saturable, and time, concentration, and temperature dependent. Kinetic parameters derived from saturation experiments revealed a Kd = 100 +/- 15 pM, Bmax = 310 +/- 36 fmol/mg protein, and a Hill slope factor (nH) of 1.17 +/- 0.12. Various chemically synthesized analogues of PACAP-38, as well as related peptides, were tested for their ability to displace [125I]PACAP-38. Of those that had an IC50 < 0.2 microM, the following order of potency was determined: PACAP-38 (IC50 = 25 nM) > or = [Ile2]PACAP-38 (IC50 = 31 nM) > PACAP-27 (IC50 = 54 nM) > [Tyr1]PACAP-38 (IC50 = 104 nM) > GHRH(1-29)NH2 (IC50 = 108 nM) > PHI (IC50 = 181 nM) > [Ser2]PACAP(2-38) (IC50 = 198 nM). Glucagon, PHM, secretin, and GIP exhibited little affinity in the same binding assay. Vasoactive intestinal peptide (VIP) had an IC50 in excess of 1 microM. When [125I]VIP was used as radioligand, PACAP-27 had an IC50 = 0.2 nM > PACAP-38 (IC50 = 0.5 nM) > VIP (IC50 = 16 nM). A novel analog of PACAP-38, [4-Cl-D-Phe6,Leu17]PACAP-38, was able to displace [125I]VIP very efficiently (IC50 = 1 nM), but had little potency in displacing [125I]PACAP-38 (IC50 = 320 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Interaction of ovine pituitary adenylate cyclase-activating peptide (PACAP-38) with rat lung membranes. 839 24

Pituitary tumorigenesis is characterized by initiation, implying spontaneous or acquired mutations and promotion, implying that tumour expansion is sustained by intrinsic or extrinsic promoting factors. Pituitary tumours have a doubling time of 100 to 700 days. Seventy per cent of cases occur in 30 to 50-year-old patients, but tumours with highest growth rate (prolactin and ACTH-secreting adenomas) are also encountered in patients < 20 years. Pituitary adenomas occur at a greater frequency in females but there is no vivo evidence for a direct role of sex hormones. Oestrogen can amplify tumour growth factors in pituitary cell lines. One-third of GH-secreting adenomas have elevated cAMP resting levels which appear to be caused by a somatic mutation in the Gs protein associated with the GHRH receptor. This maintains the adenylate cyclase system in a turned-on state. Patients with mutant Gs protein have higher GH levels, reduced GHRH response, elevated TRH response, good suppressibility by SRIH and smaller tumour size compared to other acromegalic patients. Hypothalamic releasing hormones may be able to sustain pituitary tumour development since some acromegalic patients with GHRH-secreting tumours may harbour a pituitary GH-secreting adenoma. A lack of inhibitory factors may also have a promoting role in tumour progression.
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PMID:Epidemiology and pathogenesis of pituitary adenomas. 839 32

Growth hormone-releasing hormone (GHRH) belongs to the family of gut-neuropeptide hormones which also includes glucagon, secretin and vasoactive intestinal peptide (VIP). All receptors for this peptide hormone family seem to involve similar signal transduction pathways. Upon hormone binding, these receptors interact with guanine nucleotide binding protein 'Gs' and cause the stimulation of adenylate cyclase. The secretin and VIP receptor cDNAs have recently been cloned and found to be homologous to those of calcitonin and parathyroid hormone receptors. Based on cDNA sequences of these receptors, we designed several oligonucleotide primers which were used to amplify two novel porcine pituitary cDNA fragments by the polymerase chain reaction. One novel receptor cDNA fragment was used to screen a porcine pituitary cDNA library and a full-length cDNA encoding a putative porcine GHRH receptor of 451 amino acids was isolated. This putative receptor mRNA is present specifically in porcine anterior pituitary cells and not in eight other porcine tissues as shown by Northern hybridization analysis. The receptor cDNA was subsequently cloned into a mammalian cell expression vector containing the cytomegalovirus promoter. A human kidney tumor cell line (293) stably transfected with this vector was found to express the receptor efficiently and to bind [125I]-GHRH specifically. Furthermore, challenge of the 293 cells expressing the receptor by GHRH leads to efficient stimulation of cytoplasmic cAMP production.
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PMID:Structure and functional expression of a complementary DNA for porcine growth hormone-releasing hormone receptor. 841 47

The growth hormone releasing factor (GRF) stimulated adenylate cyclase activity was evaluated in membrane fractions of anterior pituitary glands from male and female rats and in gonadectomized rats following in vivo gonadal steroid treatments. The baseline adenylate cyclase activity was lower in random estrous cycle female rats as compared with males. When estrous cycle phases were evaluated, diestrus 1 females had a lower basal activity as compared with males, while proestrus females were similar to males. The maximal stimulation of adenylate cyclase activity by GRF (i.e. Vmax) was lower in random estrous cycle female rats than in males. This lower Vmax, relative to males, was more pronounced in diestrus 1 than in proestrus females. There was little difference in the ED50 for GRF-stimulated adenylate cyclase activity among these groups. The adenylate cyclase activity was altered 1 week after gonadectomy or 1 week after gonadectomy plus simultaneous in vivo gonadal steroid treatment. The expression of data as a function of whole tissue (content) or as a function of protein (concentration) influenced magnitude and direction of these treatment effects. This may reflect the proliferation of nonsomatotroph cell populations and altered protein synthetic activity following reproductive endocrine manipulations. When expressed as a whole tissue content, the baseline adenylate cyclase activity was unchanged after gonadectomy when compared to same-sex, gonadal-intact cohorts. However, an increase in the Vmax for GRF-stimulated adenylate cyclase activity was found in gonadectomized rats relative to sham-operated, gonadal-intact cohorts.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of in vivo reproductive endocrine state on growth hormone-releasing factor stimulated adenylate cyclase activity in anterior pituitary fragments. 847 17

Several evidence suggest that pituitary adenylate cyclase activating polypeptides (PACAP-38 and -27) could function as hypophysiotropic factors. Both peptides interact with either the type I receptor, which preferentially binds the two PACAPs and has a much lower affinity for vasoactive intestinal polypeptide (VIP) or the type II receptor, which binds the two PACAPs and VIP with a nearly equal affinity. In addition to the stimulation of adenylyl cyclase (AC) activity, in different cell types PACAP causes an increase of cytosolic calcium levels ([Ca2+]i), consequent to phospholipase-C activation. In the present study, we investigated the effect of PACAP on cAMP formation and [Ca2+]i levels in 16 human nonfunctioning pituitary adenomas (NFPA). PACAP-38 increased cAMP formation in all tumors; the peptide stimulated either AC activity in membrane preparations from 26 +/- 10 to 214 +/- 179 pmol/mg prot/min (P < 0.01) or cAMP efflux from 12 +/- 5.4 to 73.2 +/- 32 pmol/well (P < 0.01) in cultured cells. The effect, detectable at concentrations higher than 1-10 pM, was maximal at 0.1-10 nM. While PACAP-38 and PACAP-27 were nearly equally effective and potent, 100-fold higher concentrations of VIP were required to obtain similar AC activation. GHRH and CRH were ineffective in any NFPA. The PACAP effect was not antagonized by a VIP antagonist, while PACAP fragment 6-27 amide partially reduced the stimulatory effects of both PACAP-27 and VIP in 2 out of 3 tumors tested. PACAP-38 caused a [Ca2+]i rise in cells obtained from 7 NFPA (from 110 +/- 34 to 151 +/- 40 nM [Ca2+]i, P < 0.05) while in the remaining 7 the peptide was ineffective at any concentrations tested (from 1 nM to 10 microM). In the responsive tumors, PACAP-38 effect was not consequence of phospholipase-C activation since removal of extracellular Ca2+ as well as blockade of L-type Ca2+ channels by dihydropyridine antagonists abolished [Ca2+]i increase triggered by the peptide. These data indicate that PACAP is by far the most potent activator of cAMP formation in NFPA and suggest a possible modulatory action of this peptide on cell growth.
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PMID:Mechanism of action of pituitary adenylate cyclase-activating polypeptide (PACAP) in human nonfunctioning pituitary tumors. 854 47

In the present study, the effects of vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase-activating polypeptides, PACAP27 and PACAP38, in a concentration range from 10(-13) to 10(-6) mol/L were studied in vitro on the spontaneous and dexamethasone (DEX)-induced apoptosis in rat thymocytes. The results show that VIP and both PACAPs inhibit significantly and in a similar way the DNA fragmentation characteristic of glucocorticoid-induced apoptosis and increase the cell survival of thymocytes, with a maximal effect observed at 10(-8) to 10(-9) mol/L. This study showed the ability of the VIP-receptor (VIP-R) antagonist [N-Ac-Tyr1,D-Phe2]-GRF(1-29) amide to partially reverse the inhibitory effect of VIP and both PACAPs on DEX-induced apoptosis, providing evidence for a specific VIP1-R-mediated response and supporting the involvement of a single receptor for the three neuropeptides. Phenotypic analysis showed that VIP, PACAP27, and PACAP38 protect predominantly CD4+CD8+ thymocytes from glucocorticoid-induced apoptosis. These findings suggest that these neuropeptides could be involved in intrathymic T-cell maturation.
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PMID:Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptides (PACAP27) and PACAP38) protect CD4+CD8+ thymocytes from glucocorticoid-induced apoptosis. 865 28

We stably transfected Chinese hamster ovary (CHO) cells with the recombinant human vasoactive intestinal peptide (VIP)1 receptor. A clone referred to as Clone 15 was isolated and studied for receptor properties. The following data were obtained: (1) one class of binding site was identified by Scatchard analysis of [125I]VIP binding to cell membranes with a Kd of 0.41 nM and a Bmax of 1.62 pmol/mg protein; (2) the constant Ki for the inhibition of [125I]VIP binding by VIP and related peptides was: VIP (0.9 nM) = pituitary adenylate cyclase-activating peptide (PACAP)-27 (1.3 nM) < PACAP-38 (6.8 nM) < helodermin (46.0 nM) < human growth hormone-releasing factor (GRF) (0.6 microM) < peptide histidine methionineamide (2.0 microM) < secretin (> 10 microM); (3) cross-linking experiments using [125I]VIP identified a single M(r) 67000 recombinant receptor; (4) VIP stimulated cAMP production in Clone 15 cells with an EC50 of 0.20 nM; (5) some previously described VIP receptor antagonists including [4-Cl-D-Phe6, Leu17]VIP, [Ac-Tyr1,D-Phe2]GRF-(1-29) amide and VIP-(10-28) inhibited [125I]VIP binding with a Ki of 0.7, 1.6 and 2.5 microM, respectively. They failed to stimulate cAMP production in Clone 15 cells and inhibited, at least partially, the VIP (0.3 nM)-evoked cAMP production; (6) exposure of Clone 15 cells to 10 nM VIP for 24 h resulted in a sharp decrease in Bmax in Clone 15 cells (0.43 vs. 1.62 pmol/mg protein in control cells) and in the potency and efficacy of VIP in stimulating cAMP. Moreover, immunofluorescence studies using confocal microscopy indicated that the receptor was internalized and sequestered in vesicular structures within the cells. It is concluded that Clone 15 cells provide a valuable tool to further characterize various functional and pharmacological aspects of the human VIP1 receptor.
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PMID:Stable expression of the recombinant human VIP1 receptor in clonal Chinese hamster ovary cells: pharmacological, functional and molecular properties. 879 Oct 9

The effects of psycholeine, a plant alkaloid, were investigated on binding of radiolabelled somatostatin ([125I]N-Tyr-SRIF) and on somatostatin (SRIF)-induced inhibition of adenylate cyclase activity and growth hormone (GH) secretion by rat anterior pituitary cells. Psycholeine was shown to displace specific binding of [125I]N-Tyr-SRIF to pituitary membrane preparations, with an IC50 of 10(-5) M. At this concentration, psycholeine was also effective in significantly reducing the SRIF-induced inhibition of adenylate cyclase activity previously stimulated by growth hormone releasing factor (GRF). In parallel, it reduced the SRIF-induced inhibition of GH release stimulated by GRF in primary pituitary cell cultures in a dose-dependent manner. At a moderate concentration, the alkaloid affected neither adenylate cyclase activity nor GH release when applied in the absence of SRIF. These data suggest that psycholeine has antagonistic properties at the SRIF receptor. Quadrigemine C, a precursor of psycholeine, has a similar action.
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PMID:Psycholeine, a natural alkaloid extracted from Psychotria oleoides, acts as a weak antagonist of somatostatin. 884 7

The biological effects of VIP are mediated by at least two VIP receptors: the VIP1 and the VIP2 receptors that were cloned in rat, human and mice. As the mRNA coding for each receptor are located in different tissues, it is likely that each receptor modulates different functions. It is therefore of interest to obtain selective agonists for each receptor subtype. In the present work, we achieved the synthesis of two VIP1 receptor selective agonsits derived from secretin and GRF. [R16]chicken secretin had IC50 values of binding of 1,10,000, 20, and 3000 nM for the rat VIP1-, VIP2-, secretion- and PACAP receptors, respectively. This peptide, however, had a weaker affinity for the human VIP1 receptor (IC50 of 60 nM). The chimeric, substituted peptide [K15, R16, L27]VIP(1-7)/GRF(8-27) had IC50 values of binding of 1,10,000, 10,000 and 30,000 nM for the rat VIP1-, VIP2-, secretin- and PACAP receptors, respectively. Furthermore, its also showed an IC50 of 0.8 nM for the human VIP1 receptor and a low affinity for the human VIP2 receptor. It is unlikely that this GRF analogue interacted with a high affinity to the pituitary GRF receptors as it did not stimulate rat pituitary adenylate cyclase activity. The two described analogues stimulated maximally the adenylate cyclase activity on membranes expressing each receptor subtype.
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PMID:Development of high affinity selective VIP1 receptor agonists. 943 14


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