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)

Parathyroid hormone and parathyroid hormone-related protein lower blood pressure and relax contracted arteries. Parathyroid hormone also attenuates angiotensin II-induced vasoconstriction. To determine the cellular mechanism or mechanisms by which parathyroid hormone analogues antagonize pressor effects, we examined the effect of these peptides on angiotensin II-induced calcium mobilization in fura 2-AM-loaded cultured rat vascular smooth muscle cells. Either 100 nmol/L parathyroid hormone or parathyroid hormone-related protein significantly reduced the amount of calcium mobilized by 100 nmol/L angiotensin II. The attenuating effect of these peptides was mimicked by 10 mmol/L forskolin and 10 mmol/L isobutylmethylxanthine and was not dependent on the presence of extracellular calcium. This effect of the parathyroid hormone analogues was reduced when cells were pretreated with 100 mmol/L 2',5'-dideoxyadenosine, an adenylate cyclase inhibitor. Combined inhibition of cyclic nucleotide-dependent protein kinases eliminated the inhibitory effect of parathyroid hormone, whereas protein kinase C inhibition had no effect. Parathyroid hormone analogues decreased the amount of calcium released by inositol 1,4,5-trisphosphate in digitonin-permeabilized vascular smooth muscle cells. This effect was inhibited by treatment with 2',5'-dideoxyadenosine. These results suggest that these peptides attenuate inositol 1,4,5-trisphosphate-sensitive calcium mobilized by angiotensin II via an adenylate cyclase-dependent mechanism. This may be a mechanism by which acute administration of parathyroid hormone or parathyroid hormone-related peptide antagonizes vasoconstriction.
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PMID:Parathyroid hormone analogues inhibit calcium mobilization in cultured vascular cells. 812 68

Parathyroid hormone (PTH) has been shown to have actions within the brain, suggesting the presence of central PTH receptors. This possibility was examined by determining the binding of 125I-labeled [Nle8,18,Tyr34]bovine PTH to the plasma membranes of rat and rabbit brains. Specific binding of the tracer to membranes of the whole brain was time and tissue dependent, and was greater with membranes from the hypothalamus than with membranes from the cerebellum, cerebrum, or brain stem. The binding of the tracer to rat hypothalamic membranes was saturable and competitively displaced by unlabeled PTH(1-34), PTH(3-34), [Nle8,18,Tyr34]PTH(1-34), and by PTH-related protein, indicating the presence of a single class of high-affinity (dissociation constant = 2-5 nM), low-capacity (maximum binding capacity, Bmax = 110-250 fmol/mg protein) binding site. The binding of radiolabeled PTH to these sites was not displaced by unrelated peptides of comparable molecular size (calcitonin, calcitonin-gene related peptide, adrenocorticotropin). The binding of PTH to these sites did not, however, appear to stimulate adenylate cyclase activity, as in peripheral PTH target sites. Thus, although these results indicate the presence of PTH receptors in the brain, these binding sites have a lower affinity than those in peripheral tissues and may utilize a different signal transduction system.
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PMID:Parathyroid hormone binding sites in the brain. 813

The receptor for parathyroid hormone (PTH) and PTH-related protein (PTHrP) is a member of a subfamily of G-protein-coupled receptors. This subfamily includes receptors for calcitonin, secretin, vasoactive intestinal polypeptide, glucagon, and related peptides, growth hormone-releasing hormone, and pituitary adenylate cyclase activating peptide. These receptors couple agonist occupancy to activation of adenylate cyclase and, in some cases, to increases in Cai2+, but the molecular basis of signalling is unclear Mutagenesis studies of recombinant PTH/PTHrP receptors indicates that large portions of the third intracellular loop and C-terminal tail can be deleted and/or mutated without major loss of receptor-G-protein interaction, as evidenced by high affinity ligand binding and signal transduction. However, specific determinants in these domains appear to modulate the efficiency of effector activation. Further studies are needed to define the contact sites for PTH/PTHrP receptor-G-protein interaction.
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PMID:Structure and function of the receptor for parathyroid hormone and parathyroid hormone-related protein. 816 70

Parathyroid hormone-related protein (PTHrP) plays a major role in the pathogenesis of humoral hypercalcemia of malignancy. It interacts with the PTH receptor and has therefore a nearly identical effect on bone cells as PTH. However, PTHrP is thought to be less potent than PTH in stimulating adenylate cyclase in canine renal membranes, leading to the hypothesis of a differential efficiency in signal transduction by PTHrP with respect to bone vs kidney. In a homologous model with intact osteoblast-like cells (UMR 106) and primary kidney cells, both from the rat, we have tested N-terminal peptide fragments, based on the rat amino acid sequence 1-34, of PTH and PTHrP. Compared with PTHrP(1-34), rat PTH(1-34) had a similar relative potency in bone cells (85%) and in kidney cells (140%) in its ability to stimulate adenylate cyclase. Human PTH(1-34) was 5.6- to 6.5-fold less potent than rat PTH(1-34) in both cell types. In human osteoblast-like cells (SaOS-2), rat and human PTH were essentially equally potent compared to PTHrP(1-34) (identical sequence in rat and human) in stimulating cAMP accumulation. In conclusion, our study revealed the equipotency of rat PTH(1-34) and PTHrP(1-34) in stimulating intracellular cAMP formation in a homologous system of rat bone and kidney cells. There seemed to be no unique signal transduction mechanism of PTHrP to the adenylate cyclase in rat kidney cells compared with bone cells.
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PMID:Cyclic AMP formation in rat bone and kidney cells is stimulated equally by parathyroid hormone-related protein (PTHrP) 1-34 and PTH 1-34. 822 83

Tumor necrosis factor (TNF-alpha) has been shown to play an important role in local control of bone remodeling. The interaction of TNF-alpha and PTH was evaluated in UMR-106-01 cells, a phenotypic osteoblastic osteosarcoma cell line. We examined the influence of TNF-alpha on the two signal transduction systems triggered by PTH in UMR-106-01 cells, adenylate cyclase and free cytosolic calcium ([Ca2+]i). cAMP generation was inhibited in TNF-alpha-pretreated cells by 69, 61, 34, and 21% at PTH concentrations of 0.1, 1, 10, and 100 nM, respectively. Inhibition was seen at TNF-alpha doses of 100-1500 units/ml after a minimum incubation time of 12 h. TNF-alpha inhibition of the PTH-stimulated increase in [Ca2+]i was even more pronounced: treated cells showed no change in baseline [Ca2+]i after stimulation with 40 nM PTH. Treatment with TNF-alpha was also found to inhibit both arms of the PTH response in the nontransformed osteoblastic cell line, MC3T3-E1. TNF-alpha treatment did not alter cAMP generation in response to PGE2. TNF-alpha inhibition of the PTH-stimulated cAMP response was reversed completely by addition of cholera toxin (5 micrograms/ml) and partially by forskolin (10 microM) but not pertussis toxin (100 and 500 ng/ml). Scatchard analysis using PTHrP revealed that TNF-alpha treatment reduced the number of receptors but had no effect on KD. These findings suggest that TNF-alpha inhibits the osteoblastic response to PTH at least in part because of a reduction in receptor number. Further investigation is indicated to provide insight into the interaction of calciotropic hormones and cytokines in vivo.
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PMID:Tumor necrosis factor alpha modulates parathyroid hormone action in UMR-106-01 osteoblastic cells. 825 56

PTH-related protein (PTHrP), originally identified through its causative role in human humoral hypercalcemia of malignancy, is now known to be a normal gene product expressed in a wide variety of neuroendocrine, epithelial, and mesoderm-derived tissues. PTHrP gene expression has recently been demonstrated in fetal and adult, benign and malignant, as well as human and rodent pancreatic islets. As in other tissues, the role of PTHrP expression in the normal islet is only beginning to be explored. In the current report, PTHrP expression in the normal rat pancreatic islet was confirmed using an affinity-purified antiserum directed against the N-terminal, biologically active region of the molecule. The effects of PTHrP on the islet were then explored using rat insulinoma (RIN m5F) cells. Synthetic PTHrP-(1-36) bound specifically, but with low affinity (Kd, approximately 10(-7) M) to RIN cell membranes. PTHrP-(1-36) failed to stimulate cAMP production in RIN cells, although RIN cells displayed a normal adenylate cyclase response to glucagon-like peptide-1-(7-36). In contrast, PTHrP-(1-36) induced a rapid dose-dependent rise in intracellular calcium in RIN cells in doses as low as 10(-12)-10(-10) M. These findings 1) confirm that PTHrP is expressed by islet cells, 2) demonstrate that the effects of PTHrP on the pancreatic islet are mediated, as in keratinocytes and lymphocytes, by a receptor related to but distinct from the PTH receptor, and 3) suggest that PTHrP functions in the islet as an autocrine or paracrine factor. Further studies are required to determine the physiological consequences of PTHrP expression by the pancreatic islet.
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PMID:Amino-terminal parathyroid hormone-related protein: specific binding and cytosolic calcium responses in rat insulinoma cells. 838 1

Gene fusions have been widely used in heterologous expression systems as a technique to stabilize the recombinant product against proteolysis, increase the translational initiation efficiency or to serve as an affinity handle for the purification of the protein. A further advantage is the potential to generate an authentic amino terminus of the foreign protein when this is vital for its biological activity, such as for the ability of human parathyroid-hormone-related protein (hPTHrP) to mediate activation of adenylate cyclase. We report here the construction and utility of a ubiquitin fusion protein system for production of the otherwise short-lived hPTHrP(1-141) as a carboxyl extension to ubiquitin in yeast. A hybrid gene containing the hPTHrP(1-141) cDNA coding region fused in-frame to the 3' end of the yeast ubiquitin cDNA was constructed and expressed under the control of the regulatable yeast metallothionein promoter. The recombinant protein was purified to homogeneity and finally characterized by N-terminal amino acid sequencing and amino acid composition analysis, demonstrating that the fusion protein was cleaved correctly and quantitatively in vivo by an ubiquitin-specific yeast endoprotease to generate authentic hPTHrP(1-141). hPTHrP(1-141) stimulated adenylate cyclase in rat osteosarcoma cell membranes to the same extent as equimolar amounts of recombinant human parathyroid hormone(1-84) and [Tyr34]hPTHrP(1-34)amide. Thus, this expression cloning strategy permits the production of authentic, biologically active recombinant hPTHrP(1-141), and the procedure can easily be adapted to make PTHrP analogues for further studies of its domain-specific activities and biological roles.
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PMID:Synthesis of human parathyroid-hormone-related protein(1-141) in Saccharomyces cerevisiae. A correct amino-terminal processing vital for the hormone's biological activity is obtained by an ubiquitin fusion protein approach. 838 31

Parathyroid hormone-related protein (PTHrP) or its mRNA transcripts have been documented in a variety of normal tissues, including vascular smooth muscle. A synthetic amino-terminal fragment of PTHrP, PTHrP(1-34), was tested a) for its vasoactive properties in a perfused rat aorta and b) its ability to stimulate cAMP accumulation in cultured rat aorta smooth muscle cells; PTHrP(1-34) was a potent vasodilator and increased cAMP accumulation. The results confirm the potent vasorelaxant properties of PTHrP(1-34), and show that the peptide stimulates adenylate cyclase in vascular smooth muscle cells per se, suggesting, but not proving, linkage of cAMP accumulation to vasorelaxation.
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PMID:Vasoactive properties of a parathyroid hormone-related protein in the rat aorta. 838 85

Studies were conducted to test whether parathyroid hormone-related protein (PTHrP) is able to stimulate adenylate cyclase activity in isolated rabbit glomeruli. Maximal stimulations were reached at 10(-7) M of human PTHrP-(1-34) or rat PTH-(1-34) and showed a 3-3.3 fold increase over basal activity. The potency (EC50) values were close to 10(-9) M. The guanyl nucleotide GTP, at 10(-5) M, potentiated the effect of PTH and PTHrP but reduced their potency. The combined effect of maximal concentrations of PTHrP and PTH was not additive, and the PTH antagonist [Nle8.18, Tyr34]-bPTH-(3-34)amide inhibited both PTHrP- and PTH-stimulated adenylate cyclase activities. These findings suggest that PTHrP could affect glomerular function through changes in glomerular cAMP content by interaction with PTH receptors.
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PMID:Evidence for adenylyl cyclase-dependent receptors for parathyroid hormone (PTH)-related protein in rabbit kidney glomeruli. 839 86

Chicken polyclonal antibodies were prepared against a synthetic peptide corresponding to the first 36 N-terminal amino acids of parathyroid hormone-related protein (PTHrP) by immunizing laying hens. Significant increases of antibodies to PTHrP were first detected after the second immunization. Production of anti-PTHrP egg yolk antibodies peaked 1-2 weeks after the second through sixth immunizations and declined over a period of 2-4 weeks. Polyclonal IgG (IgY) to PTHrP was purified from the egg yolks with high levels of PTHrP specific binding. The anti-PTHrP IgG was used to develop a radioimmunoassay for PTHrP that was able to detect 100 pg PTHrP ml-1 (23 pM) in conditioned cell culture medium. The anti-PTHrP IgG was bound to a solid phase and utilized to immunopurify iodinated [Tyr36]-PTHrP (1-36). Anti-PTHrP IgG inhibited the in vitro biologic activity of PTHrP as demonstrated by the inhibition of adenylate cyclase stimulation in a rat osteoblast-like cell line (ROS 17/2.8). The anti PTHrP IgG was immunopurified and utilized for immunohistochemical localization of PTHrP in canine skin. Chickens were advantageous in producing large amounts of high affinity, neutralizing antibodies to a highly conserved mammalian protein such as PTHrP. The antibodies will be useful to investigate the function and metabolism of PTHrP in vivo and in vitro.
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PMID:Studies on chicken polyclonal anti-peptide antibodies specific for parathyroid hormone-related protein (1-36). 843 Apr 99


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