Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of cAMP and calcium in the induction of ornithine decarboxylase (ODC, E.C.4.1.1.17) activity in the osteogenic sarcoma cell line, UMR 106-01, was studied, with particular interest for parathyroid hormone (PTH). PTH and forskolin dose-dependently induced the ODC activity and the cAMP production. Protein synthesis is involved in the effect of PTH and forskolin on ODC activity but not on cAMP production. Using quin2 we showed that 20 nM PTH and 10 microM forskolin increased the intracellular ionized calcium concentration ([Ca2+]i), thereby offering the possibility for calcium to play a role as cellular mediator in the action of PTH and forskolin in bone. Data obtained with A23187 showed that solely an increase of the [Ca2+]i is not sufficient to stimulate basal or potentiate PTH- and forskolin-induced ODC activity. However, the effects of calcium channel blockers and EGTA on basal and PTH- and forskolin-induced ODC activity point to a specific role for calcium. Moreover, the effects of calcium channel blockers and EGTA on basal and PTH- and forskolin-induced cAMP production indicate that the involvement of calcium in the induction of ODC activity is primarily located at another site than the adenylate cyclase. These data indicate that calcium is involved in the control of basal ODC activity. Furthermore, these data suggest that both cAMP and calcium are involved in the induction of ODC activity by PTH and forskolin. More precisely, ODC activity in UMR 106-01 cells can be induced by PTH and forskolin via a calcium-dependent cAMP messenger system.
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PMID:Involvement of cAMP and calcium in the induction of ornithine decarboxylase activity in an osteoblast cell line. 284 Apr 35

A tumor-derived protein with a spectrum of biologic activities remarkably similar to that of parathyroid hormone (PTH) has recently been purified and its sequence deduced from cloned cDNA. This PTH-like protein (PLP) has substantial sequence homology with PTH only in the amino-terminal 1-13 region and shows little similarity to other regions of PTH thought to be important for binding to receptors. In the present study, we compared the actions of two synthetic PLP peptides, PLP-(1-34)amide and [Tyr36]PLP-(1-36)amide, with those of bovine parathyroid hormone (bPTH)-(1-34) on receptors and adenylate cyclase in bone cells and in renal membranes. Synthetic PLP peptides were potent activators of adenylate cyclase in canine renal membranes (EC50 = 3.0 nM) and in UMR-106 osteosarcoma cells (EC50 = 0.05 nM). Bovine PTH-(1-34) was 6-fold more potent than the PLP peptides in renal membranes, but was 2-fold less potent in UMR-106 cells. A competitive PTH receptor antagonist, [Tyr34]bPTH-(7-34)amide, rapidly and fully inhibited adenylate cyclase stimulation by the PLP peptides as well as bPTH-(1-34). Competitive binding experiments with 125I-labeled PLP peptides revealed the presence of high affinity PLP receptors in UMR-106 cells IC50 = 3-4 nM) and in renal membranes (IC50 = 0.3 nM). There was no evidence of heterogeneity of PLP receptors. Bovine PTH-(1-34) was equipotent with the PLP peptides in binding to PLP receptors. Likewise, PLP peptides and bPTH-(1-34) were equipotent in competing with 125I-bPTH-(1-34) for binding to PTH receptors in renal membranes. Photoaffinity cross-linking experiments revealed that PTH and PLP peptides both interact with a major 85-kDa and minor 55- and 130-kDa components of canine renal membranes. We conclude that PTH and PLP activate adenylate cyclase by binding to common receptors in bone and kidney. The results further imply that subtle differences exist between PTH and PLP peptides in their ability to induce receptor-adenylate cyclase coupling.
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PMID:Synthetic peptides comprising the amino-terminal sequence of a parathyroid hormone-like protein from human malignancies. Binding to parathyroid hormone receptors and activation of adenylate cyclase in bone cells and kidney. 284 1

While the stimulatory effect of parathyroid hormone (PTH) on osteoblast-like cell adenylate cyclase is well known, the effect of PTH on cytosolic calcium ion ([Ca2+]i) mobilization is controversial, one group finding no effect but others reporting various increases. We investigated the effects on [Ca2+]i of synthetic rat PTH fragment 1-34 (rPTH(1-34)) and two bovine PTH analogues that inhibit PTH's stimulation of adenylate cyclase (bovine 8,18Nle, 34Tyr-PTH(3-34) and 34Tyr-PTH(7-34]. [Ca2+]i was measured before, during, and after exposure to PTH analogues in perifused, attached osteoblast-like rat osteosarcoma cells (ROS 17/2.8) that had been scrape-loaded with the luminescent photoprotein aequorin. Resting [Ca2+]i was 0.094 +/- 0.056 microM (mean +/- S.D., n = 103) and rose in a time- and dose-specific way after exposure to rPTH(1-34). At 10(-10) M rPTH(1-34), [Ca2+]i rose 100% within 30 s to a plateau; higher concentrations of PTH yielded increasing initial peaks of [Ca2+]i followed by lower plateaus. At 10(-6) M, the initial peak was 5-fold basal, or 0.64 +/- 0.07 microM. Both analogues of PTH were at least partial agonists for [Ca2+]i mobilization and did not reduce peak [Ca2+]i when co-perifused with rPTH(1-34). However, the analogues did reduce significantly rPTH(1-34)-induced cAMP accumulation and did not increase cAMP accumulation by themselves. Thus, rPTH(1-34) strongly mobilizes [Ca2+]i in ROS 17/2.8 cells, at near-physiologic concentrations. Failure of the PTH analogues to block the effect of PTH on [Ca2+]i while inhibiting the effect on cAMP accumulation suggests separate pathways for PTH activation of adenylate cyclase and mobilization of calcium.
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PMID:Differential effects of parathyroid hormone and its analogues on cytosolic calcium ion and cAMP levels in cultured rat osteoblast-like cells. 284 23

We compared the bioactivities of a synthetic truncated NH2-terminal fragment of the human (h) PTH-like peptide (PLP) associated with malignancies [hPLP-(3-34)], an intact NH2-terminal fragment [hPLP-(1-34)], and an NH2-terminal fragment of PTH [hPTH-(1-34)]. Although hPLP-(1-34) was less potent than hPTH-(1-34) in stimulating adenylate cyclase in rat renal membranes, hPLP-(1-34) and hPTH-(1-34) were equipotent in stimulating adenylate cyclase in OK renal cells as well as in UMR 108 osteosarcoma cells in vitro. In osteosarcoma cells, each of these peptides could desensitize adenylate cyclase responses to itself and to the other peptide, but could not reduce stimulation by prostaglandin E2. Renal membranes of vitamin D-deficient rats with secondary hyperparathyroidism had a reduced PLP-stimulated as well as PTH-stimulated adenylate cyclase response. The truncated analog hPLP-(3-34) was only a weak partial agonist and an antagonist in vitro, produced equivalent inhibition of hPLP-(1-34) and hPTH-(1-34) in renal and osseous cells, and could not desensitize agonist responses. In thyroparathyroidectomized rats in vivo, hPLP-(1-34) and hPTH-(1-34) increased cAMP excretion, enhanced phosphaturia, maintained plasma calcium, and reduced calciuria. Equimolar concentrations of hPLP-(3-34) produced no increases above control levels; however, high concentrations of this peptide mimicked PTH actions on renal and plasma ion handling while modestly augmenting cAMP excretion. These results demonstrate the importance of the first two residues of PLP for bioactivity, indicate that PLP and PTH interact at common receptor sites in vivo as well as in vitro, suggest that PLP may not be less potent than PTH in renal target cells, and indicate that the net result of interaction of these peptides with their common receptor in target tissues may reflect both activation and desensitization of receptor-mediated events.
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PMID:Influence of the amino-terminus on in vitro and in vivo biological activity of synthetic parathyroid hormone-like peptides of malignancy. 284 83

Binding of parathyroid hormone (PTH) to circulating bovine lymphocytes was studied using, as the radioligand, a synthetic sulfur-free analog of bovine PTH, [Nle8,Nle18,Tyr34]bPTH-(1-34)amide, which was labeled to high specific activity with 125I and was purified by reverse-phase high-performance liquid chromatography. Binding of PTH to lymphocytes satisfies several criteria indicative of a specific interaction between the hormone and its receptor. Specific binding is saturable at 3.3 fmoles of radioligand bound per 10(7) cells, occurs more rapidly at 37 degrees C than at lower temperatures, and reaches equilibrium within 2 hr at 15 degrees C. Inhibition of specific binding occurs with intact PTH, with biologically active PTH analog or fragment, and with synthetic PTH antagonists, but not with biologically inactive PTH fragments, or peptide hormones unrelated to PTH antagonists, but not with biologically inactive PTH fragments, or peptide hormones receptors on lymphocytes and those previously reported with receptors in canine renal membranes, and on rat osteosarcoma cells. The dissociation constant (Kd) is approximately 10(-9) M, as calculated from the association and dissociation rate constants. This correlates very closely both with the apparent Kd, as estimated from Scatchard analysis of radioligand saturation and competition studies, and with previously reported Kd of PTH receptors in canine renal membranes and on intact rat osteosarcoma and opossum kidney cells. In addition, the relative binding affinity of intact hormone and a synthetic PTH agonist to to receptors on lymphocytes correlates closely with the relative biologic potency of these peptides in stimulating adenylate cyclase in membranes from these cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Properties of parathyroid hormone receptors on circulating bovine lymphocytes. 285 Jul 27

We identified the subunits of the stimulatory and inhibitory guanine nucleotide binding proteins (Gs and Gi, respectively) associated with adenylate cyclase in rat osteosarcoma (ROS) cells. Pertussis toxin catalyzed ADP-ribosylation of Gi alpha in ROS cells increased agonist (PTH and isoproterenol)-stimulated, but not basal, cAMP production. The effect of pertussis toxin was dose and time dependent, and slowly reversible (T 1/2 approximately 30 h) during continued culture without toxin. Pertussis toxin treatment of ROS cell lines (17/2.8 and 24/l) with markedly different agonist responsiveness increased agonist-stimulated cAMP production in proportion to the response without toxin treatment. Pertussis toxin treatment further increased cAMP response to PTH in dexamethasone treated cells. We conclude that ROS cells contain functional Gi which modulates agonist-stimulated cAMP formation. Alterations in ROS cAMP responsiveness caused by steroids, and the reduced responsiveness of the 24/1 cell line, however, are unlikely to be due to changes in Gi.
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PMID:The inhibitory guanine nucleotide regulatory protein modulates agonist-stimulated cAMP production in rat osteosarcoma cells. 285 47

The effects of glucocorticoids on parathyroid hormone (PTH) receptors was studied using rat osteosarcoma-derived cells (ROS 17/2), which have an osteoblastic phenotype, and [125I][Nle8,Nle18,Tyr34]bovine(b)PTH-(1-34)amide as the radioligand. Treatment of cells with physiologic concentrations of hydrocortisone resulted in a time and dose-dependent increase in PTH binding. The increase in PTH binding could be observed by 10 h of exposure to hydrocortisone (2 x 10(-7) M), was maximally enhanced by 48 h, and was maintained for the subsequent 7 days of continuous exposure to the steroid. With removal of hydrocortisone, PTH receptor binding promptly returned toward control levels. The increase in PTH binding was attributed to an increase in the availability of receptor binding sites, not to altered receptor binding affinity, and was blocked by cycloheximide. PTH-stimulated adenylate cyclase was also enhanced by glucocorticoids, and a close correlation was observed between PTH binding and PTH-stimulated adenylate cyclase. However, hydrocortisone not only increased PTH binding but also enhanced the efficiency of postreceptor signaling: 5'-guanylimidodiphosphate [Gpp(NH)p]- and forskolin-stimulated adenylate cyclase activities were also increased. Thus, enhanced PTH stimulation of adenylate cyclase by glucocorticoids resulted from at least two effects--increased receptor availability and enhanced postreceptor efficiency of transmembranous signaling.
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PMID:Glucocorticoids increase parathyroid hormone receptors in rat osteoblastic osteosarcoma cells (ROS 17/2). 285 94

PTH-like protein-(1-74) [PTHLP-(1-74)] was synthesized and purified. On the basis of chromatographic criteria and amino acid composition of the full-length peptide, direct amino acid sequencing of the N-terminus, and amino acid composition and internal sequence of proteolytic fragments of PTHLP-(1-74), the synthetic peptide appears to be of high quality and purity. Physiological comparison of PTHLP-(1-74) to [Tyr36]-PTHLP-(1-36) amide and bovine (b) PTH-(1-34) indicates that all three peptides are of equivalent potency in the fetal rat long bone and rat osteosarcoma 17/2.8 adenylate cyclase assays. However, as in earlier studies with native and N-terminal PTHLPs, PTHLP-(1-74) is considerably less potent (2%) in stimulating the canine renal cortical adenylate cyclase assay than is bPTH-(1-34). Further, PTHLP-(1-74) displayed only 12% of the activity of bPTH-(1-34) in inducing hypercalcemia when infused into rats in vivo. These studies support the possibility that subclasses of PTH receptors or varying PTH- and PTHLP-signalling transduction mechanisms may exist. In addition, they emphasize the need to precisely define the naturally occurring secretory and circulating species of this novel class of peptide hormones.
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PMID:Synthetic parathyroid hormone-like protein-(1-74): biochemical and physiological characterization. 291 92

Most studies of PTH receptor binding have been carried out with amino-terminal radioligands which only detect binding within that region of the hormone molecule. We studied the binding of electrolytically labeled intact bovine PTH [bPTH-(1-84)], and its amino-terminal fragment, bPTH-(1-34) to intact cloned rat osteosarcoma cells (ROS 17/2.8). We also measured the effects of these hormones on cell cAMP accumulation. Binding equilibrium for the two radioligands was reached by 2 h of incubation at 22 C. However, the cells had higher binding capacity (8-9% or 0.22-0.25 fmol/2 X 10(6) cells) for [125I]bPTH-(1-84) than for [125I]bPTH-(1-34) (4% or 0.11 fmol/2 X 10(6) cells). On the other hand [125I]bPTH-(1-34) bound to ROS cells with higher affinity [dissociation constant (Kd) = 19 nM] than did [125I]bPTH-(1-84) (Kd = 210 nM). Measurements of trichloroacetic acid precipitability and analysis of rebinding of previously incubated radioligand to fresh cells ruled out degradation of the tracer as an explanation for these differences. The maximum cell cAMP response to bPTH-(1-34) (Vmax = 780 +/- 32 pmol/2 X 10(6) cells X 5 min) was reached at 10(-7) M concentration with an affinity [Michaelis-Menten constant (Km)] of 3 nM. On the other hand, the Vmax with intact bPTH-(1-84) was lower (400 +/- 7 pmol/2 X 10(6) cells X 5 min), with a Km of 60 nM). Further studies with the bPTH-(1-84) tracer showed inability of hormonal fragments to compete completely for binding. At a concentration of 3 microM, bPTH-(1-84) reduced tracer binding by 82.5%, compared to 18% by bPTH-(1-34) and 10% by (Nle8,Nle18,Tyr34)bPTH-(1-34)amide, 60% by human PTH (hPTH)-(53-84), and 70% by the combination of bPTH-(1-34) and hPTH-(53-84). hPTH-(53-84) itself did not elicit a cAMP response after 5 min or 1 h of incubation nor did it significantly alter the cAMP response of the cells to bPTH-(1-84). These studies suggest that PTH binds to ROS 17/2.8 cells by sites carboxy-terminal (C-terminal) to position 34, in addition to sites within the amino-terminal portion of the hormone molecule; 72% of the binding of intact hormone to these cells was to the C-terminal 35-84 region of the PTH molecule. The significance of the C-terminal binding sites is presently unclear, but they do not appear to be coupled to adenylate cyclase. Further work is needed to determine the effects of C-terminal PTH fragments on bone cell metabolism.
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PMID:Binding of intact parathyroid hormone to rat osteosarcoma cells: major contribution of binding sites for the carboxyl-terminal region of the hormone. 299 16

Human renal carcinoma cell line 786-0 elaborates a protein that is structurally and immunochemically distinct from parathyroid hormone (PTH) and that activates renal cortical adenylate cyclase via an interaction with the PTH receptor. Because of the high frequency of excessive bone resorption and resultant hypercalcemia in patients with malignant disease we evaluated the ability of this 786-0 cell factor to reproduce PTH action in bone-derived cells. The 786-0 factor as well as bovine PTH (BPTH) (1-34) and prostaglandin E1 produced marked increases in cyclic adenosine 3':5'-monophosphate (cAMP) accumulation in the clonal rat osteosarcoma cell line UMR-106. A competitive antagonist of PTH action, [norleucine8, norleucine18, tyrosine34] BPTH(3-34)amide, blocked the cAMP stimulation produced by 786-0 factor and BPTH(1-34) but not that produced by prostaglandin E1. In the presence of forskolin (0.1 microM) UMR-106 cells were extremely sensitive to 786-0 factor, showing significant increases in cAMP production at a concentration 10-fold less than that required to activate adenylate cyclase in renal membranes. In contrast UMR-106 cells were less sensitive to BPTH(1-34) than were renal membranes. This preferential increase in sensitivity to 786-0 factor was not seen in membranes prepared from UMR-106 cells suggesting the importance of cytosolic components. Six additional human genitourinary carcinoma cell lines were found to produce factors that increased cAMP levels in UMR-106 cells. We conclude that 786-0 factor is a potent activator of the PTH receptor-adenylate cyclase system in these bone-derived cells. These findings are consistent with the view that cancer-associated hypercalcemia may frequently be attributable to tumor secretion of proteins (such as 786-0 factor) that are distinct from PTH but are capable of activating skeletal PTH receptors.
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PMID:Activation of the parathyroid hormone receptor-adenylate cyclase system in osteosarcoma cells by a human renal carcinoma factor. 299 59


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