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)

1. Parathyroid hormone-induced down-regulation was studied in the osteosarcoma cell line UMR-106. 2. A maximal priming does of bPTH (1-84) down-regulated PTH-responsiveness to 40% of its initial value; bPTH (1-41) was less effective than bPTH (1-84), whereas bPTH (42-84) had no effect, alone or in combination with bPTH (1-41). 3. A tentative model for the function of different domains of parathyroid hormone in down-regulation is suggested.
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PMID:Down-regulation of adenylate cyclase-coupled response to native bovine parathyroid hormone and fragments in the osteoblast-like cell line UMR-106. 155 56

We have investigated mechanisms of PTH-induced homologous desensitization reflected in the refractoriness of cAMP response to the second exposure to PTH in the clonal rat osteosarcoma cell line, UMR-106. Preincubation with 10(-7) M rat (r) PTH-(1-34) for 6 h caused the desensitization, resulting in a 65% decrease in cAMP accumulation in response to further exposure to rPTH. This desensitization was apparent at 10(-10) M rPTH and maximal at 10(-7) M rPTH. UMR-106 cells treated with protein kinase C (PK-C) activating phorbol ester, phorbol 12-myristate 13-acetate (PMA, 10(-6) M) for 6 h also induced desensitization manifested by a loss of rPTH-stimulated cAMP accumulation to 50% of that in the control cells. On the other hand, 4 alpha-phorbol 12,13-didecanoate, incapable of activating PK-C, failed to induce desensitization. Fifty micromolar H-7 (PK-C inhibitor) significantly blocked both rPTH- and PMA-induced desensitization. Thus, PK-C seemed to play a major role in rPTH-induced desensitization. Pretreatment with neither rPTH nor PMA changed the cAMP responsiveness to 10 micrograms/ml cholera toxin or 100 microM forskolin. Islet activating protein failed to influence the desensitization in this cell line. PTH receptor binding, assessed by using 125I-labeled [Nle8,Nle18,Tyr34]PTH-(1-34) as a radioligand, was decreased along with PTH receptor numbers by pretreatment with rPTH or PMA. These data indicate that rPTH-induced homologous desensitization occurs at least in part through the activation of PK-C and that PK-C directly affects PTH receptor in UMR-106 cells.
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PMID:Protein kinase C is involved in PTH-induced homologous desensitization by directly affecting PTH receptor in the osteoblastic osteosarcoma cells. 164 55

PTH activates multiple second messengers in its target cells, but the level at which the hormonal signal splits into different pathways is still unknown. To achieve insights on this issue, we have studied the structure-function relationship of PTH by analyzing the effects of bovine PTH-(1-34) [bPTH-(1-34)] and PTH fragments truncated at the N-terminus on the intracellular calcium concentration [( Ca2+]i) and cAMP production in the rat osteogenic sarcoma cell line UMR 106-01. [Ca2+]i was measured in single cells using fura-2. When exposed to 10(-7) M bPTH-(1-34), 20% of the cells responded with a transient increase in [Ca2+]i of variable amplitude. Equimolar doses of bPTH-(2-34), propionyl bPTH-(2-34) [(pbPTH-(2-34)], and bPTH-(3-34) also transiently increased [Ca2+]i, whereas both [tyrosine34]bPTH-(7-34) amide [bPTH-(7-34)] and bPTH-(30-34) were ineffective. The amplitude of the [Ca2+] i transients was dose-dependent, with threshold concentrations of 10(-10) M for bPTH-(1-34) and bPTH-(2-34), and 10(-9) M for bPTH-(3-34). The response rate to the active peptides ranged between 10-30%, without a clear dose-relatedness. A second addition of 10(-7) M bPTH-(1-34) to cells prestimulated with equimolar doses of bPTH-(2-34), pbPTH-(2-34), or bPTH-(3-34) produced another transient, whereas after exposure to 10(-7) M bPTH-(1-34), the cells were completely desensitized to a second homologous stimulation, suggesting that the binding affinity of the truncated peptides for the PTH receptor is lower than that of the intact bPTH-(1-34) fragment. In addition, both bPTH-(1-34) and bPTH-(2-34) dose-dependently stimulated cAMP production, but the former was more potent (ED50 = 10(-9) vs. 10(-7) M, respectively). On the contrary, pbPTH-(2-34), bPTH-(3-34), and bPTH-(7-34) had no effect on cAMP. Pretreating the cells with pertussis toxin to enhance cAMP responses via inhibition of Gi potentiated the effect of bPTH-(1-34) and bPTH-(2-34) and disclosed weak but detectable agonist action of pbPTH-(2-34). These results indicate that specific domains of the PTH molecule are linked to activation of different second messenger pathways; while the first two amino acids are indispensable for activating the cAMP system, generation of the [Ca2+]i signal appears to involve a longer domain, including the amino acid residue in position 3.
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PMID:Dissociation of second messenger activation by parathyroid hormone fragments in osteosarcoma cells. 164 59

Effects of increase in intracellular calcium on PTH-induced homologous desensitization were investigated using calcium ionophores. Pretreatment of UMR-106 cells (rat osteoblast like osteosarcoma cell line) with calcium ionophores (A23187 or ionomycin) for 6h resulted in approximately 50% decrease of PTH-stimulated cAMP production. PTH receptor binding, assessed with 125I-[Nle8,Nle18,Tyr34]PTH-(1-34) as radioligand, was significantly decreased in 10(-6) M calcium ionophore-pretreated (for 6h) cells without affecting the dissociation constant (Kd) for PTH. Minimal effective treatment period was 2h and similar inhibitory effect was observed in 12h-treated cells. These data suggest that increase in intracellular calcium might also act on PTH receptor in the similar manner as protein kinase C activation to induce desensitization.
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PMID:Role of increase in intracellular calcium in PTH-induced homologous desensitization in UMR-106 cells. 164 35

The human-derived procalcitonin amino-terminal cleavage peptide, N-proCT has previously been shown to act mitogenically on isolated chicken and human osteoblast-like cells and on the human osteosarcoma cell line U-2 OS. We have examined the effect of N-proCT on growth and phenotype of cloned rat osteoblastic and preosteoblastic cells. Neither cell growth nor the phenotype (ALP, PTH response) of either cell type was significantly changed by the procalcitonin cleavage peptide.
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PMID:The procalcitonin amino-terminal cleavage peptide (N-proCT) lacks biological activity on normal clonal rat osteoblastic and preosteoblastic cells in vitro. 165 76

The protein kinase C-(PKC) activating phorbol esters 12-O-tetradecanoylphorbol-13-acetate (TPA; 100 nmol/l) and phorbol 12,13-dibutyrate (PDBU; 100 nmol/l) enhanced basal cyclin AMP accumulation in cultured neonatal mouse calvaria. The cyclic AMP response to parathyroid hormone (PTH; 10 nmol/l) and the adenylate cyclase activators forskolin (1-3 mumol/l) and choleratoxin (0.1 mumg/ml) was potentiated in a more than additive manner by TPA and PDBU. In contrast, phorbol 13-monoacetate (phorb-13; 100 nmol/l), a related compound but inactive on PKC, had no effect on basal or stimulated cyclic AMP accumulation. In the presence of indomethacin (1 mumol/l), TPA and PDBU had no effect on cyclic AMP accumulation in calvarial bones per se, but were still able to cause a significant enhancement of the response to PTH, forskolin and choleratoxin. PTH-, forskolin- and choleratoxin-stimulated cyclic AMP accumulation in rat osteosarcoma cells UMR 106-01 was synergistically potentiated by TPA and PDBU, but not by phorb.-13. These data indicate that PKC enhances cyclic AMP formation and that the level of interaction may be at, or distal to, adenylate cyclase.
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PMID:Protein kinase C activating phorbolesters enhance the cyclic AMP response to parathyroid hormone, forskolin and choleratoxin in mouse calvarial bones and rat osteosarcoma cells. 166 87

In this study we report the preparation of a human osteosarcoma cell cDNA library and describe the isolation and sequence determination of a clone encoding the complete sequence of a novel human insulin-like growth factor (IGF)-binding protein (hIGFBP-4). Previous work indicated that hIGFBP-4 is the predominant IGFBP expressed by human osteoblast-like cells, and that IGFBP-4 binds and inhibits the mitogenic activities of IGF-I and IGF-II. Sequence determination revealed that hIGFBP-4 is a unique gene product with significant amino- and carboxy-terminal sequence similarity to three other known IGFBPs. Identical alignment of 18 cysteines in IGFBP-4 and the three other IGFBPs is a key structural feature of this protein family. In vitro studies of human osteoblast-like cells suggest that PTH regulates the expression of hIGFBP-4 and that the PTH effect is mediated through a cAMP mechanism. hIGFBP-4 mRNA was also expressed in skin fibroblasts, and thus, this inhibitory IGFBP could be an important physiological regulator of IGF actions in bone cells and other cell types as well.
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PMID:Inhibitory insulin-like growth factor-binding protein: cloning, complete sequence, and physiological regulation. 170 25

Interleukin 6 (IL-6) probably plays a central role in the acute phase response and in haemopoiesis and may be involved in the control of bone turnover. We have studied the release of IL-6 from human trabecular bone cells treated with a variety of stimuli using a specific bioassay. In serum free medium, unstimulated human osteoblast-like cells produced IL-6 in the range of 1000-2050 pg/ml/24 h. Recombinant human interleukin 1 (IL-1 alpha) (10(-13)-10(-11) M), tumor necrosis factor alpha (TNF alpha) (10(-9)-10(-7) M) and lipopolysaccharide (5-500 ng/ml) all stimulated release of IL-6 from human bone cells. Maximal levels of 17,000 pg/ml were observed using the highest concentration of IL-1. 1,25(OH)2D3 and PTH did not stimulate IL-6 release. Using a specific sheep antihuman IL-6 antibody, all IL-6 activity could be neutralized. In parallel studies, ROS 17/2.8 rat osteosarcoma cells released around 50 pg/ml of IL-6 under basal conditions which were increased to a maximum of 900 pg/ml by treatment with PTH (10(-9) M). The cytokines were less effective and 1,25(OH)2D3 again had no effect. Modulation of expression of IL-6 mRNA in human osteoblast cells was examined using a human complementary deoxyribonucleic acid probe. The mRNA was constitutively expressed, and IL-1 (10(-11) M) and TNF (10(-7) M) induced further mRNA expression within 2 h, which was sustained over 24 h. 1,25(OH)2D3 (10(-7) M), IL-6 (2000 pg/ml), and PTH (10(-9) M) exerted no effects at any time point. Dexamethasone (10(-6) M) suppressed both basal and IL-1- and TNF-induced IL-6 mRNA expression. IL-6 receptor mRNA was constitutively expressed but was not regulated by any of the above agents. It is clear that rodent and human osteoblasts differ in their production of IL-6 and its modulation. These data support the hypothesis that IL-6 is produced locally in human bone by osteoblasts under the direction of other cytokines. This could have implications in bone remodeling, haemopoiesis, and systemic responses to local injury.
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PMID:The modulation of the expression of IL-6 and its receptor in human osteoblasts in vitro. 171 33

Recent evidence indicates that after PTh interaction with its receptor, both protein kinase-A (PKA) and protein kinase-C (PKC) are activated. To investigate the relationship between PTH structure and protein kinase stimulation, we have analyzed the effects of synthetic PTH fragments on PKA and PKC in the rat osteogenic sarcoma cells, UMR 106-01. Activation of PKA by 10(-7) M bovine (b) PTH-(1-34) was maximal (2.7-fold of control) at 5 min and remained elevated 15 min after hormone exposure. bPTH-(2-34), at equimolar doses, also stimulated PKA, but with a lower potency (1.4-fold of control), whereas propionyl bPTH-(2-34) [pbPTH-(2-34)], bPTH-(3-34), [Tyr34]bPTH-(7-34) amide [bPTH-(7-34)], and bPTH-(30-34) were ineffective. On the other hand, translocation of PKC activity from the cytosol to the membrane after exposure to bPTH-(1-34) was transient, with a peak at 1 min (1.9-fold of control), and returned to basal levels after 5 min. Other fragments, bPTH-(2-34), pbPTH-(2-34), bPTH-(3-34), and bPTH-(7-34), were also active on PKC, with relative potencies of 81%, 67%, 62%, and 51% of bPTH-(1-34), respectively, whereas bPTH-(30-34) was inactive. bPTH-(1-34), bPTH-(2-34), pbPTH-(2-34), and bPTH-(3-34) also induced inositol 1,4,5-trisphosphate production, with a potency order of 1.6-, 1.6-, 1.5-, and 1.6-fold over the control value, respectively, thus indicating activation of phospholipase-C. Neither bPTH-(7-34) nor bPTH-(30-34) caused a statistically significant increase in inositol 1,4,5-trisphosphate production. These results demonstrate that PTH signal transduction through the two different pathways can be dissociated; while activation of the cAMP/PKA system requires amino acids 1 and 2, the phospholipase-C/PKC system is coupled to a longer domain of the hormone's N-terminus.
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PMID:Structure-function relationship of parathyroid hormone: activation of phospholipase-C, protein kinase-A and -C in osteosarcoma cells. 172 5

The PTH activates both adenylate cyclase and a mechanism that increases membrane-associated protein kinase-C (PKC) activity. To define the hormone's PKC activation domain we have used a panel of PTH fragments and ROS 17/2 rat osteosarcoma cells as the target cells. PTH equally and maximally increased PKC activity in ROS 17/2 cell membranes at physiological concentrations between 1-50 pM and 5-50 nM, but not at intermediate concentrations or concentrations above 50 nM. The PKC-stimulating picomolar concentrations of PTH did not stimulate adenylate cyclase in ROS 17/2 cells, while the PKC-stimulating nanomolar concentrations of the hormone did stimulate adenylate cyclase, with an EC50 of 1-2 nM. Very high concentrations of PTH, such as 100 nM, that did not increase membrane PKC activity were still able to maximally stimulate adenylate cyclase. PTH fragments lacking the N-terminal amino acids needed for adenylate cyclase activation increased membrane PKC activity, and the PKC activation domain was found to lie within the 28-34 region of the PTH molecule. This was confirmed by showing that optimally effective picomolar concentrations of the human PTH-(28-34) fragment itself were able to increase membrane-associated PKC activity to the same extent as the optimally effective picomolar concentrations of the intact PTH-(1-84) or the larger PTH-(1-34) or PTH-(3-34) fragments.
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PMID:The protein kinase-C activation domain of the parathyroid hormone. 172 20


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