Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Structural requirements for binding to the bone calcitonin (CT) receptor and for CT bioactivity both in vitro and in vivo were assessed for a series of N-terminally truncated, N alpha-acetylated, fragments of salmon calcitonin (sCT). Sequential deletion of amino acid residues from the amino-terminus of [Ala7]sCT-(2-32) peptide amide first led to partial agonists and, upon deletion of residues 1 to 7, to a high affinity antagonist, N alpha-acetyl-sCT-(8-32)-NH2. The presence of two separate domains within the sCT sequence is proposed: (I) a binding domain comprising residues 9-32 and (II) an activation domain requiring residues 3 to 6. N alpha-acetyl-sCT-(8-32)-NH2, in several bioassays including plasminogen activator release from LLC-PK1 cells (pA2 = 7.31), cAMP production in UMR-106-06 cells (pA2 = 7.81) and in the fetal rat long bone resorption assay showed potent antagonistic properties.
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PMID:N-terminal truncation of salmon calcitonin leads to calcitonin antagonists. Structure activity relationship of N-terminally truncated salmon calcitonin fragments in vitro and in vivo. 132 97

Parathyroid hormone (PTH) and PTH-related protein (PTHrP) act via PTH receptors in bone to stimulate bone resorption. Bone resorption is also stimulated by certain cytokines, which are produced in bone and bone marrow. The effects of such cytokines on the PTH-receptor system were studied in the osteoblast-like osteosarcoma cell line UMR 106-06. 125I-labelled PTHrP-(1-84)-peptide bound specifically to the cells, and PTHrP-(1-34) and -(1-84) competed with equimolar affinity for binding to UMR 106-06 cells. The specific binding of 125I-PTHrP-(1-84) could be completely blocked by PTH. Therefore 125I-PTHrP-(1-84) bound to a classical receptor in UMR 106-06 cells. Preincubation for 3 days with either tumour necrosis factor alpha (TNF alpha) or retinoic acid (RA) both decreased the specific binding of 125I-PTHrP-(1-84) to about 40% of control levels. These effects were specific for PTH binding, since there was little effect on 125I-salmon-calcitonin binding. Both TNF alpha and RA required 24 h exposure to cells to produce a measurable effect. The decrease in 125I-PTHrP-(1-84) binding was due to a reduced number of binding sites, with little apparent change in affinity. Half-maximal effects were seen with 1 ng of TNF alpha/ml, whereas 1 microM-RA was needed to observe the loss of PTH receptors. Combinations of RA and TNF alpha produced a greater effect than that of either agonist alone. The loss of PTH receptors was accompanied by a specific loss of PTH-stimulated cyclic AMP production. Preincubation with TNF alpha increased the basal plasminogen activator (PA) activity in the cells and decreased the amplitude of the response of PA activity to PTH compared with control cells. Furthermore TNF alpha decreased sensitivity to PTH (50% stimulation of PA activity with 0.1 nM-PTH in control cells versus 50% stimulation with 0.3 nM-PTH in TNF alpha-treated cells). In contrast, TNF alpha pretreatment increased the amplitude of the response of PA activity to calcitonin, whereas sensitivity to calcitonin was not altered. These data are consistent with a specific down-regulation of PTH receptors in osteoblast-like UMR 106-06 cells after exposure to TNF alpha or RA. The loss of PTH receptors is accompanied by a decreased responsiveness to PTH, as measured with the PA system in these cells. A loss of PTH receptors could modulate PTH responses in osteoblasts, either in the local control of bone formation and resorption, or in pathological conditions such as humoral hypercalcaemia of malignancy.
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PMID:Specific down-regulation of parathyroid hormone (PTH) receptors and responses to PTH by tumour necrosis factor alpha and retinoic acid in UMR 106-06 osteoblast-like osteosarcoma cells. 166 Jul 13

The identification of the plasminogen activator (PA) types present in bone and the regulation of their activity by parathyroid hormone (PTH) were investigated in cultures of fetal mouse calvariae with the use of either a chromogenic substrate or a zymographic assay. PA was detected essentially in the tissue extracts of the explanted bones, with only 1-2% of the total activity released in the surrounding culture media. From their electrophoretic behavior compared to PAs of other mouse tissues and from their response to a specific antibody raised against the tissue type PA (tPA), two major molecular species, of 70 and 48 kD were identified as tPA and urokinase (uPA), respectively, a third minor species of 105 kD being likely to correspond to complexes between tPA and an inhibitor; the culture fluids, moreover, contained enzymatically active degradation products of uPA of 42 and 29 kD. The PA activity of the bone extracts was only minimally affected by the addition of fibrinogen fragments to the chromogenic assays. PTH induced bone resorption and stimulated in parallel the accumulation of PA in the tissue; other bone-resorbing agents, 1,25-dihydroxyvitamin D3 and prostaglandin E2, had similar effects. Densitometric scanning of the zymograms of the bone extracts indicated that PTH stimulated only the production of tPA and had no effect on that of uPA. However, PTH also enhanced the release of uPA (both the 48 kD and the 29 kD forms) from the bones into the media. Although inhibiting bone resorption, calcitonin had no effect on the PTH-induced accumulation of PA in bone or on the release of tPA, but it prevented the PTH-induced accumulation of 29 kD uPA in the culture fluids. Thus these studies support the view that tPA and possibly also uPA may have a role in the physiology of bone; the nature of this role remains to be elucidated, however.
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PMID:Tissue and urokinase plasminogen activators in bone tissue and their regulation by parathyroid hormone. 179 56

Calcitonin-induced changes in gene expression at the level of protein synthesis were examined in cultured porcine kidney cells (LLC-PK1) using two-dimensional gel electrophoresis of [35S]methionine-labeled polypeptides. Twelve intracellular polypeptides showed reproducible changes in the relative intensity of labeling. From that set of polypeptides ten showed an increase and two a decrease in the labeling intensity after calcitonin treatment. One of the induced polypeptides was identified as plasminogen activator and two others were shown to be related to cytokeratins. The labeling of two induced and well-separated polypeptides of 70K and 95K Mr was quantitated and correlated with an increase in secretion of plasminogen activator.
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PMID:Hormonal regulation of protein synthesis in cultured kidney cells. 240 39

Calcitonin and calcitonin gene-related peptide stimulate adenylate cyclase activity and plasminogen activator production in cultured renal tubular LLC-PK1 cells. Salmon [125I]calcitonin and human [125I]calcitonin gene-related peptide bound specifically to the cells. Salmon [125I]calcitonin binding was reduced at lower concentrations of non-radioactive salmon calcitonin than of human calcitonin gene-related peptide. For the stimulation of adenylate cyclase activity and plasminogen activator production, the potency of salmon calcitonin was higher than that of human calcitonin and calcitonin gene-related peptide. In a subclone of LLC-PK cells lacking salmon calcitonin binding sites, no specific binding of [125I]CGRP occurred, and adenylate cyclase activity and plasminogen activator production was not increased by the peptides. Thus, in LLC-PK1 cells the stimulation of adenylate cyclase activity and plasminogen activator production by calcitonin gene-related peptide is probably mediated by the calcitonin receptor.
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PMID:Calcitonin and calcitonin gene-related peptide interact with the same receptor in cultured LLC-PK1 kidney cells. 299 13

The plasminogen activator (PA) in clonal osteogenic sarcoma cells of rat origin (UMR 106-01 and UMR 106-06) and in osteoblast-rich rat calvarial cells has been characterized using specific antibodies to be tissue-type PA (tPA). An Mr value of 75,000 by SDS-polyacrylamide gel electrophoresis and fibrin autoradiography supports this characterization. There was also evidence for an Mr 105,000 component, which could be due to a proteinase-inhibitor complex. The mechanism of regulation of this tPA activity has been studied in the clonal osteogenic sarcoma cells. Parathyroid hormone (PTH) and prostaglandin E2, which increase cyclic AMP production in the sarcoma cells, also increased tPA activity. The sensitivity and magnitude of the tPA response to PTH and prostaglandin E2 were increased by simultaneous treatment with isobutylmethylxanthine (IBMX) at drug concentrations which had little effect themselves on tPA activity. In UMR 106-06 cells, which unlike UMR 106-01 cells show a cyclic AMP response to calcitonin, tPA activity was also increased in response to calcitonin, and the effect was enhanced by IBMX. 1,25-Dihydroxyvitamin D-3 also increased tPA activity in the cells, but this response was not modified by IBMX. Synthetic peptide antagonists of PTH-responsive adenylate cyclase, [34Tyr]-hPTH (3-34) amide and [34Tyr]-hPTH (5-34) amide, inhibited the PTH-induced increase in tPA activity over the same concentration range at which they inhibited cyclic AMP production, but the antagonist peptides had no effect on the tPA responses to prostaglandin E2, calcitonin or 1,25-dihydroxyvitamin D-3. These data indicate that cyclic AMP mediates the actions of PTH, prostaglandin E2 and calcitonin in increasing tPA activity in the clonal osteogenic sarcoma cells. 1,25-Dihydroxyvitamin D-3, on the other hand, increases tPA activity through a mechanism independent of cyclic AMP.
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PMID:Cyclic AMP-dependent and -independent effects on tissue-type plasminogen activator activity in osteogenic sarcoma cells; evidence from phosphodiesterase inhibition and parathyroid hormone antagonists. 301 47

The LLC-PK1 pig kidney-derived cell line is morphologically and functionally heterogeneous. We have clonally derived three sublines that differ in their response to calcitonin and in their ability to form domes. The three clones were analyzed for their basal and hormonally induced plasminogen activator production. In contrast to the D + Sc clone, in which calcitonin induced a greater than 100-fold increase in plasminogen activator synthesis, the D + Rc clone did not respond to the hormone; this was related to a deficiency of the cells in calcitonin binding. Transepithelial electrical resistance measurements revealed a direct correlation with the capacity of the cells to form domes; in one of the isolated clones (D-), the lack of dome formation coincided with a low electrical resistance; the D + Sc clone, in which all single cell-derived colonies formed domes, showed a higher electrical resistance than that developed by the original cell line. Thus the LLC-PK1 clones provide a useful in vitro model for the study of epithelial properties.
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PMID:LLC-PK1 cells: cloning of phenotypically stable subpopulations. 370 17

The peptide hormone, calcitonin, induces urokinase-type plasminogen activator (uPA) enzyme activity in cultured LLC-PK1 pig kidney cells. This induction occurs as a consequence of transcriptional activation of the uPA gene. Treatment with the synthetic glucocorticoid hormone, dexamethasone, was found to inhibit calcitonin induction of uPA enzyme activity by as much as 80%. The inhibitory effect of dexamethasone was attributed to at least two mechanisms: induction of an inhibitor of uPA enzyme activity, and reduction in uPA mRNA levels. Study on reduction of uPA mRNA levels showed that dexamethasone significantly reduced the transcription rate of the calcitonin-induced uPA gene, without affecting the half-life of uPA mRNA. Although dexamethasone has been reported to induce inhibitors of plasminogen activator enzyme activity and to inhibit transcription of various genes, the system described here appears novel in that both actions are coordinated.
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PMID:Dexamethasone coordinately inhibits plasminogen activator gene expression and enzyme activity in porcine kidney cells. 382 25

Plasminogen activators are highly selective proteases that activate the proenzyme plasminogen to the general protease, plasmin. We studied a porcine kidney cell line, originally isolated as a high producer of plasminogen activator, in which activities of cellular adenylate cyclase and cAMP-dependent protein kinase are increased in response to calcitonin. We found that salmon calcitonin, in the concentration range 0.03-300 nM, increased plasminogen activator production up to approximately 1,000-fold and concurrently inhibited cell multiplication; both of these effects were reversible. Human calcitonin was approximately 0.01 times as potent as salmon calcitonin, corresponding to potency differences observed in other biological systems. Plasminogen activator production was also stimulated by other agents that raise cellular cAMP levels such as cholera toxin, phosphodiesterase inhibitors, and vasopressin, but not to the same extent as by calcitonins. The rapidity and sensitivity of the plasminogen activator determination and other cellular responses may make it possible in the future to use this cell stain in a convenient bioassay for calcitonins and their analogues.
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PMID:Calcitonin stimulates plasminogen activator in porcine renal tubular cells: LLC-PK1. 627 91

The plasminogen activator secreted by calcitonin-treated pig kidney cells was purified, characterized and compared with human urinary urokinase. The purification procedure was based on the following steps: sulphopropyl-Sephadex chromatography, p-aminobenzamidine-Sepharose chromatography, preparative sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectrofocusing. The purified enzyme was obtained from the conditioned medium with a yield of 13% and a purification factor of 390-fold. Analysis by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis under non-reducing conditions showed one closely spaced doublet with an Mr of 50 000; in the presence of reducing agents, two additional bands of Mr 30 000 and 20 000 appeared. The purified enzyme resembles the 53 000-Mr components of human urinary urokinase in amino acid composition and two-dimensional tryptic peptide maps and in its catalytic properties, and the two enzymes cross-react immunologically with rabbit antibodies raised against either. The enzyme appears to be different from tissue plasminogen activator secreted by HeLa cells.
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PMID:Purification and characterization of a plasminogen activator secreted by a pig kidney cell line. 643 Feb 76


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