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:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined receptor binding and metabolic effects of the platelet-derived growth factor (PDGF) isoforms AA, AB, and BB in cultures of osteoblastic cells from fetal rat calvaria. Saturation binding experiments demonstrated the presence of 6,000 binding sites for PDGF-AA, 42,000 for PDGF-AB, and 60,000 for PDGF-BB. Binding competition experiments were compatible with the recently postulated model of three PDGF receptor subtypes with differential affinity for the PDGF isoforms. The effects of the PDGF isoforms on DNA synthesis, collagen synthesis, and alkaline phosphatase activity in osteoblasts strictly correlated with the number of available binding sites. Accordingly, PDGF-BB was the most potent isoform, PDGF-AB was slightly less potent, and PDGF-AA was the least potent. In contrast, we found that PDGF-BB was less potent than PDGF-AB in increasing plasminogen activator activity in the osteoblast-conditioned medium. Our data strongly suggest that the PDGF receptor subtypes in fetal rat osteoblasts not only selectively bind one or more PDGF isoforms, but are also capable of responding differently to these isoforms.
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PMID:Differential effects of platelet-derived growth factor isoforms on plasminogen activator activity in fetal rat osteoblasts due to isoform-specific receptor functions. 131 39

We tested the chemotactic response to platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF beta) of cells released enzymatically from fetal rat calvaria (RC). Both factors were chemotactic for RC cells, but the magnitude of the chemotactic response differed markedly between different populations and varied with time in culture of the cell populations. Cells released earlier from the calvaria showed a greater response than osteoblast-enriched populations released later. The optimal concentration of PDGF was the same for both alkaline phosphatase (AP)-positive and AP-negative cells within the populations. However AP-positive cells showed two peaks of response to TGF beta; one peak coincided with the TGF beta concentration also maximally affecting AP-negative cells, while the other occurred at a concentration 50-100 times higher. The results indicate that PDGF and TGF beta are chemotactic for both AP-positive and AP-negative cells in populations of cells derived from fetal calvariae, that chemotactic response declined with longer periods of time in culture, and that AP-positive osteoblast-like cells respond to a concentration of TGF beta that does not affect the AP-negative cells in the population.
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PMID:Differential chemotactic responses of different populations of fetal rat calvaria cells to platelet-derived growth factor and transforming growth factor beta. 142 6

We report herein the presence of a 56 kd platelet derived growth factor (PDGF)-related protein as a phosphorylated form in human glioma cells. The phosphorylation of the 56 kd form was found to be the longest of all PDGF-related proteins. By Western blotting using a monoclonal anti-PDGF B-chain, the 80 kd, 56 kd, 40 kd, 28 kd and 17 kd PDGF-related proteins were detected, while after treatment among the nitrocellulose membrane transblotted cell extracts with alkaline phosphatase, 40 kd was the most densely observed while the 56 kd and 80 kd PDGF-related proteins were also detected. In a 32P flush labeling study, it was revealed that PDGF-related proteins incorporated with 32P were detected at 28, 32, 35, 40, 56 and 80 kd but the 17 kd monomer was not labeled. Among the labeled PDGF-related proteins, the 56 kd PDGF-related protein alone remained intracellularly for at least 16 hours. These results indicated that the PDGF-related proteins in human glioma cells are synthesized in a phosphorylated form and partly remain in a 56 kd phosphorylated form intracellularly. The 56 kd form may thus be the most stable form and likely has a substantial biological effect.
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PMID:The 56 kd platelet-derived growth factor (PDGF)-related protein is phosphorylated and the most stable form in human glioma cells. 143 29

We used the technique of in situ hybridization to determine if cells expressing PDGF B-chain mRNA can be detected in a model of mesangial proliferative nephritis in the rat induced with antibody directed against the Thy 1 antigen present on the mesangial cell membrane. The method involved hybridization with a digoxigenin-labeled cRNA probe for the murine PDGF B-chain followed by detection with an anti-digoxigenin-alkaline phosphatase conjugate and subsequent colorimetric reaction. In normal rats (N = 4), the majority of glomeruli (74%) were negative for PDGF B-chain mRNA, whereas 65% of glomeruli from rats with mesangial proliferative nephritis (N = 4) had segmental or diffuse staining for PDGF B-chain mRNA in a mesangial pattern. The difference, as measured using a semiquantitative scale, was significant (mean scores 0.4 +/- 0.2 vs. 1.9 +/- 0.2; scale 0 to 3+; P less than 0.001). The increase in PDGF B-chain mRNA positive cells localized to areas of hypercellularity and was associated with a significant increase in cells positive for PDGF B-chain by immunostaining with a specific monoclonal antibody (0.8 +/- 0.1 vs. 1.7 +/- 0.4, scale 0 to 3+, normal vs. diseased rats, P less than 0.005). Complement depletion, which prevents the mesangial cell proliferation, also prevented the increase in cells expressing PDGF B-chain mRNA and protein. Thus, this method of in situ hybridization can successfully detect cells expressing PDGF mRNA in active glomerulonephritis, and may be useful for detecting cells expressing genes for other growth factors and cytokines in both human and experimental models of glomerular injury.
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PMID:Demonstration of PDGF B-chain mRNA in glomeruli in mesangial proliferative nephritis by in situ hybridization. 172 21

Two highly sensitive, nonradiolabeled assays for protein phosphotyrosine phosphatase (PTPase) have been developed. The first assay is based on the use of chemically synthesised phosphotyrosine-containing peptides that can be separated from the dephosphorylated peptide products by HPLC. In this assay, partially purified placental PTPase 1B dephosphorylated three dodecaphosphopeptides (corresponding to insulin receptor autophosphorylation sites at positions PY1146, PY1150, and PY1151) with approximately equal affinity (Km 1.3-2.5 microM), indicating that PTPase 1B shows no distinct preference for the site of dephosphorylation in these peptides. The second assay employs either a phosphopeptide or an autophosphorylated tyrosine kinase domain immobolized on microtiter plate wells. After reaction with PTPase, the remaining unconverted phosphosubstrate is detected in an ELISA using anti-phosphotyrosine antibodies. The latter assay was used to monitor PTPase activity during purification procedures and for characterizing PTPases. Modulation of PTPase activity by orthovanadate, heparin, Zn2+, and EDTA gave similar results in both assays. The immobilized autophosphorylated IR tyrosine kinase domain was a poor substrate for bovine liver alkaline phosphatase and seminal fluid acid phosphatase. The second assay also offers the potential for comparing PTPase activity toward several autophosphorylated tyrosine kinase domains, including those of the insulin, epidermal growth factor, and platelet-derived growth factor receptors.
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PMID:Two nonradioactive assays for phosphotyrosine phosphatases with activity toward the insulin receptor. 181 86

A 72-year-old male had complained of right back pain and bleeding from his tongue. He was admitted to our department on May 18, 1989. Physical examination revealed hepatosplenomegaly. Peripheral blood findings were as follows: RBC was 3.80 x 10(6)/microliters. Hb 12.2 g/dl, Ht 36.5%, platelet count 735 x 10(3)/microliters, WBC 22,100/microliters, leukoerythroblastosis present. Neutrophil alkaline phosphatase score was normal. Serum vitamin B12 and plasma platelet-derived growth factor level were elevated. Skeletal X-ray revealed multiple punched-out lesions at the 8th thoracic vertebra, and 6th and 8th ribs. Serum IgG level was 3,900 mg/dl. Serum immunoelectrophoresis revealed IgG lambda-type M-protein. Because he complained of severe cervical pain, and skeletal X-ray examination revealed the fracture of 6th cervical vertebra, the operation was performed to remove the lesion. Biopsy of cervical lesion revealed plasmacytoma. M-protein was decreased and the size of the tumor was reduced after treatment with VCAP (vincristine, cyclophosphamide, adriamycin, prednisolone) regimen and interferon-alpha for multiple myeloma.
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PMID:[IgG lambda-type multiple myeloma associated with myelofibrosis accompanied by thrombocytosis]. 194 35

We have prepared plasma membranes from Balb/c 3T3 fibroblasts to study the transmodulation of the high affinity epidermal growth factor (EGF) receptor. Although phorbol esters do not transmodulate the high affinity EGF receptors on these membranes, the addition of platelet-derived growth factor (PDGF) or EGF to the membranes leads to the loss of high affinity EGF binding and to the phosphorylation of several membrane proteins, including the EGF receptor. The EGF receptor is phosphorylated at tyrosine residues although we have not yet established if this represents direct phosphorylation by the PDGF receptor kinase or is mediated by activation of other cell membrane-associated tyrosine kinases. Upon treatment of the membranes with PDGF, four major phosphoproteins (of apparent molecular masses of 69, 56, 38, and 28 kDa) are released from the membrane and can be retrieved from the supernatant fluid using a reversed-phase cartridge. As assessed by immunoprecipitation with an anti-phosphotyrosine antibody, all four proteins appear to be phosphorylated on tyrosine. The time course of dissociation of these proteins from the membranes closely parallels the loss of high affinity EGF receptors. The high affinity EGF receptor can be reconstituted on PDGF-transmodulated membranes by treating the supernatant fluid with alkaline phosphatase and adding the mixture to the membranes. It appears that dephosphorylation of the released proteins is sufficient to allow reassociation with the membranes and formation of the high affinity EGF receptor complex.
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PMID:Reconstitution of the high affinity epidermal growth factor receptor on cell-free membranes after transmodulation by platelet-derived growth factor. 199 54

Platelet-derived growth factor (PDGF) exists as a homodimer or a heterodimer comprising either PDGF-A or PDGF-B subunits, and each isoform occurs in various tissues, including bone. Although the stimulatory effects of PDGF-BB have been studied in cultures of bone cells and intact bone fragments, the influence of other isoforms that may arise locally or systematically in vivo, has not been reported. Therefore recombinant human PDGF-BB, PDGF-AB, and PDGF-AA were evaluated in osteoblast-enriched cultures from fetal rat bone. Within 24 hours these factors produced a graded response in bone cell DNA and protein synthesis, with half-maximal effects at approximately 0.6, 2.1, and 4.8 nM PDGF-BB, PDGF-AB, and PDGF-AA, respectively. Increases in collagen and noncollagen protein synthesis were abrogated when DNA synthesis was blocked with hydroxyurea. Furthermore, each factor reduced alkaline phosphatase activity, PDGF-BB being the most inhibitory. Binding studies with 125I-PDGF-BB or 125I-PDGF-AA and each unlabeled PDGF isoform produced discrete ligand binding and displacement patterns: 125I-PDGF-BB binding was preferentially displaced by PDGF-BB (Ki approximately 0.7 nM), less by PDGF-AB (Ki approximately 2.3 nM) and poorly by PDGF-AA. In contrast, 125I-PDGF-AA binding was measurably reduced by PDGF-AA (Ki approximately 4.0 nM), but was more effectively displaced by PDGF-BB or PDGF-AB (each with Ki approximately 0.7 nM). These studies indicate that each PDGF isoform produces biochemical effects proportional to binding site occupancy and suggest that receptors that favor PDGF-B subunit binding preferentially mediate these results in osteoblast-enriched bone cell cultures.
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PMID:Relative binding and biochemical effects of heterodimeric and homodimeric isoforms of platelet-derived growth factor in osteoblast-enriched cultures from fetal rat bone. 206 62

The effect of leukemia inhibitory factor (LIF) on proliferation and phenotypic expression in murine osteoblast-like (MC3T3E1) cells was examined. LIF inhibited the proliferation of these cells by up to 20% and DNA synthesis was inhibited in a dose-dependent manner with an ED50 of about 0.2 ng/ml. The effect of LIF relative to matched controls increased with decreasing serum concentration, reaching 30% inhibition at 0.2% serum. LIF also reduced the stimulatory effects of platelet-derived growth factor and insulin-like growth factor I on DNA synthesis. The inhibition of the DNA synthesis by saturating concentration of transforming growth factor beta was further enhanced by the addition of LIF, suggesting independent pathways for the action of the two growth inhibitors. In addition, LIF reduced alkaline phosphatase activity and the abundance of type I collagen messenger RNA, but increased the level of osteopontin messenger RNA. These findings suggest that LIF may play a role in regulating the function of osteoblasts.
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PMID:Leukemia inhibitory factor suppresses proliferation, alkaline phosphatase activity, and type I collagen messenger ribonucleic acid level and enhances osteopontin mRNA level in murine osteoblast-like (MC3T3E1) cells. 211 64

The studies presented in this report describe an initial characterization of cell types derived from explants of human periodontia. Cell cultures were established from human periodontal ligament (PL4, PL7), gingival tissue (GF2), and alveolar bone (BP1) by means of explant techniques and monolayer culture. Cells were studied at passage numbers 2-4 and were characterized on the basis of morphological, biochemical, and proliferative parameters. Subconfluent cells did not have distinct morphologies useful in distinguishing them from one another. At confluence, PL4 and BP1 cells formed multilayered cultures of randomly oriented cells, while PL7 and GF2 cells grew in a monolayer of parallel cells. Biochemically, PL4 and BP1 cells exhibited characteristics consistent with an osteoblast-like phenotype. These included a significant increase in PTH-stimulated cyclic AMP and high basal levels of alkaline phosphatase activity, which were decreased on exposure to PTH and increased after stimulation by 1.25 dihydroxyvitamin D3. In contrast, PL7 and GF2 cells exhibited basal alkaline phosphatase levels that were low, and cyclic AMP levels were not modulated by PTH stimulation. Cell populations PL7 and GF2 did not proliferate in culture medium supplemented with 3% platelet-poor plasma. After the addition of platelet-derived growth factor (PDGF) to this medium, the proliferation of these cell populations was equal to that in media supplemented with 10% fetal bovine serum. In contrast, PL4 and BP1 cells did proliferate in culture medium supplemented with 3% platelet-poor plasma. The addition of PDGF to the medium resulted in only a moderate increase in the proliferation of cell populations PL4 and BP1.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Initial characterization of cells derived from human periodontia. 254 Nov 86


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