Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mo3 is an activation Ag expressed on the surface of human mononuclear phagocytes stimulated in vitro or in vivo by various activating factors. Mo3 is obtained by immunoprecipitation with anti-Mo3 mAb from lysates of PMA-stimulated U-937 cells. The Ag is a heterogeneous glycoprotein with a molecular mass range of 42 to 66 kDa (nonreducing conditions) containing N-linked carbohydrate chains. When the cells are treated with phosphatidylinositol-specific phospholipase C, greater than 60% of total precipitable gp42-66 Ag is released in the supernatant. This phosphatidylinositol-specific phospholipase C-sensitive linkage to the plasma membrane has provided a means for the one-step purification of Mo3 by immunoaffinity chromatography. The eluted soluble Mo3 (sMo3) was greater than 90% pure as documented by the appearance of a single major protein peak on reverse phase HPLC and SDS-PAGE. The average yield was 12.1 micrograms/10(8) cells. Sufficient quantities of sMo3 have been purified to permit the determination of amino acid and carbohydrate composition. Complex N-linked carbohydrates make up nearly 50% of the glycoprotein content and contribute to its heterogeneity. An anti-Mo3 polyclonal antiserum generated from sMo3 was used to immunoprecipitate Mo3 and its precursor from biosynthetically labeled, PMA-stimulated U-937 cells or LPS-stimulated monocytes. These 35S-methionine "pulse-chase" experiments demonstrated the existence of a 40- to 42-kDa endo-beta-N-acetylglucosaminidase-sensitive precursor, which over a period of 4 to 5 h gave rise to an endo-beta-N-acetylglucosaminidase-resistant, but N-glycanase-sensitive 42- to 66-kDa mature form.
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PMID:Purification, biochemical composition, and biosynthesis of the Mo3 activation antigen expressed on the plasma membrane of human mononuclear phagocytes. 186 26

Mo3 is an activation Ag expressed by human monocytic cells after stimulation in vitro by PMA, LPS, certain cytokines, and muramyl dipeptide. The structural characterization of Mo3 has been made possible by the development of a mAb (anti-Mo3f) that immunoprecipitates Mo3 from Nonidet P-40 lysates of radiolabeled PMA-stimulated U-937 cells and LPS-activated monocytes. On SDS-PAGE (nonreducing conditions) of anti-Mo3f immunoprecipitates, U-937 Mo3 is a single broad band of 39 to 66 kDa, whereas monocyte Mo3 is smaller with an apparent molecular mass of 32 to 56 kDa. Under reducing conditions, there is an increase in the m.w. of both species of Mo3 suggesting the existence of internal disulfide bonds. Mo3 is a glycoprotein with carbohydrate of the N-linked complex type as evidence by a reduction in m.w. by 40 to 50% after treatment with endoglycosidase F or N-glycanase; neuraminidase treatment produces a 3-kDa reduction in m.w. Deglycosylated Mo3 isolated from U-937 and monocytes have similar m.w. suggesting that the molecular heterogeneity of the native Mo3 may be due to differences in glycosylation. Mo3 is sensitive to phosphatidylinositol-specific phospholipase C with the release of native Mo3 from the surface of PMA-stimulated U-937 cells. These results indicate that Mo3 is a member of the glycosylphosphatidylinositol-linked family of surface glycoproteins.
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PMID:A structural characterization of the Mo3 activation antigen expressed on the plasma membrane of human mononuclear phagocytes. 213 44

Macrophage activation activity was characterized from a PMA-induced subclone of the murine EL-4 leukaemic cell line. The MAF was purified from the cell line culture supernatant by concentration, CM-Sepharose and lentil lectin Sepharose chromatography, AcA 54 gel filtration, Mono Q FPLC and reverse phase HPLC. Four protein bands of different abundance were observed on SDS-PAGE with molecular weights of 17,500 to 21,000 Da. Three of the four proteins were sequenced from the N-terminal and shared homology with the published sequence of BSF-1. Variation of the molecular weight due to glycosylation was demonstrated by N-glycanase treatment, all four proteins gave a band of 14,200 Da after deglycosylation. Both glycosylated and deglycosylated forms of BSF-1 were equally active in the MAF assay. A monoclonal antibody to BSF-1 neutralized 80% of the activity from crude culture supernatants in the MAF assay. These studies have indicated that BSF-1 is the major, if not the only, MAF activity from this particular subline of the murine EL-4 leukaemic cell line.
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PMID:Purification and sequencing of glycosylation variants of BSF-1, as a MAF, from the EL-4 leukaemia cell line. 264 99

The high affinity Fc receptor (FcRI) of a human monocytic cell line, U937, was further characterized using a previously described murine monoclonal antibody, FcRmAb32. This antibody immunoprecipitated a 70 K cell surface glycoprotein. A solid phase ligand binding assay and a solid phase immunoprecipitation assay were combined to confirm that the 70 K cell surface glycoprotein immunoprecipitated by FcRmAb32 is an IgG binding protein. N-glycanase digestion shows that at least 20% of the relative mobility of the 70 K FcRI glycoprotein is due to N-linked carbohydrate. FcRmAb32 immunoprecipitated a 70 K glycoprotein from biosynthetically labelled U937 cells that co-migrated with the surface iodinated glycoprotein on 2-dimensional gel electrophoresis. A 50 K protein, that is biosynthetically labelled but not accessible to surface iodination, which, bound to control antibodies was also present in FcRmAb32 immunoprecipitates. FcRmAb32 only bound the mature fully glycosylated form of FcRI. The 70 K FcRI was not phosphorylated constitutively nor when U937 cells were stimulated by PMA.
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PMID:Characterization of the human monocyte high affinity Fc receptor (hu FcRI). 296 28

Expression, saturation, and endocytosis of IgA Fc receptors (Fc alpha R) were analyzed in blood phagocytic cells of patients with alcoholic liver cirrhosis (ALC). Surface Fc alpha R expression was decreased in monocytes but not in neutrophils, as evaluated by IgA binding and anti-Fc alpha R mAb. The Fc alpha R of ALC patients were saturated by IgA1 and IgA2. ALC Fc alpha R had a higher M(r) (60 to 90 kDa) than those of controls (55 to 75 kDa) with a similar 32-kDa protein core after N-glycanase treatment, suggesting the expression of Fc alpha R molecules with altered carbohydrate moieties. Treatment of U937 cells with IFN-gamma induced a decrease of surface Fc alpha R expression in a dose-dependent manner, with a similar M(r) as observed for ALC patient Fc alpha R (60 to 90 kDa). Fc alpha R endocytosis was induced by anti-Fc alpha R or IgA. Neutrophils internalized Fc alpha R molecules faster than did monocytes. Endocytosed Fc alpha R co-localized with cathepsin D, suggesting an endolysosomal compartment pathway. In ALC monocytes, Fc alpha R endocytosis was defective, with nearly 50 to 60% of receptors detected on the cell surface even after 90 min at 37 degrees C. Similarly, delayed Fc alpha R endocytosis was observed on IFN-gamma-treated U937 cells as compared with PMA-activated cells. Defective internalization of surface-bound IgA with reflux of IgA to cell surface was also observed on ALC monocytes, but not on normal cells preincubated with patients' plasma, ruling out direct effects of IgA. The inverse correlation between monocyte Fc alpha R levels and serum IgA levels associated with defective endocytosis suggest that altered Fc alpha R expression might contribute to receptor saturation and generation of increased plasma levels of IgA and IgA-immune complexes in ALC patients.
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PMID:Altered expression of monocyte IgA Fc receptors is associated with defective endocytosis in patients with alcoholic cirrhosis. Potential role for IFN-gamma. 763 20

Two cytoplasmic variants of the alpha 6 integrin, alpha 6A and alpha 6B, have been identified previously (Hogervorst, F., I. Kuikman, A. G. van Kessel, and A. Sonnenberg. 1991. Eur. J. Biochem. 199:425-433; Cooper, H. M., R. N. Tamura, and V. Quaranta. 1991. J. Cell Biol. 115:843-850). Using synthetic peptides, containing sequences of their cytoplasmic domains, we have produced mAbs specific for either of the variants. These antibodies reacted with a variety of different epithelial tissues. In some tissues (e.g., salivary gland) both variants could be detected while in others only one of the variants was found (e.g., alpha 6A in epidermis and alpha 6B in kidney). Among nonepithelial cells and tissues, perineural fibroblasts and Schwann cells in peripheral nerves and platelets reacted with anti-alpha 6A, while microvascular endothelia reacted with both anti-alpha 6A and anti-alpha 6B. From our immunohistochemical results there is not evidence that combination with beta 1 or beta 4 is restricted to one of the two variants of alpha 6. This was confirmed by immunoprecipitation studies which showed that both beta 1 and beta 4 were coprecipitated by both anti-alpha 6A or anti-alpha 6B antibodies from cells. Also, the distribution of alpha 6A and alpha 6B subunits associated with beta 1 on cells attached to laminin was similar: both were found in focal contacts colocalizing with vinculin. In contrast, the alpha 6A subunit, associated with beta 4 in cultures of a squamous cell carcinoma cell line, was found to codistribute with bullous pemphigoid antigen 230 in hemidesmosomal-like structures. The alpha 6A and alpha 6B variants, immunoprecipitated from various cell lines, exhibited slightly different electrophoretic mobilities. Analysis of the antigens under reducing conditions showed that the mobility of the light chains, but not of the heavy chains, is different. In addition, in some cells the light chains of alpha 6A and alpha 6B, each are of two different sizes. Treatment with N-glycanase showed that these two light chain variants of alpha 6A and alpha 6B are not due to differences in N-linked glycosylation, and may therefore represent alternative proteolytic products of the alpha 6 precursor. We further demonstrate that alpha 6A, but not alpha 6B, is a major target for PMA-induced phosphorylation. Phosphorylated alpha 6A contained phosphoserine and a small amount of phosphotyrosine. There are also two variants of the integrin alpha 3 subunit with different cytoplasmic domains, but in the cell lines examined only alpha 3A could be demonstrated by RT-PCR.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Biochemical characterization and tissue distribution of the A and B variants of the integrin alpha 6 subunit. 768 34

Among a panel of mouse mAbs generated to a human T cell clone, one mAb, V7.1, inhibited T cell activation in the mixed lymphocyte reaction and was studied further. V7.1 reacted strongly with Ag-specific T cell clones, in addition to freshly isolated monocytes and granulocytes. However, the mAb reacted weakly with freshly isolated PBLs (T cells, B cells, and NK cells), T cells stimulated with phytohemagglutinin, or Con A, and did not stain the vast majority of transformed cell lines of hemopoietic origin. Stimulation of T cells with anti-CD3, or the combination of anti-CD3 and PMA, or anti-CD3, PMA and ionomycin, markedly increased V7.1 surface staining. The mAb precipitated a single polypeptide chain of approximately 135 kDa from alloactivated T cells or monocytes, which was reduced to approximately 110 kDa after treatment with N-glycanase. The proliferative response of T cells to allogeneic monocytes or B lymphoblastoid cells was inhibited by V7.1, and inhibition was maximal when the mAb was present at the initiation of culture. V7.1 also exhibited dose-dependent inhibition of the T cell response to immobilized anti-CD3 Ab in the absence of APCs, indicating that the inhibitory effect of this Ab occurs at the T cell level. Expression of CD25 (IL-2R) on anti-CD3-activated T cells and secretion of IL-2 induced with anti-CD3 and PMA were inhibited by V7.1, whereas the Ab had no effect on T cell proliferation induced by PHA or Con A or on T cell-mediated cytotoxicity. These results indicate that V7.1 recognizes a novel leukocyte surface glycoprotein, designated V7, that is up-regulated on Ag but not lectin-activated T cells, and appears to play a role in TCR/CD3-dependent T cell activation. In an accompanying study, the gene encoding the V7 Ag is described and the molecule is shown to be a novel member of the Ig superfamily.
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PMID:V7, a novel leukocyte surface protein that participates in T cell activation. I. Tissue distribution and functional studies. 772 99