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:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

PC12 cells possess two classes of nerve growth factor (NGF) receptors on their surfaces which can be distinguished by kinetic criteria. The majority class binds and releases 125I-NGF at a relatively rapid rate and has been called fast. The second class of receptors has been called slow because of relatively slower rates of binding and release of 125I-NGF, and also may be distinguished from fast receptors by their cytoskeletal association and resistance to trypsin. PC12 cell plasma membranes were prepared and shown to have only the fast class of receptors. These membranes were fused to receptorless 3T3 cells with polyethylene glycol. The resultant fused cells were shown to possess NGF receptors, essentially all of which behave like slow receptors. Immunofluorescence microscopy was used to monitor the introduction of PC12 cell membrane and NGF receptors into 3T3 cells. Results obtained with C10-2, a monoclonal antibody specific for a major PC12 cell-surface antigen. show that up to 90% of 3T3 cells receive PC12 membrane and that the PC12 membrane becomes integrally incorporated into the 3T3 cell plasma membrane. It is suggested that an association of receptors with cytoskeleton may be involved in the conversion of fast to slow receptor behavior, and that the differing proportion of fast and slow NGF receptors in PC12 and 3T3 cells reflects the differing cytoskeletal organization of these cells.
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PMID:The nerve growth factor receptor on PC12 cells: interconversion between two forms with different binding properties. 630 52

Surface markers of human gingival fibroblasts in vitro were investigated using monoclonal and heterologous antisera against a range of cell surface antigens, together with rosetting techniques to characterize surface receptors for IgG and C3. WI-38 fibroblasts and human peripheral blood monocytes were used as control cells. Human gingival fibroblasts exhibited complement receptors and beta2-microglobulin, as did WI-38 cells. Ten per cent of the human gingival fibroblasts were positive for HLA-DR antigens and additionally exhibited a granulocyte antigen not apparent on WI-38 cells. Monolayers of the gingival fibroblasts were further exposed for short periods to varying concentrations of enzymes (trypsin, collagenase and neuraminidase), bacterial extracts (lipopolysaccharide and lipoteichoic acid) and crude supra- and subgingival plaque sonicates. Surface-marker analysis was then carried out. The most noticeable effects were obtained with Vibrio cholerae neuraminidase which enhanced C3 receptor and surface antigen expression, and supragingival plaque sonicate which depressed the expression of HLA-DR and granulocyte antigens while not affecting beta2-microglobulin expression. Trypsin reduced antigen expression to a degree, but its effects were mainly on cell adherence.
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PMID:Surface markers of human gingival fibroblasts in vitro. Characterization and modulation by enzymes and bacterial products. 633 Mar 32

Indirect immunofluorescence has been used to examine surface antigens of lizard myogenic cells during in vitro differentiation. At least two developmental stage-specific surface alterations have been identified. One of these is a compositional change and involves the appearance of a cell-surface antigen(s) as the cells differentiate. This antigen(s) (Ag1422) is muscle specific and is characteristic of some rounded-up G0 myosin-positive myocytes, all stretched-back, G0 myosin-positive myocytes, and all identifiable myotubes. The antigen is not found on proliferating myoblasts, extended G1 (myosin-negative) cell-cycle-competent myoblasts or newly differentiated rounded-up, G0 myosin-positive myocytes. Pretreatment of cells with neuraminidase, trypsin, or proteinase K indicates the antigen is not present in "masked" form on normally nonreactive cells. Proteinase K is effective in the removal or destruction of the antigen, indicating it is at least partially protein in nature. The antigen is expressed in a similar developmental stage-specific fashion on early-passage myogenic cells taken from both adult lizard tail regenerates and embryonic muscle. The antibodies identifying Ag1422 can be removed by adsorption with homogenates of mature skeletal muscle. Therefore, Ag1422 is not an artifact due to in vitro conditions or the expression of a transformation antigen unique to the continuous culture line. The second alteration is an apparent restriction in the mobility of surface components (antigens and lectin receptors). Upon treatment with multivalent ligands, undifferentiated myosin-negative myoblasts exhibit rapid patching and capping of cell surface components while well-differentiated myocytes and myotubes do not. This mobility restriction is evident after the appearance of Ag1422. Treatment with cytochalasin B (15 micrograms/ml) and/or colchicine (100 microM) does not alter the restricted mobility of surface components seen on differentiated cells. Therefore, neither microfilaments nor microtubules seem to be involved in the mobility restriction. These observations are discussed in relation to current views of myogenesis.
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PMID:Changes in cell surface antigens during in vitro lizard myogenesis. 634 59

Since the immunosorbent techniques and the cycles of isopycnic and rate zonal velocity ultracentrifugations were shown to be unsuitable for the purification of hepatitis B surface antigen (HBsAg) particles from human sera because HBsAg was still largely contaminated by serum proteins, we applied a drastic dissociating treatment of HBsAg stabilized by adsorption on silica gel which appeared essential to remove extraneous components initially present in the HBsAg particles. Only albumin and sometimes IgG were recovered with the purified antigen. The polypeptide composition of our purified HBsAg preparations was analyzed by SDS-PAGE with subsequent transfer to a nitrocellulose sheet by blotting, incubation with 125I-anti-HBs and exposure to X-ray film. Samples from HBsAg-positive sera containing the hepatitis B virus e antigen (HBeAg) displayed three proteins: P 24.5 and GP 28 as major components and GP 36 as a minor component. Dimers of these polypeptides were also immunologically detected. When a supplementary step of trypsin or pepsin digestion was included in our purification procedure after adsorption to silica and acid dissociation of HBsAg, proteolytic cleavage fragments of HBsAg with mol. wts lower than 10,000 were obtained on SDS-PAGE after reduction. This finding shows that arginine and lysine residues inaccessible to tryptic digestion in the intact HBsAg lipoprotein particle were exposed to enzymatic hydrolysis by our treatment. However, HBsAg kept the antigenic and immunogenic properties of the native antigen. Therefore such a HBsAg preparation appeared as a new candidate for the vaccination against HBV and a useful material for the analysis of the HBs antigenic structure.
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PMID:Immunochemical structure of the hepatitis B surface antigen vaccine--I. Treatment of immobilized HBsAg by dissociation agents with or without enzymatic digestion and identification of polypeptides by protein blotting. 642 72

Macrophages play a requisite role in the induction and expression of T lymphocyte responses to Listeria monocytogenes. For effective T cell-macrophage interaction to occur, macrophages must perform at least two fundamental functions. They must take up and handle the antigen, and they must express appropriate membrane glycoproteins encoded for by the I-region of murine major histocompatibility gene complex (Ia molecules). Data collected in a murine model suggests that the following sequential events are involved in the Listeria-macrophage-T cell interaction. Listeria interaction with macrophage cell surface via trypsin sensitive structures. Interiorization within phagosomes. Phagosome-lysosome fusion. Partial degradation of Listeria. Transfer of protein antigen fragments to macrophage cell surface. Recognition of macrophage surface antigen and I-region associated (Ia) molecules by the T cell receptor. The essential feature of this model is that: antigen handling occurs intracellularly and independently of macrophage cell surface Ia molecules. With regard to the survival advantage of this mechanism, one may speculate that the degradation of pathogens by macrophages may serve to increase the number of different structural moieties which can act as antigens. Thus, bacterial components normally sequestered in the interior of organisms could conceivably serve as antigens, and the multiplicity of such antigenic determinants would make it less likely that a nonresponder status with respect to I-region gene function would be generated. This mechanism may be especially relevant to host defense against intracellular pathogens such as Listeria monocytogenes.
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PMID:The processing and presentation of Listeria monocytogenes antigens by macrophages. 644 50

The 20-nm particles of hepatitis B surface antigen (HBsAg) contain two minor glycoproteins, GP33 and GP36, which are probably encoded at their 55 N-terminal amino acids by the pre-s region of the viral DNA. Their 226 C-terminal amino acids are identical to the major protein P24. The 20-nm particles contained more GP33 and GP36 when the blood had a high HBsAg concentration. They were also found in relatively high amounts in HBsAg filaments and virions. Treatment with glycosidase and trypsin showed that the mannose rich glycan and the N-terminal portion of GP33 and GP36 were exposed at the surface of the HBsAg particles. The 20-nm particles containing much GP33 and GP36 did not induce higher anti-HBs titers in guinea pigs than those particles almost devoid of them.
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PMID:Characterization of pre-s gene products in hepatitis B surface antigen. 665 88

Deparaffinized sections of hepatitis B surface antigen (HBsAg) positive liver biopsies, when incubated in a human fibrinogen solution, reveal a strong labelling of ground-glass hepatocytes with fibrinogen. This implies an interaction between HBsAg and fibrinogen. The binding of fibrinogen to HBsAg is thought to be mediated by the protein moiety of HBsAg, since its binding capacity is destroyed by trypsin digestion, and to occur through formation of disulphide bridges because the binding can be disrupted by the reducing effect of 2-mercapto-ethanol. Not all ground-glass hepatocytes exhibit fibrinogen binding. The reason for this is at present unclear. No relationship between serum HBeAg positivity and binding of HBsAg to fibrinogen was observed. Preincubation in a fibrinogen solution did not alter the immunoreactivity of HBsAg. We conclude that there is a striking analogy between the interaction of HBsAg with polymerized human serum albumin and its interaction with fibrinogen.
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PMID:Hepatitis B surface antigen (HBsAg)-fibrinogen interaction. 672 84

Nine monoclonal antibodies against surface antigens of sporozoites of the simian malaria parasite Plasmodium knowlesi were produced by fusion of plasmacytoma cells with spleen cells of a mouse immunized with the parasites. Immunoprecipitation of extracts of [35S]methionine-labeled sporozoites with seven of the monoclonals identified the same three polypeptides with apparent molecular weights of 52,000 (Pk52), 50,000 (Pk50) and 42,000 (Pk42). These antigens also were recognized by serum of a rhesus monkey immunized with and protected against P. knowlesi sporozoites. Pulse--chase experiments indicated that the higher molecular weight proteins are precursors of Pk42. As shown by trypsin treatment of viable sporozoites, Pk42 is a surface antigen whereas Pk52 and Pk50 appear to be intracellular. Three of the monoclonal antibodies also reacted with a membrane antigen of sporozoites of another simian malaria, P. cynomolgi, and one monoclonal antibody reacted with sporozoites of human malaria, P. falciparum. When assayed for sporozoite neutralizing activity, most of the antibodies and their Fab fragments, which recognize Pk52, Pk50, and Pk42, abolished parasite infectivity.
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PMID:Monoclonal antibodies identify the protective antigens of sporozoites of Plasmodium knowlesi. 695 83

We describe a new cellular component of normal mouse thymuses, which is isolated by fractionated trypsin dissociation of minced thymus tissue followed by repeated unit gravity sedimentation. These cells are of unusually large size, with diameters of 30 mum and more. They represent cellular complexes of single large cells filled with high numbers of lymphoid cells. The majority of the engulfed lymphoid cells is not only fully intact, as judged by morphological criteria, but, moreover, includes a high proportion of mitotic figures. Electron microscopic investigations reveal the epithelial character of the large thymic nurse cells (TNC). The peripherally situated cytoplasmic tonofilament streams, and characteristic vacuoles filled with coarse, unidentified material, closely resemble cytoplasmic organelles found in the cortical reticuloepithelial cells described in situ. The internalized lymphocytes are located within caveolae lined by plasma membranes. These TNC caveolae are completely sequestered, and have lost any communication with the extracellular space, as demonstrated by the inability of an electrondense marker, cationized ferritin, to diffuse into the perilymphocytic clefts. The structural interactions between the membranes of the engulfed thymocytes with the surrounding TNC caveolar membranes were investigated both in ultrathin sections and in freeze-etch preparates. Two distinct contact types between both membranes were discerned: (a) complete, close contact along the entire lymphocyte circumference, and (b) more frequently, contact restricted to discrete, localized areas. Judging from their size and distribution, the localized contacts could correspond particle aggregates of freeze-etch preparates, which morphologically resemble certain stages of gap junction. Furthermore, we regularly found square arrays of particles of uniform size, which so far have been thought to be typical for cell membranes actively engaged in ion exchange. Tight junction-like particle arrays, which were present on TNC outer membranes, and probably represented disrupted contacts between adjacent TNC in the intact tissue, could not be found on caveolar or lymphocyte membranes. Finally, one of the most conspicuous specializations of the TNC caveolar membrane were membrane invaginations, which were arranged mainly in groups, and which probably reflect endo- or exocytotoxic events. We investigated the surface antigen phenotype of TNC by indirect immunofluorescence, with monoclonal antibodies against determinants of H-2- complex subregions as well as against lymphocyte differentiation markers. Semiquantification was reached with flow cytofluorimetry, followed by morphological control by fluorescence microscopy. The surface antigen formula of TNC is: Ig(-), Thy-l(-), H-2K(++), I-A (++), I-E/C(+), H-D(++), Ly-1(-), Ly-2(-), Qat-4(-), Qat-5(-), and peanut agglutinin (PNA)(-). Thymic macrophages, which were identified by double fluorescence, with rhodamine- coupled zymosan as a phagocytosis marker, were serologically identical with TNC. Free thymocytes, in contrast, had the following antigen formula: Ig(-), Thy-1(++), H-2K(+/-), I-A(-), I-E/C(-), H-2D(+/-), Ly-1(+/-), Ly-2(+), Qat- 4(-), Qat-5(-), and PNA(+). The unprecedented finding of high numbers of dividing thymocytes sojourning within thymic epithelial cells, and the particular specializations of the TNC caveolar membranes surrounding these engulfed thymocytes is the basis of a hypothesis that postulates that an intraepithelial differentiation cycle is one essential step in, intrathymic T lymphocyte generation.
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PMID:Thymic nurse cells. Lymphoepithelial cell complexes in murine thymuses: morphological and serological characterization. 696 12

Marek's disease tumor-associated surface antigen (MATSA) has been claimed to be the target of cytotoxic lymphocytes in in vitro tests for Marek's disease immunity. Treatment with papain, but not with trypsin or mixed glycosidases, removed MATSA from certain Marek's disease lymphoblastoid cell lines. Tumor cells with and without MATSA were used as target cells for in vitro studies on cell-mediated immune responses with sensitized spleen cells in a chromium release assay. The removal of MATSA did not influence the results of the chromium release assay. Attempts to block the cell-mediated cytotoxicity in vitro by coating tumor cells with an anti-MATSA serum failed. It was concluded that cell-mediated immune responses against Marek's disease tumor cells are directed against an as yet undefined antigen(s).
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PMID:In vitro cytotoxicity against Marek's disease lymphoblastoid cell lines after enzymatic removal of Marek's disease tumor-associated surface antigen. 696 35


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