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)

Quantitative analyses of Staphylococcus aureus binding to platelets were done using flow cytometry after bacterial exposure to the following treatments: proteases (trypsin, protease K), antibiotics (oxacillin, gentamicin), surface carbohydrate modifiers (sodium periodate, anticapsular antibody), or platelet microbicidal protein. In separate studies, platelets were exposed to a monoclonal antibody to their Fc receptor (Fc gamma RII) before binding was quantified. The percentage of bacteria bound to platelets varied significantly among strains (22.1% +/- 3.8% to 76.4 +/- 3.2%). For all isolates, binding to platelets was rapid, saturable, and reversible, suggesting a receptor-ligand interaction. The following modifiers significantly reduced binding: platelet microbicidal protein (by 32.1% +/- 5.2%; P less than .001), homologous (but not heterologous) anticapsular antibody (by 17.7% +/- 1.9%; P less than .05), sodium periodate (by 36.3% +/- 4.3%; P less than .005), and anti-platelet Fc monoclonal antibody (by 41.5% +/- 4.4%; P less than .002). Collectively, these data suggest that the mechanism(s) involved in S. aureus-platelet binding are complex and multimodal, involving carbohydrate-rich and platelet microbicidal protein-susceptible S. aureus surface ligands as well as the platelet Fc receptor.
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PMID:Characterization of Staphylococcus aureus-platelet binding by quantitative flow cytometric analysis. 131 11

In a recent series of experiments, we observed that epidermal Langerhans cells (LC) of healthy, non-atopic individuals have the capacity of specifically binding monomeric serum or myeloma IgE. IgE-binding to LC could neither be prevented by pre-incubation of the cryostat sections with monoclonal antibodies (MoAb) against either Fc epsilon RII/CD23 or Fc gamma RII/CD32 nor by the addition of excess amounts of lactose, but could be entirely abrogated by pre-incubation with the anti-Fc epsilon RI MoAb 15-1. A direct testing of the anti-Fc epsilon RI MoAb 15-1 and 19-1 on cryostat sections in an indirect immuno-double-labeling technique showed that, in contrast to eight different anti-Fc epsilon RII/CD23 MoAb, these MoAb react with the majority of CD1a-bearing epidermal cells. At an ultrastructural level, 15-1 immunogold-labeling in the epidermis was confined to the surface of cells exhibiting Birbeck granules. In further experiments, we were able to amplify by polymerase chain reaction (PCR) technology transcripts for the alpha, beta, and gamma chains of Fc epsilon RI from LC-enriched epidermal cells and dermal cells, but not from LC-depleted epidermal cells. Transcripts for the mast cell enzyme tryptase were exclusively found in dermal cell-derived RNA preparations, thus excluding a contamination of the LC-enriched epidermal cell preparations by dermal mast cells. Collectively, these data show that epidermal LC, but not other epidermal cells, express Fc epsilon RI molecules.
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PMID:Fc epsilon RI mediates IgE binding to human epidermal Langerhans cells. 143 Dec 5

Fc gamma R expressed by mouse mast cells were characterized as functional binding sites, as membrane proteins, and as products of the two genes known to encode murine Fc gamma RII. Peritoneal mast cells, bone marrow-derived mast cells (BMMC), and the mastocytoma cells P815 were found to bear trypsin-resistant, 2.4G2+, low-affinity receptors binding mouse monoclonal IgG1, IgG2a, and IgG2b, i.e., Fc gamma RII. BMMC and P815 Fc gamma RII appeared as heterogeneous membrane proteins that, when deglycosylated, had m.w. corresponding to those of the three known products of the alpha and beta Fc gamma R genes, and differed by their respective contents in BMMC and P815 cells. Heterogeneous Fc gamma R transcripts were also found in BMMC and in P815 RNA. P815 cells contained alpha, beta 1, and beta 2 Fc gamma R transcripts, whereas BMMC contained alpha and beta 1 Fc gamma R transcripts. These data disclose an unexpected molecular heterogeneity of murine mast cell Fc gamma R. Although they appear as a single population of receptors when viewed by external ligands, mast cell Fc gamma R comprise three Fc gamma RII subtypes, encoded by the three known transcripts of the alpha and beta Fc gamma R genes, and differing by their intracytoplasmic portion. The different distributions of Fc gamma RII transcripts and corresponding Fc gamma RII subtypes in different types of mast cells may be determinant for triggering the various biologic activities of these cells.
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PMID:Molecular heterogeneity of murine mast cell Fc gamma receptors. 213 78

Treatment of monocytes or K562 cells with proteolytic enzymes like pronase or trypsin, increases both the affinity of the type II Fc receptor for IgG and the signaling via this receptor. In the present study we evaluated whether other proteases could similarly enhance Fc gamma RII affinity. We furthermore assessed whether all cell types expressing Fc gamma RII display this effect. Therefore, proteins from the coagulation system and PMN-derived enzymes were tested for effects on Fc gamma RII-mediated ligand binding. Enzymes of the coagulation system were tested both in fibrinogen-depleted plasma, as well as in purified form. No effects were found on Fc gamma RII-mediated rosette formation for both situations. In contrast, supernatant of stimulated granulocytes as well as leucocyte elastase were observed to be active in augmenting EA-hIgG rosette formation of thrombocytes and myeloid cell lines K562 and U937. The B cell lines Raji and Daudi, did not show enhanced rosette formation after enzyme treatment. The active component from granulocyte supernatant was partially characterized as a serine esterase with an apparent Mw of 30 kD. We tested whether the isotype specificity of Fc gamma RII on K562 cells changes upon enzyme treatment. It was found that all three tested murine subclasses gamma 1, gamma 2a, gamma 2b, bound equally well to this receptor, and interaction with all isotypes was enhanced to the same extent.
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PMID:PMN-derived proteases enhance the affinity of Fc gamma receptor II on myeloid cells, but not on B cells. 214 7

Varicella-zoster virus (VZV) specifies the synthesis of viral glycoproteins which are important antigens for induction of the host immune response. In this report the technology of laser-activated flow cytometry has been employed to measure the membrane expression of VZV glycoproteins gpI, gpII, gpIII, and gpIV. By use of biotinylated monoclonal antibodies as probes, all four glycoproteins were demonstrated on the infected cell surface. The temporal appearance of the viral glycoproteins was defined in a time course experiment and shown to be maximal about 24 hr postinfection. The issue whether VZV induces the cell surface expression of an Fc receptor (FcR) was investigated with biotinylated nonimmune human IgG, followed by streptavidin-phycoerythrin. By this technique a 10-fold increase in fluorescence intensity was seen in the VZV-infected cells as compared to the mock-infected controls. When the experiment was repeated with purified human Fc fragment rather than whole IgG, a similar degree of binding was seen. Both the VZV glycoproteins and the VZV FcR were exquisitely sensitive to trypsin treatment (1 mg/ml); likewise, the cell surface expression of these VZV products was diminished by treatment of the infected cultures with monensin, an inhibitor of glycoprotein transport. In order to prove that VZV infection was not causing the induction of a cellular Fc gamma R, the VZV-infected and mock-infected cells were stained with monoclonal antibodies directed against each of the three human cellular IgG FcR, but no differences were observed. Therefore, the FcR activity seen in the infected culture was not due to one of the known cellular Fc gamma R.
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PMID:Cell surface expression of the varicella-zoster virus glycoproteins and Fc receptor. 216 54

Glycosylated chimeric mouse-human anti-NIP IgG3 antibody produced by growth of the J558L mouse B cell plasmacytoma is characterised with respect to the single carbohydrate chain at Asn-297 in the CH2 domain indicating that the mouse cell glycosyl transferases dictate the pattern of glycosylation rather than the human CH region of the heavy chain. Additionally, three unusual alpha-galactose-containing oligosaccharides are reported. Only the Fc region has detectable carbohydrate. Aglycosylated anti-NIP IgG3 antibody has been produced by cell growth in the presence of the antibiotic tunicamycin. Functionally, whilst the glycosylated intact IgG3 interacts with human Fc gamma R111 expressed on human killer (K) cells to trigger antibody-dependent cellular cytotoxicity the aglycosylated intact IgG3 fails to trigger cell lysis, localising the site on IgG for triggering human Fc gamma R111 mediated functions to the CH2 domain. The monomeric aglycosylated trypsin Fc fragment inhibits human Fc gamma R1 recognition by U937 cells 115-fold less well (K50 = 2 microM) than does glycosylated Fc (K50 = 17 nM), confirming that aglycosylation disrupts the site for human Fc gamma R1 within the CH2 domain and indicating that the trypsin Fc fragments reflect the functional properties of the intact IgG glycoforms. Structurally, 1H NMR shows that the absence of carbohydrate at Asn-297 results in a small and localised protein structural change in the vicinity of the reporter group His-268 within the CH2 domain. The site on IgG for triggering human Fc gamma R111 mediated functions is then localised to the vicinity of His-268. The profound impact of aglycosylation on human Fc gamma R1 recognition implies structural disruption of the proposed site for human Fc gamma R1 in the lower hinge region of IgG (residues 234-239), proximal to His-268.
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PMID:A protein structural change in aglycosylated IgG3 correlates with loss of huFc gamma R1 and huFc gamma R111 binding and/or activation. 217 19

Receptors for the Fc fragment of immunoglobulins (Fc R) exhibit specificities for a wide variety of immunoglobulin classes and subclasses. In humans, at least three distinct classes of receptors for the Fc fragments of IgG (Fc gamma RI, II, III) and two classes of receptors for the Fc fragments of IgE (Fc epsilon RI, II) have been characterized. These classes were largely defined on the basis of their affinities for different immunoglobulin subclasses and their reactivities with monoclonal anti-receptor antibodies. Among these FcR, in healthy individuals, epidermal Langerhans cells (LC) express only the Fc gamma RII/CDw32. This FcR--a member of the immunoglobulin superfamily--is only present on about 50% of freshly isolated CD1a positive cells, as determined by rosette assays. It has a Mr of 40 kDa, is trypsin resistant, binds polymeric human IgG and murine IgG1-coated erythrocytes, and reacts with anti-CDw32 monoclonal antibodies (MoAb). LC internalize Fc gamma RII by receptor-mediated endocytosis. After 48 h of culture, human LC loose their Fc gamma RII, as revealed by flow cytometry. While the function(s) of the Fc gamma RII on human LC remain(s) unknown, this receptor may be primarily involved, like the Fc gamma RII present on mouse macrophages, in the clearance of extra-cellular immune complexes. In patients with atopic dermatitis having an elevated IgE serum level, beside an increased expression of the Fc gamma RII by LC located on lesional skin, IgE-bearing epidermal and dermal LC are present, again essentially on lesional skin. Double immunolabeling on cryosections reveals that on lesional skin only about 50% of the epidermal CD1a positive cells bear IgE. This capacity of LC to bind IgE molecules appears to be due to the presence of a specific Fc epsilon R. While the class of this Fc epsilon R still remains unclear, it appears to have some particularities: i) an associated expression with the CD1a antigen, ii) an affinity for IgG, and iii) a trypsin resistance. In vitro, human recombinant interleukin (IL)-4 and/or interferon (IFN)-gamma are able to induce the synthesis and expression of Fc epsilon RII/CD23 on a percentage of normal human epidermal LC. This Fc epsilon RII seems to be functional since it binds IgE molecules, this binding being prevented by preincubation with anti-CD23 MoAb.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Fc receptors of human Langerhans cells. 219 Oct 49

Human monocytes express two types of IgG FcR, Fc gamma RI and Fc gamma RII. These can be assayed by using indicator E sensitized by human IgG (EA-human IgG) or mouse IgG1, (EA-mouse IgG1), respectively. On mouse macrophages, Fc gamma RI is sensitive to trypsin, whereas Fc gamma RII is trypsin resistant. We studied the effects of the proteolytic enzymes pronase and trypsin on human monocyte Fc gamma R. Neither enzyme caused a decrease in rosetting mediated by monocyte Fc gamma RI. Human Fc gamma RII is polymorphic, and monocytes interact either strongly or weakly with mouse IgG1. The interaction of low responder monocytes with mouse IgG1 was dramatically increased (to the level exhibited by high responder monocytes) by protease treatment. The effects of proteases on Fc gamma RII were investigated in more detail by using monocytes from which Fc gamma RI was selectively modulated by using immobilized immune complexes. Proteolysis of such modulated monocytes induced an increased interaction with EA-human IgG. Fc gamma RII appears to mediate this interaction. This conclusion is supported by the observation that after proteolysis, the Fc gamma RII-mediated binding of EA-mouse IgG1 becomes susceptible to inhibition by (monomeric) human IgG. To quantify the effect of proteolytic enzymes on Fc gamma RII, we performed binding studies with cell line K562, that expresses only Fc gamma RII. A significant increase in Ka of Fc gamma RII for dimeric human IgG complexes was observed when K562 cells were treated with protease. To elucidate the mechanism of this enhancement of Ka by proteolysis, we performed immunoprecipitation studies. Neither m.w., nor IEF pattern of Fc gamma RII were influenced by proteolysis. Moreover, the expression of Fc gamma RII was not affected by proteolysis as evidenced by immunofluorescence studies and Scatchard analysis, and neither were Fc gamma RI or Fc gamma RIII induced. We conclude that proteolysis increases the affinity of Fc gamma RII for human IgG, and speculate that such a proteolysis-induced change may also occur in vivo, e.g., at inflammatory sites.
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PMID:Proteolysis induces increased binding affinity of the monocyte type II FcR for human IgG. 252 88

The ability of fresh human amnion to bind and internalize horseradish peroxidase-labeled IgG (IgG-HRP) was examined in an in vitro Ussing chamber system. The amnion demonstrated unique cell membrane receptors for the Fc portion of IgG molecules (Fc gamma R). The Fc gamma R exhibit exquisite specificity and affinity for IgG monomers as demonstrated by staining with labeled IgG. Labeled IgA, IgM, F(ab')2 fragments of IgG, aggregated IgG, and antigen-antibody complexes all failed to bind to the amnionic epithelial cells. Binding was only minimally affected by changes in ionic strength or pH when viewed at the light microscopic level. The Fc gamma R are located on both the apical and basal cell membranes. The binding of IgG-HRP to the amnion cell membrane was detectable within 1 min, and internalization of the ligand occurred within 5 min. No binding of IgG-HRP was observed following treatment of the membrane with 0.25% trypsin for 30 min at room temperature. Incubation of the amnion at 4 degrees C or in the presence of colchicine or cytochalasin D prevented internalization of the IgG-HRP. These experiments demonstrate Fc gamma R on human amnionic epithelial cells that both bind and internalize IgG, thus allowing the amnion to be used as a model system for studying IgG transport.
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PMID:Human amnion as a model for IgG transport. 295 76

The properties of protein kinase activity associated with Fc receptor specific for IgG2a (Fc gamma 2aR) of a murine macrophage like cell line, P388D1, were investigated. IgG2a-binding protein isolated from the detergent lysate of P388D1 cells by affinity chromatography on IgG-Sepharose was found to contain four distinct proteins of Mr 50,000, 43,000, 37,000, and 17,000, which could be autophosphorylated upon incubation with [gamma-32P]ATP. The autophosphorylation of Fc gamma 2a receptor complex ceased when exogenous phosphate acceptors (casein or histone) were added in the reaction mixture. Casein was found to be a much better phosphate acceptor than histone in this system, as casein incorporated about 32-fold more 32P than histone did. Phosphorylation of casein catalyzed by Fc gamma 2a receptor complex was dependent on casein concentration (maximum phosphate incorporation being at 0.5 mg/mL), increased with time or temperature, was dependent on the concentration of ATP and Mg2+, and was maximum at pH near 8. Casein phosphorylation was significantly inhibited by a high concentration of Mn2+ (greater than 25 mM) or KCl (greater than 100 mM) or by a small amount of heparin (greater than 10 units/mL) and was enhanced about 2-fold by protamine. Casein kinase activity associated with Fc gamma 2a receptor used ATP as substrate with an apparent Km of 2 microM as well as GTP with an apparent Km of 10 microM. Prior heating (60 degrees C for 15 min) or treatment with protease (trypsin or Pronase) of Fc gamma 2a receptor complex almost totally abolished casein kinase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protein kinase activity associated with Fc gamma 2a receptor of a murine macrophage like cell line, P388D1. 296 64


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