Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tryptase is a serine protease secreted by mast cells that is able to activate other cells. In the present studies we have tested whether these responses could be mediated by thrombin receptors or PAR-2, two G-protein-coupled receptors that are activated by proteolysis. When added to a peptide corresponding to the N terminus of PAR-2, tryptase cleaved the peptide at the activating site, but at higher concentrations it also cleaved downstream, as did trypsin, a known activator of PAR-2. Thrombin, factor Xa, plasmin, urokinase, plasma kallikrein, and tissue kallikrein had no effect. Tryptase also cleaved the analogous thrombin receptor peptide at the activating site but less efficiently. When added to COS-1 cells expressing either receptor, tryptase stimulated phosphoinositide hydrolysis. With PAR-2, this response was half-maximal at 1 nM tryptase and could be inhibited by the tryptase inhibitor, APC366, or by antibodies to tryptase and PAR-2. When added to human endothelial cells, which normally express PAR-2 and thrombin receptors, or keratinocytes, which express only PAR-2, tryptase caused an increase in cytosolic Ca2+. However, when added to platelets or CHRF-288 cells, which express thrombin receptors but not PAR-2, tryptase caused neither aggregation nor increased Ca2+. These results show that 1) tryptase has the potential to activate both PAR-2 and thrombin receptors; 2) for PAR-2, this potential is realized, although cleavage at secondary sites may limit activation, particularly at higher tryptase concentrations; and 3) in contrast, although tryptase clearly activates thrombin receptors in COS-1 cells, it does not appear to cleave endogenous thrombin receptors in platelets or CHRF-288 cells. These distinctions correlate with the observed differences in the rate of cleavage of the PAR-2 and thrombin receptor peptides by tryptase. Tryptase is the first protease other than trypsin that has been shown to activate human PAR-2. Its presence within mast cell granules places it in tissues where PAR-2 is expressed but trypsin is unlikely to reach.
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PMID:Interactions of mast cell tryptase with thrombin receptors and PAR-2. 902 Jan 12

Human mast cell precursors arise in the bone marrow and circulate to different tissue microenvironments, where they develop distinct phenotypes that may be characterized by differential expression of the serine protease, chymase. The growth and development of mast cells is stimulated by mast cell growth factor, which is also known as kit ligand because its obligate receptor is KIT, the protein product of the c-KIT proto-oncogene. The in vivo influence of the KIT-kit ligand axis on the phenotype of human mast cells has not been determined. We used immunohistochemistry to detect in situ expression of tryptase and chymase by mast cells of a patient with urticaria pigmentosa and aggressive systemic mastocytosis, whose pathologic mast cells are clonally derived and chronically stimulated by KIT because they all contain the same point mutation causing constitutive activation of KIT. Mast cells in both spleen and skin expressed tryptase, but only in the skin did a majority of mast cells express chymase. We conclude that chronic stimulation of the KIT-kit ligand axis does not irrevocably commit mast cells to a chymase-positive or chymase-negative phenotype. These findings suggest that factors other than kit ligand predominate in determining mast cell phenotype.
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PMID:Chronically KIT-stimulated clonally-derived human mast cells show heterogeneity in different tissue microenvironments. 945 20

Serine proteases are the most abundant granule constituents of several major hematopoietic cell lineages. Due to their high abundance and their strict tissue specificity they have become important phenotypic cell markers used for studies of various aspects of hematopietic cell development. Using a polymerase chain reaction (PCR)-based strategy for the isolation of trypsin-related serine proteases, we were able to isolate cDNAs for two of the major neutrophil and monocyte serine proteases in the mouse, cathepsin G and mouse protease 3 (myeloblastin). The internal PCR fragments were used as probes to screen a mouse mast cell cDNA library and a cDNA library originating from a mouse monocytic cell line (WEHI-274.1). Full-length cDNAs for mouse cathepsin G and proteinase 3 were isolated and their complete sequences were determined. Northern blot analysis revealed expression of cathepsin G in immature cells of the monocyte macrophage lineage but also in the connective tissue mast cell line MTC. Proteinase 3 was expressed in several cell lines of myelo-monocytic origin and in one B-cell line, but not in any of the other cell lines tested. The isolation of cDNAs for mouse cathepsin G and mouse proteinase 3, together with the previous characterization of the gene for mouse N-elastase, and the entire or partial amino acid sequences for porcine azurocidine, equine N-elastase and proteinase 3, rat, dog, and rabbit cathepsin Gs in evolutionary relatively distantly related mammalian species, indicates that these four members of the serine protease family have been maintained for more than 100 million years of mammalian evolution. This latter finding indicates a strong evolutionary pressure to maintain specific immune functions associated with these neutrophil and monocyte proteases. All amino acid positions of major importance for the cleavage site selection have also been fully conserved between mouse and human proteinase 3 and a few minor changes have occurred between mouse and human cathepsin G.
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PMID:Characterization of cDNA clones encoding mouse proteinase 3 (myeloblastine) and cathepsin G. 921 43

The proteinase-activated receptor-2 (PAR-2) is the second member of a putative larger class of proteolytically activated receptors that mediate cell activation events by receptor cleavage or synthetic peptidomimetics corresponding to the newly generated N-terminus. To further study the previously identified mitogenic effects of PAR-2, we used the interleukin-3 (IL-3)-dependent murine lymphoid cell line, BaF3, for generation of stable cell lines expressing PAR-2 (BaF3/PAR-2) or the noncleavable PAR-2 mutant PAR-2(Arg36 --> Ala36). Only BaF3 cells expressing either wild-type or mutated receptor exhibited mitogenic responses when grown in IL-3-deficient media supplemented with PAR-2 activating peptide (SLIGRL, PAR39-44). This effect was dose dependent with an EC50 of approximately 80 micromol/L, sustained at 24, 48, and 72 hours, and was also demonstrable using thrombin receptor peptide TR42-47. Because tryptase shares approximately 70% homology with trypsin (previously shown to activate PAR-2), we studied recombinantly expressed forms of alpha- and beta-tryptases as candidate protease agonists for PAR-2. Hydrolytic activity of the chromogenic substrate tosyl-glycyl-prolyl-argly-4-nitroanilide acetate was present as a sharp peak at Mr approximately 130, confirming the presence of secretable and functionally active homotetrameric alpha- and beta-tryptases in transfected COS-1 cells. Dose-dependent proliferative responses were evident using either secreted form of tryptase with maximal responses seen at approximately 3 pmol/L (0.1 U/L). Receptor proteolysis was necessary and sufficient for mitogenesis because active site-blocked tryptase failed to induce this response, and proliferative responses were abrogated in BaF3 cells expressing PAR-2(Arg36 --> Ala36). These results specifically identify both forms of mast cell tryptases as serine protease agonists for PAR-2 and have implications for elucidating molecular mechanisms regulating cellular activation events mediated by proteases generated during inflammatory, fibrinolytic, or hemostatic-regulated pathways.
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PMID:Mitogenic responses mediated through the proteinase-activated receptor-2 are induced by expressed forms of mast cell alpha- or beta-tryptases. 935 58

The growth of ovine and caprine mast cells in bone marrow cultures has been achieved using recombinant ovine interleukin-3 (rOvIL-3) and recombinant ovine stem cell factor (rOvSCF). After approximately 2-3 weeks' growth in optimal concentrations of either rOvIL-3 alone or a combination of rOvIL-3 and rOvSCF, the majority of the cells produced in bone marrow culture from both species were mast cells. The significant increase in the total numbers of cells and survival times of the cultures when both cytokines were present compared to either alone, indicated synergy between rOvIL-3 and rOvSCF on mast cell growth. Ovine and caprine cells cultured in rOvIL-3 alone produced a four-fold increase in cell numbers compared with medium only controls. The resulting cultures contained up to 52% mast cells by day 18 and had a lifespan of 3-4 weeks. In contrast, cells from both species grown in both rOvIL-3 and rOvSCF produced up to six times more cells than the equivalent rOvIL-3 stimulated cultures, contained up to 69% mast cells by day 21 and could be maintained for at least 6 weeks. Ovine cells grown in rOvIL-3 alone or rOvIL-3 and rOvSCF contained significantly more aryl-sulfatase and serine protease but similar amounts of beta-hexosaminidase compared with caprine cells during the second week of culture. There were no significant differences in the granule-associated mediator content of cells from either individual species grown in rOvIL-3 alone compared with those grown in rOvIL-3 and rOvSCF during the first 21 days of culture.
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PMID:The effects of recombinant ovine interleukin-3 and recombinant ovine stem cell factor on the growth and mediator expression of caprine and ovine bone marrow-derived mast cells. 953 70

Using a recently developed PCR-based strategy, a cDNA encoding a novel mouse mast cell (MC) serine protease (MMCP-8) was isolated and characterized. The MMCP-8 mRNA contains an open reading frame of 247 amino acids (aa), divided into a signal sequence of 18 aa followed by a 2-aa activation peptide (Gly-Glu) and a mature protease of 227 aa. The mature protease has an M(r) of 25072, excluding post-translational modifications, a net positive charge of +12 and six potential N-glycosylation sites. MMCP-8 showed a high degree of homology with mouse granzyme B in the critical regions for determining substrate cleavage specificity, indicating that MMCP-8, similar to granzyme B, preferentially cleaves after Asp residues. A comparative analysis of the aa sequence of MMCP-8 with other hematopoietic serine proteases shows that it is more closely related to cathepsin G and T cell granzymes than to the MC chymases. We therefore conclude that MMCP-8 belongs to a novel subfamily of mouse MC proteases distinct from both the classical chymases and tryptases. Southern blot analysis of BALB/c genomic DNA indicated that only one MMCP-8 gene (or MMCP-8 like gene) is present in the mouse genome. Northern blot analysis of rodent hematopoietic cell lines revealed high levels of MMCP-8 mRNA in a mouse connective tissue MC-like tumor line. However, MMCP-8 mRNA could not be detected in mouse liver, intestine, lung or ears, indicating very low expression in normal tissues. Analysis of the expression of different MMCP in the tissues of Schistosoma mansoni-infected BALB/c mice showed a strong increase in MMCP-8 levels in the lungs but not in the intestines of infected animals, suggesting the presence of a novel subpopulation of MC in the lungs that expressed MMCP-8, either alone or in combination with MMCP-5 and carboxypeptidase A. The dramatic increase in MMCP-1 and MMCP-2 levels but not of MMCP-8 in the intestines of parasitized animals also shows that MMCP-8 is not expressed in mucosal MC in the mouse. This latter is in clear contrast to what has been observed in the rat where the MMCP-8 homologues, RMCP-8, -9 and -10, can be considered as true mucosal MC proteases.
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PMID:Characterization of mouse mast cell protease-8, the first member of a novel subfamily of mouse mast cell serine proteases, distinct from both the classical chymases and tryptases. 954 98

One mechanism of killing by cytotoxic lymphocytes involves the exocytosis of specialized granules. The released granules contain perforin, which assembles into pores in the membranes of cells targeted for death. Serine proteases termed granzymes are present in the cytotoxic granules and include several chymases (with chymotrypsin-like specificity of cleavage). One chymase is selectively reactive with an inhibitor, Biotinyl-Aca-Aca-Phe-Leu-PheP(OPh)2, that blocks perforin lysis. We report the purification and characterization of this chymase, lymphocyte chymase I, from rat natural killer cell (RNK)-16 granules. Lymphocyte chymase I is 30 kDa with a pH 7.5 to 9 optimum and primary substrate preference for tryptophan, a preference distinct from rat mast cell chymases. This chymase also reacts with other selective serine protease inhibitors that block perforin pore formation. It elutes by Cu2+-immobilized metal affinity chromatography with other granzymes and has the N-terminal protein sequence conserved among granzymes. Chymase I reduces pore formation when preincubated with perforin at 37 degrees C. In contrast, addition of the chymase without preincubation had little effect on lysis. It should be noted that the perforin preparation contained sufficient residual chymase activity to support lysis. Thus, the reduction of lysis may represent an effect of excess prolytic chymase I or a means to limit perforin lysis of bystander cells. In contrast, other chymases and granzyme K were without effect when added to perforin during similar preincubation. Identification of the natural substrate of chymase I will help resolve how it regulates perforin-mediated pore formation.
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PMID:Purification and characterization of lymphocyte chymase I, a granzyme implicated in perforin-mediated lysis. 959 Feb 47

The enzymatic pathways for local angiotensin II (Ang II) formation in the heart have been studied both in vivo and in vitro, but the results of these experiments have been discrepant. Thus, the experiments in vivo with intact hearts, both in humans and in animal models, have unequivocally demonstrated that the major Ang II-forming enzyme is angiotensin-converting enzyme (ACE). In contrast, the experiments in vitro with both human or animal heart preparations, have unequivocally demonstrated that the major Ang II-forming enzyme is chymase, a mast cell-derived chymotrypsin-like serine protease. The in vitro approach, however, seems to involve several pitfalls, which tend to overestimate the contribution of chymase as compared to that of ACE. It seems evident that in vivo the chymase-mediated Ang II formation is subjected to local inhibition, a fact that has been overlooked in most of the studies performed in vitro. Accordingly, human chymase, even in its natural form as a protease-proteoglycan complex, is highly sensitive to the protease inhibitors naturally present in the interstitial fluid (IF). We found that if human heart tissue preparations are incubated in vitro in the presence of IF, the chymase-mediated Ang II formation is almost totally suppressed. As the heart interstitium is constantly bathed by IF with its protease inhibitors in concentrations sufficiently high to ensure efficient inhibition of this enzyme, the protease inhibitor-mediated suppression of chymase should also be effective in vivo. Thus, the local production of Ang II in the human heart appears to be regulated by ACE rather than by chymase.
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PMID:Angiotensin II formation in the human heart: an ACE or non-ACE-mediated pathway? 980 Aug 78

Tryptase, a serine protease, is the major protein component in mast cells. In an animal model of asthma, tryptase has been established as an important mediator of inflammation and late airway responses induced by antigen challenge. Human tryptase is notable for its tetrameric structure, requirement of heparin for stability, and resistance to endogenous inhibitors. Human protryptase was expressed as a recombinant protein in Pichia pastoris. The recombinant protein consisted of two forms of protryptase, one containing the entire propeptide and the other containing only the Val-Gly dipeptide at its amino terminus. Isolation of active recombinant tryptase required a two column purification protocol and included a heparin- and dipeptidyl peptidase I-dependent activation step. Purified recombinant tryptase migrated as a tetramer on a gel filtration column and displayed kinetic parameters identical to those of a native tryptase obtained from HMC-1 cells, a human mast cell line. Recombinant and HMC-1 tryptase exhibited comparable sensitivities to an array of protein and low-molecular-weight inhibitors, including one that is highly specific for tryptase (APC-1167). Similarly, the recombinant enzyme cleaved both alpha- and beta-chains of fibrinogen to generate fibrinogen fragments indistinguishable from those generated by HMC-1-derived tryptase. Thus, recombinant tryptase expressed in P. pastoris displays physical and enzymatic properties essentially identical to the native enzyme. This system provides a cost-effective and easy to manipulate expression system that will enable the functional characterization of this unique enzyme.
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PMID:Expression and characterization of recombinant mast cell tryptase. 1009 84

Our prior work shows that cultured BR cells derived from dog mastocytomas secrete the 92-kDa proenzyme form of gelatinase B. We provided a possible link between mast cell activation and metalloproteinase-mediated matrix degradation by demonstrating that alpha-chymase, a serine protease released from secretory granules by degranulating mast cells, converts progelatinase B to an enzymatically active form. The current work shows that these cells also secrete gelatinase A. Furthermore, gelatinases A and B both colocalize to alpha-chymase-expressing cells of canine airway, suggesting that normal mast cells are a source of gelatinases in the lung. In BR cells, gelatinase B and alpha-chymase expression are regulated, whereas gelatinase A expression is constitutive. Progelatinase B mRNA and enzyme expression are strongly induced by the critical mast cell growth factor, kit ligand, which is produced by fibroblasts and other stromal cells. Induction of progelatinase B is blocked by U-73122, Ro31-8220, and thapsigargin, implicating phospholipase C, protein kinase C, and Ca2+, respectively, in the kit ligand effect. The profibrotic cytokine TGF-beta virtually abolishes the gelatinase B mRNA signal and also attenuates kit ligand-mediated induction of gelatinase B expression, suggesting that an excess of TGF-beta in inflamed or injured tissues may alter mast cell expression of gelatinase B, which is implicated in extracellular matrix degradation, angiogenesis, and apoptosis. In summary, these data provide the first evidence that normal mast cells express gelatinases A and B and suggest pathways by which their regulated expression by mast cells can influence matrix remodeling and fibrosis.
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PMID:Mast cell expression of gelatinases A and B is regulated by kit ligand and TGF-beta. 1022 34


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