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 that is stored at low pH in the mast cell secretory granules in complex with heparin proteoglycan. When mast cells are activated, e.g. during allergic responses, the tryptase/heparin complexes are released together with a variety of other preformed inflammatory mediators. Previous crystallization of human beta-tryptase revealed a unique tetrameric structure with all of the active sites facing a central pore that has a limited accessibility both for potential substrates as well as for protease inhibitors. In this study we examined whether human beta-tryptase, in addition, could form active monomers. Incubation of recombinant tetrameric human beta-tryptase at neutral pH and 37 degrees C, followed by gel-filtration analysis using a running buffer containing pig mucosal heparin, led to the formation of enzymically active compounds that were of a size compatible with tryptase monomers in complex with heparin. The monomers were, in contrast to tryptase in the tetrameric form, inhibited by bovine pancreatic trypsin inhibitor. Further, the monomers, but not the tetramers, degraded fibronectin. Formation of active monomers was more pronounced at pH 7.5 than at pH 6.0 and was not detected at room temperature or at high heparin/tryptase ratios. The present findings thus introduce the possibility that human beta-tryptase, after mast cell degranulation and exposure to neutral pH in the tissue, may dissociate into active monomers with properties that are distinct from the tetrameric counterpart. Possibly, some of the biological activities of human tryptase may be attributable to active tryptase in its monomeric rather than tetrameric form.
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PMID:Formation of active monomers from tetrameric human beta-tryptase. 1238 26

There has long been conjecture over the degree to which there may be structural and functional heterogeneity in the tetrameric serine protease tryptase (EC 3.4.21.59), a major mediator of allergic inflammation. We have applied 2D gel electrophoresis to analyze the extent, nature, and variability of this heterogeneity in lysates of mast cells isolated from lung and skin, and in preparations of purified tryptase. Gels were silver stained, or the proteins transferred to nitrocellulose blots and probed with either tryptase-specific monoclonal antibodies or various lectins. Tryptase was the major protein constituent in mast cell lysates, and presented as an array of 9-12 diffuse immunoreactive spots with molecular masses ranging from 29 to 40 kDa, and pI values from 5.1 to 6.3. Although the patterns obtained for lung and skin tryptase were broadly similar, differences were observed between tissues and between individual donors. Lectin binding studies indicated the presence of mono-antennary or bi-antennary complex-type oligosaccharide with varying degrees of sialylation. Deglycosylation with protein-N-glycosidase F (PNGase F) reduced the size of both lung and skin tryptase, while incubation with PNGase F or neuraminidase narrowed the pI range, indicating variable degrees of glycosylation as a major contributor to the size and charge heterogeneity. Comparison of different purified preparations of lung and skin tryptase revealed no significant difference in pH profiles, but differences were seen in reactivity towards a range of chromogenic substrates, with substantial differences in Km, kcat and degree of cooperativity. Mathematical modeling indicated that the variety in kinetics parameters could not result solely from the sum of varying amounts of isoforms obeying Michaelis-Menten kinetics but with different values of Km and kcat. The heterogeneity demonstrated for tryptase in these studies suggests that there are important differences in tryptase function in different tissues.
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PMID:The heterogeneity of mast cell tryptase from human lung and skin. 1260 78

Proteolytic activation of hemagglutinin, an envelope glycoprotein of the influenza virus, by host proteases is essential for infection and proliferation of the virus. However, there is no well-defined, inherent source of host proteases in man or swine, both of which are natural hosts for human influenza viruses. We have recently isolated a 32 kDa protein in a high salt extract from porcine lungs, which possess the hemagglutinin processing activity. In this study, we attempted to purify another hemagglutinin processing enzyme from porcine lung. The purified enzyme, named tryptase TC30, exhibited a molecular mass of about 30 kDa by SDS-PAGE and 28.5 kDa by gel filtration chromatography, suggesting that it is a monomer. Tryptase TC30 cleaved peptide substrates with Arg at the P1 position, and preferentially substrates with the Ser-Ile-Gin-Ser-Arg sequence corresponding to the HA cleavage site sequence of the A/PR/8/34 influenza virus. Among various inhibitors tested, trypsin-type serine protease inhibitors, such as aprotinin, antipain, benzamidine and leupeptin, efficiently inhibited the proteolytic activity of the enzyme. The N-terminal 40 amino acid sequence of tryptase TC30 exhibits more than 60% homology to mast cell tryptases from mice MCP-6 and human tryptase-alpha and -beta. These data indicate that tryptase TC30, the 30 kDa enzyme from porcine lung, is a novel hemagglutinin-cleaving enzyme.
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PMID:A novel influenza A virus activating enzyme from porcine lung: purification and characterization. 1267 14

The mast cell serine protease tryptase has been implicated as a critical mediator of airway hyperresponsiveness in vitro and in vivo. We have previously demonstrated that tryptase promotes hyperresponsiveness in isolated guinea pig bronchi. In this study, we have investigated the potential role of tryptase-mediated activation of proteinase-activated receptor-2 (PAR-2) in promoting airway hyperresponsiveness. Ex vivo exposure of guinea pig bronchi to the PAR-2 agonists H(2)N-Ser-Leu-Ile-Gly-Arg-Leu-CONH(2) (SLIGRL) and t-cinnamoyl-H(2)N-Leu-Ile-Gly-Arg-Leu-O-CONH(2) (t-c-LIGRLO) (0.1-10 microM) induced a concentration-dependent increase of contractile response to histamine. Treatment with 10 microM SLIGRL or t-c LIGRLO for 45 min increased subsequent responsiveness to histamine (0.3mM) by 54+/-3% and 69+/-5%, respectively (P<0.05 vs. control). In contrast, the PAR-1 agonist peptide H(2)N-Ser-Phe-Leu-Leu-Arg-Asn-CONH(2) (SFLLRN) did not promote significant changes in the airway. Effects of the peptides were observed following at least a 30-min preincubation with the tissue. Coincubation with indomethacin or removal of epithelial cells is required for PAR-2-mediated hyperreactivity. The inactive analogue H(2)N-Leu-Ser-Ile-Gly-Arg-Leu-CONH(2) (LISGRL; 10 microM) failed to promote hyperresponsiveness. Neuropeptide antagonists blocked the effect of the PAR-2 agonists. Selective antagonists of NK1 (L-703,606), NK2 (L-659,877), and CGRP (alphaCGRP 8-37) provided additive inhibition of PAR-2-mediated hyperreactivity. Pretreatment of bronchi with capsaicin (0.8 microM) also prevented the effects of SLIGRL. These results demonstrate the potential involvement of tryptase-mediated activation of PAR-2 in promoting airway hyperresponsiveness. These results further demonstrate that the PAR-2-mediated response involves a neurogenic mechanism involving neuropeptide release.
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PMID:Proteinase-activated receptor-2 mediates hyperresponsiveness in isolated guinea pig bronchi. 1290 52

SERPINB6 (PI6) is a member of the intracellular serine protease inhibitors (serpins). Previous studies showed that SERPINB6 is localized mainly in the cytoplasm of endothelial cells, some epithelial cells, monocytes, and neutrophils. In these cells SERPINB6 is thought to prevent cellular damage by scavenging leaking lysosomal proteases. We show here, using novel, well-defined monoclonal antibodies, that SERPINB6 is abundantly expressed by mast cells in all organs and by the human mast cell line HMC-1. Gel filtration experiments revealed that the latter cells contain a high-molecular-weight form of SERPINB6, which consists of sodium dodecyl sulfate (SDS)-stable complexes of this inhibitor with monomeric beta-tryptase. Expression of SERPINB6 by mast cells was compared with those of tryptase and CD117 (c-kit) in biopsies from patients with different forms of mast cell disease. In all cases the lesional mast cells expressed SERPINB6, and, in diffuse cutaneous mastocytosis and mastocytoma, SERPINB6 was expressed by a substantially higher number of mast cells when compared with tryptase. In conclusion, SERPINB6 is abundantly expressed by normal mast cells and by mast cells in mastocytoma lesions. We suggest that in mast cells, SERPINB6 serves to regulate the activity of endogenous beta-tryptase in the cytoplasm.
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PMID:Intracellular serpin SERPINB6 (PI6) is abundantly expressed by human mast cells and forms complexes with beta-tryptase monomers. 1467 Sep 19

Chymase is a chymotrypsin-like serine protease secreted from mast cells. Mammalian chymases are classified into two subgroups (alpha and beta) according to structure and substrate specificity; human chymase is an alpha-chymase. An important action of chymase is the ACE-independent conversion of Ang I to Ang II, but chymase also degrades the extracellular matrix, activates TGF-beta1 and IL-1beta, forms 31-amino acid endothelins and is involved in lipid metabolism. Under physiological conditions, the role of chymase in blood vessels is uncertain. In pathological situations, however, chymase may be important. In animal models of hypertension and atherosclerosis, chymase may be involved in lipid deposition and intimal and smooth muscle hyperplasia, at least in some vessels. In addition, chymase has pro-angiogenic properties. In human diseased blood vessels (e.g. atherosclerotic and aneurysmal aorta; remodeled pulmonary blood vessels), there are increases in chymase-containing mast cells and/or in chymase-dependent conversion of Ang I to Ang II. These findings have raised the possibility that inhibition of chymase may have a role in the therapy of vascular disease. The effects of chymase can theoretically be attenuated either by reducing availability of the enzyme, with a mast cell stabiliser, or alternatively with specific chymase inhibitors. The mast cell stabiliser, tranilast, was shown to be beneficial in animal models of atherosclerosis, where a prevention protocol was used, but was not effective in clinical trials where it was administered after angioplasty. Chymase inhibitors could have the advantage of being effective even if used after injury. Several orally active inhibitors, including SUN-C8257, BCEAB, NK3201 and TEI-E548, are now available. These have yet to be tested in humans, but promising results have been obtained in animal models of atherosclerosis and angiogenesis. It is concluded that orally active inhibitors of chymase may have a place in the treatment of vascular diseases where injury-induced mast cell degranulation contributes to the pathology.
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PMID:Vascular chymase: pathophysiological role and therapeutic potential of inhibition. 1498 62

Mast cells, which are granulocytes found in peripheral tissue, play a central role in inflammatory and immediate allergic reactions. beta-Tryptase is a neutral serine protease and is the most abundant mediator stored in mast cell granules. The release of beta-tryptase from the secretory granules is a characteristic feature of mast cell degranulation. While its biological function has not been fully clarified, mast cell beta-tryptase has an important role in inflammation and serves as a marker of mast cell activation. beta-Tryptase activates the protease activated receptor type 2. It is involved in airway homeostasis, vascular relaxation and contraction, gastrointestinal smooth muscle activity and intestinal transport, and coagulation. Serum mast cell beta-tryptase concentration is increased in anaphylaxis and in other allergic conditions. It is increased in systemic mastocytosis and other haematological conditions. Serum beta-tryptase measurements can be used to distinguish mast cell-dependent reactions from other systemic disturbances such as cardiogenic shock, which can present with similar clinical manifestations. Increased beta-tryptase levels are highly suggestive of an immunologically mediated reaction but may also occur following direct mast cell activation. Patients with increased mast cell beta-tryptase levels must be investigated for an allergic cause. However, patients without increased mast cell tryptase levels should be investigated if the clinical picture suggests severe anaphylaxis.
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PMID:Mast cell tryptase: a review of its physiology and clinical significance. 1520 May 44

Protease-activated receptor 2 (PAR2) is the second member of a new subfamily of G-protein coupled receptors: the protease-activated receptors (PARs). At present, four different PARs have been cloned and all of them share the same basic mechanism of activation. A serine protease cleaves the extended, extracellular N-terminus of the receptor at a specific site within the protein chain to expose an N-terminal tethered ligand domain, which binds to and activates the cleaved receptor. In this manner, trypsin and mast cell beta-tryptase activate PAR2. PARs are single use receptors because proteolytic activation is irreversible and the cleaved receptors are degraded in lysosomes. Thus, PARs play important roles in emergency situations, such as trauma and inflammation. Emerging evidence indicates that PAR2 is involved in the cardiovascular, pulmonary and gastrointestinal systems, where it controls inflammation and nociception. Work with selective agonists and knockout animals suggests a contribution of PAR2 to certain inflammatory diseases. Therefore, selective antagonists or agonists of these receptors may be useful therapeutic agents for the treatment of human diseases.
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PMID:Proteinase-activated receptor-2: physiological and pathophysiological roles. 1531 91

The renin-angiotensin system is a key target for drugs combating cardiovascular disease. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor type-1 (AT1 receptor) blockers are well known. However, angiotensin peptides can be generated through a number of pathways besides the classic system. This review outlines some of these pathways, their relation to the classic system and the likely effect of inhibiting them. Renin is still the key enzyme in angiotensin peptide generation and seems to be the only route to angiotensin I formation in vivo. Renin inhibitors may have some advantages in terms of specificity. Also, by blocking angiotensin I generation, the production of downstream bioactive angiotensin I metabolites should also be blocked. Chymase, a mast cell serine protease, cleaves angiotensin I to produce angiotensin II and may be important at sites of inflammation such as atherosclerotic plaque. Angiotensin-converting enzyme 2 (ACE2), a carboxypeptidase structurally related to ACE but resistant to ACE inhibitors, has a protective effect on cardiac function. Neutral endopeptidase 24.11 breaks down both atrial natriuretic peptide and angiotensin II. Inhibiting it potentiates the action of endogenous atrial peptide but only affects circulating angiotensin II when basal levels are above normal. Dual inhibitors of ACE and endopeptidase 24.11 may be of value where there is both sodium retention and increased angiotensin II. Targeting the renin-angiotensin system by gene therapy or antibody treatment may provide a longer-term treatment for hypertension.
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PMID:Targeting the renin-angiotensin system: what's new? 1563 41

We describe herein the design, synthesis, and in vitro biochemical evaluation of a series of potent, time-dependent inhibitors of the mast cell-derived serine protease tryptase. The inhibitors were readily obtained by attaching various heterocyclic thiols, as well as a basic primary specificity residue P(1), to the 1,2,5-thiadiazolidin-3-one 1,1-dioxide scaffold. The inhibitors were found to be devoid of any inhibitory activity toward a neutral (elastase) or cysteine (papain) protease, however they were also fairly efficient inhibitors of bovine trypsin. The differential inhibition observed with trypsin suggests that enzyme selectivity can be optimized by exploiting differences in the S' subsites of the two enzymes. The results described herein demonstrate the versatility of the heterocyclic scaffold in fashioning mechanism-based inhibitors of neutral, basic, and acidic (chymo)trypsin-like serine proteases.
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PMID:1,2,5-Thiadiazolidin-3-one 1,1-dioxide-based heterocyclic sulfides are potent inhibitors of human tryptase. 1575 3


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