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

Protease activated receptors (PARs) compose a family of G protein signal transduction receptors activated by proteolysis. In this study, the susceptibility of PARs expressed on human keratinocytes and dermal fibroblasts to the human mast cell proteases tryptase and chymase was evaluated. PAR activation was measured by monitoring cytosolic [Ca2+] in cells loaded with the fluorescent Ca2+ probe Fura-2. Tryptase produced transient cytosolic Ca2+ mobilization in keratinocytes, but not in fibroblasts. Ca2+ mobilization in keratinocytes required enzymatically active tryptase, demonstrated desensitization, and was blocked by pretreatment of cells with the PAR-2 peptide agonist SLIGKV, trypsin, or the phospholipase inhibitor U73122. Heparin, a GAG that binds to tryptase, stabilizing its functional form, also inhibited tryptase-induced Ca2+ mobilization. The maximal response elicited by tryptase was smaller than that observed upon treatment of keratinocytes with trypsin, a known activator of PAR-2, and keratinocytes made refractory to tryptase by pretreatment with the protease remained responsive to trypsin. Pretreatment of keratinocytes with thrombin, an activator of PAR-1 and -3 (thrombin receptors), had no detectable effect on the tryptase or trypsin responses. These data suggest that in keratinocytes tryptase may be activating a subpopulation of PAR-2 receptors. Treatment of keratinocytes or fibroblasts with human chymase did not produce Ca2+ mobilization, nor did it affect Ca2+ mobilization produced by trypsin. However, chymase pretreatment of fibroblasts rapidly inhibited the ability of these cells to respond to thrombin. Inhibition was dependent on chymase enzymatic activity and was not significantly affected by the presence of heparin. This finding is consistent with studies indicating that PAR-1 may be susceptible to proteases with chymotrypsin-like specificity. These results suggest that the proteases tryptase and chymase secreted from mast cells in skin may affect the behavior of surrounding cells by the hydrolysis of PARs expressed by these cells.
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PMID:Reaction of mast cell proteases tryptase and chymase with protease activated receptors (PARs) on keratinocytes and fibroblasts. 964 24

The present study examined the effect of intraplantar (i.pl.) administration of a selective agonist of protease-activated receptor (PAR)-2, SLIGRL-NH2(PP6-NH2), on vascular permeability in rat hindpaw. PP6-NH2, administered i.pl. at 10-100 nmol per paw, enhanced vascular permeability and caused oedema formation in rat hindpaw. SLIGRL (PP6-OH) and trypsin, by i.pl. administration, also elicited an increase in vascular permeability, although i.pl. administration of the mixture of constituent amino acids of PP6-OH at an equivalent dose did not. The PP6-NH2-induced increase in vascular permeability was abolished by repeated pretreatment with compound 48/80 to deplete bioactive amines in mast cells. These findings suggest that the activation of PAR-2 induces acute inflammation, at least partially, via mast cell degranulation in rat hindpaw.
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PMID:Increased vascular permeability by a specific agonist of protease-activated receptor-2 in rat hindpaw. 980 21

Activation of protease-activated receptor (PAR)-1 or PAR-2 elicits inflammation most probably via mast cell degranulation in vivo. The present study aimed at characterizing PARs in rat peritoneal mast cells (PMC). Messenger RNA for PAR-1, but not for PAR-2, was detected in PMC. Thrombin, the PAR-1 agonist SFLLR-NH2 or the PAR-2 agonist SLIGRL-NH2 failed to induce histamine release from PMC. Surprisingly, the PAR-2-inactive control peptide LSIGRL-NH2 triggered histamine release from PMC. Thus, PAR-1, but not PAR-2, are expressed in PMC, whereas neither PAR-1 nor PAR-2 are considered to be involved in degranulation of PMC. LSIGRL-NH2 does not appear to be appropriate as a control peptide for PAR-2 in inflammation studies.
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PMID:Characterization of protease-activated receptors in rat peritoneal mast cells. 1087 93

Protease-activated receptors (PARs) belong to a family of G-coupled seven transmembrane receptors that are activated by a proteolytic cleavage of their N-termini. Recent studies suggest the involvement of protease-activated receptors-1 and -2 (PAR-1, PAR-2) activators in mast cell degranulation in various physiological and pathophysiological processes in inflammatory responses. Although PAR-1 and PAR-2 activating proteases, thrombin and tryptase, have been associated with mast cell activation, PAR-1 and PAR-2 have not been localized within these cells. We describe here the localization of PAR-1 and PAR-2 in mast cells from various normal human tissues using immunohistochemical and double immunofluorescence techniques. The presence of these receptors on the membrane may explain the actions of accessible extracellular thrombin and tryptase for mast cell activation. In addition to the membrane labeling, these receptors are also localized on the membrane of the intracellular tryptase-positive granules, which may function to sustain further mast cell degranulation upon exocytosis. The localization of these two receptors in mast cells suggests a novel mechanism for controlling mast cell activation through regulation of PAR-1 and PAR-2.
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PMID:Localization of protease-activated receptors-1 and -2 in human mast cells: indications for an amplified mast cell degranulation cascade. 1094 11

Proteinase-activated receptors (PARs) are activated by proteolytic removal of a short amino terminal peptide, thus exposing a new amino terminus that functions as a tethered ligand that activates the receptor. With the aim to identify and study potential activators of PAR-2 we have developed a new method to measure proteolytic cleavage of PARs. PAR-2 was tagged with the insulin C-peptide that upon receptor cleavage is released and quantified using an ELISA. The modified receptor, shown to be functional in mouse 3T3 cells, was expressed in an insect cell line and the ability of different proteinases to cleave PAR-2 was studied. Two different mast cell tryptases cleaved PAR-2 in a concentration dependent manner, but were much less potent than pancreatic trypsin and trypsin-2 isolated from a carcinoma cell line. Pancreatic trypsin and trypsin-2 were almost equally effective at cleaving PAR-2 suggesting that extrapancreatic trypsins are potential in vivo activators of PAR-2.
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PMID:Extrapancreatic trypsin-2 cleaves proteinase-activated receptor-2. 1094 45

Tryptase, the major mast cell product, is considered to play an important role in airway inflammation and hyperresponsiveness. Tryptase produces different, sometimes opposite, effects on airway responsiveness (bronchoprotection and/or airway contraction). This study was designed to examine the effect of human lung tryptase and activation of protease-activated receptor (PAR)-2 by synthetic activated peptide (AP) SLIGKV-NH(2) on Ca(2+) signaling in human airway smooth muscle (HASM) cells. Immunocytochemistry revealed that PAR-2 was expressed by HASM cells. Tryptase (7.5--30 mU/ml) induced a concentration-dependent transient relative rise in cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) that reached 207 +/- 32 nM (n = 10) measured by indo 1 spectrofluorometry. The protease inhibitors leupeptin or benzamidine (100 microM) abolished tryptase-induced [Ca(2+)](i) increase. Activation of PAR-2 by AP (1-100 microM) also induced a concentration-dependent transient rise in [Ca(2+)](i), whereas the reverse peptide produced no effect. There was a homologous desensitization of the [Ca(2+)](i) response on repeated stimulation with tryptase or AP. U-73122, a specific phospholipase C (PLC) antagonist, xestospongin, an inositol trisphosphate (IP(3))-receptor antagonist, or thapsigargin, a sarcoplamic Ca(2+)-ATPase inhibitor, abolished tryptase-induced [Ca(2+)](i) response, whereas Ca(2+) removal, in the additional presence of EGTA, had no effect. Calphostin C, a protein kinase C inhibitor, increased PAR-2 [Ca(2+)](i) response. Our results indicate that tryptase activates a [Ca(2+)](i) response, which appears as PAR-2 mediated in HASM cells. Signal transduction implicates the intracellular Ca(2+) store via PLC activation and thus via the IP(3) pathway. This study provides evidence that tryptase, which is increasingly recognized as an important mediator in airway inflammation and hyperresponsiveness, is also a potent direct agonist at the site of airway smooth muscle.
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PMID:Selected contribution: tryptase-induced PAR-2-mediated Ca(2+) signaling in human airway smooth muscle cells. 1145 17

Dose-dependent release of beta-hexoaminidase induced with thrombin was shown to be mediated by the PAR-1. This was further confirmed by means of agonist, antagonist and PAR desensitization. Acceleration of the mast cell mediator secretion by the Xa factor and PAR-2 agonist, was revealed. An increase in the mast cell release induced by thrombin and TRAP-6 was shown in the acute peritonitis model.
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PMID:[The role of PAR family receptors in activation of mast cells in the norm and in acute inflammation in rats]. 1181 85

Because thrombin-induced inflammation is partially mast cell-dependent and involves proteinase-activated receptors (PARs), we hypothesized that mast cells express PAR and can be stimulated with PAR-activating peptides (PAR-AP). We demonstrated that rat peritoneal mast cells expressed PAR-1 and PAR-2 mRNA, and that PAR-2AP (tc-LIGRLO-NH(2), 1 microm) induced 64.2 +/- 4.4% specific beta-hexosaminidase release from peritoneal mast cells, whereas another PAR-2AP (SLIGRL-NH(2), 10 microM), trypsin (40 U/ml), and mast cell tryptase (1.5 microg/ml) did not. PAR-1AP (ApfFRChaCitY-NH(2), 10 microM) (Cit) induced 11.7 +/- 3.7% specific beta-hexosaminidase release, whereas another PAR-1AP (TFLLR-NH(2), 40 microM) and human thrombin (10 U/ml) did not. PAR-AP, tc-LIGRLO-NH(2), and Cit increased the free intracellular Ca(2+) concentration, whereas trypsin, tryptase, thrombin, and other PAR-APs did not. Desensitization of Ca(2+) flux with different agonists suggests that although tc-LIGRLO-NH(2), Cit, and compound 48/80 have similar mechanisms of action, tc-LIGRLO-NH(2) also activates mast cells by a mechanism distinct from that of 48/80. Using benzalkonium chloride, which antagonizes the actions of 48/80 by competing for the same G(i) protein, we determined that benzalkonium chloride suppressed tc-LIGRLO-NH(2)-mediated (0.1 microM) beta-hexosaminidase release by 62%. Moreover, removal of sialic acid from peritoneal mast cells, using neuraminidase (2 U/ml), inhibited Cit- (10 microM, 52%) and tc-LIGRLO-NH(2) (0.5 microM, 29%)-mediated beta-hexosaminidase release. Thus, tc-LIGRLO-NH(2) and Cit have at least partially similar mechanisms of action as 48/80. PAR-AP may therefore activate mast cells via multiple mechanisms that are distinct from those of classical PAR-1 and PAR-2. The responsiveness of mast cells to PAR-AP via a non-PAR-1/non-PAR-2 mechanism complicates the interpretation of in vivo studies using these peptides.
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PMID:Proteinase-activated receptor (PAR)-1 and -2 agonists induce mediator release from mast cells by pathways distinct from PAR-1 and PAR-2. 1213 Jul 3

Although tryptase released from mast cells might play a key role in the pathogenesis of ulcerative colitis (UC), the role of protease-activated receptor 2 (PAR2), tryptase receptor, remains unclear in the pathogenesis of this disease. The expressions of PAR2 and tumor necrosis factor (TNF) alpha in nine UC tissues and nine normal tissues were examined by immunohistochemistry. TNF-alpha levels secreted from human leukemic mast cell line (HMC-1) after the treatment of PAR2 agonists were also measured by enzyme-linked immunosorbent assay. The PAR2 and TNF-alpha proteins were more significantly detectable in UC tissues than in normal tissues. Furthermore, 65.2% of PAR2+ cells and 66.4% of TNF-alpha+ cells in UC tissues were tryptase-positive cells. In other words, 60.6% and 46.3% of tryptase-positive cells in UC tissues were PAR2+ cells and TNF-alpha+ cells, respectively. A chi2 analysis showed correlation (p < 0.007) between PAR2 and TNF-alpha in tryptase-positive mast cells. Moreover, PAR2 agonists significantly induced the TNF-alpha secretion from HMC-1. These results indicate that the activation of the mast cells through PAR2 may be involved in the pathogenesis of UC.
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PMID:Expression of protease-activated receptor 2 in ulcerative colitis. 1290 45


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