Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The protease-activated family of G protein-coupled receptors includes PAR-1 and PAR-3, which are activated by thrombin, and PAR-2, which is activated by trypsin and tryptase. PAR-2 has recently been shown to be expressed in human endothelial cells. In the present studies, we have examined the expression of PAR-2 in other cells, particularly vascular smooth muscle, and tested whether the receptors are functional. The results show that PAR-2 is present in human aorta and coronary artery smooth muscle cells, as well as in arteries traversing the walls of the small intestine. It was also detected in human keratinocytes, sweat glands, intestinal smooth muscle, and intestinal epithelium, but not at all in myocardial smooth muscle and only inconsistently in intestinal veins and venules. Activation of aortic smooth muscle cells in culture with PAR-2 peptide agonists caused a transient increase in the cytosolic Ca2+ concentration. In contrast, PAR-2 mRNA could not be detected in saphenous vein smooth muscle cells, and the same cells placed in culture showed little, if any, response to the PAR-2 agonist peptides. These observations show that PAR-2 is widely distributed in human vascular smooth muscle, particularly in arteries. However, this is not a universal finding and at least some venous smooth muscle cells, including those in saphenous veins, apparently do not express the receptor in detectable amounts.
 ...
PMID:Differential expression of functional protease-activated receptor-2 (PAR-2) in human vascular smooth muscle cells. 959 43

Protease-activated receptors (PARs) are a family of G protein-coupled receptors activated by a tethered ligand sequence within the amino terminal that are revealed by site-specific proteolysis. The thrombin-sensitive PAR-1 and trypsin-activated PAR-2 mediate endothelium-dependent vascular relaxation in a number of species. Because both thrombin and trypsin-like enzymes have been implicated in coronary artery disease, the purpose of this study was to investigate whether similar receptors are present in human coronary arteries. Thrombin (0.001 to 0.1 U/mL) and trypsin (0.001 to 1 U/mL) caused concentration- and endothelium-dependent relaxations of human coronary artery ring segments suspended in organ chambers for isometric tension recording and contracted with the thromboxane A2 mimetic U46619. These relaxations were dependent on the catalytic activity of each enzyme and were inhibited by the NO synthase inhibitor NG-nitro-L-arginine (100 micromol/L) and the NO scavenger oxyhemoglobin (20 micromol/L). The synthetic PAR-1 tethered ligand sequence SFLLRN-NH2 (0.01 to 10 micromol/L) also caused endothelium-dependent relaxation of U46619-contracted human coronary arteries; however, the equivalent PAR-2 ligand SLIGKV-NH2 caused almost no relaxation. In addition, desensitization to either thrombin or trypsin resulted in cross-desensitization to the other enzyme but had only a minimal affect on the response to SFLLRN-NH2. Therefore, we conclude that human coronary artery endothelial cells possess a PAR-1-like receptor that is potently activated by thrombin, trypsin, and SFLLRN-NH2 to cause NO-mediated vascular relaxation. Once cleaved, this receptor is recycled in a truncated form, able to respond to exogenous application of only its tethered ligand sequence, suggesting the presence of another endogenous activator possibly acting independently of receptor cleavage.
 ...
PMID:Atypical protease-activated receptor mediates endothelium-dependent relaxation of human coronary arteries. 964 27

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.
 ...
PMID:Reaction of mast cell proteases tryptase and chymase with protease activated receptors (PARs) on keratinocytes and fibroblasts. 964 24

Although serine proteases are usually considered to act principally as degradative enzymes, certain proteases are signaling molecules that specifically regulate cells by cleaving and triggering members of a new family of proteinase-activated receptors (PARs). There are three members of this family, PAR-1 and PAR-3, which are receptors for thrombin, and PAR-2, a receptor for trypsin and mast cell tryptase. Proteases cleave within the extracellular NH2-terminus of their receptors to expose a new NH2-terminus. Specific residues within this tethered ligand domain interact with extracellular domains of the cleaved receptor, resulting in activation. In common with many G protein-coupled receptors, PARs couple to multiple G proteins and thereby activate many parallel mechanisms of signal transduction. PARs are expressed in multiple tissues by a wide variety of cells, where they are involved in several pathophysiological processes, including growth and development, mitogenesis, and inflammation. Because the cleaved receptor is physically coupled to its agonist, efficient mechanisms exist to terminate signaling and prevent uncontrolled stimulation. These include cleavage of the tethered ligand, receptor phosphorylation and uncoupling from G proteins, and endocytosis and lysosomal degradation of activated receptors.
 ...
PMID:Proteinase-activated receptors: novel mechanisms of signaling by serine proteases. 969 85

Protease-activated receptors (PARs) are receptors which require proteolytic cleavage to be self-activated by newly exposed N-terminal 'tethered ligands', and hence serve as sensors for protelytic enzymes. While both the thrombin receptor (PAR-1) and PAR-2 (activated by tryptic enzymes) have been shown to mediate endothelium-dependent vasorelaxation, only PAR-1 has been shown to cause direct vascular smooth muscle contraction. In this study, we report that trypsin and the PAR-2 selective peptide ligand SLIGRL-NH2 not only caused endothelium-dependent relaxation of mouse renal arteries but also direct smooth muscle contraction if endothelial nitric oxide synthase was inhibited or if the endothelium was removed.
 ...
PMID:Endothelium-dependent and -independent responses to protease-activated receptor-2 (PAR-2) activation in mouse isolated renal arteries. 983 89

Proteinase-activated receptor-2 (PAR-2) is a G protein-coupled receptor that is cleaved by trypsin within the NH2-terminus, exposing a tethered ligand that binds and activates the receptor. We examined the secretory effects of trypsin, mediated through PAR-2, on well-differentiated nontransformed dog pancreatic duct epithelial cells (PDEC). Trypsin and activating peptide (AP or SLIGRL-NH2, corresponding to the PAR-2 tethered ligand) stimulated both an 125I- efflux inhibited by Ca2+-activated Cl- channel inhibitors and a 86Rb+ efflux inhibited by a Ca2+-activated K+ channel inhibitor. The reverse peptide (LRGILS-NH2) and inhibited trypsin were inactive. Thrombin had no effect, suggesting absence of PAR-1, PAR-3, or PAR-4. In Ussing chambers, trypsin and AP stimulated a short-circuit current from the basolateral, but not apical, surface of PDEC monolayers. In monolayers permeabilized basolaterally or apically with nystatin, AP activated apical Cl- and basolateral K+ conductances. PAR-2 agonists increased [Ca2+]i in PDEC, and the calcium chelator BAPTA inhibited the secretory effects of AP. PAR-2 expression on dog pancreatic ducts and PDEC was verified by immunofluorescence. Thus, trypsin interacts with basolateral PAR-2 to increase [Ca2+]i and activate ion channels in PDEC. In pancreatitis, when trypsinogen is prematurely activated, PAR-2-mediated ductal secretion may promote clearance of toxins and debris.
 ...
PMID:Trypsin activates pancreatic duct epithelial cell ion channels through proteinase-activated receptor-2. 991 38

A second protease-activated receptor (PAR-2) that could be activated by trypsin or more physiologically by mast cell tryptase has been recently cloned. Both the structure and activation mechanism of PAR-2 was similar to the functional thrombin receptor (PAR-1). Although many effects of the coagulation protease thrombin on the vascular endothelium could be attributed to PAR-1 activation, very little is known about the physiological and pathophysiological role of PAR-2. We investigated whether stimulation of PAR-2 on endothelial cells induced two cellular responses that play a central role in primary and secondary haemostasis: the release of high molecular weight von Willebrand factor (hmw-VWF) from Weibel-Palade bodies and the de novo synthesis of tissue factor (TF) mRNA and protein. Human umbilical vein endothelial cells (HUVEC) were incubated with agonists for PAR-2 at 37 degrees C. Both trypsin and SLIGKV increased TF mRNA and activity and induced the release of hmw-VWF due to elevated levels of cytosolic Ca2+. Trypsin (10 nm) induced a 6-fold increase of TF mRNA and reduced time until fibrin clot formation to 37%, indicating trebling of the cell surface located TF activity. Stimulation of HUVEC with the PAR-2 agonist peptide SLIGKV induced a dose-dependent increase of TF mRNA up to 6 times and TF activity up to 3 times. Release of hmw-VWF was achieved both after incubation of HUVEC with trypsin and SLIGKV and was directly depending on intracellular Ca2+ mobilization. To make results comparable to the functional thrombin receptor, homologous experiments were carried out using the PAR-1 agonists thrombin and SFLLRN.
 ...
PMID:Endothelial protease-activated receptor-2 induces tissue factor expression and von Willebrand factor release. 1023 35

1. Proteases regulate cells by cleaving proteinase-activated receptors (PARs). Thrombin and trypsin cleave PAR-1 and PAR-2 on neurons and astrocytes of the brain to regulate morphology, growth and survival. We hypothesized that thrombin and mast cell tryptase, which are generated and released during trauma and inflammation, regulate enteric neurons by cleaving PAR-1 and PAR-2. 2. We detected immunoreactive PAR-1 and PAR-2 in > 60 % of neurons from the myenteric plexus of guinea-pig small intestine in primary culture. A large proportion of neurons that expressed substance P, vasoactive intestinal peptide or nitric oxide synthase also expressed PAR-1 and PAR-2. We confirmed expression of PAR-1 and PAR-2 in the myenteric plexus by RT-PCR using primers based on sequences of cloned guinea-pig receptors. 3. Thrombin, trypsin, tryptase, a filtrate from degranulated mast cells, and peptides corresponding to the tethered ligand domains of PAR-1 and PAR-2 increased [Ca2+]i in > 50 % of cultured myenteric neurons. Approximately 60 % of neurons that responded to PAR-1 agonists responded to PAR-2 agonists, and > 90 % of PAR-1 and PAR-2 responsive neurons responded to ATP. 4. These results indicate that a large proportion of myenteric neurons that express excitatory and inhibitory neurotransmitters and purinoceptors also express PAR-1 and PAR-2. Thrombin and tryptase may excite myenteric neurons during trauma and inflammation when prothrombin is activated and mast cells degranulate. This novel action of serine proteases probably contributes to abnormal neurotransmission and motility in the inflamed intestine.
 ...
PMID:Thrombin and mast cell tryptase regulate guinea-pig myenteric neurons through proteinase-activated receptors-1 and -2. 1035 15

1. This study investigates, whether in addition to the thrombin receptor (PAR-1), the proteinase-activated receptor-2 (PAR-2) is present in vascular smooth muscle cells (SMC) and mediates mitogenesis. PAR-2 is activated by low concentrations of trypsin and the synthetic peptide SLIGRL. 2. Stimulation of bovine coronary artery SMC by trypsin (2 nM) caused a 3 fold increase in DNLA-synthesis. A similar effect was observed with 10 nM thrombin. Trypsin-induced mitogenesis was inhibited by soybean trypsin inhibitor, indicating that the proteolytic activity of the enzyme was required for its mitogenic effect. 3. The specific PAR-2-activating peptide SLIGRL or the PAR1-activating peptide SFFLRN did not elicit mitogenesis. 4. When the SMC were exposed to SLIGRL (40 nM), a homologous desensitization of cytosolic Ca2+ mobilization was found after subsequent stimulation with trypsin (40 nM) but not thrombin (15 nM). 5. Trypsin (2 nM) as well as SLIGRL (100 microm) activated the nuclear factor KB (NFkappaB) with a maximum response 2 h after stimulation of the SMC. This suggests that both agonists acted via a common receptor, PAR-2. Maximum activation of NFkappaB by thrombin (10 nM) was detected after 4-5 h. 6. These data suggest that PAR-2 is present in coronary SMC and mediates a mitogenic response. Activation of NFkappaB via either PAR-1 or PAR-2 does not predict mitogenesis.
 ...
PMID:Evidence for proteinase-activated receptor-2 (PAR-2)-mediated mitogenesis in coronary artery smooth muscle cells. 1037 15

1. Protease-activated receptors (PARs) are activated by an irreversible proteolytic mechanism which renders cleaved receptors unresponsive to subsequent challenges with activating enzymes. Non-specific proteolysis of PARs downstream of the activation site also prevents subsequent enzymic activation. Therefore, we investigated the effects of non-activating amino-terminal proteolysis with the bacterial protease thermolysin on PAR-mediated relaxation of porcine coronary artery ring preparations contracted with the thromboxane A2 mimetic U46619 (1-10 nM). 2. Treatment of contracted artery ring segments with thermolysin (0.01-1 u ml-1, 20 min) caused no response, but abolished endothelium-dependent relaxations induced by the enzymic activators of PAR-1, and PAR-2, thrombin (0.01-0.3 u ml-1) and trypsin (0.003-0.1 u ml-1) respectively. The same treatment, however, did not affect similar responses to the proteolysis-independent PAR-1 and PAR-2 activating peptides, SFLLRN-NH2 and SLIGRL-NH2 respectively (0.1-10 microM). 3. The inhibition of responsiveness to trypsin after thermolysin treatment recovered in a time-dependent manner, with maximal recovery (77.3 +/- 8.0% of time controls) occurring 150 min after thermolysin treatment. No recovery of responsiveness to thrombin after thermolysin treatment was observed within this time, however, the thrombin response returned to control levels after 20 h. 4. The recovery of responsiveness to trypsin was inhibited by the translation inhibitor cycloheximide (100 microM; 17.3 +/- 4.7%) and the protein trafficking inhibitor brefeldin A (10 microM; 12.1 +/- 4.8%) but was unaffected by the transcription inhibitor actinomycin D (2 microM; 65.1 +/- 3.6%), which did, however, abolish upregulation of B1-kinin receptors in this preparation. 5. In conclusion, our findings indicate that activation-independent amino-terminal proteolysis of PARs stimulates selective recovery of endothelial cell PAR-2 responsiveness, which appears to be regulated by translation. Such a novel mechanism for the maintenance of responsiveness to enzymic PAR-2 activators may imply that these receptors play important roles in vascular homeostasis.
 ...
PMID:Protease-activated receptor-2 turnover stimulated independently of receptor activation in porcine coronary endothelial cells. 1040 51


1 2 3 4 5 6 7 8 9 10 Next >>