Abstract
Proteinase-activated receptor-2 (PAR-2) is a G protein-coupled receptor that is cleaved and activated by trypsin-like enzymes. PAR-2 is highly expressed by small intestinal enterocytes where it is activated by luminal trypsin. The location, mechanism of activation, and biological functions of PAR-2 in the colon, however, are unknown. We localized PAR-2 to the muscularis externa of the rat colon by immunofluorescence. Myocytes in primary culture also expressed PAR-2, assessed by immunofluorescence and RT-PCR. Trypsin, SLIGRL-NH2 (corresponding to the PAR-2 tethered ligand), mast cell tryptase, and a filtrate of degranulated mast cells stimulated a prompt increase in [Ca2+]i in myocytes. The response to tryptase and the mast cell filtrate was inhibited by the tryptase inhibitor BABIM, and abolished by desensitization of PAR-2 with trypsin. PAR-2 activation inhibited the amplitude of rhythmic contractions of strips of rat colon. This response was unaffected by indomethacin, l-NG-nitroarginine methyl ester, a bradykinin B2 receptor antagonist and tetrodotoxin. Thus, PAR-2 is highly expressed by colonic myocytes where it may be cleaved and activated by mast cell tryptase. This may contribute to motility disturbances of the colon during conditions associated with mast cell degranulation.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adrenergic beta-Antagonists / pharmacology
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Animals
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Benzimidazoles / pharmacology
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Bradykinin / analogs & derivatives
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Bradykinin / pharmacology
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Calcium / metabolism
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Cells, Cultured
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Chymases
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Colon / chemistry
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Cyclooxygenase Inhibitors / pharmacology
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Dinoprostone / pharmacology
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Dose-Response Relationship, Drug
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Fluorescent Antibody Technique, Indirect
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Gastrointestinal Motility / drug effects
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In Vitro Techniques
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Indomethacin / pharmacology
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Inflammation Mediators / pharmacology
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Leupeptins / pharmacology
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Mast Cells / enzymology*
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Muscle, Smooth / chemistry
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NG-Nitroarginine Methyl Ester / pharmacology
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Nitroprusside / pharmacology
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Rats
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Receptor, PAR-2
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Receptors, Cell Surface / analysis
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Receptors, Cell Surface / physiology*
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Serine Endopeptidases / metabolism*
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Serine Endopeptidases / pharmacology
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Substance P / pharmacology
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Tetrodotoxin / pharmacology
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Time Factors
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Trypsin / pharmacology
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Tryptases
Substances
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Adrenergic beta-Antagonists
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Benzimidazoles
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Cyclooxygenase Inhibitors
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Inflammation Mediators
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Leupeptins
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Receptor, PAR-2
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Receptors, Cell Surface
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Nitroprusside
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Substance P
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Tetrodotoxin
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bis(5-amidino-2-benzimidazolyl)methane
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icatibant
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Serine Endopeptidases
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chymase 2
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Chymases
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Trypsin
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Tpsab1 protein, rat
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Tpsb2 protein, rat
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Tryptases
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leupeptin
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Dinoprostone
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Bradykinin
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Calcium
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NG-Nitroarginine Methyl Ester
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Indomethacin