Table 1

 Characteristics of the four members of the protease activated receptor (PAR) family: PAR1, PAR2, PAR3, and PAR4.

PAR1PAR2PAR3PAR4
*Each capital letter in this row represents one amino acid according to the amino acid letter code.
Activating proteasesThrombin, trypsin, plasmin, cathepsin G, granzyme A, factors Xa and VIIa, gingipainTrypsin, mast cell Tryptase, trypsin-2, trypsin VI, tissue factor, matriptase/membrane-type serine protease I, factors Xa and VIIa, gingipain, acrosin, dust mite proteasesThrombin, trypsin, factor XaThrombin, trypsin, cathepsin G, factors Xa and VIIa, gingipain, trypsin VI
Selective peptidic agonists*TFLLR, ApfFRChaCitY, TFRID (xenopus)SLIGRL, SLIGKV, trans-cynnamoyl-LIGRLO, 2-furoyl-LIGRLOGYPGKF, GYPGFK, GYPGQV, AYPGKF
AntagonistsRWJ-56110, RWJ-58259, SCH-79797, SCH-73754, FR-171113, BMS-200261Transcinnamoyl-YPGKF, palmitoyl-SGRRYGHALR
Location in the GI tractEnterocytes, myenteric neurones, submucosal neurones, fibroblasts, mast cells, smooth muscle, endothelium, human colon cancer epithelium, immune cellsEnterocytes, myenteric neurones, submucosal neurones, fibroblasts, mast cells, smooth muscle, endothelium, human colon cancer epithelium, pancreatic duct epithelium, pancreatic acinar cells, immune cellsDetected in stomach and small intestine in unidentified cell typesEnterocytes, submucosa, enteric neurones, endothelium, immune cells
Known effects in the GI tractIncreased permeability, apoptosis, ion secretion, prostaglandin release, proliferation, and cell motility, smooth muscle contraction/relaxation, inflammationIon secretion, prostaglandin and eicosanoid release, neuropeptide release, neuronal hyperexcitability, amylase secretion, ion channel activation, inflammation, visceral hypersensitivity, motor functionsMotor functions (contraction of longitudinal muscle)