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Protease-activated receptor
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Protease-activated receptors are a subfamily of related G protein-coupled receptors that are activated by cleavage of part of their extracellular domain. They are highly expressed in platelets, but also on endothelial cells, myocytes and neurons.[1]
Classification
There are 4 known protease-activated receptors or PAR's, numbered from one to four. These receptors are members of the seven transmembrane G-protein-coupled receptor superfamily, and are expressed throughout the body.
Activation
PAR's are activated by the action of serine proteases such as thrombin (acts on PAR's 1, 3 and 4) and trypsin (PAR 2). These enzymes cleave the N-terminus of the receptor, which in turn acts as a tethered ligand. In the cleaved state, part of the receptor itself acts as the agonist, causing a physiological response.
Most of the PAR family act through the actions of G-proteins i (cAMP inhibitory), 12/13 (Raf/Ras activation) and q (calcium signalling) to cause cellular actions.
Function
Recent research has implicated these novel receptors in the inflammatory response (including arthritis), muscle growth, and bone cell differentiation and proliferation.
References
External links
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Transmembrane receptor: G protein-coupled receptors |
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| Class A: Rhodopsin like |
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GPR ( 1, 3, 4, 6, 12, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 31, 32, 33, 34, 35, 37, 39, 42, 44, 45, 50, 52, 55, 61, 62, 63, 65, 68, 75, 77, 78, 79, 82, 83, 84, 85, 87, 88, 92, 101, 103, 119, 120, 132, 135, 139, 141, 142, 146, 148, 149, 150, 151, 152, 153, 160, 161, 162, 171, 172, 173, 174, 176, 177, 182)
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Adenosine ( A1, A2a, A2b, A3) • P2Y ( 1, 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14)
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Other
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Acetylcholine ( M1, M2, M3, M4, M5) • Adrenomedullin • Anaphylatoxin ( C3a, C5a) • Angiotensin ( 1, 2) • Apelin • Bile acid • Bombesin ( BRS3, GRPR, NMBR) • Bradykinin ( B1, B2) • Cannabinoid ( CB1, CB2) • Chemokine • Cholecystokinin ( A, B) • Dopamine ( D1, D2, D3, D4, D5) • EBI2 • Endothelin ( A, B) • Estrogen • Formyl peptide ( 1, L1, L2) • Free fatty acid ( 1, 2, 3, 4) • FSH • Galanin ( 1, 2, 3) • Gonadotropin-releasing hormone ( 1, 2) • Ghrelin • Histamine ( H1, H2, H3, H4) • Kisspeptin • Luteinizing hormone/choriogonadotropin • Lysophospholipid ( 1, 2, 3, 4, 5, 6, 7, 8) • MAS ( 1, 1L, D, E, F, G, X1, X2, X3, X4) • Melanocortin ( 1, 2, 3, 4, 5) • MCHR ( 1, 2) • Melatonin ( 1A, 1B) • Motilin • Neuromedin ( B, U ( 1, 2)) • Neurotensin ( 1, 2) • Opioid ( Delta, Kappa, Mu, Nociceptin, but not Sigma) • Olfactory • Opsin ( 3, 4, 5, 1LW, 1MW, 1SW, RGR, RRH) • Orexin ( 1, 2) • Oxytocin • Oxoglutarate • PAF • Prokineticin ( 1, 2) • Prolactin-releasing peptide • Protease-activated ( 1, 2, 3, 4) • Relaxin ( 1, 2, 3, 4) • Somatostatin ( 1, 2, 3, 4, 5) • SREB • Succinate • TAAR ( 1, 2, 3, 5, 6, 8, 9) • Tachykinin ( 1, 2, 3) • Thyrotropin • Thyrotropin-releasing hormone • Urotensin-II • Vasopressin ( 1A, 1B, 2)
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| Class B: Secretin like |
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GPR ( 56, 64, 97, 98, 110, 111, 112, 113, 114, 115, 116, 123, 124, 125, 126, 128, 133, 143, 144, 157)
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Other
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Brain-specific angiogenesis inhibitor ( 1, 2, 3) • Cadherin ( 1, 2, 3) • Calcitonin • CALCRL • CD97 • Corticotropin-releasing hormone ( 1, 2) • EMR ( 1, 2, 3) • Glucagon ( GR, GIPR, GLP1R, GLP2R) • Growth hormone releasing hormone • PACAPR1 • GPR • Latrophilin ( 1, 2, 3, ELTD1) • Parathyroid hormone ( 1, 2) • Secretin • Vasoactive intestinal peptide ( 1, 2)
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Class C: Metabotropic
glutamate / pheromone |
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TAS1R ( 1, 2, 3) • TAS2R ( 1, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50)
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Other
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Calcium-sensing receptor • GABA B ( 1, 2) • Glutamate receptor ( Metabotropic glutamate ( 1, 2, 3, 4, 5, 6, 7, 8)) • GPRC6A • GPR ( 156, 158, 179) • RAIG ( 1, 2, 3, 4)
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| Frizzled / Smoothened |
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