title: Role of the thrombin receptor in development and evidence for a second receptor.
abstract: Thrombin, a coagulation protease generated at sites of vascular injury, activates platelets, endothelial cells, leukocytes and mesenchymal cells. A G-protein-coupled receptor that is proteolytically activated by thrombin is a target for drug development aimed at blocking thrombosis, inflammation and proliferation. Here we show that although disruption of the thrombin receptor (tr) gene in mice causes about half of the tr-/- embryos to die at embryonic day 9-10, half survive to become grossly normal adult mice with no bleeding diathesis. Strikingly, tr-/- platelets respond strongly to thrombin, whereas tr-/- fibroblasts lose their ability to respond to thrombin. We conclude that the thrombin receptor plays an unexpected role in embryonic development, suggesting a possible new function for the 'coagulation' proteases themselves. Moreover, a second platelet thrombin receptor exists, and different thrombin receptors have tissue-specific roles. This may allow development of therapeutics that will selectively block thrombin's different cellular actions.
authors.affiliation: Cardiovascular Research Institute, University of California, San Francisco, 94143-0524, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Connolly
authors.forename: H
authors.initials: H
authors.lastname: Ishihara
authors.forename: M L
authors.initials: ML
authors.lastname: Kahn
authors.forename: R V
authors.initials: RV
authors.lastname: Farese
authors.forename: S R
authors.initials: SR
authors.lastname: Coughlin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001760:Bleeding Time; D001792:Blood Platelets / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D005314:Embryonic and Fetal Development / Q000235:genetics / Q000502:physiology*; D005260:Female; D005313:Fetal Death / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism; D018390:Gene Targeting; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010974:Platelet Aggregation; D018179:Receptors, Thrombin / Q000235:genetics / Q000502:physiology*; D013917:Thrombin / Q000378:metabolism
chemical_list: D018179:Receptors, Thrombin; D000255:Adenosine Triphosphate; D013917:Thrombin