| First Author | Liang Y | Year | 2015 |
| Journal | Blood | Volume | 126 |
| Issue | 7 | Pages | 905-14 |
| PubMed ID | 26045608 | Mgi Jnum | J:225913 |
| Mgi Id | MGI:5694900 | Doi | 10.1182/blood-2015-01-621292 |
| Citation | Liang Y, et al. (2015) Cartilage oligomeric matrix protein is a natural inhibitor of thrombin. Blood 126(7):905-14 |
| abstractText | Thrombin is an effector enzyme for hemostasis and thrombosis; however, endogenous regulators of thrombin remain elusive. Cartilage oligomeric matrix protein (COMP), a matricellular protein also known as thrombospondin-5, is essential for maintaining vascular homeostasis. Here, we asked whether COMP is involved in the process of blood coagulation. COMP deficiency shortened tail-bleeding and clotting time and accelerated ferric-chloride-induced thrombosis in mice. The absence of COMP had no effect on platelet count. In contrast, COMP specifically inhibited thrombin-induced platelet aggregation, activation, and retraction and the thrombin-mediated cleavage of fibrinogen. Furthermore, surface plasmon resonance analysis revealed direct thrombin-COMP binding (KD = 1.38 +/- 0.24 muM). In particular, blockage of thrombin exosites with compounds specific for exosite I (hirudin and HD1 aptamer) or exosite II (heparin and HD22 aptamer) impaired the COMP-thrombin interaction, indicating a 2-site binding mechanism. Additionally, epidermal growth factor-like repeats (amino acids 84-261) were identified as a COMP binding site for thrombin. Moreover, COMP was expressed in and secreted by platelets. Using bone marrow transplantation and platelet transfusion to create chimeric mice, platelet-derived but not vessel-wall-derived COMP was demonstrated to inhibit coagulation. Taken together, COMP is an endogenous thrombin inhibitor and negative regulator of hemostasis and thrombosis. |
