Thrombomodulin
From Wikipedia, the free encyclopedia
Thrombomodulin, CD141 or BDCA-3 is an integral membrane protein expressed on the surface of endothelial cells.
The protein has a molecular weight of 74kDa, and consists of a single chain with 5 distinct domains.
It functions as a cofactor in the thrombin-induced activation of protein C in the anticoagulant pathway by forming a 1:1 stochiometric complex with thrombin. This raises the speed of protein C activation thousandfold. Thrombomodulin-bound thrombin has no procoagulant effect. The TT-complex also inhibits fibrinolysis by cleaving thrombin-activatable fibrinolysis inhibitor (TAFI) into its active form.
The antigen described as BDCA-3 (Dzionek et al., 2000) has turned out to be identical to thrombomodulin (Dzionek et al., 2002). Thus, it was revealed that this molecule also occurs on a very rare (0.02%) subset of human dendritic cells called MDC2. Its function on these cells is unknown at present, but apparently, thrombomodulin has at least one other ligand apart from thrombin, because anticoaglulation is a commonplace function, in contrast to the rarity of MDC2 cells.
[edit] References
- Dzionek, Andrzej; Fuchs,Anja; Schmidt, Petra; Cremer, Sabine; Zysk, Monika; Miltenyi, Stefan; Buck, David W. & Schmitz, Jürgen (2000): BDCA-2, BDCA-3, and BDCA-4: three markers for distinct subsets of dendritic cells in human peripheral blood. Journal of Immuology 165(11): 6037-6046. PDF fulltext
- Dzionek, Andrzej; Inagaki, Yoshimasa; Okawa, Katsuya; Nagafune, Jun; Röck, Jürgen; Sohma, Yoshiaki; Winkels, Gregor; Zysk, Monika; Yamaguchi, Yasunori & Schmitz, Jürgen (2002): Plasmacytoid dendritic cells: from specific surface markers to specific cellular functions, Human Immunology 63(12): 1133-1148. DOI:10.1016/S0198-8859(02)00752-8 (HTML abstract)
