Re-evaluation of the role of the protein S-C4b binding protein complex in activated protein C-catalyzed factor Va-inactivation
Författare
Summary, in English
Protein S expresses cofactor activity for activated protein C (APC) by enhancing the APC-catalyzed proteolysis at R-306 in factor Va. It is generally accepted that only free protein S is active and that complex formation with C4b-binding protein (C4BP) inhibits the APC-cofactor activity of protein S. However, the present study shows that protein S-C4BP expresses APC-cofactor activity and stimulates APC-catalyzed proteolysis at R-306 more than 10-fold, but instead inhibits proteolysis at R-506 by APC 3- to 4-fold. Free protein S stimulates APC-catalyzed cleavage at R-306 approximately 20-fold and has no effect on cleavage at R-506. The resulting net effect of protein S-C4BP complex formation on APC-catalyzed factor Va inactivation is a 6- to 8-fold reduction in factor Va inactivation when compared with free protein S, which is not explained by inhibition of APC-cofactor activity of protein S at R306, but by generation of a specific inhibitor for APC-catalyzed proteolysis at R-506 of factor Va. These results are of interest for carriers of the factor V-Leiden mutation (R(506)Q), as protein S-C4BP effectively enhances APC-catalyzed factor Va (R-306) inactivation in plasma containing factor V-Leiden.
Avdelning/ar
Publiceringsår
2008
Språk
Engelska
Sidor
3034-3041
Publikation/Tidskrift/Serie
Blood
Volym
111
Issue
6
Dokumenttyp
Artikel i tidskrift
Förlag
American Society of Hematology
Ämne
- Hematology
Status
Published
Forskningsgrupp
- Clinical Chemistry, Malmö
ISBN/ISSN/Övrigt
- ISSN: 1528-0020