title: The Ser460Pro mutation in recombinant protein S Heerlen does not affect its APC-cofactor and APC-independent anticoagulant activities.
abstract: Protein S is a vitamin K-dependent plasma protein that functions as an APC-cofactor, but also exhibits anticoagulant activity in the absence of APC. The Heerlen polymorphism of protein S is characterized by a Ser460Pro substitution and lacks glycosylation at Asn458. It is associated with decreased protein S levels due to selective deficiency of free protein S Heerlen. To understand the lack of thrombotic complications associated with the protein S Heerlen mutation, we compared recombinant protein S Heerlen, wild type (wt) protein S and plasma-derived protein S. wt-Protein S and protein S Heerlen each bound 1:1 to C4BP with dissociation constants of 0.27 and 0.33 nM, respectively. Both wt-protein S and protein S Heerlen, either free or in complex with C4BP, were equally active as prothrombinase inhibitors in the absence of APC. All three protein S preparations stimulated APC-catalyzed inactivation of normal FVa, FVa Leiden and FVIIIa to the same extent. If extrapolated to plasma, it is not likely that the decreased free protein S levels in carriers of the protein S Heerlen mutation are compensated by an increased anticoagulant activity of protein S Heerlen-C4BP complexes. It is possible that an unrecognized plasma factor selectively enhances the anticoagulant activity of protein S Heerlen. If not, the reduction of free protein S levels in heterozygous protein S Heerlen-carriers combined with (low) normal total protein S levels apparently minimally affects the total anticoagulant activity of protein S (APC-cofactor and APC-independent activity) and hence is not associated with increased risk of venous thrombosis.
authors.affiliation: Department of Biochemistry, Cardiovascular Research Institute Maastricht, University Maastricht, The Netherlands.
authors.forename: Rory R
authors.initials: RR
authors.lastname: Koenen
authors.forename: Lucio
authors.initials: L
authors.lastname: Gomes
authors.forename: Guido
authors.initials: G
authors.lastname: Tans
authors.forename: Jan
authors.initials: J
authors.lastname: Rosing
authors.forename: Tilman M
authors.initials: TM
authors.lastname: Hackeng
mesh_terms: D000925:Anticoagulants; D001779:Blood Coagulation Factors / Q000378:metabolism; D002460:Cell Line; D015935:Complement C4b / Q000378:metabolism; D006801:Humans; D020125:Mutation, Missense; D011486:Protein C / Q000378:metabolism*; D017293:Protein S / Q000235:genetics* / Q000378:metabolism*; D018455:Protein S Deficiency / Q000150:complications / Q000209:etiology / Q000235:genetics*; D011994:Recombinant Proteins; D012306:Risk; D013925:Thromboplastin / Q000037:antagonists & inhibitors; D014162:Transfection; D020246:Venous Thrombosis / Q000209:etiology
chemical_list: D000925:Anticoagulants; D001779:Blood Coagulation Factors; D011486:Protein C; D017293:Protein S; D011994:Recombinant Proteins; C499867:protein S Heerlen; D015935:Complement C4b; D013925:Thromboplastin