title: Identification and functional characterization of a novel F5 mutation (Ala512Val, FVB onn ) associated with activated protein C resistance.
abstract: Essentials Activated protein C (APC) resistance is a prevalent risk factor for venous thrombosis. A novel missense mutation (Ala512Val - FVBonn ) was characterized in vitro and in silico. FVBonn is a new cause of APC resistance and venous thrombosis. FVBonn expresses additionally enhanced procoagulant activity in the absence of APC.
  
  
  
  Background Activated protein C (APC) resistance is a prevalent risk factor for venous thrombosis. This phenotype is most commonly associated with the factor V Arg506Gln mutation (FV Leiden), which impairs the APC-mediated inactivation of both activated FV (FVa) and activated FVIII (FVIIIa). Objectives Here, we report the identification and characterization of a novel FV mutation (Ala512Val, FVBonn ) in six patients with APC resistance and venous thrombosis or recurrent abortions. Methods FVBonn was expressed in a recombinant system and compared with recombinant wild-type (WT) FV and FV Leiden in several functional assays. Results FVBonn conferred APC resistance to FV-depleted plasma, both in the activated partial thromboplastin time (APTT)-based test (APC sensitivity ratio [APCsr] of 1.98 for FVBonn versus 4.31 for WT FV and 1.59 for FV Leiden) and in the thrombin generation-based test (normalized APCsr of 5.41 for FVBonn versus 1.00 for WT FV and 8.99 for FV Leiden). The APC-mediated inactivation of FVaBonn was slower than that of WT FVa (mainly because of delayed cleavage at Arg506), but was greatly stimulated by protein S. The APC cofactor activity of FVBonn in FVIIIa inactivation was ~ 24% lower than that of WT FV. In line with these findings, an in silico analysis showed that the Ala512Val mutation is located in the same loop as the Arg506 APC cleavage site and might hamper its interaction with APC. Moreover, FVBonn was more procoagulant than WT FV and FV Leiden in the absence of APC, because of an increased activation rate and, possibly, an enhanced interaction with activated FX. Conclusions FVBonn induces hypercoagulability via a combination of increased activation/procoagulant activity, decreased susceptibility to APC-mediated inactivation, and slightly reduced APC cofactor activity.
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Pezeshkpoor
authors.affiliation: Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Castoldi
authors.affiliation: Synlab MVZ, Stuttgart, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Mahler
authors.affiliation: Synlab MVZ, Stuttgart, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Hanel
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Müller
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: N S
authors.initials: NS
authors.lastname: Hamedani
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Biswas
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Oldenburg
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Pavlova
mesh_terms: D000026:Abortion, Habitual; D020016:Activated Protein C Resistance / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D000368:Aged; D001777:Blood Coagulation / Q000502:physiology; D001780:Blood Coagulation Tests; D002384:Catalysis; D003029:Coagulants / Q000737:chemistry; D015331:Cohort Studies; D005165:Factor V / Q000235:genetics* / Q000378:metabolism; D015944:Factor VIIIa / Q000737:chemistry; D015943:Factor Va / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D009154:Mutation; D020125:Mutation, Missense; D010314:Partial Thromboplastin Time; D011247:Pregnancy; D011486:Protein C / Q000235:genetics* / Q000378:metabolism; D013917:Thrombin / Q000737:chemistry; D013925:Thromboplastin / Q000378:metabolism; D020246:Venous Thrombosis / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
chemical_list: D003029:Coagulants; D011486:Protein C; C095381:factor V Leiden; C035876:factor V clotting antigen; D015943:Factor Va; D015944:Factor VIIIa; D005165:Factor V; D013925:Thromboplastin; D013917:Thrombin
keywords: APC resistance; FV Leiden; factor V; hypercoagulability; thrombosis