Thromb Haemost 2008; 100(06): 1058-1067
DOI: 10.1160/TH08-05-0307
Blood Coagulation, Fibrinolysis and Cellular Haemostasis
Schattauer GmbH

Multimerin 1 binds factor V and activated factor V with high affinity and inhibits thrombin generation

Samira B. Jeimy
1   Department of Pathology and Molecular Medicine, Health Sciences Center, McMaster University, Hamilton, Ontario, Canada
,
Nola Fuller
1   Department of Pathology and Molecular Medicine, Health Sciences Center, McMaster University, Hamilton, Ontario, Canada
,
Subia Tasneem
1   Department of Pathology and Molecular Medicine, Health Sciences Center, McMaster University, Hamilton, Ontario, Canada
,
Kenneth Segers
2   Cardiovascular Research Institute, Maastricht Department of Biochemistry, Maastricht University, Maastricht, The Netherlands
,
Alan R. Stafford
3   Department of Medicine, McMaster University and Henderson Research Centre, Hamilton, Ontario, Canada
,
Jeffrey I. Weitz
3   Department of Medicine, McMaster University and Henderson Research Centre, Hamilton, Ontario, Canada
,
Rodney M. Camire
4   Department of Pediatrics, Division of Hematology, Children’s Hospital of Philadelphia and University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
,
Gerry A. F. Nicolaes
2   Cardiovascular Research Institute, Maastricht Department of Biochemistry, Maastricht University, Maastricht, The Netherlands
,
Catherine P. M. Hayward
1   Department of Pathology and Molecular Medicine, Health Sciences Center, McMaster University, Hamilton, Ontario, Canada
› Author Affiliations

Financial support: This work was supported by grants from the Canadian Institutes of Health Research (42450) (C.P.M.H.), National Institutes of Health (HL-74124, project 2) (R.M.C), and Dutch Organization for Scientific Research (VIDI grant no. 917–46330) (G.A.F.N.). C. P. M. H. is the recipient of a Career Investigator Award from the Heart and Stroke Foundation of Ontario and a Canada Research Chair in Molecular Hemostasis. S. B. J is the recipient of a Doctoral Research Award from the Canadian Institutes of Health Research.
Further Information

Publication History

Received: 18 May 2008

Accepted after major revision: 02 September 2008

Publication Date:
23 November 2017 (online)

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Summary

Multimerin 1 (MMRN1) is a polymeric, factorV (FV) binding protein that is stored in platelet and endothelial cell secretion granules but is undetectable in normal plasma. In human platelet α-granules, FV is stored complexed to MMRN1, predominantly by noncovalent binding interactions. The FV binding site for MMRN1 is located in the light chain, where it overlaps the C1 and C2 domain membrane binding sites essential for activated FV (FVa) procoagulant function. Surface plasmon resonance (SPR), circular dichroism (CD) and thrombin generation assays were used to study the binding of FV and FVa to MMRN1, and the functional consequences. FV and FVa bound MMRN1 with high affinities (KD:2 and 7 nM, respectively). FV dissociated more slowly from MMRN1 than FVa in SPR experiments, and CD analyses suggested greater conformational changes in mixtures of FV and MMRN1 than in mixtures of FV and MMRN1. SPR analyses indicated that soluble phosphatidylserine (1,2-Dicaproylsn-glycero-3-phospho-L-serine) competitively inhibited both FV-MMRN1 and FVa-MMRN1 binding. Furthermore, exogenous MMRN1 delayed and reduced thrombin generation by plasma and platelets, and it reduced thrombin generation by preformed FVa. Exogenous MMRN1 also delayed FV activation, triggered by adding tissue factor to plasma, or by adding purified thrombin or factor Xa to purified FV. The high affinity binding of FV to MMRN1 may facilitate the costorage of the two proteins in platelet α-granules. As a consequence, MMRN1 release during platelet activation may limit platelet dependent thrombin generation in vivo.