LDL receptor-related protein 1 contributes to the clearance of the activated factor VII-antithrombin complex.
Essentials Factor VIIa is cleared principally as a complex with antithrombin. Enzyme/serpin complexes are preferred ligands for the scavenger-receptor LRP1. Factor VIIa/antithrombin but not factor VIIa alone is a ligand for LRP1. Macrophage-expressed LRP1 contributes to the clearance of factor VIIa/antithrombin.



Background Recent findings point to activated factor VII (FVIIa) being cleared predominantly (± 65% of the injected protein) as part of a complex with the serpin antithrombin. FVIIa-antithrombin complexes are targeted to hepatocytes and liver macrophages. Both cells lines abundantly express LDL receptor-related protein 1 (LRP1), a scavenger receptor mediating the clearance of protease-serpin complexes. Objectives To investigate whether FVIIa-antithrombin is a ligand for LRP1. Methods Binding of FVIIa and pre-formed FVIIa-antithrombin to purified LRP1 Fc-tagged cluster IV (rLRP1-cIV/Fc) and to human and murine macrophages was analyzed. FVIIa clearance was determined in macrophage LRP1 (macLRP1)-deficient mice. Results Solid-phase binding assays showed that FVIIa-antithrombin bound in a specific, dose-dependent and saturable manner to rLRP1-cIV/Fc. Competition experiments with human THP1 macrophages indicated that binding of FVIIa but not of FVIIa-antithrombin was reduced in the presence of annexin-V or anti-tissue factor antibodies, whereas binding of FVIIa-antithrombin but not FVIIa was inhibited by the LRP1-antagonist GST-RAP. Additional experiments revealed binding of both FVIIa and FVIIa-antithrombin to murine control macrophages. In contrast, no binding of FVIIa-antithrombin to macrophages derived from macLRP1-deficient mice could be detected. Clearance of FVIIa-antithrombin but not of active site-blocked FVIIa was delayed 1.5-fold (mean residence time of 3.3 ± 0.1 h versus 2.4 ± 0.2 h) in macLRP1-deficient mice. The circulatory presence of FVIIa was prolonged to a similar extent in macLRP1-deficient mice and in control mice. Conclusions Our data show that FVIIa-antithrombin but not FVIIa is a ligand for LRP1, and that LRP1 contributes to the clearance of FVIIa-antithrombin in vivo.
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
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Fazavana
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
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Muczynski
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.|Department of Biological Hematology, CHU Bicetre, Hôpitaux Universitaires Paris Sud, AP-HP, Paris, France.
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Proulle
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
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Wohner
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
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Christophe
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
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Lenting
Institut National de la Santé et de la Recherche Médicale, UMR_S 1176, Universitaires Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France.
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Denis
D000818:Animals; D000991:Antithrombins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D020134:Catalytic Domain; D002460:Cell Line; D015942:Factor VIIa / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D011485:Protein Binding; D011973:Receptors, LDL / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015843:Serpins / Q000378:metabolism; D013925:Thromboplastin / Q000378:metabolism; D013997:Time Factors; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D000991:Antithrombins; D002352:Carrier Proteins; C475476:LRP1 protein, human; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; D011973:Receptors, LDL; D011994:Recombinant Proteins; D015843:Serpins; D025521:Tumor Suppressor Proteins; D013925:Thromboplastin; D015942:Factor VIIa
LDL receptor-related proteins; antithrombin III; factor VIIa; half-life; protein-protein interaction domains