title: Prothrombotic skeletal muscle myosin directly enhances prothrombin activation by binding factors Xa and Va.
abstract: To test the hypothesis that skeletal muscle myosins can directly influence blood coagulation and thrombosis, ex vivo studies of the effects of myosin on thrombogenesis in fresh human blood were conducted. Addition of myosin to blood augmented the thrombotic responses of human blood flowing over collagen-coated surfaces (300 s-1shear rate). Perfusion of human blood over myosin-coated surfaces also caused fibrin and platelet deposition, evidencing myosin's thrombogenicity. Myosin markedly enhanced thrombin generation in both platelet-rich plasma and platelet-poor plasma, indicating that myosin promoted thrombin generation in plasma primarily independent of platelets. In purified reaction mixtures composed only of factor Xa, factor Va, prothrombin, and calcium ions, myosin greatly enhanced prothrombinase activity. The Gla domain of factor Xa was not required for myosin's prothrombinase enhancement. When binding of purified clotting factors to immobilized myosin was monitored using biolayer interferometry, factors Xa and Va each showed favorable binding interactions. Factor Va reduced by 100-fold the apparentKdof myosin for factor Xa (Kd∼0.48 nM), primarily by reducing koff, indicating formation of a stable ternary complex of myosin:Xa:Va. In studies to assess possible clinical relevance for this discovery, we found that antimyosin antibodies inhibited thrombin generation in acute trauma patient plasmas more than in control plasmas (P= .0004), implying myosin might contribute to acute trauma coagulopathy. We posit that myosin enhancement of thrombin generation could contribute either to promote hemostasis or to augment thrombosis risk with consequent implications for myosin's possible contributions to pathophysiology in the setting of acute injuries.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Deguchi
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.
authors.forename: Ranjeet K
authors.initials: RK
authors.lastname: Sinha
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Marchese
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.
authors.forename: Zaverio M
authors.initials: ZM
authors.lastname: Ruggeri
authors.affiliation: Biomedical Engineering, School of Medicine and Division of Hematology, Oregon Health and Science University, Portland, OR.
authors.forename: Jevgenia
authors.initials: J
authors.lastname: Zilberman-Rudenko
authors.affiliation: Biomedical Engineering, School of Medicine and Division of Hematology, Oregon Health and Science University, Portland, OR.
authors.forename: Owen J T
authors.initials: OJT
authors.lastname: McCarty
authors.affiliation: Department of Surgery, University of California, San Francisco and San Francisco General Hospital, San Francisco, CA; and.
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Cohen
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.|Division of Hematology, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors.forename: John H
authors.initials: JH
authors.lastname: Griffin
mesh_terms: D000208:Acute Disease; D000818:Animals; D001775:Blood Circulation / Q000187:drug effects; D016022:Case-Control Studies; D015943:Factor Va / Q000378:metabolism*; D015951:Factor Xa / Q000378:metabolism*; D006801:Humans; D055767:Immobilized Proteins / Q000494:pharmacology; D007368:Interferometry; D008954:Models, Biological; D053657:Platelet-Rich Plasma / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011516:Prothrombin / Q000378:metabolism*; D011817:Rabbits; D024744:Skeletal Muscle Myosins / Q000494:pharmacology*; D013927:Thrombosis / Q000378:metabolism / Q000473:pathology*; D014947:Wounds and Injuries / Q000097:blood / Q000473:pathology
chemical_list: D055767:Immobilized Proteins; D015943:Factor Va; D011516:Prothrombin; D015951:Factor Xa; D024744:Skeletal Muscle Myosins