title: Factor XII Contact Activation.
abstract: Contact activation is the surface-induced conversion of factor XII (FXII) zymogen to the serine protease FXIIa. Blood-circulating FXII binds to negatively charged surfaces and this contact to surfaces triggers a conformational change in the zymogen inducing autoactivation. Several surfaces that have the capacity for initiating FXII contact activation have been identified, including misfolded protein aggregates, collagen, nucleic acids, and platelet and microbial polyphosphate. Activated FXII initiates the proinflammatory kallikrein-kinin system and the intrinsic coagulation pathway, leading to formation of bradykinin and thrombin, respectively. FXII contact activation is well characterized in vitro and provides the mechanistic basis for the diagnostic clotting assay, activated partial thromboplastin time. However, only in the past decade has the critical role of FXII contact activation in pathological thrombosis been appreciated. While defective FXII contact activation provides thromboprotection, excess activation underlies the swelling disorder hereditary angioedema type III. This review provides an overview of the molecular basis of FXII contact activation and FXII contact activation-associated disease states.
authors.affiliation: Clinical Chemistry, Department of Molecular Medicine and Surgery, Karolinska Institutet and University Hospital, Stockholm, Sweden.|Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Clément
authors.initials: C
authors.lastname: Naudin
authors.affiliation: Clinical Chemistry, Department of Molecular Medicine and Surgery, Karolinska Institutet and University Hospital, Stockholm, Sweden.|Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Burillo
authors.affiliation: Department of General and Interventional Cardiology, University Heart Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Blankenberg
authors.affiliation: Clinical Chemistry, Department of Molecular Medicine and Surgery, Karolinska Institutet and University Hospital, Stockholm, Sweden.|Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Lynn
authors.initials: L
authors.lastname: Butler
authors.affiliation: Clinical Chemistry, Department of Molecular Medicine and Surgery, Karolinska Institutet and University Hospital, Stockholm, Sweden.|Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Renné
mesh_terms: D000818:Animals; D001777:Blood Coagulation; D001920:Bradykinin / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D015956:Factor XIIa / Q000235:genetics / Q000378:metabolism*; D056828:Hereditary Angioedema Type III / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013917:Thrombin / Q000235:genetics / Q000378:metabolism*
chemical_list: D015956:Factor XIIa; D013917:Thrombin; D001920:Bradykinin