title: Alboserpin, a factor Xa inhibitor from the mosquito vector of yellow fever, binds heparin and membrane phospholipids and exhibits antithrombotic activity.
abstract: The molecular mechanism of factor Xa (FXa) inhibition by Alboserpin, the major salivary gland anticoagulant from the mosquito and yellow fever vector Aedes albopictus, has been characterized. cDNA of Alboserpin predicts a 45-kDa protein that belongs to the serpin family of protease inhibitors. Recombinant Alboserpin displays stoichiometric, competitive, reversible and tight binding to FXa (picomolar range). Binding is highly specific and is not detectable for FX, catalytic site-blocked FXa, thrombin, and 12 other enzymes. Alboserpin displays high affinity binding to heparin (K(D) ~ 20 nM), but no change in FXa inhibition was observed in the presence of the cofactor, implying that bridging mechanisms did not take place. Notably, Alboserpin was also found to interact with phosphatidylcholine and phosphatidylethanolamine but not with phosphatidylserine. Further, annexin V (in the absence of Ca(2+)) or heparin outcompetes Alboserpin for binding to phospholipid vesicles, suggesting a common binding site. Consistent with its activity, Alboserpin blocks prothrombinase activity and increases both prothrombin time and activated partial thromboplastin time in vitro or ex vivo. Furthermore, Alboserpin prevents thrombus formation provoked by ferric chloride injury of the carotid artery and increases bleeding in a dose-dependent manner. Alboserpin emerges as an atypical serpin that targets FXa and displays unique phospholipid specificity. It conceivably uses heparin and phosphatidylcholine/phosphatidylethanolamine as anchors to increase protein localization and effective concentration at sites of injury, cell activation, or inflammation.
authors.affiliation: Section of Vector Biology, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Calvo
authors.forename: Daniella M
authors.initials: DM
authors.lastname: Mizurini
authors.forename: Anderson
authors.initials: A
authors.lastname: Sá-Nunes
authors.forename: José M C
authors.initials: JM
authors.lastname: Ribeiro
authors.forename: John F
authors.initials: JF
authors.lastname: Andersen
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Mans
authors.forename: Robson Q
authors.initials: RQ
authors.lastname: Monteiro
authors.forename: Michail
authors.initials: M
authors.lastname: Kotsyfakis
authors.forename: Ivo M B
authors.initials: IM
authors.lastname: Francischetti
mesh_terms: D000330:Aedes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000821:virology; D000818:Animals; D001777:Blood Coagulation; D015951:Factor Xa / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D065427:Factor Xa Inhibitors; D005343:Fibrinolytic Agents / Q000737:chemistry* / Q000378:metabolism; D006493:Heparin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007303:Insect Vectors / Q000737:chemistry* / Q000378:metabolism / Q000821:virology; D051379:Mice; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010718:Phosphatidylserines / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D015843:Serpins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015004:Yellow Fever
chemical_list: D065427:Factor Xa Inhibitors; D005343:Fibrinolytic Agents; D019476:Insect Proteins; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D015843:Serpins; C483858:phosphatidylethanolamine; D006493:Heparin; D015951:Factor Xa