title: ClfA(221-550), a fibrinogen-binding segment of Staphylococcus aureus clumping factor A, disrupts fibrinogen function.
abstract: Clumping factor A (ClfA) is a surface protein of Staphylococcus aureus bacteria known for its ability to bind the C-terminus of plasma fibrinogen gamma chain, which participates in mediating fibrinogen-platelet interaction and fibrin cross-linking, resulting in thrombus formation. With an aim to develop agents that block fibrinogen gamma chain C-terminus, the fibrinogen-binding segment of ClfA locating at residues 221-550 was produced by recombinant technology and tested for its ability to inhibit platelet functions and fibrin clot formation. Recombinant ClfA(221-550) bound fibrinogen and blocked fibrinogen-platelet interaction, resulting in the inhibition of both ADP- and collagen-induced platelet aggregations. ClfA(221-550) also affected fibrin clot formation, in which factor XIIIa-mediated cross-linking of fibrinogen gamma chains was abrogated by ClfA(221-550) leaving the release of fibrinopeptides A and B from fibrinogen by thrombin unaltered, indicating that ClfA(221-550) interfered with fibrin clot formation without affecting thrombin's catalytic activity. Platelet-mediated clot retraction depends on both platelet-fibrinogen interaction and fibrin clot formation, which makes platelet thrombus less susceptible to fibrinolysis. At the concentration that reduced platelet aggregation by 40%, ClfA(221-550) prevented platelet-mediated clot retraction, whereas the glycoprotein IIb/IIIa antagonist tirofiban needed a higher concentration in inhibiting clot retraction than inhibiting platelet aggregation. By virtue of the multiple effects of ClfA(221-550) on platelet aggregation, fibrin clot formation and platelet-mediated clot retraction, the binding of ClfA(221-550) to fibrinogen merits further investigation for its potential as a new antithrombotic agent.
authors.affiliation: Department of Pharmacology, College of Medicine, Tzu Chi University, Hualien City, Hualien, Taiwan. czliu33@mail.tcu.edu.tw
authors.forename: Chao-Zong
authors.initials: CZ
authors.lastname: Liu
authors.forename: Mei-Hsu
authors.initials: MH
authors.lastname: Shih
authors.forename: Pei-Jane
authors.initials: PJ
authors.lastname: Tsai
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D001777:Blood Coagulation; D001792:Blood Platelets / Q000378:metabolism / Q000382:microbiology*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D003030:Coagulase / Q000737:chemistry / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D026122:Factor XIIIa / Q000737:chemistry; D005337:Fibrin / Q000737:chemistry; D005340:Fibrinogen / Q000737:chemistry*; D005343:Fibrinolytic Agents / Q000494:pharmacology; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry / Q000502:physiology*; D010973:Platelet Adhesiveness; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry; D013211:Staphylococcus aureus / Q000378:metabolism*; D013917:Thrombin / Q000737:chemistry; D013997:Time Factors
chemical_list: D003030:Coagulase; D003432:Cross-Linking Reagents; D005343:Fibrinolytic Agents; D010446:Peptide Fragments; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011994:Recombinant Proteins; D000244:Adenosine Diphosphate; D005337:Fibrin; D005340:Fibrinogen; D026122:Factor XIIIa; D013917:Thrombin; D016650:Fluorescein-5-isothiocyanate