title: Incorporation of vitronectin into fibrin clots. Evidence for a binding interaction between vitronectin and gamma A/gamma' fibrinogen.
abstract: Vitronectin is an abundant plasma protein that regulates coagulation, fibrinolysis, complement activation, and cell adhesion. Recently, we demonstrated that plasma vitronectin inhibits fibrinolysis by mediating the interaction of type 1 plasminogen activator inhibitor with fibrin (Podor, T. J., Peterson, C. B., Lawrence, D. A., Stefansson, S., Shaughnessy, S. G., Foulon, D. M., Butcher, M., and Weitz, J. I. (2000) J. Biol. Chem. 275, 19788-19794). The current studies were undertaken to further examine the interactions between vitronectin and fibrin(ogen). Comparison of vitronectin levels in plasma with those in serum indicates that approximately 20% of plasma vitronectin is incorporated into the clot. When the time course of biotinylated-vitronectin incorporation into clots formed from (125)I-fibrinogen is monitored, vitronectin incorporation into the clot parallels that of fibrinogen in the absence or presence of activated factor XIII. Vitronectin binds specifically to fibrin matrices with an estimated K(d) of approximately 0.6 microm. Additional vitronectin subunits are assembled on fibrin-bound vitronectin multimers through self-association. Confocal microscopy of fibrin clots reveals the globular vitronectin aggregates anchored at intervals along the fibrin fibrils. This periodicity raised the possibility that vitronectin interacts with the gamma A/gamma' variant of fibrin(ogen) that represents about 10% of total fibrinogen. In support of this concept, the vitronectin which contaminates fibrinogen preparations co-purifies with the gamma A/gamma' fibrinogen fraction, and clots formed from gamma A/gamma' fibrinogen preferentially bind vitronectin. These studies reveal that vitronectin associates with fibrin during coagulation, and may thereby modulate hemostasis and inflammation.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University and the Hamilton Civic Hospitals Research Centre, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada. podort@mcmaster.ca
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Podor
authors.forename: Stephanie
authors.initials: S
authors.lastname: Campbell
authors.forename: Paul
authors.initials: P
authors.lastname: Chindemi
authors.forename: Denise M
authors.initials: DM
authors.lastname: Foulon
authors.forename: David H
authors.initials: DH
authors.lastname: Farrell
authors.forename: Philip D
authors.initials: PD
authors.lastname: Walton
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Weitz
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Peterson
mesh_terms: D019921:Biotinylation; D001792:Blood Platelets / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005337:Fibrin / Q000737:chemistry* / Q000378:metabolism; D005340:Fibrinogen / Q000737:chemistry*; D005353:Fibronectins / Q000737:chemistry; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D018613:Microscopy, Confocal; D011485:Protein Binding; D013997:Time Factors; D019096:Vitronectin / Q000097:blood / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D005353:Fibronectins; D019096:Vitronectin; D005337:Fibrin; D005340:Fibrinogen