Pathophysiologic roles of the fibrinogen gamma chain

Purpose of review: Fibrinogen binds through its γ chains to cell surface receptors, growth factors, and coagulation factors to perform its key roles in fibrin clot formation, platelet aggregation, and wound healing. However, these binding interactions can also contribute to pathophysiologic processes, including inflammation and thrombosis. This review summarizes the latest findings on the role of the fibrinogen γ chain in these processes, and illustrates the potential for therapeutic intervention. Recent findings: Novel γ chain epitopes that bind platelet integrin α, _IIbβ₃ and leukocyte integrin α _Mβ₂ have been characterized, leading to the revision of former dogma regarding the processes of platelet aggregation, clot retraction, inflammation, and thrombosis. A series of studies has shown that the γ chain serves as a depot for fibroblast growth factor-2 (FGF-2), which is likely to play an important role in wound healing. Inhibition of γ chain function with the monoclonal antibody 7E9 has been shown to interfere with multiple fibrinogen activities, including factor XIIIa crosslinking, platelet adhesion, and platelet-mediated clot retraction. The role of the enigmatic variant fibrinogen γ′ chain has also become clearer. Studies have shown that γ′ chain binding to thrombin and factor XIII results in clots that are mechanically stiffer and resistant to fibrinolysis, which may explain the association between γA/γ′ fibrinogen levels and cardiovascular disease. Summary: The identification of new interactions with γ chains has revealed novel targets for the treatment of inflammation and thrombosis. In addition, several exciting studies have shown new functions for the variant γ′ chain that may contribute to cardiovascular disease.