Fibrinogen γ′ chain carboxy terminal peptide selectively inhibits the intrinsic coagulation pathway

Abstract

Summary The minor γA/γ′ isoform of fibrinogen contains a high affinity binding site for thrombin exosite II that is lacking in the major fibrinogen isoform, γA/γA fibrinogen. The biological consequences of γ′ chain binding to thrombin were therefore investigated. Coagulation assays, thrombin activity assays, and a primate thrombosis model were used to characterize the biological effects of the γ′ 410–427 peptide. The γ′ peptide had little effect on thrombin cleavage of the small peptidyl substrate tosyl‐glycyl‐prolyl‐arginine‐4‐nitranilide acetate. However, in vitro assays demonstrated that the γ′ peptide inhibited thrombin cleavage of larger proteinaceous substrates, including fibrinogen and factor VIII. The γ′ peptide inhibited the activated partial thromboplastin time in plasma and showed greater inhibition of activated partial thromboplastin time assays than prothrombin time assays, consistent with the inhibition of factor VIII cleavage. Studies in a baboon thrombosis model showed that the γ′ 410–427 peptide inhibited fibrin‐rich thrombus formation (typical of venous thrombi) and, to a lesser extent, platelet‐rich thrombus formation (typical of arterial thrombi). These results indicate that binding of thrombin exosite II by the γ′ peptide has selective effects on the intrinsic pathway.

Fibrinogen-elongated γ Chain Inhibits Thrombin-induced Platelet Response, Hindering the Interaction with Different Receptors

“…A recent study in a baboon thrombosis model showed indeed that the 410 -427 ␥Ј peptide is able not only to inhibit fibrin-rich thrombus formation, because of the inhibition of the intrinsic coagulation pathway (related to inhibition of FVIII activation by thrombin), but also platelet-rich thrombus formation in the arterial circulation (59). These findings may be also relevant for clinical applications of ssDNA aptamers, like HD22, whose specific target is ABE-II of thrombin (60).…”

The pleiotropic role of the fibrinogen γ′ chain in hemostasis

“…23 Another study using a ␥Ј P410-L427 synthetic peptide found no effects on cleavage of a chromogenic substrate by thrombin, but a reduction in FVIII activation, suggesting selective inhibition of the intrinsic pathway. 31 These data suggest that the ␥Ј chain may act as an inhibitor of the plasma consolidation (intrinsic) pathway for thrombin generation in the solution phase. The authors also demonstrated that this peptide inhibited thrombus formation in a primate thrombosis model.…”

“…The authors also demonstrated that this peptide inhibited thrombus formation in a primate thrombosis model. 31 It has been suggested that allosteric effects of the binding of the ␥Ј chain to exosite II on the thrombin catalytic site may be responsible for the inhibitory activity of ␥A/␥Ј fibrinogen. 30 Recent reports suggest that the ␥Ј chain may also function as a reservoir for active thrombin in the fibrin clot.…”

Differential proteomic analysis of platelets suggested target-related proteins in rabbit platelets treated with Rhizoma Corydalis

“…Fibrinogen consists of three pairs of polypeptide chains (Aa, Bb and c) linked by disulphide bonds, which can bind a IIb b3 receptor resulted in platelet aggregation after platelets being activated (Mustard et al 1978;Marguerie et al 1980). Furthermore, fibrinogen binds through its c chains (i.e., fibrinogen c chain isoform X1, protein spot 47) to growth factors and coagulation factors to perform its key roles in fibrin clot formation, platelet aggregation and wound healing (Farrell 2004;Lovely et al 2007). Peroxiredoxin-6, which can be downregulated in platelet treated with RC, is a family member of peroxiredoxins for antioxidant proteins related to either protection against oxidation or participation in signalling by the reduction of H 2 O 2 (Da Silva- Azevedo et al 2009;Ambruso 2013).…”