Ability of Polyphosphate and Nucleic Acids to Trigger Blood Clotting: Some Observations and Caveats.

Polyphosphate plays several roles in coagulation and inflammation, while extracellular DNA and RNA are implicated in thrombosis and as disease biomarkers. We sought to compare the procoagulant activities of polyphosphate versus DNA or RNA isolated from mammalian cells. In a recent study, we found that much of the procoagulant activity of DNA isolated from mammalian cells using Qiagen kits resisted digestion with nuclease or polyphosphatase, and even resisted boiling in acid.

Multiplexed silicon photonic sensor arrays enable facile characterization of coagulation protein binding to nanodiscs with variable lipid content.

Interactions of soluble proteins with the cell membrane are critical within the blood coagulation cascade. Of particular interest are the interactions of γ-carboxyglutamic acid-rich domain-containing clotting proteins with lipids. Variability among conventional analytical methods presents challenges for comparing clotting protein-lipid interactions.

Polyphosphate and RNA Differentially Modulate the Contact Pathway of Blood Clotting.

The contact pathway of the plasma clotting cascade is dispensable for normal hemostasis, but contributes to thrombosis and serves as a bridge between inflammation and coagulation. This pathway is triggered upon exposure of plasma to certain anionic polymers and artificial surfaces. Recently, extracellular nucleic acids and inorganic polyphosphate (polyP) have been implicated as being important (patho)physiologically relevant activators of this pathway.

High-Resolution NMR Studies of Human Tissue Factor.

In normal hemostasis, the blood clotting cascade is initiated when factor VIIa (fVIIa, other clotting factors are named similarly) binds to the integral membrane protein, human tissue factor (TF). The TF/fVIIa complex in turn activates fX and fIX, eventually concluding with clot formation. Several X-ray crystal structures of the soluble extracellular domain of TF (sTF) exist; however, these structures are missing electron density in functionally relevant regions of the protein.

Structure-Function Relationship of the Interaction between Tissue Factor and Factor VIIa.

Interactions between tissue factor and factor VIIa are the primary initiators of coagulation in hemostasis and certain thrombotic diseases. Tissue factor, an integral membrane protein expressed extensively outside of the vasculature, is the regulatory protein cofactor for coagulation factor VIIa. Factor VIIa, a trypsin-like serine protease homologous with other blood coagulation proteases, is weakly active when free in solution and must bind its membrane-bound cofactor for physiologically relevant activity.

Tissue Factor Residues That Modulate Magnesium-Dependent Rate Enhancements of the Tissue Factor/Factor VIIa Complex.

The blood coagulation cascade is initiated when the cell-surface complex of factor VIIa (FVIIa, a trypsin-like serine protease) and tissue factor (TF, an integral membrane protein) proteolytically activates factor X (FX). Both FVIIa and FX bind to membranes via their γ-carboxyglutamate-rich domains (GLA domains). GLA domains contain seven to nine bound Ca(2+) ions that are critical for their folding and function, and most biochemical studies of blood clotting have employed supraphysiologic Ca(2+) concentrations to ensure saturation of these domains with bound Ca(2+).