Application of factor VII-Sepharose affinity chromatography in the purification of human tissue factor apoprotein

Expression and kinetics of induced procoagulant activity in bovine pulmonary alveolar macrophages

Leukocytes, especially macrophages, are important cellular mediators of fibrin deposition and removal at tissue sites of inflammation. Pulmonary fibrin deposition is a prominent feature of bovine acute lung injury; therefore, we studied the resting and stimulated procoagulant responses of bovine pulmonary alveolar macrophages (PAM) and peripheral blood neutrophils (PMN). Freshly isolated normal PAM and PMN expressed negligible procoagulant activity. PAM stimulated with endotoxin lipopolysaccharide (LPS), 4 beta-phorbol 12-myristate 13-acetate (PMA) and bovine recombinant interleukin-1 beta (rBIL-1 beta) exhibited protein synthesis- and dose-dependent enhancement of procoagulant activity in 8-h cultures. Bovine recombinant granulocyte macrophage-colony stimulating factor (rBGM-CSF) and recombinant human gamma-interferon (rHIFN-gamma) did not induce procoagulant activity. The kinetics of LPS- and PMA-enhanced PAM procoagulant activity differed: LPS-induced enhancement developed earlier and more rapidly than PMA-induced enhancement. Pasteurella haemolytica LPS was more potent than Escherichia coli LPS in enhancing PAM procoagulant activity, while dexamethasone decreased both baseline and LPS- or PMA-stimulated activity by approximately 50%. PAM procoagulant activity resulted from tissue factor expression. Bovine PMN produced negligible procoagulant activity when stimulated, and are thus unlikely to be major contributors to procoagulant activity in bovine lung. Activity inhibitory to bovine tissue factor was present in both calf and adult sera, and was partly dependent on the presence of factor X for activity. Rapid induction of bovine PAM procoagulant activity by inflammatory mediators, and subsequent resistance to degradation, may thus combine to promote an alveolar microenvironment permissive to fibrin deposition in bovine acute lung injury.

Formation of tissue factor activity following incubation of recombinant human tissue factor apoprotein with plasma lipoproteins

Incubation of recombinant human tissue factor apoprotein (Apo-TF) with human plasma decreased the recalcified clotting time of this plasma in a time-and dose-dependent manner suggesting relipidation of the Apo-TF by plasma lipoproteins. Incubation of Apo-TF with purified preparations of human very low density, low density and high density lipoproteins resulted in tissue factor activity in a clotting assay. The order of effectiveness was VLDL greater than LDL much greater than HDL. Tissue factor activity generated by incubation of a fixed amount of Apo-TF with plasma lipoproteins was lipoprotein concentration-dependent and saturable. The association of Apo-TF with lipoprotein particles was supported by gel filtration studies in which 125I-Apo-TF coeluted with the plasma lipoprotein in the void volume of a Superose 6 column in the presence and absence of calcium ions. In addition, void-volume Apo-TF-lipoprotein fractions exhibited tissue factor activity. These results suggest that the factor VIII-bypassing activity of bovine Apo-TF observed in a canine hemophilic model may be due, in part, to its association with plasma lipoproteins and expression of functional tissue factor activity.

The contributions of Ca2+, phospholipids and tissue-factor apoprotein to the activation of human blood-coagulation factor X by activated factor VII

In the extrinsic pathway of blood coagulation, Factor X is activated by a complex of tissue factor, factor VII(a) and Ca2+ ions. Using purified human coagulation factors and a sensitive spectrophotometric assay for Factor Xa, we could demonstrate activation of Factor X by Factor VIIa in the absence of tissue-factor apoprotein, phospholipids and Ca2+. This finding allowed a kinetic analysis of the contribution of each of the cofactors. Ca2+ stimulated the reaction rate 10-fold at an optimum of 6 mM (Vmax. of 1.1 x 10(-3) min-1) mainly by decreasing the Km of Factor X (to 11.4 microM). In the presence of Ca2+, 25 microM-phospholipid caused a 150-fold decrease of the apparent Km and a 2-fold increase of the apparent Vmax. of the reaction; however, both kinetic parameters increased with increasing phospholipid concentration. Tissue-factor apoprotein contributed to the reaction rate mainly by an increase of the Vmax., in both the presence (40,500-fold) and absence (4900-fold) of phospholipid. The formation of a ternary complex of Factor VIIa with tissue-factor apoprotein and phospholipid was responsible for a 15 million-fold increase in the catalytic efficiency of Factor X activation. The presence of Ca2+ was absolutely required for the stimulatory effects of phospholipid and apoprotein. The data fit a general model in which the Ca2(+)-dependent conformation allows Factor VIIa to bind tissue-factor apoprotein and/or a negatively charged phospholipid surface resulting into a decreased intrinsic Km and an increased Vmax. for the activation of fluid-phase Factor X.

Purification of recombinant human tissue factor

Tissue factor (TF) is a 263 amino acid membrane-bound procoagulant protein that serves as a cofactor for the serine protease factor VII (fVII). Recombinant human TF (rTF) produced in both human kidney 293 cells and Escherichia coli has been immunoaffinity purified by using a TF-specific monoclonal antibody. Recombinant TF produced in 293 cells is glycosylated and migrates on reducing SDS-PAGE with an apparent molecular weight (Mr) of 45K. Some interchain disulfide-bonded rTF dimers are observed under nonreducing conditions. The E. coli produced rTF has a molecular weight of 33K and 35K, with the 33K band missing nine amino acids at the carboxy terminus. Although the E. coli produced rTF does not contain any carbohydrate, it is fully functional in both a chromogenic assay and a one-stage prothrombin time assay. A variant has been constructed wherein the cytoplasmic cysteine (residue 245) has been mutagenized to a serine residue. The amount of disulfide-linked aggregates is dramatically reduced following immunoaffinity purification of this four-cysteine variant (C2455), which is active in the chromogenic and prothrombin time assays.

Purification and characterization of rabbit tissue factor

Anti-human tissue factor IgG column was used to partially purify rabbit tissue factor. The rabbit tissue factor was then further purified on SDS-polyacrylamide gel electrophoresis to prepare an essentially homogeneous rabbit tissue factor. This was used as an antigen to raise a high titer, monospecific, polyclonal antiserum for rabbit tissue factor. Immunostaining of a crude Triton extract of rabbit brain acetone powder and purified tissue factor with the anti-rabbit tissue factor IgG yielded a single major band with an apparent molecular weight of 45 kD, which corresponds to the mobility on SDS-PAGE of purified rabbit tissue factor apoprotein. The anti-rabbit tissue factor IgG was coupled to Affi-Gel-15 and used as an immunoadsorbent column to purify large amounts of rabbit brain tissue factor in a rapid, one-step technique.

Characterization of anti-tissue factor antibody and its use in immunoaffinity purification of human tissue factor

Human brain tissue factor apoprotein was recently purified to homogeneity in this laboratory by affinity chromatography utilizing factor VII bound to immobilized anti-factor VII (Anal Biochem 165, 365-370, 1987). A potent polyclonal anti-tissue factor antibody has now been raised to the purified apoprotein. Immunostaining of purified tissue factor with this polyclonal IgG yielded a single major band with an apparent molecular weight of 47,000, which corresponds to the mobility on SDS-PAGE of tissue factor apoprotein. Immunostaining of a crude Triton extract of brain tissue yielded two additional bands, with apparent molecular weights of 54,000 and 40,000 Da. An anti-tissue factor IgG was coupled to Affi-Gel-15 to prepare an immunoadsorbant column. The two additional proteins in the crude Triton extract recognized by Western blotting did not bind to the column. This permitted its use to develop a simple, efficient technique for purification of human tissue factor apoprotein.

Resolution of monomeric and heterodimeric forms of tissue factor, the high-affinity cellular receptor for factor VII

Tissue factor (TF) is the high affinity cell surface receptor and obligatory cofactor for plasma coagulation factor VII. Purification of TF from human brain and placenta has recently been reported to yield both a monomeric 47 kDa protein as well as a 58 kDa heterodimeric form. In this study, the TF glycoprotein was isolated from human brain by immunoaffinity chromatography using a newly developed monoclonal antibody, TF8-5G9, and was compared to TF isolated by factor VII-affinity chromatography. Except for the greater efficiency of the immunoaffinity method, both methods yielded TF with similar specific activities, and both preparations contained the monomeric and heterodimeric forms of TF. The 58 kDa form was established to be a disulfide-linked heterodimer composed of TF and the alpha chain of hemoglobin. From these results and from studies of immunoprecipitation of TF from cultured fibroblast cells, we conclude that the 47 kDa monomeric form of TF is the naturally occurring cellular form of TF, and that heterodimer formation is a secondary event. The potential significance of the proclivity of TF to form a heterodimer with hemoglobin is discussed.

Tissue factor apoprotein: intracellular transport and expression in shed membrane vesicles

We have studied the synthesis and subcellular distribution of the glycosylated membrane protein tissue factor (TF) in human blood monocytes and the inducible monocyte like cell line, HL-60. Following induction with endotoxin or the phorbol ester, TPA, tissue factor specific activity was measured in intact cells, sonicated cells, isolated plasma membranes and shed vesicles. We have shown that TF is transported over time from the cytoplasm to the plasma membrane and finally to shed membrane vesicles. Optimal transport of TF to the plasma membrane and shedding in membrane vesicles required glycosylation as judged by partial inhibition of this process by the tunicamycin homologues B2 and C2.