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Interactions of factor XIII with fibrin as substrate and cofactor.

Factor XIIIa (a2') is a homodimeric transglutaminase that is formed via limited alpha-thrombin-catalyzed proteolysis of the platelet (a2) or plasma (a2b2) factor XIII zymogen in a reaction that results in proteolytic removal of a 37-aminoacyl residue peptide from the N-terminus of the a chains and exposure of the active-site thiol group in the resulting a' chains of factor XIIIa. In this study, we characterized interactions of factor XIII and factor XIIIa with fibrin, a natural substrate for factor XIIIa and a cofactor for the alpha-thrombin-catalyzed activation of plasma factor XIII. The carbamylmethyl derivatives of the active-site thiol group of platelet factor XIII (CMa2) and factor XIIIa (CMa2') were prepared, and their interactions with fibrin were measured. The enzyme-like derivative (CMa2') which contained nicked a' chains bound more tightly to fibrin (Kd = 2.1 microM) than did CMa2 (Kd = 14 microM), the platelet zymogen-like derivative with intact a chains, but the binding of each was weaker than the binding of plasma factor XIII zymogen (a2b2) to fibrin (Kd = 0.20 microM) under the same conditions. Saturation of fibrin with plasma factor XIII zymogen (a2b2) did not affect the binding of CMa2' to fibrin, suggesting that the plasma factor XIII zymogen (a2b2) and the active-site-modified form of factor XIIIa (CMa2') bind to separate, noninteracting sites of fibrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding, Competitive↗

New mutations causing the premature termination of translation in the A subunit gene of coagulation factor XIII.

The amplification of factor XIII A subunit gene exons and heteroduplex analysis has been used to identify two new mutations that cause severe factor XIII deficiency. One mutation in a family of French origin results from a 4 bp deletion and leads to a premature termination of translation. The other mutation occurred in a Turkish family and results from a C-->T transition that inserts a premature translation stop signal at codon 400. Both mutations alter restriction enzyme sites and can be readily detected in amplified exon DNA for genetic counselling or prenatal diagnosis. The new mutations reflect the extensive molecular heterogeneity of factor XIII deficiency.

Child, Preschool↗

[Factor XIII as a stimulator of thrombin activity].

The coagulating activity of thrombin was increased by 120% and the esterase activity--by 100% after incubation of thrombin with factor XIII. Factor XIII also stimulated generation of thrombin in the test of two-step estimation of prothrombin. The effect, arising from the interaction of factor XIII with thrombin, was specific for this enzyme because the esterase activity of trypsin was not increased during incubation of enzyme with factor XIII under the same conditions. The data obtained suggest that factor XIII or its fragment are effectors of enzymatic activity of thrombin in vitro and in vivo.

Animals↗

Characterization of the catalytic subunit of factor XIII by radioimmunoassay.

Plasma factor XIII is composed of two subunits, a and b, whereas platelet and other intracellular zymogens have only a-subunits. The catalytic subunit, a, is the same in all forms. In order to characterize the interactions of 1- with b-chains in the plasma zymogen and a-chains with other molecules and to correlate factor XIII activity with a-protein, a specific, sensitive radioimmunoassay was developed. With the polyclonal antisera used, the assay recognizes all molecular forms of a (zymogens, activation intermediates, enzyme) equally well. The assay can be used to determine a-chain concentration in plasma and serum and in purified test systems. Fibrinogen in high concentrations affects the assay, probably by interfering with the interactions of 125I-a with antibody. However, at the plasma dilutions used in the assay, there is no significant fibrinogen effect. With this assay, the a-chain concentration in normal plasma is approximately 15 micrograms/ml. This compares with 14 micrograms/ml b-chain in plasma and indicates that all of the a- and b-chains in plasma probably circulate in the form of an equimolar zymogen complex. The serum concentration of a-protein is about 6% of the plasma concentration. There is a high correlation between a-protein and factor XIII activity.

Factor XIII↗

Is the factor XIII 34Val/Leu polymorphism a protective factor for cerebrovascular disease?

A frequent polymorphism in the factor XIII (FXIII) A-subunit gene, leading to a Val to Leu amino acid exchange at position 34, suggested to affect clot stability, has been associated with a decreased risk for venous thromboembolism and myocardial infarction. Its role in the development of stroke is still under investigation. Ninety-four patients with primary arterial intracerebral haemorrhage (mean age +/- standard deviation: 69 +/- 14 years; 48 men, 46 women), 718 patients with ischaemic stroke (63 +/- 14 years; 395 men, 323 women) and 369 healthy control subjects (59 +/- 14 years; 299 men, 170 women) were analysed for FXIII Val34Leu. No differences in genotype distribution between all three groups were observed. Also, no significant differences in the genotype distribution were found between subgroups of patients stratified according to age, sex, aetiology, history of hypertension, antiplatelet or anticoagulant medication and other vascular risk factors. In contrast to previously reported findings in smaller collectives, our data suggest that an association of the FXIII Val34Leu polymorphism with a decreased risk of ischaemic stroke or an increased risk of intracerebral haemorrhage is highly unlikely. Thus, screening for the FXIII Val34Leu polymorphism will not contribute significantly to the risk prediction of cerebrovascular disease.

Adult↗

Factor XIII Val34Leu is a genetic factor involved in the etiology of venous thrombosis.

A mutation in the factor XIII gene (FXIII Val34Leu) gene was recently reported to confer protection against myocardial infarction, but its relationship with venous thrombosis is unknown. In addition, a mutation in the 5'-untranslated region of the FXII gene (46 C->T) was identified which is associated with low plasma levels of the protein. Its prevalence in patients with venous thrombosis is also unknown. We investigated the frequency of the FXIII Val34Leu and FXII 46 C->T mutations in 189 patients with deep venous thrombosis and in 187 age-, gender- and race-matched controls. FXIII Val34Leu was detected in 38.6% of the patients and in 41.2% of the controls. Interestingly, homozygosity for the FXIII mutation was found in 1.6% of the patients and in 9.6% of the controls, yielding an odds ratio (OR) for venous thrombosis of 0.16 (95% CI: 0.05-0.5). The OR for heterozygotes was 1.1 (95% CI: 0.7-1.7). The FXII 46 C->T mutation was detected in 46.0% of the patients and in 48.6% of the controls. The OR for heterozygotes was 0.9 (95% CI: 0.6-1.4) and for homozygotes the OR was 0.8 (95% CI: 0.3-1.9). Our data indicate that the FXII 46 C->T mutation is unlikely to be a major risk factor for venous thrombotic disease. In contrast, the homozygous state for FXIII Val34Leu is a strong protective factor against venous thrombosis, which emerges as a novel genetic factor involved in the aetiology of thrombophilia.

Adolescent↗

Binding and degradation of blood coagulation factor XIII by cultured fibroblasts.

The interaction of Factor XIII with cultured fibroblasts was examined using 125I-labeled protein and immunofluorescence. Platelet or plasma Factor XIII bound to confluent cell layers. Binding reached an apparent steady state after 8 h. Activation with thrombin increased the binding of both the platelet and plasma forms of the enzyme. After a 1-2 h lag, a chloroquine-inhibitable increase in trichloroacetic acid-soluble radioactivity was detected in the medium. Gel electrophoresis in sodium dodecyl sulfate indicated that approximately 16-fold more a subunit (catalytic) of 125I-plasma Factor XIII bound to the cell layer than b subunit (carrier) and that some large complexes containing Factor XIII were formed with the cell layer. Factor XIII binding increased linearly with concentrations of Factor XIII up to 230 micrograms/ml, whereas a component of the degradation of Factor XIII was saturable at about 20 micrograms/ml. Factor XIII associated with cell layers was catalytically active since it could cross-link fibronectin. By immunofluorescence the a subunit of Factor XIII was localized to fibronectin-containing extracellular fibrils and, in the presence of chloroquine, to intracellular granules. These results indicate that the a subunit of Factor XIII binds to the fibroblast extracellular matrix and matrix assembly sites, where it remains active, and to a putative cell-surface receptor which mediates its internalization and degradation.

Blood Platelets↗

A unique factor XIII inhibitor to a fibrin-binding site on factor XIIIA.

An 81-year-old woman, who presented with sudden episodes of spontaneous bleeding, was found to have a specific inhibitor of factor XIII. Her fibrin clots had approximately 70% gamma-gamma and no alpha polymer formation, under conditions where normal fibrin was fully cross-linked; the patient's clots were soluble in urea or monochloroacetic acid. Factor XIII activity in her plasma was 24%, measured by the dansylcadaverine incorporation assay. When mixed with normal plasma, the patient's plasma inhibited fibrin cross-linking; however, in mixtures of patient and normal plasma, there was no inhibition of factor XIII activity when assayed by the incorporation of dansylcadaverine into casein. Thus, this inhibitor was active against fibrin cross-linking but not against ligation of small molecules to casein. Consequently, gel electrophoresis of reduced, sodium dodecyl sulfate-solubilized fibrin clots was a simple, quantitative method that was used to measure inhibitor activity. This inhibitor is unique and has been designated inhibitor New Haven. It was neutralized by anti-IgG and anti-kappa. It did not inhibit the activation of factor XIII but did inhibit fibrin cross-linking. There was complex formation between the inhibitor and activated factor XIII (A', A*) but not between A2 or fibrinogen. Only A', A* and the 56-Kd fragment bound to affinity columns made with this IgG. The inhibitor significantly decreased the binding of A', A* to fibrin clots. These data indicate that the epitope for this inhibitor is in a fibrin binding site. It is hidden in the zymogen and expressed on A' and A*, indicating that the conformational change occurring with the cleavage of the activation peptide is sufficient to expose the fibrin binding site.

Aged↗

Molecular mechanisms underlying the proangiogenic effect of factor XIII.

OBJECTIVE: Coagulation Factor XIII (FXIII) was previously shown by us to induce angiogenesis. The aim of this study was to elucidate the molecular events underlying the proangiogenic effects of activated FXIII (FXIIIa) on human umbilical vein endothelial cells (HUVECs). METHODS AND RESULTS: As shown by coimmunoprecipitation studies, FXIIIa crosslinked alpha(v)beta3 with vascular endothelial growth factor receptor 2 (VEGFR-2) and enhanced the noncovalent interaction between the 2 receptors. In addition, FXIIIa induced tyrosine phosphorylation of VEGFR-2 in both the crosslinked high-molecular-weight and the noncovalent VEGFR-2/alpha(v)beta3 complexes. These effects as well as FXIIIa-induced proliferation and migration of HUVECs were abolished by iodoacetamide treatment of FXIIIa (I-FXIII) or by PTKI, an inhibitor of VEGFR-2. FXIIIa induced upregulation of c-Jun and Egr-1 as revealed by quantitative RT-PCR. Electrophoretic mobility-shift assay experiments showed that FXIIIa treatment of HUVECs enhanced binding of Wilm's tumor-1 (WT-1) but not of early growth response (Egr)-1 to the thrombospondin-1 (TSP-1) promoter sequence, suggesting that WT-1 but not Egr-1 is involved in downregulation of TSP-1 expression. CONCLUSIONS: The proangiogenic effect of FXIIIa is mediated by (1) enhancement of crosslinked and noncovalent alpha(v)beta3/VEGFR-2 complex formation; (2) tyrosine phosphorylation and activation of VEGFR-2; (3) upregulation of c-Jun and Egr-1; and (4) downregulation of TSP-1 induced indirectly by c-Jun through WT-1. These processes may clarify FXIII role in vascular remodeling and tissue repair.

Cells, Cultured↗

Impaired wound healing in factor XIII deficient mice.

Factor XIII that stabilizes fibrin clots in the final stages of blood coagulation also participates in wound healing, as can be inferred from a delay in wound repair in some patients with inherited FXIII deficiency. In this study we evaluated the effect of FXIII on wound healing in FXIII-deficient mice. Three groups of mice (n = 10) were employed: control group, FXIII-deficient group and FXIII-deficient group treated with FXIII concentrate. Excisional wounds were left unsutured and undressed, and mice were followed for eleven days. FXIII-deficient mice exhibited impaired wound healing as has been demonstrated by 15%, 27% and 27% decrease in percentage of wound closure on day 4, 8 and 11, respectively. On day 11 complete healing was observed in control (100% closure), 73.23% in FXIII-deficient and 90.06% in FXIII deficient/FXIII-treated groups (p = 0.007 by ANOVA and p = 0.001 by t-test between control and FXIII-deficient groups). Scoring system representing maturation rate of the wounds showed that the scores for the control, FXIII-deficient and FXIII deficient/FXIII treated groups were 94.9 +/- 4.7, 61.5 +/- 14.5 and 94.5 +/- 6.4, respectively (p < 0.001 by ANOVA). Histological analysis of the lesions performed at day 11 disclosed delayed reepithelization and necrotized fissure in FXIII-deficient mice and normal healing in FXIII-deficient/FXIII-treated mice. The findings of this study confirm that in FXIII-deficient mice wound healing is delayed and the cellular and tissue defects can be corrected by treatment with FXIII, providing evidence for the essential role of FXIII in wound repair and remodeling.

Analysis of Variance↗

Identification of intracellular factor XIII in human monocytes and macrophages.

Factor XIII is a blood protransglutaminase that is distributed in plasma and platelets. The extracellular and intracellular zymogenic forms differ in that the plasma zymogen contains A and B subunits, while the platelet zymogen has A subunits only. Both zymogens form the same enzyme. Erythrocytes, in contrast, contain a tissue transglutaminase that is distinct from Factor XIII. In this study other bone marrow-derived cells were examined for transglutaminase activity. Criteria that were used to differentiate Factor XIII proteins from erythrocyte transglutaminase included: (a) immunochemical and immunohistochemical identification with monospecific polyclonal and monoclonal antibodies to Factor XIII proteins, (b) requirement for thrombin cleavage to express activity, (c) pattern of fibrin cross-linking catalyzed by the enzyme, and (d) different electrophoretic mobilities in nondenaturing gel systems. By these criteria human peripheral blood monocytes, peritoneal macrophages, and monocytes maintained in culture contain an intracellular protransglutaminase that is the same as platelet Factor XIII. The monocyte-macrophage protein is thrombin-sensitive, and under appropriate conditions there is no enzyme expression without activation of the zymogen. Both the monocyte-macrophage zymogen and enzyme have the same electrophoretic mobilities as platelet Factor XIII zymogen and enzyme. Antibody to A protein reacts with the monocyte-macrophage protein. B protein is not associated with this intracellular zymogen. By immunoperoxidase staining monocyte-macrophage protein seems to be localized in the cytoplasm, similar to the known cytoplasmic distribution of platelet and megakaryocyte Factor XIII. These procedures were also used to study populations of human granulocytes and lymphocytes, and protransglutaminase activity was not observed in these cells.

Acyltransferases↗

Expression of functional coagulation factor XIII in Escherichia coli.

Coagulation factor XIII is a zymogen that can be activated by thrombin cleavage to a transglutaminase that catalyses the formation of covalent crosslinks between fibrin chains in the final stages of the blood clotting cascade. Although circulating factor-XIII is composed of A and B subunits the catalytic activity is a property of the A subunits. In this study we have constructed a plasmid (pKKF13A) that contains a cDNA encoding the A subunit positioned downstream of a tac promoter. Escherichia coli containing this plasmid produce A subunit protein when grown in the presence of IPTG. The cloned A subunit has been partially purified and characterized. Comparison with A subunits purified from plasma showed that the cloned A subunits were of the same size, assembled as dimers, and had the same native electrophoretic mobility. The cloned A subunits expressed transglutaminase activity with putrescine, dansylcadaverine and casein as substrates, and were able to crosslink fibrin in clots formed from A subunit deficient plasma. These studies have demonstrated that functional recombinant factor XIII A subunit can be produced in E. coli and suggest that recombinant factor XIII can potentially provide a safe and inexhaustible supply for therapeutic use.

Amino Acid Sequence↗

The zymogen forms of blood coagulation factor XIII bind specifically to fibrinogen.

To examine the possibility that Factor XIII zymogens bind to fibrinogen, we have studied the reaction between radiolabeled Factor XIII and fibrinogen coupled to beads. Platelet and plasma Factor XIII were iodinated with Na(125I)iodide using lactoperoxidase. Both forms of 125I-Factor XIII retained greater than 92% of the transglutaminase activity. 125I-platelet and plasma Factor XIII specifically bound to human fibrinogen covalently coupled to either carboxylated latex or acrylonitrile beads but not to fetuin- or albumin-coated beads. Unlabeled platelet Factor XIII inhibited 90% of the total binding of 125I-platelet and 125I-plasma Factor XIII to fibrinogen, whereas human IgG, fetuin, and serum albumin had no effect. These data suggest that 125I-platelet and plasma Factor XIII specifically bind to fibrinogen by the a2 subunit. 125I-Factor XIII which was bound to the fibrinogen beads migrated identically to unbound material on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Soluble fibrinogen inhibited binding of 125I-Factor XIII to fibrinogen beads, indicating that binding is not due to alteration of the fibrinogen coupled to the beads. Binding of 125I-Factor XIII was reversible and time- and temperature-dependent: maximal binding occurred by 1 min at 37 degrees C. Binding was independent of calcium; 10 mM EDTA had no effect. Binding was dependent on sodium chloride concentration; complete inhibition of binding occurred at concentrations above 300 mM NaCl. The Kd for binding, 1 X 10(-8) M, is approximately 7-fold higher than the concentration of Factor XIII in plasma. These data support the hypothesis that Factor XIII circulates in plasma bound to fibrinogen. This interaction may play a role in regulating the physiologic activation and function of Factor XIII.

Blood Platelets↗

Regulation of plasma factor XIII binding to fibrin in vitro.

The binding of plasma factor XIII to fibrinogen or fibrin that has been chemically or enzymatically induced to polymerize was studied. Factor XIII binding was assayed using a 3H-putrescine incorporation assay and an 125I-plasma factor XIII binding assay. More than 80% of the native and radiolabeled plasma factor XIII was bound to fibrin I formed by reptilase in EDTA, citrate, or heparin anticoagulated plasma. Plasma factor XIII and 125I-factor XIII was bound (89.6% to 92.5%) to fibrin II formed by thrombin in either citrate or EDTA anticoagulated plasma. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of 125I-plasma factor XIII bound to fibrin I or fibrin II formed by reptilase or thrombin in the presence of EDTA demonstrated the b2-subunit remained bound to the a-chains or thrombin-cleaved a-chains. In the presence of calcium chloride and thrombin, the b2-subunit dissociated and factor XIIIa was bound. Protamine sulfate caused fibrinogen polymerization in the absence of divalent cations and reduced both plasma factor XIII and immunologic fibrinogen levels. Fibrinogen polymerized by protamine sulfate bound plasma factor XIII and the a2-subunit of 125I-platelet factor XIII. Plasma factor XIII was also bound to sonicated non-cross-linked fibrin II in either normal plasma or afibrinogenemic plasma. Plasma levels of several coagulation proteins were unchanged after the addition of reptilase, protamine sulfate, or sonicated fibrin to plasma. These results demonstrate that a specific binding site for the a2-subunit of plasma factor XIII is present on polymerized fibrinogen, fibrin I, and fibrin II. Furthermore, the presence of divalent cations, thrombin-cleavage of plasma factor XIII, and release of fibrinopeptides A or B are not required for plasma factor XIII binding to polymerized fibrinogen and fibrin.

Antithrombins↗

Factor XIII deficiency: pathogenic mechanisms and clinical significance.

Congenital factor XIII deficiency is a rare disease, but has provided valuable information on the physiological role of factor XIII and the benefit of factor XIII replacement therapy. It could be shown that not only homozygous patients but also heterozygotes are at risk for bleeding complications. Acquired factor XIII deficiency, however, is much more common, and preliminary studies suggest a lack of factor XIII to be an important feature of various diseases. In acute states and severe hemorrhages, replacement therapy with factor XIII concentrates is recommended. Recent progress in assay methods and future clinical studies should help to evaluate the therapeutic potential of factor XIII.

Autoantibodies↗

Expression, purification, and characterization of human factor XIII in Saccharomyces cerevisiae.

Factor XIII is the terminal enzyme of the clotting cascade. A cDNA sequence encoding human placental factor XIII was expressed in Saccharomyces cerevisiae with the yeast ADH2-4c promoter. Expression levels were a strong function of the noncoding flanking DNA content of the construction. When the terminal 3'-flanking noncoding DNA was removed, expression increased approximately 50-fold. The protein was produced in quantity by high-yield fermentation and purified to homogeneity. The recombinant protein was cleaved by thrombin at the same activation site as purified human placental FXIII and exhibited 100% enzymatic activity. At high thrombin concentrations rFXIIIa was cleaved into inactive 54- and 25-kDa polypeptides. The identity of these cleavage sites and the blocked N-terminus to that of the human protein was revealed by amino acid microsequencing. A time course of thrombin activation was performed and the relative distribution of the thrombin-cleaved subunits to the uncleaved zymogen subunits determined; the results were consistent with the half of the sites catalytic model for transglutaminase activity proposed by Chung et al. (Chung, S. I., Lewis, M. S., & Folk, J. E. (1974) J. Biol. Chem. 249, 940-950, 1974) and Hornyak et al. (Hornyak, T. J., Bishop, P. D., & Shafer, J. A. (1989) Biochemistry 28, 7326-7332). Equilibrium and velocity sedimentation analysis indicated that rFXIII exists as a 166-kDa nondissociating dimer that behaves as a compact particle of 8.02 S. Thus, all of the properties of rFXIII thus far examined are consistent with those reported for human platelet and placental FXIII.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

Factor XIII in human plasma and platelets.

Plasma and platelet factor XIII levels were measured in normal human donors and in a patient congenitally deficient in factor XIII. The purpose of these experiments was to study the role of platelet factor XIII in blood coagulation. On polyacrylamide disc electrophoresis, factor XIII activity in extracts of washed normal platelets appeared as a single peak. This peak was missing or very low when factor XIII-deficient platelet extract was used. The patient was also studied before and after transfusion of fresh frozen plasma. Before transfusion, factor XIII activity could not be detected in the patient's plasma or platelet extracts. 24 hr after transfusion the plasma factor XIII level was still at the anticipated value, but factor XIII activity could not be detected in the platelet extracts. These experiments imply that plasma factor XIII was not transported across the platelet membrane in measurable quantities in vivo. This suggests that platelet factor XIII is a true platelet component and originates in the platelet precursor, the megakaryocyte. Thrombelastographic studies suggest that platelet factor XIII participates in the coagulation process. Thrombelastograms of factor XIII-deficient samples had decreased maximum amplitude and clot elasticity values. The abnormalities were fully corrected by the addition of washed normal platelets to factor XIII-deficient plasma; preincubation of the normal platelets in the deficient plasma had no additional effect. This indicates that platelet factor XIII is immediately available during clot formation.

Adolescent↗

Clot retraction in a factor XIII free system.

The role of Factor XIII in clot retraction was studied using the plasma from Factor XIII-deficient patients. Time course experiments revealed no significant difference in clot retraction between a plasma deficient in Factor XIII and one to which purified Factor XIII had been added. Using Factor XIII-free fibrinogen and Factor XIII-deficient platelets, it is shown that there is no significant difference in clot retraction with or without added Factor XIII.

Clot Retraction↗