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Contact with the N termini in the central E domain enhances the reactivities of the distal D domains of fibrin to factor XIIIa.

The reaction of Factor XIIIa with fibrin is the last enzyme-catalyzed step on the coagulation cascade, leading to the formation of a normal blood clot. The finding that fibrin is preferred by the cross-linking enzyme about 10-fold over the circulating fibrinogen suggests the operation of a unique substrate-level control for the orderly functioning of the physiological process in the forward direction. An important task is to elucidate the molecular mechanism for the transmission of the signal generated by the thrombin-catalyzed cleavage in the central E domain of fibrin to the distant Factor XIIIa-reactive glutamine residues. By focusing on the substrate sites present in gamma chain remnants of D type domains of fibrinogen and by employing the approach of fragment complementation with the regulatory E domain, which represents the thrombin-modified portion of fibrin, we have now succeeded in reconstructing in solution the phenomenon of kinetic enhancement for the reaction with Factor XIIIa. Two D type preparations (truncated fibrinogen, approximately 250 kDa and D', approximately 105 kDa) were obtained by digestion of human fibrinogen with endo Lys-C. Neither product could be cross-linked by Factor XIIIa, but as shown by the incorporation of dansylcadaverine, both were acceptor substrates for the enzyme. The plasmin-derived D (approximately 105-kDa) product, however, could be cross-linked into DD dimers. In all cases, the admixture of E fragments exerted a remarkable boosting effect on the reactions with Factor XIIIa. Even with native fibrinogen as substrate, cross-linking of gamma chains was enhanced in the presence of E. Nondenaturing electrophoresis was used to demonstrate the complex forming potential of E fragments with fibrinogen, truncated fibrinogen, D', or D. The GPRP tetrapeptide mimic of the GPRV N-terminal sequence of the alpha chains in the E fragments, abolished both complex formation and the kinetic boosting effect of E on the reactions of substrates with Factor XIIIa. Thus, the N-terminal alpha chain sequences seem to act as organizing templates for spatially orienting the D domains, probably during the protofibrillar assembly of the fibrin units, for favorable reaction with Factor XIIIa.

Binding Sites↗

Factor XIIIA Calgary: a candidate missense mutation (Leu667Pro) in the beta barrel 2 domain of the factor XIIIA subunit.

Molecular analysis performed on a Canadian family with congenital factor XIII deficiency revealed a homozygous missense mutation (Leu667Pro) in exon 14 of the A subunit gene in three affected siblings. The mutation results from a T-to-C transition at nucleotide position 2087 and generates a new Msp1 restriction site. Digestion of an amplified fragment containing exon 14 with this restriction enzyme enabled the heterozygous allele to be identified in both parents (who were third cousins) and three other family members. SSCP analysis detected no additional mutations in the coding or consensus splice sequences of the A subunit gene. The mutant nucleotide substitution was absent in 60 normal alleles and 10 unrelated patients with XIIIA deficiency. Leu667 is located in the carboxyl terminal beta barrel 2 domain of the A subunit molecule. Computer modelling based on 3D crystallographic data predicts that the mutant protein has aberrant folding and is likely to be rapidly degraded following translation.

Factor VIIIa↗

Atypical cells in radiation dermatitis express factor XIIIa.

Dendritic cells that express factor XIIIa are present in the normal dermis and are increased in a variety of pathologic conditions. Atypical dermal cells are often seen in biopsy specimens of skin that has been previously irradiated. We sought to determine whether the atypical dermal cells in chronic radiation dermatitis express factor XIIIa. We employed standard immunohistochemical techniques with antibodies to factor XIIIa and CD34 to study 16 biopsy samples showing changes of radiation dermatitis. All cases showed diffuse positive cytoplasmic staining of atypical dermal cells with antibody to factor XIIIa. Of 16 cases, 10 showed focal staining of dermal cells with antibody to CD34, but this antibody did not react with most of the atypical dermal cells. We conclude that the majority of atypical dermal cells in radiation dermatitis are derived from dermal dendritic cells which express factor XIIIa.

Adult↗

Specific binding of blood coagulation factor XIIIa to thrombin-stimulated platelets.

We studied the binding of 125I-platelet and plasma Factor XIII (125I-Factor XIII) to human platelets. When 125I-Factor XIII was incubated with gel-filtered platelets, calcium chloride (5 mM) and thrombin (1 unit/ml) at 37 degrees C, saturable binding was observed. Half-maximal binding occurred at 1 min. Binding was inhibited 93% by a 100-fold molar excess of unlabeled ligand but not by other purified proteins. Greater than 87% of platelet-bound radioactivity migrated as thrombin-cleaved a-chains (a'-chains) in sodium dodecyl sulfate-polyacrylamide gels indicating that Factor XIIIa but not Factor XIII binds to platelets. 125I-Factor XIIIa does not bind to unstimulated platelets. When platelet secretion was blocked, binding was markedly inhibited. 125I-Factor XIIIa bound minimally to platelets stimulated with agonists other than thrombin. Thus, binding is dependent on platelet activation, as well as modification of platelets by thrombin. 125I-Factor XIIIa bound to gamma-thrombin-stimulated platelets, at concentrations which did not clot fibrinogen. Therefore, Factor XIIIa is not bound to fibrin associated with platelets. Binding was only partially reversible. Approximately 12,000 molecules of Factor XIIIa were bound per platelet. 125I-Factor XIIIa bound normally to platelets from patients with severe Glanzmann's thrombasthenia indicating that 125I-Factor XIIIa does not bind to platelet glycoproteins IIb or IIIa, or platelet-bound fibrinogen. Chymotrypsin treatment of platelets inhibited 125I-Factor XIIIa binding by 78% without inhibiting secretion. Methylamine and putrescine, Factor XIIIa substrates, and N-ethylmaleimide, an active site inhibitor, did not inhibit binding. Factor XIIIa bound to platelets was enzymatically active and catalyzed [3H]putrescine incorporation into platelet proteins. The specific binding of Factor XIIIa to platelets suggests it may play a role in physiologic reactions involving platelets.

Binding Sites↗

Factor XIIIA and clot strength after cardiopulmonary bypass.

Reduced factor XIIIA levels and decreased clot strength have been associated with increased bleeding after cardiopulmonary bypass (CPB). The purpose of this study was to evaluate the relationship between hemostatic factors, including factor XIIIA, and clot strength before, during and after CPB. Factor XIIIA antigen, platelet counts, fibrinogen, factor V activity, tissue plasminogen activator and clot strength (by thromboelastograph) were measured at baseline, after 45 min of CPB, at the end of CPB and 4 h post-operatively in 34 patients. Baseline factor XIIIA antigen was 5.2 +/- 1.4 mg/l. On average, factor XIIIA levels dropped to 64% and clot strength to 77% of baseline values after 45 min on CPB and remained below baseline during the immediate post-operative period. Clot strength was significantly correlated (r = 0.81) with platelet count and fibrinogen but not plasma factor XIIIA levels. Addition of 10 mg/l recombinant factor XIII[a2] significantly increased clot strength. Postoperative bleeding at 2 h was inversely correlated with platelet count, factor XIIIA antigen and clot strength measured at the end of CPB. Maintenance of adequate platelet counts and factor XIIIA levels at the end of CPB may play a role in maintaining clot strength and reducing blood loss.

Adult↗

Cytofluorometric identification of plasmin-sensitive factor XIIIa binding to platelets.

We have investigated the binding of blood coagulation factor XIIIa to thrombin-stimulated platelets using cytofluorometric analysis. Washed thrombin-stimulated platelets bound exogenously added factor XIIIa in a calcium-dependent reaction. The expression of endogenous platelet factor XIII was also detected on the surface of thrombin-stimulated platelets. When fluorescence analysis was performed based on particle size, factor XIIIa bound to the surface of greater than 95% of particles which contained more than one platelet, but only 50% of single platelets. The binding of factor XIIIa to thrombin-stimulated platelets was inhibited by plasmin. Plasmin also inhibited thrombin-dependent expression of the factor XIIIa binding site on platelets. Experiments in which thrombin-stimulated platelets were incubated with factor XIIIa in the presence of 125I-dimethylcasein or 3H-putrescine demonstrated that platelets bear both glutamyl and lysyl substrates for factor XIIIa. Thrombin increased the expression of factor XIIIa substrates by platelets. Plasmin inhibited both the expression of factor XIIIa substrates and degraded them. The binding of factor XIIIa to thrombin-stimulated platelets and the availability of factor XIIIa substrates on the platelet surface could provide a mechanism by which factor XIIIa stabilizes the hemostatic plug by promoting crosslinking reactions between platelet membrane proteins and adhesive glycoproteins. In contrast, plasmin inhibition of factor XIIIa binding and crosslinking could disrupt hemostasis.

Blood Platelets↗

Protein-protein interactions in blood clotting. The use of polarization of fluorescence to measure the dissociation of plasma factor XIIIa.

1. Human plasma Factor XIII (the precursor of fibrin-glutamine-fibrin-lysine endo-gamma-glutamyltransferase) was randomly labelled by incubation with fluorescein isothiocyanate. The biochemical properties of the system were unaltered by the label. The polarization of the fluorescein fluorescence attached to the plasma protein was measured and the following conclusions were reached. 2. Factor XIII (a'2b2) does not dissociate in the protein-concentration range 10-500 microgram/ml either with or without added Ca2+. 3. Factor XIIIa (a'2b2) does not dissociate in the absence of Ca2+ in the protein-concentration range 10-500 microgram/ml. 4. Additions of Ca2+ to Factor XIIIa result in a decreased polarization of fluorescence as the tetramer dissociates. The decrease in polarization was the same amplitude at protein concentrations 10-500 microgram/ml and Ca2+ concentrations 2-66 mM and indicates that the overall process is essentially irreversible. The decrease in polarization consisted of fast and slow exponential phases. Both the rate of the fast phase and the proportion of the reaction it represented increased with Ca2+ concentration. 5. A comparison of the rate of dissociation measured by fluorescence polarization and the rate of appearance of enzyme activity in the presence of a protein substrate suggests that the Factor XIII is autoactivated by a soluble a-subunit-containing molecular forming a tight complex with the substrate.

Blood Proteins↗

Cross-linking exogenous bifunctional peptides into fibrin gels with factor XIIIa.

Bi-domain peptides with a factor XIIIa substrate in one domain and a bioactive peptide in another domain were covalently incorporated into fibrin gels during coagulation through the action of the transglutaminase factor XIIIa. The cross-linking characteristics were determined for two bi-domain peptides with factor XIIIa substrates based on fibrinogen, dYRGDTIGEGQQHHLGG-NH2, and dLRGDGAKDV-NH2, as well as one bi-domain peptide with a substrate sequence based on alpha2-plasmin inhibitor, dLNQEQVSPLRGD-NH2, and another with a nonbiological, oligolysine substrate, dLRGDKKKKG-NH2 (substrate domains in italic). Each of these peptides was able to cross-link into the fibrin gels during coagulation, with the peptide containing the factor XIIIa substrate based on alpha2-plasmin inhibitor being incorporated at levels in excess of 8 mol/mol fibrinogen. The structural characteristics of these peptide-modified gels proved to be the same as those for a native fibrin gel. The bioactivity of the incorporated active factors was tested in a neuronal culture model with day 8 chicken dorsal root ganglia using two bioactive sequences, RGD and DGEA, and one inactive control sequence, RDG. Each of these peptides influenced the extension of neurites from the ganglia as expected, indicating that the incorporated factors retained their activity. With the use of soluble competitive inhibitors, it was shown that this effect was due to the covalently incorporated peptides. Through exploiting the role of factor XIIIa in coagulation, we have developed a method by which to impart the character of nonfibrin proteins, such as extracellular matrix proteins, to fibrin, a biological material with many potential therapeutic and academic applications.

Amino Acid Sequence↗

Loss of factor XIIIa in pig dermis during tissue expansion.

Considerable evidence suggests that factor XIIIa, a blood coagulation factor, also functions in tissue repair, and specifically in the dynamic process of fibroplasia. On the other hand, the dynamic process of tissue expansion would require a loosening of the dermis, the opposite of fibroplasia. We examined the effects of tissue expansion on the expression of factor XIIIa in pig skin. Standard immunohistochemical procedures were used coupled with a rabbit antibody to factor XIIIa. In this report, we demonstrate that the normal expression of factor XIIIa in pig dermis is completely inhibited at the apex overlying the tissue expander. Factor XIIIa inhibition during expansion supports the thesis that this substance is important in the production and maintenance of fibroplasia.

Animals↗

The effect of fibrin polymers on thrombin-catalyzed plasma factor XIIIa formation.

The effect of fibrin polymers on thrombin-catalyzed factor XIIIa formation was studied in afibrinogenemic plasma. Fibrin polymers derived from des A fibrinogen and des A,B fibrinogen increased sixfold the rate of thrombin-catalyzed factor XIIIa formation in the presence of EDTA. Calcium chloride accelerated factor XIIIa formation 14-fold in the presence of des A,B fibrinogen without increasing the rate of thrombin formation. Fibrinopeptides A and B had no effect on factor XIIIa formation in afibrinogenemic plasma. Des A,B fibrinogen reduced by 20- to 40-fold the thrombin concentration required to activate factor XIII. Glycyl-L-prolyl-L-arginyl-L-proline (gly-pro-arg-pro), a fibrin polymerization inhibitor, inhibited des A and des A,B fibrinogen from enhancing thrombin-catalyzed factor XIIIa formation. Gly-pro-arg-pro did not modify factor XIIIa formation in afibrinogenemic plasma and did not inhibit thrombin cleavage of the chromogenic substrate S-2238. These results demonstrate that fibrin polymers accelerate thrombin-catalyzed plasma factor XIIIa formation.

Afibrinogenemia↗

Primary structure of blood coagulation factor XIIIa (fibrinoligase, transglutaminase) from human placenta.

We have determined the primary structure of human placental factor XIIIa, an enzyme [fibrinoligase, transglutaminase, fibrin-stabilizing factor, EC 2.3.2.13 (protein-glutamine:amine gamma-glutamyltransferase)] that forms intermolecular isopeptide bonds between fibrin molecules as the last step in blood coagulation. Placental factor XIIIa is an unglycosylated polypeptide chain of 730 amino acid residues (Mr = 83,005) that appears to be identical to the a subunit of the plasma zymogen factor XIII. Ca2+-dependent activation of factor XIIIa by thrombin removes a blocked amino-terminal peptide and unmasks a reactive thiol group at Cys-314. A second specific cleavage after Lys-513 by thrombin inactivates factor XIIIa and produces an amino-terminal 56-kDa fragment and a 24-kDa fragment. The amino acid sequence of factor XIIIa is unique and does not exhibit internal homology, but its active center is similar to that of the thiol proteases. The probable Ca2+-binding site of factor XIIIa has been identified by homology to the high-affinity sites in calmodulins. Knowledge of the primary structure of factor XIIIa will aid elucidation of the mechanism of its enzymatic action and that of the many tissue transglutaminases of which it is the prototype. This will also facilitate production of factor XIIIa by recombinant DNA technology for use in treatment of congenital factor XIII deficiencies and in the postoperative healing of wounds.

Amino Acid Sequence↗

Factor XIIIa in the hamartomas of tuberous sclerosis.

Factor XIII is a blood coagulation factor which may also be produced in an intracellular location. The 'a' subunit of this factor has been found in a number of different cell types and has been shown to stimulate the proliferation of fibroblasts in vitro. We have examined cutaneous, central nervous system and renal lesions from persons with tuberous sclerosis using a standard immunohistochemical assay to see if factor XIIIa is expressed in these hamartomatous growths. We found factor XIIIa in most of the stromal cells composing the skin lesions of tuberous sclerosis as well as in cells of subependymal giant cell astrocytoma of the brain and the stromal cells in renal angiomyolipoma. Expression of factor XIIIa may be of significance in the formation of fibrous growths in tuberous sclerosis.

Adolescent↗

Factor XIIIa supports microvascular endothelial cell adhesion and inhibits capillary tube formation in fibrin.

Coagulation factor XIIIa is a transglutaminase that catalyzes covalent cross-link formation in fibrin clots. In this report, we demonstrate that factor XIIIa also mediates adhesion of endothelial cells and inhibits capillary tube formation in fibrin. The adhesive activity of factor XIIIa was not dependent on the transglutaminase activity, and did not involve the factor XIIIb-subunits. The adhesion was inhibited by 99% using a combination of monoclonal antibodies directed against integrin alpha(v)beta(3) and beta(1)-containing integrins, and was dependent on Mg(2+) or Mn(2+). Soluble factor XIIIa also bound to endothelial cells in solution, as detected by flow cytometry. In addition, factor XIIIa inhibited endothelial cell capillary tube formation in fibrin in a dose-dependent manner. Furthermore, the extent of inhibition differed in 2 types of fibrin. The addition of 10 to 100 microg/mL factor XIIIa produced a dose-dependent reduction in capillary tube formation of 60% to 100% in gammaA/gammaA fibrin, but only a 10% to 37% decrease in gammaA/gamma' fibrin. These results show that factor XIIIa supports endothelial cell adhesion in an integrin-dependent manner and inhibits capillary tube formation. (Blood. 2000;95:2586-2592)

Cell Adhesion↗

Identification of factor-XIIIa-reactive glutaminyl residues in the propolypeptide of bovine von Willebrand factor.

von Willebrand factor is a large multimeric plasma protein which plays important roles in platelet aggregation, blood coagulation and probably also in the adhesion of endothelial cells. A 100-kDa propeptide, called the propolypeptide of von Willebrand factor (pp-vWF), is generated during biosynthesis. We found that pp-vWF served as a substrate for transglutaminases including human factor XIIIa and guinea pig liver transglutaminase [Usui, T., Takagi, J. & Saito, Y. (1993) J. Biol. Chem. 268, 12311-12316]. As such, it could form cross-linked copolymers with the extracellular matrix protein, laminin, making it all the more likely that pp-vWF plays a role in cell adhesion phenomena [Takagi, J., Sudo, Y., Saito, T. & Saito, Y. (1994) Eur. J. Biochem. 222, 861-867]. In this work, we identified the Gln residues in pp-vWF specifically reacting with blood coagulation factor XIIIa as amine acceptors. The fluorescent amine, dansylcadaverine, was employed for labeling the enzyme-reactive sites of the protein. Following partial proteolysis, fragments containing the labeled Gln residues were isolated by passage through an anti-dansyl affinity chromatographic column. Amino acid sequence analyses of the fragments revealed that, out of about 40 Gln residues in pp-vWF, only four could be modified in the factor-XIIIa-catalyzed reaction.

Amino Acid Sequence↗

Clinical significance of measuring blood coagulation factor XIIIA regularly and continuously in patients with Crohn's disease.

BACKGROUND: The aim of the present paper was to determine the mechanism by which the level of coagulation factor XIIIA declines during the active phase of Crohn's disease. METHODS: The relationship between the activity of Crohn's disease and factor XIIIA was observed in 31 patients with Crohn's disease prospectively. The relationship between factor XIIIA and thrombin-antithrombin III complex (TAT), factor XIIIA expressed on the surface of peripheral monocytes, was also evaluated. RESULTS: During the first year, there were 11 patients with Crohn's disease in the active phase and 20 patients who remained in remission. The average of the lowest level of factor XIIIA among the patients in the active phase was 60.1%. The average of the lowest level of factor XIIIA in patients who remained in remission was 78.1% (P = 0.049). Among the 20 patients who remained in remission for 1 year, eight patients had factor XIIIA levels below 70%. Six of them required surgical enterectomies, on average 2 years and 1 month later. However, none of the 12 patients who remained in remission for 1 year and who never had factor XIIIA levels <70% had a surgical enterectomy during follow up of 4 years and 6 months (P = 0.002). The decline of factor XIIIA was not due to increased consumption secondary to blood coagulation (TAT), nor was it due to a decline in the function of monocytes that produce factor XIIIA. CONCLUSION: Factor XIIIA declines during the active phase of Crohn's disease because it might be consumed in the repair of injured tissue.

Adult↗

Regulation of formation of factor XIIIa by its fibrin substrates.

Thrombin-catalyzed release of activation peptide (AP) from plasma factor XIII was studied to characterize the regulation of this initial step in the activation of factor XIII zymogen (fibrin-stabilizing factor). High-performance liquid chromatography was used to monitor the kinetics of release of AP. Non-cross-linked polymeric fibrins I and II (polymerized des-A- and des-A,B-fibrinogens), physiological substrates of factor XIIIa, were shown to be potent promoters of thrombin-catalyzed release of activation peptide from factor XIII. These promoters are proposed to act by complexing factor XIII and reducing the apparent Km for thrombin-catalyzed release of AP. Since thrombin-catalyzed release of AP is inefficient in the absence of polymerized fibrin, this mode of regulation should minimize formation of factor XIIIa prior to the formation of its fibrin substrates. The promoting activity of polymeric fibrin was rapidly lost when catalytically competent factor XIIIa was allowed to form. This observation suggested the possibility that factor XIIIa catalyzed cross-linking of fibrin inactivates fibrin as a promoter for the thrombin-catalyzed release of AP from factor XIII. Consistent with this view, the thiol reagent S-methyl methanethiosulfonate inactivated factor XIIIa, blocked cross-linking of fibrin, and protected against loss of its promoter activity. This mode of feedback regulation of the activation process by catalytically active factor XIIIa may serve to ensure against continued generation of factor XIIIa after its fibrin substrates have been cross-linked.

Calcium↗

Characterization of cDNA coding for human factor XIIIa.

A cDNA library prepared from human placenta has been screened for sequences coding for factor XIIIa, the enzymatically active subunit of the factor XIII complex that stabilizes blood clots through crosslinking of fibrin molecules. Two oligonucleotides, based on the amino acid sequences of tryptic peptides of factor XIIIa, were used as hybridization probes. Of 0.36 X 10(6) independent recombinants, 1 clone was identified that hybridized to both probes. The insert of 1704 base pairs coded for the amino-terminal 541 amino acid residues of the mature factor XIIIa molecule. Blot-hybridization analysis using this cDNA as a probe showed that the factor XIIIa mRNA from placenta has a size of approximately 4000 bases. The insert was used to rescreen cDNA libraries and to identify further factor XIIIa-specific sequences. The total length of the isolated factor XIIIa cDNA is 3905 bases, and it codes for a protein of 732 amino acids. In spite of the presence of factor XIII in blood plasma, we could not identify a leader sequence typical for secreted proteins.

Amino Acid Sequence↗

The impact of factor XIIIa V34L polymorphism on plasma factor XIII activity in the Chinese and Asian Indians from Singapore.

Factor XIII (FXIII) is a plasma transglutaminase that is essential for normal haemostasis and fibrinolysis. A few polymorphic sites have been identified in the gene, one of them being a point mutation (V34L) in exon 2 of the FXIIIa subunit gene leading to an amino acid change of valine to leucine. We have examined the role of this polymorphism in relation to plasma FXIII activity in a total of 532 healthy individuals belonging to two ethnic groups in Singapore. The frequency of the L34 allele was significantly higher ( P<0.001) among the Asian Indians (0.08) when compared with the Chinese (0.005). No significant difference in frequency of the L34 allele was observed between Asian Indian CAD patients and controls. The mean FXIII levels were significantly higher ( P<0.0005) among the Asian Indians (148.4%+/-35.5) when compared with Chinese (111.2%+/-26.7). The L34 variant was associated with increased FXIII activity among Asian Indian females. This study shows that both racial and genetic components play a significant role in determining plasma FXIII activity. The effect of V34L polymorphism on FXIII activity in the Indian females is independent of the effects of the P564L and E651Q polymorphic sites in the FXIIIa gene.

Asian People↗