Human factor XII (Hageman factor)

Can half-marathon affect overall health? The yin-yang of sport

Physical activity improves overall health and counteracts metabolic pathologies. Adipose tissue and bone are important key targets of exercise; the prevalence of diseases associated with suboptimal physical activity levels has increased in recent times as a result of lifestyle changes. Mesenchymal stem cells (MSCs) differentiation in either osteogenic or adipogenic lineage is regulated by many factors. Particularly, the expression of master genes such as RUNX2 and PPARγ2 is essential for MSC commitment to osteogenic or adipogenic differentiation, respectively. Besides various positive effects on health, some authors have reported stressful outcomes as a consequence of endurance in physical activity. We looked for further clues about MSCs differentiation and serum proteins modulation studying the effects of half marathon in runners by means of gene expression analyses and a proteomic approach. Our results demonstrated an increase in osteogenic commitment and a reduction in adipogenic commitment of MSCs. In addition, for the first time we have analyzed the proteomic profile changes in runners after half-marathon activity in order to survey the related systemic adjustments. The shotgun proteomic approach, performed through the immuno-depletion of the 14 most abundant serum proteins, allowed the identification of 23 modulated proteins after the half marathon. Interestingly, proteomic data showed the activation of both inflammatory response and detoxification process. Moreover, the involvement of pathways associated to immune response, lipid transport and coagulation, was elicited. Notably, positive and negative effects may be strictly linked. Data are available via ProteomeXchange with identifier PXD006704.

SIGNIFICANCE

We describe gene expression and proteomic studies aiming to an in-depth understanding of half-marathon effects on bone and adipogenic differentiation as well as biological phenomena involved in sport activity. We believe that this novel approach suggests the physical effects on overall health and show the different pathways involved during half marathon. Contents of the paper have not been published or submitted for publication elsewhere. The authors declare no conflict of interest.

Inhibition of protease in intact fish fillets by soaking in or injection of recombinant soy cystatin or bovine plasma

Arrowtooth flounder (AF) fillets are known to contain a heat-activated cysteine protease similar to that found in Pacific whiting, which results in soft texture upon cooking. A crude recombinant soy cystatin (CRSC) produced by Escherichia coli, which has been shown to inhibit the protease(s) in Pacific whiting, was introduced into AF fillets by immersion or injection at one of three levels of inhibitory activity: 10 times less than, equal to, or 10 times greater than that of a 20% bovine plasma protein (BPP) solution, a known inhibitor of AF protease(s). Fillets treated with CRSC or BPP at equal inhibitory strength subsequently exhibited the same degree of protection against textural degradation during cooking. Fillets treated with CRSC at lesser or greater levels of inhibitory activity than those of BPP exhibited lesser or higher protection, accordingly. As revealed by SDS-PAGE, the outer portion of fillets soaked with inhibitory solutions was more effectively protected than the inner portion. Such differences between the outer and inner portions of the fillets were not evident when inhibitory solutions were injected into the fillets.

Identification and characterization of prolylcarboxypeptidase as an endothelial cell prekallikrein activator

Our recent investigations have postulated a human umbilical vein endothelial cell (HUVEC)-associated prekallikrein activator (PKA). When prekallikrein (PK) assembles on high molecular weight kininogen on HUVEC, PK is activated to kallikrein. PKA was found in the 15,800 x g pellet of HUVEC lysates using an assay that measures PK activation only when bound to high molecular weight kininogen linked to microtiter plates. Sequential DEAE, wheat germ lectin affinity, and hydroxyapatite chromatography resulted in four protein bands on SDS-PAGE. One protein in the 73-kDa band was identified by amino acid sequencing as prolylcarboxypeptidase (PRCP). On gel filtration, PKA activity was a single homogenous peak identical in migration to the 73-kDa immunoblot of PRCP. Anti-PRCP inhibits PKA activity and PK activation on HUVEC. Purified PKA was blocked by diisopropyl fluorophosphate (1 mm), phenylmethylsulfonyl fluoride (3 mm), leupeptin (100 microm), antipain (IC(50) = 2 microm), HgCl(2) (IC(50) = 500 microm), Z-Pro-Pro-aldehyde-dimethyl acetate (IC(50) = 1 microm), and corn trypsin inhibitor (IC(50) = 40 nm). PKA did not correct the coagulant defect in factor XII deficient plasma, was purified from HUVEC cultured in factor XII-deficient serum, was not detected by antibody to factor XII, did not activate FXI, and was not inhibited by a neutralizing antibody to FXII. Angiotensin II (IC(50) = 2 microm) or bradykinin (IC(50) = 100 microm), but not angiotensin II-(1-7) or bradykinin(1-5), and the prolyl oligopeptidase inhibitor Fmoc-Ala-Pyr-CN (IC(50) = 50 nm) also blocked purified PKA activation of PK. The K(m) of PK activation by PRCP is 6.7 nm. PRCP antigen is present on the membrane of fixed but not permeabilized HUVEC. PRCP appears to be a HUVEC-associated PK activator.

The search for a new model structure of beta-factor XIIa

We present the search for a new model of beta-factor XIIa, a blood coagulation enzyme, with an unknown experimental 3D-structure. We decided to build not one but three different models using different homologous proteins as well as different techniques and different modelers. Additional studies, including extensive molecular dynamics simulations on the solvated state, allowed us to draw several conclusions concerning homology modelling, in general, and beta-factor XIIa, in particular.

Factor XII Tenri, a Novel Cross-Reacting Material Negative Factor XII Deficiency, Occurs Through a Proteasome-Mediated Degradation

A homozygous cross-reacting material negative factor XII-deficient patient with 3% antigen and activity levels of factor XII was screened for the identification of a mutation at the genomic level. Low-ionic strength single-stranded conformation polymorphism (SSCP) analysis and sequence analysis showed that the proband’s gene for factor XII had an A→G substitution at nucleotide position 7832 in exon 3, resulting in a Tyr34 to Cys substitution in the NH2-terminal type II domain of factor XII. We designated this mutation as factor XII Tenri. Mutagenic polymerase chain reaction (PCR), followed by KpnI digestion, showed a homozygous mutation in the proband’s gene and heterozygous mutations in his parents and sister. Immunoprecipitation and Western blot analyses of plasma samples from the factor XII Tenri family indicated that the proband had a trace amount of variant factor XII with an apparent molecular mass of 115 kD, which was converted to the normal 80-kD form after reduction, suggesting that factor XII Tenri was secreted as a disulfide-linked heterodimer with a ≈35-kD protein, which we identified as 1-microglobulin by immunoblotting. Pulse-chase experiments using baby hamster kidney (BHK) cells showed that Tenri-type factor XII was extensively degraded intracellularly, but the addition of cystine resulted in increased secretion of the mutant. Using membrane-permeable inhibitors, we observed that the degradation occurred in the pre-Golgi, nonlysosomal compartment and a proteasome appeared to play a major role in this process. On the basis of these in vitro results, we speculate that the majority of the factor XII Tenri is degraded intracellularly through a quality control mechanism in the endoplasmic reticulum (ER), and a small amount of factor XII Tenri that formed a disulfide-linked heterodimer with 1-microglobulin is secreted into the blood stream.

Factor XII Tenri, a Novel Cross-Reacting Material Negative Factor XII Deficiency, Occurs Through a Proteasome-Mediated Degradation

A homozygous cross-reacting material negative factor XII-deficient patient with 3% antigen and activity levels of factor XII was screened for the identification of a mutation at the genomic level. Low-ionic strength single-stranded conformation polymorphism (SSCP) analysis and sequence analysis showed that the proband’s gene for factor XII had an A→G substitution at nucleotide position 7832 in exon 3, resulting in a Tyr34 to Cys substitution in the NH2-terminal type II domain of factor XII. We designated this mutation as factor XII Tenri. Mutagenic polymerase chain reaction (PCR), followed by KpnI digestion, showed a homozygous mutation in the proband’s gene and heterozygous mutations in his parents and sister. Immunoprecipitation and Western blot analyses of plasma samples from the factor XII Tenri family indicated that the proband had a trace amount of variant factor XII with an apparent molecular mass of 115 kD, which was converted to the normal 80-kD form after reduction, suggesting that factor XII Tenri was secreted as a disulfide-linked heterodimer with a ≈35-kD protein, which we identified as 1-microglobulin by immunoblotting. Pulse-chase experiments using baby hamster kidney (BHK) cells showed that Tenri-type factor XII was extensively degraded intracellularly, but the addition of cystine resulted in increased secretion of the mutant. Using membrane-permeable inhibitors, we observed that the degradation occurred in the pre-Golgi, nonlysosomal compartment and a proteasome appeared to play a major role in this process. On the basis of these in vitro results, we speculate that the majority of the factor XII Tenri is degraded intracellularly through a quality control mechanism in the endoplasmic reticulum (ER), and a small amount of factor XII Tenri that formed a disulfide-linked heterodimer with 1-microglobulin is secreted into the blood stream.

Elucidation of the core residues of an epitope using membrane-based combinatorial peptide libraries

Combinatorial peptide libraries have proved to be a valuable tool for the study of the interaction of a functional protein with its ligand. Here, the epitope for a monoclonal antibody 201/9, raised against beta-factor XIIa, has been identified with a two-step approach using peptide libraries attached to a polymer (polyvinylidene difluoride) membrane. First, the octapeptide libraries with two amino acids defined at position 2 and 4, represented by the formula X-O2-X-O4-X-X-X-X, were synthesized on a sheet of polymer membrane in which X represents a mixture of all the natural -amino acids except cysteine, while O2 and O4 each represent a single amino acid. The libraries were probed with the antibody 201/9, and the bound antibody was detected with a sensitive chemiluminescent method. In the first cycle, the peptide mixtures X-Phe-X-Gln-X-X-X-X showed the strongest signal development. In the second cycle Phe and Gln were incorporated into new libraries consisting of sequences O1-Phe-X-Gln-X-X-X-X, X-Phe-O3-Gln-X-X-X-X, X-Phe-X-Gln-O5-X-X-X, X-Phe-X-Gln-X-O6-X-X, X-Phe-X-Gln-X-X-O7-X, and X-Phe-X-Gln-X-X-X-O8. After probing these new peptides, the residues representing the core sequence of the epitope for monoclonal antibody 201/9 were elucidated. The sequence Ser-Phe-Leu-Gln-Glu-Asn, identified as the immunodominant epitope, correlates well with the sequence Ser-Phe-Leu-Gln-Glu-Ala previously identified (Gao, B., and Esnouf, M. P. (1996) J. Immunol. 157, 183-188) in a scan of overlapping peptides based on the sequence of human beta-factor XIIa.

Explicit constants for the dextran-sulfate-mediated activation and autoactivation of purified human factor XII (Hageman factor)

The autoactivation kinetics of purified factor XII (FXII) in the presence of dextran sulfate of 500000 Da was reexamined assuming the existence of two preceding activation steps. Kinetics were numerically simulated by using rate and equilibrium constants related to surface-bound species. Relevant feature parameters related to the polymer (number of binding sites and concentration, dissociation constant of FXII from the surface) and the zymogen (concentration. Michaelis-Menten constant of the autoactivation reaction, catalytic rate constant) were accordingly introduced in the mechanisms. Depending on the rate-limiting step i.e. whether the polymer or FXII predominates, numerical simulation analysis led to obtain for the observed autoactivation rate constant (kobs) two explicit expressions which included the contributing variables. One of the two proposed models was in good accordance with the experimental data obtained in this study and with others published previously. We were able to estimate the mean number of the FXII-activating sites supported by the polymer chains (220) and the equilibrium dissociation constant of FXII from the surface (1 microM). Further treatment led us to determine surface-concentration-independent constants (K(m) = 2510 nM and kcat = 0.01 s-1), as well as the rate constant (k1 = 1.6 x 10(-4) s-1) of the postulated first-order activation rate aimed at explaining the formation of the first trace amounts of FXIIa via an intramolecular mechanism. Overall, the treatment applied to the dextran sulfate case offers a quantitative tool by which data determined in the presence of other activating materials can be rationalized.

An enzyme-linked immunosorbent assay (ELISA) for the measurement of activated factor XII (Hageman factor) in human plasma

A direct enzyme-linked immunosorbent assay (ELISA) employing 2/215 mouse monoclonal hybridoma antibody is described. The assay is capable of detecting activated factor XII in human plasma and can be used to assess early detection of the intrinsic blood coagulation pathway. No cross reactivity with human factor XII zymogen has been found. The assay was used to assess activation of factor XII in patients with renal failure, pregnancy and diabetes compared to a control group.

Inhibition of prekallikrein activation in human plasma by components of bovine plasma

Contact of plasma with a negatively charged surface activates prekallikrein and factor XII reciprocally. Activation of prekallikrein by several activators was impaired in bovine plasma when compared to that in human plasma. The activated partial thromboplastin time of bovine plasma, induced by several activators, was significantly longer than that of human plasma. Cleavage of [125I]factor XII was optimum at 10 min in human plasma but took up to 60 min in bovine plasma. Addition of bovine plasma to human plasma caused significant inhibition of dextran sulfate-induced prekallikrein activation, indicating that the impaired rate of contact activation in bovine plasma is due to the presence of inhibitors. The inhibitory effect was greater at lower concentrations of dextran sulfate but could not be abolished by increasing the concentration. The inhibitory activity eluted in two peaks at low and medium salt concentrations on carboxymethyl ion-exchange chromatography of bovine plasma.

Autoactivation of human blood coagulation factor XII on dextran derivatives of different molecular weight

We prepared a derivative of dextran T40 (average M(r) 43,000) from which fractions of different M(r) but with equal charge density were obtained and tested for their ability to promote autoactivation of human blood coagulation factor XII. The mechanism of autoactivation appeared dependent upon the M(r) of the polymer used. Thus, with polymers of 38,000 M(r) or higher only alpha-factor XIIa was formed and the reaction could be completely described in terms of a simple second-order mechanism of autoactivation. With smaller polymer molecules beta-factor XIIa became a major reaction product and as a result of this the autoactivation kinetics did not adhere to the second-order mechanisms thus far described.

Activation mechanism of human Hageman factor-plasma kallikrein-kinin system by Vibrio vulnificus metalloprotease

Vivrio vulnificus, an opportunistic human pathogen, secretes a metalloprotease (VVP). The VVP inoculated into a guinea pig is known to generate bradykinin through activation of the Hageman factor-plasma kallikrein-kinin system. VVP was shown to possess the ability to activate the human system through the same mechanism as that clarified in the guinea pig system, namely, VVP converted both human zymogens (Hageman factor and plasma prekallikrein) to active enzymes (activated Hageman factor and plasma kallikrein), and the then generated kallikrein liberated bradykinin from high-molecular-weight kininogen. However, in the presence of plasma alpha 2-macroglobulin (alpha 2M), the VVP action was drastically decreased. This finding suggests that the human system might be activated only at the interstitial-tissue space which contains negligible amounts of alpha 2M or in the bloodstream of the individuals whose plasma alpha 2M level is extremely reduced.

Prekallikrein activation in human, bovine, and rabbit plasmas: presence of an inhibitor in bovine plasma

Contact of human plasma with a negatively charged surface such as dextran sulfate activates prekallikrein to kallikrein, which releases the vasoactive peptide bradykinin from high-molecular-weight kininogen. The dextran sulfate-induced activation of prekallikrein at 0 degree C (assayed by its amidolytic activity on the chromogenic substate S-2302) could not be observed in either bovine or rabbit plasmas when compared to human plasma. Neither bovine nor rabbit plasma inhibited the amidolytic activity of contact-activated human plasma at 0 degrees C. The activation of prekallikrein in human plasma was significantly inhibited by the addition of bovine plasma but not by rabbit plasma. Bovine plasma (0.025 units, 1 unit = 1 ml of plasma) caused 68.8% inhibition of prekallikrein activation. Eighty percent of the inhibitory property of bovine plasma was present in the greater than 30,000-molecular-weight fraction. These results indicate the presence of an inhibitor(s) of prekallikrein activation in bovine plasma.

Model structure for the human blood coagulation agent beta-factor XIIa

An improvement to the human blood coagulation agent beta-factor XIIa three-dimensional model is proposed. The sequence alignment as well as the modeling procedures are presented and the minimized energy of the new model is reported before and after solvation of the active center.

Kinin-generating cascade in advanced cancer patients and in vitro study

The role of the bradykinin-generating system in the pathogenesis of cancer was explored by simultaneously measuring plasma prekallikrein (PK), the precursor of kallikrein, which is the major enzyme responsible for kinin generation, and plasma kininogens (KNG), which are precursors of kinin, in patients with various cancers. The mean value of plasma PK in healthy volunteers was 2.5 +/- 0.5 (mean +/- SD) units/mg plasma protein and that in cancer patients (all stage IV) was 1.7 +/- 0.7 units/mg plasma protein. The mean value of plasma KNG in healthy volunteers was 12.5 +/- 2.0 ng kinin equivalents/mg plasma protein and that in cancer patients was 10.9 +/- 2.8 ng. These data showed that plasma PK and plasma KNG values were significantly lower in cancer patients compared with healthy volunteers (P less than or equal to 0.005 for PK; 0.0005 less than P less than or equal to 0.005 for KNG; n = 28 for healthy subjects; n = 29 for cancer patients). These data appear to indicate that conversion of PK to kallikrein would probably occur with concomitant consumption of KNG by newly generated kallikrein for kinin generation in cancer patients. Early stage cancer patients showed little difference from healthy volunteers. For the in vitro study, activation of purified Hageman factor (HF) and PK was examined by using cancer cell lines and virus-transformed cells that produced plasminogen activator (PA) at a high rate. Both HF and PK were activated in the presence of plasminogen. Diploid cell lines and primary fibroblasts, which did not produce PA, activated neither HF nor PK. Taking all these data together, we conclude that kinin generation does occur in the plasma of patients with advanced cancer, and that one of the initiation mechanisms of the kinin-generating cascade appears to be mediated by plasmin and to depend on cancer cell-derived PA activity.

Triggering of the vascular permeability reaction by activation of the Hageman factor-prekallikrein system by house dust mite proteinase

A 30-kilodalton (kDa) proteinase from the house dust mite Dermatophagoides farinae (Df-proteinase) was recently purified (Takahashi et al. (1990) Int. Arch. Allergy Appl. Immunol. 91, 80-85). In this paper we detailed the biological activities of the Df-proteinase. The activation of the kinin cascade by Df-proteinase was examined in vitro by using purified guinea pig Hageman factor (HF), prekallikrein (PK) and high-molecular-weight kininogen (HMWK) and the effect of this proteinase on endogenous human plasma proteinase inhibitors (serpins) and alpha 2-macroglobulin was tested. In addition, enhancement of the vascular permeability reaction in guinea pig skin by Df-proteinase was examined in vivo. These experiments showed that Df-proteinase could activate all the steps of the kinin-generating cascade, i.e., HF, PK and HMWK, and that Df-proteinase retained proteolytic activity even in the presence of an excess amount of endogenous proteinase inhibitors in plasma. We also found that the marked enhancement of the vascular permeability reaction was induced by Df-proteinase via the activation of the kinin-generating cascade without the release of histamine. From these results, we conclude that the proteinase of the house dust mite, Df-proteinase, has the potential to generate bradykinin and that the presence of this proteinase in biological systems would exacerbate inflammatory reactions in some pathological conditions.

Mitogenic effects of coagulation factor XII and factor XIIa on HepG2 cells

The structure of coagulation factor XII (Hageman factor), inferred from its DNA sequence, includes two epidermal growth factor (EGF)-homologous domains in its amino-terminal region. This suggests that factor XII may exhibit EGF-like activities. Reciprocal antigenic cross-reactivity between factor XII and EGF was shown by exposing purified human factor XII or mouse EGF to anti-mouse EGF or anti-human factor XII. Western blot analysis showed that anti-mouse EGF recognized intact factor XII at 80 kDa. Together, these results suggest that the EGF-homologous domains are accessible for anti-EGF binding in native factor XII. To determine whether factor XII has mitogenic activity, HepG2 or L cells (10(4) cells per well) were grown in serum-free medium in the presence or absence of factor XII or kaolin-activated factor XII (factor XIIa). Both factors XII and XIIa (6.0 micrograms/ml) enhanced cell proliferation by approximately 2-fold (P less than 0.001 and P less than 0.005, respectively). In contrast, L cells, which are not EGF target cells, were not affected by either factor XII or factor XIIa. Various doses of factor XII enhanced cell proliferation, [3H]thymidine incorporation, and [3H]leucine incorporation in HepG2 cells cultured under the same conditions. These data indicate that factor XII, like EGF, is a mitogen for HepG2 cells and suggest a possible autocrine role in the liver.

The inositol-phospholipid-accelerated activation of prekallikrein by activated factor XII at physiological ionic strength requires zinc ions and high-Mr kininogen

In a system consisting of purified proteins inositol-phospholipid-accelerated activation of prekallikrein by alpha-factor XIIa was determined by measuring the appearance of kallikrein amidolytic activity towards the chromogenic substrate, H-D-Pro-Phe-Arg-NH-PhNO2 (PhNO2, 4-nitrophenyl). The activation reaction was ionic-strength dependent. In the absence of high-Mr kininogen optimal activity was recorded at I = 50 mM. Searching for conditions, which could change this optimum towards physiological values, high-Mr kininogen was added. This resulted in an inhibition of the activity, with no change in ionic strength optimum. If, however, Zn2+ were added concomitant with high-Mr kininogen, the inhibition was abolished and optimal activity recorded at physiological ionic strength. The optimal Zn2+ concentration was found to be 0.1 mM. Kinetic analysis of the reaction demonstrated that the kcat/Km was 1.2 x 10(5) M-1 s-1 in the absence and 1.1 x 10(6) M-1 s-1 in the presence of Zn2+. Zn2+ were also required for inositol-phospholipid-accelerated initiation of the contact activation in whole plasma.

A quantitative dot immunobinding assay for coagulation factor XII in plasma

A dot immunobinding assay on nitrocellulose (NC) membranes has been developed for the quantification of human coagulation factor XII (F XII). Plasma samples were dotted on to NC filters and F XII was detected using a polyclonal antiserum followed by a radiolabelled antigen overlay. Dilutions of either pooled normal human plasma (NHP) or purified F XII in F XII deficient plasma were used as standards. Quantification was performed by measuring the radioactivity of bound 125I-F XII. Precise measurements of F XII antigen (F XII: Ag) were possible with a sensitivity down to 0.12 ng. Thus, dotting samples containing 0.5 microliter of plasma permitted detection of a F XII concentration corresponding to 1% of the level in NHP. The intra-assay coefficient of variation (CV) was less than 5% and the interassay CV was less than 16%. F XII:Ag in plasma samples of 50 healthy adults ranged from 12 micrograms/ml to 47 micrograms/ml. A good correlation (r = 0.93) existed between F XII:Ag and F XII clot promoting activity (F XII:C) in these samples. NHP contained 24.1 micrograms/ml F XII:Ag confirming earlier results obtained by other methods. In 16 pregnant women levels of F XII:Ag as well as of F XII:C were elevated, but F XII:Ag was disproportionately higher compared with F XII:C. The immunobinding assay has the following advantages: (1) rapid quantification of large numbers of samples is possible, (2) the sensitivity down to 1% of NHP is better than that of several other methods, (3) only very small amounts of both test material and reagents are needed.

Activation of human Hageman factor by Pseudomonas aeruginosa elastase in the presence or absence of negatively charged substance in vitro

Human Hageman factor, a plasma proteinase zymogen, was activated in vitro under a near physiological condition (pH 7.8, ionic strength I = 0.14, 37 degrees C) by Pseudomonas aeruginosa elastase, which is a zinc-dependent tissue destructive neutral proteinase. This activation was completely inhibited by a specific inhibitor of the elastase, HONHCOCH(CH2C6H5)CO-Ala-Gly-NH2, at a concentration as low as 10 microM. In this activation Hagemen factor was cleaved, in a limited fashion, liberating two fragments with apparent molecular masses of 40 and 30 kDa, respectively. The appearance of the latter seemed to correspond chronologically to the generation of activated Hageman factor. Kinetic parameters of the enzymatic activation were kcat = 5.8 x 10(-3) s-1, Km = 4.3 x 10(-7) M and kcat/Km = 1.4 x 10(4) M-1 x s-1. This Km value is close to the plasma concentration of Hageman factor. Another zinc-dependent proteinase, P. aeruginosa alkaline proteinase, showed a negligible Hageman factor activation. In the presence of a negatively charged soluble substance, dextran sulfate (0.3-3 micrograms/ml), the activation rate by the elastase increased several fold, with the kinetic parameters of kcat = 13.9 x 10(-3) s-1, Km = 1.6 x 10(-7) M and kcat/Km = 8.5 x 10(4) M-1 x s-1. These results suggested a participation of the Hageman factor-dependent system in the inflammatory response to pseudomonal infections, due to the initiation of the system by the bacterial elastase.

Expression and purification of biologically active v-sis/platelet-derived growth factor B protein by using a baculovirus vector system

Malignant transformation induced by simian sarcoma virus is mediated by its v-sis protein, the monkey homolog of the platelet-derived growth factor (PDGF) B chain. By use of an appropriately engineered baculovirus expression vector, the v-sis protein was expressed in the insect cell line Spodoptera frugiperda (Sf9) at a level 50- to 100-fold higher than that observed with overexpression in mammalian-cell transfectants. The sis protein produced by Sf9 cells underwent processing similar to that observed in mammalian cells, including efficient disulfide-linked dimer formation. Moreover, the recombinant sis protein was capable of binding PDGF receptors and inducing DNA synthesis as efficiently as PDGF-B synthesized by mammalian cells. A significant fraction of sis protein was released from Sf9 cells, which made possible a one-step immunoaffinity purification to near homogeneity with a 40% recovery of biological activity. These results demonstrate that a protein whose normal processing requires both intrachain and interchain disulfide-bridge formation can be efficiently expressed in a biologically active form in insect cells by using a baculovirus vector system.

Inositolphospholipid-accelerated activation of prekallikrein by activated factor XII and its inhibition by beta 2-glycoprotein I

Inositolphospholipid-accelerated activation of prekallikrein by alpha-factor XIIa was determined by measuring the appearance of kallikrein amidolytic activity towards the chromogenic substrate, D-prolyl-phenylalanyl-arginyl p-nitroanilide (S-2302). The activation reaction did not exhibit normal Michaelis-Menten kinetics. The Hill coefficient was found to be 1.6 indicating that the activation followed an allosteric reaction mechanism. The temperature dependence of the reaction showed a thermal transition at 30 degrees C, which in addition to the allosteric reaction mechanism is indicative of a conformational change of prekallikrein following binding to the inositolphospholipid. The reaction exhibited pH optimum at pH 7.2 and ionic strength optimum at 50 mM NaCl. At optimal conditions the apparent KA value and the kcat/KA value for factor XIIa on prekallikrein were calculated to be 73 nM and 9.3 x 10(6) s-1 M-1, respectively. Kinetic constants could not be calculated at salt concentrations higher than the optimal concentrations, as Lineweaver-Burk plots were curvilinear in agreement with the Hill coefficient greater than unity. The activation was inhibited competitively by beta 2-glycoprotein I with a Ki value of 77 nM as determined by the Dixon plot.

Structural gene encoding human factor XII is located at 5q33-qter

The gene encoding human factor XII (F12) or Hageman factor has been mapped to 5q33-qter. This has been achieved by analyzing the results obtained from hybridizing a cloned fragment from the factor XII gene to a panel of human-hamster somatic cell hybrid DNAs and also by in situ hybridization to normal human metaphase cells. The previously reported results localizing F12 to 6p23 are discussed.

Intrinsic versus extrinsic coagulation. Kinetic considerations

A study to compare the kinetics of activation of factor IX by Factor XIa/Ca2+ and by Factor VIIa/tissue factor/Ca2+ has been undertaken. When purified human proteins, detergent-extracted brain tissue factor and tritiated-activation-peptide-release assays were utilized, the kinetic constants obtained were: Km = 310 nM, kcat. = 25 min-1 for Factor XIa and Km = 210 nM, kcat. = 15 min-1 for Factor VIIa. The kinetic constants for the activation of Factor X by Factor VIIa/brain tissue factor were: Km = 205 nM, kcat. = 70 min-1. Predicted rates for the generation of Factor IXa and Factor Xa were obtained when human monocytic tumour U937 cells (source of tissue factor) and Factor VIIa were used to form the activator. In other experiments, inclusion of high-Mr kininogen did not increase the activation rates of Factor IX by Factor XIa in the presence or absence of platelets and/or denuded rabbit aorta. These kinetic data strongly indicate that both Factor XIa and Factor VIIa play physiologically significant roles in the activation of Factor IX.

Possible basis for the apparent surface selectivity of the contact activation of human blood coagulation factor XII

The activation of factor XII by the proteases factor XIIa and kallikrein is known to be greatly enhanced by certain negatively charged surfaces. Studies that compared factor XII surface binding to factor XII activation found that binding alone was insufficient to account for surface enhancement of the activation rate. The temperature dependence of the reaction showed unusual behavior that may be related to the conformational change of factor XII following binding; the rate of factor XII activation had a relatively low temperature optimum (0-47 degrees C) that was sensitive to choice of surface and salt concentration. In temperature studies, below 47 degrees C, the decrease in the activation rate was not related to the thermal denaturation of enzyme or substrate, nor to the choice of activator enzyme (factor XIIa or kallikrein), nor to the species of factor XII (human or bovine) but to a behavior, designated a thermal transition, associated with the surface or the protein-surface interaction. The previously reported surface selectivity of contact activation is possible due to the temperature characteristics and other properties of the thermal transition; a surface that has a low-temperature thermal transition and that is highly sensitive to salt will be a "poor" contact surface under the usual choice of reaction conditions (approximately 150 mM ionic strength and 37 degrees C). However, solution conditions were identified that allowed the following negatively charged surfaces to function, in nearly equal potency, in the activation of factor XII: phosphatidylserine, phosphatidylglycerol, phosphatidic acid, phosphatidylinositol 4-phosphate, heparin, and 5-kDa dextran sulfate, as well as the previously characterized sulfatide and 500-kDa dextran sulfate.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid sequence of human factor XI, a blood coagulation factor with four tandem repeats that are highly homologous with plasma prekallikrein

A lambda gtll cDNA library prepared from human liver poly(A) RNA has been screened with affinity-purified antibody to human factor XI, a blood coagulation factor composed of two identical polypeptide chains linked by a disulfide bond(s). A cDNA insert coding for factor XI was isolated and shown to contain 2097 nucleotides, including 54 nucleotides coding for a leader peptide of 18 amino acids and 1821 nucleotides coding for 607 amino acids that are present in each of the 2 chains of the mature protein. The cDNA for factor XI also contained a stop codon (TGA), a potential polyadenylation or processing sequence (AACAAA), and a poly(A) tail at the 3' end. Five potential N-glycosylation sites were found in each of the two chains of factor XI. The cleavage site for the activation of factor XI by factor XIIa was identified as an internal peptide bond between Arg-369 and Ile-370 in each polypeptide chain. This was based upon the amino acid sequence predicted by the cDNA and the amino acid sequence previously reported for the amino-terminal portion of the light chain of factor XI. Each heavy chain of factor XIa (369 amino acids) was found to contain 4 tandem repeats of 90 (or 91) amino acids plus a short connecting peptide. Each repeat probably forms a separate domain containing three internal disulfide bonds. The light chains of factor XIa (each 238 amino acids) contain the catalytic portion of the enzyme with sequences that are typical of the trypsin family of serine proteases. The amino acid sequence of factor XI shows 58% identity with human plasma prekallikrein.

Characterization of a cDNA coding for human factor XII (Hageman factor)

Affinity-purified antibody against human factor XII (Hageman factor) has been radiolabeled with 125I and employed as a probe to screen a human liver cDNA expression library prepared in lambda gt11. Approximately 3.5 X 10(6) recombinant phages were screened for factor XII, and two positive clones were identified and plaque purified. The largest cDNA coding for factor XII was 1571 base pairs in length and coded for amino acid residues 127-596 in the mature protein, a termination codon of TGA, a 3' noncoding sequence of 147 nucleotides, and a poly(A) tail of 11 nucleotides. The second clone contained an insert of 1334 base pairs and coded for amino acid residues 200-596. The amino acid sequence predicted by the cDNAs was in excellent agreement with that previously determined by amino acid sequence analysis. The amino acid and DNA sequences in human factor XII showed considerable homology with the corresponding domains in other serine proteases, including prothrombin, plasminogen, tissue plasminogen activator, and urokinase.

Proteolytic activation of tissue plasminogen activator by plasma and tissue enzymes

Tissue kallikrein and factor Xa were found to activate tissue plasminogen activator (t-PA) at a rate comparable with that of plasmin. During the activation reaction, the single-chain molecule was converted into a two-chain form. A slight t-PA activating activity was also found in plasma kallikrein. Other activated coagulation factors, factor XIIa, factor XIa, factor IXa, factor VIIa, thrombin and activated protein C had no effect on t-PA activation. t-PA was also activated by a tissue kallikrein-like enzyme that was isolated from the culture medium of melanoma cells. These results indicate that tissue kallikrein and factor Xa may participate in the extrinsic pathway of human fibrinolysis.

Use of human factor VIIa in the treatment of two hemophilia A patients with high-titer inhibitors

Two patients with hemophilia A complicated with high-titer alloantibodies have been treated by repeated infusions of microgram quantities of pure human Factor VIIa. Patient 1 was presented with a gastrocnemius muscle bleeding that involved the knee joint. Upon treatment with Factor VIIa the circumference of the muscle decreased and joint mobility increased substantially. Patient 2 was given Factor VIIa concurrent with tranexamic acid in association with the extraction of two primary molars. No significant gingival bleeding occurred after Factor VIIa and tranexamic acid treatment. Furthermore, no deleterious side effects or increase of the alloantibody level were observed in either patient throughout the Factor VIIa infusion. These results, although limited and preliminary in nature, suggest that trace quantities of Factor VIIa can act as a Factor VIII bypassing activity and restore hemostasis in these patients.