A monoclonal antibody recognizing an icosapeptide sequence in the heavy chain of human factor XII inhibits surface-catalyzed activation.

Pixley, Robin A.; Stumpo, L G; Birkmeyer, K.; Silver, Lee D.; Colman, Robert W.

doi:10.1016/s0021-9258(18)61089-0

Cited by 52 publications

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“…Human studies show enzymatic inhibition properties using both agents. 16,28 When the purified and concentrated fractions of FXII protein from normal cats were added to a homozygous cat plasma pool, the APTT was corrected to near-normal values (from >200 seconds corrected to 33.6-43.1 seconds), indicating that the purified FXII was intact and active (data not shown). Testing of the mutant factor XII protein isolated from deficient cat plasma revealed no correction of the APTT (>200 after adding purified mutant FXII), suggesting this abnormal protein lacks FXII catalytic activity reflective of a primary defect in FXII protein (Suppl.…”

Section: Resultsmentioning

confidence: 95%

“…The prediction program Clustal omega version 1.2.0 was used to align cDNA and protein sequences.Protein Isolation and Identification TechniquesPlasma mixing studies and inhibition of feline FXII. To define the functional enzymatic activity of normal and mutant feline FXII, we performed plasma mixing studies using human prekallikrein-deficient (PKd) plasma (Sigma Diagnostics, St Louis, MO) and FXII-deficient plasma (George King Biomedicals, Overland Park, KS), corn trypsin inhibitor (CTI; Enzyme Research Laboratories, South Bend, IN), and a monoclonal mouse anti-human FXII heavy chain antibody, B7C9, directed to amino acids p.I19-V38 and p.T153-R172 of the human FXII protein5,28 (a gift from Dr Robin Pixley) with cat plasmas prior to assaying coagulant activity using the Stago ST4 and the modified APTT procedure. Human PKd plasma was used as a diluent instead of a HZY cat plasma pool to assess for a prekallikrein deficiency in our colony.…”

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Molecular Characterization of Cat Factor XII Gene and Identification of a Mutation Causing Factor XII Deficiency in a Domestic Shorthair Cat Colony

et al. 2014

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Coagulation factor XII (FXII) may be important in cardiovascular and inflammatory diseases. We have identified and characterized a naturally occurring mutation in the feline FXII gene that results in a mutant protein and enzymatic loss of activity. Feline intron/ exon gene structure and sequence were acquired by comparing DNA sequences obtained from a fragmented Felis catus genomic sequence and the National Center for Biotechnology Information's Cross Species Megablast of multiple species' FXII gene sequences. Fourteen exons ranging in size from 57 to 222 base pairs were confirmed spanning 8 Kb on chromosome A1. The 1828-base pair feline FXII messenger RNA (mRNA) sequence contains an open reading frame that encodes a protein of 609 amino acids with high homology to human FXII protein. Total RNA and mRNA purified from liver tissue of 4 wild-type/normal and 8 FXII-deficient cats confirmed the predicted mRNA sequence and identified one important single-nucleotide polymorphism (SNP). A single base deletion in exon 11 of the FXII coding gene in our colony of cats results in deficient FXII activity. Translation of the mRNA transcript shows a frame shift at L441 (C441fsX119) resulting in a nonsense mutation and a premature stop codon with a predicted 560-amino acid protein. The mutant FXII protein is truncated in the 3 0 proteolytic light chain region of the Cterminus, explaining its loss of enzymatic activity. This study is the first molecular characterization of the feline FXII gene and the first identification of an FXII mutation in the domestic cat, providing insights into the origin and nature of feline FXII deficiency.Keywords coagulation, technology, cat, domestic mammals, species, factor XII, FXII, Hageman factor, gene, mutation, mRNA Deficiency of factor XII (FXII or Hageman factor) was first described in 1955 in a human patient who lacked plasma coagulant activity. 31 In the intervening time, FXIIs from multiple species have been genetically characterized and various mutations have been reported in humans. Although FXII deficiency does not present as a bleeding tendency, recent evidence indicates FXII may be important in maintaining blood clot stability and pregnancy. 22,25,32 A feline FXII-deficient case was first described in 1977, 10 and later Kier et al 18 established a colony in the early 1980s to study FXII deficiency.Today, these offspring continue to provide information about the in vivo role of FXII and are the source of this study's molecular characterization of a mutation in the FXII gene with a similar autosomal recessive inheritance pattern and coagulation profile as seen in humans. Studies in human populations indicate that the prevalence of moderate to severe FXII deficiency is between 2% and 5% of a given white population.11 Similar to humans, the prevalence of FXII deficiency in domestic cats of the United States is 2%. 3Factor XII is primarily produced in the liver and circulates in the plasma as an inactive precursor enzyme or zymogen. 40The FXII protein is a 2-chain molecule consis...

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Section: Resultsmentioning

confidence: 95%

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confidence: 99%

Molecular Characterization of Cat Factor XII Gene and Identification of a Mutation Causing Factor XII Deficiency in a Domestic Shorthair Cat Colony

et al. 2014

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“…Previously, epitope mapping of inhibitory FXII antibodies interfering with contact activation identified several putative sites on FXII involved in surface-binding and contact activation. Monoclonal antibodies P5-2-1 and B7C9 interfered with surface-triggered FXIIa formation in plasma 39 and epitopes of these antibodies were originally mapped to residues Ile1-His28 and Thr134-Arg153 in the Fib-II and Fib-I domains of the heavy chain, respectively 40 . A follow-up study revealed that P5-2-1 and B7C9 competed with each other for FXII binding and they were both mapped to epitope Ile1-His28 41 .…”

Section: Discussionmentioning

confidence: 99%

Identification of the factor XII contact activation site enables sensitive coagulation diagnostics

et al. 2021

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Contact activation refers to the process of surface-induced activation of factor XII (FXII), which initiates blood coagulation and is captured by the activated partial thromboplastin time (aPTT) assay. Here, we show the mechanism and diagnostic implications of FXII contact activation. Screening of recombinant FXII mutants identified a continuous stretch of residues Gln317–Ser339 that was essential for FXII surface binding and activation, thrombin generation and coagulation. Peptides spanning these 23 residues competed with surface-induced FXII activation. Although FXII mutants lacking residues Gln317–Ser339 were susceptible to activation by plasmin and plasma kallikrein, they were ineffective in supporting arterial and venous thrombus formation in mice. Antibodies raised against the Gln317–Ser339 region induced FXII activation and triggered controllable contact activation in solution leading to thrombin generation by the intrinsic pathway of coagulation. The antibody-activated aPTT allows for standardization of particulate aPTT reagents and for sensitive monitoring of coagulation factors VIII, IX, XI.

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“…28 The monoclonal antibody B7C9 identified amino acids 134-153 as a part of the Fib-I domain as potential polyanionic surface binding site. 29 Furthermore, anti-FXII antibody KOK5 that recognizes a discontinuous epitope in the Fib-II domain involving residues 30-33, 40-47, and 57-60 inhibits kaolin-triggered FXII contact system activation. 30 However, a 319-amino-acids-deleted FXII mutant, rFXII.lpc, that consists of the light chain and the C-terminal part of the PR region but lacks the entire KOK5 epitope, binds to kaolin and is activated by the anionic surface.…”

Section: Fxii: Domains and Their Functionsmentioning

confidence: 99%

Mechanism, Functions, and Diagnostic Relevance of FXII Activation by Foreign Surfaces

2021

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Factor XII (FXII) is a serine protease zymogen produced by hepatocytes and secreted into plasma. The highly glycosylated coagulation protein consists of six domains and a proline-rich region that regulate activation and function. Activation of FXII results from a conformational change induced by binding (“contact”) with negatively charged surfaces. The activated serine protease FXIIa drives both the proinflammatory kallikrein–kinin pathway and the procoagulant intrinsic coagulation cascade, respectively. Deficiency in FXII is associated with a prolonged activated partial thromboplastin time (aPTT) but not with an increased bleeding tendency. However, genetic or pharmacological deficiency impairs both arterial and venous thrombosis in experimental models. This review summarizes current knowledge of FXII structure, mechanisms of FXII contact activation, and the importance of FXII for diagnostic coagulation testing and thrombosis.

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A monoclonal antibody recognizing an icosapeptide sequence in the heavy chain of human factor XII inhibits surface-catalyzed activation.

Cited by 52 publications

References 31 publications

Molecular Characterization of Cat Factor XII Gene and Identification of a Mutation Causing Factor XII Deficiency in a Domestic Shorthair Cat Colony

Molecular Characterization of Cat Factor XII Gene and Identification of a Mutation Causing Factor XII Deficiency in a Domestic Shorthair Cat Colony

Identification of the factor XII contact activation site enables sensitive coagulation diagnostics

Mechanism, Functions, and Diagnostic Relevance of FXII Activation by Foreign Surfaces

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