Defective glycosylation of coagulation factor XII underlies hereditary angioedema type III
Jenny Björkqvist, … , Coen Maas, Thomas Renné
Jenny Björkqvist, … , Coen Maas, Thomas Renné
Published July 20, 2015
Citation Information: J Clin Invest. 2015;125(8):3132-3146. https://doi.org/10.1172/JCI77139.
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Research Article Vascular biology

Defective glycosylation of coagulation factor XII underlies hereditary angioedema type III

Abstract

Hereditary angioedema type III (HAEIII) is a rare inherited swelling disorder that is associated with point mutations in the gene encoding the plasma protease factor XII (FXII). Here, we demonstrate that HAEIII-associated mutant FXII, derived either from HAEIII patients or recombinantly produced, is defective in mucin-type Thr309-linked glycosylation. Loss of glycosylation led to increased contact-mediated autoactivation of zymogen FXII, resulting in excessive activation of the bradykinin-forming kallikrein-kinin pathway. In contrast, both FXII-driven coagulation and the ability of C1-esterase inhibitor to bind and inhibit activated FXII were not affected by the mutation. Intravital laser-scanning microscopy revealed that, compared with control animals, both F12–/– mice reconstituted with recombinant mutant forms of FXII and humanized HAEIII mouse models with inducible liver-specific expression of Thr309Lys-mutated FXII exhibited increased contact-driven microvascular leakage. An FXII-neutralizing antibody abolished bradykinin generation in HAEIII patient plasma and blunted edema in HAEIII mice. Together, the results of this study characterize the mechanism of HAEIII and establish FXII inhibition as a potential therapeutic strategy to interfere with excessive vascular leakage in HAEIII and potentially alleviate edema due to other causes.

Authors

Jenny Björkqvist, Steven de Maat, Urs Lewandrowski, Antonio Di Gennaro, Chris Oschatz, Kai Schönig, Markus M. Nöthen, Christian Drouet, Hal Braley, Marc W. Nolte, Albert Sickmann, Con Panousis, Coen Maas, Thomas Renné

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Figure 7

Increased vascular leakage in HAEIII mice.

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Increased vascular leakage in HAEIII mice. (A) Inducible expression of F...
(A) Inducible expression of FXII_Thr309Lys in HEK293T cells, incubated in the presence of increasing concentrations of doxycycline (dox; 0.1–6.4 μg/ml) or buffer using a Tet-On system. FXII_Thr309Lys in supernatants was analyzed by Western blotting after 48 hours of induction. FXII and FXII_Thr309Lys were loaded as controls. n = 3. (B) Transgenic FXII_Thr309Lys expression was induced in HAEIII mice (Tet-Off system) by dox withdrawal (–) and suppressed by dox (+). Plasma samples from induced (–dox) and noninduced (+dox) HAEIII mice (muHAEIII) were analyzed by Western blotting using a human anti-FXII antibody that does not crossreact with the mouse orthologue. Plasma samples from a HAEIII patient (huHAEIII), a healthy individual (NP), a WT mouse, and HEK293T cell–expressed FXII_Thr309Lys were loaded for comparison. (C) Extravasation of FITC-dextran tracer from murine dorsal skin microvessels was recorded by intravital laser-scanning fluorescence microscopy in real time. DXS was topically applied to the inverted skin of either noninduced (+dox; not expressing FXII_ Thr309Lys) or induced (–dox; expressing FXII_ Thr309Lys) HAEIII mice (columns 1 and 2). HAEIII mice expressing FXII_Thr309Lys were injected with DX-88 (430 μg/kg bw) or 3F7 (7 mg/kg bw) 30 minutes before FITC-dextran application (columns 3 and 4). Laser-scanning images were taken at 10 and 20 minutes after stimulation by topical application of DXS to skin microvessels at time point 0 minutes and are shown in false colors. White represents the highest and black the lowest tracer intensity. Scale bar: 500 μm. n = 4 per group.