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  • A novel role for the macrop...
    Ward, Soracha E.; O'Sullivan, Jamie M.; Drakeford, Clive; Aguila, Sonia; Jondle, Christopher N.; Sharma, Jyotika; Fallon, Padraic G.; Brophy, Teresa M.; Preston, Roger J.S.; Smyth, Paul; Sheils, Orla; Chion, Alain; O'Donnell, James S.

    Blood, 02/2018, Letnik: 131, Številka: 8
    Journal Article

    Previous studies have shown that loss of terminal sialic acid causes enhanced von Willebrand factor (VWF) clearance through the Ashwell-Morrell receptor (AMR). In this study, we investigated (1) the specific importance of N- vs O-linked sialic acid in protecting against VWF clearance and (2) whether additional receptors contribute to the reduced half-life of hyposialylated VWF. α2-3-linked sialic acid accounts for <20% of total sialic acid and is predominantly expressed on VWF O-glycans. Nevertheless, specific digestion with α2-3 neuraminidase (α2-3Neu-VWF) was sufficient to cause markedly enhanced VWF clearance. Interestingly, in vivo clearance experiments in dual VWF−/−/Asgr1−/− mice demonstrated enhanced clearance of α2-3Neu-VWF even in the absence of the AMR. The macrophage galactose-type lectin (MGL) is a C-type lectin that binds to glycoproteins expressing terminal N-acetylgalactosamine or galactose residues. Importantly, the markedly enhanced clearance of hyposialylated VWF in VWF−/−/Asgr1−/− mice was significantly attenuated in the presence of an anti-MGL inhibitory antibody. Furthermore, dose-dependent binding of human VWF to purified recombinant human MGL was confirmed using surface plasmon resonance. Additionally, plasma VWF:Ag levels were significantly elevated in MGL1−/− mice compared with controls. Collectively, these findings identify MGL as a novel macrophage receptor for VWF that significantly contributes to the clearance of both wild-type and hyposialylated VWF. •VWF sialylation modulates in vivo clearance through Ashwell-Morrell independent pathways.•VWF binding to MGL plays a novel role in facilitating VWF clearance. Display omitted