The plasma von Willebrand factor O‐glycome comprises a surprising variety of structures including ABH antigens and disialosyl motifs

Background: von Willebrand factor (VWF) is a key component for maintenance of normal hemostasis. Its glycan moieties, accounting for about 20% of its molecular weight, have been shown to affect many of its properties. Previous studies reported correlations between VWF secretion, half‐life and the nature or presence of its N‐glycans, and more importantly between VWF plasma level and the type of N‐linked ABH antigens. Despite the presence of 10 predicted O‐glycosylation sites, the O‐glycome remains poorly characterized, impairing the complete elucidation of its influence on VWF functions. So far only a single glycan structure, a disialyl core 1 glycan, has been identified. Objectives: To define an exhaustive profile of the VWF O‐glycan structures to help the understanding of their role in VWF regulation and properties. Methods: Plasma‐derived VWF O‐linked sugars were isolated and analyzed using state‐of‐the‐art mass spectrometry methodologies. Results and conclusions: We provide here a detailed analysis of the human plasma‐derived VWF O‐glycome. Eighteen O‐glycan structures including both core 1 and core 2 structures are now demonstrated to be present on VWF. Amongst the newly determined structures are unusual tetra‐sialylated core 1 O‐glycans and ABH antigen‐containing core 2 O‐glycans. In conjunction with current models explaining VWF activity, knowledge of the complete O‐glycome will facilitate research aimed at providing a better understanding of the influence of glycosylation on VWF functions.