Submitted June 29, 2006
Accepted November 1, 2006
Variations in glycosylation of von Willebrand factor with
O-linked sialylated T-antigen are associated with its plasma levels
Carina JM van Schooten, Cecile V Denis, Ton Lisman, Jeroen CJ Eikenboom, Frank W Leebeek, Jenny Goudemand, Edith Fressinaud, Marijke van den Berg, Philip G de Groot, and Peter J. Lenting*
University Medical Center Utrecht, Netherlands
Universite Paris-Sud, France
Leiden University Medical Center, Netherlands
Erasmus University Medical Center, Netherlands
Medical University of Lille, Hopital Cardiogique, France
Centre Hospitalier Universitaire, France
* Corresponding author; email: p.j.lenting{at}umcutrecht.nl.
The glycosylation-profile of von Willebrand factor (VWF) is known to strongly influence its plasma levels. VWF contains several carbohydrate structures, including O-linked glycans that primarily consist of sialylated T-antigen (NeuAc(
2-3)Gal-(
1-3)-[NeuAc(2-6)]GalNAc). It is unknown yet if O-linked carbohydrates affect VWF levels. We developed an immunosorbent-assay based on neuraminidase-incubation allowing subsequent binding of Peanut-Agglutinin (PNA) to de-sialylated O-linked T-antigen on VWF. An inverse relation was found between PNA-binding and VWF-antigen levels in healthy individuals (n=111; Pearson-rank=-0.43; p<0.0001). A similar inverse association was observed in randomly-selected plasma-samples from our diagnostic laboratory: 252±125% for VWF<0.5 U/ml (n=15); 131±36% for VWF between 0.5 and 1.5 U/ml (n=32); 92±40% for VWF>1.5 U/ml (n=19). Reduced or increased PNA-binding was also observed in patients with increased (liver cirrhosis) or reduced (von Willebrand disease (VWD)-type 1) VWF-antigen levels, respectively. VWD-type 1 patients further displayed increased ratios of propeptide over mature VWF-antigen levels (0.38±0.18 versus 0.17±0.03 for patients and controls, respectively; p<0.0001), which is indicative for reduced VWF survival in these patients. Interestingly, a linear relation between PNA-binding and propeptide/VWF ratio was observed (Spearman-rank=0.47), suggesting a potential association between O-linked glycosylation and VWF survival. Finally, we detected a marked decrease in PNA-binding in post-DDAVP samples from various patients, indicating that the O-linked glycosylation profile of VWF stored in endothelial storage-organelles may differ from circulating VWF.
