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Blood, 15 October 2005, Vol. 106, No. 8, pp. 2744-2749. Prepublished online as a Blood First Edition Paper on July 12, 2005; DOI 10.1182/blood-2005-04-1454.
HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY The influence of N-linked glycosylation on the function of platelet glycoprotein VIFrom the Division of Experimental Hemostasis and Thrombosis, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA; and Department of Protein Biochemistry, Institute of Life Science, Kurume University, Kurume, Fukuoka, Japan.
Using recombinant human glycoprotein VI (GPVI), we evaluated the effect of N-linked glycosylation at the consensus site Asparagine92-Glycine-Serine94 (N92GS94) on binding of this platelet-specific receptor to its ligands, human type I collagen, collagen-related peptide (CRP), and the snake venom C-type lectin convulxin (CVX). In COS-7 cells transiently transfected with GPVI, deglycosylation with peptide-N-glycosidase F (PNGase F; specific for complex N-linked glycans) or tunicamycin decreases the molecular weight of GPVI and reduces transfected COS-7 cell binding to both CRP and CVX. In stably transfected Dami cells, the substitutions N92A or S94A, but not L95H, resulted in a 30% to 40% decrease in adhesion to CVX, but a 90% or greater decrease in adhesion to CRP and a 65% to 70% decrease in adhesion to type I collagen. Treatment with PNGase F, but not Endoglycosidase H (Endo H) (specific for high-mannose N-linked glycans), produced an equivalent decrease in molecular weight. Neither N92A nor S94A affected the expression of GPVI, based on the direct binding of murine antihuman GPVI monoclonal antibody 204-11 to transfected Dami cells. These findings indicate that N-linked glycosylation at N92 in human GPVI is not required for surface expression, but contributes to maximal adhesion to type I collagen, CRP and, to a lesser extent, CVX.
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