Title : Glycosylation of
Asn-76 in mouse
GPIHBP1 is critical for its appearance on the cell surface and the binding of chylomicrons and
lipoprotein lipase
Abstract :
- GPIHBP1 is a glycosylphosphatidylinositol-anchored protein in the lymphocyte antigen 6 ( Ly-6 ) family that recently was identified as a platform for the lipolytic processing of triglyceride-rich lipoproteins
- GPIHBP1 binds both LPL and chylomicrons and is expressed on the luminal face of microvascular endothelial cells
- Here, we show that mouse GPIHBP1 is N-glycosylated at Asn-76 within the Ly-6 domain
- Human GPIHBP1 is also glycosylated
- The N-linked glycan could be released from mouse GPIHBP1 with N-glycosidase F , endoglycosidase H , or endoglycosidase F1
- The glycan was marginally sensitive to endoglycosidase F2 digestion but resistant to endoglycosidase F3 digestion, suggesting that the glycan on GPIHBP1 is of the oligomannose type
- Mutating the N-glycosylation site in mouse GPIHBP1 results in an accumulation of GPIHBP1 in the endoplasmic reticulum and a markedly reduced amount of the protein on the cell surface
- Consistent with this finding, cells expressing a nonglycosylated GPIHBP1 lack the ability to bind LPL or chylomicrons
- Eliminating the N-glycosylation site in a truncated soluble version of GPIHBP1 causes a modest reduction in the secretion of the protein
- These studies demonstrate that N-glycosylation of GPIHBP1 is important for the trafficking of GPIHBP1 to the cell surface