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XB-ART-48956
J Biol Chem 2014 Jun 20;28925:17312-24. doi: 10.1074/jbc.M113.545053.
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Low density lipoprotein receptor class A repeats are O-glycosylated in linker regions.

Pedersen NB, Wang S, Narimatsu Y, Yang Z, Halim A, Schjoldager KT, Madsen TD, Seidah NG, Bennett EP, Levery SB, Clausen H.


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The low density lipoprotein receptor (LDLR) is crucial for cholesterol homeostasis and deficiency in LDLR functions cause hypercholesterolemia. LDLR is a type I transmembrane protein that requires O-glycosylation for stable expression at the cell surface. It has previously been suggested that LDLR O-glycosylation is found N-terminal to the juxtamembrane region. Recently we identified O-glycosylation sites in the linker regions between the characteristic LDLR class A repeats in several LDLR-related receptors using the "SimpleCell" O-glycoproteome shotgun strategy. Herein, we have systematically characterized O-glycosylation sites on recombinant LDLR shed from HEK293 SimpleCells and CHO wild-type cells. We find that the short linker regions between LDLR class A repeats contain an evolutionarily conserved O-glycosylation site at position -1 of the first cysteine residue of most repeats, which in wild-type CHO cells is glycosylated with the typical sialylated core 1 structure. The glycosites in linker regions of LDLR class A repeats are conserved in LDLR from man to Xenopus and found in other homologous receptors. O-Glycosylation is controlled by a large family of polypeptide GalNAc transferases. Probing into which isoform(s) contributed to glycosylation of the linker regions of the LDLR class A repeats by in vitro enzyme assays suggested a major role of GalNAc-T11. This was supported by expression of LDLR in HEK293 cells, where knock-out of the GalNAc-T11 isoform resulted in the loss of glycosylation of three of four linker regions.

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Species referenced: Xenopus laevis
Genes referenced: galnt11 ldlr

References [+] :
Andersen, Specific binding of alpha-macroglobulin to complement-type repeat CR4 of the low-density lipoprotein receptor-related protein. 2000, Pubmed