Site-specific O-glycosylation of members of the low-density lipoprotein receptor superfamily enhances ligand interactions

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Shengjun Wang, Yang Mao, Yoshiki Narimatsu, Zilu Ye, Weihua Tian, Christoffer K Goth, Erandi Lira-Navarrete, Nis Borbye Pedersen, Asier Benito-Vicente, Cesar Martin, Kepa B Uribe, Ramon Hurtado-Guerrero, Christina Christoffersen, Nabil G Seidah, Rikke Nielsen, Erik I Christensen, Lars Hansen, Eric P Bennett, Sergey Y Vakhrushev, Katrine T Schjoldager & 1 andre Henrik Clausen

The low-density lipoprotein receptor (LDLR) and related proteins are important for the transport of diverse biomolecules across cell membranes and barriers. Their functions are especially relevant for cholesterol homeostasis and diseases, including neurodegenerative and kidney disorders. Members of the LDLR-related protein family share LDLR class A (LA) repeats providing binding properties for lipoproteins and other biomolecules. We previously demonstrated that short linker regions between these LA repeats contain conserved O-glycan-sites. Moreover, we found that O-glycan modifications at these sites are selectively controlled by the GalNAc-transferase isoform, GalNAc-T11. However, the effects of GalNAc-T11-mediated O-glycosylation on LDLR and related receptors localization and function are unknown. Here, we characterized O-glycosylation of LDLR-related proteins and identified conserved O-glycosylation sites in the LA linker regions of VLDLR, LRP1, and LRP2 (Megalin) from both cell lines and rat organs. Using a panel of gene-edited isogenic cell line models, we demonstrate that GalNAc-T11-mediated LDLR and VLDLR O-glycosylation is not required for transport and cell surface expression and stability of these receptors, but markedly enhances LDL and VLDL binding and uptake. Direct ELISA-based binding assays with truncated LDLR constructs revealed that O-glycosylation increased affinity for LDL by approximately 5-fold. The molecular basis for this observation is currently unknown, but these findings open up new avenues for exploring the roles of LDLR-related proteins in disease.

OriginalsprogEngelsk
TidsskriftThe Journal of Biological Chemistry
Vol/bind293
Udgave nummer19
Sider (fra-til)7408 –7422
ISSN0021-9258
DOI
StatusUdgivet - 2018

ID: 194041815