Biosynthesis and post-translational processing of lectin-like oxidized low density lipoprotein receptor-1 (LOX-1). N-linked glycosylation affects cell-surface expression and ligand binding

J Biol Chem. 2000 Mar 3;275(9):6573-9. doi: 10.1074/jbc.275.9.6573.

Abstract

LOX-1 (lectin-like oxidized low density lipoprotein receptor-1) is a type II membrane protein belonging to the C-type lectin family that can act as a cell-surface receptor for atherogenic oxidized low density lipoprotein (Ox-LDL) and may play crucial roles in atherogenesis. In this study, we show, by pulse-chase labeling and glycosidase digestion, that LOX-1 is synthesized as a 40-kDa precursor protein with N-linked high mannose carbohydrate chains (pre-LOX-1), which is subsequently further glycosylated and processed into the 48-kDa mature form within 40 min. Furthermore, when treated with an N-glycosylation inhibitor, tunicamycin, both tumor necrosis factor-alpha-activated bovine aortic endothelial cells and CHO-K1 cells stably expressing bovine LOX-1 (BLOX-1-CHO) exclusively produced a 32-kDa deglycosylated form of LOX-1. Cell enzyme-linked immunosorbent assay, flow cytometry, and immunofluorescence confocal microscopy demonstrated that the deglycosylated form of LOX-1 is not efficiently transported to the cell surface, but is retained in the endoplasmic reticulum or Golgi apparatus in tumor necrosis factor-alpha-activated bovine aortic endothelial cells, but not in BLOX-1-CHO cells. Radiolabeled Ox-LDL binding studies revealed that the deglycosylated form of LOX-1 expressed on the cell surface of BLOX-1-CHO cells has a reduced affinity for Ox-LDL binding. Taken together, N-linked glycosylation appears to play key roles in the cell-surface expression and ligand binding of LOX-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amidohydrolases / metabolism
  • Animals
  • CHO Cells
  • Cattle
  • Cells, Cultured
  • Cricetinae
  • Endothelium, Vascular
  • Flow Cytometry
  • Fluorescent Antibody Technique
  • Glycosylation
  • Iodine Radioisotopes
  • Lipoproteins, LDL / metabolism
  • Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase
  • Protein Binding
  • Protein Precursors / metabolism*
  • Protein Processing, Post-Translational*
  • Receptors, LDL / biosynthesis
  • Receptors, LDL / metabolism*
  • Receptors, Oxidized LDL
  • Scavenger Receptors, Class E
  • Tumor Necrosis Factor-alpha / pharmacology
  • Tunicamycin / pharmacology

Substances

  • Iodine Radioisotopes
  • Lipoproteins, LDL
  • Protein Precursors
  • Receptors, LDL
  • Receptors, Oxidized LDL
  • Scavenger Receptors, Class E
  • Tumor Necrosis Factor-alpha
  • oxidized low density lipoprotein
  • Tunicamycin
  • Amidohydrolases
  • Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase