N-Glycosylation instead of cholesterol mediates oligomerization and apical sorting of GPI-APs in FRT cells

Mol Biol Cell. 2011 Dec;22(23):4621-34. doi: 10.1091/mbc.E11-04-0320. Epub 2011 Oct 12.

Abstract

Sorting of glycosylphosphatidyl-inositol--anchored proteins (GPI-APs) in polarized epithelial cells is not fully understood. Oligomerization in the Golgi complex has emerged as the crucial event driving apical segregation of GPI-APs in two different kind of epithelial cells, Madin-Darby canine kidney (MDCK) and Fisher rat thyroid (FRT) cells, but whether the mechanism is conserved is unknown. In MDCK cells cholesterol promotes GPI-AP oligomerization, as well as apical sorting of GPI-APs. Here we show that FRT cells lack this cholesterol-driven oligomerization as apical sorting mechanism. In these cells both apical and basolateral GPI-APs display restricted diffusion in the Golgi likely due to a cholesterol-enriched membrane environment. It is striking that N-glycosylation is the critical event for oligomerization and apical sorting of GPI-APs in FRT cells but not in MDCK cells. Our data indicate that at least two mechanisms exist to determine oligomerization in the Golgi leading to apical sorting of GPI-APs. One depends on cholesterol, and the other depends on N-glycosylation and is insensitive to cholesterol addition or depletion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Polarity
  • Cells, Cultured
  • Cholesterol / metabolism*
  • Cholesterol / pharmacology
  • Dogs
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Fluorescence Recovery After Photobleaching
  • GPI-Linked Proteins / genetics
  • GPI-Linked Proteins / metabolism*
  • Glycosylation
  • Golgi Apparatus / metabolism
  • Golgi Apparatus / ultrastructure
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Kidney / cytology
  • Protein Transport
  • Rats
  • Rats, Inbred F344
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Thyroid Gland / cytology
  • Thyroid Gland / metabolism

Substances

  • GPI-Linked Proteins
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Cholesterol