Galectin-4-regulated delivery of glycoproteins to the brush border membrane of enterocyte-like cells

Traffic. 2009 Apr;10(4):438-50. doi: 10.1111/j.1600-0854.2009.00882.x. Epub 2009 Jan 24.

Abstract

We have previously reported that silencing of galectin-4 expression in polarized HT-29 cells perturbed apical biosynthetic trafficking and resulted in a phenotype similar to the inhibitor of glycosylation, 1-benzyl-2-acetamido-2-deoxy-beta-d-galactopyranoside (GalNAcalpha-O-bn). We now present evidence of a lipid raft-based galectin-4-dependent mechanism of apical delivery of glycoproteins in these cells. First, galectin-4 recruits the apical glycoproteins in detergent-resistant membranes (DRMs) because these glycoproteins were depleted in DRMs isolated from galectin-4-knockdown (KD) HT-29 5M12 cells. DRM-associated glycoproteins were identified as ligands for galectin-4. Structural analysis showed that DRMs were markedly enriched in a series of complex N-glycans in comparison to detergent-soluble membranes. Second, in galectin-4-KD cells, the apical glycoproteins still exit the Golgi but accumulated inside the cells, showing that their recruitment within lipid rafts and their apical trafficking required the delivery of galectin-4 at a post-Golgi level. This lectin that is synthesized on free cytoplasmic ribosomes is externalized from HT-29 cells mostly in the apical medium and follows an apical endocytic-recycling pathway that is required for the apical biosynthetic pathway. Together, our data show that the pattern of N-glycosylation of glycoproteins serves as a recognition signal for endocytosed galectin-4, which drives the raft-dependent apical pathway of glycoproteins in enterocyte-like HT-29 cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers / metabolism
  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • Cell Membrane / metabolism*
  • Cell Polarity
  • Dipeptidyl Peptidase 4 / genetics
  • Dipeptidyl Peptidase 4 / metabolism
  • Enterocytes / cytology*
  • Enterocytes / metabolism
  • Galectin 4 / metabolism*
  • Glycoproteins / chemistry
  • Glycoproteins / metabolism*
  • Golgi Apparatus / metabolism
  • HT29 Cells
  • Humans
  • Membrane Microdomains / chemistry
  • Membrane Microdomains / metabolism
  • Molecular Sequence Data
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism

Substances

  • Biomarkers
  • Galectin 4
  • Glycoproteins
  • Recombinant Fusion Proteins
  • DPP4 protein, human
  • Dipeptidyl Peptidase 4