N-Glycans on the link domain of human HARE/Stabilin-2 are needed for hyaluronan binding to purified ecto-domain, but not for cellular endocytosis of hyaluronan

Glycobiology. 2010 Aug;20(8):991-1001. doi: 10.1093/glycob/cwq057. Epub 2010 Apr 14.

Abstract

The hyaluronic acid receptor for endocytosis (HARE)/Stabilin-2 is the primary systemic scavenger receptor for 13 ligands including hyaluronan (HA), heparin and chondroitin sulfates. Most ligand-binding sites are within the 190 kDa isoform, which contains approximately 25 kDa of N-glycans and is the C-terminal half of the full-length 315 kDa HARE. Glycoproteomic analyses of purified recombinant human 190-HARE ecto-domain identified a diverse population of glycans at 10 of 17 consensus sites. The most diversity (and the only sialylated structures) occurred at N(2280), within the HA-binding Link domain. To determine if these N-glycans are required for HA binding, we created human Flp-In 293 cell lines expressing membrane-bound or soluble ecto-domain variants of 190-HARE(N2280A). Membrane-bound HARE lacking Link domain N-glycans mediated rapid HA endocytosis, but purified 190-HARE(N2280A) ecto-domain showed little or no HA binding in ELISA-like, HA-HARE pull-down assays or by surface plasmon resonance analysis (which detected very high apparent affinity for 190-HARE ecto-domain binding to HA; K(d) = 5.2 nM). The results indicate that Link domain N-glycans stabilize interactions that facilitate HA binding to HARE.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Cell Adhesion Molecules, Neuronal / chemistry
  • Cell Adhesion Molecules, Neuronal / metabolism*
  • Cell Line
  • Endocytosis*
  • Humans
  • Hyaluronic Acid / chemistry
  • Hyaluronic Acid / metabolism*
  • Polysaccharides / chemistry
  • Polysaccharides / metabolism*
  • Protein Structure, Tertiary

Substances

  • Cell Adhesion Molecules, Neuronal
  • Polysaccharides
  • STAB2 protein, human
  • Hyaluronic Acid