Association of FcgammaRIIa (CD32a) with lipid rafts regulates ligand binding activity

Stylianos Bournazos, Simon P Hart, Luke H Chamberlain, Martin J Glennie, Ian Dransfield

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Binding of Igs to myeloid cells via FcR is a key event in the control of innate and acquired immunity. FcgammaRIIa (CD32a) is a receptor for multivalent IgG expressed predominantly by myeloid cells, and its association with microdomains rich in cholesterol and sphingolipids, termed as lipid rafts, has been reported to be essential for efficient signaling. However, for many myeloid cell types, ligand binding to CD32a is suppressed by as yet undefined mechanisms. In this study, we have examined the role of CD32a-lipid raft interactions in the regulation of IgG binding to CD32a. Disruption of lipid raft structure following depletion or sequestration of membrane cholesterol greatly inhibited CD32a-mediated IgG binding. Furthermore, specific CD32a mutants, which show reduced association with lipid rafts (A224S and C241A), displayed decreased levels of IgG binding compared with wild-type CD32a. In contrast, constitutively lipid raft-associated CD32a (GPI-anchored CD32a) exhibited increased capacity for IgG binding compared with the full-length transmembrane CD32a. Our findings clearly suggest a major role for lipid rafts in the regulation of IgG binding and, more specifically, that suppression of CD32a-mediated IgG binding in myeloid cells is achieved by receptor exclusion from lipid raft membrane microdomains.
Original languageEnglish
Pages (from-to)8026-8036
Number of pages11
JournalJournal of Immunology
Volume182
Issue number12
DOIs
Publication statusPublished - 15 Jun 2009

Keywords

  • amino acid sequence
  • animals
  • cultured cells
  • cricetinae
  • humans
  • immunoglobulin G
  • ligands
  • membrane microdomains
  • molecular sequence data
  • neutrophils
  • pancreatic elastase
  • protein binding
  • receptors, IgG

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