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

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

Abstract

Binding of Igs to myeloid cells via FcR is a key event in the control of innate and acquired immunity. FcγRIIa (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.

Citation

Bournazos, S., Hart, S. P., Chamberlain, L. H., Glennie, M. J., & Dransfield, I. (2009). Association of FcγRIIa (CD32a) with lipid rafts regulates ligand binding activity. Journal of Immunology, 182(12), 8026-8036. https://doi.org/10.4049/jimmunol.0900107

• Journal Article Type: Article
• Online Publication Date: Jun 3, 2009
• Publication Date: Jun 15, 2009
• Deposit Date: Nov 13, 2014
• Journal: Journal Of Immunology
• Print ISSN: 0022-1767
• Publisher: American Association of Immunologists
• Peer Reviewed: Peer Reviewed
• Volume: 182
• Issue: 12
• Pages: 8026-8036
• DOI: https://doi.org/10.4049/jimmunol.0900107
• Keywords: Cholesterol, Inflammation, Membrane Microdomains, Research, Research Support, Role, Sphingolipids,
• Public URL: https://hull-repository.worktribe.com/output/464959
• Contract Date: Nov 13, 2014