Oligomerization of the Macrophage Mannose Receptor Enhances gp120-mediated Binding of HIV-1

• Published in: The Journal of biological chemistry Vol. 284; no. 17; pp. 11027 - 11038
• Main Authors: Lai, Joey, Bernhard, Oliver K., Turville, Stuart G., Harman, Andrew N., Wilkinson, John, Cunningham, Anthony L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 24.04.2009; American Society for Biochemistry and Molecular Biology
• Subjects: Acetylgalactosamine - metabolism; Animals; Calcium; Calcium - metabolism; Carbohydrates; Cell adhesion molecules; Cross-Linking Reagents - chemistry; Cysteine - metabolism; Dendritic cells; Dimerization; Envelope protein; Flow Cytometry; fucose; Glycoprotein gp120; HIV Envelope Protein gp120 - metabolism; HIV-1 - metabolism; Human immunodeficiency virus 1; Humans; Langerhans cells; Langerhans Cells - metabolism; Langerhans Cells - virology; Lectins; Lectins, C-Type - chemistry; Lectins, C-Type - metabolism; Macrophages; Macrophages - metabolism; Macrophages - virology; mannan; Mannose; Mannose Receptor; Mannose receptors; Mannose-Binding Lectins - chemistry; Mannose-Binding Lectins - metabolism; Mass spectroscopy; Monocytes; N-Acetylgalactosamine; N-Acetylglucosamine; Oligomerization; oligosaccharides; Oligosaccharides - metabolism; Pathogens; Protein Structure and Folding; Rats; Receptors, Cell Surface - chemistry; Receptors, Cell Surface - metabolism; Virions
• DOI: 10.1074/jbc.M809698200
• ISSN: 0021-9258

C-type lectin receptors expressed on the surface of dendritic cells and macrophages are able to bind glycoproteins of microbial pathogens via mannose, fucose, and N-acetylglucosamine. Langerin on Langerhans cells, dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin on dendritic cells, and mannose receptor (MR) on dendritic cells and macrophages bind the human immunodeficiency virus (HIV) envelope protein gp120 principally via high mannose oligosaccharides. These C-type lectin receptors can also oligomerize to facilitate enhanced ligand binding. This study examined the effect of oligomerization of MR on its ability to bind to mannan, monomeric gp120, native trimeric gp140, and HIV type 1 BaL. Mass spectrometry analysis of cross-linked MR showed homodimerization on the surface of primary monocyte-derived dendritic cells and macrophages. Both monomeric and dimeric MR were precipitated by mannan, but only the dimeric form was co-immunoprecipitated by gp120. These results were confirmed independently by flow cytometry analysis of soluble monomeric and trimeric HIV envelope and a cellular HIV virion capture assay. As expected, mannan bound to the carbohydrate recognition domains of MR dimers mostly in a calcium-dependent fashion. Unexpectedly, gp120-mediated binding of HIV to dimers on MR-transfected Rat-6 cells and macrophages was not calcium-dependent, was only partially blocked by mannan, and was also partially inhibited by N-acetylgalactosamine 4-sulfate. Thus gp120-mediated HIV binding occurs via the calcium-dependent, non-calcium-dependent carbohydrate recognition domains and the cysteine-rich domain at the C terminus of MR dimers, presenting a much broader target for potential inhibitors of gp120-MR binding.