title: Quantifying recruitment of cytosolic peptides for HLA class I presentation: impact of TAP transport.
abstract: MHC class I ligands are recruited from the cytosolic peptide pool, whose size is likely to depend on the balance between peptide generation by the proteasome and peptide degradation by downstream peptidases. We asked what fraction of this pool is available for presentation, and how the size of this fraction is modulated by peptide affinity for the TAP transporters. A model epitope restricted by HLA-A2 and a series of epitope precursors with N-terminal extensions by single residues modifying TAP affinity were expressed in a system that allowed us to monitor and modulate cytosolic peptide copy numbers. We show that presentation varies strongly according to TAP affinities of the epitope precursors. The fraction of cytosolic peptides recruited for MHC presentation does not exceed 1% and is more than two logs lower for peptides with very low TAP affinities. Therefore, TAP affinity has a substantial impact on MHC class I Ag presentation.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale Unité 580, Institut Necker, Paris, France.
authors.forename: Doriana
authors.initials: D
authors.lastname: Fruci
authors.forename: Grégoire
authors.initials: G
authors.lastname: Lauvau
authors.forename: Loredana
authors.initials: L
authors.lastname: Saveanu
authors.forename: Massimo
authors.initials: M
authors.lastname: Amicosante
authors.forename: Richard H
authors.initials: RH
authors.lastname: Butler
authors.forename: Axel
authors.initials: A
authors.lastname: Polack
authors.forename: Florent
authors.initials: F
authors.lastname: Ginhoux
authors.forename: François
authors.initials: F
authors.lastname: Lemonnier
authors.forename: Hüseyin
authors.initials: H
authors.lastname: Firat
authors.forename: Peter M
authors.initials: PM
authors.lastname: van Endert
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000276:immunology* / Q000378:metabolism*; D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D001667:Binding, Competitive / Q000235:genetics / Q000276:immunology; D002461:Cell Line, Transformed; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D003601:Cytotoxicity Tests, Immunologic / Q000379:methods; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006183:H-2 Antigens / Q000276:immunology / Q000378:metabolism*; D015789:HLA-A2 Antigen / Q000276:immunology / Q000378:metabolism*; D064532:Histocompatibility Antigen H-2D; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010455:Peptides / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D021381:Protein Transport / Q000235:genetics / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D014162:Transfection / Q000379:methods; D014407:Tumor Cells, Cultured
chemical_list: D018528:ATP-Binding Cassette Transporters; D018984:Epitopes, T-Lymphocyte; D006183:H-2 Antigens; D015789:HLA-A2 Antigen; D064532:Histocompatibility Antigen H-2D; D008164:Luminescent Proteins; D010455:Peptides; D049452:Green Fluorescent Proteins