Quantifying recruitment of cytosolic peptides for HLA class I presentation: impact of TAP transport.
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.
Fruci
Doriana
D
Institut National de la Santé et de la Recherche Médicale Unité 580, Institut Necker, Paris, France.
Lauvau
Grégoire
G
Saveanu
Loredana
L
Amicosante
Massimo
M
Butler
Richard H
RH
Polack
Axel
A
Ginhoux
Florent
F
Lemonnier
François
F
Firat
Hüseyin
H
van Endert
Peter M
PM
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
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