Cytotoxic T lymphocyte epitopes of HIV-1 Nef: Generation of multiple definitive major histocompatibility complex class I ligands by proteasomes.
Although a pivotal role of proteasomes in the proteolytic generation of epitopes for major histocompatibility complex (MHC) class I presentation is undisputed, their precise function is currently the subject of an active debate: do proteasomes generate many epitopes in definitive form, or do they merely generate the COOH termini, whereas the definitive NH(2) termini are cleaved by aminopeptidases? We determined five naturally processed MHC class I ligands derived from HIV-1 Nef. Unexpectedly, the five ligands correspond to only three cytotoxic T lymphocyte (CTL) epitopes, two of which occur in two COOH-terminal length variants. Parallel analyses of proteasomal digests of a Nef fragment encompassing the epitopes revealed that all five ligands are direct products of proteasomes. Moreover, in four of the five ligands, the NH(2) termini correspond to major proteasome cleavage sites, and putative NH(2)-terminally extended precursor fragments were detected for only one of the five ligands. All ligands are transported by the transporter associated with antigen processing (TAP). The combined results from these five ligands provide strong evidence that many definitive MHC class I ligands are precisely cleaved at both ends by proteasomes. Additional evidence supporting this conclusion is discussed, along with contrasting results of others who propose a strong role for NH(2)-terminal trimming with direct proteasomal epitope generation being a rare event.
Lucchiari-Hartz
M
M
Max-Planck Institute of Immunobiology, D-79108 Freiburg, Germany.
van Endert
P M
PM
Lauvau
G
G
Maier
R
R
Meyerhans
A
A
Mann
D
D
Eichmann
K
K
Niedermann
G
G
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000276:immunology; D000111:Acetylcysteine / Q000031:analogs & derivatives; D017951:Antigen Presentation / Q000276:immunology; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D015693:Gene Products, nef / Q000276:immunology* / Q000378:metabolism; D015497:HIV-1 / Q000276:immunology*; D015789:HLA-A2 Antigen / Q000276:immunology; D015793:HLA-B7 Antigen / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D008024:Ligands; D009097:Multienzyme Complexes / Q000378:metabolism*; D010446:Peptide Fragments / Q000276:immunology; D010455:Peptides / Q000276:immunology; D046988:Proteasome Endopeptidase Complex; D012107:Research Design; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D054311:nef Gene Products, Human Immunodeficiency Virus
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D015853:Cysteine Proteinase Inhibitors; D018984:Epitopes, T-Lymphocyte; D015693:Gene Products, nef; D015789:HLA-A2 Antigen; D015793:HLA-B7 Antigen; D015395:Histocompatibility Antigens Class I; D008024:Ligands; D009097:Multienzyme Complexes; D010446:Peptide Fragments; D010455:Peptides; C073119:TAP1 protein, human; D054311:nef Gene Products, Human Immunodeficiency Virus; C067713:lactacystin; C071692:TAP2 protein, human; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine