The final N-terminal trimming of a subaminoterminal proline-containing HLA class I-restricted antigenic peptide in the cytosol is mediated by two peptidases.
The proteasome produces MHC class I-restricted antigenic peptides carrying N-terminal extensions, which are trimmed by other peptidases in the cytosol or within the endoplasmic reticulum. In this study, we show that the N-terminal editing of an antigenic peptide with a predicted low TAP affinity can occur in the cytosol. Using proteomics, we identified two cytosolic peptidases, tripeptidyl peptidase II and puromycin-sensitive aminopeptidase, that trimmed the N-terminal extensions of the precursors produced by the proteasome, and led to a transient enrichment of the final antigenic peptide. These peptidases acted either sequentially or redundantly, depending on the extension remaining at the N terminus of the peptides released from the proteasome. Inhibition of these peptidases abolished the CTL-mediated recognition of Ag-expressing cells. Although we observed some proteolytic activity in fractions enriched in endoplasmic reticulum, it could not compensate for the loss of tripeptidyl peptidase II/puromycin-sensitive aminopeptidase activities.
Lévy
Frédéric
F
Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Ch. des Boveresses 155, CH-1066 Epalinges, Switzerland. Frederic.Levy@isrec.unil.ch
Burri
Lena
L
Morel
Sandra
S
Peitrequin
Anne-Lise
AL
Lévy
Nicole
N
Bachi
Angela
A
Hellman
Ulf
U
Van den Eynde
Benoît J
BJ
Servis
Catherine
C
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017951:Antigen Presentation / Q000187:drug effects; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015235:HLA-B Antigens / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D059949:HLA-B51 Antigen; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010446:Peptide Fragments / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000276:immunology; D011691:Puromycin / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism / Q000502:physiology*; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D000590:Amino Acid Chloromethyl Ketones; D004791:Enzyme Inhibitors; D015235:HLA-B Antigens; D059949:HLA-B51 Antigen; D009842:Oligopeptides; D010446:Peptide Fragments; D011498:Protein Precursors; C055604:alanyl-alanyl-phenylalanine chloromethyl ketone; C067713:lactacystin; D011691:Puromycin; D011392:Proline; D000626:Aminopeptidases; C025579:enkephalin degrading enzyme; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D000111:Acetylcysteine