A spliced antigenic peptide comprising a single spliced amino acid is produced in the proteasome by reverse splicing of a longer peptide fragment followed by trimming.
Peptide splicing is a novel mechanism of production of peptides relying on the proteasome and involving the linkage of fragments originally distant in the parental protein. Peptides produced by splicing can be presented on class I molecules of the MHC and recognized by CTLs. In this study, we describe a new antigenic peptide, which is presented by HLA-A3 and comprises two noncontiguous fragments of the melanoma differentiation Ag gp100(PMEL17) spliced together in the reverse order to that in which they appear in the parental protein. Contrary to the previously described spliced peptides, which are produced by the association of fragments of 3-6 aa, the peptide described in this work results from the ultimate association of an 8-aa fragment with a single arginine residue. As described before, peptide splicing takes place in the proteasome by transpeptidation involving an acyl-enzyme intermediate linking one of the peptide fragment to a catalytic subunit of the proteasome. Interestingly, we observe that the peptide causing the nucleophilic attack on the acyl-enzyme intermediate must be at least 3 aa long to give rise to a spliced peptide. The spliced peptide produced from this reaction therefore bears an extended C terminus that needs to be further trimmed to produce the final antigenic peptide. We show that the proteasome is able to perform the final trimming step required to produce the antigenic peptide described in this work.
Ludwig Institute for Cancer Research, B-1200 Brussels, Belgium;
Alexandre
A
Michaux
Pierre
P
Larrieu
Vincent
V
Stroobant
Jean-François
JF
Fonteneau
Francine
F
Jotereau
Benoît J
BJ
Van den Eynde
Agnès
A
Moreau-Aubry
Nathalie
N
Vigneron
D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D015791:HLA-A3 Antigen / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D019154:Protein Splicing / Q000502:physiology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D058951:gp100 Melanoma Antigen / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
C442141:HLA-A*03:01 antigen; D015791:HLA-A3 Antigen; D010446:Peptide Fragments; D058951:gp100 Melanoma Antigen; D046988:Proteasome Endopeptidase Complex