title: Tripeptidyl peptidase II is dispensable for the generation of both proteasome-dependent and proteasome-independent ligands of HLA-B27 and other class I molecules.
abstract: A significant fraction of the HLA-B27-bound peptide repertoire is resistant to proteasome inhibitors. The possible implication of tripeptidyl peptidase II (TPPII) in generating this subset was analyzed by quantifying the surface re-expression of HLA-B*2705 after acid stripping in the presence of two TPPII inhibitors, butabindide and Ala-Ala-Phe-chloromethylketone. Neither decreased HLA-B27 re-expression under conditions in which TPPII activity was largely inhibited. This was in contrast to a significant effect of the proteasome inhibitor epoxomicin. The failure of TPPII inhibition to decrease surface re-expression was not limited to HLA-B27, since it was also observed in several HLA-B27-negative cell lines, including Mel JuSo. Actually, HLA class I re-expression in Mel JuSo cells increased as a function of butabindide concentration, which is consistent with an involvement of TPPII in destroying HLA class I ligands. Inhibition of TPPII with small interfering RNA also failed to decrease the surface expression of HLA class I molecules on 143B cells. Our results indicate that TPPII is dispensable for the generation of proteasome-dependent HLA class I ligands and, without excluding its role in producing some individual epitopes, this enzyme is not involved to any quantitatively significant extent, in generating the proteasome-independent HLA-B27-bound peptide repertoire.
authors.affiliation: Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid), Universidad Autónoma, Madrid, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Marcilla
authors.forename: Eugenia M
authors.initials: EM
authors.lastname: Villasevil
authors.forename: José Antonio López
authors.initials: JA
authors.lastname: de Castro
mesh_terms: D000143:Acids / Q000494:pharmacology; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000626:Aminopeptidases; D017951:Antigen Presentation / Q000187:drug effects / Q000276:immunology*; D020126:Brefeldin A / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D003374:Coumarins / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D004355:Drug Stability; D015796:HLA-B27 Antigen / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000143:Acids; D000590:Amino Acid Chloromethyl Ketones; D003374:Coumarins; D015796:HLA-B27 Antigen; D015395:Histocompatibility Antigens Class I; D007211:Indoles; D009842:Oligopeptides; D034741:RNA, Small Interfering; D015842:Serine Proteinase Inhibitors; C117513:alanyl-alanyl-phenylalanyl-7-amino-4-methylcoumarin; C098807:butabindide; C055604:alanyl-alanyl-phenylalanine chloromethyl ketone; D020126:Brefeldin A; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C078846:epoxomicin