title: Re-evaluating the generation of a "proteasome-independent" MHC class I-restricted CD8 T cell epitope.
abstract: The proteasome is primarily responsible for the generation of MHC class I-restricted CTL epitopes. However, some epitopes, such as NP(147-155) of the influenza nucleoprotein (NP), are presented efficiently in the presence of proteasome inhibitors. The pathways used to generate such apparently "proteasome-independent" epitopes remain poorly defined. We have examined the generation of NP(147-155) and a second proteasome-dependent NP epitope, NP(50-57), using cells adapted to growth in the presence of proteasome inhibitors and also through protease overexpression. We observed that: 1) Ag processing and presentation proceeds in proteasome-inhibitor adapted cells but may become more dependent, at least in part, on nonproteasomal protease(s), 2) tripeptidyl peptidase II does not substitute for the proteasome in the generation of NP(147-155), 3) overexpression of leucine aminopeptidase, thymet oligopeptidase, puromycin-sensitive aminopeptidase, and bleomycin hydrolase, has little impact on the processing and presentation of NP(50-57) or NP(147-155), and 4) proteasome-inhibitor treatment altered the specificity of substrate cleavage by the proteasome using cell-free digests favoring NP(147-155) epitope preservation. Based on these results, we propose a central role for the proteasome in epitope generation even in the presence of proteasome inhibitors, although such inhibitors will likely alter cleavage patterns and may increase the dependence of the processing pathway on postproteasomal enzymes.
authors.affiliation: Department of Microbiology and Immunology, Jefferson Medical College and Kimmel Cancer Institute, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA.
authors.forename: E John
authors.initials: EJ
authors.lastname: Wherry
authors.forename: Tatiana N
authors.initials: TN
authors.lastname: Golovina
authors.forename: Susan E
authors.initials: SE
authors.lastname: Morrison
authors.forename: Gomathinayagam
authors.initials: G
authors.lastname: Sinnathamby
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McElhaugh
authors.forename: David C
authors.initials: DC
authors.lastname: Shockey
authors.forename: Laurence C
authors.initials: LC
authors.lastname: Eisenlohr
mesh_terms: D000626:Aminopeptidases; D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002474:Cell-Free System; D002478:Cells, Cultured; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D015971:Gene Expression Regulation, Enzymologic; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D007211:Indoles / Q000494:pharmacology; D051379:Mice; D009698:Nucleoproteins / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D034622:RNA Interference; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism
chemical_list: D018984:Epitopes, T-Lymphocyte; D015395:Histocompatibility Antigens Class I; D007211:Indoles; D009698:Nucleoproteins; D010446:Peptide Fragments; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; C098807:butabindide; C122116:nucleoprotein (147-155); D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D046988:Proteasome Endopeptidase Complex