Stress protein (hsp73)-mediated, TAP-independent processing of endogenous, truncated SV40 large T antigen for Db-restricted peptide presentation.
Transporter associated with antigen processing (TAP)-competent and TAP-deficient cell lines were transfected with expression plasmids encoding either the wild-type (wt) large tumor antigen (T-Ag) of SV40, or a truncated cytoplasmic variant (cT-Ag) of this viral protein. Stable expression of comparable levels of both forms of the viral protein was observed in different transfectants. The truncated cT-Ag variant, but not the wtT-Ag was stably associated with the constitutively expressed, cytosolic heat shock protein (hsp)73 chaperone. Two Db-binding peptides and one Kb-binding peptide of T-Ag were presented to cytotoxic T lymphocyte lines (CTLL) by TAP-competent transfectants expressing either wtT-Ag or cT-Ag. TAP-deficient transfectants expressing the wtT-Ag did not present any of these epitopes to CTLL. In contrast, TAP-deficient transfectants expressing the truncated hsp73-associated cT-Ag, presented the two Db-binding epitopes, but not the Kb-binding T-Ag epitope to CTLL. Regurgitation of peptides by transfectants was not detectable. The described data indicate that a pool of post-Golgi Db molecules is available for 2-3 h in TAP-deficient transfectants for loading with peptides released during endolysosomal processing of hsp73-associated, endogenous antigen.
Schirmbeck
R
R
Institute for Medical Microbiology, University of Ulm, Germany.
Böhm
W
W
Reimann
J
J
D000818:Animals; D017951:Antigen Presentation; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D015870:Gene Expression; D006183:H-2 Antigens / Q000378:metabolism*; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D064532:Histocompatibility Antigen H-2D; D051379:Mice; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014162:Transfection
D000952:Antigens, Polyomavirus Transforming; D002352:Carrier Proteins; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D064532:Histocompatibility Antigen H-2D; C494372:Hspa8 protein, mouse