Cargando…

Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing

Cytotoxic T lymphocytes (CTL) recognize antigenic peptides bound to major histocompatibility complex class I antigens on the cell surface of virus-infected cells. It is believed that the majority of peptides originate from cytoplasmic degradation of proteins assumed to be mediated by the "20S&q...

Descripción completa

Detalles Bibliográficos
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1994
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2191686/
https://www.ncbi.nlm.nih.gov/pubmed/7931074
_version_ 1782147063083958272
collection PubMed
description Cytotoxic T lymphocytes (CTL) recognize antigenic peptides bound to major histocompatibility complex class I antigens on the cell surface of virus-infected cells. It is believed that the majority of peptides originate from cytoplasmic degradation of proteins assumed to be mediated by the "20S" proteasome. Cytosolic peptides are then translocated, presumably by transporters associated with antigen processing (TAP-1 and -2), into the lumen of the endoplasmic reticulum (ER) where binding and formation of the ternary complex between heavy chain, beta2-microglobulin (beta 2m) and peptide occurs. In this study, we have analyzed and compared the phenotype of two mutant cell lines, the thymoma cell line RMA-S and a small lung carcinoma cell line CMT.64, in order to address the mechanism that underlies the antigen processing deficiency of CMT.64 cells. Unlike RMA-S cells, vesicular stomatitis virus (VSV)-infected CMT.64 cells are not recognized by specific CTL. Interferon gamma (IFN-gamma) treatment of CMT.64 cells restores the ability of these cells to process and present VSV in the context of Kb. We show that although CMT.64 cells express a low level of beta 2m, the recognition of VSV-specific CTL is not restored by increasing the amount of beta 2m synthesized in CMT.64 cells. In addition, we find that CMT.64 cells express moderate levels of Kb heavy chain molecules, but most of it is unstable and rapidly degraded in the absence of IFN-gamma treatment. We infer that the antigen processing deficiency does not lie at the level of beta 2m or Kb production. We find also that the mRNAs for both TAP-1 and -2 are present in RMA and RMA-S cells but are absent in uninduced CMT.64 cells. Upon IFN-gamma induction, both mRNAs are highly expressed in CMT-64 cells. In addition, we find that the low molecular mass polypeptides 2 and 7, and additional components of the proteasome are induced by IFN-gamma in CMT- 64 cells. Finally, introduction of the rat TAP-1 gene in CMT.64 cells restores CTL recognition of VSV-infected cells. These results indicate that a TAP-1 homodimer may translocate peptides in the ER and explain partially the CMT.64 defect and the RMA-S phenotype. These findings link a dysfunction in the transport and/or generation of antigenic peptides to the capacity of tumor cells to evade immunosurveillance and provide a unique model system to dissect this phenomenon.
format Text
id pubmed-2191686
institution National Center for Biotechnology Information
language English
publishDate 1994
publisher The Rockefeller University Press
record_format MEDLINE/PubMed
spelling pubmed-21916862008-04-16 Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing J Exp Med Articles Cytotoxic T lymphocytes (CTL) recognize antigenic peptides bound to major histocompatibility complex class I antigens on the cell surface of virus-infected cells. It is believed that the majority of peptides originate from cytoplasmic degradation of proteins assumed to be mediated by the "20S" proteasome. Cytosolic peptides are then translocated, presumably by transporters associated with antigen processing (TAP-1 and -2), into the lumen of the endoplasmic reticulum (ER) where binding and formation of the ternary complex between heavy chain, beta2-microglobulin (beta 2m) and peptide occurs. In this study, we have analyzed and compared the phenotype of two mutant cell lines, the thymoma cell line RMA-S and a small lung carcinoma cell line CMT.64, in order to address the mechanism that underlies the antigen processing deficiency of CMT.64 cells. Unlike RMA-S cells, vesicular stomatitis virus (VSV)-infected CMT.64 cells are not recognized by specific CTL. Interferon gamma (IFN-gamma) treatment of CMT.64 cells restores the ability of these cells to process and present VSV in the context of Kb. We show that although CMT.64 cells express a low level of beta 2m, the recognition of VSV-specific CTL is not restored by increasing the amount of beta 2m synthesized in CMT.64 cells. In addition, we find that CMT.64 cells express moderate levels of Kb heavy chain molecules, but most of it is unstable and rapidly degraded in the absence of IFN-gamma treatment. We infer that the antigen processing deficiency does not lie at the level of beta 2m or Kb production. We find also that the mRNAs for both TAP-1 and -2 are present in RMA and RMA-S cells but are absent in uninduced CMT.64 cells. Upon IFN-gamma induction, both mRNAs are highly expressed in CMT-64 cells. In addition, we find that the low molecular mass polypeptides 2 and 7, and additional components of the proteasome are induced by IFN-gamma in CMT- 64 cells. Finally, introduction of the rat TAP-1 gene in CMT.64 cells restores CTL recognition of VSV-infected cells. These results indicate that a TAP-1 homodimer may translocate peptides in the ER and explain partially the CMT.64 defect and the RMA-S phenotype. These findings link a dysfunction in the transport and/or generation of antigenic peptides to the capacity of tumor cells to evade immunosurveillance and provide a unique model system to dissect this phenomenon. The Rockefeller University Press 1994-10-01 /pmc/articles/PMC2191686/ /pubmed/7931074 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing
title Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing
title_full Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing
title_fullStr Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing
title_full_unstemmed Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing
title_short Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing
title_sort comparison of cell lines deficient in antigen presentation reveals a functional role for tap-1 alone in antigen processing
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2191686/
https://www.ncbi.nlm.nih.gov/pubmed/7931074