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Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention
We have recently shown that the accumulation of diverse viral and cellular membrane proteins in the ER activates the higher eukaryotic transcription factor NF-kappaB. This defined a novel ER-nuclear signal transduction pathway, which is distinct from the previously described unfolded protein respons...
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Lenguaje: | English |
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The Rockefeller University Press
1996
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2199876/ https://www.ncbi.nlm.nih.gov/pubmed/8647884 |
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collection | PubMed |
description | We have recently shown that the accumulation of diverse viral and cellular membrane proteins in the ER activates the higher eukaryotic transcription factor NF-kappaB. This defined a novel ER-nuclear signal transduction pathway, which is distinct from the previously described unfolded protein response (UPR). The well characterized UPR pathway is activated by the presence of un- or malfolded proteins in the ER. In contrast, the ER stress signal which activates the NF-kappaB pathway is not known. Here we used the adenovirus early region protein E3/19K as a model to investigate the nature of the NF-kappaB-activating signal emitted by the ER. E3/19K resides in the endoplasmic reticulum where it binds to MHC class I molecules, thereby preventing their transport to the cell surface. It is maintained in the ER by a retention signal sequence in its carboxy terminus, which causes the protein to be continuously retrieved to the ER from post-ER compartments. Mutation of this sequence allows E3/19K to reach the cell surface. We show here that expression of E3/19K potently activates a functional NF-kappaB transcription factor. The activated NF-kappaB complexes contained p50/p65 and p50/c-rel heterodimers. E3/19K interaction with MHC class I was not important for NF-kappaB activation since mutant proteins which no longer bind MHC molecules remained fully capable of inducing NF- kappaB. However, activation of both NF-kappaB DNA binding and kappaB- dependent transactivation relied on E3/19K ER retention: mutants, which were expressed on the cell surface, could no longer activate the transcription factor. This identifies the NF-kappaB-activating signal as the accumulation of proteins in the ER membrane, a condition we have termed "ER overload." We show that ER overload-mediated NF-kappaB activation but not TNF-stimulated NF-kappaB induction can be inhibited by the intracellular Ca2+ chelator TMB-8. Moreover, treatment of cells with two inhibitors of the ER-resident Ca(2+) -dependent ATPase, thapsigargin and cyclopiazonic acid, which causes a rapid release of Ca2+ from the ER, strongly activated NF-kappaB. We therefore propose that ER overload activates NF-kappaB by causing Ca2+ release from the ER. Because NF-kappaB plays a key role in mounting an immune response, ER overload caused by viral proteins may constitute a simple antiviral response with broad specificity. |
format | Text |
id | pubmed-2199876 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1996 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-21998762008-05-01 Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention J Cell Biol Articles We have recently shown that the accumulation of diverse viral and cellular membrane proteins in the ER activates the higher eukaryotic transcription factor NF-kappaB. This defined a novel ER-nuclear signal transduction pathway, which is distinct from the previously described unfolded protein response (UPR). The well characterized UPR pathway is activated by the presence of un- or malfolded proteins in the ER. In contrast, the ER stress signal which activates the NF-kappaB pathway is not known. Here we used the adenovirus early region protein E3/19K as a model to investigate the nature of the NF-kappaB-activating signal emitted by the ER. E3/19K resides in the endoplasmic reticulum where it binds to MHC class I molecules, thereby preventing their transport to the cell surface. It is maintained in the ER by a retention signal sequence in its carboxy terminus, which causes the protein to be continuously retrieved to the ER from post-ER compartments. Mutation of this sequence allows E3/19K to reach the cell surface. We show here that expression of E3/19K potently activates a functional NF-kappaB transcription factor. The activated NF-kappaB complexes contained p50/p65 and p50/c-rel heterodimers. E3/19K interaction with MHC class I was not important for NF-kappaB activation since mutant proteins which no longer bind MHC molecules remained fully capable of inducing NF- kappaB. However, activation of both NF-kappaB DNA binding and kappaB- dependent transactivation relied on E3/19K ER retention: mutants, which were expressed on the cell surface, could no longer activate the transcription factor. This identifies the NF-kappaB-activating signal as the accumulation of proteins in the ER membrane, a condition we have termed "ER overload." We show that ER overload-mediated NF-kappaB activation but not TNF-stimulated NF-kappaB induction can be inhibited by the intracellular Ca2+ chelator TMB-8. Moreover, treatment of cells with two inhibitors of the ER-resident Ca(2+) -dependent ATPase, thapsigargin and cyclopiazonic acid, which causes a rapid release of Ca2+ from the ER, strongly activated NF-kappaB. We therefore propose that ER overload activates NF-kappaB by causing Ca2+ release from the ER. Because NF-kappaB plays a key role in mounting an immune response, ER overload caused by viral proteins may constitute a simple antiviral response with broad specificity. The Rockefeller University Press 1996-02-02 /pmc/articles/PMC2199876/ /pubmed/8647884 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 Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention |
title | Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention |
title_full | Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention |
title_fullStr | Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention |
title_full_unstemmed | Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention |
title_short | Activation of transcription factor NF-kappaB by the adenovirus E3/19K protein requires its ER retention |
title_sort | activation of transcription factor nf-kappab by the adenovirus e3/19k protein requires its er retention |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2199876/ https://www.ncbi.nlm.nih.gov/pubmed/8647884 |