Cargando…
TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel
In mammalian cells, one-third of all polypeptides is transported into or through the ER-membrane via the Sec61-channel. While the Sec61-complex facilitates the transport of all polypeptides with amino-terminal signal peptides (SP) or SP-equivalent transmembrane helices (TMH), the translocating chain...
Autores principales: | , , , , , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Taylor & Francis
2020
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039644/ https://www.ncbi.nlm.nih.gov/pubmed/32013668 http://dx.doi.org/10.1080/19336950.2020.1724759 |
_version_ | 1783500842836426752 |
---|---|
author | Klein, Marie-Christine Lerner, Monika Nguyen, Duy Pfeffer, Stefan Dudek, Johanna Förster, Friedrich Helms, Volkhard Lang, Sven Zimmermann, Richard |
author_facet | Klein, Marie-Christine Lerner, Monika Nguyen, Duy Pfeffer, Stefan Dudek, Johanna Förster, Friedrich Helms, Volkhard Lang, Sven Zimmermann, Richard |
author_sort | Klein, Marie-Christine |
collection | PubMed |
description | In mammalian cells, one-third of all polypeptides is transported into or through the ER-membrane via the Sec61-channel. While the Sec61-complex facilitates the transport of all polypeptides with amino-terminal signal peptides (SP) or SP-equivalent transmembrane helices (TMH), the translocating chain-associated membrane protein (now termed TRAM1) was proposed to support transport of a subset of precursors. To identify possible determinants of TRAM1 substrate specificity, we systematically identified TRAM1-dependent precursors by analyzing cellular protein abundance changes upon TRAM1 depletion in HeLa cells using quantitative label-free proteomics. In contrast to previous analysis after TRAP depletion, SP and TMH analysis of TRAM1 clients did not reveal any distinguishing features that could explain its putative substrate specificity. To further address the TRAM1 mechanism, live-cell calcium imaging was carried out after TRAM1 depletion in HeLa cells. In additional contrast to previous analysis after TRAP depletion, TRAM1 depletion did not affect calcium leakage from the ER. Thus, TRAM1 does not appear to act as SP- or TMH-receptor on the ER-membrane’s cytosolic face and does not appear to affect the open probability of the Sec61-channel. It may rather play a supportive role in protein transport, such as making the phospholipid bilayer conducive for accepting SP and TMH in the vicinity of the lateral gate of the Sec61-channel. Abbreviations: ER, endoplasmic reticulum; OST, oligosaccharyltransferase; RAMP, ribosome-associated membrane protein; SP, signal peptide; SR, SRP-receptor; SRP, signal recognition particle; TMH, signal peptide-equivalent transmembrane helix; TRAM, translocating chain-associated membrane protein; TRAP, translocon-associated protein. |
format | Online Article Text |
id | pubmed-7039644 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | Taylor & Francis |
record_format | MEDLINE/PubMed |
spelling | pubmed-70396442020-03-03 TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel Klein, Marie-Christine Lerner, Monika Nguyen, Duy Pfeffer, Stefan Dudek, Johanna Förster, Friedrich Helms, Volkhard Lang, Sven Zimmermann, Richard Channels (Austin) Research Paper In mammalian cells, one-third of all polypeptides is transported into or through the ER-membrane via the Sec61-channel. While the Sec61-complex facilitates the transport of all polypeptides with amino-terminal signal peptides (SP) or SP-equivalent transmembrane helices (TMH), the translocating chain-associated membrane protein (now termed TRAM1) was proposed to support transport of a subset of precursors. To identify possible determinants of TRAM1 substrate specificity, we systematically identified TRAM1-dependent precursors by analyzing cellular protein abundance changes upon TRAM1 depletion in HeLa cells using quantitative label-free proteomics. In contrast to previous analysis after TRAP depletion, SP and TMH analysis of TRAM1 clients did not reveal any distinguishing features that could explain its putative substrate specificity. To further address the TRAM1 mechanism, live-cell calcium imaging was carried out after TRAM1 depletion in HeLa cells. In additional contrast to previous analysis after TRAP depletion, TRAM1 depletion did not affect calcium leakage from the ER. Thus, TRAM1 does not appear to act as SP- or TMH-receptor on the ER-membrane’s cytosolic face and does not appear to affect the open probability of the Sec61-channel. It may rather play a supportive role in protein transport, such as making the phospholipid bilayer conducive for accepting SP and TMH in the vicinity of the lateral gate of the Sec61-channel. Abbreviations: ER, endoplasmic reticulum; OST, oligosaccharyltransferase; RAMP, ribosome-associated membrane protein; SP, signal peptide; SR, SRP-receptor; SRP, signal recognition particle; TMH, signal peptide-equivalent transmembrane helix; TRAM, translocating chain-associated membrane protein; TRAP, translocon-associated protein. Taylor & Francis 2020-02-11 /pmc/articles/PMC7039644/ /pubmed/32013668 http://dx.doi.org/10.1080/19336950.2020.1724759 Text en © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. https://creativecommons.org/licenses/by-nc/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/ (https://creativecommons.org/licenses/by-nc/4.0/) ), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Paper Klein, Marie-Christine Lerner, Monika Nguyen, Duy Pfeffer, Stefan Dudek, Johanna Förster, Friedrich Helms, Volkhard Lang, Sven Zimmermann, Richard TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel |
title | TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel |
title_full | TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel |
title_fullStr | TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel |
title_full_unstemmed | TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel |
title_short | TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel |
title_sort | tram1 protein may support er protein import by modulating the phospholipid bilayer near the lateral gate of the sec61-channel |
topic | Research Paper |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039644/ https://www.ncbi.nlm.nih.gov/pubmed/32013668 http://dx.doi.org/10.1080/19336950.2020.1724759 |
work_keys_str_mv | AT kleinmariechristine tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT lernermonika tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT nguyenduy tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT pfefferstefan tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT dudekjohanna tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT forsterfriedrich tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT helmsvolkhard tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT langsven tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel AT zimmermannrichard tram1proteinmaysupporterproteinimportbymodulatingthephospholipidbilayernearthelateralgateofthesec61channel |