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Abstract
Folding of proteins is essential so that they can exert their functions. For proteins that transit the secretory pathway, folding occurs in the endoplasmic reticulum (ER) and various chaperone systems assist in acquiring their correct folding/subunit formation. N-glycosylation is one of the most conserved posttranslational modification for proteins, and in eukaryotes it occurs in the ER. Consequently, eukaryotic cells have developed various systems that utilize N-glycans to dictate and assist protein folding, or if they consistently fail to fold properly, to destroy proteins for quality control and the maintenance of homeostasis of proteins in the ER.
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Annaert W, Kaether C. Bring it back, bring it back, don't take it away from me - the sorting receptor RER1. J Cell Sci 2020; 133:133/17/jcs231423. [PMID: 32873699 DOI: 10.1242/jcs.231423] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The quote "bring it back, bring it back, don't take it away from me" from Queen's Love of my life describes the function of the sorting receptor RER1, a 23 kDa protein with four transmembrane domains (TMDs) that localizes to the intermediate compartment and the cis-Golgi. From there it returns escaped proteins that are not supposed to leave the endoplasmic reticulum (ER) back to it. Unique about RER1 is its ability to recognize its ligands through binding motifs in TMDs. Among its substrates are ER-resident proteins, as well as unassembled subunits of multimeric complexes that are retrieved back into the ER, this way guarding the full assembly of their respective complexes. The basic mechanisms for RER1-dependent retrieval have been already elucidated some years ago in yeast. More recently, several important cargoes of RER1 have been described in mammalian cells, and the in vivo role of RER1 is being unveiled by using mouse models. In this Review, we give an overview of the cell biology of RER1 in different models, discuss its controversial role in the brain and provide an outlook on future directions for RER1 research.
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Affiliation(s)
- Wim Annaert
- VIB Center for Brain and Disease Research & KU Leuven, Department of Neurosciences, Gasthuisberg, B-3000 Leuven, Belgium
| | - Christoph Kaether
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, 07745 Jena, Germany
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Zhang J, Wu J, Liu L, Li J. The Crucial Role of Demannosylating Asparagine-Linked Glycans in ERADicating Misfolded Glycoproteins in the Endoplasmic Reticulum. FRONTIERS IN PLANT SCIENCE 2020; 11:625033. [PMID: 33510762 PMCID: PMC7835635 DOI: 10.3389/fpls.2020.625033] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 12/08/2020] [Indexed: 05/04/2023]
Abstract
Most membrane and secreted proteins are glycosylated on certain asparagine (N) residues in the endoplasmic reticulum (ER), which is crucial for their correct folding and function. Protein folding is a fundamentally inefficient and error-prone process that can be easily interfered by genetic mutations, stochastic cellular events, and environmental stresses. Because misfolded proteins not only lead to functional deficiency but also produce gain-of-function cellular toxicity, eukaryotic organisms have evolved highly conserved ER-mediated protein quality control (ERQC) mechanisms to monitor protein folding, retain and repair incompletely folded or misfolded proteins, or remove terminally misfolded proteins via a unique ER-associated degradation (ERAD) mechanism. A crucial event that terminates futile refolding attempts of a misfolded glycoprotein and diverts it into the ERAD pathway is executed by removal of certain terminal α1,2-mannose (Man) residues of their N-glycans. Earlier studies were centered around an ER-type α1,2-mannosidase that specifically cleaves the terminal α1,2Man residue from the B-branch of the three-branched N-linked Man9GlcNAc2 (GlcNAc for N-acetylglucosamine) glycan, but recent investigations revealed that the signal that marks a terminally misfolded glycoprotein for ERAD is an N-glycan with an exposed α1,6Man residue generated by members of a unique folding-sensitive α1,2-mannosidase family known as ER-degradation enhancing α-mannosidase-like proteins (EDEMs). This review provides a historical recount of major discoveries that led to our current understanding on the role of demannosylating N-glycans in sentencing irreparable misfolded glycoproteins into ERAD. It also discusses conserved and distinct features of the demannosylation processes of the ERAD systems of yeast, mammals, and plants.
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Affiliation(s)
- Jianjun Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Jiarui Wu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Linchuan Liu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Jianming Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States
- *Correspondence: Jianming Li, ;
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A signal motif retains Arabidopsis ER-α-mannosidase I in the cis-Golgi and prevents enhanced glycoprotein ERAD. Nat Commun 2019; 10:3701. [PMID: 31420549 PMCID: PMC6697737 DOI: 10.1038/s41467-019-11686-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 07/01/2019] [Indexed: 11/09/2022] Open
Abstract
The Arabidopsis ER-α-mannosidase I (MNS3) generates an oligomannosidic N-glycan structure that is characteristically found on ER-resident glycoproteins. The enzyme itself has so far not been detected in the ER. Here, we provide evidence that in plants MNS3 exclusively resides in the Golgi apparatus at steady-state. Notably, MNS3 remains on dispersed punctate structures when subjected to different approaches that commonly result in the relocation of Golgi enzymes to the ER. Responsible for this rare behavior is an amino acid signal motif (LPYS) within the cytoplasmic tail of MNS3 that acts as a specific Golgi retention signal. This retention is a means to spatially separate MNS3 from ER-localized mannose trimming steps that generate the glycan signal required for flagging terminally misfolded glycoproteins for ERAD. The physiological importance of the very specific MNS3 localization is demonstrated here by means of a structurally impaired variant of the brassinosteroid receptor BRASSINOSTEROID INSENSITIVE 1. The Arabidopsis ER-α-mannosidase I MNS3 generates N-glycan structures typical of ER-resident glycoproteins. Here Schoberer et al. identify a novel motif that anchors MNS3 to the cis-Golgi, spatially separating MNS3 from ER-localized mannose trimming associated with the ER-associated degradation pathway.
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Tunicamycin Sensitivity-Suppression by High Gene Dosage Reveals New Functions of the Yeast Hog1 MAP Kinase. Cells 2019; 8:cells8070710. [PMID: 31336877 PMCID: PMC6678945 DOI: 10.3390/cells8070710] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 07/03/2019] [Accepted: 07/09/2019] [Indexed: 01/10/2023] Open
Abstract
In the yeast Saccharomyces cerevisiae, components of the High Osmolarity Glycerol (HOG) pathway are important for the response to diverse stresses including response to endoplasmic reticulum stress (ER stress), which is produced by the accumulation of unfolded proteins in the lumen of this organelle. Accumulation of unfolded proteins may be due to the inhibition of protein N-glycosylation, which can be achieved by treatment with the antibiotic tunicamycin (Tn). In this work we were interested in finding proteins involved in the ER stress response regulated by Hog1, the mitogen activated protein kinase (MAPK) of the HOG pathway. A high gene dosage suppression screening allowed us to identify genes that suppressed the sensitivity to Tn shown by a hog1Δ mutant. The suppressors participate in a limited number of cellular processes, including lipid/carbohydrate biosynthesis and protein glycosylation, vesicle-mediated transport and exocytosis, cell wall organization and biogenesis, and cell detoxification processes. The finding of suppressors Rer2 and Srt1, which participate in the dolichol biosynthesis pathway revealed that the hog1Δ strain has a defective polyprenol metabolism. This work uncovers new genetic and functional interactors of Hog1 and contributes to a better understanding of the participation of this MAPK in the ER stress response.
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Chen S, Zhang J, Chen J, Wang Y, Zhou S, Huang L, Bai Y, Peng C, Shen B, Chen H, Tian Y. RER1 enhances carcinogenesis and stemness of pancreatic cancer under hypoxic environment. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2019; 38:15. [PMID: 30630537 PMCID: PMC6327509 DOI: 10.1186/s13046-018-0986-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 11/29/2018] [Indexed: 12/14/2022]
Abstract
Background Increasing incidence and mortality rates of pancreatic cancer (PC) highlight an urgent need for novel and efficient drugs. Retention in endoplasmic reticulum 1 (RER1) is an important retention factor in the endoplasmic reticulum (ER). However, it remains elusive whether RER1 is involved in the retention of disease-related proteins. Methods We analyzed the expression level of RER1 in PC and adjacent tissues, and also employed Kaplan–Meier’s analysis to identify the correlation between RER1 expression and overall survival rate. Cell proliferation, colony formation, tumor formation, scratch test, and transwell invasion assays were performed in RER1 knockdown cells and negative control cells. Results We hereby reported the important functions of RER1 in tumorigenesis and metastasis of PC, evidenced by inhibitory effects of RER1 knockdown on PC cell proliferation, migration and aggressiveness. Tumor formation was also significantly repressed in RER1 knockdown cells compared to control. Hypoxia-inducible factor (HIF)-1α was found to be an upstream regulator of RER1. Knockdown HIF-1α cells exhibited similar repressive impact on cell proliferation as RER1, and showed diminished migratory and invasive abilities under hypoxic condition. Conclusion The present study has demonstrated that RER1 enhances the progression of PC through promoting cell proliferation, migration and aggressiveness.
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Affiliation(s)
- Shi Chen
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China.,Department of Pancreatic Surgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200025, People's Republic of China
| | - Jiaqiang Zhang
- Department of Pancreatic Surgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200025, People's Republic of China
| | - Jiangzhi Chen
- Department of Hepatobiliary Surgery, Union Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China
| | - Yaodong Wang
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China
| | - Songqiang Zhou
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China
| | - Long Huang
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China
| | - Yannan Bai
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China
| | - Chenghong Peng
- Department of Pancreatic Surgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200025, People's Republic of China
| | - Baiyong Shen
- Department of Pancreatic Surgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200025, People's Republic of China.
| | - Huixing Chen
- Department of Hepatobiliary Surgery, Union Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China.
| | - Yifeng Tian
- Department of Hepatobiliary Surgery, Fujian Provincial Hospital, Fujian Medical University, Fuzhou, 350001, People's Republic of China.
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Ponsero AJ, Igbaria A, Darch MA, Miled S, Outten CE, Winther JR, Palais G, D'Autréaux B, Delaunay-Moisan A, Toledano MB. Endoplasmic Reticulum Transport of Glutathione by Sec61 Is Regulated by Ero1 and Bip. Mol Cell 2017; 67:962-973.e5. [PMID: 28918898 DOI: 10.1016/j.molcel.2017.08.012] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 06/29/2017] [Accepted: 08/18/2017] [Indexed: 10/18/2022]
Abstract
In the endoplasmic reticulum (ER), Ero1 catalyzes disulfide bond formation and promotes glutathione (GSH) oxidation to GSSG. Since GSSG cannot be reduced in the ER, maintenance of the ER glutathione redox state and levels likely depends on ER glutathione import and GSSG export. We used quantitative GSH and GSSG biosensors to monitor glutathione import into the ER of yeast cells. We found that glutathione enters the ER by facilitated diffusion through the Sec61 protein-conducting channel, while oxidized Bip (Kar2) inhibits transport. Increased ER glutathione import triggers H2O2-dependent Bip oxidation through Ero1 reductive activation, which inhibits glutathione import in a negative regulatory loop. During ER stress, transport is activated by UPR-dependent Ero1 induction, and cytosolic glutathione levels increase. Thus, the ER redox poise is tuned by reciprocal control of glutathione import and Ero1 activation. The ER protein-conducting channel is permeable to small molecules, provided the driving force of a concentration gradient.
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Affiliation(s)
- Alise J Ponsero
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France
| | - Aeid Igbaria
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France
| | - Maxwell A Darch
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
| | - Samia Miled
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France
| | - Caryn E Outten
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
| | - Jakob R Winther
- Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Gael Palais
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France
| | - Benoit D'Autréaux
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France
| | - Agnès Delaunay-Moisan
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France
| | - Michel B Toledano
- Institute for Integrative Biology of the Cell (I2BC), CEA-Saclay, CNRS, Université Paris-Saclay, ISVJC/SBIGEM, Laboratoire Stress Oxydant et Cancer, 91191 Gif-sur-Yvette, France.
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The ER retention protein RER1 promotes alpha-synuclein degradation via the proteasome. PLoS One 2017; 12:e0184262. [PMID: 28877262 PMCID: PMC5587320 DOI: 10.1371/journal.pone.0184262] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 08/21/2017] [Indexed: 11/19/2022] Open
Abstract
Abnormal accumulation of α-synuclein (αSyn) has been linked to endoplasmic-reticulum (ER) stress, defective intracellular protein/vesicle trafficking, and cytotoxicity. Targeting factors involved in ER-related protein processing and trafficking may, therefore, be a key to modulating αSyn levels and associated toxicity. Recently retention in endoplasmic reticulum 1 (RER1) has been identified as an important ER retrieval/retention factor for Alzheimer's disease proteins and negatively regulates amyloid-β peptide levels. Here, we hypothesized that RER1 might also play an important role in retention/retrieval of αSyn and mediate levels. We expressed RER1 and a C-terminal mutant RER1Δ25, which lacks the ER retention/retrieval function, in HEK293 and H4 neuroglioma cells. RER1 overexpression significantly decreased levels of both wild type and A30P, A53T, and E46K disease causal mutants of αSyn, whereas the RER1Δ25 mutant had a significantly attenuated effect on αSyn. RER1 effects were specific to αSyn and had little to no effect on either βSyn or the Δ71-82 αSyn mutant, which both lack the NAC domain sequence critical for synuclein fibrillization. Tests with proteasomal and macroautophagy inhibitors further demonstrate that RER1 effects on αSyn are primarily mediated through the ubiquitin-proteasome system. RER1 also appears to interact with the ubiquitin ligase NEDD4. RER1 in human diseased brain tissues co-localizes with αSyn-positive Lewy bodies. Together, these findings provide evidence that RER1 is a novel and potential important mediator of elevated αSyn levels. Further investigation of the mechanism of RER1 and downstream effectors on αSyn may yield novel therapeutic targets for modulation in Parkinson disease and related synucleinopathies.
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Benyair R, Ogen-Shtern N, Mazkereth N, Shai B, Ehrlich M, Lederkremer GZ. Mammalian ER mannosidase I resides in quality control vesicles, where it encounters its glycoprotein substrates. Mol Biol Cell 2014; 26:172-84. [PMID: 25411339 PMCID: PMC4294666 DOI: 10.1091/mbc.e14-06-1152] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
ER mannosidase I (ERManI) was found recently in the Golgi. This result is found to arise artificially from membrane disturbance in immunofluorescence methods. ERManI is located in novel vesicles to which substrates traffic and that converge at the ER-derived quality control compartment under ER stress. Endoplasmic reticulum α1,2 mannosidase I (ERManI), a central component of ER quality control and ER-associated degradation (ERAD), acts as a timer enzyme, modifying N-linked sugar chains of glycoproteins with time. This process halts glycoprotein folding attempts when necessary and targets terminally misfolded glycoproteins to ERAD. Despite the importance of ERManI in maintenance of glycoprotein quality control, fundamental questions regarding this enzyme remain controversial. One such question is the subcellular localization of ERManI, which has been suggested to localize to the ER membrane, the ER-derived quality control compartment (ERQC), and, surprisingly, recently to the Golgi apparatus. To try to clarify this controversy, we applied a series of approaches that indicate that ERManI is located, at the steady state, in quality control vesicles (QCVs) to which ERAD substrates are transported and in which they interact with the enzyme. Both endogenous and exogenously expressed ERManI migrate at an ER-like density on iodixanol gradients, suggesting that the QCVs are derived from the ER. The QCVs are highly mobile, displaying dynamics that are dependent on microtubules and COP-II but not on COP-I vesicle machinery. Under ER stress conditions, the QCVs converge in a juxtanuclear region, at the ERQC, as previously reported. Our results also suggest that ERManI is turned over by an active autophagic process. Of importance, we found that membrane disturbance, as is common in immunofluorescence methods, leads to an artificial appearance of ERManI in a Golgi pattern.
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Affiliation(s)
- Ron Benyair
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Navit Ogen-Shtern
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Niv Mazkereth
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ben Shai
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Gerardo Z Lederkremer
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Park HJ, Shabashvili D, Nekorchuk MD, Shyqyriu E, Jung JI, Ladd TB, Moore BD, Felsenstein KM, Golde TE, Kim SH. Retention in endoplasmic reticulum 1 (RER1) modulates amyloid-β (Aβ) production by altering trafficking of γ-secretase and amyloid precursor protein (APP). J Biol Chem 2012; 287:40629-40. [PMID: 23043097 PMCID: PMC3504776 DOI: 10.1074/jbc.m112.418442] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 10/05/2012] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Aβ production is influenced by intracellular trafficking of secretases and amyloid precursor protein (APP). RESULTS Retention in endoplasmic reticulum 1 (RER1) regulates the trafficking of γ-secretase and APP, thereby influences Aβ production. CONCLUSION RER1, an ER retention/retrieval factor for γ-secretase and APP, modulates Aβ production. SIGNIFICANCE RER1 and its influence on γ-secretase and APP may be implicated for a safe strategy to target Aβ production. The presence of neuritic plaques containing aggregated amyloid-β (Aβ) peptides in the brain parenchyma is a pathological hallmark of Alzheimer disease (AD). Aβ is generated by sequential cleavage of the amyloid β precursor protein (APP) by β- and γ-secretase, respectively. As APP processing to Aβ requires transport through the secretory pathway, trafficking of the substrate and access to the secretases are key factors that can influence Aβ production (Thinakaran, G., and Koo, E. H. (2008) Amyloid precursor protein trafficking, processing, and function. J. Biol. Chem. 283, 29615-29619). Here, we report that retention in endoplasmic reticulum 1 (RER1) associates with γ-secretase in early secretory compartments and regulates the intracellular trafficking of γ-secretase. RER1 overexpression decreases both γ-secretase localization on the cell surface and Aβ secretion and conversely RER1 knockdown increases the level of cell surface γ-secretase and increases Aβ secretion. Furthermore, we find that increased RER1 levels decrease mature APP and increase immature APP, resulting in less surface accumulation of APP. These data show that RER1 influences the trafficking and localization of both γ-secretase and APP, thereby regulating the production and secretion of Aβ peptides.
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Affiliation(s)
- Hyo-Jin Park
- From the Department of Pharmacology and Therapeutics, and
- the Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610
| | | | | | - Eva Shyqyriu
- From the Department of Pharmacology and Therapeutics, and
| | - Joo In Jung
- the Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610
| | - Thomas B. Ladd
- the Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610
| | - Brenda D. Moore
- the Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610
| | - Kevin M. Felsenstein
- the Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610
| | - Todd E. Golde
- the Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610
| | - Seong-Hun Kim
- From the Department of Pharmacology and Therapeutics, and
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Abstract
Estimates based on proteomic analyses indicate that a third of translated proteins in eukaryotic genomes enter the secretory pathway. After folding and assembly of nascent secretory proteins in the endoplasmic reticulum (ER), the coat protein complex II (COPII) selects folded cargo for export in membrane-bound vesicles. To accommodate the great diversity in secretory cargo, protein sorting receptors are required in a number of instances for efficient ER export. These transmembrane sorting receptors couple specific secretory cargo to COPII through interactions with both cargo and coat subunits. After incorporation into COPII transport vesicles, protein sorting receptors release bound cargo in pre-Golgi or Golgi compartments, and receptors are then recycled back to the ER for additional rounds of cargo export. Distinct types of protein sorting receptors that recognize carbohydrate and/or polypeptide signals in secretory cargo have been characterized. Our current understanding of the molecular mechanisms underlying cargo receptor function are described.
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Affiliation(s)
- Julia Dancourt
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Sato M, Sato K, Nakano A. Endoplasmic reticulum quality control of unassembled iron transporter depends on Rer1p-mediated retrieval from the golgi. Mol Biol Cell 2004; 15:1417-24. [PMID: 14699055 PMCID: PMC363159 DOI: 10.1091/mbc.e03-10-0765] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2003] [Revised: 12/02/2003] [Accepted: 12/02/2003] [Indexed: 11/11/2022] Open
Abstract
Endoplasmic reticulum (ER) quality control is a conserved process by which misfolded or unassembled proteins are selectively retained in the endoplasmic reticulum (ER). Failure in oligomerization of multisubunit membrane proteins is one of the events that triggers ER quality control. The transmembrane domains (TMDs) of unassembled subunits are determinants of ER retention in many cases, although the mechanism of the TMD-mediated sorting of unassembled subunits remains elusive. We studied a yeast iron transporter complex on the cell surface as a new model system for ER quality control. When Fet3p, a transmembrane subunit, is not assembled with the other membrane subunit, Ftr1p, unassembled Fet3p is exclusively localized to the ER at steady state. The TMD of Fet3p contains a determinant for this process. However, pulse-chase analysis and in vitro budding assays indicate that unassembled Fet3p rapidly escapes from the ER. Furthermore, Rer1p, a retrieval receptor for ER-resident membrane proteins in the Golgi, is responsible for the TMD-dependent ER retrieval of unassembled Fet3p. These findings provide clear evidence that the ER quality control of unassembled membrane proteins can be achieved by retrieval from the Golgi and that Rer1p serves as a specific sorting receptor in this process.
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Affiliation(s)
- Miyuki Sato
- Molecular Membrane Biology Laboratory, RIKEN Discovery Research Institute, Saitama 351-0198, Japan
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13
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Sato K, Sato M, Nakano A. Rer1p, a retrieval receptor for ER membrane proteins, recognizes transmembrane domains in multiple modes. Mol Biol Cell 2003; 14:3605-16. [PMID: 12972550 PMCID: PMC196553 DOI: 10.1091/mbc.e02-12-0777] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The yeast Golgi membrane protein Rer1p is required for the retrieval of various endoplasmic reticulum (ER) membrane proteins such as Sec12p and Sec71p to the ER. We demonstrate here that the transmembrane domain (TMD) of Sec71p, a type-III membrane protein, contains an ER localization signal, which is required for physical recognition by Rer1p. The Sec71TMD-GFP fusion protein is efficiently retrieved to the ER by Rer1p. The structural feature of this TMD signal turns out to be the spatial location of polar residues flanking the highly hydrophobic core sequence but not the whole length of the TMD. On the Rer1p side, Tyr152 residue in the 4th TMD is important for the recognition of Sec12p but not Sec71p, suggesting that Rer1p interacts with its ligands at least in two modes. Sec71TMD-GFP expressed in the Deltarer1 mutant cells is mislocalized from the ER to the lumen of vacuoles via the multivesicular body (MVB) sorting pathway. In this case, not only the presence of polar residues in the Sec71TMD but also the length of the TMD is critical for the MVB sorting. Thus, the Rer1p-dependent ER retrieval and the MVB sorting in late endosomes both watch polar residues in the TMD but in a different manner.
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Affiliation(s)
- Ken Sato
- Molecular Membrane Biology Laboratory, Discovery Research Institute, Riken, Wako, Saitama 351-0198, Japan.
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Massaad MJ, Herscovics A. Interaction of the endoplasmic reticulum α1,2-mannosidase Mns1p with Rer1p using the split-ubiquitin system. J Cell Sci 2001; 114:4629-35. [PMID: 11792827 DOI: 10.1242/jcs.114.24.4629] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The α1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae is a type II membrane protein of the endoplasmic reticulum. The localization of Mns1p depends on retrieval from the Golgi through a mechanism that involves Rer1p. A chimera consisting of the transmembrane domain of Mns1p fused to the catalytic domain of the Golgi α1,2-mannosyltransferase Kre2p was localized in the endoplasmic reticulum of Δpep4 cells and in the vacuoles of rer1/Δpep4 by indirect immunofluorescence. The split-ubiquitin system was used to determine if there is an interaction between Mns1p and Rer1p in vivo. Co-expression of NubG-Mns1p and Rer1p-Cub-protein A-lexA-VP16 in L40 yeast cells resulted in cleavage of the reporter molecule, protein A-lexA-VP16, detected by western blot analysis and by expression of β-galactosidase activity. Sec12p, another endoplasmic reticulum protein that depends on Rer1p for its localization, also interacted with Rer1p using the split-ubiquitin assay, whereas the endoplasmic reticulum protein Ost1p showed no interaction. A weak interaction was observed between Alg5p and Rer1p. These results demonstrate that the transmembrane domain of Mns1p is sufficient for Rer1p-dependent endoplasmic reticulum localization and that Mns1p and Rer1p interact. Furthermore, the split-ubiquitin system demonstrates that the C-terminal of Rer1p is in the cytosol.
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Affiliation(s)
- M J Massaad
- McGill Cancer Centre, McGill University, Montréal, Québec H3G 1Y6, Canada
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15
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Sato K, Sato M, Nakano A. Rer1p, a retrieval receptor for endoplasmic reticulum membrane proteins, is dynamically localized to the Golgi apparatus by coatomer. J Cell Biol 2001; 152:935-44. [PMID: 11238450 PMCID: PMC2198819 DOI: 10.1083/jcb.152.5.935] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rer1p, a yeast Golgi membrane protein, is required for the retrieval of a set of endoplasmic reticulum (ER) membrane proteins. We present the first evidence that Rer1p directly interacts with the transmembrane domain (TMD) of Sec12p which contains a retrieval signal. A green fluorescent protein (GFP) fusion of Rer1p rapidly cycles between the Golgi and the ER. Either a lesion of coatomer or deletion of the COOH-terminal tail of Rer1p causes its mislocalization to the vacuole. The COOH-terminal Rer1p tail interacts in vitro with a coatomer complex containing alpha and gamma subunits. These findings not only give the proof that Rer1p is a novel type of retrieval receptor recognizing the TMD in the Golgi but also indicate that coatomer actively regulates the function and localization of Rer1p.
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Affiliation(s)
- K Sato
- Molecular Membrane Biology Laboratory, RIKEN (The Institute of Physical and Chemical Research), Saitama 351-0198, Japan.
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16
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Szczesna-Skorupa E, Kemper B. Endoplasmic reticulum retention determinants in the transmembrane and linker domains of cytochrome P450 2C1. J Biol Chem 2000; 275:19409-15. [PMID: 10781599 DOI: 10.1074/jbc.m002394200] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytochrome P450 2C1 N-terminal signal anchor sequence mediates direct retention of the protein in the endoplasmic reticulum and consists of a hydrophobic transmembrane domain, residues 3-20, followed by a hydrophilic linker, residues 21-28. Fusions of the N-terminal 21 or 28 amino acids of P450 2C1 to green fluorescent protein resulted in endoplasmic reticulum localization of the chimera in transfected cells. Disruption of microtubules by nocodazole treatment resulted in redistribution into a punctate pattern for the 1-21, but not for the 1-28, chimera indicating that the linker was preventing transport from the endoplasmic reticulum but was not required for retrieval to the endoplasmic reticulum from the pre-Golgi compartment. In the 1-28 chimera, mutations of residues 21-23 (KQS) in the linker resulted in redistribution of the chimera after nocodazole treatment. Mutations in the transmembrane domain affected both direct retention in the endoplasmic reticulum and retrieval from the pre-Golgi compartment, and although structural requirements for each process are distinct, in both cases the arrangement of amino acids and distribution of hydrophobicity are critical. In contrast, the linker region exhibits a sequence-specific requirement for direct retention in the endoplasmic reticulum.
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Affiliation(s)
- E Szczesna-Skorupa
- Departments of Molecular and Integrative Physiology and Cell and Structural Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Vallée F, Lipari F, Yip P, Sleno B, Herscovics A, Howell PL. Crystal structure of a class I alpha1,2-mannosidase involved in N-glycan processing and endoplasmic reticulum quality control. EMBO J 2000; 19:581-8. [PMID: 10675327 PMCID: PMC305596 DOI: 10.1093/emboj/19.4.581] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mannose trimming is not only essential for N-glycan maturation in mammalian cells but also triggers degradation of misfolded glycoproteins. The crystal structure of the class I alpha1, 2-mannosidase that trims Man(9)GlcNAc(2) to Man(8)GlcNAc(2 )isomer B in the endoplasmic reticulum of Saccharomyces cerevisiae reveals a novel (alphaalpha)(7)-barrel in which an N-glycan from one molecule extends into the barrel of an adjacent molecule, interacting with the essential acidic residues and calcium ion. The observed protein-carbohydrate interactions provide the first insight into the catalytic mechanism and specificity of this eukaryotic enzyme family and may be used to design inhibitors that prevent degradation of misfolded glycoproteins in genetic diseases.
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Affiliation(s)
- F Vallée
- Structural Biology and Biochemistry, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, M5G 1X8, Ontario
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