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Combining Auxin-Induced Degradation and RNAi Screening Identifies Novel Genes Involved in Lipid Bilayer Stress Sensing in Caenorhabditis elegans. G3-GENES GENOMES GENETICS 2020; 10:3921-3928. [PMID: 32958476 PMCID: PMC7642917 DOI: 10.1534/g3.120.401635] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Alteration of the lipid composition of biological membranes interferes with their function and can cause tissue damage by triggering apoptosis. Upon lipid bilayer stress, the endoplasmic reticulum mounts a stress response similar to the unfolded protein response. However, only a few genes are known to regulate lipid bilayer stress. We performed a suppressor screen that combined the auxin-inducible degradation (AID) system with conventional RNAi in C. elegans to identify members of the lipid bilayer stress response. AID-mediated degradation of the mediator MDT-15, a protein required for the upregulation of fatty acid desaturases, induced the activation of lipid bilayer stress-sensitive reporters. We screened through most C. elegans kinases and transcription factors by feeding RNAi. We discovered nine genes that suppressed the lipid bilayer stress response in C. elegans. These suppressor genes included drl-1/MAP3K3, gsk-3/GSK3, let-607/CREB3, ire-1/IRE1, and skn-1/NRF1,2,3. Our candidate suppressor genes suggest a network of transcription factors and the integration of multiple tissues for a centralized lipotoxicity response in the intestine. Thus, we demonstrated proof-of-concept for combining AID and RNAi as a new screening strategy and identified eight conserved genes that had not previously been implicated in the lipid bilayer stress response.
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52
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Yap WS, Shyu P, Gaspar ML, Jesch SA, Marvalim C, Prinz WA, Henry SA, Thibault G. The yeast FIT2 homologs are necessary to maintain cellular proteostasis and membrane lipid homeostasis. J Cell Sci 2020; 133:jcs248526. [PMID: 33033181 PMCID: PMC7657468 DOI: 10.1242/jcs.248526] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 10/01/2020] [Indexed: 12/12/2022] Open
Abstract
Lipid droplets (LDs) are implicated in conditions of lipid and protein dysregulation. The fat storage-inducing transmembrane (FIT; also known as FITM) family induces LD formation. Here, we establish a model system to study the role of the Saccharomyces cerevisiae FIT homologues (ScFIT), SCS3 and YFT2, in the proteostasis and stress response pathways. While LD biogenesis and basal endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) remain unaltered in ScFIT mutants, SCS3 was found to be essential for proper stress-induced UPR activation and for viability in the absence of the sole yeast UPR transducer IRE1 Owing to not having a functional UPR, cells with mutated SCS3 exhibited an accumulation of triacylglycerol within the ER along with aberrant LD morphology, suggesting that there is a UPR-dependent compensatory mechanism that acts to mitigate lack of SCS3 Additionally, SCS3 was necessary to maintain phospholipid homeostasis. Strikingly, global protein ubiquitylation and the turnover of both ER and cytoplasmic misfolded proteins is impaired in ScFITΔ cells, while a screen for interacting partners of Scs3 identifies components of the proteostatic machinery as putative targets. Together, our data support a model where ScFITs play an important role in lipid metabolism and proteostasis beyond their defined roles in LD biogenesis.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Wei Sheng Yap
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
| | - Peter Shyu
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
| | - Maria Laura Gaspar
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Stephen A Jesch
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Charlie Marvalim
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
| | - William A Prinz
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Susan A Henry
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Guillaume Thibault
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
- Institute of Molecular and Cell Biology, A*STAR, Singapore, 138673
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53
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Garcia EJ, Liao PC, Tan G, Vevea JD, Sing CN, Tsang CA, McCaffery JM, Boldogh IR, Pon LA. Membrane dynamics and protein targets of lipid droplet microautophagy during ER stress-induced proteostasis in the budding yeast, Saccharomyces cerevisiae. Autophagy 2020. [PMID: 33021864 DOI: 10.1080/15548627.2020.1826691.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022] Open
Abstract
Our previous studies reveal a mechanism for lipid droplet (LD)-mediated proteostasis in the endoplasmic reticulum (ER) whereby unfolded proteins that accumulate in the ER in response to lipid imbalance-induced ER stress are removed by LDs and degraded by microlipophagy (µLP), autophagosome-independent LD uptake into the vacuole (the yeast lysosome). Here, we show that dithiothreitol- or tunicamycin-induced ER stress also induces µLP and identify an unexpected role for vacuolar membrane dynamics in this process. All stressors studied induce vacuolar fragmentation prior to µLP. Moreover, during µLP, fragmented vacuoles fuse to form cup-shaped structures that encapsulate and ultimately take up LDs. Our studies also indicate that proteins of the endosome sorting complexes required for transport (ESCRT) are upregulated, required for µLP, and recruited to LDs, vacuolar membranes, and sites of vacuolar membrane scission during µLP. We identify possible target proteins for LD-mediated ER proteostasis. Our live-cell imaging studies reveal that one potential target (Nup159) localizes to punctate structures that colocalizes with LDs 1) during movement from ER membranes to the cytosol, 2) during microautophagic uptake into vacuoles, and 3) within the vacuolar lumen. Finally, we find that mutations that inhibit LD biogenesis, homotypic vacuolar membrane fusion or ESCRT function inhibit stress-induced autophagy of Nup159 and other ER proteins. Thus, we have obtained the first direct evidence that LDs and µLP can mediate ER stress-induced ER proteostasis, and identified direct roles for ESCRT and vacuolar membrane fusion in that process.
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Affiliation(s)
- Enrique J Garcia
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Pin-Chao Liao
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Gary Tan
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Jason D Vevea
- HHMI and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin, USA
| | - Cierra N Sing
- Institute of Human Nutrition, Columbia University, New York, NY, USA
| | - Catherine A Tsang
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD, USA
| | - Istvan R Boldogh
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Liza A Pon
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
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54
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Garcia EJ, Liao PC, Tan G, Vevea JD, Sing CN, Tsang CA, McCaffery JM, Boldogh IR, Pon LA. Membrane dynamics and protein targets of lipid droplet microautophagy during ER stress-induced proteostasis in the budding yeast, Saccharomyces cerevisiae. Autophagy 2020; 17:2363-2383. [PMID: 33021864 PMCID: PMC8496710 DOI: 10.1080/15548627.2020.1826691] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Our previous studies reveal a mechanism for lipid droplet (LD)-mediated proteostasis in the endoplasmic reticulum (ER) whereby unfolded proteins that accumulate in the ER in response to lipid imbalance-induced ER stress are removed by LDs and degraded by microlipophagy (µLP), autophagosome-independent LD uptake into the vacuole (the yeast lysosome). Here, we show that dithiothreitol- or tunicamycin-induced ER stress also induces µLP and identify an unexpected role for vacuolar membrane dynamics in this process. All stressors studied induce vacuolar fragmentation prior to µLP. Moreover, during µLP, fragmented vacuoles fuse to form cup-shaped structures that encapsulate and ultimately take up LDs. Our studies also indicate that proteins of the endosome sorting complexes required for transport (ESCRT) are upregulated, required for µLP, and recruited to LDs, vacuolar membranes, and sites of vacuolar membrane scission during µLP. We identify possible target proteins for LD-mediated ER proteostasis. Our live-cell imaging studies reveal that one potential target (Nup159) localizes to punctate structures that colocalizes with LDs 1) during movement from ER membranes to the cytosol, 2) during microautophagic uptake into vacuoles, and 3) within the vacuolar lumen. Finally, we find that mutations that inhibit LD biogenesis, homotypic vacuolar membrane fusion or ESCRT function inhibit stress-induced autophagy of Nup159 and other ER proteins. Thus, we have obtained the first direct evidence that LDs and µLP can mediate ER stress-induced ER proteostasis, and identified direct roles for ESCRT and vacuolar membrane fusion in that process.
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Affiliation(s)
- Enrique J Garcia
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Pin-Chao Liao
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Gary Tan
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Jason D Vevea
- HHMI and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin, USA
| | - Cierra N Sing
- Institute of Human Nutrition, Columbia University, New York, NY, USA
| | - Catherine A Tsang
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD, USA
| | - Istvan R Boldogh
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Liza A Pon
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
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55
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Triacylglycerols sequester monotopic membrane proteins to lipid droplets. Nat Commun 2020; 11:3944. [PMID: 32769983 PMCID: PMC7414839 DOI: 10.1038/s41467-020-17585-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 07/08/2020] [Indexed: 01/05/2023] Open
Abstract
Triacylglycerols (TG) are synthesized at the endoplasmic reticulum (ER) bilayer and packaged into organelles called lipid droplets (LDs). LDs are covered by a single phospholipid monolayer contiguous with the ER bilayer. This connection is used by several monotopic integral membrane proteins, with hydrophobic membrane association domains (HDs), to diffuse between the organelles. However, how proteins partition between ER and LDs is not understood. Here, we employed synthetic model systems and found that HD-containing proteins strongly prefer monolayers and returning to the bilayer is unfavorable. This preference for monolayers is due to a higher affinity of HDs for TG over membrane phospholipids. Protein distribution is regulated by PC/PE ratio via alterations in monolayer packing and HD-TG interaction. Thus, HD-containing proteins appear to non-specifically accumulate to the LD surface. In cells, protein editing mechanisms at the ER membrane would be necessary to prevent unspecific relocation of HD-containing proteins to LDs. Triacylglycerols (TG) are synthesized at the endoplasmic reticulum (ER) bilayer and packaged into monolayer lipid droplets (LDs), but how proteins partition between ER and LDs is poorly understood. Here authors use synthetic model systems and find that proteins containing hydrophobic membrane association domains strongly prefer monolayers and that returning to the bilayer is unfavorable.
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56
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Reinhard J, Mattes C, Väth K, Radanović T, Surma MA, Klose C, Ernst R. A Quantitative Analysis of Cellular Lipid Compositions During Acute Proteotoxic ER Stress Reveals Specificity in the Production of Asymmetric Lipids. Front Cell Dev Biol 2020; 8:756. [PMID: 32850859 PMCID: PMC7417482 DOI: 10.3389/fcell.2020.00756] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 07/20/2020] [Indexed: 12/12/2022] Open
Abstract
The unfolded protein response (UPR) is central to endoplasmic reticulum (ER) homeostasis by controlling its size and protein folding capacity. When activated by unfolded proteins in the ER-lumen or aberrant lipid compositions, the UPR adjusts the expression of hundreds of target genes to counteract ER stress. The proteotoxic drugs dithiothreitol (DTT) and tunicamycin (TM) are commonly used to induce misfolding of proteins in the ER and to study the UPR. However, their potential impact on the cellular lipid composition has never been systematically addressed. Here, we report the quantitative, cellular lipid composition of Saccharomyces cerevisiae during acute, proteotoxic stress in both rich and synthetic media. We show that DTT causes rapid remodeling of the lipidome when used in rich medium at growth-inhibitory concentrations, while TM has only a marginal impact on the lipidome under our conditions of cultivation. We formulate recommendations on how to study UPR activation by proteotoxic stress without interferences from a perturbed lipid metabolism. Furthermore, our data suggest an intricate connection between the cellular growth rate, the abundance of the ER, and the metabolism of fatty acids. We show that Saccharomyces cerevisiae can produce asymmetric lipids with two saturated fatty acyl chains differing substantially in length. These observations indicate that the pairing of saturated fatty acyl chains is tightly controlled and suggest an evolutionary conservation of asymmetric lipids and their biosynthetic machineries.
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Affiliation(s)
- John Reinhard
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - Carsten Mattes
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - Kristina Väth
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - Toni Radanović
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | | | | | - Robert Ernst
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
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57
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Leier HC, Weinstein JB, Kyle JE, Lee JY, Bramer LM, Stratton KG, Kempthorne D, Navratil AR, Tafesse EG, Hornemann T, Messer WB, Dennis EA, Metz TO, Barklis E, Tafesse FG. A global lipid map defines a network essential for Zika virus replication. Nat Commun 2020; 11:3652. [PMID: 32694525 PMCID: PMC7374707 DOI: 10.1038/s41467-020-17433-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
Zika virus (ZIKV), an arbovirus of global concern, remodels intracellular membranes to form replication sites. How ZIKV dysregulates lipid networks to allow this, and consequences for disease, is poorly understood. Here, we perform comprehensive lipidomics to create a lipid network map during ZIKV infection. We find that ZIKV significantly alters host lipid composition, with the most striking changes seen within subclasses of sphingolipids. Ectopic expression of ZIKV NS4B protein results in similar changes, demonstrating a role for NS4B in modulating sphingolipid pathways. Disruption of sphingolipid biosynthesis in various cell types, including human neural progenitor cells, blocks ZIKV infection. Additionally, the sphingolipid ceramide redistributes to ZIKV replication sites, and increasing ceramide levels by multiple pathways sensitizes cells to ZIKV infection. Thus, we identify a sphingolipid metabolic network with a critical role in ZIKV replication and show that ceramide flux is a key mediator of ZIKV infection.
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Affiliation(s)
- Hans C Leier
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University (OHSU), Portland, OR, 97239, USA
| | - Jules B Weinstein
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University (OHSU), Portland, OR, 97239, USA
| | - Jennifer E Kyle
- Biological Sciences Division, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Joon-Yong Lee
- Biological Sciences Division, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Lisa M Bramer
- Computing and Analytics Division, National Security Directorate, PNNL, Richland, WA, 99352, USA
| | - Kelly G Stratton
- Computing and Analytics Division, National Security Directorate, PNNL, Richland, WA, 99352, USA
| | - Douglas Kempthorne
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University (OHSU), Portland, OR, 97239, USA
- Center for Diversity and Inclusion, OHSU, Portland, OR, 97239, USA
| | - Aaron R Navratil
- Departments of Chemistry & Biochemistry and Pharmacology, University of California San Diego School of Medicine, La Jolla, CA, 92093, USA
| | - Endale G Tafesse
- Department of Plant Sciences, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK, S7N 5A8, Canada
| | - Thorsten Hornemann
- University Zurich and University Hospital Zurich, University of Zurich, Zurich, 8091, Switzerland
| | - William B Messer
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University (OHSU), Portland, OR, 97239, USA
- Department of Medicine, Division of Infectious Diseases, OHSU, Portland, Oregon, 97239, USA
| | - Edward A Dennis
- Departments of Chemistry & Biochemistry and Pharmacology, University of California San Diego School of Medicine, La Jolla, CA, 92093, USA
| | - Thomas O Metz
- Biological Sciences Division, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Eric Barklis
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University (OHSU), Portland, OR, 97239, USA
| | - Fikadu G Tafesse
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University (OHSU), Portland, OR, 97239, USA.
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58
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Ho N, Yap WS, Xu J, Wu H, Koh JH, Goh WWB, George B, Chong SC, Taubert S, Thibault G. Stress sensor Ire1 deploys a divergent transcriptional program in response to lipid bilayer stress. J Cell Biol 2020; 219:e201909165. [PMID: 32349127 PMCID: PMC7337508 DOI: 10.1083/jcb.201909165] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 02/26/2020] [Accepted: 04/07/2020] [Indexed: 12/11/2022] Open
Abstract
Membrane integrity at the endoplasmic reticulum (ER) is tightly regulated, and its disturbance is implicated in metabolic diseases. Using an engineered sensor that activates the unfolded protein response (UPR) exclusively when normal ER membrane lipid composition is compromised, we identified pathways beyond lipid metabolism that are necessary to maintain ER integrity in yeast and in C. elegans. To systematically validate yeast mutants that disrupt ER membrane homeostasis, we identified a lipid bilayer stress (LBS) sensor in the UPR transducer protein Ire1, located at the interface of the amphipathic and transmembrane helices. Furthermore, transcriptome and chromatin immunoprecipitation analyses pinpoint the UPR as a broad-spectrum compensatory response wherein LBS and proteotoxic stress deploy divergent transcriptional UPR programs. Together, these findings reveal the UPR program as the sum of two independent stress responses, an insight that could be exploited for future therapeutic intervention.
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Affiliation(s)
- Nurulain Ho
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Wei Sheng Yap
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Jiaming Xu
- Centre for Molecular Medicine and Therapeutics, British Columbia Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Haoxi Wu
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Jhee Hong Koh
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Wilson Wen Bin Goh
- Bio-Data Science and Education Research Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Bhawana George
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Shu Chen Chong
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Stefan Taubert
- Centre for Molecular Medicine and Therapeutics, British Columbia Children’s Hospital Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Guillaume Thibault
- Lipid Regulation and Cell Stress Group, School of Biological Sciences, Nanyang Technological University, Singapore
- Institute of Molecular and Cell Biology, A*STAR, Singapore
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59
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Rajakumar S, Vijayakumar R, Abhishek A, Selvam GS, Nachiappan V. Loss of ERAD bridging factor UBX2 modulates lipid metabolism and leads to ER stress-associated apoptosis during cadmium toxicity in Saccharomyces cerevisiae. Curr Genet 2020; 66:1003-1017. [DOI: 10.1007/s00294-020-01090-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 06/08/2020] [Accepted: 06/22/2020] [Indexed: 12/17/2022]
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60
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Tan JX, Finkel T. Mitochondria as intracellular signaling platforms in health and disease. J Cell Biol 2020; 219:e202002179. [PMID: 32320464 PMCID: PMC7199861 DOI: 10.1083/jcb.202002179] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/02/2020] [Accepted: 04/03/2020] [Indexed: 12/15/2022] Open
Abstract
Mitochondria, long viewed solely in the context of bioenergetics, are increasingly emerging as critical hubs for intracellular signaling. Due to their bacterial origin, mitochondria possess their own genome and carry unique lipid components that endow these organelles with specialized properties to help orchestrate multiple signaling cascades. Mitochondrial signaling modulates diverse pathways ranging from metabolism to redox homeostasis to cell fate determination. Here, we review recent progress in our understanding of how mitochondria serve as intracellular signaling platforms with a particular emphasis on lipid-mediated signaling, innate immune activation, and retrograde signaling. We further discuss how these signaling properties might potentially be exploited to develop new therapeutic strategies for a range of age-related conditions.
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Affiliation(s)
- Jay X. Tan
- Aging Institute, University of Pittsburgh School of Medicine/University of Pittsburgh Medical Center, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Toren Finkel
- Aging Institute, University of Pittsburgh School of Medicine/University of Pittsburgh Medical Center, Pittsburgh, PA
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
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61
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Rajakumar S, Abhishek A, Selvam GS, Nachiappan V. Effect of cadmium on essential metals and their impact on lipid metabolism in Saccharomyces cerevisiae. Cell Stress Chaperones 2020; 25:19-33. [PMID: 31823289 PMCID: PMC6985397 DOI: 10.1007/s12192-019-01058-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 11/14/2019] [Accepted: 11/28/2019] [Indexed: 01/09/2023] Open
Abstract
Cadmium (Cd) is a toxic heavy metal that induces irregularity in numerous lipid metabolic pathways. Saccharomyces cerevisiae, a model to study lipid metabolism, has been used to establish the molecular basis of cellular responses to Cd toxicity in relation to essential minerals and lipid homeostasis. Multiple pathways sense these environmental stresses and trigger the mineral imbalances specifically calcium (Ca) and zinc (Zn). This review is aimed to elucidate the role of Cd toxicity in yeast, in three different perspectives: (1) elucidate stress response and its adaptation to Cd, (2) understand the physiological role of a macromolecule such as lipids, and (3) study the stress rescue mechanism. Here, we explored the impact of Cd interference on the essential minerals such as Zn and Ca and their influence on endoplasmic reticulum stress and lipid metabolism. Cd toxicity contributes to lipid droplet synthesis by activating OLE1 that is essential to alleviate lipotoxicity. In this review, we expanded our current findings about the effect of Cd on lipid metabolism of budding yeast.
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Affiliation(s)
- Selvaraj Rajakumar
- Eukaryotic Biology Lab, Department of Biochemistry, School of Biological Sciences, Madurai Kamaraj University, Madurai, Tamil Nadu, 625021, India.
- Biomembrane Lab, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India.
- Department of Pediatrics, Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta, T6G 2S2, Canada.
| | - Albert Abhishek
- Eukaryotic Biology Lab, Department of Biochemistry, School of Biological Sciences, Madurai Kamaraj University, Madurai, Tamil Nadu, 625021, India
| | - Govindan Sadasivam Selvam
- Eukaryotic Biology Lab, Department of Biochemistry, School of Biological Sciences, Madurai Kamaraj University, Madurai, Tamil Nadu, 625021, India
| | - Vasanthi Nachiappan
- Biomembrane Lab, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India
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62
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Micoogullari Y, Basu SS, Ang J, Weisshaar N, Schmitt ND, Abdelmoula WM, Lopez B, Agar JN, Agar N, Hanna J. Dysregulation of very-long-chain fatty acid metabolism causes membrane saturation and induction of the unfolded protein response. Mol Biol Cell 2019; 31:7-17. [PMID: 31746669 PMCID: PMC6938273 DOI: 10.1091/mbc.e19-07-0392] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The unfolded protein response (UPR) senses defects in the endoplasmic reticulum (ER) and orchestrates a complex program of adaptive cellular remodeling. Increasing evidence suggests an important relationship between lipid homeostasis and the UPR. Defects in the ER membrane induce the UPR, and the UPR in turn controls the expression of some lipid metabolic genes. Among lipid species, the very-long-chain fatty acids (VLCFAs) are relatively rare and poorly understood. Here, we show that loss of the VLCFA-coenzyme A synthetase Fat1, which is essential for VLCFA utilization, results in ER stress with compensatory UPR induction. Comprehensive lipidomic analyses revealed a dramatic increase in membrane saturation in the fat1Δ mutant, likely accounting for UPR induction. In principle, this increased membrane saturation could reflect adaptive membrane remodeling or an adverse effect of VLCFA dysfunction. We provide evidence supporting the latter, as the fat1Δ mutant showed defects in the function of Ole1, the sole fatty acyl desaturase in yeast. These results indicate that VLCFAs play essential roles in protein quality control and membrane homeostasis and suggest an unexpected requirement for VLCFAs in Ole1 function.
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Affiliation(s)
| | - Sankha S Basu
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | | | | | | | - Walid M Abdelmoula
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Begona Lopez
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Jeffrey N Agar
- Department of Chemistry and Chemical Biology and.,Department of Pharmacological Sciences, Northeastern University, Boston, MA 02111
| | - Nathalie Agar
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
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63
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Xie SZ, Garcia-Prat L, Voisin V, Ferrari R, Gan OI, Wagenblast E, Kaufmann KB, Zeng AGX, Takayanagi SI, Patel I, Lee EK, Jargstorf J, Holmes G, Romm G, Pan K, Shoong M, Vedi A, Luberto C, Minden MD, Bader GD, Laurenti E, Dick JE. Sphingolipid Modulation Activates Proteostasis Programs to Govern Human Hematopoietic Stem Cell Self-Renewal. Cell Stem Cell 2019; 25:639-653.e7. [PMID: 31631013 PMCID: PMC6838675 DOI: 10.1016/j.stem.2019.09.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 07/09/2019] [Accepted: 09/23/2019] [Indexed: 12/30/2022]
Abstract
Cellular stress responses serve as crucial decision points balancing persistence or culling of hematopoietic stem cells (HSCs) for lifelong blood production. Although strong stressors cull HSCs, the linkage between stress programs and self-renewal properties that underlie human HSC maintenance remains unknown, particularly at quiescence exit when HSCs must also dynamically shift metabolic state. Here, we demonstrate distinct wiring of the sphingolipidome across the human hematopoietic hierarchy and find that genetic or pharmacologic modulation of the sphingolipid enzyme DEGS1 regulates lineage differentiation. Inhibition of DEGS1 in hematopoietic stem and progenitor cells during the transition from quiescence to cellular activation with N-(4-hydroxyphenyl) retinamide activates coordinated stress pathways that coalesce on endoplasmic reticulum stress and autophagy programs to maintain immunophenotypic and functional HSCs. Thus, our work identifies a linkage between sphingolipid metabolism, proteostatic quality control systems, and HSC self-renewal and provides therapeutic targets for improving HSC-based cellular therapeutics.
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Affiliation(s)
- Stephanie Z Xie
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada.
| | - Laura Garcia-Prat
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Veronique Voisin
- The Donnelly Centre, University of Toronto, Toronto, ON M5S3E1, Canada
| | - Robin Ferrari
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Olga I Gan
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Elvin Wagenblast
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Kerstin B Kaufmann
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Andy G X Zeng
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S1A8, Canada
| | - Shin-Ichiro Takayanagi
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada; R&D Division, Kyowa Kirin Co., Ltd., Tokyo 194-8533, Japan
| | - Ishita Patel
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Esther K Lee
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Joseph Jargstorf
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Gareth Holmes
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Guy Romm
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Kristele Pan
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Michelle Shoong
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada
| | - Aditi Vedi
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, Department of Haematology, University of Cambridge, Cambridge, UK
| | - Chiara Luberto
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, NY 11794, USA
| | - Mark D Minden
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada; Division of Medical Oncology and Hematology, Department of Medicine, University Health Network, Toronto, ON, Canada; Department of Medicine, University of Toronto, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Gary D Bader
- The Donnelly Centre, University of Toronto, Toronto, ON M5S3E1, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S1A8, Canada
| | - Elisa Laurenti
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, Department of Haematology, University of Cambridge, Cambridge, UK
| | - John E Dick
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G0A3, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S1A8, Canada.
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64
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Song MJ, Malhi H. The unfolded protein response and hepatic lipid metabolism in non alcoholic fatty liver disease. Pharmacol Ther 2019; 203:107401. [PMID: 31419516 PMCID: PMC6848795 DOI: 10.1016/j.pharmthera.2019.107401] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 08/08/2019] [Indexed: 12/19/2022]
Abstract
Nonalcoholic fatty liver disease is a major public health burden. Although many features of nonalcoholic fatty liver disease pathogenesis are known, the specific mechanisms and susceptibilities that determine an individual's risk of developing nonalcoholic steatohepatitis versus isolated steatosis are not well delineated. The predominant and defining histologic and imaging characteristic of nonalcoholic fatty liver disease is the accumulation of lipids. Dysregulation of lipid homeostasis in hepatocytes leads to transient generation or accumulation of toxic lipids that result in endoplasmic reticulum (ER) stress with inflammation, hepatocellular damage, and apoptosis. ER stress activates the unfolded protein response (UPR) which is classically viewed as an adaptive pathway to maintain protein folding homeostasis. Recent studies have uncovered the contribution of the UPR sensors in the regulation of hepatic steatosis and in the cellular response to lipotoxic stress. Interestingly, the UPR sensors can be directly activated by toxic lipids, independently of the accumulation of misfolded proteins, termed lipotoxic and proteotoxic stress, respectively. The dual function of the UPR sensors in protein and lipid homeostasis suggests that these two types of stress are interconnected likely due to the central role of the ER in protein folding and trafficking and lipid biosynthesis and trafficking, such that perturbations in either impact the function of the ER and activate the UPR sensors in an effort to restore homeostasis. The precise molecular similarities and differences between proteotoxic and lipotoxic ER stress are beginning to be understood. Herein, we provide an overview of the mechanisms involved in the activation and cross-talk between the UPR sensors, hepatic lipid metabolism, and lipotoxic stress, and discuss the possible therapeutic potential of targeting the UPR in nonalcoholic fatty liver disease.
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Affiliation(s)
- Myeong Jun Song
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, United States of America; Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Harmeet Malhi
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, United States of America.
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65
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Medkour Y, Mohammad K, Arlia-Ciommo A, Svistkova V, Dakik P, Mitrofanova D, Rodriguez MEL, Junio JAB, Taifour T, Escudero P, Goltsios FF, Soodbakhsh S, Maalaoui H, Simard É, Titorenko VI. Mechanisms by which PE21, an extract from the white willow Salix alba, delays chronological aging in budding yeast. Oncotarget 2019; 10:5780-5816. [PMID: 31645900 PMCID: PMC6791382 DOI: 10.18632/oncotarget.27209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 08/27/2019] [Indexed: 01/05/2023] Open
Abstract
We have recently found that PE21, an extract from the white willow Salix alba, slows chronological aging and prolongs longevity of the yeast Saccharomyces cerevisiae more efficiently than any of the previously known pharmacological interventions. Here, we investigated mechanisms through which PE21 delays yeast chronological aging and extends yeast longevity. We show that PE21 causes a remodeling of lipid metabolism in chronologically aging yeast, thereby instigating changes in the concentrations of several lipid classes. We demonstrate that such changes in the cellular lipidome initiate three mechanisms of aging delay and longevity extension. The first mechanism through which PE21 slows aging and prolongs longevity consists in its ability to decrease the intracellular concentration of free fatty acids. This postpones an age-related onset of liponecrotic cell death promoted by excessive concentrations of free fatty acids. The second mechanism of aging delay and longevity extension by PE21 consists in its ability to decrease the concentrations of triacylglycerols and to increase the concentrations of glycerophospholipids within the endoplasmic reticulum membrane. This activates the unfolded protein response system in the endoplasmic reticulum, which then decelerates an age-related decline in protein and lipid homeostasis and slows down an aging-associated deterioration of cell resistance to stress. The third mechanisms underlying aging delay and longevity extension by PE21 consists in its ability to change lipid concentrations in the mitochondrial membranes. This alters certain catabolic and anabolic processes in mitochondria, thus amending the pattern of aging-associated changes in several key aspects of mitochondrial functionality.
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Affiliation(s)
- Younes Medkour
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Karamat Mohammad
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | | | - Veronika Svistkova
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Pamela Dakik
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Darya Mitrofanova
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | | | | | - Tarek Taifour
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Paola Escudero
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Fani-Fay Goltsios
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Sahar Soodbakhsh
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Hana Maalaoui
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Éric Simard
- Idunn Technologies Inc., Rosemere, Quebec J7A 4A5, Canada
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66
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de Mendoza D, Pilon M. Control of membrane lipid homeostasis by lipid-bilayer associated sensors: A mechanism conserved from bacteria to humans. Prog Lipid Res 2019; 76:100996. [DOI: 10.1016/j.plipres.2019.100996] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 06/25/2019] [Accepted: 06/28/2019] [Indexed: 12/31/2022]
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67
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Lin YC, Kanehara K, Nakamura Y. Arabidopsis CHOLINE/ETHANOLAMINE KINASE 1 (CEK1) is a primary choline kinase localized at the endoplasmic reticulum (ER) and involved in ER stress tolerance. THE NEW PHYTOLOGIST 2019; 223:1904-1917. [PMID: 31087404 DOI: 10.1111/nph.15915] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 05/05/2019] [Indexed: 05/25/2023]
Abstract
Choline kinase catalyzes the initial reaction step of choline metabolism that produces phosphocholine, a prerequisite for the biosynthesis of a primary phospholipid phosphatidylcholine. However, the primary choline kinase and its role in plant growth remained elusive in seed plants. Here, we showed that Arabidopsis CHOLINE/ETHANOLAMINE KINASE 1 (CEK1) encodes functional CEK that prefers choline than ethanolamine as a substrate in vitro and affects contents of choline and phosphocholine but not phosphatidylcholine in vivo. CEK1 is localized at endoplasmic reticulum (ER); upon tunicamycin-induced ER stress, a null mutant of CEK1 showed hypersensitive phenotype in seedlings, albeit with no enhanced choline kinase activity. Our results demonstrate that CEK1 is a primary ER-localized choline kinase in vivo that is required for ER stress tolerance possibly through the modulation of choline metabolites.
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Affiliation(s)
- Ying-Chen Lin
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 11529, Taiwan
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Kazue Kanehara
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 11529, Taiwan
- Biotechnology Center, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Yuki Nakamura
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 11529, Taiwan
- Biotechnology Center, National Chung Hsing University, Taichung, 40227, Taiwan
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68
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iPla2β Deficiency Suppresses Hepatic ER UPR, Fxr, and Phospholipids in Mice Fed with MCD Diet, Resulting in Exacerbated Hepatic Bile Acids and Biliary Cell Proliferation. Cells 2019; 8:cells8080879. [PMID: 31409057 PMCID: PMC6721660 DOI: 10.3390/cells8080879] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 07/26/2019] [Accepted: 08/08/2019] [Indexed: 12/30/2022] Open
Abstract
Background: Group VIA calcium-independent phospholipase A2 (iPla2β) regulates homeostasis and remodeling of phospholipids (PL). We previously showed that iPla2β-/- mice fed with a methionine-choline-deficient diet (MCD) exhibited exaggerated liver fibrosis. As iPla2β is located in the endoplasmic reticulum (ER), we investigated the mechanisms for this by focusing on hepatic ER unfolded protein response (UPR), ER PL, and enterohepatic bile acids (BA). Methods: Female WT (wild-type) and iPla2β-/- mice were fed with chow or MCD for 5 weeks. PL and BA profiles were measured by liquid chromatography-mass spectrometry. Gene expression analyses were performed. Results: MCD feeding of WT mice caused a decrease of ER PL subclasses, which were further decreased by iPla2β deficiency. This deficiency alone or combined with MCD downregulated the expression of liver ER UPR proteins and farnesoid X-activated receptor. The downregulation under MCD was concomitant with an elevation of BA in the liver and peripheral blood and an increase of biliary epithelial cell proliferation measured by cytokeratin 19. Conclusion: iPla2β deficiency combined with MCD severely disturbed ER PL composition and caused inactivation of UPR, leading to downregulated Fxr, exacerbated BA, and ductular proliferation. Our study provides insights into iPla2β inactivation for injury susceptibility under normal conditions and liver fibrosis and cholangiopathies during MCD feeding.
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69
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Goder V, Alanis-Dominguez E, Bustamante-Sequeiros M. Lipids and their (un)known effects on ER-associated protein degradation (ERAD). Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158488. [PMID: 31233887 DOI: 10.1016/j.bbalip.2019.06.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/15/2019] [Accepted: 06/18/2019] [Indexed: 02/09/2023]
Abstract
Endoplasmic reticulum (ER)-associated protein degradation (ERAD) is a conserved cellular process that apart from protein quality control and maintenance of ER membrane identity has pivotal functions in regulating the lipid composition of the ER membrane. A general trigger for ERAD activation is the exposure of normally buried protein domains due to protein misfolding, absence of binding partners or conformational changes. Several feedback loops for ER lipid homeostasis exploit the induction of conformational changes in key enzymes of lipid biosynthesis or in ER membrane-embedded transcription factors upon shortage or abundance of specific lipids, leading to enzyme degradation or mobilization of transcription factors. Similarly, an insufficient amount of lipids triggers ERAD of apolipoproteins during lipoprotein formation. Lipids might even have a role in ER protein quality control: when proteins destined for ER export are covalently modified with lipids their ER residence time and their susceptibility to ERAD is reduced. Here we summarize and compare the various interconnections of lipids with ER membrane proteins and ERAD. This article is part of a Special Issue entitled Endoplasmic reticulum platforms for lipid dynamics edited by Shamshad Cockcroft and Christopher Stefan.
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Affiliation(s)
- Veit Goder
- Department of Genetics, University of Seville, 6, Ave Reina Mercedes, 41012 Seville, Spain.
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70
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Thiam AR, Dugail I. Lipid droplet-membrane contact sites - from protein binding to function. J Cell Sci 2019; 132:132/12/jcs230169. [PMID: 31209063 DOI: 10.1242/jcs.230169] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In the general context of an increasing prevalence of obesity-associated diseases, which follows changing paradigms in food consumption and worldwide use of industry-transformed foodstuffs, much attention has been given to the consequences of excessive fattening on health. Highly related to this clinical problem, studies at the cellular and molecular level are focused on the fundamental mechanism of lipid handling in dedicated lipid droplet (LD) organelles. This Review briefly summarizes how views on LD functions have evolved from those of a specialized intracellular compartment dedicated to lipid storage to exerting a more generalized role in the stress response. We focus on the current understanding of how proteins bind to LDs and determine their function, and on the new paradigms that have emerged from the discoveries of the multiple contact sites formed by LDs. We argue that elucidating the important roles of LD tethering to other cellular organelles allows for a better understanding of LD diversity and dynamics.
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Affiliation(s)
- Abdou Rachid Thiam
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, 75005 Paris, France
| | - Isabelle Dugail
- U1269 INSERM/Sorbonne Université, Nutriomics, Faculté de Médecine Pitié-Salpêtrière, 75013 Paris, France
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71
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Membrane phospholipid alteration causes chronic ER stress through early degradation of homeostatic ER-resident proteins. Sci Rep 2019; 9:8637. [PMID: 31201345 PMCID: PMC6572771 DOI: 10.1038/s41598-019-45020-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/29/2019] [Indexed: 12/31/2022] Open
Abstract
Phospholipid homeostasis in biological membranes is essential to maintain functions of organelles such as the endoplasmic reticulum. Phospholipid perturbation has been associated to cellular stress responses. However, in most cases, the implication of membrane lipid changes to homeostatic cellular response has not been clearly defined. Previously, we reported that Saccharomyces cerevisiae adapts to lipid bilayer stress by upregulating several protein quality control pathways such as the endoplasmic reticulum-associated degradation (ERAD) pathway and the unfolded protein response (UPR). Surprisingly, we observed certain ER-resident transmembrane proteins, which form part of the UPR programme, to be destabilised under lipid bilayer stress. Among these, the protein translocon subunit Sbh1 was prematurely degraded by membrane stiffening at the ER. Moreover, our findings suggest that the Doa10 complex recognises free Sbh1 that becomes increasingly accessible during lipid bilayer stress, perhaps due to the change in ER membrane properties. Premature removal of key ER-resident transmembrane proteins might be an underlying cause of chronic ER stress as a result of lipid bilayer stress.
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72
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Chadwick SR, Lajoie P. Endoplasmic Reticulum Stress Coping Mechanisms and Lifespan Regulation in Health and Diseases. Front Cell Dev Biol 2019; 7:84. [PMID: 31231647 PMCID: PMC6558375 DOI: 10.3389/fcell.2019.00084] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 05/03/2019] [Indexed: 12/30/2022] Open
Abstract
Multiple factors lead to proteostatic perturbations, often resulting in the aberrant accumulation of toxic misfolded proteins. Cells, from yeast to humans, can respond to sudden accumulation of secretory proteins within the endoplasmic reticulum (ER) through pathways such as the Unfolded Protein Response (UPR). The ability of cells to adapt the ER folding environment to the misfolded protein burden ultimately dictates cell fate. The aging process is a particularly important modifier of the proteostasis network; as cells age, both their ability to maintain this balance in protein folding/degradation and their ability to respond to insults in these pathways can break down, a common element of age-related diseases (including neurodegenerative diseases). ER stress coping mechanisms are central to lifespan regulation under both normal and disease states. In this review, we give a brief overview of the role of ER stress response pathways in age-dependent neurodegeneration.
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Affiliation(s)
- Sarah R Chadwick
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON, Canada
| | - Patrick Lajoie
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON, Canada
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73
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Abstract
Endoplasmic reticulum (ER) stress is a major contributor to liver disease and hepatic fibrosis, but the role it plays varies depending on the cause and progression of the disease. Furthermore, ER stress plays a distinct role in hepatocytes versus hepatic stellate cells (HSCs), which adds to the complexity of understanding ER stress and its downstream signaling through the unfolded protein response (UPR) in liver disease. Here, the authors focus on the current literature of ER stress in nonalcoholic and alcoholic fatty liver diseases, how ER stress impacts hepatocyte injury, and the role of ER stress in HSC activation and hepatic fibrosis. This review provides insight into the complex signaling and regulation of the UPR, parallels and distinctions between different liver diseases, and how ER stress may be targeted as an antisteatotic or antifibrotic therapy to limit the progression of liver disease.
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Affiliation(s)
- Jessica L. Maiers
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota
| | - Harmeet Malhi
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota
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74
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Engineering microbial membranes to increase stress tolerance of industrial strains. Metab Eng 2019; 53:24-34. [DOI: 10.1016/j.ymben.2018.12.010] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/29/2018] [Accepted: 12/29/2018] [Indexed: 12/29/2022]
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75
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Guerra-Moreno A, Ang J, Welsch H, Jochem M, Hanna J. Regulation of the unfolded protein response in yeast by oxidative stress. FEBS Lett 2019; 593:1080-1088. [PMID: 31002390 DOI: 10.1002/1873-3468.13389] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 04/09/2019] [Accepted: 04/11/2019] [Indexed: 12/11/2022]
Abstract
In the unfolded protein response (UPR), Ire1 activates Hac1 to coordinate the transcription of hundreds of genes to mitigate ER stress. Recent work in Caenorhabditis elegans suggests that oxidative stress inhibits this canonical Ire1 signalling pathway, activating instead an antioxidant stress response. We sought to determine whether this novel mode of UPR function also existed in yeast, where Ire1 has been best characterized. We show that the yeast UPR is also subject to inhibition by oxidative stress. Inhibition is mediated by a single evolutionarily conserved cysteine, and affects both luminal and membrane pathways of Ire1 activation. In yeast, Ire1 appears dispensable for resistance to oxidative stress and, therefore, the physiological significance of this pathway remains to be demonstrated.
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Affiliation(s)
- Angel Guerra-Moreno
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Jessie Ang
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Hendrik Welsch
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Marco Jochem
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - John Hanna
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
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76
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Fun XH, Thibault G. Lipid bilayer stress and proteotoxic stress-induced unfolded protein response deploy divergent transcriptional and non-transcriptional programmes. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158449. [PMID: 31028913 DOI: 10.1016/j.bbalip.2019.04.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/14/2019] [Accepted: 04/22/2019] [Indexed: 12/13/2022]
Abstract
The unfolded protein response (UPR) is activated by endoplasmic reticulum (ER) stress and is designed to restore cellular homeostasis through multiple intracellular signalling pathways. In mammals, the UPR programme regulates the expression of hundreds of genes in response to signalling from ATF6, IRE1, and PERK. These three highly conserved stress sensors are activated by the accumulation of unfolded proteins within the ER. Alternatively, IRE1 and PERK sense generalised lipid bilayer stress (LBS) at the ER while ATF6 is activated by an increase of specific sphingolipids. As a result, the UPR supports cellular robustness as a broad-spectrum compensatory pathway that is achieved by deploying a tailored transcriptional programme adapted to the source of ER stress. This review summarises the current understanding of the three ER stress transducers in sensing proteotoxic stress and LBS. The plasticity of the UPR programme in the context of different sources of ER stress will also be discussed.
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Affiliation(s)
- Xiu Hui Fun
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Guillaume Thibault
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.
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77
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Covino R, Hummer G, Ernst R. Integrated Functions of Membrane Property Sensors and a Hidden Side of the Unfolded Protein Response. Mol Cell 2019; 71:458-467. [PMID: 30075144 DOI: 10.1016/j.molcel.2018.07.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/09/2018] [Accepted: 07/17/2018] [Indexed: 12/26/2022]
Abstract
Eukaryotic cells face the challenge of maintaining the complex composition of several coexisting organelles. The molecular mechanisms underlying the homeostasis of subcellular membranes and their adaptation during stress are only now starting to emerge. Here, we discuss three membrane property sensors of the endoplasmic reticulum (ER), namely OPI1, MGA2, and IRE1, each controlling a large cellular program impacting the lipid metabolic network. OPI1 coordinates the production of membrane and storage lipids, MGA2 regulates the production of unsaturated fatty acids required for membrane biogenesis, and IRE1 controls the unfolded protein response (UPR) to adjust ER size, protein folding, and the secretory capacity of the cell. Although these proteins use remarkably distinct sensing mechanisms, they are functionally connected via the ER membrane and cooperate to maintain membrane homeostasis. As a rationalization of the recently described mechanism of UPR activation by lipid bilayer stress, we propose that IRE1 can sense the protein-to-lipid ratio in the ER membrane to ensure a balanced production of membrane proteins and lipids.
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Affiliation(s)
- Roberto Covino
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany; Institute of Biophysics, Goethe University, 60438 Frankfurt am Main, Germany
| | - Robert Ernst
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Kirrberger Str. 100, Gebäude 61.4, 66421 Homburg, Germany.
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78
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Koh JH, Wang L, Beaudoin-Chabot C, Thibault G. Lipid bilayer stress-activated IRE-1 modulates autophagy during endoplasmic reticulum stress. J Cell Sci 2018; 131:jcs.217992. [PMID: 30333136 DOI: 10.1242/jcs.217992] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 10/01/2018] [Indexed: 12/14/2022] Open
Abstract
Metabolic disorders, such as non-alcoholic fatty liver disease (NAFLD), are emerging as epidemics that affect the global population. One facet of these disorders is attributed to the disturbance of membrane lipid composition. Perturbation of endoplasmic reticulum (ER) homeostasis through alteration in membrane phospholipids activates the unfolded protein response (UPR) and causes dramatic transcriptional and translational changes in the cell. To restore cellular homeostasis, the three highly conserved UPR transducers ATF6, IRE1 (also known as ERN1 in mammals) and PERK (also known as EIF2AK3 in mammals) mediate adaptive responses upon ER stress. The homeostatic UPR cascade is well characterised under conditions of proteotoxic stress, but much less so under lipid bilayer stress-induced UPR. Here, we show that disrupted phosphatidylcholine (PC) synthesis in Caenorhabditis elegans causes lipid bilayer stress, lipid droplet accumulation and ER stress induction. Transcriptional profiling of PC-deficient worms revealed a unique subset of genes regulated in a UPR-dependent manner that is independent from proteotoxic stress. Among these, we show that autophagy is modulated through the conserved IRE-1-XBP-1 axis, strongly suggesting of the importance of autophagy in maintaining cellular homeostasis during the lipid bilayer stress-induced UPR.
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Affiliation(s)
- Jhee Hong Koh
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - Lei Wang
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | | | - Guillaume Thibault
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
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79
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Dropping in on lipid droplets: insights into cellular stress and cancer. Biosci Rep 2018; 38:BSR20180764. [PMID: 30111611 PMCID: PMC6146295 DOI: 10.1042/bsr20180764] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 08/01/2018] [Accepted: 08/06/2018] [Indexed: 02/07/2023] Open
Abstract
Lipid droplets (LD) have increasingly become a major topic of research in recent years following its establishment as a highly dynamic organelle. Contrary to the initial view of LDs being passive cytoplasmic structures for lipid storage, studies have provided support on how they act in concert with different organelles to exert functions in various cellular processes. Although lipid dysregulation resulting from aberrant LD homeostasis has been well characterised, how this translates and contributes to cancer progression is poorly understood. This review summarises the different paradigms on how LDs function in the regulation of cellular stress as a contributing factor to cancer progression. Mechanisms employed by a broad range of cancer cell types in differentially utilising LDs for tumourigenesis will also be highlighted. Finally, we discuss the potential of targeting LDs in the context of cancer therapeutics.
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80
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Tam AB, Roberts LS, Chandra V, Rivera IG, Nomura DK, Forbes DJ, Niwa M. The UPR Activator ATF6 Responds to Proteotoxic and Lipotoxic Stress by Distinct Mechanisms. Dev Cell 2018; 46:327-343.e7. [PMID: 30086303 DOI: 10.1016/j.devcel.2018.04.023] [Citation(s) in RCA: 127] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Revised: 04/13/2018] [Accepted: 04/24/2018] [Indexed: 02/06/2023]
Abstract
The unfolded protein response (UPR) is induced by proteotoxic stress of the endoplasmic reticulum (ER). Here we report that ATF6, a major mammalian UPR sensor, is also activated by specific sphingolipids, dihydrosphingosine (DHS) and dihydroceramide (DHC). Single mutations in a previously undefined transmembrane domain motif that we identify in ATF6 incapacitate DHS/DHC activation while still allowing proteotoxic stress activation via the luminal domain. ATF6 thus possesses two activation mechanisms: DHS/DHC activation and proteotoxic stress activation. Reporters constructed to monitor each mechanism show that phenobarbital-induced ER membrane expansion depends on transmembrane domain-induced ATF6. DHS/DHC addition preferentially induces transcription of ATF6 target lipid biosynthetic and metabolic genes over target ER chaperone genes. Importantly, ATF6 containing a luminal achromatopsia eye disease mutation, unresponsive to proteotoxic stress, can be activated by fenretinide, a drug that upregulates DHC, suggesting a potential therapy for this and other ATF6-related diseases including heart disease and stroke.
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Affiliation(s)
- Arvin B Tam
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA
| | - Lindsay S Roberts
- Department of Chemistry, Molecular and Cell Biology, and Nutritional Sciences and Toxicology, University of California, Berkeley, 127 Morgan Hall, Berkeley, CA 94720, USA
| | - Vivek Chandra
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA
| | - Io Guane Rivera
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA
| | - Daniel K Nomura
- Department of Chemistry, Molecular and Cell Biology, and Nutritional Sciences and Toxicology, University of California, Berkeley, 127 Morgan Hall, Berkeley, CA 94720, USA
| | - Douglass J Forbes
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, 2124A Pacific Hall, 9500 Gilman Drive, La Jolla, CA 92093-0347, USA
| | - Maho Niwa
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA.
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81
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Haider A, Wei YC, Lim K, Barbosa AD, Liu CH, Weber U, Mlodzik M, Oras K, Collier S, Hussain MM, Dong L, Patel S, Alvarez-Guaita A, Saudek V, Jenkins BJ, Koulman A, Dymond MK, Hardie RC, Siniossoglou S, Savage DB. PCYT1A Regulates Phosphatidylcholine Homeostasis from the Inner Nuclear Membrane in Response to Membrane Stored Curvature Elastic Stress. Dev Cell 2018; 45:481-495.e8. [PMID: 29754800 PMCID: PMC5971203 DOI: 10.1016/j.devcel.2018.04.012] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 02/27/2018] [Accepted: 04/11/2018] [Indexed: 12/19/2022]
Abstract
Cell and organelle membranes consist of a complex mixture of phospholipids (PLs) that determine their size, shape, and function. Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic membranes, yet how cells sense and regulate its levels in vivo remains unclear. Here we show that PCYT1A, the rate-limiting enzyme of PC synthesis, is intranuclear and re-locates to the nuclear membrane in response to the need for membrane PL synthesis in yeast, fly, and mammalian cells. By aligning imaging with lipidomic analysis and data-driven modeling, we demonstrate that yeast PCYT1A membrane association correlates with membrane stored curvature elastic stress estimates. Furthermore, this process occurs inside the nucleus, although nuclear localization signal mutants can compensate for the loss of endogenous PCYT1A in yeast and in fly photoreceptors. These data suggest an ancient mechanism by which nucleoplasmic PCYT1A senses surface PL packing defects on the inner nuclear membrane to control PC homeostasis.
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Affiliation(s)
- Afreen Haider
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Yu-Chen Wei
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Koini Lim
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Antonio D Barbosa
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Che-Hsiung Liu
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Ursula Weber
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York City, NY 10029, USA
| | - Marek Mlodzik
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York City, NY 10029, USA
| | - Kadri Oras
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Simon Collier
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - M Mahmood Hussain
- Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Liang Dong
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Satish Patel
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Anna Alvarez-Guaita
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Vladimir Saudek
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Benjamin J Jenkins
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Albert Koulman
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Marcus K Dymond
- Division of Chemistry, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
| | - Roger C Hardie
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Symeon Siniossoglou
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK.
| | - David B Savage
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
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82
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Ernst R, Ballweg S, Levental I. Cellular mechanisms of physicochemical membrane homeostasis. Curr Opin Cell Biol 2018; 53:44-51. [PMID: 29787971 DOI: 10.1016/j.ceb.2018.04.013] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 04/19/2018] [Accepted: 04/29/2018] [Indexed: 12/11/2022]
Abstract
Biological membranes are vital, active contributors to cell function. In addition to specific interactions of individual lipid molecules and lateral organization produced by membrane domains, the bulk physicochemical properties of biological membranes broadly regulate protein structure and function. Therefore, these properties must be homeostatically maintained within a narrow range that is compatible with cellular physiology. Although such adaptiveness has been known for decades, recent observations have dramatically expanded its scope by showing the breadth of membrane properties that must be maintained, and revealing the remarkable diversity of biological membranes, both within and between cell types. Cells have developed a broad palette of sense-and-respond machineries to mediate physicochemical membrane homeostasis, and the molecular mechanisms of these are being discovered through combinations of cell biology, biophysical approaches, and computational modeling.
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Affiliation(s)
- Robert Ernst
- Department of Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany.
| | - Stephanie Ballweg
- Department of Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School at the University of Texas Health Science Center, Houston, TX, USA.
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83
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Godinho CP, Prata CS, Pinto SN, Cardoso C, Bandarra NM, Fernandes F, Sá-Correia I. Pdr18 is involved in yeast response to acetic acid stress counteracting the decrease of plasma membrane ergosterol content and order. Sci Rep 2018; 8:7860. [PMID: 29777118 PMCID: PMC5959924 DOI: 10.1038/s41598-018-26128-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 05/04/2018] [Indexed: 11/11/2022] Open
Abstract
Saccharomyces cerevisiae has the ability to become less sensitive to a broad range of chemically and functionally unrelated cytotoxic compounds. Among multistress resistance mechanisms is the one mediated by plasma membrane efflux pump proteins belonging to the ABC superfamily, questionably proposed to enhance the kinetics of extrusion of all these compounds. This study provides new insights into the biological role and impact in yeast response to acetic acid stress of the multistress resistance determinant Pdr18 proposed to mediate ergosterol incorporation in plasma membrane. The described coordinated activation of the transcription of PDR18 and of several ergosterol biosynthetic genes (ERG2-4, ERG6, ERG24) during the period of adaptation to acetic acid inhibited growth provides further support to the involvement of Pdr18 in yeast response to maintain plasma membrane ergosterol content in stressed cells. Pdr18 role in ergosterol homeostasis helps the cell to counteract acetic acid-induced decrease of plasma membrane lipid order, increase of the non-specific membrane permeability and decrease of transmembrane electrochemical potential. Collectively, our results support the notion that Pdr18-mediated multistress resistance is closely linked to the status of plasma membrane lipid environment related with ergosterol content and the associated plasma membrane properties.
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Affiliation(s)
- Cláudia P Godinho
- IBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
| | - Catarina S Prata
- IBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
| | - Sandra N Pinto
- IBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.,Centro de Química-Física Molecular, Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
| | - Carlos Cardoso
- DivAV, IPMA - Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho 6, 1495-006, Lisbon, Portugal
| | - Narcisa M Bandarra
- DivAV, IPMA - Instituto Português do Mar e da Atmosfera, Rua Alfredo Magalhães Ramalho 6, 1495-006, Lisbon, Portugal
| | - Fábio Fernandes
- IBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.,Centro de Química-Física Molecular, Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
| | - Isabel Sá-Correia
- IBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.
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84
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Leznicki P, Natarajan J, Bader G, Spevak W, Schlattl A, Abdul Rehman SA, Pathak D, Weidlich S, Zoephel A, Bordone MC, Barbosa-Morais NL, Boehmelt G, Kulathu Y. Expansion of DUB functionality generated by alternative isoforms - USP35, a case study. J Cell Sci 2018; 131:jcs.212753. [PMID: 29685892 DOI: 10.1242/jcs.212753] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 04/01/2018] [Indexed: 12/12/2022] Open
Abstract
Protein ubiquitylation is a dynamic post-translational modification that can be reversed by deubiquitylating enzymes (DUBs). It is unclear how the small number (∼100) of DUBs present in mammalian cells regulate the thousands of different ubiquitylation events. Here, we analysed annotated transcripts of human DUBs and found ∼300 ribosome-associated transcripts annotated as protein coding, which thus increases the total number of DUBs. By using USP35, a poorly studied DUB, as a case study, we provide evidence that alternative isoforms contribute to the functional expansion of DUBs. We show that there are two different USP35 isoforms that localise to different intracellular compartments and have distinct functions. Our results reveal that isoform 1 is an anti-apoptotic factor that inhibits staurosporine- and TNF-related apoptosis-inducing ligand (TRAIL; also known as TNFSF10)-induced apoptosis. In contrast, USP35 isoform 2 is an integral membrane protein of the endoplasmic reticulum (ER) that is also present at lipid droplets. Manipulations of isoform 2 levels cause rapid ER stress, likely through deregulation of lipid homeostasis, and lead to cell death. Our work highlights how alternative isoforms provide functional expansion of DUBs and sets directions for future research.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Pawel Leznicki
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Jayaprakash Natarajan
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Gerd Bader
- Boehringer Ingelheim RCV GmbH & Co KG, Dr. Boehringer Gasse 5-11, 1120 Vienna, Austria
| | - Walter Spevak
- Boehringer Ingelheim RCV GmbH & Co KG, Dr. Boehringer Gasse 5-11, 1120 Vienna, Austria
| | - Andreas Schlattl
- Boehringer Ingelheim RCV GmbH & Co KG, Dr. Boehringer Gasse 5-11, 1120 Vienna, Austria
| | - Syed Arif Abdul Rehman
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Deepika Pathak
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Simone Weidlich
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Andreas Zoephel
- Boehringer Ingelheim RCV GmbH & Co KG, Dr. Boehringer Gasse 5-11, 1120 Vienna, Austria
| | - Marie C Bordone
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisbon, Portugal
| | - Nuno L Barbosa-Morais
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisbon, Portugal
| | - Guido Boehmelt
- Boehringer Ingelheim RCV GmbH & Co KG, Dr. Boehringer Gasse 5-11, 1120 Vienna, Austria
| | - Yogesh Kulathu
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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85
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Membrane glycerolipid equilibrium under endoplasmic reticulum stress in Arabidopsis thaliana. Biochem Biophys Res Commun 2018. [PMID: 29524407 DOI: 10.1016/j.bbrc.2018.03.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Endoplasmic reticulum (ER) is an indispensable organelle for secretory protein synthesis as well as metabolism of phospholipids and their derivatives in eukaryotic cells. Various external and internal factors may cause an accumulation of aberrant proteins in the ER, which causes ER stress and activates cellular ER stress responses to cope with the stress. In animal research, molecular mechanisms for protein quality control upon ER stress are well documented; however, how cells maintain lipid homeostasis under ER stress is an emerging issue. The ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE), two major phospholipid classes, is important under ER stress in animal cells. However, in seed plants, no study has reported on the changes in membrane lipid content under ER stress, although a number of physiologically important environmental stresses, such as heat and salinity, induce ER stress. Here, we investigated membrane glycerolipid metabolism under ER stress in Arabidopsis. ER stress transcriptionally affected PC and PE biosynthesis pathways differentially, with no significant changes in membrane glycerolipid content. Our results suggest that higher plants maintain membrane lipid equilibrium during active transcription of phospholipid biosynthetic genes under ER stress.
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86
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Radanović T, Reinhard J, Ballweg S, Pesek K, Ernst R. An Emerging Group of Membrane Property Sensors Controls the Physical State of Organellar Membranes to Maintain Their Identity. Bioessays 2018; 40:e1700250. [PMID: 29574931 DOI: 10.1002/bies.201700250] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Revised: 02/06/2018] [Indexed: 11/06/2022]
Abstract
The biological membranes of eukaryotic cells harbor sensitive surveillance systems to establish, sense, and maintain characteristic physicochemical properties that ultimately define organelle identity. They are fundamentally important for membrane homeostasis and play active roles in cellular signaling, protein sorting, and the formation of vesicular carriers. Here, we compare the molecular mechanisms of Mga2 and Ire1, two sensors involved in the regulation of fatty acid desaturation and the response to unfolded proteins and lipid bilayer stress in order to identify their commonalities and specializations. We will speculate on the cellular significance of membrane property sensors in other organelles and discuss their putative mechanisms. Based on these findings, we propose membrane property sensors as an emerging class of proteins with wide implications for organelle communication and function.
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Affiliation(s)
- Toni Radanović
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - John Reinhard
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - Stephanie Ballweg
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - Kristina Pesek
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - Robert Ernst
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
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87
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Rybczynska AA, Boersma HH, de Jong S, Gietema JA, Noordzij W, Dierckx RAJO, Elsinga PH, van Waarde A. Avenues to molecular imaging of dying cells: Focus on cancer. Med Res Rev 2018. [PMID: 29528513 PMCID: PMC6220832 DOI: 10.1002/med.21495] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Successful treatment of cancer patients requires balancing of the dose, timing, and type of therapeutic regimen. Detection of increased cell death may serve as a predictor of the eventual therapeutic success. Imaging of cell death may thus lead to early identification of treatment responders and nonresponders, and to “patient‐tailored therapy.” Cell death in organs and tissues of the human body can be visualized, using positron emission tomography or single‐photon emission computed tomography, although unsolved problems remain concerning target selection, tracer pharmacokinetics, target‐to‐nontarget ratio, and spatial and temporal resolution of the scans. Phosphatidylserine exposure by dying cells has been the most extensively studied imaging target. However, visualization of this process with radiolabeled Annexin A5 has not become routine in the clinical setting. Classification of death modes is no longer based only on cell morphology but also on biochemistry, and apoptosis is no longer found to be the preponderant mechanism of cell death after antitumor therapy, as was earlier believed. These conceptual changes have affected radiochemical efforts. Novel probes targeting changes in membrane permeability, cytoplasmic pH, mitochondrial membrane potential, or caspase activation have recently been explored. In this review, we discuss molecular changes in tumors which can be targeted to visualize cell death and we propose promising biomarkers for future exploration.
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Affiliation(s)
- Anna A Rybczynska
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.,Department of Genetics, University of Groningen, Groningen, the Netherlands
| | - Hendrikus H Boersma
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.,Department of Clinical Pharmacy & Pharmacology, University of Groningen, Groningen, the Netherlands
| | - Steven de Jong
- Department of Medical Oncology, University of Groningen, Groningen, the Netherlands
| | - Jourik A Gietema
- Department of Medical Oncology, University of Groningen, Groningen, the Netherlands
| | - Walter Noordzij
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Rudi A J O Dierckx
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.,Department of Nuclear Medicine, Ghent University, Ghent, Belgium
| | - Philip H Elsinga
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Aren van Waarde
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
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88
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Garcia EJ, Vevea JD, Pon LA. Lipid droplet autophagy during energy mobilization, lipid homeostasis and protein quality control. Front Biosci (Landmark Ed) 2018; 23:1552-1563. [PMID: 29293450 DOI: 10.2741/4660] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Lipid droplets (LDs) have well-established functions as sites for lipid storage and energy mobilization to meet the metabolic demands of cells. However, recent studies have expanded the roles of LDs to protein quality control. Lipophagy, or LD degradation by autophagy, plays a vital role not only in the mobilization of free fatty acids (FFAs) and lipid homeostasis at LDs, but also in the adaptation of cells to certain forms of stress including lipid imbalance. Recent studies have provided new mechanistic insights about the diverse types of lipophagy, in particular microlipophagy. This review summarizes key findings about the mechanisms and functions of lipophagy and highlights a novel function of LD microlipophagy as a mechanism to maintain endoplasmic reticulum (ER) proteostasis under conditions of lipid imbalance.
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Affiliation(s)
- Enrique J Garcia
- Department of Pathology and Cell Biology, Columbia University, New York, NY, 10032 USA
| | - Jason D Vevea
- HHMI and Dept. of Neuroscience, University of Wisconsin, Madison, WI, 53705 USA
| | - Liza A Pon
- Department of Pathology and Cell Biology, Columbia University, New York, NY, 10032 USA,
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89
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Gianfrancesco MA, Paquot N, Piette J, Legrand-Poels S. Lipid bilayer stress in obesity-linked inflammatory and metabolic disorders. Biochem Pharmacol 2018; 153:168-183. [PMID: 29462590 DOI: 10.1016/j.bcp.2018.02.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 02/15/2018] [Indexed: 12/13/2022]
Abstract
The maintenance of the characteristic lipid compositions and physicochemical properties of biological membranes is essential for their proper function. Mechanisms allowing to sense and restore membrane homeostasis have been identified in prokaryotes for a long time and more recently in eukaryotes. A membrane remodeling can result from aberrant metabolism as seen in obesity. In this review, we describe how such lipid bilayer stress can account for the modulation of membrane proteins involved in the pathogenesis of obesity-linked inflammatory and metabolic disorders. We address the case of the Toll-like receptor 4 that is implicated in the obesity-related low grade inflammation and insulin resistance. The lipid raft-mediated TLR4 activation is promoted by an enrichment of the plasma membrane with saturated lipids or cholesterol increasing the lipid phase order. We discuss of the plasma membrane Na, K-ATPase that illustrates a new concept according to which direct interactions between specific residues and particular lipids determine both stability and activity of the pump in parallel with indirect effects of the lipid bilayer. The closely related sarco(endo)-plasmic Ca-ATPase embedded in the more fluid ER membrane seems to be more sensitive to a lipid bilayer stress as demonstrated by its inactivation in cholesterol-loaded macrophages or its inhibition mediated by an increased PtdCho/PtdEtn ratio in obese mice hepatocytes. Finally, we describe the model recently proposed for the activation of the conserved IRE-1 protein through alterations in the ER membrane lipid packing and thickness. Such IRE-1 activation could occur in response to abnormal lipid synthesis and membrane remodeling as observed in hepatocytes exposed to excess nutrients. Since the IRE-1/XBP1 branch also stimulates the lipid synthesis, this pathway could create a vicious cycle "lipogenesis-ER lipid bilayer stress-lipogenesis" amplifying hepatic ER pathology and the obesity-linked systemic metabolic defects.
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Affiliation(s)
- Marco A Gianfrancesco
- Laboratory of Immunometabolism and Nutrition, GIGA-I3, University of Liège, Liège, Belgium; Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University Hospital of Liège, Liège, Belgium
| | - Nicolas Paquot
- Laboratory of Immunometabolism and Nutrition, GIGA-I3, University of Liège, Liège, Belgium; Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University Hospital of Liège, Liège, Belgium
| | - Jacques Piette
- Laboratory of Virology and Immunology, GIGA-Molecular Biology of Diseases, University of Liège, Liège, Belgium
| | - Sylvie Legrand-Poels
- Laboratory of Immunometabolism and Nutrition, GIGA-I3, University of Liège, Liège, Belgium; Laboratory of Virology and Immunology, GIGA-Molecular Biology of Diseases, University of Liège, Liège, Belgium.
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90
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Ho N, Xu C, Thibault G. From the unfolded protein response to metabolic diseases - lipids under the spotlight. J Cell Sci 2018; 131:131/3/jcs199307. [PMID: 29439157 DOI: 10.1242/jcs.199307] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The unfolded protein response (UPR) is classically viewed as a stress response pathway to maintain protein homeostasis at the endoplasmic reticulum (ER). However, it has recently emerged that the UPR can be directly activated by lipid perturbation, independently of misfolded proteins. Comprising primarily phospholipids, sphingolipids and sterols, individual membranes can contain hundreds of distinct lipids. Even with such complexity, lipid distribution in a cell is tightly regulated by mechanisms that remain incompletely understood. It is therefore unsurprising that lipid dysregulation can be a key factor in disease development. Recent advances in analysis of lipids and their regulators have revealed remarkable mechanisms and connections to other cellular pathways including the UPR. In this Review, we summarize the current understanding in UPR transducers functioning as lipid sensors and the interplay between lipid metabolism and ER homeostasis in the context of metabolic diseases. We attempt to provide a framework consisting of a few key principles to integrate the different lines of evidence and explain this rather complicated mechanism.
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Affiliation(s)
- Nurulain Ho
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551
| | - Chengchao Xu
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142-1479, USA
| | - Guillaume Thibault
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551
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91
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Hosios AM, Vander Heiden MG. The redox requirements of proliferating mammalian cells. J Biol Chem 2018; 293:7490-7498. [PMID: 29339555 DOI: 10.1074/jbc.tm117.000239] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cell growth and division require nutrients, and proliferating cells use a variety of sources to acquire the amino acids, lipids, and nucleotides that support macromolecule synthesis. Lipids are more reduced than other nutrients, whereas nucleotides and amino acids are typically more oxidized. Cells must therefore generate reducing and oxidizing (redox) equivalents to convert consumed nutrients into biosynthetic precursors. To that end, redox cofactor metabolism plays a central role in meeting cellular redox requirements. In this Minireview, we highlight the biosynthetic pathways that involve redox reactions and discuss their integration with metabolism in proliferating mammalian cells.
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Affiliation(s)
- Aaron M Hosios
- From the Koch Institute for Integrative Cancer Research and.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and
| | - Matthew G Vander Heiden
- From the Koch Institute for Integrative Cancer Research and .,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and.,the Dana-Farber Cancer Institute, Boston, Massachusetts 02115
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92
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Deprez MA, Eskes E, Wilms T, Ludovico P, Winderickx J. pH homeostasis links the nutrient sensing PKA/TORC1/Sch9 ménage-à-trois to stress tolerance and longevity. MICROBIAL CELL 2018; 5:119-136. [PMID: 29487859 PMCID: PMC5826700 DOI: 10.15698/mic2018.03.618] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The plasma membrane H+-ATPase Pma1 and the vacuolar V-ATPase act in close harmony to tightly control pH homeostasis, which is essential for a vast number of physiological processes. As these main two regulators of pH are responsive to the nutritional status of the cell, it seems evident that pH homeostasis acts in conjunction with nutrient-induced signalling pathways. Indeed, both PKA and the TORC1-Sch9 axis influence the proton pumping activity of the V-ATPase and possibly also of Pma1. In addition, it recently became clear that the proton acts as a second messenger to signal glucose availability via the V-ATPase to PKA and TORC1-Sch9. Given the prominent role of nutrient signalling in longevity, it is not surprising that pH homeostasis has been linked to ageing and longevity as well. A first indication is provided by acetic acid, whose uptake by the cell induces toxicity and affects longevity. Secondly, vacuolar acidity has been linked to autophagic processes, including mitophagy. In agreement with this, a decline in vacuolar acidity was shown to induce mitochondrial dysfunction and shorten lifespan. In addition, the asymmetric inheritance of Pma1 has been associated with replicative ageing and this again links to repercussions on vacuolar pH. Taken together, accumulating evidence indicates that pH homeostasis plays a prominent role in the determination of ageing and longevity, thereby providing new perspectives and avenues to explore the underlying molecular mechanisms.
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Affiliation(s)
| | - Elja Eskes
- Functional Biology, KU Leuven, Leuven, Belgium
| | | | - Paula Ludovico
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
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93
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Niu Y, Xiang Y. An Overview of Biomembrane Functions in Plant Responses to High-Temperature Stress. FRONTIERS IN PLANT SCIENCE 2018; 9:915. [PMID: 30018629 PMCID: PMC6037897 DOI: 10.3389/fpls.2018.00915] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 06/08/2018] [Indexed: 05/03/2023]
Abstract
Biological membranes are highly ordered structures consisting of mosaics of lipids and proteins. Elevated temperatures can directly and effectively change the properties of these membranes, including their fluidity and permeability, through a holistic effect that involves changes in the lipid composition and/or interactions between lipids and specific membrane proteins. Ultimately, high temperatures can alter microdomain remodeling and instantaneously relay ambient cues to downstream signaling pathways. Thus, dynamic membrane regulation not only helps cells perceive temperature changes but also participates in intracellular responses and determines a cell's fate. Moreover, due to the specific distribution of extra- and endomembrane elements, the plasma membrane (PM) and membranous organelles are individually responsible for distinct developmental events during plant adaptation to heat stress. This review describes recent studies that focused on the roles of various components that can alter the physical state of the plasma and thylakoid membranes as well as the crucial signaling pathways initiated through the membrane system, encompassing both endomembranes and membranous organelles in the context of heat stress responses.
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Affiliation(s)
- Yue Niu
- *Correspondence: Yue Niu, Yun Xiang,
| | - Yun Xiang
- *Correspondence: Yue Niu, Yun Xiang,
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94
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Slp1-Emp65: A Guardian Factor that Protects Folding Polypeptides from Promiscuous Degradation. Cell 2017; 171:346-357.e12. [DOI: 10.1016/j.cell.2017.08.036] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 07/06/2017] [Accepted: 08/21/2017] [Indexed: 02/05/2023]
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95
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Hu T, Zhang JL. Mass-spectrometry-based lipidomics. J Sep Sci 2017; 41:351-372. [PMID: 28859259 DOI: 10.1002/jssc.201700709] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 08/17/2017] [Accepted: 08/18/2017] [Indexed: 01/09/2023]
Abstract
Lipids, which have a core function in energy storage, signalling and biofilm structures, play important roles in a variety of cellular processes because of the great diversity of their structural and physiochemical properties. Lipidomics is the large-scale profiling and quantification of biogenic lipid molecules, the comprehensive study of their pathways and the interpretation of their physiological significance based on analytical chemistry and statistical analysis. Lipidomics will not only provide insight into the physiological functions of lipid molecules but will also provide an approach to discovering important biomarkers for diagnosis or treatment of human diseases. Mass-spectrometry-based analytical techniques are currently the most widely used and most effective tools for lipid profiling and quantification. In this review, the field of mass-spectrometry-based lipidomics was discussed. Recent progress in all essential steps in lipidomics was carefully discussed in this review, including lipid extraction strategies, separation techniques and mass-spectrometry-based analytical and quantitative methods in lipidomics. We also focused on novel resolution strategies for difficult problems in determining C=C bond positions in lipidomics. Finally, new technologies that were developed in recent years including single-cell lipidomics, flux-based lipidomics and multiomics technologies were also reviewed.
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Affiliation(s)
- Ting Hu
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, PR China
| | - Jin-Lan Zhang
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, PR China
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96
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Cohen N, Breker M, Bakunts A, Pesek K, Chas A, Argemí J, Orsi A, Gal L, Chuartzman S, Wigelman Y, Jonas F, Walter P, Ernst R, Aragón T, van Anken E, Schuldiner M. Iron affects Ire1 clustering propensity and the amplitude of endoplasmic reticulum stress signaling. J Cell Sci 2017; 130:3222-3233. [PMID: 28794014 PMCID: PMC5665437 DOI: 10.1242/jcs.201715] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 08/02/2017] [Indexed: 01/10/2023] Open
Abstract
The unfolded protein response (UPR) allows cells to adjust secretory pathway capacity according to need. Ire1, the endoplasmic reticulum (ER) stress sensor and central activator of the UPR is conserved from the budding yeast Saccharomyces cerevisiae to humans. Under ER stress conditions, Ire1 clusters into foci that enable optimal UPR activation. To discover factors that affect Ire1 clustering, we performed a high-content screen using a whole-genome yeast mutant library expressing Ire1–mCherry. We imaged the strains following UPR induction and found 154 strains that displayed alterations in Ire1 clustering. The hits were enriched for iron and heme effectors and binding proteins. By performing pharmacological depletion and repletion, we confirmed that iron (Fe3+) affects UPR activation in both yeast and human cells. We suggest that Ire1 clustering propensity depends on membrane composition, which is governed by heme-dependent biosynthesis of sterols. Our findings highlight the diverse cellular functions that feed into the UPR and emphasize the cross-talk between organelles required to concertedly maintain homeostasis. Highlighted Article: To respond to folding stress in the ER, cells activate the conserved sensor Ire1. We show that iron is required for optimal Ire1 activation and suggest this is because iron is required for ergosterol biosynthesis.
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Affiliation(s)
- Nir Cohen
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Michal Breker
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.,The Rockefeller University, New York, NY 10065, USA
| | - Anush Bakunts
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Ospedale San Raffaele, Via Olgettina 58, 20132, Milan, Italy
| | - Kristina Pesek
- Institute of Biochemistry and Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Max-von-Laue Str. 15, 60438 Frankfurt, Germany
| | - Ainara Chas
- Center for Applied Medical Research, Department of Gene Therapy and Regulation of Gene Expression. University of Navarra, 55 Pio XII St. 31008 Pamplona, Spain
| | - Josepmaria Argemí
- Center for Applied Medical Research, Department of Gene Therapy and Regulation of Gene Expression. University of Navarra, 55 Pio XII St. 31008 Pamplona, Spain
| | - Andrea Orsi
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Ospedale San Raffaele, Via Olgettina 58, 20132, Milan, Italy
| | - Lihi Gal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Silvia Chuartzman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Yoav Wigelman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Felix Jonas
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Peter Walter
- Department of Biochemistry & Biophysics, University of California San Francisco and Howard Hughes Medical Institute, San Francisco, CA 94143, USA
| | - Robert Ernst
- Center for Molecular Signaling, Institute of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Tomás Aragón
- Center for Applied Medical Research, Department of Gene Therapy and Regulation of Gene Expression. University of Navarra, 55 Pio XII St. 31008 Pamplona, Spain
| | - Eelco van Anken
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Ospedale San Raffaele, Via Olgettina 58, 20132, Milan, Italy
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
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97
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Welte MA, Gould AP. Lipid droplet functions beyond energy storage. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1260-1272. [PMID: 28735096 PMCID: PMC5595650 DOI: 10.1016/j.bbalip.2017.07.006] [Citation(s) in RCA: 364] [Impact Index Per Article: 45.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/17/2017] [Accepted: 07/17/2017] [Indexed: 02/07/2023]
Abstract
Lipid droplets are cytoplasmic organelles that store neutral lipids and are critically important for energy metabolism. Their function in energy storage is firmly established and increasingly well characterized. However, emerging evidence indicates that lipid droplets also play important and diverse roles in the cellular handling of lipids and proteins that may not be directly related to energy homeostasis. Lipid handling roles of droplets include the storage of hydrophobic vitamin and signaling precursors, and the management of endoplasmic reticulum and oxidative stress. Roles of lipid droplets in protein handling encompass functions in the maturation, storage, and turnover of cellular and viral polypeptides. Other potential roles of lipid droplets may be connected with their intracellular motility and, in some cases, their nuclear localization. This diversity highlights that lipid droplets are very adaptable organelles, performing different functions in different biological contexts. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY, United States.
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98
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Halbleib K, Pesek K, Covino R, Hofbauer HF, Wunnicke D, Hänelt I, Hummer G, Ernst R. Activation of the Unfolded Protein Response by Lipid Bilayer Stress. Mol Cell 2017; 67:673-684.e8. [PMID: 28689662 DOI: 10.1016/j.molcel.2017.06.012] [Citation(s) in RCA: 242] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 05/15/2017] [Accepted: 06/13/2017] [Indexed: 11/29/2022]
Abstract
The unfolded protein response (UPR) is a conserved homeostatic program that is activated by misfolded proteins in the lumen of the endoplasmic reticulum (ER). Recently, it became evident that aberrant lipid compositions of the ER membrane, referred to as lipid bilayer stress, are equally potent in activating the UPR. The underlying molecular mechanism, however, remained unclear. We show that the most conserved transducer of ER stress, Ire1, uses an amphipathic helix (AH) to sense membrane aberrancies and control UPR activity. In vivo and in vitro experiments, together with molecular dynamics (MD) simulations, identify the physicochemical properties of the membrane environment that control Ire1 oligomerization. This work establishes the molecular mechanism of UPR activation by lipid bilayer stress.
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Affiliation(s)
- Kristina Halbleib
- Institute of Biochemistry and Buchmann Institute for Molecular Life Sciences, Goethe-University, Frankfurt, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany
| | - Kristina Pesek
- Institute of Biochemistry and Buchmann Institute for Molecular Life Sciences, Goethe-University, Frankfurt, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany
| | - Roberto Covino
- Department of Theoretical Biophysics, Max-Planck-Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt, Germany
| | - Harald F Hofbauer
- Institute of Biochemistry and Buchmann Institute for Molecular Life Sciences, Goethe-University, Frankfurt, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany
| | - Dorith Wunnicke
- Institute of Biochemistry, Goethe-University, Frankfurt, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany
| | - Inga Hänelt
- Institute of Biochemistry, Goethe-University, Frankfurt, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max-Planck-Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt, Germany; Institute of Biophysics, Goethe-University, 60438 Frankfurt, Germany
| | - Robert Ernst
- Institute of Biochemistry and Buchmann Institute for Molecular Life Sciences, Goethe-University, Frankfurt, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany; Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany.
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99
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Kono N, Amin-Wetzel N, Ron D. Generic membrane-spanning features endow IRE1α with responsiveness to membrane aberrancy. Mol Biol Cell 2017; 28:2318-2332. [PMID: 28615323 PMCID: PMC5555659 DOI: 10.1091/mbc.e17-03-0144] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 06/07/2017] [Accepted: 06/09/2017] [Indexed: 12/16/2022] Open
Abstract
Previous studies indicated that IRE1α responds to membrane aberrancy via its transmembrane domain (TMD); however, little is known about the TMD features involved. Use of CRISPR/Cas9-mediated gene editing shows that generic membrane-spanning features of the TMD are sufficient for IRE1α’s responsiveness to membrane aberrancy. Altered cellular lipid composition activates the endoplasmic reticulum unfolded protein response (UPR), and UPR signaling effects important changes in lipid metabolism. Secondary effects on protein folding homeostasis likely contribute to UPR activation, but deletion of the unfolded protein stress-sensing luminal domain of the UPR transducers PERK and IRE1α does not abolish their responsiveness to lipid perturbation. This finding suggests that PERK and IRE1α also directly recognize the membrane aberrancy wrought by lipid perturbation. However, beyond the need for a transmembrane domain (TMD), little is known about the features involved. Regulation of the UPR transducers entails changes in their oligomeric state and is easily corrupted by overexpression. We used CRISPR/Cas9-mediated gene editing of the Ern1 locus to study the role of the TMD in the ability of the endogenous IRE1α protein to recognize membrane aberrancy in mammalian cells. Conducted in the background of a point mutation that isolated the response to membrane aberrancy induced by palmitate from unfolded protein stress, our analysis shows that generic membrane-spanning features of the TMD are sufficient for IRE1α’s responsiveness to membrane aberrancy. Our data suggest that IRE1α’s conserved TMD may have been selected for features imparting a relatively muted response to acyl-chain saturation.
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Affiliation(s)
- Nozomu Kono
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Niko Amin-Wetzel
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - David Ron
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
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100
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Shi M, Song W, Han T, Chang B, Li G, Jin J, Zhang Y. Role of the unfolded protein response in topography-induced osteogenic differentiation in rat bone marrow mesenchymal stem cells. Acta Biomater 2017; 54:175-185. [PMID: 28315494 DOI: 10.1016/j.actbio.2017.03.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Revised: 03/09/2017] [Accepted: 03/12/2017] [Indexed: 12/20/2022]
Abstract
The topography of biomaterials can significantly influence the osteogenic differentiation of cells. Understanding topographical signal transduction is critical for developing biofunctional surfaces, but the current knowledge is insufficient. Recently, numerous reports have suggested that the unfolded protein response (UPR) and osteogenic differentiation are inter-linked. Therefore, we hypothesize that the UPR pathway may be involved in the topography-induced osteogenesis. In the present study, different surface topographies were fabricated on pure titanium foils and the endoplasmic reticulum (ER) stress and UPR pathway were systematically investigated. We found that ER stress and the PERK-eIF2α-ATF4 pathway were activated in a time- and topography-dependent manner. Additionally, the activation of the PERK-eIF2α-ATF4 pathway by different topographies was in line with their osteogenic induction capability. More specifically, the osteogenic differentiation could be enhanced or weakened when the PERK-eIF2α-ATF4 pathway was promoted or inhibited, respectively. Furthermore, tuning of the degree of ER stress with different concentrations of thapsigargin revealed that mild ER stress promotes osteogenic differentiation, whereas excessive ER stress inhibits osteogenic differentiation and causes apoptosis. Taken together, our findings suggest that the UPR may play a critical role in topography-induced osteogenic differentiation, which may help to provide new insights into topographical signal transduction. STATEMENT OF SIGNIFICANCE Suitable implant surface topography can effectively improve bioactivity and eventual bone affinity. However, the mechanism of topographical signaling transduction is unclear and criteria for designation of an appropriate implant surface topography is lacking. This study shows that the ER stress and PERK-eIF2α-ATF4 pathway were activated by micro- and micro/nano-topographies, which is corresponding to the osteogenic induction abilities of these topographies. Furthermore, we have found that mild ER stress improves osteogenic differentiation, whereas excessive ER stress inhibits osteogenic differentiation and causes apoptosis. Our findings demonstrate that the UPR plays a critical role in the topography induced osteogenic differentiation, which may help to provide new insights into the topographical signaling transduction.
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Affiliation(s)
- Mengqi Shi
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Wen Song
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Tianxiao Han
- Department of Prosthodontics, School of Stomatology, Capital Medical University, Beijing 100050, PR China
| | - Bei Chang
- PLA Rocket Force General Hospital, Beijing 100088, PR China
| | - Guangwen Li
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Jianfeng Jin
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Periodontology, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Yumei Zhang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, PR China.
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