1
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Rajakumar T, Hossain MA, Stopka SA, Micoogullari Y, Ang J, Agar NYR, Hanna J. Dysregulation of ceramide metabolism causes phytoceramide-dependent induction of the unfolded protein response. Mol Biol Cell 2024; 35:ar117. [PMID: 39024283 DOI: 10.1091/mbc.e24-03-0121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024] Open
Abstract
The unfolded protein response (UPR) detects and mitigates the harmful effects of dysregulated endoplasmic reticulum (ER) function. The UPR has been best characterized as a protein quality control response, and the sole UPR sensor in yeast, Ire1, is known to detect misfolded ER proteins. However, recent work suggests the UPR can also sense diverse defects within the ER membrane, including increased fatty acid saturation and altered phospholipid abundance. These and other lipid-related stimuli have been referred to as lipid bilayer stress and may be sensed independently through Ire1's transmembrane domain. Here, we show that the loss of Isc1, a phospholipase that catabolizes complex ceramides, causes UPR induction, even in the absence of exogenous stress. A series of chemical and genetic approaches identified a requirement for very long-chain fatty acid (VLCFA)-containing phytoceramides for UPR induction. In parallel, comprehensive lipidomics analyses identified large increases in the abundance of specific VLCFA-containing phytoceramides in the isc1Δ mutant. We failed to identify evidence of an accompanying defect in protein quality control or ER-associated protein degradation. These results extend our understanding of lipid bilayer stress in the UPR and provide a foundation for mechanistic investigation of this fascinating intersection between ceramide metabolism, membrane homeostasis, and the UPR.
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Affiliation(s)
- Tamayanthi Rajakumar
- Department of Pathology, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Md Amin Hossain
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Sylwia A Stopka
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Yagmur Micoogullari
- Department of Pathology, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Jessie Ang
- Department of Pathology, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - Nathalie Y R Agar
- Department of Neurosurgery, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
| | - John Hanna
- Department of Pathology, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115
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2
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Miller JM, Tragesser-Tiña ME, Turk SM, Rubenstein EM. Loss of transcriptional regulator of phospholipid biosynthesis alters post-translational modification of Sec61 translocon beta subunit Sbh1 in Saccharomyces cerevisiae. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001260. [PMID: 39071171 PMCID: PMC11282434 DOI: 10.17912/micropub.biology.001260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2024] [Revised: 07/09/2024] [Accepted: 07/11/2024] [Indexed: 07/30/2024]
Abstract
We recently discovered that disrupting phospholipid biosynthesis by eliminating the Ino2/4 transcriptional regulator impairs endoplasmic reticulum (ER)-associated degradation (ERAD) in Saccharomyces cerevisiae , but the mechanism is unclear. Phosphatidylcholine deficiency has been reported to accelerate degradation of Sec61 translocon beta subunit Sbh1 and ERAD cofactor Cue1. Here, we found that, unlike targeted phosphatidylcholine depletion, INO4 deletion does not destabilize Sbh1 or Cue1. However, we observed altered electrophoretic mobility of Sbh1 in ino4 Δ yeast, consistent with phospholipid-responsive post-translational modification. A better understanding of the molecular consequences of disrupted lipid homeostasis could lead to enhanced treatments for conditions associated with perturbed lipid biosynthesis.
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Affiliation(s)
| | - Mary E. Tragesser-Tiña
- Department of Biology, Ball State University
- Diabetes, Obesity, and Complications Therapeutic Area, Eli Lilly and Company
| | - Samantha M. Turk
- Department of Biology, Ball State University
- Graduate School of Biomedical Sciences and Department of Developmental Neurobiology, St. Jude Graduate School of Biomedical Science
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3
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Kettel P, Karagöz GE. Endoplasmic reticulum: Monitoring and maintaining protein and membrane homeostasis in the endoplasmic reticulum by the unfolded protein response. Int J Biochem Cell Biol 2024; 172:106598. [PMID: 38768891 DOI: 10.1016/j.biocel.2024.106598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 05/01/2024] [Accepted: 05/14/2024] [Indexed: 05/22/2024]
Abstract
The endoplasmic reticulum (ER) regulates essential cellular processes, including protein folding, lipid synthesis, and calcium homeostasis. The ER homeostasis is maintained by a conserved set of signaling cascades called the Unfolded Protein Response (UPR). How the UPR senses perturbations in ER homeostasis has been the subject of active research for decades. In metazoans, the UPR consists of three ER-membrane embedded sensors: IRE1, PERK and ATF6. These sensors detect the accumulation of misfolded proteins in the ER lumen and adjust protein folding capacity according to cellular needs. Early work revealed that the ER-resident chaperone BiP binds to all three UPR sensors in higher eukaryotes and BiP binding was suggested to regulate their activity. More recent data have shown that in higher eukaryotes the interaction of the UPR sensors with a complex network of chaperones and misfolded proteins modulates their activation and deactivation dynamics. Furthermore, emerging evidence suggests that the UPR monitors ER membrane integrity beyond protein folding defects. However, the mechanistic and structural basis of UPR activation by proteotoxic and lipid bilayer stress in higher eukaryotes remains only partially understood. Here, we review the current understanding of novel protein interaction networks and the contribution of the lipid membrane environment to UPR activation.
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Affiliation(s)
- Paulina Kettel
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - G Elif Karagöz
- Max Perutz Laboratories Vienna, Vienna BioCenter, Vienna, Austria; Medical University of Vienna, Vienna, Austria.
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4
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Liu R, Hong W, Hou D, Huang H, Duan C. Decoding Organelle Interactions: Unveiling Molecular Mechanisms and Disease Therapies. Adv Biol (Weinh) 2024; 8:e2300288. [PMID: 38717793 DOI: 10.1002/adbi.202300288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 01/05/2024] [Indexed: 07/13/2024]
Abstract
Organelles, substructures in the cytoplasm with specific morphological structures and functions, interact with each other via membrane fusion, membrane transport, and protein interactions, collectively termed organelle interaction. Organelle interaction is a complex biological process involving the interaction and regulation of several organelles, including the interaction between mitochondria-endoplasmic reticulum, endoplasmic reticulum-Golgi, mitochondria-lysosomes, and endoplasmic reticulum-peroxisomes. This interaction enables intracellular substance transport, metabolism, and signal transmission, and is closely related to the occurrence, development, and treatment of many diseases, such as cancer, neurodegenerative diseases, and metabolic diseases. Herein, the mechanisms and regulation of organelle interactions are reviewed, which are critical for understanding basic principles of cell biology and disease development mechanisms. The findings will help to facilitate the development of novel strategies for disease prevention, diagnosis, and treatment opportunities.
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Affiliation(s)
- Ruixue Liu
- Department of Anesthesiology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China
| | - Weilong Hong
- Department of Anesthesiology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China
| | - Dongyao Hou
- Department of Anesthesiology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China
| | - He Huang
- Department of Anesthesiology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China
| | - Chenyang Duan
- Department of Anesthesiology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China
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5
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Turk SM, Indovina CJ, Miller JM, Overton DL, Runnebohm AM, Orchard CJ, Tragesser-Tiña ME, Gosser SK, Doss EM, Richards KA, Irelan CB, Daraghmi MM, Bailey CG, Niekamp JM, Claypool KP, Engle SM, Buchanan BW, Woodruff KA, Olesen JB, Smaldino PJ, Rubenstein EM. Lipid biosynthesis perturbation impairs endoplasmic reticulum-associated degradation. J Biol Chem 2023; 299:104939. [PMID: 37331602 PMCID: PMC10372827 DOI: 10.1016/j.jbc.2023.104939] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/02/2023] [Accepted: 06/09/2023] [Indexed: 06/20/2023] Open
Abstract
The relationship between lipid homeostasis and protein homeostasis (proteostasis) is complex and remains incompletely understood. We conducted a screen for genes required for efficient degradation of Deg1-Sec62, a model aberrant translocon-associated substrate of the endoplasmic reticulum (ER) ubiquitin ligase Hrd1, in Saccharomyces cerevisiae. This screen revealed that INO4 is required for efficient Deg1-Sec62 degradation. INO4 encodes one subunit of the Ino2/Ino4 heterodimeric transcription factor, which regulates expression of genes required for lipid biosynthesis. Deg1-Sec62 degradation was also impaired by mutation of genes encoding several enzymes mediating phospholipid and sterol biosynthesis. The degradation defect in ino4Δ yeast was rescued by supplementation with metabolites whose synthesis and uptake are mediated by Ino2/Ino4 targets. Stabilization of a panel of substrates of the Hrd1 and Doa10 ER ubiquitin ligases by INO4 deletion indicates ER protein quality control is generally sensitive to perturbed lipid homeostasis. Loss of INO4 sensitized yeast to proteotoxic stress, suggesting a broad requirement for lipid homeostasis in maintaining proteostasis. A better understanding of the dynamic relationship between lipid homeostasis and proteostasis may lead to improved understanding and treatment of several human diseases associated with altered lipid biosynthesis.
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Affiliation(s)
- Samantha M Turk
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - Jacob M Miller
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | | | - Cade J Orchard
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | | | - Ellen M Doss
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Kyle A Richards
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | | | - Connor G Bailey
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Julia M Niekamp
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - Sarah M Engle
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Bryce W Buchanan
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - James B Olesen
- Department of Biology, Ball State University, Muncie, Indiana, USA
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6
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Hwang J, Peterson BG, Knupp J, Baldridge RD. The ERAD system is restricted by elevated ceramides. SCIENCE ADVANCES 2023; 9:eadd8579. [PMID: 36638172 PMCID: PMC9839339 DOI: 10.1126/sciadv.add8579] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 12/15/2022] [Indexed: 06/17/2023]
Abstract
Misfolded proteins in the endoplasmic reticulum (ER) are removed through a process known as ER-associated degradation (ERAD). ERAD occurs through an integral membrane protein quality control system that recognizes substrates, retrotranslocates the substrates across the membrane, and ubiquitinates and extracts the substrates from the membrane for degradation at the cytosolic proteasome. While ERAD systems are known to regulate lipid biosynthetic enzymes, the regulation of ERAD systems by the lipid composition of cellular membranes remains unexplored. Here, we report that the ER membrane composition influences ERAD function by incapacitating substrate extraction. Unbiased lipidomic profiling revealed that elevation of specific very-long-chain ceramides leads to a marked increase in the level of ubiquitinated substrates in the ER membrane and concomitantly reduces extracted substrates in the cytoplasm. This work reveals a previously unrecognized mechanism in which ER membrane lipid remodeling changes the activity of ERAD.
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Affiliation(s)
- Jiwon Hwang
- Department of Biological Chemistry, University of Michigan Medical School, 1150 W Medical Center Drive, Ann Arbor, MI 48109, USA
| | - Brian G. Peterson
- Department of Biological Chemistry, University of Michigan Medical School, 1150 W Medical Center Drive, Ann Arbor, MI 48109, USA
| | - Jeffrey Knupp
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Ryan D. Baldridge
- Department of Biological Chemistry, University of Michigan Medical School, 1150 W Medical Center Drive, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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7
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Castillo-Quan JI, Steinbaugh MJ, Fernández-Cárdenas LP, Pohl NK, Wu Z, Zhu F, Moroz N, Teixeira V, Bland MS, Lehrbach NJ, Moronetti L, Teufl M, Blackwell TK. An antisteatosis response regulated by oleic acid through lipid droplet-mediated ERAD enhancement. SCIENCE ADVANCES 2023; 9:eadc8917. [PMID: 36598980 PMCID: PMC9812393 DOI: 10.1126/sciadv.adc8917] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 11/23/2022] [Indexed: 05/19/2023]
Abstract
Although excessive lipid accumulation is a hallmark of obesity-related pathologies, some lipids are beneficial. Oleic acid (OA), the most abundant monounsaturated fatty acid (FA), promotes health and longevity. Here, we show that OA benefits Caenorhabditis elegans by activating the endoplasmic reticulum (ER)-resident transcription factor SKN-1A (Nrf1/NFE2L1) in a lipid homeostasis response. SKN-1A/Nrf1 is cleared from the ER by the ER-associated degradation (ERAD) machinery and stabilized when proteasome activity is low and canonically maintains proteasome homeostasis. Unexpectedly, OA increases nuclear SKN-1A levels independently of proteasome activity, through lipid droplet-dependent enhancement of ERAD. In turn, SKN-1A reduces steatosis by reshaping the lipid metabolism transcriptome and mediates longevity from OA provided through endogenous accumulation, reduced H3K4 trimethylation, or dietary supplementation. Our findings reveal an unexpected mechanism of FA signal transduction, as well as a lipid homeostasis pathway that provides strategies for opposing steatosis and aging, and may mediate some benefits of the OA-rich Mediterranean diet.
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Affiliation(s)
- Jorge Iván Castillo-Quan
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Michael J. Steinbaugh
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Laura Paulette Fernández-Cárdenas
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Nancy K. Pohl
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Ziyun Wu
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Feimei Zhu
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Natalie Moroz
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Biology Department, Emmanuel College, Boston, MA, USA
| | - Veronica Teixeira
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Monet S. Bland
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Nicolas J. Lehrbach
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Lorenza Moronetti
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - Magdalena Teufl
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
| | - T. Keith Blackwell
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA
- Corresponding author.
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8
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Sánchez-Álvarez M, Del Pozo MÁ, Bosch M, Pol A. Insights Into the Biogenesis and Emerging Functions of Lipid Droplets From Unbiased Molecular Profiling Approaches. Front Cell Dev Biol 2022; 10:901321. [PMID: 35756995 PMCID: PMC9213792 DOI: 10.3389/fcell.2022.901321] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/17/2022] [Indexed: 11/30/2022] Open
Abstract
Lipid droplets (LDs) are spherical, single sheet phospholipid-bound organelles that store neutral lipids in all eukaryotes and some prokaryotes. Initially conceived as relatively inert depots for energy and lipid precursors, these highly dynamic structures play active roles in homeostatic functions beyond metabolism, such as proteostasis and protein turnover, innate immunity and defense. A major share of the knowledge behind this paradigm shift has been enabled by the use of systematic molecular profiling approaches, capable of revealing and describing these non-intuitive systems-level relationships. Here, we discuss these advances and some of the challenges they entail, and highlight standing questions in the field.
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Affiliation(s)
- Miguel Sánchez-Álvarez
- Cell and Developmental Biology Area, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Miguel Ángel Del Pozo
- Cell and Developmental Biology Area, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Marta Bosch
- Lipid Trafficking and Disease Group, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Biomedical Sciences, Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain
| | - Albert Pol
- Lipid Trafficking and Disease Group, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Biomedical Sciences, Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
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9
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Can ND, Basturk E, Kizilboga T, Akcay IM, Dingiloglu B, Tatli O, Acar S, Ozfiliz Kilbas P, Elbeyli E, Muratcioglu S, Jannuzzi AT, Gursoy A, Keskin O, Doganay HL, Karademir Yilmaz B, Dinler Doganay G. Interactome analysis of Bag-1 isoforms reveals novel interaction partners in endoplasmic reticulum-associated degradation. PLoS One 2021; 16:e0256640. [PMID: 34428256 PMCID: PMC8384158 DOI: 10.1371/journal.pone.0256640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 08/11/2021] [Indexed: 11/24/2022] Open
Abstract
Bag-1 is a multifunctional protein that regulates Hsp70 chaperone activity, apoptosis, and proliferation. The three major Bag-1 isoforms have different subcellular localizations and partly non-overlapping functions. To identify the detailed interaction network of each isoform, we utilized mass spectrometry-based proteomics and found that interactomes of Bag-1 isoforms contained many common proteins, with variations in their abundances. Bag-1 interactomes were enriched with proteins involved in protein processing and degradation pathways. Novel interaction partners included VCP/p97; a transitional ER ATPase, Rad23B; a shuttling factor for ubiquitinated proteins, proteasome components, and ER-resident proteins, suggesting a role for Bag-1 also in ER-associated protein degradation (ERAD). Bag-1 pull-down from cells and tissues from breast cancer patients validated these interactions and showed cancer-related prominence. Using in silico predictions we detected hotspot residues of Bag-1. Mutations of these residues caused loss of binding to protein quality control elements and impaired proteasomal activity in MCF-7 cells. Following CD147 glycosylation pattern, we showed that Bag-1 downregulated VCP/p97-dependent ERAD. Overall, our data extends the interaction map of Bag-1, and broadens its role in protein homeostasis. Targeting the interaction surfaces revealed in this study might be an effective strategy in the treatment of cancer.
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Affiliation(s)
- Nisan Denizce Can
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
| | - Ezgi Basturk
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
| | - Tugba Kizilboga
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
| | - Izzet Mehmet Akcay
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
| | - Baran Dingiloglu
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
| | - Ozge Tatli
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
- Molecular Biology and Genetics Department, Istanbul Medeniyet University, Istanbul, Turkey
| | - Sevilay Acar
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
| | - Pelin Ozfiliz Kilbas
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
- Department of Molecular Biology and Genetics, Istanbul Kultur University, Istanbul, Turkey
| | - Efe Elbeyli
- Department of Chemical and Biological Engineering, Koc University, Istanbul, Turkey
| | - Serena Muratcioglu
- Department of Chemical and Biological Engineering, Koc University, Istanbul, Turkey
| | - Ayse Tarbin Jannuzzi
- Faculty of Pharmacy, Department of Pharmaceutical Toxicology, Istanbul University, Istanbul, Turkey
| | - Attila Gursoy
- Department of Chemical and Biological Engineering, Koc University, Istanbul, Turkey
| | - Ozlem Keskin
- Department of Chemical and Biological Engineering, Koc University, Istanbul, Turkey
| | | | - Betul Karademir Yilmaz
- Department of Biochemistry, School of Medicine/Genetic and Metabolic Diseases Research and Investigation Center, Marmara University, Istanbul, Turkey
| | - Gizem Dinler Doganay
- Department of Molecular Biology—Genetics and Biotechnology, Istanbul Technical University, Istanbul, Turkey
- * E-mail:
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10
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Abstract
Lipid droplets (LDs) are endoplasmic reticulum-derived organelles that consist of a core of neutral lipids encircled by a phospholipid monolayer decorated with proteins. As hubs of cellular lipid and energy metabolism, LDs are inherently involved in the etiology of prevalent metabolic diseases such as obesity and nonalcoholic fatty liver disease. The functions of LDs are regulated by a unique set of associated proteins, the LD proteome, which includes integral membrane and peripheral proteins. These proteins control key activities of LDs such as triacylglycerol synthesis and breakdown, nutrient sensing and signal integration, and interactions with other organelles. Here we review the mechanisms that regulate the composition of the LD proteome, such as pathways that mediate selective and bulk LD protein degradation and potential connections between LDs and cellular protein quality control.
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Affiliation(s)
- Melissa A Roberts
- Department of Molecular and Cell Biology and Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720, USA;
| | - James A Olzmann
- Department of Molecular and Cell Biology and Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720, USA; .,Chan Zuckerberg Biohub, San Francisco, California 94158, USA
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11
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Chen HK, Rosset SL, Wang LH, Chen CS. The characteristics of host lipid body biogenesis during coral-dinoflagellate endosymbiosis. PeerJ 2021; 9:e11652. [PMID: 34221732 PMCID: PMC8234918 DOI: 10.7717/peerj.11652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 05/31/2021] [Indexed: 11/25/2022] Open
Abstract
Intracellular lipid body (LB) biogenesis depends on the symbiosis between coral hosts and their Symbiodinaceae. Therefore, understanding the mechanism(s) behind LB biosynthesis in corals can portentially elucide the drivers of cellular regulation during endosymbiosis. This study assessed LB formation in the gastrodermal tissue layer of the hermatypic coral Euphyllia glabrescens. Diel rhythmicity in LB size and distribution was observed; solar irradiation onset at sunrise initiated an increase in LB formation, which continued throughout the day and peaked after sunset at 18:00. The LBs migrated from the area near the mesoglea to the gastrodermal cell border near the coelenteron. Micro-LB biogenesis occurred in the endoplasmic reticulum (ER) of the host gastrodermal cells. A transcriptomic analysis of genes related to lipogenesis indicated that binding immunoglobulin protein (BiP) plays a key role in metabolic signaling pathways. The diel rhythmicity of LB biogenesis was correlated with ER-localized BiP expression. BiP expression peaked during the period with the largest increase in LB formation, thereby indicating that the chaperoning reaction of abnormal protein folding inside the host ER is likely involved in LB biosynthesis. These findings suggest that the host ER, central to LB formation, potentially facilitates the regulation of endosymbiosis between coral hosts and Symbiodiniaceae.
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Affiliation(s)
- Hung-Kai Chen
- National Museum of Marine Biology and Aquarium, Pingtung, Taiwan
| | - Sabrina L Rosset
- National Museum of Marine Biology and Aquarium, Pingtung, Taiwan
| | - Li-Hsueh Wang
- National Museum of Marine Biology and Aquarium, Pingtung, Taiwan.,Graduate Institute of Marine Biology, National Dong-Hwa University, Pingtung, Taiwan
| | - Chii-Shiarng Chen
- National Museum of Marine Biology and Aquarium, Pingtung, Taiwan.,Graduate Institute of Marine Biology, National Dong-Hwa University, Pingtung, Taiwan.,Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
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12
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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: 2.3] [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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13
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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: 1.3] [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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14
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Disorders of FZ-CRD; insights towards FZ-CRD folding and therapeutic landscape. Mol Med 2019; 26:4. [PMID: 31892318 PMCID: PMC6938638 DOI: 10.1186/s10020-019-0129-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Accepted: 12/13/2019] [Indexed: 02/08/2023] Open
Abstract
The ER is hub for protein folding. Proteins that harbor a Frizzled cysteine-rich domain (FZ-CRD) possess 10 conserved cysteine motifs held by a unique disulfide bridge pattern which attains a correct fold in the ER. Little is known about implications of disease-causing missense mutations within FZ-CRD families. Mutations in FZ-CRD of Frizzled class receptor 4 (FZD4) and Muscle, skeletal, receptor tyrosine kinase (MuSK) and Receptor tyrosine kinase-like orphan receptor 2 (ROR2) cause Familial Exudative Vitreoretinopathy (FEVR), Congenital Myasthenic Syndrome (CMS), and Robinow Syndrome (RS) respectively. We highlight reported pathogenic inherited missense mutations in FZ-CRD of FZD4, MuSK and ROR2 which misfold, and traffic abnormally in the ER, with ER-associated degradation (ERAD) as a common pathogenic mechanism for disease. Our review shows that all studied FZ-CRD mutants of RS, FEVR and CMS result in misfolded proteins and/or partially misfolded proteins with an ERAD fate, thus we coin them as “disorders of FZ-CRD”. Abnormal trafficking was demonstrated in 17 of 29 mutants studied; 16 mutants were within and/or surrounding the FZ-CRD with two mutants distant from FZ-CRD. These ER-retained mutants were improperly N-glycosylated confirming ER-localization. FZD4 and MuSK mutants were tagged with polyubiquitin chains confirming targeting for proteasomal degradation. Investigating the cellular and molecular mechanisms of these mutations is important since misfolded protein and ER-targeted therapies are in development. The P344R-MuSK kinase mutant showed around 50% of its in-vitro autophosphorylation activity and P344R-MuSK increased two-fold on proteasome inhibition. M105T-FZD4, C204Y-FZD4, and P344R-MuSK mutants are thermosensitive and therefore, might benefit from extending the investigation to a larger number of chemical chaperones and/or proteasome inhibitors. Nonetheless, FZ-CRD ER-lipidation it less characterized in the literature and recent structural data sheds light on the importance of lipidation in protein glycosylation, proper folding, and ER trafficking. Current treatment strategies in-place for the conformational disease landscape is highlighted. From this review, we envision that disorders of FZ-CRD might be receptive to therapies that target FZ-CRD misfolding, regulation of fatty acids, and/or ER therapies; thus paving the way for a newly explored paradigm to treat different diseases with common defects.
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15
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Kamp DW. Mitigating Lung Fibrosis by Targeting Dysfunctional Alveolar Epithelial Cell Lipid Metabolism. Am J Respir Cell Mol Biol 2019; 59:139-140. [PMID: 29698616 DOI: 10.1165/rcmb.2018-0070ed] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- David W Kamp
- 1 Division of Pulmonary and Critical Care Medicine Northwestern University Feinberg School of Medicine Chicago, Illinois and.,2 Jesse Brown VA Medical Center Chicago, Illinois
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16
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Abstract
Lipid droplets are storage organelles at the centre of lipid and energy homeostasis. They have a unique architecture consisting of a hydrophobic core of neutral lipids, which is enclosed by a phospholipid monolayer that is decorated by a specific set of proteins. Originating from the endoplasmic reticulum, lipid droplets can associate with most other cellular organelles through membrane contact sites. It is becoming apparent that these contacts between lipid droplets and other organelles are highly dynamic and coupled to the cycles of lipid droplet expansion and shrinkage. Importantly, lipid droplet biogenesis and degradation, as well as their interactions with other organelles, are tightly coupled to cellular metabolism and are critical to buffer the levels of toxic lipid species. Thus, lipid droplets facilitate the coordination and communication between different organelles and act as vital hubs of cellular metabolism.
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Affiliation(s)
- James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California-Berkeley, Berkeley, CA, USA.
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
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17
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Volkmar N, Thezenas ML, Louie SM, Juszkiewicz S, Nomura DK, Hegde RS, Kessler BM, Christianson JC. The ER membrane protein complex promotes biogenesis of sterol-related enzymes maintaining cholesterol homeostasis. J Cell Sci 2019; 132:jcs.223453. [PMID: 30578317 PMCID: PMC6362398 DOI: 10.1242/jcs.223453] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 12/03/2018] [Indexed: 12/24/2022] Open
Abstract
The eukaryotic endoplasmic reticulum (ER) membrane contains essential complexes that oversee protein biogenesis and lipid metabolism, impacting nearly all aspects of cell physiology. The ER membrane protein complex (EMC) is a newly described transmembrane domain (TMD) insertase linked with various phenotypes, but whose clients and cellular responsibilities remain incompletely understood. We report that EMC deficiency limits the cellular boundaries defining cholesterol tolerance, reflected by diminished viability with limiting or excessive extracellular cholesterol. Lipidomic and proteomic analyses revealed defective biogenesis and concomitant loss of the TMD-containing ER-resident enzymes sterol-O-acyltransferase 1 (SOAT1) and squalene synthase (SQS, also known as FDFT1), which serve strategic roles in the adaptation of cells to changes in cholesterol availability. Insertion of the weakly hydrophobic tail-anchor (TA) of SQS into the ER membrane by the EMC ensures sufficient flux through the sterol biosynthetic pathway while biogenesis of polytopic SOAT1 promoted by the EMC provides cells with the ability to store free cholesterol as inert cholesteryl esters. By facilitating insertion of TMDs that permit essential mammalian sterol-regulating enzymes to mature accurately, the EMC is an important biogenic determinant of cellular robustness to fluctuations in cholesterol availability. This article has an associated First Person interview with the first author of the paper. Highlighted Article: The ER membrane protein complex promotes biogenesis of key membrane-bound enzymes responsible for regulation of cholesterol biosynthesis and storage, an important determinant of mammalian cell viability.
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Affiliation(s)
- Norbert Volkmar
- Ludwig Institute for Cancer Research, University of Oxford, ORCRB, Headington, Oxford, OX3 7DQ, UK
| | - Maria-Laetitia Thezenas
- Target Discovery Institute (TDI) Mass Spectrometry Laboratory, Nuffield Department of Medicine, University of Oxford, Headington, Oxford, OX3 7DQ, UK
| | - Sharon M Louie
- Dept. of Chemistry, Molecular and Cell Biology, and Nutritional Sciences and Toxicology, University of California-Berkeley, Berkeley, CA, 94720, USA
| | - Szymon Juszkiewicz
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Daniel K Nomura
- Dept. of Chemistry, Molecular and Cell Biology, and Nutritional Sciences and Toxicology, University of California-Berkeley, Berkeley, CA, 94720, USA
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Benedikt M Kessler
- Target Discovery Institute (TDI) Mass Spectrometry Laboratory, Nuffield Department of Medicine, University of Oxford, Headington, Oxford, OX3 7DQ, UK
| | - John C Christianson
- Ludwig Institute for Cancer Research, University of Oxford, ORCRB, Headington, Oxford, OX3 7DQ, UK .,Oxford Centre for Translational Myeloma Research, NDORMS, University of Oxford, Botnar Research Centre, Headington, Oxford, OX3 7LD, UK
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18
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Babele PK, Thakre PK, Kumawat R, Tomar RS. Zinc oxide nanoparticles induce toxicity by affecting cell wall integrity pathway, mitochondrial function and lipid homeostasis in Saccharomyces cerevisiae. CHEMOSPHERE 2018; 213:65-75. [PMID: 30212720 DOI: 10.1016/j.chemosphere.2018.09.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 07/29/2018] [Accepted: 09/04/2018] [Indexed: 05/27/2023]
Abstract
Growing numbers of nanotoxicity research demonstrating that mechanical damage and oxidative stress are potential modes of nanoparticles (NPs) induced toxicity. However, the underlying mechanisms by which NPs interact with the eukaryotic cell and affect their physiological and metabolic functions are not fully known. We investigated the toxic effects of zinc oxide nanoparticles (ZnO-NPs) on budding yeast, Saccharomyces cerevisiae and elucidated the underlying mechanism. We observed cell wall damage and accumulation of reactive oxygen species (ROS) leading to cell death upon ZnO-NPs exposure. We detected a significant change in the cellular distribution of lipid biosynthetic enzymes (Fas1 and Fas2). Furthermore, exposure of ZnO-NPs altered the architecture of endoplasmic reticulum (ER) and mitochondria as well as ER-mitochondria encounter structure (ERMES) complex causing cellular toxicity due to lipid disequilibrium and proteostasis. We also observed significant changes in heat shock and unfolded protein responses, monitored by Hsp104-GFP localization and cytosolic Hac1 splicing respectively. Moreover, we observed activation of MAP kinases of CWI (Mpk1) and HOG (Hog1) pathways upon exposure to ZnO-NPs. Transcript level analyses showed induction of chitin synthesis and redox homeostasis genes. Finally, we observed induction in lipid droplets (LDs) formation, distorted vacuolar morphology and induction of autophagy as monitored by localization of Atg8p. However, we did not observe any significant change in epigenetic marks, examined by western blotting. Altogether, we provide evidence that exposure of ZnO-NPs results in cell death by affecting cell wall integrity and ER homeostasis as well as accumulation of ROS and saturated free fatty acids.
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Affiliation(s)
- Piyoosh Kumar Babele
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Bhopal 462023, India
| | - Pilendra Kumar Thakre
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Bhopal 462023, India
| | - Ramesh Kumawat
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Bhopal 462023, India
| | - Raghuvir Singh Tomar
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Bhopal 462023, India.
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19
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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: 8.3] [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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20
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Romero F, Hong X, Shah D, Kallen CB, Rosas I, Guo Z, Schriner D, Barta J, Shaghaghi H, Hoek JB, Mesaros C, Choi AM, Snyder NW, Summer R. Lipid Synthesis Is Required to Resolve Endoplasmic Reticulum Stress and Limit Fibrotic Responses in the Lung. Am J Respir Cell Mol Biol 2018; 59:225-236. [PMID: 29465261 PMCID: PMC6096342 DOI: 10.1165/rcmb.2017-0340oc] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 02/20/2018] [Indexed: 01/27/2023] Open
Abstract
Endoplasmic reticulum (ER) stress is evident in the alveolar epithelium of humans and mice with pulmonary fibrosis, but neither the mechanisms causing ER stress nor the contribution of ER stress to fibrosis is understood. A well-recognized adaptive response to ER stress is that affected cells induce lipid synthesis; however, we recently reported that lipid synthesis was downregulated in the alveolar epithelium in pulmonary fibrosis. In the present study, we sought to determine whether lipid synthesis is needed to resolve ER stress and limit fibrotic remodeling in the lung. Pharmacologic and genetic manipulations were performed to assess whether lipid production is required for resolving ER stress and limiting fibrotic responses in cultured alveolar epithelial cells and whole-lung tissues. Concentrations of ER stress markers and lipid synthesis enzymes were also measured in control and idiopathic pulmonary fibrosis lung tissues. We found that chemical agents that induce ER stress (tunicamycin or thapsigargin) enhanced lipid production in cultured alveolar epithelial cells and in the mouse lung. Moreover, lipid production was found to be dependent on the enzyme stearoyl-coenzyme A desaturase 1, and when pharmacologically inhibited, ER stress persisted and lung fibrosis ensued. Conversely, lipid production was reduced in mouse and human fibrotic lung, despite there being an increase in the magnitude of ER stress. Furthermore, augmenting lipid production effectively reduced ER stress and mitigated fibrotic remodeling in the mouse lung after exposure to silica. Augmenting lipid production reduces ER stress and attenuates fibrotic remodeling in the mouse lung, suggesting that similar approaches might be effective for treating human fibrotic lung diseases.
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Affiliation(s)
- Freddy Romero
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
| | - Xu Hong
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
- Medical Research Center, North China University of Science and Technology, Tangshan, China
| | - Dilip Shah
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
| | | | - Ivan Rosas
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women’s Hospital, Boston, Massachusetts
| | - Zhi Guo
- Department of Pulmonary Diseases, Jinan Military General Hospital, Jinan, China
| | - DeLeila Schriner
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
| | - Julie Barta
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
| | - Hoora Shaghaghi
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
| | - Jan B. Hoek
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Clementina Mesaros
- University of Pennsylvania Superfund Research and Training Program (Penn SRP) Center and Center of Excellence in Environmental Toxicology, and
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Augustine M. Choi
- Joan and Sanford I. Weill Department of Medicine, New York-Presbyterian Hospital, Weill Cornell Medical College, New York, New York; and
| | - Nathaniel W. Snyder
- A. J. Drexel Autism Institute, Drexel University, Philadelphia, Pennsylvania
| | - Ross Summer
- Center for Translational Medicine
- Jane and Leonard Korman Lung Center
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21
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Huang EY, To M, Tran E, Dionisio LTA, Cho HJ, Baney KLM, Pataki CI, Olzmann JA. A VCP inhibitor substrate trapping approach (VISTA) enables proteomic profiling of endogenous ERAD substrates. Mol Biol Cell 2018. [PMID: 29514927 PMCID: PMC5921570 DOI: 10.1091/mbc.e17-08-0514] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A new substrate trapping strategy that couples VCP inhibition and quantitative ubiquitin proteomics identifies endogenous ERAD substrates, expanding the available toolbox of strategies for global analysis of the ERAD substrate landscape. Endoplasmic reticulum (ER)–associated degradation (ERAD) mediates the proteasomal clearance of proteins from the early secretory pathway. In this process, ubiquitinated substrates are extracted from membrane-embedded dislocation complexes by the AAA ATPase VCP and targeted to the cytosolic 26S proteasome. In addition to its well-established role in the degradation of misfolded proteins, ERAD also regulates the abundance of key proteins such as enzymes involved in cholesterol synthesis. However, due to the lack of generalizable methods, our understanding of the scope of proteins targeted by ERAD remains limited. To overcome this obstacle, we developed a VCP inhibitor substrate trapping approach (VISTA) to identify endogenous ERAD substrates. VISTA exploits the small-molecule VCP inhibitor CB5083 to trap ERAD substrates in a membrane-associated, ubiquitinated form. This strategy, coupled with quantitative ubiquitin proteomics, identified previously validated (e.g., ApoB100, Insig2, and DHCR7) and novel (e.g., SCD1 and RNF5) ERAD substrates in cultured human hepatocellular carcinoma cells. Moreover, our results indicate that RNF5 autoubiquitination on multiple lysine residues targets it for ubiquitin and VCP-dependent clearance. Thus, VISTA provides a generalizable discovery method that expands the available toolbox of strategies to elucidate the ERAD substrate landscape.
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Affiliation(s)
- Edmond Y Huang
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
| | - Milton To
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
| | - Erica Tran
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
| | - Lorraine T Ador Dionisio
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
| | - Hyejin J Cho
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
| | - Katherine L M Baney
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
| | - Camille I Pataki
- Biomedical Informatics Program, Stanford University, Stanford, CA 94305
| | - James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720
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22
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Bersuker K, Peterson CWH, To M, Sahl SJ, Savikhin V, Grossman EA, Nomura DK, Olzmann JA. A Proximity Labeling Strategy Provides Insights into the Composition and Dynamics of Lipid Droplet Proteomes. Dev Cell 2017; 44:97-112.e7. [PMID: 29275994 DOI: 10.1016/j.devcel.2017.11.020] [Citation(s) in RCA: 207] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 10/18/2017] [Accepted: 11/27/2017] [Indexed: 01/06/2023]
Abstract
Lipid droplet (LD) functions are regulated by a complement of integral and peripheral proteins that associate with the bounding LD phospholipid monolayer. Defining the composition of the LD proteome has remained a challenge due to the presence of contaminating proteins in LD-enriched buoyant fractions. To overcome this limitation, we developed a proximity labeling strategy that exploits LD-targeted APEX2 to biotinylate LD proteins in living cells. Application of this approach to two different cell types identified the vast majority of previously validated LD proteins, excluded common contaminating proteins, and revealed new LD proteins. Moreover, quantitative analysis of LD proteome dynamics uncovered a role for endoplasmic reticulum-associated degradation in controlling the composition of the LD proteome. These data provide an important resource for future LD studies and demonstrate the utility of proximity labeling to study the regulation of LD proteomes.
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Affiliation(s)
- Kirill Bersuker
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Clark W H Peterson
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Milton To
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Steffen J Sahl
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Victoria Savikhin
- SLAC National Accelerator Center, SSRL, Menlo Park, CA 94025, USA; Stanford Electrical Engineering Department, Stanford University, Stanford, CA 94305, USA
| | - Elizabeth A Grossman
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Daniel K Nomura
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA; Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA.
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23
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DGAT1-Dependent Lipid Droplet Biogenesis Protects Mitochondrial Function during Starvation-Induced Autophagy. Dev Cell 2017; 42:9-21.e5. [PMID: 28697336 DOI: 10.1016/j.devcel.2017.06.003] [Citation(s) in RCA: 323] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 04/25/2017] [Accepted: 06/02/2017] [Indexed: 01/22/2023]
Abstract
Lipid droplets (LDs) provide an "on-demand" source of fatty acids (FAs) that can be mobilized in response to fluctuations in nutrient abundance. Surprisingly, the amount of LDs increases during prolonged periods of nutrient deprivation. Why cells store FAs in LDs during an energy crisis is unknown. Our data demonstrate that mTORC1-regulated autophagy is necessary and sufficient for starvation-induced LD biogenesis. The ER-resident diacylglycerol acyltransferase 1 (DGAT1) selectively channels autophagy-liberated FAs into new, clustered LDs that are in close proximity to mitochondria and are lipolytically degraded. However, LDs are not required for FA delivery to mitochondria but instead function to prevent acylcarnitine accumulation and lipotoxic dysregulation of mitochondria. Our data support a model in which LDs provide a lipid buffering system that sequesters FAs released during the autophagic degradation of membranous organelles, reducing lipotoxicity. These findings reveal an unrecognized aspect of the cellular adaptive response to starvation, mediated by LDs.
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24
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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: 331] [Impact Index Per Article: 47.3] [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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25
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Bersuker K, Olzmann JA. Establishing the lipid droplet proteome: Mechanisms of lipid droplet protein targeting and degradation. Biochim Biophys Acta Mol Cell Biol Lipids 2017. [PMID: 28627435 DOI: 10.1016/j.bbalip.2017.06.006] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are ubiquitous, endoplasmic reticulum (ER)-derived organelles that mediate the sequestration of neutral lipids (e.g. triacylglycerol and sterol esters), providing a dynamic cellular storage depot for rapid lipid mobilization in response to increased cellular demands. LDs have a unique ultrastructure, consisting of a core of neutral lipids encircled by a phospholipid monolayer that is decorated with integral and peripheral proteins. The LD proteome contains numerous lipid metabolic enzymes, regulatory scaffold proteins, proteins involved in LD clustering and fusion, and other proteins of unknown functions. The cellular role of LDs is inherently determined by the composition of its proteome and alteration of the LD protein coat provides a powerful mechanism to adapt LDs to fluctuating metabolic states. Here, we review the current understanding of the molecular mechanisms that govern LD protein targeting and degradation. 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)
- Kirill Bersuker
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA
| | - James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA.
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