1
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Wang X, Sun L. REEP5 mediates the function of CLEC5A to alleviate myocardial infarction by inhibiting endoplasmic reticulum stress-induced apoptosis. BMC Cardiovasc Disord 2024; 24:382. [PMID: 39044150 PMCID: PMC11265427 DOI: 10.1186/s12872-024-04018-3] [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: 12/01/2023] [Accepted: 06/27/2024] [Indexed: 07/25/2024] Open
Abstract
MI (myocardial infarction) often triggers severe heart failure and is one of the leading causes of death worldwide. Receptor expression-enhancing protein 5 (REEP5), a member of REEPs, acts as regulators of endoplasmic reticulum (ER) affecting cardiac functions. Based on GSE114695 profile data, REEP5 was decreased in the left ventricle of MI mice. However, its role and potential mechanism in MI remain to be investigated. In the present study, the mouse MI model was established by ligation of the left anterior descending artery. REEP5 expression was downregulated in the infarct penumbra area of MI mice. Next, its role during MI was explored by gain-of-function. Interestingly, REEP5 overexpression improved left ventricular function of mice with MI, accompanied with reduced infarct size. In cardiomyocytes, REEP5 overexpression inhibited ER stress, accompanied with repressive phosphorylation of PERK and IRE1α, and the decreased nuclear translocation of ATF6. Subsequently, REEP5 overexpression downregulated the levels of Chop and cleaved caspase-12, further alleviating ER stress-induced apoptosis, which was consistent with the in vivo results. Moreover, REEP5 was found to bind to C-type lectin member 5 A (CLEC5A), a protein that triggers cardiac dysfunction. CLEC5A, whose expression was elevated in hypoxia-induced cell models, led to cardiomyocyte apoptosis. Noteworthily, REEP5 overexpression markedly abolished the effects of CLEC5A on ER stress-induced apoptosis. Taken together, REEP5 mediated the function of CLEC5A to relieve MI via inhibiting ER stress-induced apoptosis in vivo and in vitro. REEP5 may be a promising target for treating MI.
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Affiliation(s)
- Xin Wang
- Department of Cardiology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, China
| | - Limin Sun
- Department of General Practice, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, China.
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2
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Sun S, Zhao G, Jia M, Jiang Q, Li S, Wang H, Li W, Wang Y, Bian X, Zhao YG, Huang X, Yang G, Cai H, Pastor-Pareja JC, Ge L, Zhang C, Hu J. Stay in touch with the endoplasmic reticulum. SCIENCE CHINA. LIFE SCIENCES 2024; 67:230-257. [PMID: 38212460 DOI: 10.1007/s11427-023-2443-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 08/28/2023] [Indexed: 01/13/2024]
Abstract
The endoplasmic reticulum (ER), which is composed of a continuous network of tubules and sheets, forms the most widely distributed membrane system in eukaryotic cells. As a result, it engages a variety of organelles by establishing membrane contact sites (MCSs). These contacts regulate organelle positioning and remodeling, including fusion and fission, facilitate precise lipid exchange, and couple vital signaling events. Here, we systematically review recent advances and converging themes on ER-involved organellar contact. The molecular basis, cellular influence, and potential physiological functions for ER/nuclear envelope contacts with mitochondria, Golgi, endosomes, lysosomes, lipid droplets, autophagosomes, and plasma membrane are summarized.
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Affiliation(s)
- Sha Sun
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Gan Zhao
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Mingkang Jia
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Qing Jiang
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Shulin Li
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Haibin Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wenjing Li
- Laboratory of Computational Biology & Machine Intelligence, School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunyun Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xin Bian
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China.
| | - Yan G Zhao
- Brain Research Center, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, 518055, China.
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Ge Yang
- Laboratory of Computational Biology & Machine Intelligence, School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Huaqing Cai
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Jose C Pastor-Pareja
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Institute of Neurosciences, Consejo Superior de Investigaciones Cientfflcas-Universidad Miguel Hernandez, San Juan de Alicante, 03550, Spain.
| | - Liang Ge
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
| | - Chuanmao Zhang
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China.
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China.
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3
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Deng Y, Zhu H, Wang Y, Dong Y, Du J, Yu Q, Li M. The Endoplasmic Reticulum-Plasma Membrane Tethering Protein Ice2 Controls Lipid Droplet Size via the Regulation of Phosphatidylcholine in Candida albicans. J Fungi (Basel) 2024; 10:87. [PMID: 38276033 PMCID: PMC10817647 DOI: 10.3390/jof10010087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/13/2024] [Accepted: 01/17/2024] [Indexed: 01/27/2024] Open
Abstract
Lipid droplets (LDs) are intracellular organelles that play important roles in cellular lipid metabolism; they change their sizes and numbers in response to both intracellular and extracellular signals. Changes in LD size reflect lipid synthesis and degradation and affect many cellular activities, including energy supply and membrane synthesis. Here, we focused on the function of the endoplasmic reticulum-plasma membrane tethering protein Ice2 in LD dynamics in the fungal pathogen Candida albicans (C. albicans). Nile red staining and size quantification showed that the LD size increased in the ice2Δ/Δ mutant, indicating the critical role of Ice2 in the regulation of LD dynamics. A lipid content analysis further demonstrated that the mutant had lower phosphatidylcholine levels. As revealed with GFP labeling and fluorescence microscopy, the methyltransferase Cho2, which is involved in phosphatidylcholine synthesis, had poorer localization in the plasma membrane in the mutant than in the wild-type strain. Interestingly, the addition of the phosphatidylcholine precursor choline led to the recovery of normal-sized LDs in the mutant. These results indicated that Ice2 regulates LD size by controlling intracellular phosphatidylcholine levels and that endoplasmic reticulum-plasma membrane tethering proteins play a role in lipid metabolism regulation in C. albicans. This study provides significant findings for further investigation of the lipid metabolism in fungi.
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Affiliation(s)
| | | | | | | | | | | | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China; (Y.D.); (H.Z.); (Y.W.); (Y.D.); (J.D.)
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4
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Zhang C, Ye M, Melikov K, Yang D, Dias do Vale G, McDonald J, Eckert K, Lin MJ, Zeng X. CLSTN3B enhances adipocyte lipid droplet structure and function via endoplasmic reticulum contact. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.20.576491. [PMID: 38293096 PMCID: PMC10827225 DOI: 10.1101/2024.01.20.576491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Interorganelle contacts facilitate material exchanges and sustain the structural and functional integrity of organelles. Lipid droplets (LDs) of adipocytes are responsible for energy storage and mobilization responding to body needs. LD biogenesis defects compromise the lipid-storing capacity of adipocytes, resulting in ectopic lipid deposition and metabolic disorders, yet how the uniquely large LDs in adipocytes attain structural and functional maturation is incompletely understood. Here we show that the mammalian adipocyte-specific protein CLSTN3B is crucial for adipocyte LD maturation. CLSTN3B employs an arginine-rich segment to promote extensive contact and hemifusion-like structure formation between the endoplasmic reticulum (ER) and LD, allowing ER-to-LD phospholipid diffusion during LD expansion. CLSTN3B ablation results in reduced LD surface phospholipid density, increased turnover of LD-surface proteins, and impaired LD functions. Our results establish the central role of CLSTN3B in the adipocyte-specific LD maturation pathway that enhances lipid storage and maintenance of metabolic health under caloric overload.
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Affiliation(s)
- Chuanhai Zhang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX
| | - Mengchen Ye
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA
| | - Kamran Melikov
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
| | - Dengbao Yang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX
| | | | - Jeffrey McDonald
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX
| | - Kaitlyn Eckert
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX
| | - Mei-Jung Lin
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX
| | - Xing Zeng
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX
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5
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Kumari RM, Khatri A, Chaudhary R, Choudhary V. Concept of lipid droplet biogenesis. Eur J Cell Biol 2023; 102:151362. [PMID: 37742390 PMCID: PMC7615795 DOI: 10.1016/j.ejcb.2023.151362] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/26/2023] Open
Abstract
Lipid droplets (LD) are functionally conserved fat storage organelles found in all cell types. LDs have a unique structure comprising of a hydrophobic core of neutral lipids (fat), triacylglycerol (TAG) and cholesterol esters (CE) surrounded by a phospholipid monolayer. LD surface is decorated by a multitude of proteins and enzymes rendering this compartment functional. Accumulating evidence suggests that LDs originate from discrete ER-subdomains, demarcated by the lipodystrophy protein seipin, however, the mechanisms of which are not well understood. LD biogenesis factors together with biophysical properties of the ER membrane orchestrate spatiotemporal regulation of LD nucleation and growth at specific ER subdomains in response to metabolic cues. Defects in LD formation manifests in several human pathologies, including obesity, lipodystrophy, ectopic fat accumulation, and insulin resistance. Here, we review recent advances in understanding the molecular events during initial stages of eukaryotic LD assembly and discuss the critical role of factors that ensure fidelity of this process.
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Affiliation(s)
- R Mankamna Kumari
- Lipid Metabolism Laboratory, Department of Biotechnology, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - Amit Khatri
- Lipid Metabolism Laboratory, Department of Biotechnology, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - Ritika Chaudhary
- Lipid Metabolism Laboratory, Department of Biotechnology, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - Vineet Choudhary
- Lipid Metabolism Laboratory, Department of Biotechnology, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India.
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6
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Prado LG, Camara NOS, Barbosa AS. Cell lipid biology in infections: an overview. Front Cell Infect Microbiol 2023; 13:1148383. [PMID: 37868347 PMCID: PMC10587689 DOI: 10.3389/fcimb.2023.1148383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 09/22/2023] [Indexed: 10/24/2023] Open
Abstract
Lipids are a big family of molecules with a vast number of functions in the cell membranes, within the cytoplasm, and extracellularly. Lipid droplets (LDs) are the most common storage organelles and are present in almost every tissue type in the body. They also have structural functions serving as building blocks of cellular membranes and may be precursors of other molecules such as hormones, and lipoproteins, and as messengers in signal transduction. Fatty acids (FAs), such as sterol esters and triacylglycerols, are stored in LDs and are used in β-oxidation as fuel for tricarboxylic acid cycle (TCA) and adenosine triphosphate (ATP) generation. FA uptake and entrance in the cytoplasm are mediated by membrane receptors. After a cytoplasmic round of α- and β-oxidation, FAs are guided into the mitochondrial matrix by the L-carnitine shuttle system, where they are fully metabolized, and enter the TCA cycle. Pathogen infections may lead to impaired lipid metabolism, usage of membrane phospholipids, and LD accumulation in the cytoplasm of infected cells. Otherwise, bacterial pathogens may use lipid metabolism as a carbon source, thus altering the reactions and leading to cellular and organelles malfunctioning. This review aims to describe cellular lipid metabolism and alterations that occur upon infections.
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Affiliation(s)
- Luan Gavião Prado
- Laboratório de Bacteriologia, Instituto Butantan, São Paulo, Brazil
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Niels Olsen Saraiva Camara
- Laboratório de Imunobiologia de Transplantes, Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
- Disciplina de Nefrologia, Departamento de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
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7
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Nenadic A, Zaman MF, Johansen J, Volpiana MW, Beh CT. Increased Phospholipid Flux Bypasses Overlapping Essential Requirements for the Yeast Sac1p Phosphoinositide Phosphatase and ER-PM Membrane Contact Sites. J Biol Chem 2023; 299:105092. [PMID: 37507017 PMCID: PMC10470028 DOI: 10.1016/j.jbc.2023.105092] [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: 08/21/2022] [Revised: 07/13/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
In budding yeast cells, much of the inner surface of the plasma membrane (PM) is covered with the endoplasmic reticulum (ER). This association is mediated by seven ER membrane proteins that confer cortical ER-PM association at membrane contact sites (MCSs). Several of these membrane "tether" proteins are known to physically interact with the phosphoinositide phosphatase Sac1p. However, it is unclear how or if these interactions are necessary for their interdependent functions. We find that SAC1 inactivation in cells lacking the homologous synaptojanin-like genes INP52 and INP53 results in a significant increase in cortical ER-PM MCSs. We show in sac1Δ, sac1tsinp52Δ inp53Δ, or Δ-super-tether (Δ-s-tether) cells lacking all seven ER-PM tethering genes that phospholipid biosynthesis is disrupted and phosphoinositide distribution is altered. Furthermore, SAC1 deletion in Δ-s-tether cells results in lethality, indicating a functional overlap between SAC1 and ER-PM tethering genes. Transcriptomic profiling indicates that SAC1 inactivation in either Δ-s-tether or inp52Δ inp53Δ cells induces an ER membrane stress response and elicits phosphoinositide-dependent changes in expression of autophagy genes. In addition, by isolating high-copy suppressors that rescue sac1Δ Δ-s-tether lethality, we find that key phospholipid biosynthesis genes bypass the overlapping function of SAC1 and ER-PM tethers and that overexpression of the phosphatidylserine/phosphatidylinositol-4-phosphate transfer protein Osh6 also provides limited suppression. Combined with lipidomic analysis and determinations of intracellular phospholipid distributions, these results suggest that Sac1p and ER phospholipid flux controls lipid distribution to drive Osh6p-dependent phosphatidylserine/phosphatidylinositol-4-phosphate counter-exchange at ER-PM MCSs.
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Affiliation(s)
- Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Mohammad F Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jesper Johansen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Matthew W Volpiana
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada; Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada.
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8
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Greenwood BL, Luo Z, Ahmed T, Huang D, Stuart DT. Saccharomyces cerevisiae Δ9-desaturase Ole1 forms a supercomplex with Slc1 and Dga1. J Biol Chem 2023:104882. [PMID: 37269945 PMCID: PMC10302205 DOI: 10.1016/j.jbc.2023.104882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Revised: 05/04/2023] [Accepted: 05/07/2023] [Indexed: 06/05/2023] Open
Abstract
Biosynthesis of the various lipid species that compose cellular membranes and lipid droplets depends on the activity of multiple enzymes functioning in coordinated pathways. The flux of intermediates through lipid biosynthetic pathways is regulated to respond to nutritional and environmental demands placed on the cell necessitating that there be extensive flexibility in pathway activity and organization. This flexibility can in part be achieved through the organization of biosynthetic enzymes into metabolon supercomplexes. However, the composition and organization of such supercomplexes remains unclear. Here, we identified protein-protein interactions between acyltransferases Sct1, Gpt2, Slc1, Dga1 and the Δ9 acyl-CoA desaturase Ole1 in Saccharomyces cerevisiae. We further determined that a subset of these acyltransferases interact with each other without Ole1 acting as a scaffold. We show that truncated versions of Dga1 lacking the carboxyl-terminal 20 amino acid residues are non-functional and unable to bind Ole1. Furthermore, charged-to-alanine scanning mutagenesis revealed that a cluster of charged residues near the carboxyl-terminus were required for the interaction with Ole1. Mutation of these charged residues disrupted the interaction between Dga1 and Ole1, but allowed Dga1 to retain catalytic activity and to induce lipid droplet formation. These data support the formation of a complex of acyltransferases involved in lipid biosynthesis that interacts with Ole1, the sole acyl-CoA desaturase in S. cerevisiae, that can channel unsaturated acyl-chains toward phospholipid or triacylglycerol synthesis. This desaturasome complex may provide the architecture that allows for the necessary flux of de novo synthesized unsaturated acyl-CoA to phospholipid or triacylglycerol synthesis as demanded by cellular requirements.
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Affiliation(s)
- Brianna L Greenwood
- Department of Biochemistry, 561 Medical Sciences Building, University of Alberta, Edmonton AB, T6G 2R3, Canada
| | - Zijun Luo
- Department of Biochemistry, 561 Medical Sciences Building, University of Alberta, Edmonton AB, T6G 2R3, Canada
| | - Tareq Ahmed
- Department of Biochemistry, 561 Medical Sciences Building, University of Alberta, Edmonton AB, T6G 2R3, Canada
| | - Daniel Huang
- Department of Biochemistry, 561 Medical Sciences Building, University of Alberta, Edmonton AB, T6G 2R3, Canada
| | - David T Stuart
- Department of Biochemistry, 561 Medical Sciences Building, University of Alberta, Edmonton AB, T6G 2R3, Canada.
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9
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Li Z, Zou J, Chen X. In Response to Precision Medicine: Current Subcellular Targeting Strategies for Cancer Therapy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2209529. [PMID: 36445169 DOI: 10.1002/adma.202209529] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 11/08/2022] [Indexed: 05/26/2023]
Abstract
Emerging as a potent anticancer treatment, subcellular targeted cancer therapy has drawn increasing attention, bringing great opportunities for clinical application. Here, two targeting strategies for four main subcellular organelles (mitochondria, lysosome, endoplasmic reticulum, and nucleus), including molecule- and nanomaterial (inorganic nanoparticles, micelles, organic polymers, and others)-based targeted delivery or therapeutic strategies, are summarized. Phototherapy, chemotherapy, radiotherapy, immunotherapy, and "all-in-one" combination therapy are among the strategies covered in detail. Such materials are constructed based on the specific properties and relevant mechanisms of organelles, enabling the elimination of tumors by inducing dysfunction in the corresponding organelles or destroying specific structures. The challenges faced by organelle-targeting cancer therapies are also summarized. Looking forward, a paradigm for organelle-targeting therapy with enhanced therapeutic efficacy compared to current clinical approaches is envisioned.
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Affiliation(s)
- Zheng Li
- Departments of Diagnostic Radiology, Surgery, Chemical and Biomolecular Engineering, and Biomedical Engineering, Yong Loo Lin School of Medicine and Faculty of Engineering, National University of Singapore, Singapore, 119074, Singapore
- Nanomedicine Translational Research Program, NUS Center for Nanomedicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
| | - Jianhua Zou
- Departments of Diagnostic Radiology, Surgery, Chemical and Biomolecular Engineering, and Biomedical Engineering, Yong Loo Lin School of Medicine and Faculty of Engineering, National University of Singapore, Singapore, 119074, Singapore
- Nanomedicine Translational Research Program, NUS Center for Nanomedicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
| | - Xiaoyuan Chen
- Departments of Diagnostic Radiology, Surgery, Chemical and Biomolecular Engineering, and Biomedical Engineering, Yong Loo Lin School of Medicine and Faculty of Engineering, National University of Singapore, Singapore, 119074, Singapore
- Nanomedicine Translational Research Program, NUS Center for Nanomedicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
- Clinical Imaging Research Centre, Centre for Translational Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117599, Singapore
- Institute of Molecular and Cell Biology, Agency for Science, Technology, and Research (A*STAR), 61 Biopolis Drive, Proteos, Singapore, 138673, Singapore
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10
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Lu S, Dai Z, Cui Y, Kong DM. Recent Development of Advanced Fluorescent Molecular Probes for Organelle-Targeted Cell Imaging. BIOSENSORS 2023; 13:360. [PMID: 36979572 PMCID: PMC10046058 DOI: 10.3390/bios13030360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 02/10/2023] [Accepted: 02/20/2023] [Indexed: 06/18/2023]
Abstract
Fluorescent molecular probes are very powerful tools that have been generally applied in cell imaging in the research fields of biology, pathology, pharmacology, biochemistry, and medical science. In the last couple of decades, numerous molecular probes endowed with high specificity to particular organelles have been designed to illustrate intracellular images in more detail at the subcellular level. Nowadays, the development of cell biology has enabled the investigation process to go deeply into cells, even at the molecular level. Therefore, probes that can sketch a particular organelle's location while responding to certain parameters to evaluate intracellular bioprocesses are under urgent demand. It is significant to understand the basic ideas of organelle properties, as well as the vital substances related to each unique organelle, for the design of probes with high specificity and efficiency. In this review, we summarize representative multifunctional fluorescent molecular probes developed in the last decade. We focus on probes that can specially target nuclei, mitochondria, endoplasmic reticulums, and lysosomes. In each section, we first briefly introduce the significance and properties of different organelles. We then discuss how probes are designed to make them highly organelle-specific. Finally, we also consider how probes are constructed to endow them with additional functions to recognize particular physical/chemical signals of targeted organelles. Moreover, a perspective on the challenges in future applications of highly specific molecular probes in cell imaging is also proposed. We hope that this review can provide researchers with additional conceptual information about developing probes for cell imaging, assisting scientists interested in molecular biology, cell biology, and biochemistry to accelerate their scientific studies.
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Affiliation(s)
- Sha Lu
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Centre for Analytical Sciences, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Zhiqi Dai
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Centre for Analytical Sciences, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Yunxi Cui
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - De-Ming Kong
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Centre for Analytical Sciences, College of Chemistry, Nankai University, Tianjin 300071, China
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11
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Mishra S, Wang Z, Volk MJ, Zhao H. Design and application of a kinetic model of lipid metabolism in Saccharomyces cerevisiae. Metab Eng 2023; 75:12-18. [PMID: 36371031 DOI: 10.1016/j.ymben.2022.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 10/29/2022] [Accepted: 11/08/2022] [Indexed: 11/10/2022]
Abstract
Lipid biosynthesis plays a vital role in living cells and has been increasingly engineered to overproduce various lipid-based chemicals. However, owing to the tightly constrained and interconnected nature of lipid biosynthesis, both understanding and engineering of lipid metabolism remain challenging, even with the help of mathematical models. Here we report the development of a kinetic metabolic model of lipid metabolism in Saccharomyces cerevisiae that integrates fatty acid biosynthesis, glycerophospholipid metabolism, sphingolipid metabolism, storage lipids, lumped sterol synthesis, and the synthesis and transport of relevant target-chemicals, such as fatty acids and fatty alcohols. The model was trained on lipidomic data of a reference S. cerevisiae strain, single knockout mutants, and lipid overproduction strains reported in literature. The model was used to design mutants for fatty alcohol overproduction and the lipidomic analysis of the resultant mutant strains coupled with model-guided hypothesis led to discovery of a futile cycle in the triacylglycerol biosynthesis pathway. In addition, the model was used to explain successful and unsuccessful mutant designs in metabolic engineering literature. Thus, this kinetic model of lipid metabolism can not only enable the discovery of new phenomenon in lipid metabolism but also the engineering of mutant strains for overproduction of lipids.
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Affiliation(s)
- Shekhar Mishra
- Department of Chemical and Biomolecular Engineering, Department of Energy Center for Advanced Bioenergy and Bioproducts Innovation, Carl R. Woese Institute for Genomic Biology, USA
| | | | - Michael J Volk
- Department of Chemical and Biomolecular Engineering, Department of Energy Center for Advanced Bioenergy and Bioproducts Innovation, Carl R. Woese Institute for Genomic Biology, USA
| | - Huimin Zhao
- Department of Chemical and Biomolecular Engineering, Department of Energy Center for Advanced Bioenergy and Bioproducts Innovation, Carl R. Woese Institute for Genomic Biology, USA; Department of Biochemistry, USA; Departments of Chemistry and Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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12
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Chen G, Harwood JL, Lemieux MJ, Stone SJ, Weselake RJ. Acyl-CoA:diacylglycerol acyltransferase: Properties, physiological roles, metabolic engineering and intentional control. Prog Lipid Res 2022; 88:101181. [PMID: 35820474 DOI: 10.1016/j.plipres.2022.101181] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 05/31/2022] [Accepted: 07/04/2022] [Indexed: 12/15/2022]
Abstract
Acyl-CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the last reaction in the acyl-CoA-dependent biosynthesis of triacylglycerol (TAG). DGAT activity resides mainly in membrane-bound DGAT1 and DGAT2 in eukaryotes and bifunctional wax ester synthase-diacylglycerol acyltransferase (WSD) in bacteria, which are all membrane-bound proteins but exhibit no sequence homology to each other. Recent studies also identified other DGAT enzymes such as the soluble DGAT3 and diacylglycerol acetyltransferase (EaDAcT), as well as enzymes with DGAT activities including defective in cuticular ridges (DCR) and steryl and phytyl ester synthases (PESs). This review comprehensively discusses research advances on DGATs in prokaryotes and eukaryotes with a focus on their biochemical properties, physiological roles, and biotechnological and therapeutic applications. The review begins with a discussion of DGAT assay methods, followed by a systematic discussion of TAG biosynthesis and the properties and physiological role of DGATs. Thereafter, the review discusses the three-dimensional structure and insights into mechanism of action of human DGAT1, and the modeled DGAT1 from Brassica napus. The review then examines metabolic engineering strategies involving manipulation of DGAT, followed by a discussion of its therapeutic applications. DGAT in relation to improvement of livestock traits is also discussed along with DGATs in various other eukaryotic organisms.
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Affiliation(s)
- Guanqun Chen
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6H 2P5, Canada.
| | - John L Harwood
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, Membrane Protein Disease Research Group, Edmonton T6G 2H7, Canada
| | - Scot J Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
| | - Randall J Weselake
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6H 2P5, Canada
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13
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Miyata N, Ito T, Nakashima M, Fujii S, Kuge O. Mitochondrial phosphatidylethanolamine synthesis affects mitochondrial energy metabolism and quiescence entry through attenuation of Snf1/AMPK signaling in yeast. FASEB J 2022; 36:e22355. [PMID: 35639425 DOI: 10.1096/fj.202101600rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 05/04/2022] [Accepted: 05/06/2022] [Indexed: 11/11/2022]
Abstract
The Ups2-Mdm35 complex mediates intramitochondrial phosphatidylserine (PS) transport to facilitate mitochondrial phosphatidylethanolamine (PE) synthesis. In the present study, we found that ups2∆ yeast showed increased mitochondrial ATP production and enhanced quiescence (G0) entry in the post-diauxic shift phase. Transcriptomic and biochemical analyses revealed that the depletion of Ups2 leads to overactivation of the yeast AMPK homolog Snf1. Inactivation of Snf1 by depletion of an Snf1-activating kinase, Sak1 canceled the changes in mitochondrial ATP production and quiescence entry observed in ups2∆ cells. Furthermore, among the factors regulated by Snf1, upregulation of pyruvate carboxylase, Pyc1 and downregulation of acetyl-CoA carboxylase, Acc1, respectively, were sufficient to increase mitochondrial ATP production and quiescence entry. These results suggested that a normal PE synthesis mediated by Ups2-Mdm35 complex attenuates Snf1/AMPK activity, and that Snf1-mediated regulation of carbon metabolisms has great impacts on mitochondrial energy metabolism and quiescence entry. We also found that depletion of Ups2 together with the cell-cycle regulators Whi5 and Whi7, functional orthologs of the Rb1 tumor suppressor, caused a synthetic growth defect in yeast. Similarly, knockdown of PRELID3b, the human homolog of Ups2, decreased the viability of Rb1-deficient breast cancer cells, suggesting that PRELID3b is a potential target for cancer therapy.
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Affiliation(s)
- Non Miyata
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
| | - Takanori Ito
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
| | - Miyu Nakashima
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
| | - Satoru Fujii
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
| | - Osamu Kuge
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
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14
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Schneiter R, Choudhary V. Seipin collaborates with the ER membrane to control the sites of lipid droplet formation. Curr Opin Cell Biol 2022; 75:102070. [PMID: 35306312 PMCID: PMC7615794 DOI: 10.1016/j.ceb.2022.02.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 12/24/2022]
Abstract
Most cells store metabolic energy in lipid droplets (LDs). LDs are composed of a hydrophobic core, covered by a phospholipid monolayer, and functionalized by a specific set of proteins. Formation of LDs takes place in the endoplasmic reticulum (ER), where neutral lipid biosynthetic enzymes are located. Recent evidence indicate that this process is confined to specific ER subdomains, where proteins meet to initiate LD assembly. The lipodystrophy protein Seipin, is emerging as a major coordinator of LD biogenesis. Seipin forms a large oligomeric toroidal structure, which traps neutral lipids to promote LD nucleation. Here, we discuss the role of LD biogenesis factors that associate with Seipin to assemble functional LDs.
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Affiliation(s)
- Roger Schneiter
- University of Fribourg, Department of Biology, 1700, Fribourg, Switzerland.
| | - Vineet Choudhary
- All India Institute of Medical Sciences (AIIMS), Department of Biotechnology, New Delhi, 110029, India.
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15
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Chorlay A, Forêt L, Thiam AR. Origin of gradients in lipid density and surface tension between connected lipid droplet and bilayer. Biophys J 2021; 120:5491-5503. [PMID: 34808099 DOI: 10.1016/j.bpj.2021.11.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/20/2021] [Accepted: 11/17/2021] [Indexed: 10/19/2022] Open
Abstract
We combined theory and experiments to depict physical parameters modulating the phospholipid (PL) density and tension equilibrium between a bilayer and an oil droplet in contiguity. This situation is encountered during a neutral lipid (NL) droplet formation in the endoplasmic reticulum. We set up macroscopic and microscopic models to uncover free parameters and the origin of molecular interactions controlling the PL densities of the droplet monolayer and the bilayer. The established physical laws and predictions agreed with experiments performed with droplet-embedded vesicles. We found that the droplet monolayer is always by a few percent (∼10%) less packed with PLs than the bilayer. Such a density gradient arises from PL-NL interactions on the droplet, which are lower than PL-PL trans interactions in the bilayer, i.e., interactions between PLs belonging to different leaflets of the bilayer. Finally, despite the pseudo-surface tension for the water/PL acyl chains in the bilayer being higher than the water/NL surface tension, the droplet monolayer always has a higher surface tension than the bilayer because of its lower PL density. Thus, a PL density gradient is mandatory to maintain the mechanical and thermodynamic equilibrium of the droplet-bilayer continuity. Our study sheds light on the origin of the molecular interactions responsible for the unique surface properties of lipid droplets compared with cellular bilayer membranes.
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Affiliation(s)
- Aymeric Chorlay
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France
| | - Lionel Forêt
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France.
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France.
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16
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Hello from the other side: Membrane contact of lipid droplets with other organelles and subsequent functional implications. Prog Lipid Res 2021; 85:101141. [PMID: 34793861 DOI: 10.1016/j.plipres.2021.101141] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/10/2021] [Accepted: 11/10/2021] [Indexed: 02/06/2023]
Abstract
Lipid droplets (LDs) are ubiquitous organelles that play crucial roles in response to physiological and environmental cues. The identification of several neutral lipid synthesizing and regulatory protein complexes have propelled significant advance on the mechanisms of LD biogenesis in the endoplasmic reticulum (ER). Increasing evidence suggests that distinct proteins and regulatory factors, which localize to membrane contact sites (MCS), are involved not only in interorganellar lipid exchange and transport, but also function in other important cellular processes, including autophagy, mitochondrial dynamics and inheritance, ion signaling and inter-regulation of these MCS. More and more tethers and molecular determinants are associated to MCS and to a diversity of cellular and pathophysiological processes, demonstrating the dynamics and importance of these junctions in health and disease. The conjugation of lipids with proteins in supramolecular complexes is known to be paramount for many biological processes, namely membrane biosynthesis, cell homeostasis, regulation of organelle division and biogenesis, and cell growth. Ultimately, this physical organization allows the contact sites to function as crucial metabolic hubs that control the occurrence of chemical reactions. This leads to biochemical and metabolite compartmentalization for the purposes of energetic efficiency and cellular homeostasis. In this review, we will focus on the structural and functional aspects of LD-organelle interactions and how they ensure signaling exchange and metabolites transfer between organelles.
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17
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Papagiannidis D, Bircham PW, Lüchtenborg C, Pajonk O, Ruffini G, Brügger B, Schuck S. Ice2 promotes ER membrane biogenesis in yeast by inhibiting the conserved lipin phosphatase complex. EMBO J 2021; 40:e107958. [PMID: 34617598 PMCID: PMC8591542 DOI: 10.15252/embj.2021107958] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 09/01/2021] [Accepted: 09/03/2021] [Indexed: 11/30/2022] Open
Abstract
Cells dynamically adapt organelle size to current physiological demand. Organelle growth requires membrane biogenesis and therefore needs to be coordinated with lipid metabolism. The endoplasmic reticulum (ER) can undergo massive expansion, but the underlying regulatory mechanisms are largely unclear. Here, we describe a genetic screen for factors involved in ER membrane expansion in budding yeast and identify the ER transmembrane protein Ice2 as a strong hit. We show that Ice2 promotes ER membrane biogenesis by opposing the phosphatidic acid phosphatase Pah1, called lipin in metazoa. Specifically, Ice2 inhibits the conserved Nem1‐Spo7 complex and thus suppresses the dephosphorylation and activation of Pah1. Furthermore, Ice2 cooperates with the transcriptional regulation of lipid synthesis genes and helps to maintain cell homeostasis during ER stress. These findings establish the control of the lipin phosphatase complex as an important mechanism for regulating ER membrane biogenesis.
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Affiliation(s)
- Dimitrios Papagiannidis
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Peter W Bircham
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany
| | | | - Oliver Pajonk
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Giulia Ruffini
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Britta Brügger
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Sebastian Schuck
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
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18
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Ajjaji D, Ben M'barek K, Boson B, Omrane M, Gassama-Diagne A, Blaud M, Penin F, Diaz E, Ducos B, Cosset FL, Thiam AR. Hepatitis C virus core protein uses triacylglycerols to fold onto the endoplasmic reticulum membrane. Traffic 2021; 23:63-80. [PMID: 34729868 DOI: 10.1111/tra.12825] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Revised: 10/16/2021] [Accepted: 11/01/2021] [Indexed: 12/12/2022]
Abstract
Lipid droplets (LDs) are involved in viral infections, but exactly how remains unclear. Here, we study the hepatitis C virus (HCV) whose core capsid protein binds to LDs but is also involved in the assembly of virions at the endoplasmic reticulum (ER) bilayer. We found that the amphipathic helix-containing domain of core, D2, senses triglycerides (TGs) rather than LDs per se. In the absence of LDs, D2 can bind to the ER membrane but only if TG molecules are present in the bilayer. Accordingly, the pharmacological inhibition of the diacylglycerol O-acyltransferase enzymes, mediating TG synthesis in the ER, inhibits D2 association with the bilayer. We found that TG molecules enable D2 to fold into alpha helices. Sequence analysis reveals that D2 resembles the apoE lipid-binding region. Our data support that TG in LDs promotes the folding of core, which subsequently relocalizes to contiguous ER regions. During this motion, core may carry TG molecules to these regions where HCV lipoviroparticles likely assemble. Consistent with this model, the inhibition of Arf1/COPI, which decreases LD surface accessibility to proteins and ER-LD material exchange, severely impedes the assembly of virions. Altogether, our data uncover a critical function of TG in the folding of core and HCV replication and reveals, more broadly, how TG accumulation in the ER may provoke the binding of soluble amphipathic helix-containing proteins to the ER bilayer.
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Affiliation(s)
- Dalila Ajjaji
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, Paris, 75005, France
| | - Kalthoum Ben M'barek
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, Paris, 75005, France
| | - Bertrand Boson
- CIRI-Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, Lyon, France
| | - Mohyeddine Omrane
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, Paris, 75005, France
| | - Ama Gassama-Diagne
- INSERM, Unité 1193, Villejuif, France.,Université Paris-Sud, UMR-S 1193, Villejuif, France
| | - Magali Blaud
- Université de Paris, CiTCoM, CNRS, Paris, France
| | - François Penin
- Institut de Biologie et Chimie des Protéines, Bases Moléculaires et Structurales des Systèmes Infectieux, UMR 5086, CNRS, Labex Ecofect, University of Lyon, Lyon, France
| | - Elise Diaz
- High Throughput qPCR Core Facility of the ENS, IBENS, PSL Research University, Paris, France
| | - Bertrand Ducos
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, Paris, 75005, France.,High Throughput qPCR Core Facility of the ENS, IBENS, PSL Research University, Paris, France
| | - François-Loïc Cosset
- CIRI-Centre International de Recherche en Infectiologie, Univ Lyon, Université Claude Bernard Lyon 1, Inserm, U1111, CNRS, UMR5308, ENS Lyon, Lyon, France
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, Paris, 75005, France
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19
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Adhikari S, Moscatelli J, Puchner EM. Quantitative live-cell PALM reveals nanoscopic Faa4 redistributions and dynamics on lipid droplets during metabolic transitions of yeast. Mol Biol Cell 2021; 32:1565-1578. [PMID: 34161133 PMCID: PMC8351750 DOI: 10.1091/mbc.e20-11-0695] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Lipid droplets (LDs) are dynamic organelles for lipid storage and homeostasis. Cells respond to metabolic changes by regulating the spatial distribution of LDs and enzymes required for LD growth and turnover. The small size of LDs precludes the observation of their associated enzyme densities and dynamics with conventional fluorescence microscopy. Here we employ quantitative photo-activated localization microscopy to study the density of the fatty acid (FA) activating enzyme Faa4 on LDs in live yeast cells with single-molecule sensitivity and 30 nm resolution. During the log phase LDs colocalize with the endoplasmic reticulum (ER) where their emergence and expansion are mediated by the highest observed Faa4 densities. During transition to the stationary phase, LDs with a ∼2-fold increased surface area translocate to the vacuolar surface and lumen and exhibit a ∼2.5-fold increase in Faa4 density. The increased Faa4 density on LDs further suggests its role in LD expansion, is caused by its ∼5-fold increased expression level, and is specific to exogenous FA chain-lengths. When lipolysis is induced by refreshed medium, Faa4 shuttles through ER- and lipophagy to the vacuole, where it may activate FAs for membrane expansion and degrade Faa4 to reset its cellular abundance to levels in the log phase.
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Affiliation(s)
- Santosh Adhikari
- School of Physics and Astronomy, University of Minnesota, Twin Cities, Physics and Nanotechnology (PAN), Minneapolis, MN 55455
| | - Joe Moscatelli
- School of Physics and Astronomy, University of Minnesota, Twin Cities, Physics and Nanotechnology (PAN), Minneapolis, MN 55455
| | - Elias M Puchner
- School of Physics and Astronomy, University of Minnesota, Twin Cities, Physics and Nanotechnology (PAN), Minneapolis, MN 55455
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20
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Khaddaj R, Mari M, Cottier S, Reggiori F, Schneiter R. The surface of lipid droplets constitutes a barrier for endoplasmic reticulum-resident integral membrane proteins. J Cell Sci 2021; 135:268334. [PMID: 34028531 DOI: 10.1242/jcs.256206] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 04/14/2021] [Indexed: 12/12/2022] Open
Abstract
Lipid droplets (LDs) are globular subcellular structures that store neutral lipids. LDs are closely associated with the endoplasmic reticulum (ER) and are limited by a phospholipid monolayer harboring a specific set of proteins. Most of these proteins associate with LDs through either an amphipathic helix or a membrane-embedded hairpin motif. Here, we address the question of whether integral membrane proteins can localize to the surface of LDs. To test this, we fused perilipin 3 (PLIN3), a mammalian LD-targeted protein, to ER-resident proteins. The resulting fusion proteins localized to the periphery of LDs in both yeast and mammalian cells. This peripheral LD localization of the fusion proteins, however, was due to a redistribution of the ER around LDs, as revealed by bimolecular fluorescence complementation between ER- and LD-localized partners. A LD-tethering function of PLIN3-containing membrane proteins was confirmed by fusing PLIN3 to the cytoplasmic domain of an outer mitochondrial membrane protein, OM14. Expression of OM14-PLIN3 induced a close apposition between LDs and mitochondria. These data indicate that the ER-LD junction constitutes a barrier for ER-resident integral membrane proteins.
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Affiliation(s)
- Rasha Khaddaj
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Stéphanie Cottier
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Roger Schneiter
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
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21
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Alli-Balogun GO, Levine TP. Fungal Ice2p is in the same superfamily as SERINCs, restriction factors for HIV and other viruses. Proteins 2021; 89:1240-1250. [PMID: 33982326 DOI: 10.1002/prot.26145] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/10/2021] [Indexed: 12/13/2022]
Abstract
Ice2p is an integral endoplasmic reticulum (ER) membrane protein in budding yeast S. cerevisiae named ICE because it is required for Inheritance of Cortical ER. Ice2p has also been reported to be involved in an ER metabolic branch-point that regulates the flux of lipid either to be stored in lipid droplets or to be used as membrane components. Alternately, Ice2p has been proposed to act as a tether that physically bridges the ER at contact sites with both lipid droplets and the plasma membrane via a long loop on the protein's cytoplasmic face that contains multiple predicted amphipathic helices. Here we carried out a bioinformatic analysis to increase understanding of Ice2p. First, regarding topology, we found that diverse members of the fungal Ice2 family have 10 transmembrane helices (TMHs), which places the long loop on the exofacial face of Ice2p, where it cannot form inter-organelle bridges. Second, we identified Ice2p as a full-length homolog of SERINC (serine incorporator), a family of proteins with 10 TMHs found universally in eukaryotes. Since SERINCs are potent restriction factors for HIV and other viruses, study of Ice2p may reveal functions or mechanisms that shed light on viral restriction by SERINCs.
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Affiliation(s)
| | - Tim P Levine
- UCL Institute of Ophthalmology, University College London, London, UK
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22
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Yocum HC, Pham A, Da Silva NA. Successful Enzyme Colocalization Strategies in Yeast for Increased Synthesis of Non-native Products. Front Bioeng Biotechnol 2021; 9:606795. [PMID: 33634084 PMCID: PMC7901933 DOI: 10.3389/fbioe.2021.606795] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 01/11/2021] [Indexed: 11/13/2022] Open
Abstract
Yeast cell factories, particularly Saccharomyces cerevisiae, have proven valuable for the synthesis of non-native compounds, ranging from commodity chemicals to complex natural products. One significant challenge has been ensuring sufficient carbon flux to the desired product. Traditionally, this has been addressed by strategies involving "pushing" and "pulling" the carbon flux toward the products by overexpression while "blocking" competing pathways via downregulation or gene deletion. Colocalization of enzymes is an alternate and complementary metabolic engineering strategy to control flux and increase pathway efficiency toward the synthesis of non-native products. Spatially controlling the pathway enzymes of interest, and thus positioning them in close proximity, increases the likelihood of reaction along that pathway. This mini-review focuses on the recent developments and applications of colocalization strategies, including enzyme scaffolding, construction of synthetic organelles, and organelle targeting, in both S. cerevisiae and non-conventional yeast hosts. Challenges with these techniques and future directions will also be discussed.
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Affiliation(s)
- Hannah C Yocum
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, CA, United States
| | - Anhuy Pham
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, CA, United States
| | - Nancy A Da Silva
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, CA, United States
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23
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Muszewska A, Okrasińska A, Steczkiewicz K, Drgas O, Orłowska M, Perlińska-Lenart U, Aleksandrzak-Piekarczyk T, Szatraj K, Zielenkiewicz U, Piłsyk S, Malc E, Mieczkowski P, Kruszewska JS, Bernat P, Pawłowska J. Metabolic Potential, Ecology and Presence of Associated Bacteria Is Reflected in Genomic Diversity of Mucoromycotina. Front Microbiol 2021; 12:636986. [PMID: 33679672 PMCID: PMC7928374 DOI: 10.3389/fmicb.2021.636986] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 01/25/2021] [Indexed: 11/13/2022] Open
Abstract
Mucoromycotina are often considered mainly in pathogenic context but their biology remains understudied. We describe the genomes of six Mucoromycotina fungi representing distant saprotrophic lineages within the subphylum (i.e., Umbelopsidales and Mucorales). We selected two Umbelopsis isolates from soil (i.e., U. isabellina, U. vinacea), two soil-derived Mucor isolates (i.e., M. circinatus, M. plumbeus), and two Mucorales representatives with extended proteolytic activity (i.e., Thamnidium elegans and Mucor saturninus). We complement computational genome annotation with experimental characteristics of their digestive capabilities, cell wall carbohydrate composition, and extensive total lipid profiles. These traits inferred from genome composition, e.g., in terms of identified encoded enzymes, are in accordance with experimental results. Finally, we link the presence of associated bacteria with observed characteristics. Thamnidium elegans genome harbors an additional, complete genome of an associated bacterium classified to Paenibacillus sp. This fungus displays multiple altered traits compared to the remaining isolates, regardless of their evolutionary distance. For instance, it has expanded carbon assimilation capabilities, e.g., efficiently degrades carboxylic acids, and has a higher diacylglycerol:triacylglycerol ratio and skewed phospholipid composition which suggests a more rigid cellular membrane. The bacterium can complement the host enzymatic capabilities, alter the fungal metabolism, cell membrane composition but does not change the composition of the cell wall of the fungus. Comparison of early-diverging Umbelopsidales with evolutionary younger Mucorales points at several subtle differences particularly in their carbon source preferences and encoded carbohydrate repertoire. Nevertheless, all tested Mucoromycotina share features including the ability to produce 18:3 gamma-linoleic acid, use TAG as the storage lipid and have fucose as a cell wall component.
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Affiliation(s)
- Anna Muszewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Alicja Okrasińska
- Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Kamil Steczkiewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Olga Drgas
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Małgorzata Orłowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | | | | | - Katarzyna Szatraj
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Urszula Zielenkiewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Sebastian Piłsyk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Ewa Malc
- High Throughput Sequencing Facility of UNC, Chapel Hill, NC, United States
| | - Piotr Mieczkowski
- High Throughput Sequencing Facility of UNC, Chapel Hill, NC, United States
| | - Joanna S. Kruszewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Przemysław Bernat
- Department of Industrial Microbiology and Biotechnology, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
| | - Julia Pawłowska
- Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
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24
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Redhai S, Boutros M. The Role of Organelles in Intestinal Function, Physiology, and Disease. Trends Cell Biol 2021; 31:485-499. [PMID: 33551307 DOI: 10.1016/j.tcb.2021.01.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/04/2021] [Accepted: 01/11/2021] [Indexed: 02/06/2023]
Abstract
The intestine maintains homeostasis by coordinating internal biological processes to adjust to fluctuating external conditions. The intestinal epithelium is continuously renewed and comprises multiple cell types, including absorptive cells, secretory cells, and resident stem cells. An important feature of this organ is its ability to coordinate many processes including cell proliferation, differentiation, regeneration, damage/stress response, immune activity, feeding behavior, and age-related changes by using conserved signaling pathways. However, the subcellular spatial organization of these signaling events and the organelles involved has only recently been studied in detail. Here we discuss how organelles of intestinal cells serve to initiate, mediate, and terminate signals, that are vital for homeostasis.
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Affiliation(s)
- Siamak Redhai
- German Cancer Research Center (DKFZ), Division Signaling and Functional Genomics, and Heidelberg University, BioQuant and Medical Faculty Mannheim, D-69120 Heidelberg, Germany.
| | - Michael Boutros
- German Cancer Research Center (DKFZ), Division Signaling and Functional Genomics, and Heidelberg University, BioQuant and Medical Faculty Mannheim, D-69120 Heidelberg, Germany.
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25
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Schepers J, Behl C. Lipid droplets and autophagy-links and regulations from yeast to humans. J Cell Biochem 2021; 122:602-611. [PMID: 33522032 DOI: 10.1002/jcb.29889] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 12/04/2020] [Accepted: 12/28/2020] [Indexed: 12/22/2022]
Abstract
Recent advances in the yeast Saccharomyces cerevisiae and higher eukaryotes have been increasingly connecting lipid droplet (LD) dynamics to the regulation of autophagy. In this review we will discuss implications that connect LD de novo synthesis and LD mobilization to autophagy and how autophagy is regulated by these mechanisms. Elucidating these connections might pose a chance to further understand autophagy induction and membrane biogenesis for the growing autophagosome under different conditions. Increasing our understanding of these mechanisms might provide a chance to understand several conditions that might be related to LD dysregulation and, possibly, as a consequence of this, dysregulation of autophagy.
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Affiliation(s)
- Jana Schepers
- The Autophagy Lab, Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Christian Behl
- The Autophagy Lab, Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
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26
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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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27
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The phosphatidylethanolamine-binding protein DTH1 mediates degradation of lipid droplets in Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 2020; 117:23131-23139. [PMID: 32868427 DOI: 10.1073/pnas.2005600117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Lipid droplets (LDs) are intracellular organelles found in a wide range of organisms and play important roles in stress tolerance. During nitrogen (N) starvation, Chlamydomonas reinhardtii stores large amounts of triacylglycerols (TAGs) inside LDs. When N is resupplied, the LDs disappear and the TAGs are degraded, presumably providing carbon and energy for regrowth. The mechanism by which cells degrade LDs is poorly understood. Here, we isolated a mutant (dth1-1, Delayed in TAG Hydrolysis 1) in which TAG degradation during recovery from N starvation was compromised. Consequently, the dth1-1 mutant grew poorly compared to its parental line during N recovery. Two additional independent loss-of-function mutants (dth1-2 and dth1-3) also exhibited delayed TAG remobilization. DTH1 transcript levels increased sevenfold upon N resupply, and DTH1 protein was localized to LDs. DTH1 contains a putative lipid-binding domain (DTH1LBD) with alpha helices predicted to be structurally similar to those in apolipoproteins E and A-I. Recombinant DTH1LBD bound specifically to phosphatidylethanolamine (PE), a major phospholipid coating the LD surface. Overexpression of DTH1LBD in Chlamydomonas phenocopied the dth1 mutant's defective TAG degradation, suggesting that the function of DTH1 depends on its ability to bind PE. Together, our results demonstrate that the lipid-binding DTH1 plays an essential role in LD degradation and provide insight into the molecular mechanism of protein anchorage to LDs at the LD surface in photosynthetic cells.
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28
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Ganesan S, Tavassoli M, Shabits BN, Zaremberg V. Tubular ER Associates With Diacylglycerol-Rich Structures During Lipid Droplet Consumption. Front Cell Dev Biol 2020; 8:700. [PMID: 32850820 PMCID: PMC7403446 DOI: 10.3389/fcell.2020.00700] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/09/2020] [Indexed: 11/13/2022] Open
Abstract
Growth resumption from stationary phase in Saccharomyces cerevisiae, is characterized by lipid droplet (LD) consumption and channeling of lipid precursors toward synthesis of membranes. We have previously determined that triacylglycerol lipolysis contributes to a pool of diacylglycerol (DAG) associated with the yeast vacuole that is enriched in structures that are in close proximity to LDs. In this study we have monitored these structures using a DAG sensor fused to GFP during isolation of LDs. A unique fraction containing the DAG sensor, with low presence of LDs, was identified. Membranes enriched in the DAG probe were obtained by immunoaffinity purification using a GFP nanobody, and the associated proteome was investigated by mass spectrometry. It was determined this LD-associated fraction was enriched in proteins known to shape the tubular endoplasmic reticulum (ER) like Yop1, Sey1, Rtn1, and Rtn2. Consistently, cells lacking three of these proteins (rtn1Δ rtn2Δ yop1Δ) exhibited delayed LD consumption, larger LDs and abnormal LD distribution. In addition, the triple mutant displayed aberrant localization of the DAG sensor after 5 h of growth resumption from stationary phase. Manipulation of DAG levels by overexpression of the DAG kinase Dgk1, impacted localization of the DAG probe and affected fitness of the triple mutant. Altogether these results link LD consumption to tubular ER expansion as a gateway of lipid precursors that otherwise accumulate in vacuolar associated membranes or other internal compartments. Furthermore, conversion of DAG to phosphatidic acid (PA) in the absence of a functional tubular ER was toxic to cells, suggesting the ratio of PA to DAG is critical to allow growth progression.
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Affiliation(s)
| | - Marjan Tavassoli
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Brittney N Shabits
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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29
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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: 31] [Impact Index Per Article: 7.8] [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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30
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Zaman MF, Nenadic A, Radojičić A, Rosado A, Beh CT. Sticking With It: ER-PM Membrane Contact Sites as a Coordinating Nexus for Regulating Lipids and Proteins at the Cell Cortex. Front Cell Dev Biol 2020; 8:675. [PMID: 32793605 PMCID: PMC7387695 DOI: 10.3389/fcell.2020.00675] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/03/2020] [Indexed: 12/31/2022] Open
Abstract
Membrane contact sites between the cortical endoplasmic reticulum (ER) and the plasma membrane (PM) provide a direct conduit for small molecule transfer and signaling between the two largest membranes of the cell. Contact is established through ER integral membrane proteins that physically tether the two membranes together, though the general mechanism is remarkably non-specific given the diversity of different tethering proteins. Primary tethers including VAMP-associated proteins (VAPs), Anoctamin/TMEM16/Ist2p homologs, and extended synaptotagmins (E-Syts), are largely conserved in most eukaryotes and are both necessary and sufficient for establishing ER-PM association. In addition, other species-specific ER-PM tether proteins impart unique functional attributes to both membranes at the cell cortex. This review distils recent functional and structural findings about conserved and species-specific tethers that form ER-PM contact sites, with an emphasis on their roles in the coordinate regulation of lipid metabolism, cellular structure, and responses to membrane stress.
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Affiliation(s)
- Mohammad F Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Ana Radojičić
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Abel Rosado
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,The Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, BC, Canada
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31
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Lv X, Cui S, Gu Y, Li J, Du G, Liu L. Enzyme Assembly for Compartmentalized Metabolic Flux Control. Metabolites 2020; 10:E125. [PMID: 32224973 PMCID: PMC7241084 DOI: 10.3390/metabo10040125] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 11/16/2022] Open
Abstract
Enzyme assembly by ligand binding or physically sequestrating enzymes, substrates, or metabolites into isolated compartments can bring key molecules closer to enhance the flux of a metabolic pathway. The emergence of enzyme assembly has provided both opportunities and challenges for metabolic engineering. At present, with the development of synthetic biology and systems biology, a variety of enzyme assembly strategies have been proposed, from the initial direct enzyme fusion to scaffold-free assembly, as well as artificial scaffolds, such as nucleic acid/protein scaffolds, and even some more complex physical compartments. These assembly strategies have been explored and applied to the synthesis of various important bio-based products, and have achieved different degrees of success. Despite some achievements, enzyme assembly, especially in vivo, still has many problems that have attracted significant attention from researchers. Here, we focus on some selected examples to review recent research on scaffold-free strategies, synthetic artificial scaffolds, and physical compartments for enzyme assembly or pathway sequestration, and we discuss their notable advances. In addition, the potential applications and challenges in the applications are highlighted.
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Affiliation(s)
- Xueqin Lv
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Shixiu Cui
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Yang Gu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Jianghua Li
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Guocheng Du
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Long Liu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
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32
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Lee SH, Hadipour-Lakmehsari S, Murthy HR, Gibb N, Miyake T, Teng ACT, Cosme J, Yu JC, Moon M, Lim S, Wong V, Liu P, Billia F, Fernandez-Gonzalez R, Stagljar I, Sharma P, Kislinger T, Scott IC, Gramolini AO. REEP5 depletion causes sarco-endoplasmic reticulum vacuolization and cardiac functional defects. Nat Commun 2020; 11:965. [PMID: 32075961 PMCID: PMC7031342 DOI: 10.1038/s41467-019-14143-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/17/2019] [Indexed: 12/17/2022] Open
Abstract
The sarco-endoplasmic reticulum (SR/ER) plays an important role in the development and progression of many heart diseases. However, many aspects of its structural organization remain largely unknown, particularly in cells with a highly differentiated SR/ER network. Here, we report a cardiac enriched, SR/ER membrane protein, REEP5 that is centrally involved in regulating SR/ER organization and cellular stress responses in cardiac myocytes. In vitro REEP5 depletion in mouse cardiac myocytes results in SR/ER membrane destabilization and luminal vacuolization along with decreased myocyte contractility and disrupted Ca2+ cycling. Further, in vivo CRISPR/Cas9-mediated REEP5 loss-of-function zebrafish mutants show sensitized cardiac dysfunction upon short-term verapamil treatment. Additionally, in vivo adeno-associated viral (AAV9)-induced REEP5 depletion in the mouse demonstrates cardiac dysfunction. These results demonstrate the critical role of REEP5 in SR/ER organization and function as well as normal heart function and development.
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Affiliation(s)
- Shin-Haw Lee
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Sina Hadipour-Lakmehsari
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Harsha R Murthy
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
- Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Natalie Gibb
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
- Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Tetsuaki Miyake
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
- Department of Biology, Faculty of Science, York University, Toronto, ON, M3J1P3, Canada
| | - Allen C T Teng
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Jake Cosme
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Jessica C Yu
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, M5S3G9, Canada
| | - Mark Moon
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
- Ottawa Heart Institute, Ottawa, ON, K1Y4W7, Canada
| | - SangHyun Lim
- Donnelly Centre, University of Toronto, Toronto, ON, M5S1M8, Canada
- Department of Biochemistry, Faculty of Medicine, University of Toronto Canada, Toronto, Canada
| | - Victoria Wong
- Donnelly Centre, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Peter Liu
- Ottawa Heart Institute, Ottawa, ON, K1Y4W7, Canada
| | - Filio Billia
- Toronto General Research Institute, University Health Network, Toronto, ON, M5G2C4, Canada
| | - Rodrigo Fernandez-Gonzalez
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, M5S3G9, Canada
| | - Igor Stagljar
- Donnelly Centre, University of Toronto, Toronto, ON, M5S1M8, Canada
- Department of Biochemistry, Faculty of Medicine, University of Toronto Canada, Toronto, Canada
- Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, Canada
- Mediterranean Institute for Life Sciences, Split, Croatia
| | - Parveen Sharma
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
- Institute of Translational Medicine, University of Liverpool, Liverpool, L693BX, UK
| | - Thomas Kislinger
- Department of Medical Biophysics, University of Toronto, Toronto, Canada
- Princess Margaret Cancer Centre, Toronto, ON, M5G1L7, Canada
| | - Ian C Scott
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
- Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada
| | - Anthony O Gramolini
- Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, M5G1M1, Canada.
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, M5S1M8, Canada.
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33
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Henne M, Goodman JM, Hariri H. Spatial compartmentalization of lipid droplet biogenesis. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158499. [PMID: 31352131 PMCID: PMC7050823 DOI: 10.1016/j.bbalip.2019.07.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/08/2019] [Accepted: 07/09/2019] [Indexed: 12/18/2022]
Abstract
Lipid droplets (LDs) are ubiquitous organelles that store metabolic energy in the form of neutral lipids (typically triacylglycerols and steryl esters). Beyond being inert energy storage compartments, LDs are dynamic organelles that participate in numerous essential metabolic functions. Cells generate LDs de novo from distinct sub-regions at the endoplasmic reticulum (ER), but what determines sites of LD formation remains a key unanswered question. Here, we review the factors that determine LD formation at the ER, and discuss how they work together to spatially and temporally coordinate LD biogenesis. These factors include lipid synthesis enzymes, assembly proteins, and membrane structural requirements. LDs also make contact with other organelles, and these inter-organelle contacts contribute to defining sites of LD production. Finally, we highlight emerging non-canonical roles for LDs in maintaining cellular homeostasis during stress.
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Affiliation(s)
- Mike Henne
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Hanaa Hariri
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America.
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34
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Kiegerl B, Tavassoli M, Smart H, Shabits BN, Zaremberg V, Athenstaedt K. Phosphorylation of the lipid droplet localized glycerol‑3‑phosphate acyltransferase Gpt2 prevents a futile triacylglycerol cycle in yeast. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:158509. [DOI: 10.1016/j.bbalip.2019.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 08/09/2019] [Accepted: 08/12/2019] [Indexed: 11/30/2022]
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35
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Hugenroth M, Bohnert M. Come a little bit closer! Lipid droplet-ER contact sites are getting crowded. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118603. [PMID: 31733263 DOI: 10.1016/j.bbamcr.2019.118603] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/26/2019] [Accepted: 10/29/2019] [Indexed: 12/12/2022]
Abstract
Not so long ago, contact sites between the endoplasmic reticulum (ER) and lipid droplets (LDs) were largely unexplored on a molecular level. In recent years however, numerous proteins have been identified that are enriched or exclusively located at the interfaces between LDs and the ER. These comprise members of protein classes typically found in diverse types of contacts, such as organelle tethers and lipid transfer proteins, but also proteins that have no similarities to known contact site machineries. This structurally heterogeneous group of contact site residents might be required to fulfill unique aspects of LD-ER contact biology, such as de novo LD biogenesis, and maintenance of lipidic connections between LDs and ER. Here, we summarize the current knowledge on the molecular components of this special organelle contact site, and discuss their features and functions.
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Affiliation(s)
- Marie Hugenroth
- Institute of Cell Dynamics and Imaging, University of Münster, Von-Esmarch-Str. 56, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany
| | - Maria Bohnert
- Institute of Cell Dynamics and Imaging, University of Münster, Von-Esmarch-Str. 56, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany.
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36
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Exner T, Beretta CA, Gao Q, Afting C, Romero-Brey I, Bartenschlager R, Fehring L, Poppelreuther M, Füllekrug J. Lipid droplet quantification based on iterative image processing. J Lipid Res 2019; 60:1333-1344. [PMID: 30926625 DOI: 10.1194/jlr.d092841] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 03/28/2019] [Indexed: 12/15/2022] Open
Abstract
Lipid droplets (LDs) are ubiquitous and highly dynamic subcellular organelles required for the storage of neutral lipids. LD number and size distribution are key parameters affected not only by nutrient supply but also by lipotoxic stress and metabolic regulation. Current methods for LD quantification lack general applicability and are either based on time consuming manual evaluation or show limitations if LDs are high in numbers or closely clustered. Here, we present an ImageJ-based approach for the detection and quantification of LDs stained by neutral lipid dyes in images acquired by conventional wide-field fluorescence microscopy. The method features an adjustable preprocessing procedure that resolves LD clusters. LD identification is based on their circular edges and central fluorescence intensity maxima. Adaptation to different cell types is mediated by a set of interactive parameters. Validation was done for three different cell lines using manual evaluation of LD numbers and volume measurement by 3D rendering of confocal datasets. In an application example, we show that overexpression of the acyl-CoA synthetase, FATP4/ACSVL5, in oleate-treated COS7 cells increased the size of LDs but not their number.
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Affiliation(s)
- Tarik Exner
- Molecular Cell Biology Laboratory Internal Medicine IV, Heidelberg University, Heidelberg, Germany
| | - Carlo A Beretta
- CellNetworks Math-Clinic Core Facility, BioQuant Heidelberg University, Heidelberg, Germany
| | - Qi Gao
- CellNetworks Math-Clinic Core Facility, BioQuant Heidelberg University, Heidelberg, Germany
| | - Cassian Afting
- Molecular Cell Biology Laboratory Internal Medicine IV, Heidelberg University, Heidelberg, Germany
| | - Inés Romero-Brey
- Department of Infectious Diseases, Molecular Virology Heidelberg University, Heidelberg, Germany
| | - Ralf Bartenschlager
- Department of Infectious Diseases, Molecular Virology Heidelberg University, Heidelberg, Germany.,Department of Virus-Associated Carcinogenesis, German Cancer Research Center, Heidelberg, Germany
| | - Leonard Fehring
- Molecular Cell Biology Laboratory Internal Medicine IV, Heidelberg University, Heidelberg, Germany
| | - Margarete Poppelreuther
- Molecular Cell Biology Laboratory Internal Medicine IV, Heidelberg University, Heidelberg, Germany
| | - Joachim Füllekrug
- Molecular Cell Biology Laboratory Internal Medicine IV, Heidelberg University, Heidelberg, Germany
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37
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Rockenfeller P, Gourlay CW. Lipotoxicty in yeast: a focus on plasma membrane signalling and membrane contact sites. FEMS Yeast Res 2019; 18:4953420. [PMID: 29718175 PMCID: PMC5905628 DOI: 10.1093/femsyr/foy034] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/23/2018] [Indexed: 12/23/2022] Open
Abstract
Lipotoxicity is a pathophysiological process triggered by lipid overload. In metazoans, lipotoxicity is characterised by the ectopic deposition of lipids on organs other than adipose tissue. This leads to organ dysfunction, cell death, and is intimately linked to lipid-associated diseases such as cardiac dysfunction, atherosclerosis, stroke, hepatosteatosis, cancer and the metabolic syndrome. The molecules involved in eliciting lipotoxicity include FAs and their acyl-CoA derivatives, triacylglycerol (TG), diacylglycerol (DG), ceramides, acyl-carnitines and phospholipids. However, the cellular transport of toxic lipids through membrane contact sites (MCS) and vesicular mechanisms as well as lipid metabolism that progress lipotoxicity to the onset of disease are not entirely understood. Yeast has proven a useful model organism to study the molecular mechanisms of lipotoxicity. Recently, the Rim101 pathway, which senses alkaline pH and the lipid status at the plasmamembrane, has been connected to lipotoxicity. In this review article, we summarise recent research advances on the Rim101 pathway and MCS in the context of lipotoxicity in yeast and present a perspective for future research directions.
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Affiliation(s)
- Patrick Rockenfeller
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, CT2 7NJ Kent, UK.,Institute of Molecular Biosciences, NAWI Graz, University of Graz, Humboldtstr. 50, 8010 Graz, Austria
| | - Campbell W Gourlay
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, CT2 7NJ Kent, UK
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38
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Preuss C, Jelenik T, Bódis K, Müssig K, Burkart V, Szendroedi J, Roden M, Markgraf DF. A New Targeted Lipidomics Approach Reveals Lipid Droplets in Liver, Muscle and Heart as a Repository for Diacylglycerol and Ceramide Species in Non-Alcoholic Fatty Liver. Cells 2019; 8:cells8030277. [PMID: 30909521 PMCID: PMC6468791 DOI: 10.3390/cells8030277] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 03/14/2019] [Accepted: 03/19/2019] [Indexed: 12/13/2022] Open
Abstract
Obesity is frequently associated with excessive accumulation of lipids in ectopic tissue and presents a major risk factor for type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). Diacylglycerols (DAGs) and ceramides (CERs) were identified as key players in lipid-induced insulin resistance, typical for such diseases. Recent results suggest that the subcellular distribution of these lipids affects their lipotoxic properties. However, the subcellular dynamics of these lipids and the role of lipid droplets (LDs) as a potential storage site is not understood. Here, we developed a liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS)-method for the rapid and simultaneous quantification of DAG and CER species in tissue sample fractions. The assay is characterized by excellent recovery of analytes, limit of quantification, accuracy and precision. We established a fractionation protocol that allows the separation of subcellular tissue fractions. This method was subsequently tested to measure the concentration of DAGs and CERs in subcellular fractions of human muscle and several mouse tissues. In a mouse model of NAFLD, application of this method revealed a prominent role for LDs as repository for lipotoxic DAG and CER species. In conclusion, the new method proved as a valuable tool to analyse the subcellular dynamics of lipotoxins, related to the pathogenesis of insulin resistance, T2D and NAFLD.
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Affiliation(s)
- Christina Preuss
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
| | - Tomas Jelenik
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
| | - Kálmán Bódis
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
| | - Karsten Müssig
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
- Division of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, D-40225, Düsseldorf, Germany.
| | - Volker Burkart
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
| | - Julia Szendroedi
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
- Division of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, D-40225, Düsseldorf, Germany.
| | - Michael Roden
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
- Division of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, D-40225, Düsseldorf, Germany.
| | - Daniel F Markgraf
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.
- German Center for Diabetes Research (DZD e.V.), München, D-85764 Neuherberg, Germany.
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39
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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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40
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Regulation of targeting determinants in interorganelle communication. Curr Opin Cell Biol 2019; 57:106-114. [PMID: 30807956 DOI: 10.1016/j.ceb.2018.12.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 12/27/2018] [Accepted: 12/28/2018] [Indexed: 01/02/2023]
Abstract
The field of interorganelle communication is now established as a major aspect of intracellular organisation, with a profusion of material and signals exchanged between organelles. One way to address interorganelle communication is to study the interactions of the proteins involved, particularly targeting interactions, which are a key way to regulate activity. While most peripheral membrane proteins have single determinants for membrane targeting, proteins involved in interorganelle communication have more than one such determinant, sometimes as many as four, as in Vps13. Here we review the targeting determinants, showing how they can be relatively hard to find, how they are regulated, and how proteins integrate information from multiple targeting determinants.
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41
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Grzybek M, Palladini A, Alexaki VI, Surma MA, Simons K, Chavakis T, Klose C, Coskun Ü. Comprehensive and quantitative analysis of white and brown adipose tissue by shotgun lipidomics. Mol Metab 2019; 22:12-20. [PMID: 30777728 PMCID: PMC6437637 DOI: 10.1016/j.molmet.2019.01.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/17/2019] [Accepted: 01/23/2019] [Indexed: 12/12/2022] Open
Abstract
Objective Shotgun lipidomics enables an extensive analysis of lipids from tissues and fluids. Each specimen requires appropriate extraction and processing procedures to ensure good coverage and reproducible quantification of the lipidome. Adipose tissue (AT) has become a research focus with regard to its involvement in obesity-related pathologies. However, the quantification of the AT lipidome is particularly challenging due to the predominance of triacylglycerides, which elicit high ion suppression of the remaining lipid classes. Methods We present a new and validated method for shotgun lipidomics of AT, which tailors the lipid extraction procedure to the target specimen and features high reproducibility with a linear dynamic range of at least 4 orders of magnitude for all lipid classes. Results Utilizing this method, we observed tissue-specific and diet-related differences in three AT types (brown, gonadal, inguinal subcutaneous) from lean and obese mice. Brown AT exhibited a distinct lipidomic profile with the greatest lipid class diversity and responded to high-fat diet by altering its lipid composition, which shifted towards that of white AT. Moreover, diet-induced obesity promoted an overall remodeling of the lipidome, where all three AT types featured a significant increase in longer and more unsaturated triacylglyceride and phospholipid species. Conclusions The here presented method facilitates reproducible systematic lipidomic profiling of AT and could be integrated with further –omics approaches used in (pre-) clinical research, in order to advance the understanding of the molecular metabolic dynamics involved in the pathogenesis of obesity-associated disorders. Validated shotgun lipidomics method of AT covering 300 lipids of 20 classes and linear dynamic range of 4 orders of magnitude. Increase of longer and more unsaturated triacylglycerides and phospholipids in brown and white AT under high-fat diet. Differences in the lipidomes of gonadal, subcutaneous and brown AT.
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Affiliation(s)
- Michal Grzybek
- Paul Langerhans Institute Dresden of the Helmholtz Zentrum Munich at the University Clinic Carl Gustav Carus, TU Dresden, Dresden, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Alessandra Palladini
- Paul Langerhans Institute Dresden of the Helmholtz Zentrum Munich at the University Clinic Carl Gustav Carus, TU Dresden, Dresden, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Vasileia I Alexaki
- Institute for Clinical Chemistry and Laboratory Medicine, Faculty of Medicine, TU Dresden, Dresden, Germany
| | | | | | - Triantafyllos Chavakis
- Paul Langerhans Institute Dresden of the Helmholtz Zentrum Munich at the University Clinic Carl Gustav Carus, TU Dresden, Dresden, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany; Institute for Clinical Chemistry and Laboratory Medicine, Faculty of Medicine, TU Dresden, Dresden, Germany
| | | | - Ünal Coskun
- Paul Langerhans Institute Dresden of the Helmholtz Zentrum Munich at the University Clinic Carl Gustav Carus, TU Dresden, Dresden, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany.
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42
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Ganesan S, Sosa Ponce ML, Tavassoli M, Shabits BN, Mahadeo M, Prenner EJ, Terebiznik MR, Zaremberg V. Metabolic control of cytosolic-facing pools of diacylglycerol in budding yeast. Traffic 2019; 20:226-245. [PMID: 30569465 DOI: 10.1111/tra.12632] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 12/18/2018] [Accepted: 12/18/2018] [Indexed: 12/12/2022]
Abstract
Diacylglycerol (DAG) is a key signaling lipid and intermediate in lipid metabolism. Our knowledge of DAG distribution and dynamics in cell membranes is limited. Using live-cell fluorescence microscopy we investigated the localization of yeast cytosolic-facing pools of DAG in response to conditions where lipid homeostasis and DAG levels were known to be altered. Two main pools were monitored over time using DAG sensors. One pool was associated with vacuolar membranes and the other localized to sites of polarized growth. Dynamic changes in DAG distribution were observed during resumption of growth from stationary phase, when DAG is used to support phospholipid synthesis for membrane proliferation. Vacuolar membranes experienced constant morphological changes displaying DAG enriched microdomains coexisting with liquid-disordered areas demarcated by Vph1. Formation of these domains was dependent on triacylglycerol (TAG) lipolysis. DAG domains and puncta were closely connected to lipid droplets. Lack of conversion of DAG to phosphatidate in growth conditions dependent on TAG mobilization, led to the accumulation of DAG in a vacuolar-associated compartment, impacting the polarized distribution of DAG at budding sites. DAG polarization was also regulated by phosphatidylserine synthesis/traffic and sphingolipid synthesis in the Golgi.
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Affiliation(s)
| | - Maria L Sosa Ponce
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Marjan Tavassoli
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Brittney N Shabits
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Mark Mahadeo
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Elmar J Prenner
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Mauricio R Terebiznik
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.,Department of Cell and System Biology, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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43
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Döring S, Seeßle J, Gan-Schreier H, Javaheri B, Jiao L, Cheng Y, Tuma-Kellner S, Liebisch G, Herrmann T, Stremmel W, Chamulitrat W. Elevation of blood lipids in hepatocyte-specific fatty acid transport 4-deficient mice fed with high glucose diets. Mol Genet Metab 2019; 126:30-38. [PMID: 30497809 DOI: 10.1016/j.ymgme.2018.11.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/12/2018] [Accepted: 11/17/2018] [Indexed: 11/20/2022]
Abstract
Fatty acid transport protein4 (FATP4) is upregulated in acquired and central obesity and its polymorphisms are associated with blood lipids and insulin resistance. Patients with FATP4 mutations and mice with global FATP4 deletion exhibit skin abnormalities characterized as ischthyosis prematurity syndrome (IPS). Cumulating data have shown that an absence of FATP4 increases the levels of cellular triglycerides (TG). However, FATP4 role and consequent lipid and TG metabolism in the hepatocyte is still elusive. Here, hepatocyte-specific FATP4 deficient (Fatp4L-/-) mice were generated. When fed with chow, these mutant mice displayed no phenotypes regarding blood lipids. However when fed low-fat/high-sugar (HS) or high-fat/high-sugar (HFS) for 12 weeks, Fatp4L-/- mice showed a significant increase of plasma TG, free fatty acids and glycerol when compared with diet-fed control mice. Interestingly, Fatp4L-/- mice under HS diet had lower body and liver weights and they were not protected from HFS-induced body weight gain and hepatic steatosis. Male mutant mice were more sensitive to HFS diet than female mutant mice. Glucose intolerance was observed only in female Fatp4L-/- mice fed with HS diet. Lipidomics analyses revealed that hepatic phospholipids were not disturbed in mutant mice under both diets. Thus, hepatic FATP4 deletion rendered an increase of blood lipids including glycerol indicating a preferential fatty-acid channeling to TG pools that are specifically available for lipolysis. Our results imply a possible risk of hyperlipidemia as a result of abnormal metabolism in liver in IPS patients with FATP4 mutations who consume high-sugar diets.
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Affiliation(s)
- Stephan Döring
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Jessica Seeßle
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Hongying Gan-Schreier
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Bahador Javaheri
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Li Jiao
- Institute of Medical Biology, Chinese Academy of Medical Sciences, Peking Union Medical College, Kunming, Yunnan 650118, China
| | - Yuting Cheng
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Sabine Tuma-Kellner
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Gerhard Liebisch
- Institute of Clinical Chemistry and Laboratory Medicine, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Thomas Herrmann
- Westkuesten Hospital, Esmarchstraße 50, 25746 Heide, Germany
| | - Wolfgang Stremmel
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
| | - Walee Chamulitrat
- Department of Internal Medicine IV, University of Heidelberg Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
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44
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Salo VT, Ikonen E. Moving out but keeping in touch: contacts between endoplasmic reticulum and lipid droplets. Curr Opin Cell Biol 2018; 57:64-70. [PMID: 30476754 DOI: 10.1016/j.ceb.2018.11.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 11/06/2018] [Accepted: 11/07/2018] [Indexed: 12/14/2022]
Abstract
The formation of neutral lipid filled and phospholipid monolayer engulfed lipid droplets (LDs) from the bilayer of the endoplasmic reticulum (ER) is an active area of investigation. This process harnesses the biophysical properties of the lipids involved and necessitates cooperation of protein machineries in both organelle membranes. Increasing evidence suggests that once formed, LDs keep close contact to the mother organelle and that this may be achieved via several, morphologically distinct and potentially functionally specialized connections. These may help LDs to dynamically respond to changes in lipid metabolic status sensed by the ER. In this review, we will discuss recent progress in understanding how LDs interact with the ER.
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Affiliation(s)
- Veijo T Salo
- Faculty of Medicine, Dept. of Anatomy and HiLIFE, Univ. of Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Elina Ikonen
- Faculty of Medicine, Dept. of Anatomy and HiLIFE, Univ. of Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
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45
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Joshi AS, Nebenfuehr B, Choudhary V, Satpute-Krishnan P, Levine TP, Golden A, Prinz WA. Lipid droplet and peroxisome biogenesis occur at the same ER subdomains. Nat Commun 2018; 9:2940. [PMID: 30054481 PMCID: PMC6063926 DOI: 10.1038/s41467-018-05277-3] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 06/18/2018] [Indexed: 12/19/2022] Open
Abstract
Nascent lipid droplet (LD) formation occurs in the endoplasmic reticulum (ER) membrane but it is not known how sites of biogenesis are determined. We previously identified ER domains in S. cerevisiae containing the reticulon homology domain (RHD) protein Pex30 that are regions where preperoxisomal vesicles (PPVs) form. Here, we show that Pex30 domains are also sites where most nascent LDs form. Mature LDs usually remain associated with Pex30 subdomains, and the same Pex30 subdomain can simultaneously associate with a LD and a PPV or peroxisome. We find that in higher eukaryotes multiple C2 domain containing transmembrane protein (MCTP2) is similar to Pex30: it contains an RHD and resides in ER domains where most nascent LD biogenesis occurs and that often associate with peroxisomes. Together, these findings indicate that most LDs and PPVs form and remain associated with conserved ER subdomains, and suggest a link between LD and peroxisome biogenesis.
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Affiliation(s)
- Amit S Joshi
- National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA.
| | - Benjamin Nebenfuehr
- National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Vineet Choudhary
- National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | | | - Tim P Levine
- University College London, Institute of Ophthalmology, London, EC1V 9EL, UK
| | - Andy Golden
- National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - William A Prinz
- National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA.
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46
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Cohen S, Valm AM, Lippincott-Schwartz J. Interacting organelles. Curr Opin Cell Biol 2018; 53:84-91. [PMID: 30006038 DOI: 10.1016/j.ceb.2018.06.003] [Citation(s) in RCA: 152] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/06/2018] [Accepted: 06/12/2018] [Indexed: 12/11/2022]
Abstract
Eukaryotic cells are organized into membrane-bound organelles. These organelles communicate with one another through vesicular trafficking pathways and membrane contact sites (MCSs). MCSs are sites of close apposition between two or more organelles that play diverse roles in the exchange of metabolites, lipids and proteins. Organelle interactions at MCSs also are important for organelle division and biogenesis. For example, the division of several organelles, including mitochondria and endosomes, seem to be regulated by contacts with the endoplasmic reticulum (ER). Moreover, the biogenesis of autophagosomes and peroxisomes involves contributions from the ER and multiple other cellular compartments. Thus, organelle-organelle interactions allow cells to alter the shape and activities of their membrane-bound compartments, allowing them to cope with different developmental and environmental conditions.
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Affiliation(s)
- Sarah Cohen
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Alex M Valm
- University at Albany, SUNY, Albany, NY, United States
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47
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Ouahoud S, Fiet MD, Martínez-Montañés F, Ejsing CS, Kuss O, Roden M, Markgraf DF. Lipid droplet consumption is functionally coupled to vacuole homeostasis independent of lipophagy. J Cell Sci 2018; 131:jcs.213876. [PMID: 29678904 DOI: 10.1242/jcs.213876] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 04/13/2018] [Indexed: 01/19/2023] Open
Abstract
Lipid droplets (LDs) store neutral lipids and are integrated into a cellular metabolic network that relies on functional coupling with various organelles. Factors mediating efficient coupling and mechanisms regulating them remain unknown. Here, we conducted a global screen in S. cerevisiae to identify genes required for the functional coupling of LDs and other organelles during LD consumption. We show that LD utilization during growth resumption is coupled to vacuole homeostasis. ESCRT-, V-ATPase- and vacuole protein sorting-mutants negatively affect LD consumption, independent of lipophagy. Loss of ESCRT function leads to the accumulation of LD-derived diacylglycerol (DAG), preventing its conversion into phosphatidic acid (PA) and membrane lipids. In addition, channeling of DAG from LD-proximal sites to the vacuole is blocked. We demonstrate that utilization of LDs requires intact vacuolar signaling via TORC1 and its downstream effector Sit4p. These data suggest that vacuolar status is coupled to LD catabolism via TORC1-mediated regulation of DAG-PA interconversion and explain how cells coordinate organelle dynamics throughout cell growth.
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Affiliation(s)
- Sarah Ouahoud
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.,German Center for Diabetes Research (DZD e.V.), München, Neuherberg, Germany
| | - Mitchell D Fiet
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.,German Center for Diabetes Research (DZD e.V.), München, Neuherberg, Germany
| | - Fernando Martínez-Montañés
- Department of Biochemistry and Molecular Biology, Villum Center for Bioanalytical Sciences, University of Southern Denmark, 5230 Odense, Denmark
| | - Christer S Ejsing
- Department of Biochemistry and Molecular Biology, Villum Center for Bioanalytical Sciences, University of Southern Denmark, 5230 Odense, Denmark.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
| | - Oliver Kuss
- German Center for Diabetes Research (DZD e.V.), München, Neuherberg, Germany.,Institute for Biometrics and Epidemiology, German Diabetes Center, Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany
| | - Michael Roden
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany.,German Center for Diabetes Research (DZD e.V.), München, Neuherberg, Germany.,Division of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, D-40225 Düsseldorf, Germany
| | - Daniel F Markgraf
- Institute for Clinical Diabetology, German Diabetes Center, c/o Auf'm Hennekamp 65, D-40225 Düsseldorf, Germany .,German Center for Diabetes Research (DZD e.V.), München, Neuherberg, Germany
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48
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Henne WM, Reese ML, Goodman JM. The assembly of lipid droplets and their roles in challenged cells. EMBO J 2018; 37:embj.201898947. [PMID: 29789390 DOI: 10.15252/embj.201898947] [Citation(s) in RCA: 171] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 03/08/2018] [Accepted: 03/22/2018] [Indexed: 12/14/2022] Open
Abstract
Cytoplasmic lipid droplets are important organelles in nearly every eukaryotic and some prokaryotic cells. Storing and providing energy is their main function, but they do not work in isolation. They respond to stimuli initiated either on the cell surface or in the cytoplasm as conditions change. Cellular stresses such as starvation and invasion are internal insults that evoke changes in droplet metabolism and dynamics. This review will first outline lipid droplet assembly and then discuss how droplets respond to stress and in particular nutrient starvation. Finally, the role of droplets in viral and microbial invasion will be presented, where an unresolved issue is whether changes in droplet abundance promote the invader, defend the host, to try to do both. The challenges of stress and infection are often accompanied by changes in physical contacts between droplets and other organelles. How these changes may result in improving cellular physiology, an ongoing focus in the field, is discussed.
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Affiliation(s)
- W Mike Henne
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, TX, USA
| | - Michael L Reese
- Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX, USA
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX, USA
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Quon E, Sere YY, Chauhan N, Johansen J, Sullivan DP, Dittman JS, Rice WJ, Chan RB, Di Paolo G, Beh CT, Menon AK. Endoplasmic reticulum-plasma membrane contact sites integrate sterol and phospholipid regulation. PLoS Biol 2018; 16:e2003864. [PMID: 29782498 PMCID: PMC5983861 DOI: 10.1371/journal.pbio.2003864] [Citation(s) in RCA: 101] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 06/01/2018] [Accepted: 04/20/2018] [Indexed: 01/21/2023] Open
Abstract
Tether proteins attach the endoplasmic reticulum (ER) to other cellular membranes, thereby creating contact sites that are proposed to form platforms for regulating lipid homeostasis and facilitating non-vesicular lipid exchange. Sterols are synthesized in the ER and transported by non-vesicular mechanisms to the plasma membrane (PM), where they represent almost half of all PM lipids and contribute critically to the barrier function of the PM. To determine whether contact sites are important for both sterol exchange between the ER and PM and intermembrane regulation of lipid metabolism, we generated Δ-super-tether (Δ-s-tether) yeast cells that lack six previously identified tethering proteins (yeast extended synatotagmin [E-Syt], vesicle-associated membrane protein [VAMP]-associated protein [VAP], and TMEM16-anoctamin homologues) as well as the presumptive tether Ice2. Despite the lack of ER-PM contacts in these cells, ER-PM sterol exchange is robust, indicating that the sterol transport machinery is either absent from or not uniquely located at contact sites. Unexpectedly, we found that the transport of exogenously supplied sterol to the ER occurs more slowly in Δ-s-tether cells than in wild-type (WT) cells. We pinpointed this defect to changes in sterol organization and transbilayer movement within the PM bilayer caused by phospholipid dysregulation, evinced by changes in the abundance and organization of PM lipids. Indeed, deletion of either OSH4, which encodes a sterol/phosphatidylinositol-4-phosphate (PI4P) exchange protein, or SAC1, which encodes a PI4P phosphatase, caused synthetic lethality in Δ-s-tether cells due to disruptions in redundant PI4P and phospholipid regulatory pathways. The growth defect of Δ-s-tether cells was rescued with an artificial "ER-PM staple," a tether assembled from unrelated non-yeast protein domains, indicating that endogenous tether proteins have nonspecific bridging functions. Finally, we discovered that sterols play a role in regulating ER-PM contact site formation. In sterol-depleted cells, levels of the yeast E-Syt tether Tcb3 were induced and ER-PM contact increased dramatically. These results support a model in which ER-PM contact sites provide a nexus for coordinating the complex interrelationship between sterols, sphingolipids, and phospholipids that maintain PM composition and integrity. Almost half of the inner surface area of the yeast plasma membrane (PM) is covered with closely associated cortical endoplasmic reticulum (ER). In yeast and human cells, it has been proposed that ER-anchored tether proteins staple the ER to the PM, creating membrane contact sites at which lipid transport between the ER and PM and membrane lipid synthesis are coordinately regulated, but the potential mechanisms are unclear. Here, we test this idea by creating yeast cells that lack all ER-PM tethers. We find that whereas the bidirectional transport of sterols between the ER and PM is unaffected in these cells, sterols within the PM are disorganized due to disruptions in phospholipid biosynthesis that alter PM lipid composition. In particular, we show that phosphatidylinositol-4-phosphate, a phospholipid needed for intracellular signaling and membrane trafficking, accumulates within the PM. Some of these defects can be rescued by reinstating membrane contacts via expression of an artificial tether. However, correction is also achieved without the creation of contacts by supplementing the growth medium with a precursor of membrane phospholipids. Based on these results, we propose that ER-PM contacts do not play a major role as physical conduits for lipid exchange but rather serve as regulatory interfaces to integrate lipid synthesis pathways.
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Affiliation(s)
- Evan Quon
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Yves Y. Sere
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Neha Chauhan
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Jesper Johansen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - David P. Sullivan
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Jeremy S. Dittman
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - William J. Rice
- Simons Electron Microscopy Center at the New York Structural Biology Center, New York, New York, United States of America
| | - Robin B. Chan
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Gilbert Di Paolo
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- Denali Therapeutics, South San Francisco, California, United States of America
| | - Christopher T. Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
- * E-mail: (AKM); (CTB)
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: (AKM); (CTB)
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Graef M. Lipid droplet-mediated lipid and protein homeostasis in budding yeast. FEBS Lett 2018; 592:1291-1303. [PMID: 29397034 PMCID: PMC5947121 DOI: 10.1002/1873-3468.12996] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 12/25/2022]
Abstract
Lipid droplets are conserved specialized organelles that store neutral lipids. Our view on this unique organelle has evolved from a simple fat deposit to a highly dynamic and functionally diverse hub—one that mediates the buffering of fatty acid stress and the adaptive reshaping of lipid metabolism to promote membrane and organelle homeostasis and the integrity of central proteostasis pathways, including autophagy, which ensure stress resistance and cell survival. This Review will summarize the recent developments in the budding yeast Saccharomyces cerevisiae, as this model organism has been instrumental in deciphering the fundamental mechanisms and principles of lipid droplet biology and interconnecting lipid droplets with many unanticipated cellular functions applicable to many other cell systems.
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Affiliation(s)
- Martin Graef
- Max Planck Institute for Biology of Ageing, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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