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Hou JT, Li C, Guo S, Ye X, Chi W, Ren Y, Wang Q, Shen J. Polarity-Driven Fluorescence Monitoring of Lipid Droplet Dynamics in Dry Eye Disease. Anal Chem 2024; 96:9975-9983. [PMID: 38830231 DOI: 10.1021/acs.analchem.4c01366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
The emergence of lipid droplets (LDs) has been recognized as cellular markers of ocular surface hyperosmosis, which is recognized as a fundamental mechanism driving dry eye disease (DED), while their dynamics during DED progression and therapy remains unlocked. For this purpose, an LD-specific fluorescent probe P1 is presented in this work that exhibits highly selective and sensitive emission enhancement in response to a decreased ambient polarity (Δf) from 0.209 to 0.021. The hydrophobic nature of P1 enables specific staining of LDs, facilitating visualization of changes in polarity within these cellular structures. Utilizing P1, we observe a decrease in polarity accompanied by an increase in the size and number of LDs in hyperosmotic human corneal epithelial cells (HCECs). Furthermore, interplays between LDs and cellular organelles such as mitochondria and the Golgi apparatus are visualized, suggesting the underlying pathogenesis in DED. Notably, the variations of LDs are observed after the inhibition of ferroptosis or activation of autophagy in hyperosmotic HCECs, implying the great potential of LDs as indicators for the design and efficacy evaluation of DED drugs regarding ferroptosis or autophagy as targets. Finally, LDs are confirmed to be overproduced in corneal tissues from DED mice, and the application of clinical eye drops effectively impedes these changes. This detailed exploration underscores the significant roles of LDs as an indicator for the deep insight into DED advancement and therapy.
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Affiliation(s)
- Ji-Ting Hou
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
| | - Chen Li
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
| | - Shuai Guo
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
| | - Xuanqiao Ye
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
| | - Weijie Chi
- Collaborative Innovation Center of OneHealth, School of Chemistry and Chemical Engineering, Hainan University, Renmin Road 58, Haikou 570228, China
| | - Yueping Ren
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
| | - Qiang Wang
- Department of Ophthalmology, Third Affiliated Hospital, Wenzhou Medical University, Ruian 325200, China
| | - Jianliang Shen
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou 325027, China
- Zhejiang Engineering Research Center for Tissue Repair Materials, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325001, China
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Luo Q, Wang J, Ge W, Li Z, Mao Y, Wang C, Zhang L. Exploration of the potential causative genes for inflammatory bowel disease: Transcriptome-wide association analysis, Mendelian randomization analysis and Bayesian colocalisation. Heliyon 2024; 10:e28944. [PMID: 38617957 PMCID: PMC11015108 DOI: 10.1016/j.heliyon.2024.e28944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 03/27/2024] [Accepted: 03/27/2024] [Indexed: 04/16/2024] Open
Abstract
Background Inflammatory bowel disease (IBD) poses a complex challenge due to its intricate underlying mechanisms, and curative treatments remain elusive. Consequently, there is an urgent need to identify genes causally associated with IBD. Methods We extracted blood eQTL data from the GTExv8.ALL.Whole_Blood database, genome-wide association studies (GWAS) summary statistics of IBD from the IEU GWAS database, and performed a three-fold analysis protocol, including transcriptome-wide association analysis, Mendelian randomisation analysis, Bayesian colocalisation, and subsequent potential therapeutic agents identification. Results We identified four pathogenic genes, namely CARD9, RTEL1, STMN3 and ARFRP1, that promote the development of IBD, encompassing both ulcerative colitis (UC) and Crohn's disease (CD). Notably, ARFRP1 exhibited the ability to suppress IBD (encompassing UC and CD) development. Regarding drug prediction, cyclophosphamide emerged as a promising novel therapeutic option for IBD, encompassing UC and CD. Conclusion We identified several potential genes related to IBD (UC and CD), including CARD9, RTEL1, STMN3 and ARFRP1, warranting further investigation in functional studies to elucidate underlying disease mechanisms. Additionally, clinical studies exploring the potential of cyclophosphamide as a treatment avenue for IBD are warranted.
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Affiliation(s)
- Qinghua Luo
- Clinical Medical College, Jiangxi University of Chinese Medicine, Nanchang, China
| | - Jiawen Wang
- Department of Proctology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Wei Ge
- Department of Proctology, Affiliated Hospital of Jiangxi University of Chinese Medicine, Nanchang, China
| | - Zihao Li
- Office of the President, Jiangmen Wuyi Hospital of Traditional Chinese Medicine, Jiangmen, China
| | - Yuanting Mao
- Clinical Medical College, Jiangxi University of Chinese Medicine, Nanchang, China
| | - Chen Wang
- Department of Proctology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Leichang Zhang
- Formula-Pattern Research Center, Jiangxi University of Chinese Medicine, Jiangxi, China
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Varland S, Silva RD, Kjosås I, Faustino A, Bogaert A, Billmann M, Boukhatmi H, Kellen B, Costanzo M, Drazic A, Osberg C, Chan K, Zhang X, Tong AHY, Andreazza S, Lee JJ, Nedyalkova L, Ušaj M, Whitworth AJ, Andrews BJ, Moffat J, Myers CL, Gevaert K, Boone C, Martinho RG, Arnesen T. N-terminal acetylation shields proteins from degradation and promotes age-dependent motility and longevity. Nat Commun 2023; 14:6774. [PMID: 37891180 PMCID: PMC10611716 DOI: 10.1038/s41467-023-42342-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 10/06/2023] [Indexed: 10/29/2023] Open
Abstract
Most eukaryotic proteins are N-terminally acetylated, but the functional impact on a global scale has remained obscure. Using genome-wide CRISPR knockout screens in human cells, we reveal a strong genetic dependency between a major N-terminal acetyltransferase and specific ubiquitin ligases. Biochemical analyses uncover that both the ubiquitin ligase complex UBR4-KCMF1 and the acetyltransferase NatC recognize proteins bearing an unacetylated N-terminal methionine followed by a hydrophobic residue. NatC KO-induced protein degradation and phenotypes are reversed by UBR knockdown, demonstrating the central cellular role of this interplay. We reveal that loss of Drosophila NatC is associated with male sterility, reduced longevity, and age-dependent loss of motility due to developmental muscle defects. Remarkably, muscle-specific overexpression of UbcE2M, one of the proteins targeted for NatC KO-mediated degradation, suppresses defects of NatC deletion. In conclusion, NatC-mediated N-terminal acetylation acts as a protective mechanism against protein degradation, which is relevant for increased longevity and motility.
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Affiliation(s)
- Sylvia Varland
- Department of Biomedicine, University of Bergen, N-5021, Bergen, Norway.
- Department of Biological Sciences, University of Bergen, N-5006, Bergen, Norway.
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada.
| | - Rui Duarte Silva
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139, Faro, Portugal.
- Faculdade de Medicina e Ciências Biomédicas, Universidade do Algarve, 8005-139, Faro, Portugal.
| | - Ine Kjosås
- Department of Biomedicine, University of Bergen, N-5021, Bergen, Norway
| | - Alexandra Faustino
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139, Faro, Portugal
| | - Annelies Bogaert
- VIB-UGent Center for Medical Biotechnology, B-9052, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, B-9052, Ghent, Belgium
| | - Maximilian Billmann
- Department of Computer Science and Engineering, University of Minnesota-Twin Cities, Minneapolis, MN, 55455, USA
- Institute of Human Genetics, University of Bonn, School of Medicine and University Hospital Bonn, D-53127, Bonn, Germany
| | - Hadi Boukhatmi
- Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes 1, CNRS, UMR6290, 35065, Rennes, France
| | - Barbara Kellen
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139, Faro, Portugal
| | - Michael Costanzo
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Adrian Drazic
- Department of Biomedicine, University of Bergen, N-5021, Bergen, Norway
| | - Camilla Osberg
- Department of Biomedicine, University of Bergen, N-5021, Bergen, Norway
| | - Katherine Chan
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Xiang Zhang
- Department of Computer Science and Engineering, University of Minnesota-Twin Cities, Minneapolis, MN, 55455, USA
| | - Amy Hin Yan Tong
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Simonetta Andreazza
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, UK
| | - Juliette J Lee
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, UK
| | - Lyudmila Nedyalkova
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Matej Ušaj
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | | | - Brenda J Andrews
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Jason Moffat
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Program in Genetics & Genome Biology, The Hospital for Sick Children, Toronto, ON, M5G 1×8, Canada
| | - Chad L Myers
- Department of Computer Science and Engineering, University of Minnesota-Twin Cities, Minneapolis, MN, 55455, USA
- Bioinformatics and Computational Biology Graduate Program, University of Minnesota-Twin Cities, Minneapolis, MN, 55455, USA
| | - Kris Gevaert
- VIB-UGent Center for Medical Biotechnology, B-9052, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, B-9052, Ghent, Belgium
| | - Charles Boone
- The Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 3E1, Canada
- RIKEN Centre for Sustainable Resource Science, Wako, Saitama, 351-0106, Japan
| | - Rui Gonçalo Martinho
- Algarve Biomedical Center Research Institute, Universidade do Algarve, 8005-139, Faro, Portugal.
- Departmento de Ciências Médicas, Universidade de Aveiro, 3810-193, Aveiro, Portugal.
- iBiMED - Institute of Biomedicine, Universidade de Aveiro, 3810-193, Aveiro, Portugal.
| | - Thomas Arnesen
- Department of Biomedicine, University of Bergen, N-5021, Bergen, Norway.
- Department of Biological Sciences, University of Bergen, N-5006, Bergen, Norway.
- Department of Surgery, Haukeland University Hospital, N-5021, Bergen, Norway.
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Gao Z, Yang YY, Huang M, Qi TF, Wang H, Wang Y. Targeted Proteomic Analysis of Small GTPases in Radioresistant Breast Cancer Cells. Anal Chem 2022; 94:14925-14930. [PMID: 36264766 PMCID: PMC9869664 DOI: 10.1021/acs.analchem.2c02389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Radiation therapy benefits more than 50% of all cancer patients and cures 40% of them, where ionizing radiation (IR) deposits energy to cells and tissues, thereby eliciting DNA damage and resulting in cell death. Small GTPases are a superfamily of proteins that play critical roles in cell signaling. Several small GTPases, including RAC1, RHOB, and RALA, were previously shown to modulate radioresistance in cancer cells. However, there is no systematic proteomic study on small GTPases that regulate radioresistance in cancer cells. Herein, we applied a high-throughput scheduled multiple-reaction monitoring (MRM) method, along with the use of synthetic stable isotope-labeled (SIL) peptides, to identify differentially expressed small GTPase proteins in two pairs of breast cancer cell lines, MDA-MB-231 and MCF7, and their corresponding radioresistant cell lines. We identified 7 commonly altered small GTPase proteins with over 1.5-fold changes in the two pairs of cell lines. We also discovered ARFRP1 as a novel regulator of radioresistance, where its downregulation promotes radioresistance in breast cancer cells. Together, this represents the first comprehensive investigation about the differential expression of the small GTPase proteome associated with the development of radioresistance in breast cancer cells. Our work also uncovered ARFRP1 as a new target for enhancing radiation sensitivity in breast cancer.
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Affiliation(s)
- Zi Gao
- Department of Chemistry, University of California Riverside, Riverside, California92521-0403, United States
| | - Yen-Yu Yang
- Department of Chemistry, University of California Riverside, Riverside, California92521-0403, United States
| | - Ming Huang
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, California92521-0403, United States
| | - Tianyu F Qi
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, California92521-0403, United States
| | - Handing Wang
- Department of Chemistry, University of California Riverside, Riverside, California92521-0403, United States
| | - Yinsheng Wang
- Department of Chemistry, University of California Riverside, Riverside, California92521-0403, United States
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, California92521-0403, United States
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5
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Li M, Yin C, Zhao F, Liu Y. Copy number variation association studies for sheep tail‐relevant traits in Hulunbuir sheep. Anim Genet 2022; 53:897-900. [DOI: 10.1111/age.13265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 08/26/2022] [Accepted: 08/26/2022] [Indexed: 12/01/2022]
Affiliation(s)
- Mianyan Li
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science and Technology, National Experimental Teaching Demonstration Center of Animal Science Nanjing Agricultural University Nanjing China
- Key Laboratory of Animal Genetics, Breeding and Reproduction (Poultry) of Ministry of Agriculture, Institute of Animal Science Chinese Academy of Agricultural Sciences Beijing China
| | - Chang Yin
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science and Technology, National Experimental Teaching Demonstration Center of Animal Science Nanjing Agricultural University Nanjing China
| | - Fuping Zhao
- Key Laboratory of Animal Genetics, Breeding and Reproduction (Poultry) of Ministry of Agriculture, Institute of Animal Science Chinese Academy of Agricultural Sciences Beijing China
| | - Yang Liu
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science and Technology, National Experimental Teaching Demonstration Center of Animal Science Nanjing Agricultural University Nanjing China
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Yang Y, Basu S, Zhang L. A Bayesian hierarchically structured prior for gene-based association testing with multiple traits in genome-wide association studies. Genet Epidemiol 2022; 46:63-72. [PMID: 34787916 PMCID: PMC8795481 DOI: 10.1002/gepi.22437] [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: 06/24/2021] [Revised: 09/28/2021] [Accepted: 10/18/2021] [Indexed: 02/03/2023]
Abstract
Although genome-wide association studies (GWAS) often collect data on multiple correlated traits for complex diseases, conventional gene-based analysis is usually univariate, and therefore, treating traits as uncorrelated. Multivariate analysis of multiple correlated traits can potentially increase the power to detect genes that affect some or all of these traits. In this study, we propose the multivariate hierarchically structured variable selection (HSVS-M) model, a flexible Bayesian model that tests the association of a gene with multiple correlated traits. With only summary statistics, HSVS-M can account for the correlations among genetic variants and among traits simultaneously and can also estimate the various directions and magnitudes of associations between a gene and multiple traits. Simulation studies show that HSVS-M substantially outperforms competing methods in various scenarios, particularly when variants in a gene are associated with a trait in similar directions and magnitudes. We applied HSVS-M to the summary statistics of a meta-analysis GWAS on four lipid traits from the Global Lipids Genetics Consortium and identified 15 genes that have also been confirmed as risk factors in previous studies.
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Affiliation(s)
- Yi Yang
- Division of Biostatistics, University of Minnesota, Minneapolis, MN 55455, USA,Department of Biostatistics, Columbia University, New York, NY 10032, USA,Correspondence:
| | - Saonli Basu
- Division of Biostatistics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Lin Zhang
- Division of Biostatistics, University of Minnesota, Minneapolis, MN 55455, USA
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Lipid droplets in skeletal muscle during grass snake (Natrix natrix L.) development. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1867:159086. [PMID: 34822977 DOI: 10.1016/j.bbalip.2021.159086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 10/19/2021] [Accepted: 11/15/2021] [Indexed: 11/21/2022]
Abstract
Lipid droplets (LDs) are common organelles observed in Eucaryota. They are multifunctional organelles (involved in lipid storage, metabolism, and trafficking) that originate from endoplasmic reticulum (ER). LDs consist of a neutral lipid core, made up of diacyl- and triacylglycerols (DAGs and TAGs) and cholesterol esters (CEs), surrounded by a phospholipid monolayer and proteins, which are necessary for their structure and dynamics. Here, we report the protein and lipid composition as well as characterization and dynamics of grass snake (Natrix natrix) skeletal muscle LDs at different developmental stages. In the present study, we used detailed morphometric, LC-MS, quantitative lipidomic analyses of LDs isolated from the skeletal muscles of the snake embryos, immunofluorescence, and TEM. Our study also provides a valuable insight concerning the LDs' multifunctionality and ability to interact with a variety of organelles. These LD features are reflected in their proteome composition, which contains scaffold proteins, metabolic enzymes signalling polypeptides, proteins necessary for the formation of docking sites, and many others. We also provide insights into the biogenesis and growth of muscle LDs goes beyond the conventional mechanism based on the synthesis and incorporation of TAGs and LD fusion. We assume that the formation and functioning of grass snake muscle LDs are based on additional mechanisms that have not yet been identified, which could be related to the unique features of reptiles that are manifested in the after-hatching period of life, such as a reptile-specific strategy for energy saving during hibernation.
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8
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Wilhelmi I, Grunwald S, Gimber N, Popp O, Dittmar G, Arumughan A, Wanker EE, Laeger T, Schmoranzer J, Daumke O, Schürmann A. The ARFRP1-dependent Golgi scaffolding protein GOPC is required for insulin secretion from pancreatic β-cells. Mol Metab 2020; 45:101151. [PMID: 33359402 PMCID: PMC7811047 DOI: 10.1016/j.molmet.2020.101151] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 12/13/2022] Open
Abstract
Objective Hormone secretion from metabolically active tissues, such as pancreatic islets, is governed by specific and highly regulated signaling pathways. Defects in insulin secretion are among the major causes of diabetes. The molecular mechanisms underlying regulated insulin secretion are, however, not yet completely understood. In this work, we studied the role of the GTPase ARFRP1 on insulin secretion from pancreatic β-cells. Methods A β-cell-specific Arfrp1 knockout mouse was phenotypically characterized. Pulldown experiments and mass spectrometry analysis were employed to screen for new ARFRP1-interacting proteins. Co-immunoprecipitation assays as well as super-resolution microscopy were applied for validation. Results The GTPase ARFRP1 interacts with the Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC). Both proteins are co-localized at the trans-Golgi network and regulate the first and second phase of insulin secretion by controlling the plasma membrane localization of the SNARE protein SNAP25. Downregulation of both GOPC and ARFRP1 in Min6 cells interferes with the plasma membrane localization of SNAP25 and enhances its degradation, thereby impairing glucose-stimulated insulin release from β-cells. In turn, overexpression of SNAP25 as well as GOPC restores insulin secretion in islets from β-cell-specific Arfrp1 knockout mice. Conclusion Our results identify a hitherto unrecognized pathway required for insulin secretion at the level of trans-Golgi sorting. β-cell specific deletion of the trans-Golgi residing small GTPase ARFRP1 leads to elevated blood glucose levels in mice. GOPC is a newly identified ARFRP1 dependent scaffolding protein. ARFRP1 and GOPC are required for glucose-stimulated insulin secretion from pancreatic β-cells.
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Affiliation(s)
- Ilka Wilhelmi
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany
| | - Stephan Grunwald
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Niclas Gimber
- Advanced Medical Bioimaging Core Facility - AMBIO, Charité-Universitätsmedizin Berlin, Germany
| | - Oliver Popp
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany
| | - Gunnar Dittmar
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany
| | - Anup Arumughan
- Neuroproteomics, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) Berlin, Germany
| | - Erich E Wanker
- Neuroproteomics, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) Berlin, Germany
| | - Thomas Laeger
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany
| | - Jan Schmoranzer
- Advanced Medical Bioimaging Core Facility - AMBIO, Charité-Universitätsmedizin Berlin, Germany
| | - Oliver Daumke
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Annette Schürmann
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany; University of Potsdam, Institute of Nutritional Sciences, Nuthetal, Germany; Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus - Senftenberg, the Brandenburg Medical School Theodor Fontane and the University of Potsdam, Germany.
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9
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Yang F, Li T, Peng Z, Liu Y, Guo Y. The amphipathic helices of Arfrp1 and Arl14 are sufficient to determine subcellular localizations. J Biol Chem 2020; 295:16643-16654. [PMID: 32972971 PMCID: PMC7864062 DOI: 10.1074/jbc.ra120.014999] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/31/2020] [Indexed: 11/06/2022] Open
Abstract
The subcellular localization of Arf family proteins is generally thought to be determined by their corresponding guanine nucleotide exchange factors. By promoting GTP binding, guanine nucleotide exchange factors induce conformational changes of Arf proteins exposing their N-terminal amphipathic helices, which then insert into the membranes to stabilize the membrane association process. Here, we found that the N-terminal amphipathic motifs of the Golgi-localized Arf family protein, Arfrp1, and the endosome- and plasma membrane-localized Arf family protein, Arl14, play critical roles in spatial determination. Exchanging the amphipathic helix motifs between these two Arf proteins causes the switch of their localizations. Moreover, the amphipathic helices of Arfrp1 and Arl14 are sufficient for cytosolic proteins to be localized into a specific cellular compartment. The spatial determination mediated by the Arfrp1 helix requires its binding partner Sys1. In addition, the residues that are required for the acetylation of the Arfrp1 helix and the myristoylation of the Arl14 helix are important for the specific subcellular localization. Interestingly, Arfrp1 and Arl14 are recruited to their specific cellular compartments independent of GTP binding. Our results demonstrate that the amphipathic motifs of Arfrp1 and Arl14 are sufficient for determining specific subcellular localizations in a GTP-independent manner, suggesting that the membrane association and activation of some Arf proteins are uncoupled.
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Affiliation(s)
- Feng Yang
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Tiantian Li
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Ziqing Peng
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Yang Liu
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Yusong Guo
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China; Hong Kong University of Science and Technology Shenzhen Research Institute, Shenzhen, China.
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10
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Zhang G, Zhang Q, Zhu J, Tang J, Nie M. LncRNA ARFRP1 knockdown inhibits LPS-induced the injury of chondrocytes by regulation of NF-κB pathway through modulating miR-15a-5p/TLR4 axis. Life Sci 2020; 261:118429. [PMID: 32931797 DOI: 10.1016/j.lfs.2020.118429] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 09/02/2020] [Accepted: 09/08/2020] [Indexed: 12/15/2022]
Abstract
AIMS Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been reported as the important regulators in osteoarthritis (OA). However, the detailed mechanism is implicated. The aim of this study is to reveal the functional mechanism of lncRNA ARFRP1 and miR-15a-5p in osteoarthritis. MATERIALS AND METHODS The expression level of genes was detected by quantitative real time polymerase chain reaction (qRT-PCR) or western blot assay. Cell Counting Kit-8 (CCK-8) was used to assess cell viability. Cell apoptosis rate was analyzed by flow cytometry analysis. Furthermore, Enzyme-linked immunosorbent assay (ELISA) was performed to measure tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β contents. The interaction between miR-15a-5p and ARFRP1 or Toll-like receptor 4 (TLR4) was predicted by miRcode or PITA, and then confirmed by the dual luciferase reporter assay or pull down assay. Besides, NF-κB-driven luciferase activity was determined using NF-κB luciferase reporter assay. KEY FINDINGS ARFRP1 and TLR4 levels were increased and miR-15a-5p level was decreased in OA cartilage tissues and lipopolysaccharides (LPS)-induced chondrocytes. ARFRP1 knockdown inhibited LPS-induced the injury of chondrocytes. Interestingly, miR-15a-5p downregulated by ARFRP1 negatively modulated TLR4 expression through interaction. ARFRP1 mediated LPS-induced the injury of chondrocytes via regulating miR-15a-5p/TLR4 axis. Furthermore, ARFRP1 exerted function by modulation of NF-κB pathway. SIGNIFICANCE Our findings confirmed that ARFRP1 mediated LPS-induced the injury of chondrocytes through regulating NF-κB pathway by modulation of miR-15a-5p/TLR4 axis, providing theoretical basis for the treatment of OA patients.
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Affiliation(s)
- Guangcheng Zhang
- Department of Orthopedics, Affiliated Hospital of Jiangsu University, Jiangsu, Zhejiang, China
| | - Qing Zhang
- Department of Orthopedics, Affiliated Hospital of Jiangsu University, Jiangsu, Zhejiang, China
| | - Juan Zhu
- Department of Anesthesiology, Affiliated Hospital of Jiangsu University, Jiangsu, Zhejiang, China
| | - Jiazhu Tang
- Department of Orthopedics, Affiliated Hospital of Jiangsu University, Jiangsu, Zhejiang, China
| | - Mingjun Nie
- Department of Orthopedics, Affiliated Hospital of Jiangsu University, Jiangsu, Zhejiang, China.
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11
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Chen Y, Frost S, Khushi M, Cantrill LC, Yu H, Arthur JW, Bright RK, Groblewski GE, Byrne JA. Delayed recruiting of TPD52 to lipid droplets - evidence for a "second wave" of lipid droplet-associated proteins that respond to altered lipid storage induced by Brefeldin A treatment. Sci Rep 2019; 9:9790. [PMID: 31278300 PMCID: PMC6611826 DOI: 10.1038/s41598-019-46156-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Accepted: 06/18/2019] [Indexed: 12/27/2022] Open
Abstract
Tumor protein D52 (TPD52) is amplified and overexpressed in breast and prostate cancers which are frequently characterised by dysregulated lipid storage and metabolism. TPD52 expression increases lipid storage in mouse 3T3 fibroblasts, and co-distributes with the Golgi marker GM130 and lipid droplets (LDs). We examined the effects of Brefeldin A (BFA), a fungal metabolite known to disrupt the Golgi structure, in TPD52-expressing 3T3 cells, and in human AU565 and HMC-1-8 breast cancer cells that endogenously express TPD52. Five-hour BFA treatment reduced median LD numbers, but increased LD sizes. TPD52 knockdown decreased both LD sizes and numbers, and blunted BFA's effects on LD numbers. Following BFA treatment for 1-3 hours, TPD52 co-localised with the trans-Golgi network protein syntaxin 6, but after 5 hours BFA treatment, TPD52 showed increased co-localisation with LDs, which was disrupted by microtubule depolymerising agent nocodazole. BFA treatment also increased perilipin (PLIN) family protein PLIN3 but reduced PLIN2 detection at LDs in TPD52-expressing 3T3 cells, with PLIN3 recruitment to LDs preceding that of TPD52. An N-terminally deleted HA-TPD52 mutant (residues 40-184) almost exclusively targeted to LDs in both vehicle and BFA treated cells. In summary, delayed recruitment of TPD52 to LDs suggests that TPD52 participates in a temporal hierarchy of LD-associated proteins that responds to altered LD packaging requirements induced by BFA treatment.
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Affiliation(s)
- Yuyan Chen
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia.
- The University of Sydney Discipline of Child and Adolescent Health, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia.
| | - Sarah Frost
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia
- The University of Sydney Discipline of Child and Adolescent Health, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia
| | - Matloob Khushi
- Bioinformatics Unit, Children's Medical Research Institute, The University of Sydney, Westmead, NSW, 2145, Australia
- The University of Sydney School of Information Technologies, Darlington, NSW, 2008, Australia
| | - Laurence C Cantrill
- The University of Sydney Discipline of Child and Adolescent Health, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia
- Kids Research Microscope Facility, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia
| | - Hong Yu
- Cell Imaging Facility, Westmead Institute for Medical Research, Westmead, NSW, 2145, Australia
| | - Jonathan W Arthur
- Bioinformatics Unit, Children's Medical Research Institute, The University of Sydney, Westmead, NSW, 2145, Australia
| | - Robert K Bright
- Department of Immunology and Molecular Microbiology and TTUHSC Cancer Center, Texas Tech University Health Sciences Center, Lubbock, Texas, 79430, USA
| | - Guy E Groblewski
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Jennifer A Byrne
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia.
- The University of Sydney Discipline of Child and Adolescent Health, The Children's Hospital at Westmead, Westmead, NSW, 2145, Australia.
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12
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Sztul E, Chen PW, Casanova JE, Cherfils J, Dacks JB, Lambright DG, Lee FJS, Randazzo PA, Santy LC, Schürmann A, Wilhelmi I, Yohe ME, Kahn RA. ARF GTPases and their GEFs and GAPs: concepts and challenges. Mol Biol Cell 2019; 30:1249-1271. [PMID: 31084567 PMCID: PMC6724607 DOI: 10.1091/mbc.e18-12-0820] [Citation(s) in RCA: 149] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 02/26/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022] Open
Abstract
Detailed structural, biochemical, cell biological, and genetic studies of any gene/protein are required to develop models of its actions in cells. Studying a protein family in the aggregate yields additional information, as one can include analyses of their coevolution, acquisition or loss of functionalities, structural pliability, and the emergence of shared or variations in molecular mechanisms. An even richer understanding of cell biology can be achieved through evaluating functionally linked protein families. In this review, we summarize current knowledge of three protein families: the ARF GTPases, the guanine nucleotide exchange factors (ARF GEFs) that activate them, and the GTPase-activating proteins (ARF GAPs) that have the ability to both propagate and terminate signaling. However, despite decades of scrutiny, our understanding of how these essential proteins function in cells remains fragmentary. We believe that the inherent complexity of ARF signaling and its regulation by GEFs and GAPs will require the concerted effort of many laboratories working together, ideally within a consortium to optimally pool information and resources. The collaborative study of these three functionally connected families (≥70 mammalian genes) will yield transformative insights into regulation of cell signaling.
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Affiliation(s)
- Elizabeth Sztul
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, MA 01267
| | - James E. Casanova
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908
| | - Jacqueline Cherfils
- Laboratoire de Biologie et Pharmacologie Appliquée, CNRS and Ecole Normale Supérieure Paris-Saclay, 94235 Cachan, France
| | - Joel B. Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - David G. Lambright
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Amherst, MA 01605
| | - Fang-Jen S. Lee
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan
| | | | - Lorraine C. Santy
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802
| | - Annette Schürmann
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Ilka Wilhelmi
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Marielle E. Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Richard A. Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050
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13
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Cai M, Chen J, Yu C, Xi L, Jiang Q, Wang Y, Wang X. FAM134B promotes adipogenesis by increasing vesicular activity in porcine and 3T3-L1 adipocytes. Biol Chem 2018; 400:523-532. [DOI: 10.1515/hsz-2018-0336] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 10/02/2018] [Indexed: 11/15/2022]
Abstract
Abstract
Family with sequence similarity 134, Member B (FAM134B), is a cis-Golgi transmembrane protein that is known to be necessary for the long-term survival of nociceptive and autonomic ganglion neurons. Recent work has shown that FAM134B plays a pivotal role in autophagy-mediated turnover of endoplasmic reticulum (ER) membranes, tumor inhibition and lipid homeostasis. In this study, we provide mechanistic links between FAM134B and ARF-related protein 1 (ARFRP1) and further show that FAM134B resides in the Golgi apparatus. Here, we found that FAM134B increased lipid accumulation in adipocytes. Transport vehicle number and ADP-ribosylation factor (ARF) family gene expression were also increased by FAM134B overexpression, suggesting that vesicular transport activity enhanced lipid accumulation. ARF-related protein 1 (ARFRP1) is a GTPase that promotes protein trafficking. We show that FAM134B regulates the expression of ARFRP1, and the knockdown of ARFRP1 abolishes enhancement on lipid accumulation caused by FAM134B. In addition, FAM134B upregulates the PAT family protein (PAT), which associates with the lipid droplets (LDs) surface and promotes lipolysis by recruiting adipocyte triglyceride lipase (ATGL). These findings indicate that FAM134B promotes lipid accumulation and adipogenic differentiation by increasing vesicle transport activity in the Golgi apparatus and inhibiting the lipolysis of LDs.
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Affiliation(s)
- Min Cai
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
| | - Jin Chen
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
| | - Caihua Yu
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
| | - Lingling Xi
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
| | - Qin Jiang
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
| | - Yizhen Wang
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
| | - Xinxia Wang
- College of Animal Sciences , Zhejiang University , Zhejiang , P.R. China
- Key Laboratory of Animal Nutrition and Feed Sciences , Ministry of Agriculture , Zhejiang , P.R. China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition , No. 866 Yuhangtang Road , Hangzhou 310058, Zhejiang , P.R. China
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14
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Rödiger M, Werno MW, Wilhelmi I, Baumeier C, Hesse D, Wettschureck N, Offermanns S, Song K, Krauß M, Schürmann A. Adiponectin release and insulin receptor targeting share trans-Golgi-dependent endosomal trafficking routes. Mol Metab 2018; 8:167-179. [PMID: 29203237 PMCID: PMC5985030 DOI: 10.1016/j.molmet.2017.11.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 11/18/2017] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE Intracellular vesicle trafficking maintains cellular structures and functions. The assembly of cargo-laden vesicles at the trans-Golgi network is initiated by the ARF family of small GTPases. Here, we demonstrate the role of the trans-Golgi localized monomeric GTPase ARFRP1 in endosomal-mediated vesicle trafficking of mature adipocytes. METHODS Control (Arfrp1flox/flox) and inducible fat-specific Arfrp1 knockout (Arfrp1iAT-/-) mice were metabolically characterized. In vitro experiments on mature 3T3-L1 cells and primary mouse adipocytes were conducted to validate the impact of ARFRP1 on localization of adiponectin and the insulin receptor. Finally, secretion and transferrin-based uptake and recycling assays were performed with HeLa and HeLa M-C1 cells. RESULTS We identified the ARFRP1-based sorting machinery to be involved in vesicle trafficking relying on the endosomal compartment for cell surface delivery. Secretion of adiponectin from fat depots was selectively reduced in Arfrp1iAT-/- mice, and Arfrp1-depleted 3T3-L1 adipocytes revealed an accumulation of adiponectin in Rab11-positive endosomes. Plasma adiponectin deficiency of Arfrp1iAT-/- mice resulted in deteriorated hepatic insulin sensitivity, increased gluconeogenesis and elevated fasting blood glucose levels. Additionally, the insulin receptor, undergoing endocytic recycling after ligand binding, was less abundant at the plasma membrane of adipocytes lacking Arfrp1. This had detrimental effects on adipose insulin signaling, followed by insufficient suppression of basal lipolytic activity and impaired adipose tissue expansion. CONCLUSIONS Our findings suggest that adiponectin secretion and insulin receptor surface targeting utilize the same post-Golgi trafficking pathways that are essential for an appropriate systemic insulin sensitivity and glucose homeostasis.
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Affiliation(s)
- Maria Rödiger
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Martin W Werno
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Ilka Wilhelmi
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Christian Baumeier
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Deike Hesse
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Nina Wettschureck
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
| | - Stefan Offermanns
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
| | - Kyungyeun Song
- Department of Molecular Pharmacology and Cell Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany.
| | - Michael Krauß
- Department of Molecular Pharmacology and Cell Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany.
| | - Annette Schürmann
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
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15
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Common, low-frequency, and rare genetic variants associated with lipoprotein subclasses and triglyceride measures in Finnish men from the METSIM study. PLoS Genet 2017; 13:e1007079. [PMID: 29084231 PMCID: PMC5679656 DOI: 10.1371/journal.pgen.1007079] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 11/09/2017] [Accepted: 10/16/2017] [Indexed: 12/12/2022] Open
Abstract
Lipid and lipoprotein subclasses are associated with metabolic and cardiovascular diseases, yet the genetic contributions to variability in subclass traits are not fully understood. We conducted single-variant and gene-based association tests between 15.1M variants from genome-wide and exome array and imputed genotypes and 72 lipid and lipoprotein traits in 8,372 Finns. After accounting for 885 variants at 157 previously identified lipid loci, we identified five novel signals near established loci at HIF3A, ADAMTS3, PLTP, LCAT, and LIPG. Four of the signals were identified with a low-frequency (0.005<minor allele frequency [MAF]<0.05) or rare (MAF<0.005) variant, including Arg123His in LCAT. Gene-based associations (P<10-10) support a role for coding variants in LIPC and LIPG with lipoprotein subclass traits. 30 established lipid-associated loci had a stronger association for a subclass trait than any conventional trait. These novel association signals provide further insight into the molecular basis of dyslipidemia and the etiology of metabolic disorders.
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16
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Jiang Y, Xiao P, Shao Q, Qin H, Hu Z, Lei A, Wang J. Metabolic responses to ethanol and butanol in Chlamydomonas reinhardtii. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:239. [PMID: 29075323 PMCID: PMC5646117 DOI: 10.1186/s13068-017-0931-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 10/12/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Microalgae have been demonstrated to be among the most promising phototrophic species for producing renewable biofuels and chemicals. Ethanol and butanol are clean energy sources with good chemical and physical properties as alternatives to gasoline. However, biosynthesis of these two biofuels has not been achieved due to low tolerance of algal cells to ethanol or butanol. RESULTS With an eye to circumventing these problems in the future and engineering the robust alcohol-producing microalgal hosts, we investigated the metabolic responses of the model green alga Chlamydomonas reinhardtii to ethanol and butanol. Using a quantitative proteomics approach with iTRAQ-LC-MS/MS technologies, we detected the levels of 3077 proteins; 827 and 730 of which were differentially regulated by ethanol and butanol, respectively, at three time points. In particular, 41 and 59 proteins were consistently regulated during at least two sampling times. Multiple metabolic processes were affected by ethanol or butanol, and various stress-related proteins, transporters, cytoskeletal proteins, and regulators were induced as the major protection mechanisms against toxicity of the organic solvents. The most highly upregulated butanol response protein was Cre.770 peroxidase. CONCLUSIONS The study is the first comprehensive view of the metabolic mechanisms employed by C. reinhardtii to defend against ethanol or butanol toxicity. Moreover, the proteomic analysis provides a resource for investigating potential gene targets for engineering microalgae to achieve efficient biofuel production.
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Affiliation(s)
- Yongguang Jiang
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Peng Xiao
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Qing Shao
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Huan Qin
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Zhangli Hu
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Anping Lei
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
| | - Jiangxin Wang
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060 People’s Republic of China
- Shenzhen Engineering Laboratory for Marine Algal Biotechnology, Shenzhen, 518060 People’s Republic of China
- Nanshan District Key Lab for Biopolymers and Safety Evaluation, Shenzhen University, Shenzhen, 518060 People’s Republic of China
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17
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Lim YS, Ngo HTT, Lee J, Son K, Park EM, Hwang SB. ADP-ribosylation Factor-related Protein 1 Interacts with NS5A and Regulates Hepatitis C Virus Propagation. Sci Rep 2016; 6:31211. [PMID: 27550144 PMCID: PMC4994002 DOI: 10.1038/srep31211] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 07/08/2016] [Indexed: 12/12/2022] Open
Abstract
The life cycle of hepatitis C virus (HCV) is tightly coupled to the lipid metabolism of host cells. In order to identify host factors involved in HCV propagation, we have previously screened a small interfering RNA (siRNA) library targeting host genes that control lipid metabolism and lipid droplet (LD) formation using cell culture-grown HCV (HCVcc)-infected cells. In this study, we selected and characterized the gene encoding ADP-ribosylation factor-related protein 1 (ARFRP1). ARFRP1 is essential for LD growth and is involved in the regulation of lipolysis. siRNA-mediated knockdown of ARFRP1 significantly inhibited HCV replication in both subgenomic replicon cells and HCVcc-infected cells. ARFRP1 interacted with NS5A and NS5A partially colocalized with LD. Silencing of ARFRP1 abrogated HCV-induced LD growth and viral protein expressions. Moreover, ARFRP1 recruited synaptosomal-associated protein 23 (SNAP23) to sites in close proximity to LDs in HCV-infected cells. Silencing of ARFRP1 ablated relocalization of SNAP23 to LD. These data indicate that HCV regulates ARFRP1 for LD growth to facilitate viral propagation and thus ARFRP1 may be a potential target for antiviral therapy.
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Affiliation(s)
- Yun-Sook Lim
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Huong T T Ngo
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Jihye Lee
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Kidong Son
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Eun-Mee Park
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea.,Korea National Institute of Health, Cheongwon-gun, South Korea
| | - Soon B Hwang
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
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18
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Kamili A, Roslan N, Frost S, Cantrill LC, Wang D, Della-Franca A, Bright RK, Groblewski GE, Straub BK, Hoy AJ, Chen Y, Byrne JA. TPD52 expression increases neutral lipid storage within cultured cells. J Cell Sci 2015; 128:3223-38. [PMID: 26183179 DOI: 10.1242/jcs.167692] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2014] [Accepted: 07/10/2015] [Indexed: 12/12/2022] Open
Abstract
Tumor protein D52 (TPD52) is amplified and/or overexpressed in cancers of diverse cellular origins. Altered cellular metabolism (including lipogenesis) is a hallmark of cancer development, and protein-protein associations between TPD52 and known regulators of lipid storage, and differential TPD52 expression in obese versus non-obese adipose tissue, suggest that TPD52 might regulate cellular lipid metabolism. We found increased lipid droplet numbers in BALB/c 3T3 cell lines stably expressing TPD52, compared with control and TPD52L1-expressing cell lines. TPD52-expressing 3T3 cells showed increased fatty acid storage in triglyceride (from both de novo synthesis and uptake) and formed greater numbers of lipid droplets upon oleic acid supplementation than control cells. TPD52 colocalised with Golgi, but not endoplasmic reticulum (ER), markers and also showed partial colocalisation with lipid droplets coated with ADRP (also known as PLIN2), with a proportion of TPD52 being detected in the lipid droplet fraction. Direct interactions between ADRP and TPD52, but not TPD52L1, were demonstrated using the yeast two-hybrid system, with ADRP-TPD52 interactions confirmed using GST pulldown assays. Our findings uncover a new isoform-specific role for TPD52 in promoting intracellular lipid storage, which might be relevant to TPD52 overexpression in cancer.
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Affiliation(s)
- Alvin Kamili
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Nuruliza Roslan
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia Discipline of Paediatrics and Child Health, University of Sydney, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Sarah Frost
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia Discipline of Paediatrics and Child Health, University of Sydney, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Laurence C Cantrill
- Discipline of Paediatrics and Child Health, University of Sydney, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia Kids Research Institute Microscope Facility, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Dongwei Wang
- Kids Research Institute Microscope Facility, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Austin Della-Franca
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia Discipline of Paediatrics and Child Health, University of Sydney, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Robert K Bright
- Department of Immunology and Molecular Microbiology and TTUHSC Cancer Center, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Guy E Groblewski
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI 53706, USA
| | - Beate K Straub
- Department of General Pathology, Institute of Pathology, Heidelberg 69120, Germany
| | - Andrew J Hoy
- Discipline of Physiology, School of Medical Sciences and Bosch Institute and Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Yuyan Chen
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia Discipline of Paediatrics and Child Health, University of Sydney, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Jennifer A Byrne
- Molecular Oncology Laboratory, Children's Cancer Research Unit, Kids Research Institute, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia Discipline of Paediatrics and Child Health, University of Sydney, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
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19
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Bouchez I, Pouteaux M, Canonge M, Genet M, Chardot T, Guillot A, Froissard M. Regulation of lipid droplet dynamics in Saccharomyces cerevisiae depends on the Rab7-like Ypt7p, HOPS complex and V1-ATPase. Biol Open 2015; 4:764-75. [PMID: 25948753 PMCID: PMC4571102 DOI: 10.1242/bio.20148615] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
It has now been clearly shown that lipid droplets (LDs) play a dynamic role in the cell. This was reinforced by LD proteomics which suggest that a significant number of trafficking proteins are associated with this organelle. Using microscopy, we showed that LDs partly co-localize with the vacuole in S. cerevisiae. Immunoblot experiments confirmed the association of the vacuolar Rab GTPase Rab7-like Ypt7p with LDs. We observed an increase in fatty acid content and LD number in ypt7Δ mutant and also changes in LD morphology and intra LD fusions, revealing a direct role for Ypt7p in LD dynamics. Using co-immunoprecipitation, we isolated potential Ypt7p partners including, Vma13p, the H subunit of the V1 part of the vacuolar (H+) ATPase (V-ATPase). Deletion of the VMA13 gene, as well as deletion of three other subunits of the V1 part of the V-ATPase, also increased the cell fatty acid content and LD number. Mutants of the Homotypic fusion and vacuole protein sorting (HOPS) complex showed similar phenotypes. Here, we demonstrated that LD dynamics and membrane trafficking between the vacuole and LDs are regulated by the Rab7-like Ypt7p and are impaired when the HOPS complex and the V1 domain of the V-ATPase are defective.
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Affiliation(s)
- Isabelle Bouchez
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Marie Pouteaux
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Michel Canonge
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Mélanie Genet
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Thierry Chardot
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
| | - Alain Guillot
- MICALIS PAPPSO, UMR 1319 INRA, Domaine de Vilvert 78352, Jouy-en-Josas cedex, France MICALIS PAPPSO, UMR 1319 AgroParisTech, Domaine de Vilvert 78352, Jouy-en-Josas cedex, France
| | - Marine Froissard
- Institut Jean-Pierre Bourgin IJPB, UMR 1318 INRA, Saclay Plant Sciences, route de St Cyr (RD 10), 78026, Versailles cedex, France Institut Jean-Pierre Bourgin IJPB, UMR 1318 AgroParisTech, route de St Cyr (RD 10), 78026, Versailles cedex, France
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Chu M, Sampath H, Cahana DY, Kahl CA, Somwar R, Cornea A, Roberts CT, Varlamov O. Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes. Mol Biol Cell 2014; 25:4096-105. [PMID: 25298400 PMCID: PMC4263452 DOI: 10.1091/mbc.e14-06-1085] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Real-time fluorescence microscopy is used to investigate the trafficking of metabolizable fluorescent fatty acid in unilocular adipocytes from adipose tissue of nonhuman primates. The study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy. The spatiotemporal dynamics of triglyceride (TG) storage in unilocular adipocytes are not well understood. Here we applied ex vivo technology to study trafficking and metabolism of fluorescent fatty acids in adipose tissue explants. Live imaging revealed multiple cytoplasmic nodules surrounding the large central lipid droplet (cLD) of unilocular adipocytes. Each cytoplasmic nodule harbors a series of closely associated cellular organelles, including micro–lipid droplets (mLDs), mitochondria, and the endoplasmic reticulum. Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG. This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte. This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.
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Affiliation(s)
- Michael Chu
- Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239
| | - Harini Sampath
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR 97239
| | - David Y. Cahana
- Divisions of Diabetes, Obesity, and Metabolism and Developmental and Reproductive Science, Beaverton, OR 97006
| | | | - Romel Somwar
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
| | - Anda Cornea
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR 97006
| | - Charles T. Roberts
- Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239
- Divisions of Diabetes, Obesity, and Metabolism and Developmental and Reproductive Science, Beaverton, OR 97006
| | - Oleg Varlamov
- Divisions of Diabetes, Obesity, and Metabolism and Developmental and Reproductive Science, Beaverton, OR 97006
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Affiliation(s)
- Yusong Guo
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, California 94720-3200;
| | - Daniel W. Sirkis
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, California 94720-3200;
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, California 94720-3200;
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Skeletal muscle perilipin 3 and coatomer proteins are increased following exercise and are associated with fat oxidation. PLoS One 2014; 9:e91675. [PMID: 24632837 PMCID: PMC3954790 DOI: 10.1371/journal.pone.0091675] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 02/14/2014] [Indexed: 12/19/2022] Open
Abstract
Lipid droplet-associated proteins such as perilipin 3 (PLIN3) and coatomer GTPase proteins (GBF1, ARF1, Sec23a, and ARFRP1) are expressed in skeletal muscle but little is known so far as to their regulation of lipolysis. We aimed here to explore the effects of lipolytic stimulation in vitro in primary human myotubes as well as in vivo following an acute exercise bout. In vitro lipolytic stimulation by epinephrine (100 μM) or by a lipolytic cocktail (30 μM palmitate, 4 μM forskolin, and 0.5 μM ionomycin, PFI) resulted in increases in PLIN3 protein content. Coatomer GTPases such as GBF1, ARF1, Sec23a, and ARFRP1 also increased in response to lipolytic stimuli. Furthermore, a long duration endurance exercise bout (20 males; age 24.0±4.5 y; BMI 23.6±1.8 kg/m2) increased PLIN3 protein in human skeletal muscle (p = 0.03) in proportion to ex vivo palmitate oxidation (r = 0.45, p = 0.04) and whole body in vivo fat oxidation (r = 0.52, p = 0.03). Protein content of ARF1 was increased (p = 0.04) while mRNA expression was increased for several other coatomers (GBF1, ARF1, and Sec23a, all p<0.05). These data provide novel observational insight into the possible relationships between lipolysis and PLIN3 along with these coatomoer GTPase proteins in human skeletal muscle.
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Abstract
The ARF-like (ARL) proteins, within the ARF family, are a collection of functionally diverse GTPases that share extensive (>40 %) identity with the ARFs and each other and are assumed to share basic mechanisms of regulation and a very incompletely documented degree of overlapping regulators. At least four ARLs were already present in the last eukaryotic common ancestor, along with one ARF, and these have been expanded to >20 members in mammals. We know little about the majority of these proteins so our review will focus on those about which the most is known, including ARL1, ARL2, ARL3, ARL4s, ARL6, ARL13s, and ARFRP1. From this fragmentary information we extract some generalizations and conclusions regarding the sources and extent of specificity and functions of the ARLs.
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Affiliation(s)
- Alfred Wittinghofer
- Max-Planck-Institute of Molecular Physiology, Dortmund, Nordrhein-Westfalen Germany
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Hesse D, Radloff K, Jaschke A, Lagerpusch M, Chung B, Tailleux A, Staels B, Schürmann A. Hepatic trans-Golgi action coordinated by the GTPase ARFRP1 is crucial for lipoprotein lipidation and assembly. J Lipid Res 2013; 55:41-52. [PMID: 24186947 DOI: 10.1194/jlr.m040089] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The liver is a major organ in whole body lipid metabolism and malfunctioning can lead to various diseases including dyslipidemia, fatty liver disease, and type 2 diabetes. Triglycerides and cholesteryl esters are packed in the liver as very low density lipoproteins (VLDLs). Generation of these lipoproteins is initiated in the endoplasmic reticulum and further maturation likely occurs in the Golgi. ADP-ribosylation factor-related protein 1 (ARFRP1) is a small trans-Golgi-associated guanosine triphosphatase (GTPase) that regulates protein sorting and is required for chylomicron lipidation and assembly in the intestine. Here we show that the hepatocyte-specific deletion of Arfrp1 (Arfrp1(liv-/-)) results in impaired VLDL lipidation leading to reduced plasma triglyceride levels in the fasted state as well as after inhibition of lipoprotein lipase activity by Triton WR-1339. In addition, the concentration of ApoC3 that comprises 40% of protein mass of secreted VLDLs is markedly reduced in the plasma of Arfrp1(liv-/-) mice but accumulates in the liver accompanied by elevated triglycerides. Fractionation of Arfrp1(liv-/-) liver homogenates reveals more ApoB48 and a lower concentration of triglycerides in the Golgi compartments than in the corresponding fractions from control livers. In conclusion, ARFRP1 and the Golgi apparatus play an important role in lipoprotein maturation in the liver by influencing lipidation and assembly of proteins to the lipid particles.
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Affiliation(s)
- Deike Hesse
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, D-14558 Nuthetal, Germany
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COPI buds 60-nm lipid droplets from reconstituted water-phospholipid-triacylglyceride interfaces, suggesting a tension clamp function. Proc Natl Acad Sci U S A 2013; 110:13244-9. [PMID: 23901109 DOI: 10.1073/pnas.1307685110] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Intracellular trafficking between organelles is achieved by coat protein complexes, coat protomers, that bud vesicles from bilayer membranes. Lipid droplets are protected by a monolayer and thus seem unsuitable targets for coatomers. Unexpectedly, coat protein complex I (COPI) is required for lipid droplet targeting of some proteins, suggesting a possible direct interaction between COPI and lipid droplets. Here, we find that COPI coat components can bud 60-nm triacylglycerol nanodroplets from artificial lipid droplet (LD) interfaces. This budding decreases phospholipid packing of the monolayer decorating the mother LD. As a result, hydrophobic triacylglycerol molecules become more exposed to the aqueous environment, increasing LD surface tension. In vivo, this surface tension increase may prime lipid droplets for reactions with neighboring proteins or membranes. It provides a mechanism fundamentally different from transport vesicle formation by COPI, likely responsible for the diverse lipid droplet phenotypes associated with depletion of COPI subunits.
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Demignot S, Beilstein F, Morel E. Triglyceride-rich lipoproteins and cytosolic lipid droplets in enterocytes: key players in intestinal physiology and metabolic disorders. Biochimie 2013; 96:48-55. [PMID: 23871915 DOI: 10.1016/j.biochi.2013.07.009] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 07/08/2013] [Indexed: 02/07/2023]
Abstract
During the post-prandial phase, intestinal triglyceride-rich lipoproteins (TRL) i.e. chylomicrons are the main contributors to the serum lipid level, which is linked to coronary artery diseases. Hypertriglyceridemia can originate from decreased clearance or increased production of TRL. During lipid absorption, enterocytes produce and secrete chylomicrons and transiently store lipid droplets (LDs) in the cytosol. The dynamic fluctuation of triglycerides in cytosolic LDs suggests that they contribute to TRL production and may thus control the length and amplitude of the post-prandial hypertriglyceridemia. In this review, we will describe the recent advances in the characterization of enterocytic LDs. The role of LDs in chylomicron production and secretion as well as potential previously unsuspected functions in the metabolism of vitamins, steroids and prostaglandins and in viral infection will also be discussed.
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Affiliation(s)
- Sylvie Demignot
- Université Pierre et Marie Curie, UMR S 872, Centre de Recherche des Cordeliers, Paris, France; Inserm, U 872, Paris, France; Ecole Pratique des Hautes Etudes, Laboratoire de Pharmacologie Cellulaire et Moléculaire, Paris, France; Université Paris Descartes, UMR S 872, Paris, France; Institut de Cardiométabolisme et Nutrition (ICAN), Paris, France.
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Abstract
LDs (lipid droplets) carrying TAG (triacylglycerol) and cholesteryl esters are emerging as dynamic cellular organelles that are generated in nearly every cell. They play a key role in lipid and membrane homoeostasis. Abnormal LD dynamics are associated with the pathophysiology of many metabolic diseases, such as obesity, diabetes, atherosclerosis, fatty liver and even cancer. Chylomicrons, stable droplets also consisting of TAG and cholesterol are generated in the intestinal epithelium to transport exogenous (dietary) lipids after meals from the small intestine to tissues for degradation. Defective chylomicron formation is responsible for inherited lipoprotein deficiencies, including abetalipoproteinaemia, hypobetalipoproteinaemia and chylomicron retention disease. These are disorders sharing characteristics such as fat malabsorption, low levels of circulating lipids and fat-soluble vitamins, failure to thrive in early childhood, ataxic neuropathy and visual impairment. Thus understanding the molecular mechanisms governing the dynamics of LDs and chylomicrons, namely, their biogenesis, growth, maintenance and degradation, will not only clarify their molecular role, but might also provide additional indications to treatment of metabolic diseases. In this review, we highlight the role of two small GTPases [ARFRP1 (ADP-ribosylation factor related protein 1) and ARL1 (ADP-ribosylation factor-like 1)] and their downstream targets acting on the trans-Golgi (Golgins and Rab proteins) on LD and chylomicron formation.
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Pulido MR, Rabanal-Ruiz Y, Almabouada F, Díaz-Ruiz A, Burrell MA, Vázquez MJ, Castaño JP, Kineman RD, Luque RM, Diéguez C, Vázquez-Martínez R, Malagón MM. Nutritional, hormonal, and depot-dependent regulation of the expression of the small GTPase Rab18 in rodent adipose tissue. J Mol Endocrinol 2013; 50:19-29. [PMID: 23093555 DOI: 10.1530/jme-12-0140] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
There is increasing evidence that proteins associated with lipid droplets (LDs) play a key role in the coordination of lipid storage and mobilization in adipocytes. The small GTPase, RAB18, has been recently identified as a novel component of the protein coat of LDs and proposed to play a role in both β-adrenergic stimulation of lipolysis and insulin-induced lipogenesis in 3T3-L1 adipocytes. In order to better understand the role of Rab18 in the regulation of lipid metabolism in adipocytes, we evaluated the effects of age, fat location, metabolic status, and hormonal milieu on Rab18 expression in rodent white adipose tissue (WAT). Rab18 mRNA was undetectable at postnatal day 15 (P15), but reached adult levels by P45, in both male and female rats. In adult rats, Rab18 immunolocalized around LDs, as well as within the cytoplasm of mature adipocytes. A weak Rab18 signal was also detected in the stromal-vascular fraction of WAT. In mice, fasting significantly increased, though with a distinct time-course pattern, Rab18 mRNA and protein levels in visceral and subcutaneous WAT. The expression of Rab18 was also increased in visceral and subcutaneous WAT of obese mice (diet-induced, ob/ob, and New Zealand obese mice) compared with lean controls. Rab18 expression in rats was unaltered by castration, adrenalectomy, or GH deficiency but was increased by hypophysectomy, as well as hypothyroidism. When viewed together, our results suggest the participation of Rab18 in the regulation of lipid processing in adipose tissue under both normal and pathological conditions.
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Affiliation(s)
- Marina R Pulido
- Department of Cell Biology, Physiology and Immunology, Instituto Maimónides de Investigación Biomédica de Córdoba, University of Córdoba/Hospital Universitario Reina Sofia, Edificio Severo-Ochoa, Pl. 3, Campus Univ. de Rabanales, E-14014 Córdoba, Spain
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Abstract
Objective Genetics plays a large role in atherosclerosis susceptibility in humans and mice. We attempted to confirm previously determined mouse atherosclerosis‐associated loci and use bioinformatics and transcriptomics to create a catalog of candidate atherosclerosis modifier genes at these loci. Methods and Results A strain intercross was performed between AKR and DBA/2 mice on the apoE−/− background generating 166 F2 progeny. Using the phenotype log10 of the aortic root lesion area, we identified 3 suggestive atherosclerosis quantitative trait loci (Ath QTLs). When combined with our prior strain intercross, we confirmed 3 significant Ath QTLs on chromosomes 2, 15, and 17, with combined logarithm of odds scores of 5.9, 5.3, and 5.6, respectively, which each met the genome‐wide 5% false discovery rate threshold. We identified all of the protein coding differences between these 2 mouse strains within the Ath QTL intervals. Microarray gene expression profiling was performed on macrophages and endothelial cells from this intercross to identify expression QTLs (eQTLs), the loci that are associated with variation in the expression levels of specific transcripts. Cross tissue eQTLs and macrophage eQTLs that replicated from a prior strain intercross were identified. These bioinformatic and eQTL analyses produced a comprehensive list of candidate genes that may be responsible for the Ath QTLs. Conclusions Replication studies for clinical traits as well as gene expression traits are worthwhile in identifying true versus false genetic associations. We have replicated 3 loci on mouse chromosomes 2, 15, and 17 that are associated with atherosclerosis. We have also identified protein coding differences and multiple replicated eQTLs, which may be useful in the identification of atherosclerosis modifier genes.
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Affiliation(s)
- Jeffrey Hsu
- Department of Molecular Medicine, Cleveland Clinic, Lerner College of Medicine, Case Western Reserve University, Cleveland, OH, USA
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Guo Y, Zanetti G, Schekman R. A novel GTP-binding protein-adaptor protein complex responsible for export of Vangl2 from the trans Golgi network. eLife 2013; 2:e00160. [PMID: 23326640 PMCID: PMC3539332 DOI: 10.7554/elife.00160] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 10/18/2012] [Indexed: 01/03/2023] Open
Abstract
Planar cell polarity (PCP) requires the asymmetric sorting of distinct signaling
receptors to distal and proximal surfaces of polarized epithelial cells. We have
examined the transport of one PCP signaling protein, Vangl2, from the
trans Golgi network (TGN) in mammalian cells. Using siRNA
knockdown experiments, we find that the GTP-binding protein, Arfrp1, and the clathrin
adaptor complex 1 (AP-1) are required for Vangl2 transport from the TGN. In contrast,
TGN export of Frizzled 6, which localizes to the opposing epithelial surface from
Vangl2, does not depend on Arfrp1 or AP-1. Mutagenesis studies identified a YYXXF
sorting signal in the C-terminal cytosolic domain of Vangl2 that is required for
Vangl2 traffic and interaction with the μ subunit of AP-1. We propose that
Arfrp1 exposes a binding site on AP-1 that recognizes the Vangl2 sorting motif for
capture into a transport vesicle destined for the proximal surface of a polarized
epithelial cell. DOI:http://dx.doi.org/10.7554/eLife.00160.001 Most cells in multicellular organisms possess a property known as polarity that is
reflected, in part, in the organization of the cell surface into distinct domains.
One well-known axis in epithelial cells, such as those in the skin, divides the cell
into an apical domain, which faces out, and a basal domain, which faces the
underlying tissue. These cells rely on the distribution of structural components
inside the cell, or within the cell membrane, to tell the difference between these
two directions. Epithelial cells also possess a second type of polarity, planar cell
polarity, that ensures that cells adjacent to each other in the plane parallel to the
skin tissue are oriented correctly with respect to each other during development.
This ensures, in turn, that hairs, scales, feathers and so on are all aligned. All eukaryotic cells sort and process proteins within an organelle called the Golgi
apparatus, and proteins that are required at a specific destination within the cell,
such as the cell surface membrane, carry specific molecular sorting signals that act
as address labels to convey the protein into and within the secretory pathway. As one
of these proteins moves through the Golgi apparatus, its sorting signals are
recognized by coat proteins, such as clathrin, that subsequently form a vesicle
around it. The assembly of this vesicle is initiated by an enzyme from the Arf
family, but the enzyme must first undergo a conformational change (by exchanging a
molecule of GDP for one of GTP) before formation can begin. The resulting vesicle can
then be sent on its way to the address indicated by its Golgi-to-cell-surface sorting
signal. These sorting signals also help to establish planar cell polarity in cells by
ensuring that proteins called signaling receptors are distributed asymmetrically
within the cell membrane. Guo et al. have now examined the mechanism behind the asymmetric sorting of two
proteins that are involved in planar cell polarity: Vangl2 and Frizzled 6. In an
effort to understand why these proteins are localized to opposite surfaces of
epithelial cells, Guo et al. used genetic techniques to reduce the expression of
Golgi-localized Arf proteins in epithelial cell cultures. They found that knockdown
of a protein called Arfrp1 caused Vangl2 to accumulate in the last station of the
Golgi complex instead of being transported to the cell surface membrane. Then, using
a technique called affinity chromatography, they demonstrated that a coat protein
called the clathrin adaptor complex (AP-1) had to be present for the formation of
vesicles around Vangl2. Moreover, disrupting AP-1 and Arfrp1 did not prevent Frizzled
6 being transported to the cell surface membrane. This suggests that cells use
several distinct adaptor proteins and coat complexes to ensure that proteins from the
Golgi apparatus go to specific locations on the cell surface and, thus, help to
establish planar cell polarity. DOI:http://dx.doi.org/10.7554/eLife.00160.002
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Affiliation(s)
- Yusong Guo
- Department of Molecular and Cell Biology , Howard Hughes Medical Institute, University of California-Berkeley , Berkeley , United States
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31
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Mullican SE, Tomaru T, Gaddis CA, Peed LC, Sundaram A, Lazar MA. A novel adipose-specific gene deletion model demonstrates potential pitfalls of existing methods. Mol Endocrinol 2012. [PMID: 23192980 DOI: 10.1210/me.2012-1267] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Adipose-specific gene deletion in mice is crucial in determining gene function in adipocyte homeostasis and the development of obesity. We noted 100% mortality when the Hdac3 gene was conditionally deleted using Fabp4-Cre mice, the most commonly used model of adipose-targeted Cre recombinase. However, this surprising result was not reproduced using other models of adipose targeting of Cre, including a novel Retn-Cre mouse. These findings underscore the need for caution when interpreting data obtained using Fabp4-Cre mice and should encourage the use of additional or alternative adipose-targeting Cre mouse models before drawing conclusions about in vivo adipocyte-specific functions.
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Affiliation(s)
- Shannon E Mullican
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, and The Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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East MP, Bowzard JB, Dacks JB, Kahn RA. ELMO domains, evolutionary and functional characterization of a novel GTPase-activating protein (GAP) domain for Arf protein family GTPases. J Biol Chem 2012; 287:39538-53. [PMID: 23014990 DOI: 10.1074/jbc.m112.417477] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human family of ELMO domain-containing proteins (ELMODs) consists of six members and is defined by the presence of the ELMO domain. Within this family are two subclassifications of proteins, based on primary sequence conservation, protein size, and domain architecture, deemed ELMOD and ELMO. In this study, we used homology searching and phylogenetics to identify ELMOD family homologs in genomes from across eukaryotic diversity. This demonstrated not only that the protein family is ancient but also that ELMOs are potentially restricted to the supergroup Opisthokonta (Metazoa and Fungi), whereas proteins with the ELMOD organization are found in diverse eukaryotes and thus were likely the form present in the last eukaryotic common ancestor. The segregation of the ELMO clade from the larger ELMOD group is consistent with their contrasting functions as unconventional Rac1 guanine nucleotide exchange factors and the Arf family GTPase-activating proteins, respectively. We used unbiased, phylogenetic sorting and sequence alignments to identify the most highly conserved residues within the ELMO domain to identify a putative GAP domain within the ELMODs. Three independent but complementary assays were used to provide an initial characterization of this domain. We identified a highly conserved arginine residue critical for both the biochemical and cellular GAP activity of ELMODs. We also provide initial evidence of the function of human ELMOD1 as an Arf family GAP at the Golgi. These findings provide the basis for the future study of the ELMOD family of proteins and a new avenue for the study of Arf family GTPases.
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Affiliation(s)
- Michael P East
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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GTPase ARFRP1 is essential for normal hepatic glycogen storage and insulin-like growth factor 1 secretion. Mol Cell Biol 2012; 32:4363-74. [PMID: 22927645 DOI: 10.1128/mcb.00522-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The GTPase ADP-ribosylation factor-related protein 1 (ARFRP1) is located at the trans-Golgi compartment and regulates the recruitment of Arf-like 1 (ARL1) and its effector golgin-245 to this compartment. Here, we show that liver-specific knockout of Arfrp1 in the mouse (Arfrp1(liv-/-)) resulted in early growth retardation, which was associated with reduced hepatic insulin-like growth factor 1 (IGF1) secretion. Accordingly, suppression of Arfrp1 in primary hepatocytes resulted in a significant reduction of IGF1 release. However, the hepatic secretion of IGF-binding protein 2 (IGFBP2) was not affected in the absence of ARFRP1. In addition, Arfrp1(liv-/-) mice exhibited decreased glucose transport into the liver, leading to a 50% reduction of glycogen stores as well as a marked retardation of glycogen storage after fasting and refeeding. These abnormalities in glucose metabolism were attributable to reduced protein levels and intracellular retention of the glucose transporter GLUT2 in Arfrp1(liv-/-) livers. As a consequence of impaired glucose uptake into the liver, the expression levels of carbohydrate response element binding protein (ChREBP), a transcription factor regulated by glucose concentration, and its target genes (glucokinase and pyruvate kinase) were markedly reduced. Our data indicate that ARFRP1 in the liver is involved in the regulation of IGF1 secretion and GLUT2 sorting and is thereby essential for normal growth and glycogen storage.
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Murphy DJ. The dynamic roles of intracellular lipid droplets: from archaea to mammals. PROTOPLASMA 2012; 249:541-85. [PMID: 22002710 DOI: 10.1007/s00709-011-0329-7] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 09/28/2011] [Indexed: 05/02/2023]
Abstract
During the past decade, there has been a paradigm shift in our understanding of the roles of intracellular lipid droplets (LDs). New genetic, biochemical and imaging technologies have underpinned these advances, which are revealing much new information about these dynamic organelles. This review takes a comparative approach by examining recent work on LDs across the whole range of biological organisms from archaea and bacteria, through yeast and Drosophila to mammals, including humans. LDs probably evolved originally in microorganisms as temporary stores of excess dietary lipid that was surplus to the immediate requirements of membrane formation/turnover. LDs then acquired roles as long-term carbon stores that enabled organisms to survive episodic lack of nutrients. In multicellular organisms, LDs went on to acquire numerous additional roles including cell- and organism-level lipid homeostasis, protein sequestration, membrane trafficking and signalling. Many pathogens of plants and animals subvert their host LD metabolism as part of their infection process. Finally, malfunctions in LDs and associated proteins are implicated in several degenerative diseases of modern humans, among the most serious of which is the increasingly prevalent constellation of pathologies, such as obesity and insulin resistance, which is associated with metabolic syndrome.
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Affiliation(s)
- Denis J Murphy
- Division of Biological Sciences, University of Glamorgan, Cardiff, CF37 4AT, UK.
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Saka HA, Valdivia R. Emerging roles for lipid droplets in immunity and host-pathogen interactions. Annu Rev Cell Dev Biol 2012; 28:411-37. [PMID: 22578141 DOI: 10.1146/annurev-cellbio-092910-153958] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lipid droplets (LDs) are neutral lipid storage organelles ubiquitous to eukaryotic cells. It is increasingly recognized that LDs interact extensively with other organelles and that they perform functions beyond passive lipid storage and lipid homeostasis. One emerging function for LDs is the coordination of immune responses, as these organelles participate in the generation of prostaglandins and leukotrienes, which are important inflammation mediators. Similarly, LDs are also beginning to be recognized as playing a role in interferon responses and in antigen cross presentation. Not surprisingly, there is emerging evidence that many pathogens, including hepatitis C and Dengue viruses, Chlamydia, and Mycobacterium, target LDs during infection either for nutritional purposes or as part of an anti-immunity strategy. We here review recent findings that link LDs to the regulation and execution of immune responses in the context of host-pathogen interactions.
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Affiliation(s)
- Hector Alex Saka
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina 27710, USA
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Jaschke A, Chung B, Hesse D, Kluge R, Zahn C, Moser M, Petzke KJ, Brigelius-Flohé R, Puchkov D, Koepsell H, Heeren J, Joost HG, Schürmann A. The GTPase ARFRP1 controls the lipidation of chylomicrons in the Golgi of the intestinal epithelium. Hum Mol Genet 2012; 21:3128-42. [PMID: 22505585 PMCID: PMC3384381 DOI: 10.1093/hmg/dds140] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The uptake and processing of dietary lipids by the small intestine is a multistep process that involves several steps including vesicular and protein transport. The GTPase ADP-ribosylation factor-related protein 1 (ARFRP1) controls the ARF-like 1 (ARL1)-mediated Golgi recruitment of GRIP domain proteins which in turn bind several Rab-GTPases. Here, we describe the essential role of ARFRP1 and its interaction with Rab2 in the assembly and lipidation of chylomicrons in the intestinal epithelium. Mice lacking Arfrp1 specifically in the intestine (Arfrp1vil−/−) exhibit an early post-natal growth retardation with reduced plasma triacylglycerol and free fatty acid concentrations. Arfrp1vil−/− enterocytes as well as Arfrp1 mRNA depleted Caco-2 cells absorbed fatty acids normally but secreted chylomicrons with a markedly reduced triacylglycerol content. In addition, the release of apolipoprotein A-I (ApoA-I) was dramatically decreased, and ApoA-I accumulated in the Arfrp1vil−/− epithelium, where it predominantly co-localized with Rab2. The release of chylomicrons from Caco-2 was markedly reduced after the suppression of Rab2, ARL1 and Golgin-245. Thus, the GTPase ARFRP1 and its downstream proteins are required for the lipidation of chylomicrons and the assembly of ApoA-I to these particles in the Golgi of intestinal epithelial cells.
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Affiliation(s)
- Alexander Jaschke
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, D-14558 Nuthetal, Germany
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Interaction between the triglyceride lipase ATGL and the Arf1 activator GBF1. PLoS One 2011; 6:e21889. [PMID: 21789191 PMCID: PMC3138737 DOI: 10.1371/journal.pone.0021889] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 06/14/2011] [Indexed: 02/07/2023] Open
Abstract
The Arf1 exchange factor GBF1 (Golgi Brefeldin A resistance factor 1) and its effector COPI are required for delivery of ATGL (adipose triglyceride lipase) to lipid droplets (LDs). Using yeast two hybrid, co-immunoprecipitation in mammalian cells and direct protein binding approaches, we report here that GBF1 and ATGL interact directly and in cells, through multiple contact sites on each protein. The C-terminal region of ATGL interacts with N-terminal domains of GBF1, including the catalytic Sec7 domain, but not with full-length GBF1 or its entire N-terminus. The N-terminal lipase domain of ATGL (called the patatin domain) interacts with two C-terminal domains of GBF1, HDS (Homology downstream of Sec7) 1 and HDS2. These two domains of GBF1 localize to lipid droplets when expressed alone in cells, but not to the Golgi, unlike the full-length GBF1 protein, which localizes to both. We suggest that interaction of GBF1 with ATGL may be involved in the membrane trafficking pathway mediated by GBF1, Arf1 and COPI that contributes to the localization of ATGL to lipid droplets.
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Jacquier N, Choudhary V, Mari M, Toulmay A, Reggiori F, Schneiter R. Lipid droplets are functionally connected to the endoplasmic reticulum in Saccharomyces cerevisiae. J Cell Sci 2011; 124:2424-37. [PMID: 21693588 DOI: 10.1242/jcs.076836] [Citation(s) in RCA: 297] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells store metabolic energy in the form of neutral lipids that are deposited within lipid droplets (LDs). In this study, we examine the biogenesis of LDs and the transport of integral membrane proteins from the endoplasmic reticulum (ER) to newly formed LDs. In cells that lack LDs, otherwise LD-localized membrane proteins are homogenously distributed in the ER membrane. Under these conditions, transcriptional induction of a diacylglycerol acyltransferase that catalyzes the formation of the storage lipid triacylglycerol (TAG), Lro1, is sufficient to drive LD formation. Newly formed LDs originate from the ER membrane where they become decorated by marker proteins. Induction of LDs by expression of the second TAG-synthesizing integral membrane protein, Dga1, reveals that Dga1 itself moves from the ER membrane to concentrate on LDs. Photobleaching experiments (FRAP) indicate that relocation of membrane proteins from the ER to LDs is independent of temperature and energy, and thus not mediated by classical vesicular transport routes. LD-localized membrane proteins are homogenously distributed at the perimeter of LDs, they are free to move over the LD surface and can even relocate back into the ER, indicating that they are not restricted to specialized sites on LDs. These observations indicate that LDs are functionally connected to the ER membrane and that this connection allows the efficient partitioning of membrane proteins between the two compartments.
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Affiliation(s)
- Nicolas Jacquier
- Department of Biology, Division of Biochemistry, University of Fribourg, 1700 Fribourg, Switzerland
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ARF family G proteins and their regulators: roles in membrane transport, development and disease. Nat Rev Mol Cell Biol 2011; 12:362-75. [PMID: 21587297 PMCID: PMC3245550 DOI: 10.1038/nrm3117] [Citation(s) in RCA: 669] [Impact Index Per Article: 51.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ADP-ribosylation factor (ARF) family of guanine-nucleotide-binding (G) proteins, including the ARF proteins, ARF-like (ARL) proteins and SAR1, regulates membrane traffic and organelle structure, and each family member is regulated through a cycle of GTP binding and GTP hydrolysis, which activate and inactivate, respectively, the G protein. Traditionally, ARFs have been characterized for their immediate effects in the recruitment of coat proteins to drive cargo sorting, the recruitment of enzymes that can alter membrane lipid composition and the regulation of cytoskeletal factors. Now, new roles for ARFs have been discovered at the Golgi complex, for example in driving lipid transport. ARL proteins are also being increasingly linked to coordination of trafficking with cytoskeletal processes, for example during ciliogenesis. There is particular interest in the mechanisms that control recruitment of the ARF guanine nucleotide exchange factors (GEFs) that mediate GTP binding to ARFs and, in the case of the cytohesin (also known as ARNO) GEF, membrane recruitment is coupled to relief of autoinhibition. GEFs such as cytohesin may also participate in a cascade of activation between particular pairs of ARFs. Traditionally, G protein signalling has been viewed as a linear pathway, with the GDP-bound form of an ARF protein being inactive; however, more recent studies have highlighted novel roles for these GDP-bound forms and have also shown that GEFs and GTPase-activating proteins (GAPs) themselves can engage in distinct signalling responses through scaffolding functions.
The ADP-ribosylation factor (ARF) and ARF-like (ARL) family of G proteins, which are known to regulate membrane traffic and organelle structure, are emerging as regulators of diverse processes, including lipid and cytoskeletal transport. Although traditionally viewed as part of a linear signalling pathway, ARFs and their regulators must now be considered to exist within functional networks, in which both the 'inactive' ARF and the regulators themselves can mediate distinct effects. Members of the ADP-ribosylation factor (ARF) family of guanine-nucleotide-binding (G) proteins, including the ARF-like (ARL) proteins and SAR1, regulate membrane traffic and organelle structure by recruiting cargo-sorting coat proteins, modulating membrane lipid composition, and interacting with regulators of other G proteins. New roles of ARF and ARL proteins are emerging, including novel functions at the Golgi complex and in cilia formation. Their function is under tight spatial control, which is mediated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) that catalyse GTP exchange and hydrolysis, respectively. Important advances are being gained in our understanding of the functional networks that are formed not only by the GEFs and GAPs themselves but also by the inactive forms of the ARF proteins.
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Fujimoto T, Parton RG. Not just fat: the structure and function of the lipid droplet. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a004838. [PMID: 21421923 DOI: 10.1101/cshperspect.a004838] [Citation(s) in RCA: 335] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Lipid droplets (LDs) are independent organelles that are composed of a lipid ester core and a surface phospholipid monolayer. Recent studies have revealed many new proteins, functions, and phenomena associated with LDs. In addition, a number of diseases related to LDs are beginning to be understood at the molecular level. It is now clear that LDs are not an inert store of excess lipids but are dynamically engaged in various cellular functions, some of which are not directly related to lipid metabolism. Compared to conventional membrane organelles, there are still many uncertainties concerning the molecular architecture of LDs and how each function is placed in a structural context. Recent findings and remaining questions are discussed.
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Affiliation(s)
- Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Japan.
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Beller M, Thiel K, Thul PJ, Jäckle H. Lipid droplets: a dynamic organelle moves into focus. FEBS Lett 2010; 584:2176-82. [PMID: 20303960 DOI: 10.1016/j.febslet.2010.03.022] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 03/15/2010] [Accepted: 03/16/2010] [Indexed: 11/17/2022]
Abstract
Lipid droplets (LDs) were perceived as static storage deposits, which passively participate in the energy homeostasis of both cells and entire organisms. However, this view has changed recently after the realization of a complex and highly dynamic LD proteome. The proteome contains key components of the fat mobilization system and proteins that suggest LD interactions with a variety of cell organelles, including the endoplasmic reticulum, mitochondria and peroxisomes. The study of LD cell biology, including cross-talk with other organelles, the trafficking of LDs in the cell and regulatory events involving the LD coat proteins is now on the verge of leaving its infancy and unfolds that LDs are highly dynamic cellular organelles.
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Affiliation(s)
- Mathias Beller
- Max-Planck-Institut für biophysikalische Chemie, Abteilung für molekulare Entwicklungsbiologie, Göttingen, Germany.
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Altered GLUT4 trafficking in adipocytes in the absence of the GTPase Arfrp1. Biochem Biophys Res Commun 2010; 394:896-903. [PMID: 20230794 DOI: 10.1016/j.bbrc.2010.03.059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 03/10/2010] [Indexed: 12/16/2022]
Abstract
The GTPase ADP-ribosylation factor related protein 1 (ARFRP1) controls the recruitment of proteins such as golgin-245 to the trans-Golgi. ARFRP1 is highly expressed in adipose tissues in which the insulin-sensitive glucose transporter GLUT4 is processed through the Golgi to a specialized endosomal compartment, the insulin-responsive storage compartment from which it is translocated to the plasma membrane in response to a stimulation of cells by insulin. In order to examine the role of ARFRP1 for GLUT4 targeting, subcellular distribution of GLUT4 was investigated in adipose tissue specific Arfrp1 knockout (Arfrp1(ad)(-/-)) mice. Immunohistochemical and ultrastructural studies of brown adipocytes demonstrated an abnormal trans-Golgi in Arfrp1(ad)(-/-) adipocytes. In addition, in Arfrp1(ad)(-/-) adipocytes GLUT4 protein accumulated at the plasma membrane rather than being sequestered in an intracellular compartment. A similar missorting of GLUT4 was produced by siRNA-mediated knockdown of Arfrp1 in 3T3-L1 adipocytes which was associated with significantly elevated uptake of deoxyglucose under basal conditions. Thus, Arfrp1 appears to be involved in sorting of GLUT4.
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