1
|
Dempsey JL, Ioannou GN, Carr RM. Mechanisms of Lipid Droplet Accumulation in Steatotic Liver Diseases. Semin Liver Dis 2023; 43:367-382. [PMID: 37799111 DOI: 10.1055/a-2186-3557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
The steatotic diseases of metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), and chronic hepatitis C (HCV) account for the majority of liver disease prevalence, morbidity, and mortality worldwide. While these diseases have distinct pathogenic and clinical features, dysregulated lipid droplet (LD) organelle biology represents a convergence of pathogenesis in all three. With increasing understanding of hepatocyte LD biology, we now understand the roles of LD proteins involved in these diseases but also how genetics modulate LD biology to either exacerbate or protect against the phenotypes associated with steatotic liver diseases. Here, we review the history of the LD organelle and its biogenesis and catabolism. We also review how this organelle is critical not only for the steatotic phenotype of liver diseases but also for their advanced phenotypes. Finally, we summarize the latest attempts and challenges of leveraging LD biology for therapeutic gain in steatotic diseases. In conclusion, the study of dysregulated LD biology may lead to novel therapeutics for the prevention of disease progression in the highly prevalent steatotic liver diseases of MASLD, ALD, and HCV.
Collapse
Affiliation(s)
- Joseph L Dempsey
- Division of Gastroenterology, Department of Medicine, School of Medicine, University of Washington, Seattle, Washington
| | - George N Ioannou
- Division of Gastroenterology, Department of Medicine, School of Medicine, University of Washington, Seattle, Washington
- Division of Gastroenterology, Veterans Affairs Puget Sound Healthcare System Seattle, Washington
| | - Rotonya M Carr
- Division of Gastroenterology, Department of Medicine, School of Medicine, University of Washington, Seattle, Washington
| |
Collapse
|
2
|
Yang D, Wang X, Zhang L, Fang Y, Zheng Q, Liu X, Yu W, Chen S, Ying J, Hua F. Lipid metabolism and storage in neuroglia: role in brain development and neurodegenerative diseases. Cell Biosci 2022; 12:106. [PMID: 35831869 PMCID: PMC9277953 DOI: 10.1186/s13578-022-00828-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 06/05/2022] [Indexed: 11/13/2022] Open
Abstract
The importance of neuroglia in maintaining normal brain function under physiological and pathological conditions has been supported by growing evidence in recent years. The most important issues regarding glial metabolism and function include the cooperation between glial populations and neurons, morphological and functional changes in pathological states, and the role in the onset and progression of neurodegenerative diseases. Although lipid accumulation and further lipid droplet production in neurodegenerative disease brain models have been observed for a long time, the dynamic development of brain lipid droplet research in recent years suggests its role in the development and progression of neurodegenerative diseases was previously underestimated. First recognized as organelles of lipid storage, lipid droplets (LDs) have emerged as an important organelle in metabolic diseases, inflammation, and host defense. Dynamic changes in lipid metabolism within neurons and glial cells resulting in lipid accumulation and lipid droplet formation are present in brain models of various neurodegenerative diseases, yet their role in the brain remains largely unexplored. This paper first reviews the metabolism and accumulation of several major lipids in the brain and discusses the regulation of lipid accumulation in different types of brain cells. We explore the potential role of intracellular lipid accumulation in the pathogenesis of neurodegeneration, starting from lipid metabolism and LDs biogenesis in glial cells, and discuss several pathological factors that promote lipid droplet formation, mainly focusing on oxidative stress, energy metabolism and glial cell-neuron coupling, which are closely related to the etiology and progression of neurodegenerative diseases. Finally, the directions and challenges of intracellular lipid metabolism in glial cells in neurodegeneration are discussed.
Collapse
|
3
|
Qin ZL, Yao QF, Ren H, Zhao P, Qi ZT. Lipid Droplets and Their Participation in Zika Virus Infection. Int J Mol Sci 2022; 23:ijms232012584. [PMID: 36293437 PMCID: PMC9604050 DOI: 10.3390/ijms232012584] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/11/2022] [Accepted: 10/14/2022] [Indexed: 11/23/2022] Open
Abstract
Lipid droplets (LDs) are highly conserved and dynamic intracellular organelles. Their functions are not limited to serving as neutral lipid reservoirs; they also participate in non-energy storage functions, such as cell lipid metabolism, protection from cell stresses, maintaining protein homeostasis, and regulating nuclear function. During a Zika virus (ZIKV) infection, the viruses hijack the LDs to provide energy and lipid sources for viral replication. The co-localization of ZIKV capsid (C) protein with LDs supports its role as a virus replication platform and a key compartment for promoting the generation of progeny virus particles. However, in view of the multiple functions of LDs, their role in ZIKV infection needs further elucidation. Here, we review the basic mechanism of LD biogenesis and biological functions and discuss how ZIKV infection utilizes these effects of LDs to facilitate virus replication, along with the future application strategy of developing new antiviral drugs based on the interaction of ZIKV with LDs.
Collapse
|
4
|
Sánchez-Álvarez M, Del Pozo MÁ, Bosch M, Pol A. Insights Into the Biogenesis and Emerging Functions of Lipid Droplets From Unbiased Molecular Profiling Approaches. Front Cell Dev Biol 2022; 10:901321. [PMID: 35756995 PMCID: PMC9213792 DOI: 10.3389/fcell.2022.901321] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/17/2022] [Indexed: 11/30/2022] Open
Abstract
Lipid droplets (LDs) are spherical, single sheet phospholipid-bound organelles that store neutral lipids in all eukaryotes and some prokaryotes. Initially conceived as relatively inert depots for energy and lipid precursors, these highly dynamic structures play active roles in homeostatic functions beyond metabolism, such as proteostasis and protein turnover, innate immunity and defense. A major share of the knowledge behind this paradigm shift has been enabled by the use of systematic molecular profiling approaches, capable of revealing and describing these non-intuitive systems-level relationships. Here, we discuss these advances and some of the challenges they entail, and highlight standing questions in the field.
Collapse
Affiliation(s)
- Miguel Sánchez-Álvarez
- Cell and Developmental Biology Area, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Miguel Ángel Del Pozo
- Cell and Developmental Biology Area, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Marta Bosch
- Lipid Trafficking and Disease Group, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Biomedical Sciences, Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain
| | - Albert Pol
- Lipid Trafficking and Disease Group, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Biomedical Sciences, Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| |
Collapse
|
5
|
Lipid metabolism and neutrophil function. Cell Immunol 2022; 377:104546. [DOI: 10.1016/j.cellimm.2022.104546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/12/2022] [Accepted: 05/19/2022] [Indexed: 11/22/2022]
|
6
|
Huang W, Gao F, Zhang Y, Chen T, Xu C. Lipid Droplet-Associated Proteins in Cardiomyopathy. ANNALS OF NUTRITION AND METABOLISM 2021; 78:1-13. [PMID: 34856540 DOI: 10.1159/000520122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 10/08/2021] [Indexed: 11/19/2022]
Abstract
BACKGROUND The heart requires a high rate of fatty-acid oxidation (FAO) to meet its energy needs. Neutral lipids are the main source of energy for the heart and are stored in lipid droplets (LDs), which are cytosolic organelles that primarily serve to store neutral lipids and regulate cellular lipid metabolism. LD-associated proteins (LDAPs) are proteins either located on the surface of the LDs or reside in the cytosol and contribute to lipid metabolism. Therefore, abnormal cardiac lipid accumulation or FAO can alter the redox state of the heart, resulting in cardiomyopathy, a group of diseases that negatively affect the myocardial function, thereby leading to heart failure and even cardiac death. SUMMARY LDs, along with LDAPs, are pivotal for modulating heart lipid homeostasis. The proper cardiac development and the maintenance of its normal function depend largely on lipid homeostasis regulated by LDs and LDAPs. Overexpression or deletion of specific LDAPs can trigger myocardial dysfunction and may contribute to the development of cardiomyopathy. Extensive connections and interactions may also exist between LDAPs. Key Message: In this review, the various mechanisms involved in LDAP-mediated regulation of lipid metabolism, the association between cardiac development and lipid metabolism, as well as the role of LDAPs in cardiomyopathy progression are discussed.
Collapse
Affiliation(s)
- Weiwei Huang
- Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.,Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Fei Gao
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Yuting Zhang
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Tianhui Chen
- Department of Ophthalmology and Vision Science, Eye and ENT Hospital of Fudan University, Shanghai, China.,Key Laboratory of Myopia of State Health Ministry, and Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
| | - Chen Xu
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| |
Collapse
|
7
|
Li B, Song S, Wei X, Tang G, Wang C. Activation of microlipophagy during early infection of insect hosts by Metarhizium robertsii. Autophagy 2021; 18:608-623. [PMID: 34130590 DOI: 10.1080/15548627.2021.1943179] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The requirement of macroautophagic/autophagic machinery for filamentous fungal development and pathogenicity has been recognized, but the underlying effects and mechanisms remain elusive. The insect pathogenic fungus Metarhizium robertsii infects hosts by cuticular penetration through the formation of the infection structure appressoria. Here, we show that autophagic fluxes were highly activated during the appressorial formation of M. robertsii. Genome-wide deletion of the autophagy-related genes and insect bioassays identified 10 of 23 encoded MrATG genes with requirements for topical fungal infection of insect hosts. Besides the defect in forming appressoria on insects (two null mutants), these virulence-reduced mutants were largely impaired in penetrating cellophane membrane and insect cuticles, suggesting their failures in generating proper appressorium turgor. We found that the conidial storage of lipid droplets (LDs) had no obvious difference between strains, but autophagic LD degradation was impaired in different mutants. After induction of cell autophagy by nitrogen starvation, we found that LD entry into vacuoles was unaffected in the selected mutant cells with potential failures in forming autophagosomes. The finding therefore reveals a microlipophagy machinery employed in this fungus and that the direct engulfment of LDs occurs without inhibition by the downstream defective lipolysis. Our data first unveil the activation and contribution of microlipophagy to fungal infection biology. The obtained technique may benefit future detection of microlipophagy in different organisms by examining vacuolar or lysosomal engulfment of LDs in core autophagic gene deletion mutants.
Collapse
Affiliation(s)
- Bing Li
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuangxiu Song
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuefei Wei
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guirong Tang
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Chengshu Wang
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| |
Collapse
|
8
|
Garcia EJ, Liao PC, Tan G, Vevea JD, Sing CN, Tsang CA, McCaffery JM, Boldogh IR, Pon LA. Membrane dynamics and protein targets of lipid droplet microautophagy during ER stress-induced proteostasis in the budding yeast, Saccharomyces cerevisiae. Autophagy 2020. [PMID: 33021864 DOI: 10.1080/15548627.2020.1826691.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022] Open
Abstract
Our previous studies reveal a mechanism for lipid droplet (LD)-mediated proteostasis in the endoplasmic reticulum (ER) whereby unfolded proteins that accumulate in the ER in response to lipid imbalance-induced ER stress are removed by LDs and degraded by microlipophagy (µLP), autophagosome-independent LD uptake into the vacuole (the yeast lysosome). Here, we show that dithiothreitol- or tunicamycin-induced ER stress also induces µLP and identify an unexpected role for vacuolar membrane dynamics in this process. All stressors studied induce vacuolar fragmentation prior to µLP. Moreover, during µLP, fragmented vacuoles fuse to form cup-shaped structures that encapsulate and ultimately take up LDs. Our studies also indicate that proteins of the endosome sorting complexes required for transport (ESCRT) are upregulated, required for µLP, and recruited to LDs, vacuolar membranes, and sites of vacuolar membrane scission during µLP. We identify possible target proteins for LD-mediated ER proteostasis. Our live-cell imaging studies reveal that one potential target (Nup159) localizes to punctate structures that colocalizes with LDs 1) during movement from ER membranes to the cytosol, 2) during microautophagic uptake into vacuoles, and 3) within the vacuolar lumen. Finally, we find that mutations that inhibit LD biogenesis, homotypic vacuolar membrane fusion or ESCRT function inhibit stress-induced autophagy of Nup159 and other ER proteins. Thus, we have obtained the first direct evidence that LDs and µLP can mediate ER stress-induced ER proteostasis, and identified direct roles for ESCRT and vacuolar membrane fusion in that process.
Collapse
Affiliation(s)
- Enrique J Garcia
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Pin-Chao Liao
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Gary Tan
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Jason D Vevea
- HHMI and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin, USA
| | - Cierra N Sing
- Institute of Human Nutrition, Columbia University, New York, NY, USA
| | - Catherine A Tsang
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD, USA
| | - Istvan R Boldogh
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Liza A Pon
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| |
Collapse
|
9
|
Garcia EJ, Liao PC, Tan G, Vevea JD, Sing CN, Tsang CA, McCaffery JM, Boldogh IR, Pon LA. Membrane dynamics and protein targets of lipid droplet microautophagy during ER stress-induced proteostasis in the budding yeast, Saccharomyces cerevisiae. Autophagy 2020; 17:2363-2383. [PMID: 33021864 PMCID: PMC8496710 DOI: 10.1080/15548627.2020.1826691] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Our previous studies reveal a mechanism for lipid droplet (LD)-mediated proteostasis in the endoplasmic reticulum (ER) whereby unfolded proteins that accumulate in the ER in response to lipid imbalance-induced ER stress are removed by LDs and degraded by microlipophagy (µLP), autophagosome-independent LD uptake into the vacuole (the yeast lysosome). Here, we show that dithiothreitol- or tunicamycin-induced ER stress also induces µLP and identify an unexpected role for vacuolar membrane dynamics in this process. All stressors studied induce vacuolar fragmentation prior to µLP. Moreover, during µLP, fragmented vacuoles fuse to form cup-shaped structures that encapsulate and ultimately take up LDs. Our studies also indicate that proteins of the endosome sorting complexes required for transport (ESCRT) are upregulated, required for µLP, and recruited to LDs, vacuolar membranes, and sites of vacuolar membrane scission during µLP. We identify possible target proteins for LD-mediated ER proteostasis. Our live-cell imaging studies reveal that one potential target (Nup159) localizes to punctate structures that colocalizes with LDs 1) during movement from ER membranes to the cytosol, 2) during microautophagic uptake into vacuoles, and 3) within the vacuolar lumen. Finally, we find that mutations that inhibit LD biogenesis, homotypic vacuolar membrane fusion or ESCRT function inhibit stress-induced autophagy of Nup159 and other ER proteins. Thus, we have obtained the first direct evidence that LDs and µLP can mediate ER stress-induced ER proteostasis, and identified direct roles for ESCRT and vacuolar membrane fusion in that process.
Collapse
Affiliation(s)
- Enrique J Garcia
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Pin-Chao Liao
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Gary Tan
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Jason D Vevea
- HHMI and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin, USA
| | - Cierra N Sing
- Institute of Human Nutrition, Columbia University, New York, NY, USA
| | - Catherine A Tsang
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD, USA
| | - Istvan R Boldogh
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Liza A Pon
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| |
Collapse
|
10
|
Madeira JB, Matos GS, Messias LS, Bozaquel-Morais BL, Masuda CA, Montero-Lomeli M. Induction of triacylglycerol synthesis in yeast by cell cycle arrest. FEMS Yeast Res 2019; 19:5462652. [PMID: 30985885 DOI: 10.1093/femsyr/foz030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 04/13/2019] [Indexed: 12/13/2022] Open
Abstract
In this study, we found that cell cycle arrest induced by alpha-factor mating pheromone (G1), hydroxyurea (S) or nocodazole (G2/M) was associated to increased lipid droplet (LD) content. To identify novel cell cycle genes involved in LD homeostasis, we screened a deletion library for strains with altered LD levels. Among the mutants related to mitotic cell cycle, we found 24 hits that displayed a significantly higher LD content. Ontology mapping showed that neither a biological process nor a specific cell cycle phase was enriched among the hits. We decided to further study the role of SWI4 on LD homeostasis as it is involved in G1/S transition, a stage where lipolysis is active. The high LD content of swi4Δ mutant was not due to inhibition of lipolysis, but due to an increase in triacylglycerol (TAG) synthesis. In addition, deletion of the AMP kinase gene SNF1 or inhibition of TORC1 activity, both known regulators of LD homeostasis, further increased the LD content of a swi4Δ mutant. These findings highlight a role of the cell cycle regulator SWI4 in the coordination of lipid metabolism which is independent of the TORC1 and SNF1/AMPK pathways.
Collapse
Affiliation(s)
- Juliana B Madeira
- Instituto de Bioquimica Médica Leoplodo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, cep 21941-902, Rio de Janeiro, Rio de Janeiro Brazil
| | - Gabriel S Matos
- Instituto de Bioquimica Médica Leoplodo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, cep 21941-902, Rio de Janeiro, Rio de Janeiro Brazil
| | - Laryssa S Messias
- Instituto de Bioquimica Médica Leoplodo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, cep 21941-902, Rio de Janeiro, Rio de Janeiro Brazil
| | - Bruno L Bozaquel-Morais
- Instituto de Bioquimica Médica Leoplodo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, cep 21941-902, Rio de Janeiro, Rio de Janeiro Brazil
| | - Claudio A Masuda
- Instituto de Bioquimica Médica Leoplodo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, cep 21941-902, Rio de Janeiro, Rio de Janeiro Brazil
| | - Monica Montero-Lomeli
- Instituto de Bioquimica Médica Leoplodo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, cep 21941-902, Rio de Janeiro, Rio de Janeiro Brazil
| |
Collapse
|
11
|
Geltinger F, Tevini J, Briza P, Geiser A, Bischof J, Richter K, Felder T, Rinnerthaler M. The transfer of specific mitochondrial lipids and proteins to lipid droplets contributes to proteostasis upon stress and aging in the eukaryotic model system Saccharomyces cerevisiae. GeroScience 2019; 42:19-38. [PMID: 31676965 PMCID: PMC7031196 DOI: 10.1007/s11357-019-00103-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 09/11/2019] [Indexed: 01/12/2023] Open
Abstract
Originally Lipid droplets (LDs) were considered as being droplets for lipid storage only. Increasing evidence, however, demonstrates that LDs fulfill a pleiotropy of additional functions. Among them is the modulation of protein as well as lipid homeostasis. Under unfavorable pro-oxidative conditions, proteins can form aggregates which may exceed the overall proteolytic capacity of the proteasome. After stress termination LDs can adjust and support the removal of these aggregates. Additionally, LDs interact with mitochondria, specifically take over certain proteins and thus prevent apoptosis. LDs, which are loaded with these harmful proteins, are subsequently eliminated via lipophagy. Recently it was demonstrated that this autophagic process is a modulator of longevity. LDs do not only eliminate potentially dangerous proteins, but they are also able to prevent lipotoxicity by storing specific lipids. In the present study we used the model organism Saccharomyces cerevisiae to compare the proteome as well as lipidome of mitochondria and LDs under different conditions: replicative aging, stress and apoptosis. In this context we found an accumulation of proteins at LDs, supporting the role of LDs in proteostasis. Additionally, the composition of main lipid classes such as phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols, phosphatidylglycerols, triacylglycerols, ceramides, phosphatidic acids and ergosterol of LDs and mitochondria changed during stress conditions and aging.
Collapse
Affiliation(s)
- Florian Geltinger
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - Julia Tevini
- Department of Laboratory Medicine, Paracelsus Medical University, Salzburg, Austria
| | - Peter Briza
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - Amrito Geiser
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - Johannes Bischof
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - Klaus Richter
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - Thomas Felder
- Department of Laboratory Medicine, Paracelsus Medical University, Salzburg, Austria.
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria.
| | - Mark Rinnerthaler
- Department of Biosciences, University of Salzburg, Salzburg, Austria.
| |
Collapse
|
12
|
Pevalová Z, Pevala V, Blunsom NJ, Tahotná D, Kotrasová V, Holič R, Pokorná L, Bauer JA, Kutejová E, Cockcroft S, Griač P. Yeast phosphatidylinositol transfer protein Pdr17 does not require high affinity phosphatidylinositol binding for its cellular function. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:1412-1421. [DOI: 10.1016/j.bbalip.2019.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 07/09/2019] [Indexed: 11/28/2022]
|
13
|
Abstract
Lipid droplets (LDs), important organelles for energy storage and involved in the development of metabolic disorders, are extremely dynamic and interact with many other cellular compartments to orchestrate lipid metabolism. Little is known about how these organelle contacts are changed according to cellular needs and functions under different metabolic and pathological conditions and which proteins regulate this. Here, we summarize recent exciting discoveries about the reorganization of organelle contacts in steatotic liver, including the identification of novel LD contact site proteins in cell lines and in animals. We also discuss state of the art proteomics workflows that enable the characterization of LD-organelle contacts and tethering proteins and give an outlook how this can inform obesity research.
Collapse
Affiliation(s)
- Natalie Krahmer
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Munich-Neuherberg, Germany.,Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Matthias Mann
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany.,Faculty of Health Sciences, NNF Center for Protein Research, University of Copenhagen, Denmark
| |
Collapse
|
14
|
Control of Drosophila Growth and Survival by the Lipid Droplet-Associated Protein CG9186/Sturkopf. Cell Rep 2019; 26:3726-3740.e7. [DOI: 10.1016/j.celrep.2019.02.110] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 05/08/2018] [Accepted: 02/27/2019] [Indexed: 12/20/2022] Open
|
15
|
Bhutada G, Kavšček M, Hofer F, Gogg-Fassolter G, Schweiger M, Darnhofer B, Kordiš D, Birner-Gruenberger R, Natter K. Characterization of a lipid droplet protein from Yarrowia lipolytica that is required for its oleaginous phenotype. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:1193-1205. [DOI: 10.1016/j.bbalip.2018.07.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/26/2018] [Accepted: 07/21/2018] [Indexed: 10/28/2022]
|
16
|
Liu Y, Xu S, Zhang C, Zhu X, Hammad MA, Zhang X, Christian M, Zhang H, Liu P. Hydroxysteroid dehydrogenase family proteins on lipid droplets through bacteria, C. elegans, and mammals. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:881-894. [DOI: 10.1016/j.bbalip.2018.04.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 04/18/2018] [Accepted: 04/21/2018] [Indexed: 02/08/2023]
|
17
|
Bui Q, Sherma J, Hines JK. Using High Performance Thin Layer Chromatography-Densitometry to Study the Influence of the Prion [ RNQ+] and Its Determinant Prion Protein Rnq1 on Yeast Lipid Profiles. SEPARATIONS 2018; 5:6. [PMID: 30003084 PMCID: PMC6039194 DOI: 10.3390/separations5010006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The baker's yeast Saccharomyces cerevisiae harbors multiple prions that allow for the creation of heterogeneity within otherwise clonal cell populations. However, in many cases, the consequences of prion infection are entirely unclear. Predictions of prion-induced changes in cell physiology are complicated by pleotropic effects, and detection is often limited to relatively insensitive cell growth assays that may obscure many physiological changes. We previously showed that silica gel high performance thin-layer chromatography-densitometry (HPTLC) can be used to empirically determine prion-induced changes in lipid content in yeast. Here, we conduct pair-wise quantifications of the relative levels of free sterols, free fatty acids, and triacylglycerols [petroleum ether-diethyl ether-glacial acetic acid (80:20:1, v/v/v) mobile phase and phosphomolybdic acid (PMA) detection reagent]; steryl esters, methyl esters, and squalene [hexane-petroleum ether-diethyl ether-glacial acetic acid (50:20:5:1, v/v/v/v) and PMA]; and phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol (chloroform-diethyl ether-acetic acid (65:25:4.5, v/v/v) and cupric sulfate-phosphoric acid) in otherwise clonal prion-infected ([RNQ+]) and prion-free ([rnq-]) cells in both stationary- and logarithmic-growth phases. We detected multiple statistically significant differences between prion-infected and prion-free cells that varied by growth phase, confirming our pr evious observations that prions exert distinct influences on cell physiology between stationary- and log-phase growth. We also found significant differences between cells expressing or lacking the Rnq1 protein which forms the [RNQ+] prion, providing new clues to the as yet unresolved normal biological function of this prion-forming protein. This investigation further emphasizes the utility of HPTLC-densitometry to empirically determine the effects of prions and other presumed innocuous gene deletions on lipid content in yeast, and we expect that additional analyses will continue to resolve the physiological effects of prion infection.
Collapse
Affiliation(s)
- Quang Bui
- Department of Chemistry, Lafayette College, Easton, PA 18042, USA
| | - Joseph Sherma
- Department of Chemistry, Lafayette College, Easton, PA 18042, USA
| | - Justin K. Hines
- Department of Chemistry, Lafayette College, Easton, PA 18042, USA
| |
Collapse
|
18
|
Abstract
Lipid droplets (LDs) are ubiquitous organelles that store neutral lipids for energy or membrane synthesis and act as hubs for metabolic processes. Cells generate LDs de novo, converting cells to emulsions with LDs constituting the dispersed oil phase in the aqueous cytoplasm. Here we review our current view of LD biogenesis. We present a model of LD formation from the ER in distinct steps and highlight the biology of proteins that govern this biophysical process. Areas of incomplete knowledge are identified, as are connections with physiology and diseases linked to alterations in LD biology.
Collapse
Affiliation(s)
- Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115; , .,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142.,Howard Hughes Medical Institute, Boston, Massachusetts 02115
| | - Jeeyun Chung
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115; , .,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Robert V Farese
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115; , .,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142
| |
Collapse
|
19
|
Welte MA, Gould AP. Lipid droplet functions beyond energy storage. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1260-1272. [PMID: 28735096 PMCID: PMC5595650 DOI: 10.1016/j.bbalip.2017.07.006] [Citation(s) in RCA: 331] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/17/2017] [Accepted: 07/17/2017] [Indexed: 02/07/2023]
Abstract
Lipid droplets are cytoplasmic organelles that store neutral lipids and are critically important for energy metabolism. Their function in energy storage is firmly established and increasingly well characterized. However, emerging evidence indicates that lipid droplets also play important and diverse roles in the cellular handling of lipids and proteins that may not be directly related to energy homeostasis. Lipid handling roles of droplets include the storage of hydrophobic vitamin and signaling precursors, and the management of endoplasmic reticulum and oxidative stress. Roles of lipid droplets in protein handling encompass functions in the maturation, storage, and turnover of cellular and viral polypeptides. Other potential roles of lipid droplets may be connected with their intracellular motility and, in some cases, their nuclear localization. This diversity highlights that lipid droplets are very adaptable organelles, performing different functions in different biological contexts. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
Collapse
Affiliation(s)
- Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY, United States.
| | | |
Collapse
|
20
|
Lipid droplets accumulation and other biochemical changes induced in the fungal pathogen Ustilago maydis under nitrogen-starvation. Arch Microbiol 2017; 199:1195-1209. [PMID: 28550409 DOI: 10.1007/s00203-017-1388-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 04/28/2017] [Accepted: 05/16/2017] [Indexed: 10/19/2022]
Abstract
In many organisms, the growth under nitrogen-deprivation or a poor nitrogen source impacts on the carbon flow distribution and causes accumulation of neutral lipids, which are stored as lipid droplets (LDs). Efforts are in progress to find the mechanism of LDs synthesis and degradation, and new organisms capable of accumulating large amounts of lipids for biotechnological applications. In this context, when Ustilago maydis was cultured in the absence of a nitrogen source, there was a large accumulation of lipid bodies containing mainly triacylglycerols. The most abundant fatty acids in lipid bodies at the stationary phase were palmitic, linoleic, and oleic acids, and they were synthesized de novo by the fatty-acid synthase. In regard to the production of NADPH for the synthesis of fatty acids, the cytosolic NADP+-dependent isocitrate dehydrogenase and the glucose-6-phosphate and 6-phosphogluconate dehydrogenases couple showed the highest specific activities, with a lower activity of the malic enzyme. The ATP-citrate lyase activity was not detected in any of the culture conditions, which points to a different mechanism for the transfer of acetyl-CoA into the cytosol. Protein and RNA contents decreased when U. maydis was grown without a nitrogen source. Due to the significant accumulation of triacylglycerols and the particular composition of fatty acids, U. maydis can be considered an alternative model for biotechnological applications.
Collapse
|
21
|
Meyers A, Chourey K, Weiskittel TM, Pfiffner S, Dunlap JR, Hettich RL, Dalhaimer P. The protein and neutral lipid composition of lipid droplets isolated from the fission yeast, Schizosaccharomyces pombe. J Microbiol 2017; 55:112-122. [PMID: 28120187 DOI: 10.1007/s12275-017-6205-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 10/04/2016] [Accepted: 10/20/2016] [Indexed: 12/17/2022]
Abstract
Lipid droplets consist of a core of neutral lipids surrounded by a phospholipid monolayer with bound proteins. Much of the information on lipid droplet function comes from proteomic and lipodomic studies that identify the components of droplets isolated from organisms throughout the phylogenetic tree. Here, we add to that important inventory by reporting lipid droplet factors from the fission yeast, Schizosaccharomyces pombe. Unique to this study was the fact that cells were cultured in three different environments: 1) late log growth phase in glucose-based media, 2) stationary phase in glucosebased media, and 3) late log growth phase in media containing oleic acid. We confirmed colocalization of major factors with lipid droplets using live-cell fluorescent microscopy. We also analyzed droplets from each of the three conditions for sterol ester (SE) and triacylglycerol (TAG) content, along with their respective fatty acid compositions. We identified a previously undiscovered lipid droplet protein, Vip1p, which affects droplet size distribution. The results provide further insight into the workings of these ubiquitous organelles.
Collapse
Affiliation(s)
- Alex Meyers
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996-2200, USA
| | - Karuna Chourey
- Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Taylor M Weiskittel
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996-2200, USA
| | - Susan Pfiffner
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, USA
| | - John R Dunlap
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, USA.,Advanced Microscopy and Imaging Center, University of Tennessee, Knoxville, TN, 37996, USA
| | | | - Paul Dalhaimer
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996-2200, USA. .,Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, USA. .,Institute of Biomedical Engineering, University of Tennessee, Knoxville, TN, 37996, USA.
| |
Collapse
|
22
|
Abstract
Lipid droplets are the universal cellular organelles for the transient or long-term storage of lipids. The number, size and composition of lipid droplets vary greatly within cells in a homogenous population as well as in different cell types. The variability of intracellular lipid-storage organelles reflects the diversification of lipid droplet composition and function. Lipid droplet diversification results, for example, in two cellular lipid droplet populations that are prone to diminish and grow, respectively. The aberrant accumulation or depletion of lipids are hallmarks or causes of various human pathologies. Thus, a better understanding of the origins of lipid droplet diversification is not only a fascinating cell biology question but also potentially serves to improve comprehension of pathologies that entail the accumulation of lipids. This Commentary covers the lipid droplet life cycle and highlights the early steps during lipid droplet biogenesis, which we propose to be the potential driving forces of lipid droplet diversification.
Collapse
Affiliation(s)
- Abdou Rachid Thiam
- Laboratoire de Physique Statistique, École Normale Supérieure, PSL Research University; Université Paris Diderot Sorbonne Paris-Cité; Sorbonne Universités UPMC Univ Paris 06; CNRS; 24 rue Lhomond, Paris 75005, France
| | - Mathias Beller
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany .,Systems Biology of Lipid Metabolism, Heinrich Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany
| |
Collapse
|
23
|
Kolkhof P, Werthebach M, van de Venn A, Poschmann G, Chen L, Welte M, Stühler K, Beller M. A Luciferase-fragment Complementation Assay to Detect Lipid Droplet-associated Protein-Protein Interactions. Mol Cell Proteomics 2016; 16:329-345. [PMID: 27956707 DOI: 10.1074/mcp.m116.061499] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 11/10/2016] [Indexed: 12/18/2022] Open
Abstract
A critical challenge for all organisms is to carefully control the amount of lipids they store. An important node for this regulation is the protein coat present at the surface of lipid droplets (LDs), the intracellular organelles dedicated to lipid storage. Only limited aspects of this regulation are understood so far. For the probably best characterized case, the regulation of lipolysis in mammals, some of the major protein players have been identified, and it has been established that this process crucially depends on an orchestrated set of protein-protein interactions. Proteomic analysis has revealed that LDs are associated with dozens, if not hundreds, of different proteins, most of them poorly characterized, with even fewer data regarding which of them might physically interact. To comprehensively understand the mechanism of lipid storage regulation, it will likely be essential to define the interactome of LD-associated proteins.Previous studies of such interactions were hampered by technical limitations. Therefore, we have developed a split-luciferase based protein-protein interaction assay and test for interactions among 47 proteins from Drosophila and from mouse. We confirmed previously described interactions and identified many new ones. In 1561 complementation tests, we assayed for interactions among 487 protein pairs of which 92 (19%) resulted in a successful luciferase complementation. These results suggest that a prominent fraction of the LD-associated proteome participates in protein-protein interactions.In targeted experiments, we analyzed the two proteins Jabba and CG9186 in greater detail. Jabba mediates the sequestration of histones to LDs. We successfully applied our split luciferase complementation assay to learn more about this function as we were e.g. able to map the interaction between Jabba and histones. For CG9186, expression levels affect the positioning of LDs. Here, we reveal the ubiquitination of CG9186, and link this posttranslational modification to LD cluster induction.
Collapse
Affiliation(s)
- Petra Kolkhof
- From the ‡Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Duesseldorf, Germany
| | - Michael Werthebach
- From the ‡Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Duesseldorf, Germany.,§Systems Biology of Lipid metabolism, Heinrich Heine University, Duesseldorf, Germany
| | - Anna van de Venn
- From the ‡Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Duesseldorf, Germany.,§Systems Biology of Lipid metabolism, Heinrich Heine University, Duesseldorf, Germany
| | - Gereon Poschmann
- ¶Molecular Proteomics Laboratory, Institute for Molecular Medicine, Heinrich Heine University, Duesseldorf, Germany.,‖Biomedical Research Center (BMFZ), Heinrich Heine University, Duesseldorf, Germany
| | - Lili Chen
- **Department of Biology, University of Rochester, Rochester, New York
| | - Michael Welte
- **Department of Biology, University of Rochester, Rochester, New York
| | - Kai Stühler
- ¶Molecular Proteomics Laboratory, Institute for Molecular Medicine, Heinrich Heine University, Duesseldorf, Germany.,‖Biomedical Research Center (BMFZ), Heinrich Heine University, Duesseldorf, Germany
| | - Mathias Beller
- From the ‡Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Duesseldorf, Germany; .,§Systems Biology of Lipid metabolism, Heinrich Heine University, Duesseldorf, Germany
| |
Collapse
|
24
|
Zamith-Miranda D, Palma ML, Matos GS, Schiebel JG, Maya-Monteiro CM, Aronovich M, Bozza PT, Bozza FA, Nimrichter L, Montero-Lomeli M, Marques ET, Martins FS, Douradinha B. Lipid droplet levels vary heterogeneously in response to simulated gastrointestinal stresses in different probiotic Saccharomyces cerevisiae strains. J Funct Foods 2016. [DOI: 10.1016/j.jff.2015.12.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
|
25
|
Silverman AM, Qiao K, Xu P, Stephanopoulos G. Functional overexpression and characterization of lipogenesis-related genes in the oleaginous yeast Yarrowia lipolytica. Appl Microbiol Biotechnol 2016; 100:3781-98. [DOI: 10.1007/s00253-016-7376-0] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 01/14/2016] [Accepted: 02/02/2016] [Indexed: 11/24/2022]
|
26
|
Liu HH, Ji XJ, Huang H. Biotechnological applications of Yarrowia lipolytica: Past, present and future. Biotechnol Adv 2015; 33:1522-46. [DOI: 10.1016/j.biotechadv.2015.07.010] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 07/13/2015] [Accepted: 07/29/2015] [Indexed: 01/01/2023]
|
27
|
Bui Q, Sherma J, Fried B, Hines J. Determination of Growth-Phase Dependent Influences Exerted by Prions on Yeast Lipid Content Using HPTLC-Densitometry. ACTA CHROMATOGR 2015; 28:373-385. [PMID: 27974871 PMCID: PMC5152692 DOI: 10.1556/1326.2016.28.3.7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Prions of the baker's yeast Saccharomyces cerevisiae allow for the inheritance of complex traits based solely on the acquisition of cytoplasmic protein aggregates and confer distinctive phenotypes to the cells which harbor them, creating heterogeneity within an otherwise clonal cell population. These phenotypes typically arise from a loss-of-function of the prion-forming protein that is unable to perform its normal cellular function(s) while sequestered in prion amyloid aggregates, but the specific biochemical consequences of prion infection are poorly understood. To begin to address this issue, we initiated a direct investigation into the potential control that yeast prions exert over fungal lipid content by utilizing the prions [URE3] and [PSI+], the first two prions discovered in yeast. We utilized silica gel high-performance thin-layer chromatography (HPTLC)-densitometry to conduct pair-wise quantifications of the relative levels of free sterols, free fatty acids, and triacylglycerols [petroleum ether-diethyl ether-acetic acid (80:20:1) mobile phase, phosphomolybdic acid (PMA) detection reagent]; steryl esters and squalene (hexane-petroleum ether-diethyl ether-acetic acid (50:20;5:1), PMA]; and phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol (chloroform-diethyl ether-acetic acid (65:25:4.5), cupric sulfate-phosphoric acid) in otherwise clonal prion-infected ([PSI+] or [URE3]) and prion-free ([psi-] or [ure-o]) cells in two growth phases: log-phase and stationary phase. Our analysis revealed multiple statistically significant differences (p < 0.00625) between prion-infected and prion-free cells. Interestingly, prion-induced changes varied dramatically by growth phase, indicating that prions exert differential influences on cell physiology between log and stationary growth. Further experimental replication and extension of the analysis to other prions is expected to resolve additional physiological effects of prion infection. This investigation demonstrates that HPTLC-densitometry is an effective method for studying prion-induced alterations in lipid content in yeast.
Collapse
Affiliation(s)
- Q. Bui
- Department of Chemistry, Lafayette College, Easton, Pennsylvania, United States of America
| | - J. Sherma
- Department of Chemistry, Lafayette College, Easton, Pennsylvania, United States of America
| | - B. Fried
- Department of Biology, Lafayette College, Easton, Pennsylvania, United States of America
| | - J.K. Hines
- Department of Chemistry, Lafayette College, Easton, Pennsylvania, United States of America
| |
Collapse
|
28
|
Abstract
Lipid droplets (LDs) are intracellular structures that regulate neutral lipid homeostasis. In mammals, LD synthesis is inhibited by rapamycin, a known inhibitor of the mTORC1 pathway. In Saccharomyces cerevisiae, LD dynamics are modulated by the growth phase; however, the regulatory pathways involved are unknown. Therefore, we decided to study the role of the TORC1 pathway on LD metabolism in S. cerevisiae. Interestingly, rapamycin treatment resulted in a fast LD replenishment and growth inhibition. The discovery that osmotic stress (1 M sorbitol) also induced LD synthesis but not growth inhibition suggested that the induction of LDs in yeast is not a secondary response to reduced growth. The induction of LDs by rapamycin was due to increased triacylglycerol but not sterol ester synthesis. Induction was dependent on the TOR downstream effectors, the PP2A-related phosphatase Sit4p and the regulatory protein Tap42p. The TORC1-controlled transcriptional activators Gln3p, Gat1p, Rtg1p, and Rtg3p, but not Msn2p and Msn4p, were required for full induction of LDs by rapamycin. Furthermore, we show that the deletion of Gln3p and Gat1p transcription factors, which are activated in response to nitrogen availability, led to abnormal LD dynamics. These results reveal that the TORC1 pathway is involved in neutral lipid homeostasis in yeast.
Collapse
|
29
|
Kiss RS, Nilsson T. Rab proteins implicated in lipid storage and mobilization. J Biomed Res 2014; 28:169-77. [PMID: 25013400 PMCID: PMC4085554 DOI: 10.7555/jbr.28.20140029] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 02/28/2014] [Indexed: 12/28/2022] Open
Abstract
Abnormal intracellular accumulation or transport of lipids contributes greatly to the pathogenesis of human diseases. In the liver, excess accumulation of triacylglycerol (TG) leads to fatty liver disease encompassing steatosis, steatohepatitis and fibrosis. This places individuals at risk of developing cirrhosis, hepatocellular carcinoma or hepatic decompensation and also contributes to the emergence of insulin resistance and dyslipidemias affecting many other organs. Excessive accumulation of TG in adipose tissue contributes to insulin resistance as well as to the release of cytokines attracting leucocytes leading to a pro-inflammatory state. Pathological accumulation of cholesteryl ester (CE) in macrophages in the arterial wall is the progenitor of atherosclerotic plaques and heart disease. Overconsumption of dietary fat, cholesterol and carbohydrates explains why these diseases are on the increase yet offers few clues for how to prevent or treat individuals. Dietary regimes have proven futile and barring surgery, no realistic alternatives are at hand as effective drugs are few and not without side effects. Overweight and obesity-related diseases are no longer restricted to the developed world and as such, constitute a global problem. Development of new drugs and treatment strategies are a priority yet requires as a first step, elucidation of the molecular pathophysiology underlying each associated disease state. The lipid droplet (LD), an up to now overlooked intracellular organelle, appears at the heart of each pathophysiology linking key regulatory and metabolic processes as well as constituting the site of storage of both TGs and CEs. As the molecular machinery and mechanisms of LDs of each cell type are being elucidated, regulatory proteins used to control various cellular processes are emerging. Of these and the subject of this review, small GTPases belonging to the Rab protein family appear as important molecular switches used in the regulation of the intracellular trafficking and storage of lipids.
Collapse
Affiliation(s)
- Robert Scott Kiss
- Department of Medicine, McGill University, Montreal, Canada; ; Research Institute of McGill University Health Centre, Montreal, Canada
| | - Tommy Nilsson
- Department of Medicine, McGill University, Montreal, Canada; ; Research Institute of McGill University Health Centre, Montreal, Canada
| |
Collapse
|