Lipid Droplets Protect Aging Mitochondria and Thus Promote Lifespan in Yeast Cells

Besides their role as a storage for neutral lipids and sterols, there is increasing evidence that lipid droplets (LDs) are involved in cellular detoxification. LDs are in close contact to a broad variety of organelles where protein- and lipid exchange is mediated. Mitochondria as a main driver of the aging process produce reactive oxygen species (ROS), which damage several cellular components. LDs as highly dynamic organelles mediate a potent detoxification mechanism by taking up toxic lipids and proteins. A stimulation of LDs induced by the simultaneously overexpression of Lro1p and Dga1p (both encoding acyltransferases) prolongs the chronological as well as the replicative lifespan of yeast cells. The increased number of LDs reduces mitochondrial fragmentation as well as mitochondrial ROS production, both phenotypes that are signs of aging. Strains with an altered LD content or morphology as in the sei1∆ or lro1∆ mutant lead to a reduced replicative lifespan. In a yeast strain defective for the LON protease Pim1p, which showed an enhanced ROS production, increased doubling time and an altered mitochondrial morphology, a LRO1 overexpression resulted in a partially reversion of this “premature aging” phenotype.

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A Unique Junctional Interface at Contact Sites Between the Endoplasmic Reticulum and Lipid Droplets

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.650186 ◽

2021 ◽

Vol 9 ◽

Author(s):

Vineet Choudhary ◽

Roger Schneiter

Keyword(s):

Endoplasmic Reticulum ◽

Lipid Droplets ◽

Neutral Lipids ◽

Close Contact ◽

Lipid Storage ◽

Metabolic Energy ◽

Lipid Monolayer ◽

Storage Diseases ◽

Contact Sites ◽

Ordered Assembly

Lipid droplets (LDs) constitute compartments dedicated to the storage of metabolic energy in the form of neutral lipids. LDs originate from the endoplasmic reticulum (ER) with which they maintain close contact throughout their life cycle. These ER–LD junctions facilitate the exchange of both proteins and lipids between these two compartments. In recent years, proteins that are important for the proper formation of LDs and localize to ER–LD junctions have been identified. This junction is unique as it is generally believed to invoke a transition from the ER bilayer membrane to a lipid monolayer that delineates LDs. Proper formation of this junction requires the ordered assembly of proteins and lipids at specialized ER subdomains. Without such a well-ordered assembly of LD biogenesis factors, neutral lipids are synthesized throughout the ER membrane, resulting in the formation of aberrant LDs. Such ectopically formed LDs impact ER and lipid homeostasis, resulting in different types of lipid storage diseases. In response to starvation, the ER–LD junction recruits factors that tether the vacuole to these junctions to facilitate LD degradation. In addition, LDs maintain close contacts with peroxisomes and mitochondria for metabolic channeling of the released fatty acids toward beta-oxidation. In this review, we discuss the function of different components that ensure proper functioning of LD contact sites, their role in lipogenesis and lipolysis, and their relation to lipid storage diseases.

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Lecithin:Retinol Acyl Transferase (LRAT) induces the formation of lipid droplets

10.1101/733931 ◽

2019 ◽

Cited By ~ 3

Author(s):

Martijn R. Molenaar ◽

Tsjerk A. Wassenaar ◽

Kamlesh K. Yadav ◽

Alexandre Toulmay ◽

Muriel C. Mari ◽

...

Keyword(s):

Mammalian Cells ◽

Lipid Droplets ◽

Neutral Lipids ◽

Yeast Cells ◽

Acyl Transferase ◽

Hydrophobic Core ◽

Retinyl Ester ◽

Steryl Esters ◽

Retinyl Esters

AbstractLipid droplets are unique and nearly ubiquitous organelles that store neutral lipids in a hydrophobic core, surrounded by a monolayer of phospholipids. The primary neutral lipids are triacylglycerols and steryl esters. It is not known whether other classes of neutral lipids can form lipid droplets by themselves. Here we show that production of retinyl esters by lecithin:retinol acyl transferase (LRAT) in yeast cells, incapable of producing triacylglycerols and steryl esters, causes the formation of lipid droplets. By electron microscopy, these lipid droplets are morphologically indistinguishable from those in wild-type cells. In silico and in vitro experiments confirmed the propensity of retinyl esters to segregate from membranes and to form lipid droplets. The hydrophobic N-terminus of LRAT displays preferential interactions with retinyl esters in membranes and promotes the formation of large retinyl ester-containing lipid droplets in mammalian cells. Our combined data indicate that the molecular design of LRAT is optimally suited to allow the formation of characteristic large lipid droplets in retinyl ester-storing cells.

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Human VPS13A is associated with multiple organelles and influences mitochondrial morphology and lipid droplet motility

eLife ◽

10.7554/elife.43561 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 29

Author(s):

Wondwossen M Yeshaw ◽

Marianne van der Zwaag ◽

Francesco Pinto ◽

Liza L Lahaye ◽

Anita IE Faber ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Lipid Droplet ◽

Mammalian Cells ◽

Lipid Droplets ◽

Neurodegenerative Disorder ◽

Close Contact ◽

Mitochondrial Morphology ◽

Published Data ◽

Membrane Contact Sites ◽

Contact Sites

The VPS13A gene is associated with the neurodegenerative disorder Chorea Acanthocytosis. It is unknown what the consequences are of impaired function of VPS13A at the subcellular level. We demonstrate that VPS13A is a peripheral membrane protein, associated with mitochondria, the endoplasmic reticulum and lipid droplets. VPS13A is localized at sites where the endoplasmic reticulum and mitochondria are in close contact. VPS13A interacts with the ER residing protein VAP-A via its FFAT domain. Interaction with mitochondria is mediated via its C-terminal domain. In VPS13A-depleted cells, ER-mitochondria contact sites are decreased, mitochondria are fragmented and mitophagy is decreased. VPS13A also localizes to lipid droplets and affects lipid droplet motility. In VPS13A-depleted mammalian cells lipid droplet numbers are increased. Our data, together with recently published data from others, indicate that VPS13A is required for establishing membrane contact sites between various organelles to enable lipid transfer required for mitochondria and lipid droplet related processes.

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Lipid droplets form a network interconnected by the endoplasmic reticulum through which they equilibrate their proteins

Journal of Cell Science ◽

10.1242/jcs.258819 ◽

2021 ◽

Author(s):

Stéphanie Cottier ◽

Roger Schneiter

Keyword(s):

Endoplasmic Reticulum ◽

Lipid Droplets ◽

Neutral Lipids ◽

Yeast Cells ◽

Zygote Formation ◽

Protein Transfer ◽

Mating Partner ◽

Functional Connection ◽

Yeast Mating ◽

Er Membrane

Lipid droplets (LDs) are globular intracellular structures dedicated to the storage of neutral lipids. They are closely associated with the endoplasmic reticulum (ER) and are delineated by a monolayer of phospholipids that is continuous with the cytoplasmic leaflet of the ER membrane. LDs contain a specific set of proteins, but how these proteins are targeted to the LD surface is not fully understood. Here we devised a yeast mating-based microscopic readout to monitor the transfer of LD proteins upon zygote formation. The results of this analysis indicate that ER fusion between mating partners is required for transfer of LD proteins and that this transfer is continuous, bidirectional and affects most LDs simultaneously. These observations suggest that LDs do not fuse upon mating of yeast cells, but that they form a network that is interconnected through the ER membrane. Consistent with this, ER-localized LD proteins rapidly move onto LDs of a mating partner and this protein transfer is affected by seipin, a protein important for proper LD biogenesis and the functional connection of LDs with the ER membrane.

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Yeast Cells Exposed to Exogenous Palmitoleic Acid Either Adapt to Stress and Survive or Commit to Regulated Liponecrosis and Die

Oxidative Medicine and Cellular Longevity ◽

10.1155/2018/3074769 ◽

2018 ◽

Vol 2018 ◽

pp. 1-11 ◽

Cited By ~ 4

Author(s):

Karamat Mohammad ◽

Paméla Dakik ◽

Younes Medkour ◽

Mélissa McAuley ◽

Darya Mitrofanova ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Lipid Metabolism ◽

Lipid Droplets ◽

Palmitoleic Acid ◽

Molecular Mechanisms ◽

Neutral Lipids ◽

Yeast Cells ◽

Cellular Processes ◽

Regulated Cell Death

A disturbed homeostasis of cellular lipids and the resulting lipotoxicity are considered to be key contributors to many human pathologies, including obesity, metabolic syndrome, type 2 diabetes, cardiovascular diseases, and cancer. The yeast Saccharomyces cerevisiae has been successfully used for uncovering molecular mechanisms through which impaired lipid metabolism causes lipotoxicity and elicits different forms of regulated cell death. Here, we discuss mechanisms of the “liponecrotic” mode of regulated cell death in S. cerevisiae. This mode of regulated cell death can be initiated in response to a brief treatment of yeast with exogenous palmitoleic acid. Such treatment prompts the incorporation of exogenously added palmitoleic acid into phospholipids and neutral lipids. This orchestrates a global remodeling of lipid metabolism and transfer in the endoplasmic reticulum, mitochondria, lipid droplets, and the plasma membrane. Certain features of such remodeling play essential roles either in committing yeast to liponecrosis or in executing this mode of regulated cell death. We also outline four processes through which yeast cells actively resist liponecrosis by adapting to the cellular stress imposed by palmitoleic acid and maintaining viability. These prosurvival cellular processes are confined in the endoplasmic reticulum, lipid droplets, peroxisomes, autophagosomes, vacuoles, and the cytosol.

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Upregulation of the Cdc42 GTPase limits replicative lifespan in budding yeast

10.1101/2021.04.27.441634 ◽

2021 ◽

Author(s):

Pil Jung Kang ◽

Rachel Mullner ◽

Haoyu Li ◽

Derek Hansford ◽

Han-Wei Shen ◽

...

Keyword(s):

Cell Polarity ◽

Asymmetric Cell Division ◽

Rho Gtpase ◽

Budding Yeast ◽

Premature Aging ◽

Yeast Cells ◽

Replicative Lifespan ◽

Cellular Processes ◽

Cell Divisions ◽

Short Lifespan

ABSTRACTCell polarity underlies various cellular processes, including cell proliferation and asymmetric cell division. Cdc42, a conserved Rho GTPase, plays a central role in polarity establishment in yeast and animals. While cell polarity is critical for the asymmetric division of budding yeast, whether Cdc42 impacts lifespan is not clear. Here, we show by live-cell imaging that the active Cdc42 level is sporadically elevated in wild-type cells during repeated cell divisions but rarely in the long-lived bud8 deletion mutant. Remarkably, mild overexpression of Cdc42 causes premature aging with frequent symmetric cell divisions despite no harmful effects on young cells. Furthermore, deletion of BUD8 rescues the short lifespan of an rga1 mutant, which lacks a Cdc42 GTPase activating protein, and Bud8 competes with Rga1 for localization to cytokinesis remnants. Collectively, our findings suggest that upregulation of Cdc42 is a proximal cause of cell death in old yeast cells and that Bud8 counteracts Rga1 in modulating the Cdc42 activity to limit replicative lifespan.

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Retinyl esters form lipid droplets independently of triacylglycerol and seipin

The Journal of Cell Biology ◽

10.1083/jcb.202011071 ◽

2021 ◽

Vol 220 (10) ◽

Author(s):

Martijn R. Molenaar ◽

Kamlesh K. Yadav ◽

Alexandre Toulmay ◽

Tsjerk A. Wassenaar ◽

Muriel C. Mari ◽

...

Keyword(s):

Lipid Bilayers ◽

Lipid Droplet ◽

Lipid Droplets ◽

Neutral Lipids ◽

Yeast Cells ◽

In Vitro Experiments ◽

Steryl Esters ◽

Retinyl Esters

Lipid droplets store neutral lipids, primarily triacylglycerol and steryl esters. Seipin plays a role in lipid droplet biogenesis and is thought to determine the site of lipid droplet biogenesis and the size of newly formed lipid droplets. Here we show a seipin-independent pathway of lipid droplet biogenesis. In silico and in vitro experiments reveal that retinyl esters have the intrinsic propensity to sequester and nucleate in lipid bilayers. Production of retinyl esters in mammalian and yeast cells that do not normally produce retinyl esters causes the formation of lipid droplets, even in a yeast strain that produces only retinyl esters and no other neutral lipids. Seipin does not determine the size or biogenesis site of lipid droplets composed of only retinyl esters or steryl esters. These findings indicate that the role of seipin in lipid droplet biogenesis depends on the type of neutral lipid stored in forming droplets.

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Lipid droplets are central organelles for meiosis II progression during yeast sporulation

Molecular Biology of the Cell ◽

10.1091/mbc.e16-06-0375 ◽

2017 ◽

Vol 28 (3) ◽

pp. 440-451 ◽

Cited By ~ 14

Author(s):

Tzu-Han Hsu ◽

Rey-Huei Chen ◽

Yun-Hsin Cheng ◽

Chao-Wen Wang

Keyword(s):

Lipid Droplets ◽

De Novo ◽

Neutral Lipids ◽

Spore Wall ◽

Yeast Cells ◽

Cytological Evidence ◽

Major Function ◽

Cellular Events ◽

Membrane Morphogenesis ◽

Wall Assembly

Neutral lipids, predominantly triacylglycerol (TAG) and sterol ester, are stored within the cellular organelles termed lipid droplets (LDs). Although it is believed that the major function of LDs is to supply the cell with energy and membranes, little is known about the cellular events directly involving LDs and their contents. In this study, we provide cytological evidence that LDs form direct contacts with the prospore membrane (PSM) that is synthesized de novo during meiosis II to sequester the dividing nuclei in sporulating yeast. Lipidomic analyses indicate that TAG lipolysis releases free fatty acids at a time that correlates well with meiosis II progression, concomitant with phospholipid remodeling. Mutants lacking TAG or impaired of TAG hydrolysis show spore wall assembly defects, supporting a role for TAG and/or its metabolites in spore wall morphogenesis. Not only does LD integrity influence spore wall assembly, LDs are also essential for other aspects of spore development. Yeast cells lacking LDs are severely defective in PSM growth and organization and display disrupted spindles, producing dead spores or even failing to form spores. Together these results link LD physiology directly to a unique membrane morphogenesis process critical for development.

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A Molecular Logic Gate Enables Super-Resolved Imaging of Intracellular Lipid Droplets

10.26434/chemrxiv.9784799.v1 ◽

2019 ◽

Author(s):

Adam Eördögh ◽

Carolina Paganini ◽

Dorothea Pinotsi ◽

Paolo Arosio ◽

Pablo Rivera-Fuentes

Keyword(s):

Single Molecule ◽

Lipid Droplets ◽

Neutral Lipids ◽

Logic Gate ◽

Living Cells ◽

Three Dimensions ◽

Single Molecule Imaging ◽

Molecular Logic Gate ◽

Molecular Logic ◽

Cellular Compartments

<div>Photoactivatable dyes enable single-molecule imaging in biology. Despite progress in the development of new fluorophores and labeling strategies, many cellular compartments remain difficult to image beyond the limit of diffraction in living cells. For example, lipid droplets, which are organelles that contain mostly neutral lipids, have eluded single-molecule imaging. To visualize these challenging subcellular targets, it is necessary to develop new fluorescent molecular devices beyond simple on/off switches. Here, we report a fluorogenic molecular logic gate that can be used to image single molecules associated with lipid droplets with excellent specificity. This probe requires the subsequent action of light, a lipophilic environment and a competent nucleophile to produce a fluorescent product. The combination of these requirements results in a probe that can be used to image the boundary of lipid droplets in three dimensions with resolutions beyond the limit of diffraction. Moreover, this probe enables single-molecule tracking of lipids within and between droplets in living cells.</div>

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Interactions of Lipid Droplets with the Intracellular Transport Machinery

International Journal of Molecular Sciences ◽

10.3390/ijms22052776 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2776

Author(s):

Selma Yilmaz Dejgaard ◽

John F. Presley

Keyword(s):

Membrane Trafficking ◽

Lipid Droplets ◽

Intracellular Transport ◽

Neutral Lipids ◽

Small Gtpases ◽

Lipid Phase ◽

Intracellular Organelles ◽

And Function ◽

Lipid Phase Separation ◽

Endocytic Pathways

Historically, studies of intracellular membrane trafficking have focused on the secretory and endocytic pathways and their major organelles. However, these pathways are also directly implicated in the biogenesis and function of other important intracellular organelles, the best studied of which are peroxisomes and lipid droplets. There is a large recent body of work on these organelles, which have resulted in the introduction of new paradigms regarding the roles of membrane trafficking organelles. In this review, we discuss the roles of membrane trafficking in the life cycle of lipid droplets. This includes the complementary roles of lipid phase separation and proteins in the biogenesis of lipid droplets from endoplasmic reticulum (ER) membranes, and the attachment of mature lipid droplets to membranes by lipidic bridges and by more conventional protein tethers. We also discuss the catabolism of neutral lipids, which in part results from the interaction of lipid droplets with cytosolic molecules, but with important roles for both macroautophagy and microautophagy. Finally, we address their eventual demise, which involves interactions with the autophagocytotic machinery. We pay particular attention to the roles of small GTPases, particularly Rab18, in these processes.

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