scholarly journals Cerebellar ataxia disease–associated Snx14 promotes lipid droplet growth at ER–droplet contacts

2019 ◽  
Vol 218 (4) ◽  
pp. 1335-1351 ◽  
Author(s):  
Sanchari Datta ◽  
Yang Liu ◽  
Hanaa Hariri ◽  
Jade Bowerman ◽  
W. Mike Henne
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Cerebellar Ataxia ◽  
Lipid Droplets ◽  
Fatty Acyl ◽  
Droplet Growth ◽  
Sorting Nexin ◽  
Coa Ligase ◽  
In Trans ◽  
Time Point

Lipid droplets (LDs) are nutrient reservoirs used by cells to maintain homeostasis. Nascent droplets form on the endoplasmic reticulum (ER) and grow following an influx of exogenous fatty acids (FAs). The budding of LDs requires extensive ER–LD crosstalk, but how this is regulated remains poorly understood. Here, we show that sorting nexin protein Snx14, an ER-resident protein associated with the cerebellar ataxia SCAR20, localizes to ER–LD contacts following FA treatment, where it promotes LD maturation. Using proximity-based APEX technology and topological dissection, we show that Snx14 accumulates specifically at ER–LD contacts independently of Seipin, where it remains ER-anchored and binds LDs in trans. SNX14KO cells exhibit perturbed LD morphology, whereas Snx14 overexpression promotes LD biogenesis and extends ER–LD contacts. Multi–time point imaging reveals that Snx14 is recruited to ER microdomains containing the fatty acyl-CoA ligase ACSL3, where nascent LDs bud. We propose that Snx14 is a novel marker for ER–LD contacts and regulates FA-stimulated LD growth.

scholarly journals Mdm1 maintains endoplasmic reticulum homeostasis by spatially regulating lipid droplet biogenesis

2019 ◽  
Vol 218 (4) ◽  
pp. 1319-1334 ◽  
Author(s):  
Hanaa Hariri ◽  
Natalie Speer ◽  
Jade Bowerman ◽  
Sean Rogers ◽  
Gang Fu ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Fatty Acyl ◽  
Nutrient Depletion ◽  
Coenzyme A Ligase ◽  
Response To Stress ◽  
Acyl Coenzyme A ◽  
Er Homeostasis

Lipid droplets (LDs) serve as cytoplasmic reservoirs for energy-rich fatty acids (FAs) stored in the form of triacylglycerides (TAGs). During nutrient stress, yeast LDs cluster adjacent to the vacuole/lysosome, but how this LD accumulation is coordinated remains poorly understood. The ER protein Mdm1 is a molecular tether that plays a role in clustering LDs during nutrient depletion, but its mechanism of function remains unknown. Here, we show that Mdm1 associates with LDs through its hydrophobic N-terminal region, which is sufficient to demarcate sites for LD budding. Mdm1 binds FAs via its Phox-associated domain and coenriches with fatty acyl–coenzyme A ligase Faa1 at LD bud sites. Consistent with this, loss of MDM1 perturbs free FA activation and Dga1-dependent synthesis of TAGs, elevating the cellular FA level, which perturbs ER morphology and sensitizes yeast to FA-induced lipotoxicity. We propose that Mdm1 coordinates FA activation adjacent to the vacuole to promote LD production in response to stress, thus maintaining ER homeostasis.

scholarly journals Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes

2014 ◽  
Vol 25 (25) ◽  
pp. 4096-4105 ◽  
Author(s):  
Michael Chu ◽  
Harini Sampath ◽  
David Y. Cahana ◽  
Christoph A. Kahl ◽  
Romel Somwar ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Adipose Tissue ◽  
Free Fatty Acids ◽  
Lipid Droplets ◽  
Ex Vivo ◽  
Spatiotemporal Dynamics ◽  
Biological Features ◽  
Adipocyte Hypertrophy ◽  
Cellular Organelles

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.

scholarly journals Postlipolytic insulin-dependent remodeling of micro lipid droplets in adipocytes

2012 ◽  
Vol 23 (10) ◽  
pp. 1826-1837 ◽  
Author(s):  
Nicholas Ariotti ◽  
Samantha Murphy ◽  
Nicholas A. Hamilton ◽  
Lizhen Wu ◽  
Kathryn Green ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Electron Tomography ◽  
Morphological Changes ◽  
Quantitative Imaging ◽  
The Reformation ◽  
Fundamental Process ◽  
Insulin Dependent ◽  
Fat Pads

Despite the lipolysis–lipogenesis cycle being a fundamental process in adipocyte biology, very little is known about the morphological changes that occur during this process. The remodeling of lipid droplets to form micro lipid droplets (mLDs) is a striking feature of lipolysis in adipocytes, but once lipolysis ceases, the cell must regain its basal morphology. We characterized mLD formation in cultured adipocytes, and in primary adipocytes isolated from mouse epididymal fat pads, in response to acute activation of lipolysis. Using real-time quantitative imaging and electron tomography, we show that formation of mLDs in cultured adipocytes occurs throughout the cell to increase total LD surface area by ∼30% but does not involve detectable fission from large LDs. Peripheral mLDs are monolayered structures with a neutral lipid core and are sites of active lipolysis. Electron tomography reveals preferential association of mLDs with the endoplasmic reticulum. Treatment with insulin and fatty acids results in the reformation of macroLDs and return to the basal state. Insulin-dependent reformation of large LDs involves two distinct processes: microtubule-dependent homotypic fusion of mLDs and expansion of individual mLDs. We identify a physiologically important role for LD fusion that is involved in a reversible lipolytic cycle in adipocytes.

scholarly journals Zebrafish lipid droplets regulate embryonic ATP homeostasis to power early development

Open Biology ◽  
2017 ◽  
Vol 7 (7) ◽  
pp. 170063 ◽  
Author(s):  
Asmita Dutta ◽  
Deepak Kumar Sinha
Keyword(s):  
Fatty Acids ◽  
Early Development ◽  
Lipid Droplets ◽  
Developmental Stages ◽  
Fatty Acyl ◽  
Zebrafish Embryos ◽  
Early Developmental Stages ◽  
Successful Execution ◽  
Acyl Coenzyme A ◽  
Early Developmental

In zebrafish embryos, the maternally supplied pool of ATP is insufficient to power even the earliest of developmental events (0–3 hpf) such as oocyte-to-embryo transition (OET). The embryos generate an additional pulse (2.5 h long) of ATP (1.25–4 hpf) to achieve the embryonic ATP homeostasis. We demonstrate that the additional pulse of ATP is needed for successful execution of OET. The maternally supplied yolk lipids play a crucial role in maintaining the embryonic ATP homeostasis. In this paper, we identify the source and trafficking routes of free fatty acids (FFAs) that feed the mitochondria for synthesis of ATP. Interestingly, neither the maternally supplied pool of yolk-FFA nor the yolk-FACoA (fatty acyl coenzyme A) is used for ATP homeostasis during 0–5 hpf in zebrafish embryos. With the help of lipidomics, we explore the link between lipid droplet (LD)-mediated lipolysis and ATP homeostasis in zebrafish embryos. Until 5 hpf, the embryonic LDs undergo extensive lipolysis that generates FFAs. We demonstrate that these newly synthesized FFAs from LDs are involved in the maintenance of embryonic ATP homeostasis, rather than the FFAs/FACoA present in the yolk. Thus, the LDs are vital embryonic organelles that maintain the ATP homeostasis during early developmental stages (0–5 hpf) in zebrafish embryos. Our study highlights the important roles carried on by the LDs during the early development of the zebrafish embryos.

scholarly journals Dictyostelium Lipid Droplets Host Novel Proteins

2013 ◽  
Vol 12 (11) ◽  
pp. 1517-1529 ◽  
Author(s):  
Xiaoli Du ◽  
Caroline Barisch ◽  
Peggy Paschke ◽  
Cornelia Herrfurth ◽  
Oliver Bertinetti ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Unsaturated Fatty Acids ◽  
Neutral Lipids ◽  
Saturated Fatty Acids ◽  
Endoplasmic Reticulum Membrane ◽  
Hydrophobic Core ◽  
Content Type

ABSTRACT Across all kingdoms of life, cells store energy in a specialized organelle, the lipid droplet. In general, it consists of a hydrophobic core of triglycerides and steryl esters surrounded by only one leaflet derived from the endoplasmic reticulum membrane to which a specific set of proteins is bound. We have chosen the unicellular organism Dictyostelium discoideum to establish kinetics of lipid droplet formation and degradation and to further identify the lipid constituents and proteins of lipid droplets. Here, we show that the lipid composition is similar to what is found in mammalian lipid droplets. In addition, phospholipids preferentially consist of mainly saturated fatty acids, whereas neutral lipids are enriched in unsaturated fatty acids. Among the novel protein components are LdpA, a protein specific to Dictyostelium , and Net4, which has strong homologies to mammalian DUF829/Tmem53/NET4 that was previously only known as a constituent of the mammalian nuclear envelope. The proteins analyzed so far appear to move from the endoplasmic reticulum to the lipid droplets, supporting the concept that lipid droplets are formed on this membrane.

scholarly journals Metabolism of palmitate in perfused rat liver. Computer models of subcellular triacylglycerol metabolism

1979 ◽  
Vol 184 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Jens Kondrup ◽  
Stig E. Damgaard ◽  
Peter Fleron
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Preceding Paper ◽  
Computer Models ◽  
The Other ◽  
Triacylglycerol Metabolism ◽  
Cytoplasmic Lipid Droplets ◽  
Hepatic Triacylglycerol ◽  
Hydrolysis Of

1. In the preceding paper [Kondrup (1979) Biochem. J.184, 63–71] the separation of two major fractions of hepatic triacylglycerol was described. One fraction contained triacylglycerol from the endoplasmic reticulum and from the Golgi apparatus. The other fraction contained triacylglycerol from the cytoplasmic lipid droplets. In the present paper possible precursor–product relationships between the two fractions were investigated by means of computer models. 2. The fatty acids present in di- and tri-acylglycerol in the fractions isolated in the time studies were analysed by gas chromatography. From this analysis the relative specific radioactivities, and contents, of palmitate in acylglycerols in the two fractions at the various time points were calculated. 3. A computer was used to predict relative specific radioactivities of pools in defined models of hepatic triacylglycerol metabolism. The acceptability of the models was evaluated by comparing predicted with measured relative specific radioactivities. 4. It is suggested that triacylglycerol in cytoplasmic lipid droplets does not originate (a) directly from triacylglycerol in the endoplasmic reticulum, (b) from a sub-pool of it or (c) directly from non-esterified fatty acids entering the cell. Rather, it is formed from diacylglycerol (and acyl-CoA) in the endoplasmic reticulum. Diacylglycerol, on the other hand, is furnished in part by hydrolysis of triacylglycerol in the endoplasmic reticulum. 5. This suggestion is discussed in relation to previous models of hepatic fatty acid metabolism.

scholarly journals The endoplasmic reticulum-resident protein TMEM-120/TMEM120A promotes fat storage in C. elegans and mammalian cells

2021 ◽  
Author(s):  
Yan Li ◽  
Siwei Huang ◽  
Xuesong Li ◽  
Xingyu Yang ◽  
Ningyi Xu ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Lipid Droplets ◽  
Stimulated Raman Scattering ◽  
Transmembrane Helices ◽  
Fat Storage ◽  
Over Expression ◽  
C Elegans

The synthesis of triacylglycerol (TAG) is essential for the storage of excess fatty acids, which can subsequently be used for energy or cell growth. A series of enzymes act in the endoplasmic reticulum (ER) to synthesize TAG, prior to its transfer to lipid droplets (LDs), which are conserved organelles for fat storage. Here, we report that the deficiency of TMEM-120/TMEM120A, a protein with 6-transmembrane helices, retards TAG synthesis and LD expansion in C. elegans. GFP fusion proteins of TMEM-120, expressed at the endogenous level in live worms, were observed throughout the ER network. Using Stimulated Raman Scattering, we demonstrated the specific requirement of TMEM-120 in the storage of exogenous fatty acids in LDs. Knockdown of TMEM120A impedes adipogenesis of pre-adipocytes in vitro, while its over-expression is sufficient to promote LD expansion in mammalian cells. Our results suggest that TMEM-120/TMEM120A plays a conserved role in increasing the efficiency of TAG synthesis.

Fatty acyl chain structure, orientational order, and the lipid phase transition in Acholeplasma laidlawii B membranes. A review of recent 19F nuclear magnetic resonance studies

1984 ◽  
Vol 62 (11) ◽  
pp. 1134-1150 ◽  
Author(s):  
P. M. Macdonald ◽  
B. D. Sykes ◽  
R. N. McElhaney
Keyword(s):  
Phase Transition ◽  
Fatty Acids ◽  
Nuclear Magnetic Resonance ◽  
Acyl Chain ◽  
Orientational Order ◽  
Membrane Lipid ◽  
Fatty Acyl ◽  
Fatty Acyl Chain ◽  
Lipid Phase ◽  
Lipid Phase Transition

The orientational order parameters of monofluoropalmitic acids biosynthetically incorporated into membranes of Acholeplasma laidlawii B in the presence of a large excess of a variety of structurally diverse fatty acids have been determined via 19F nuclear magnetic resonance (19F NMR) spectroscopy. It is demonstrated that these monofluoropalmitic acids are relatively nonperturbing membrane probes based upon physical (differential scanning calorimetry), biochemical (membrane lipid analysis), and biological (growth studies) criteria. 19F NMR is shown to convey the same qualitative and quantitative picture of membrane lipid order provided by 2H-NMR techniques and to be sensitive to the structural characteristics of the membrane fatty acyl chains, as well as to the lipid phase transition. Representatives of each naturally occurring class of fatty acyl chain structures, including straight-chain saturated, methyl-branched, monounsaturated, and alicyclic-ring-substituted fatty acids, were studied and the 19F-NMR order parameters were correlated with the lipid phase transitions (determined calorimetrically). The lipid phase transition was the prime determinant of overall orientational order regardless of fatty acid structure. Effects upon orientational order attributable to specific structural substituents were discernible, but were secondary to the effects of the lipid phase transition. In the gel state, relative overall order was directly proportional to the temperature of the particular lipid phase transition. Not only the overall order, but also the order profile across the membrane was sensitive to the presence of particular structural substituents. In particular, in the gel state specific fatty acyl structures demonstrated a characteristic disordering effect in the membrane order profile. These various observations can be merged to provide a unified picture of the manner in which fatty acyl chain chemistry modulates the physical state of membrane lipids.

Sign in / Sign up

Export Citation Format

Share Document