Neutral lipids regulate amphipathic helix affinity for model lipid droplets

Cellular lipid droplets (LDs) have a neutral lipid core shielded from the aqueous environment by a phospholipid monolayer containing proteins. These proteins define the biological functions of LDs, and most of them bear amphipathic helices (AH), which can selectively target to LDs, or to LD subsets. How such binding preference happens remains poorly understood. Here, we found that artificial LDs made of different neutral lipids but presenting equal phospholipid packing densities differentially recruit AHs. Varying the phospholipid density shifts the binding levels, but the differential recruitment is unchanged. We found that the binding level of AHs is defined by their interaction preference with neutral lipids and ability to decrease surface tension. The phospholipid packing level regulates mainly the amount of neutral lipid accessible. Therefore, it is the hydrophobic nature of the phospholipid packing voids that controls the binding level of AHs. Our data bring us a major step closer to understanding the binding selectivity of AHs to lipid membranes.

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Intracellular Lipid Droplets: From Structure to Function

Lipid Insights ◽

10.1177/1178635317745518 ◽

2017 ◽

Vol 10 ◽

pp. 117863531774551 ◽

Cited By ~ 13

Author(s):

Stefano Vanni

Keyword(s):

Lipid Droplets ◽

Neutral Lipids ◽

Interfacial Structure ◽

Aqueous Environment ◽

Sterol Esters ◽

Computational Approaches ◽

Main Site ◽

Natural Surfactant ◽

Oil Emulsions ◽

Function Relationship

Lipid droplets (LDs) are unique intracellular organelles that are mainly constituted by neutral lipids (triglycerides, sterol esters). As such they serve as the main site of energy storage in the cell and they are akin to oil emulsions in water. To prevent the direct exposure of the hydrophobic neutral lipids to the aqueous environment of the cytosol, LDs are surrounded by a monolayer of phospholipids that thus behave as a natural surfactant. This interfacial structure is rather unique inside the cell, but a molecular understanding of how the LD structure modulates its functions is still lacking, mainly due to technical challenges in both experimental and computational approaches to investigate oil-in-water emulsions. Recently, we have investigated the structure of LDs using a combination of existing and newly developed computational approaches that are optimized to study oil-water interfaces.1 Our simulations provide a comprehensive molecular characterization of the unique surface properties of LDs, suggesting structure-function relationship in several LD-related metabolic processes.

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The yeast lipin orthologue Pah1p is important for biogenesis of lipid droplets

The Journal of Cell Biology ◽

10.1083/jcb.201010111 ◽

2011 ◽

Vol 192 (6) ◽

pp. 1043-1055 ◽

Cited By ~ 167

Author(s):

Oludotun Adeyo ◽

Patrick J. Horn ◽

SungKyung Lee ◽

Derk D. Binns ◽

Anita Chandrahas ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Neutral Lipid ◽

Strong Evidence ◽

Lipid Droplets ◽

Neutral Lipids ◽

Glucose Medium ◽

Wild Type ◽

Lipid Levels ◽

Total Neutral Lipid ◽

A Site

Lipins are phosphatidate phosphatases that generate diacylglycerol (DAG). In this study, we report that yeast lipin, Pah1p, controls the formation of cytosolic lipid droplets. Disruption of PAH1 resulted in a 63% decrease in droplet number, although total neutral lipid levels did not change. This was accompanied by an accumulation of neutral lipids in the endoplasmic reticulum (ER). The droplet biogenesis defect was not a result of alterations in neutral lipid ratios. No droplets were visible in the absence of both PAH1 and steryl acyltransferases when grown in glucose medium, even though the strain produces as much triacylglycerol as wild type. The requirement of PAH1 for normal droplet formation can be bypassed by a knockout of DGK1. Nem1p, the activator of Pah1p, localizes to a single punctum per cell on the ER that is usually next to a droplet, suggesting that it is a site of droplet assembly. Overall, this study provides strong evidence that DAG generated by Pah1p is important for droplet biogenesis.

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Neutral Lipid Content in Lipid Droplets: Potential Biomarker of Cordycepin Accumulation in Cordycepin-Producing Fungi

Molecules ◽

10.3390/molecules24183363 ◽

2019 ◽

Vol 24 (18) ◽

pp. 3363 ◽

Cited By ~ 1

Author(s):

Peng Qin ◽

ZhiYe Wang ◽

DengXue Lu ◽

HongMei Kang ◽

Guang Li ◽

...

Keyword(s):

Neutral Lipid ◽

Fluorescence Intensity ◽

Lipid Content ◽

Lipid Droplets ◽

Neutral Lipids ◽

Nile Red ◽

Hplc Method ◽

Relative Fluorescence Intensity ◽

Potential Biomarker ◽

Neutral Lipid Content

To clarify the relationship between neutral lipid content and cordycepin accumulation in Cordyceps militaris, mutants were generated from mixed spores of two C. militaris strains with varying cordycepin-producing capacities. Fifteen stable mutants producing from 0.001 to 2.363 mg/mL cordycepin were finally selected. The relative fluorescence intensities of the 15 mutants, two C. militaris strains and an Aspergillus nidulans strain at different concentrations of lyophilized mycelium powder were then investigated using the Nile red method. The mutant CM1-1-1 with the highest relative fluorescence intensity among the eighteen strains was selected for optimizing the Nile red method. Relative fluorescence intensity was linearly correlated with cordycepin concentration in liquid broth (R2 = 0.9514) and in lyophilized mycelium powder (R2 = 0.9378) for the 18 cordycepin-producing strains under identical culture conditions and with cordycepin concentration in liquid broth (R2 = 0.9727) and in lyophilized mycelium powder (R2 = 0.9613) for CM1-1-1 under eight different sets of conditions. In addition, the cordycepin content in lyophilized mycelium powder measured by the Nile red method was linearly correlated with that determined by an HPLC method (R2 = 0.9627). In conclusion, neutral lipids in lipid droplets are required during cordycepin accumulation; these neutral lipids are potential biomarkers of cordycepin biosynthesis.

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The architecture of Cidec-mediated interfaces between lipid droplets

10.1101/2021.03.23.436555 ◽

2021 ◽

Author(s):

Iva Ganeva ◽

Koini Lim ◽

Jerome Boulanger ◽

Patrick C. Hoffmann ◽

David B. Savage ◽

...

Keyword(s):

Fluorescence Microscopy ◽

Neutral Lipid ◽

Lipid Droplets ◽

Neutral Lipids ◽

Lipid Transfer ◽

Surplus Energy ◽

White Adipocytes ◽

Architectural Features ◽

Intracellular Organelles ◽

Kinetics Of

Lipid droplets (LDs) are intracellular organelles responsible for storing surplus energy as neutral lipids. Their size and number vary enormously. In white adipocytes, they reach up to 100 μm in size, occupying >90% of the cell. Cidec, which is strictly required for the formation of such large LDs, is concentrated at interfaces between adjacent LDs and facilitates the directional flux of neutral lipids from the smaller to the larger LD. However, the mechanism of lipid transfer is unclear, in part because the architecture of interfaces between LDs has remained elusive. Here we visualised interfaces between LDs by electron cryo-tomography and analysed the kinetics of lipid transfer by quantitative live fluorescence microscopy. We show that transfer occurs through closely apposed intact monolayers, is slowed down by increasing the distance between the monolayers and follows exponential kinetics suggesting a pressure-driven mechanism. We thus propose that unique architectural features of LD-LD interfaces are mechanistic determinants of neutral lipid transfer.

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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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The Lack of the C-Terminal Domain of Adipose Triglyceride Lipase Causes Neutral Lipid Storage Disease through Impaired Interactions with Lipid Droplets

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2007-2247 ◽

2008 ◽

Vol 93 (7) ◽

pp. 2877-2884 ◽

Cited By ~ 73

Author(s):

Kunihisa Kobayashi ◽

Toyoshi Inoguchi ◽

Yasutaka Maeda ◽

Naoki Nakashima ◽

Asako Kuwano ◽

...

Keyword(s):

Neutral Lipid ◽

Lipid Droplets ◽

Storage Disease ◽

Lipid Storage ◽

Adipose Triglyceride Lipase ◽

Lipid Storage Disease ◽

Triglyceride Lipase ◽

Terminal Domain ◽

Neutral Lipid Storage Disease

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An essential vesicular-trafficking phospholipase mediates neutral lipid synthesis and contributes to hemozoin formation in Plasmodium falciparum

BMC Biology ◽

10.1186/s12915-021-01042-z ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Mohd Asad ◽

Yoshiki Yamaryo-Botté ◽

Mohammad E. Hossain ◽

Vandana Thakur ◽

Shaifali Jain ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Neutral Lipid ◽

Neutral Lipids ◽

Lipid Synthesis ◽

Large Family ◽

Degradation Pathway ◽

Food Vacuole ◽

Parasite Growth ◽

Lipid Homeostasis ◽

Parasite Development

Abstract Background Plasmodium falciparum is the pathogen responsible for the most devastating form of human malaria. As it replicates asexually in the erythrocytes of its human host, the parasite feeds on haemoglobin uptaken from these cells. Heme, a toxic by-product of haemoglobin utilization by the parasite, is neutralized into inert hemozoin in the food vacuole of the parasite. Lipid homeostasis and phospholipid metabolism are crucial for this process, as well as for the parasite’s survival and propagation within the host. P. falciparum harbours a uniquely large family of phospholipases, which are suggested to play key roles in lipid metabolism and utilization. Results Here, we show that one of the parasite phospholipase (P. falciparum lysophospholipase, PfLPL1) plays an essential role in lipid homeostasis linked with the haemoglobin degradation and heme conversion pathway. Fluorescence tagging showed that the PfLPL1 in infected blood cells localizes to dynamic vesicular structures that traffic from the host-parasite interface at the parasite periphery, through the cytosol, to get incorporated into a large vesicular lipid rich body next to the food-vacuole. PfLPL1 is shown to harbour enzymatic activity to catabolize phospholipids, and its transient downregulation in the parasite caused a significant reduction of neutral lipids in the food vacuole-associated lipid bodies. This hindered the conversion of heme, originating from host haemoglobin, into the hemozoin, and disrupted the parasite development cycle and parasite growth. Detailed lipidomic analyses of inducible knock-down parasites deciphered the functional role of PfLPL1 in generation of neutral lipid through recycling of phospholipids. Further, exogenous fatty-acids were able to complement downregulation of PfLPL1 to rescue the parasite growth as well as restore hemozoin levels. Conclusions We found that the transient downregulation of PfLPL1 in the parasite disrupted lipid homeostasis and caused a reduction in neutral lipids essentially required for heme to hemozoin conversion. Our study suggests a crucial link between phospholipid catabolism and generation of neutral lipids (TAGs) with the host haemoglobin degradation pathway.

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