scholarly journals Retinyl esters form lipid droplets independently of triacylglycerol and seipin

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.

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

2019 ◽  
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.

Mechanisms of lipid droplet biogenesis

2019 ◽  
Vol 476 (13) ◽  
pp. 1929-1942 ◽  
Author(s):  
Kent D. Chapman ◽  
Mina Aziz ◽  
John M. Dyer ◽  
Robert T. Mullen
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
Steryl Esters ◽  
Evolutionarily Conserved ◽  
Compare And Contrast ◽  
In Cells

Abstract Lipid droplets (LDs) are organelles that compartmentalize nonbilayer-forming lipids in the aqueous cytoplasm of cells. They are ubiquitous in most organisms, including in animals, protists, plants and microorganisms. In eukaryotes, LDs are believed to be derived by a budding and scission process from the surface of the endoplasmic reticulum, and this occurs concomitantly with the accumulation of neutral lipids, most often triacylglycerols and steryl esters. Overall, the mechanisms underlying LD biogenesis are difficult to generalize, in part because of the involvement of different sets of both evolutionarily conserved and organism-specific LD-packaging proteins. Here, we briefly compare and contrast these proteins and the allied processes responsible for LD biogenesis in cells of animals, yeasts and plants.

scholarly journals Some Lipid Droplets Are More Equal Than Others: Different Metabolic Lipid Droplet Pools in Hepatic Stellate Cells

2017 ◽  
Vol 10 ◽  
pp. 117863531774728 ◽  
Author(s):  
Martijn R Molenaar ◽  
Arie B Vaandrager ◽  
J Bernd Helms
Keyword(s):  
Lipid Droplet ◽  
Hepatic Stellate Cells ◽  
Lipid Droplets ◽  
Cell Activation ◽  
Neutral Lipids ◽  
Stellate Cell ◽  
Stellate Cells ◽  
Molecular Machinery ◽  
Retinyl Esters ◽  
Slow Turnover

Hepatic stellate cells (HSCs) are professional lipid-storing cells and are unique in their property to store most of the retinol (vitamin A) as retinyl esters in large-sized lipid droplets. Hepatic stellate cell activation is a critical step in the development of chronic liver disease, as activated HSCs cause fibrosis. During activation, HSCs lose their lipid droplets containing triacylglycerols, cholesteryl esters, and retinyl esters. Lipidomic analysis revealed that the dynamics of disappearance of these different classes of neutral lipids are, however, very different from each other. Although retinyl esters steadily decrease during HSC activation, triacylglycerols have multiple pools one of which becomes transiently enriched in polyunsaturated fatty acids before disappearing. These observations are consistent with the existence of preexisting “original” lipid droplets with relatively slow turnover and rapidly recycling lipid droplets that transiently appear during activation of HSCs. Elucidation of the molecular machinery involved in the regulation of these distinct lipid droplet pools may open new avenues for the treatment of liver fibrosis.

Identification of Perilipin-2 as a lipid droplet protein regulated in oocytes during maturation

2010 ◽  
Vol 22 (8) ◽  
pp. 1262 ◽  
Author(s):  
Xing Yang ◽  
Kylie R. Dunning ◽  
Linda L.-Y. Wu ◽  
Theresa E. Hickey ◽  
Robert J. Norman ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
Lipid Content ◽  
Lipid Droplets ◽  
Intracellular Lipids ◽  
Epidermal Growth ◽  
Novel Method ◽  
Perilipin 2 ◽  
Lipid Droplet Protein

Lipid droplet proteins regulate the storage and utilisation of intracellular lipids. Evidence is emerging that oocyte lipid utilisation impacts embryo development, but lipid droplet proteins have not been studied in oocytes. The aim of the present study was to characterise the size and localisation of lipid droplets in mouse oocytes during the periovulatory period and to identify lipid droplet proteins as potential biomarkers of oocyte lipid content. Oocyte lipid droplets, visualised using a novel method of staining cumulus–oocyte complexes (COCs) with BODIPY 493/503, were small and diffuse in oocytes of preovulatory COCs, but larger and more centrally located after maturation in response to ovulatory human chorionic gonadotrophin (hCG) in vivo, or FSH + epidermal growth factor in vitro. Lipid droplet proteins Perilipin, Perilipin-2, cell death-inducing DNA fragmentation factor 45-like effector (CIDE)-A and CIDE-B were detected in the mouse ovary by immunohistochemistry, but only Perilipin-2 was associated with lipid droplets in the oocyte. In COCs, Perilipin-2 mRNA and protein increased in response to ovulatory hCG. IVM failed to induce Perilipin-2 mRNA, yet oocyte lipid content was increased in this context, indicating that Perilipin-2 is not necessarily reflective of relative oocyte lipid content. Thus, Perilipin-2 is a lipid droplet protein in oocytes and its induction in the COC concurrent with dynamic reorganisation of lipid droplets suggests marked changes in lipid utilisation during oocyte maturation.

Role of cysteine in jaundice hemorrhages

1935 ◽  
Vol 31 (8-9) ◽  
pp. 1114-1114
Keyword(s):  
Amino Acid ◽  
Obstructive Jaundice ◽  
Blood Clotting ◽  
In Vitro Experiments ◽  
Main Factor

The role of calcium, platelets, and other factors that were associated with bleeding was not confirmed in jaundice. Carr and Toote found that the amino acid cysteine was the main factor impeding blood clotting. In obstructive jaundice, this amino acid accumulates in the blood and in in vitro experiments and, when administered to animals, causes a deterioration in blood clotting.

773 HEPATITIS C VIRUS AND LIPID DROPLETS: ROLE OF SEIPIN IN LIPID DROPLET MATURATION AND VIRAL LIFE CYCLE

2011 ◽  
Vol 54 ◽  
pp. S311 ◽  
Author(s):  
S. Clement ◽  
C. Fauvelle ◽  
S. Pascarella ◽  
S. Conzelmann ◽  
V. Kaddai ◽  
...  
Keyword(s):  
Life Cycle ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Viral Life Cycle

scholarly journals Exon 9-deleted CETP inhibits full length-CETP synthesis and promotes cellular triglyceride storage

2020 ◽  
Vol 61 (3) ◽  
pp. 422-431 ◽  
Author(s):  
Lahoucine Izem ◽  
Yan Liu ◽  
Richard E. Morton
Keyword(s):  
Lipid Metabolism ◽  
Lipid Droplets ◽  
Full Length ◽  
Intracellular Lipid ◽  
Transfer Protein ◽  
Lipid Phenotype ◽  
Exon 9 ◽  
And Storage

Cholesteryl ester transfer protein (CETP) exists as full-length (FL) and exon 9 (E9)-deleted isoforms. The function of E9-deleted CETP is poorly understood. Here, we investigated the role of E9-deleted CETP in regulating the secretion of FL-CETP by cells and explored its possible role in intracellular lipid metabolism. CETP overexpression in cells that naturally express CETP confirmed that E9-deleted CETP is not secreted, and showed that cellular FL- and E9-deleted CETP form an isolatable complex. Coexpression of CETP isoforms lowered cellular levels of both proteins and impaired FL-CETP secretion. These effects were due to reduced synthesis of both isoforms; however, the predominate consequence of FL- and E9-deleted CETP coexpression is impaired FL-CETP synthesis. We reported previously that reducing both CETP isoforms or overexpressing FL-CETP impairs cellular triglyceride (TG) storage. To investigate this further, E9-deleted CETP was expressed in SW872 cells that naturally synthesize CETP and in mouse 3T3-L1 cells that do not. E9-deleted CETP overexpression stimulated SW872 triglyceride synthesis and increased stored TG 2-fold. Expression of E9-deleted CETP in mouse 3T3-L1 cells produced a similar lipid phenotype. In vitro, FL-CETP promotes the transfer of TG from ER-enriched membranes to lipid droplets. E9-deleted CETP also promoted this transfer, although less effectively, and it inhibited the transfer driven by FL-CETP. We conclude that FL- and E9-deleted CETP isoforms interact to mutually decrease their intracellular levels and impair FL-CETP secretion by reducing CETP biosynthesis. E9-deleted CETP, like FL-CETP, alters cellular TG metabolism and storage but in a contrary manner.

scholarly journals Trophectoderm-Specific Knockdown of LIN28 Decreases Expression of Genes Necessary for Cell Proliferation and Reduces Elongation of Sheep Conceptus

2020 ◽  
Vol 21 (7) ◽  
pp. 2549 ◽  
Author(s):  
Asghar Ali ◽  
Mark Stenglein ◽  
Thomas Spencer ◽  
Gerrit Bouma ◽  
Russell Anthony ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Critical Period ◽  
In Vitro Experiments ◽  
Placental Development ◽  
Expression Of Genes ◽  
Trophectoderm Cells ◽  
Successful Establishment

LIN28 inhibits let-7 miRNA maturation which prevents cell differentiation and promotes proliferation. We hypothesized that the LIN28-let-7 axis regulates proliferation-associated genes in sheep trophectoderm in vivo. Day 9-hatched sheep blastocysts were incubated with lentiviral particles to deliver shRNA targeting LIN28 specifically to trophectoderm cells. At day 16, conceptus elongation was significantly reduced in LIN28A and LIN28B knockdowns. Let-7 miRNAs were significantly increased and IGF2BP1-3, HMGA1, ARID3B, and c-MYC were decreased in trophectoderm from knockdown conceptuses. Ovine trophoblast (OTR) cells derived from day 16 trophectoderm are a useful tool for in vitro experiments. Surprisingly, LIN28 was significantly reduced and let-7 miRNAs increased after only a few passages of OTR cells, suggesting these passaged cells represent a more differentiated phenotype. To create an OTR cell line more similar to day 16 trophectoderm we overexpressed LIN28A and LIN28B, which significantly decreased let-7 miRNAs and increased IGF2BP1-3, HMGA1, ARID3B, and c-MYC compared to control. This is the first study showing the role of the LIN28-let-7 axis in trophoblast proliferation and conceptus elongation in vivo. These results suggest that reduced LIN28 during early placental development can lead to reduced trophoblast proliferation and sheep conceptus elongation at a critical period for successful establishment of pregnancy.

Role of Activated Platelets in the Homing, Maturation, and Differentiation of Endotheleal Progenitor Cells (EPCs) to Vascular Subendotheleal Matrix.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3938-3938
Author(s):  
Eli I. Lev ◽  
Jing-fei Dong ◽  
Marcin Bujak ◽  
Khatira Aboulfatova ◽  
Neal S. Kleiman ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Vascular Injury ◽  
Human Platelets ◽  
In Vitro Experiments ◽  
Cell Markers ◽  
Femoral Arteries ◽  
In Vivo Experiments

Abstract We and others have found that platelets play an important role in the recruitment of endothelial progenitor cells to sights of vascular injury. However, it is not clear whether the EPCs mature and differentiate to endothelial cells following recruitment to the vascular injury sites. In addition, there is limited in vivo data to support the role of EPCs in re-endothlialization following vascular injury. We conducted in vitro experiments to investigate the maturation of EPCs on platelet based-media and in vivo experiments to evaluate the recruitment of EPCs following vascular injury. In in vitro experiments human EPCs were isolated from donated buffy coats by magnetic microbeads and flow cytometry cell sorting using CD133 and VEGFR-2, respectively, as cell markers. Isolated viable EPCs (CD133+, VEGFR-2+ cells) were plated on human fibronectin or a monolayer of washed human platelets. Cell colonies were counted 7 days after plating and stained for the endothelial cell markers CD31 (PECAM-1) and CD144 (VE-cadherin). The mean number of colony-forming cells was 35±2.6 colonies/106 cells on platelets, which was significantly higher than 18±4.2 colonies/106 cells on fibronectin (n = 4, P<0.01). Apart from the difference in colony numbers, the EPC colonies grew faster on the platelet substrate, were larger, and had more spindle-shaped cells (Figure 1 - staining of EPC colonies for CD31 and CD144). In the in vivo experiments a model of transluminal injury to mouse femoral arteries was used. Femoral artery denudation was performed by 0.25-mm-diameter angioplasty guidewire. Injured femoral arteries were compared to the contra-lateral controls (uninjured), and were harvested 1.5 hours following the injury and immunostaining performed with an anti-VEGFR-2 antibody. Four experiments showed a markedly higher number of VEGFR-2+ cells in the artery that has undergone denudation. These experiments indicate that a media composed of platelets promotes the maturation and differentiation of EPCs. Furthermore, in vivo, EPCs are recruited early following vascular injury. Thus, homing, maturation, and differentiation of EPCs are mediated by platelets.

scholarly journals YPR139c/LOA1encodes a novel lysophosphatidic acid acyltransferase associated with lipid droplets and involved in TAG homeostasis

2012 ◽  
Vol 23 (2) ◽  
pp. 233-246 ◽  
Author(s):  
Sophie Ayciriex ◽  
Marina Le Guédard ◽  
Nadine Camougrand ◽  
Gisèle Velours ◽  
Mario Schoene ◽  
...  
Keyword(s):  
Lysophosphatidic Acid ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
In Vitro Assays ◽  
Metabolic Labeling ◽  
Lysophosphatidic Acid Acyltransferase ◽  
Escherichia Coli Cells ◽  
Type Strains

For many years, lipid droplets (LDs) were considered to be an inert store of lipids. However, recent data showed that LDs are dynamic organelles playing an important role in storage and mobilization of neutral lipids. In this paper, we report the characterization of LOA1 (alias VPS66, alias YPR139c), a yeast member of the glycerolipid acyltransferase family. LOA1 mutants show abnormalities in LD morphology. As previously reported, cells lacking LOA1 contain more LDs. Conversely, we showed that overexpression results in fewer LDs. We then compared the lipidome of loa1Δ mutant and wild-type strains. Steady-state metabolic labeling of loa1Δ revealed a significant reduction in triacylglycerol content, while phospholipid (PL) composition remained unchanged. Interestingly, lipidomic analysis indicates that both PLs and glycerolipids are qualitatively affected by the mutation, suggesting that Loa1p is a lysophosphatidic acid acyltransferase (LPA AT) with a preference for oleoyl-CoA. This hypothesis was tested by in vitro assays using both membranes of Escherichia coli cells expressing LOA1 and purified proteins as enzyme sources. Our results from purification of subcellular compartments and proteomic studies show that Loa1p is associated with LD and active in this compartment. Loa1p is therefore a novel LPA AT and plays a role in LD formation.

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