scholarly journals Lipidome analysis of rotavirus-infected cells confirms the close interaction of lipid droplets with viroplasms

2013 ◽  
Vol 94 (7) ◽  
pp. 1576-1586 ◽  
Author(s):  
Eleanor R. Gaunt ◽  
Qifeng Zhang ◽  
Winsome Cheung ◽  
Michael J. O. Wakelam ◽  
Andrew M. L. Lever ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
Lipid Droplets ◽  
Close Interaction ◽  
Associated Proteins ◽  
Dsrna Genome ◽  
Infected Cells ◽  
Lipidome Analysis ◽  
Equilibrium Ultracentrifugation ◽  
Globally Distributed ◽  
Infants And Young Children

Rotaviruses (RVs) cause acute gastroenteritis in infants and young children, and are globally distributed. Within the infected host cell, RVs establish replication complexes in viroplasms (‘viral factories’) to which lipid droplet organelles are recruited. To further understand this recently discovered phenomenon, the lipidomes of RV-infected and uninfected MA104 cells were investigated. Cell lysates were subjected to equilibrium ultracentrifugation through iodixanol gradients. Fourteen different classes of lipids were differentiated by mass spectrometry. The concentrations of virtually all lipids were elevated in RV-infected cells. Fractions of low density (1.11–1.15 g ml−1), in which peaks of the RV dsRNA genome and lipid droplet- and viroplasm-associated proteins were observed, contained increased amounts of lipids typically found concentrated in the cellular organelle lipid droplets, confirming the close interaction of lipid droplets with viroplasms. A decrease in the ratio of the amounts of surface to internal components of lipid droplets upon RV infection suggested that the lipid droplet–viroplasm complexes became enlarged.

scholarly journals HSD17B13: A Potential Therapeutic Target for NAFLD

2022 ◽  
Vol 8 ◽  
Author(s):  
Hai-bo Zhang ◽  
Wen Su ◽  
Hu Xu ◽  
Xiao-yan Zhang ◽  
You-fei Guan
Keyword(s):  
Liver Disease ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Critical Role ◽  
Chronic Liver ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Nonalcoholic Fatty Liver ◽  
Promising Target ◽  
Associated Proteins

Nonalcoholic fatty liver disease (NAFLD), especially in its inflammatory form (steatohepatitis, NASH), is closely related to the pathogenesis of chronic liver disease. Despite substantial advances in the management of NAFLD/NASH in recent years, there are currently no efficacious therapies for its treatment. The biogenesis and expansion of lipid droplets (LDs) are critical pathophysiological processes in the development of NAFLD/NASH. In the past decade, increasing evidence has demonstrated that lipid droplet-associated proteins may represent potential therapeutic targets for the treatment of NAFLD/NASH given the critical role they play in regulating the biogenesis and metabolism of lipid droplets. Recently, HSD17B13, a newly identified liver-enriched, hepatocyte-specific, lipid droplet-associated protein, has been reported to be strongly associated with the development and progression of NAFLD/NASH in both mice and humans. Notably, human genetic studies have repeatedly reported a robust association of HSD17B13 single nucleotide polymorphisms (SNPs) with the occurrence and severity of NAFLD/NASH and other chronic liver diseases (CLDs). Here we briefly overview the discovery, tissue distribution, and subcellular localization of HSD17B13 and highlight its important role in promoting the pathogenesis of NAFLD/NASH in both experimental animal models and patients. We also discuss the potential of HSD17B13 as a promising target for the development of novel therapeutic agents for NAFLD/NASH.

Subcellular localization of skeletal muscle lipid droplets and PLIN family proteins OXPAT and ADRP at rest and following contraction in rat soleus muscle

2012 ◽  
Vol 302 (1) ◽  
pp. R29-R36 ◽  
Author(s):  
Rebecca E. K. MacPherson ◽  
Eric A. F. Herbst ◽  
Erica J. Reynolds ◽  
Rene Vandenboom ◽  
Brian D. Roy ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Lipid Droplet ◽  
Protein Interactions ◽  
Lipid Droplets ◽  
Droplet Surface ◽  
Protein Protein Interactions ◽  
Muscle Lipid ◽  
Droplet Distribution ◽  
Associated Proteins ◽  
Skeletal Muscle Lipid

Skeletal muscle lipid droplet-associated proteins (PLINs) are thought to regulate lipolysis through protein-protein interactions on the lipid droplet surface. In adipocytes, PLIN2 [adipocyte differentiation-related protein (ADRP)] is found only on lipid droplets, while PLIN5 (OXPAT, expressed only in oxidative tissues) is found both on and off the lipid droplet and may be recruited to lipid droplet membranes when needed. Our purpose was to determine whether PLIN5 is recruited to lipid droplets with contraction and to investigate the myocellular location and colocalization of lipid droplets, PLIN2, and PLIN5. Rat solei were isolated, and following a 30-min equilibration period, they were assigned to one of two groups: 1) 30 min of resting incubation and 2) 30 min of stimulation ( n = 10 each). Immunofluorescence microscopy was used to determine subcellular content, distribution, and colocalization of lipid droplets, PLIN2, and PLIN5. There was a main effect for lower lipid and PLIN2 content in stimulated compared with rested muscles ( P < 0.05). Lipid droplet distribution declined exponentially from the sarcolemma to the fiber center in the rested muscles ( P = 0.001, r2= 0.99) and linearly in stimulated muscles (slope = −0.0023 ± 0.0006, P < 0.001, r2= 0.93). PLIN2 distribution declined exponentially from the sarcolemma to the fiber center in both rested and stimulated muscles ( P < 0.0001, r2= 0.99 rest; P = 0.0004, r2= 0.98 stimulated), while PLIN5 distribution declined linearly (slope = −0.0085 ± 0.0009, P < 0.0001, r2= 0.94 rest; slope=−0.0078 ± 0.0010, P = 0.0003, r2= 0.91 stimulated). PLIN5-lipid droplets colocalized at rest with no difference poststimulation ( P = 0.47; rest r2= 0.55 ± 0.02, stimulated r2= 0.58 ± 0.03). PLIN2-lipid droplets colocalized at rest with no difference poststimulation ( P = 0.48; rest r2= 0.66 ± 0.02, stimulated r2= 0.65 ± 0.02). Contrary to our hypothesis, these results show that PLIN5 is not recruited to lipid droplets with contraction in isolated skeletal muscle.

scholarly journals Active involvement of micro-lipid droplets and lipid-droplet-associated proteins in hormone-stimulated lipolysis in adipocytes

2012 ◽  
Vol 125 (24) ◽  
pp. 6127-6136 ◽  
Author(s):  
T. Hashimoto ◽  
H. Segawa ◽  
M. Okuno ◽  
H. Kano ◽  
H.-o. Hamaguchi ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
Lipid Droplets ◽  
Active Involvement ◽  
Associated Proteins

Triglyceride containing lipid droplets and lipid droplet-associated proteins

2008 ◽  
Vol 19 (5) ◽  
pp. 441-447 ◽  
Author(s):  
Sven-Olof Olofsson ◽  
Pontus Boström ◽  
Linda Andersson ◽  
Mikael Rutberg ◽  
Malin Levin ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
Lipid Droplets ◽  
Associated Proteins

scholarly journals A Genetically Engineered Rotavirus NSP2 Phosphorylation Mutant Impaired in Viroplasm Formation and Replication Shows an Early Interaction between vNSP2 and Cellular Lipid Droplets

2020 ◽  
Vol 94 (15) ◽  
Author(s):  
Jeanette M. Criglar ◽  
Sue E. Crawford ◽  
Boyang Zhao ◽  
Hunter G. Smith ◽  
Fabio Stossi ◽  
...  
Keyword(s):  
Virus Replication ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Reverse Genetics ◽  
Nonstructural Protein ◽  
Genetically Engineered ◽  
Wild Type ◽  
Nonstructural Proteins ◽  
Nonstructural Protein 2 ◽  
Infected Cells

ABSTRACT Many RNA viruses replicate in cytoplasmic compartments (virus factories or viroplasms) composed of viral and cellular proteins, but the mechanisms required for their formation remain largely unknown. Rotavirus (RV) replication in viroplasms requires interactions between virus nonstructural proteins NSP2 and NSP5, which are associated with components of lipid droplets (LDs). We previously identified two forms of NSP2 in RV-infected cells, a cytoplasmically dispersed form (dNSP2) and a viroplasm-specific form (vNSP2), which interact with hypophosphorylated and hyperphosphorylated NSP5, respectively, indicating that a coordinated phosphorylation cascade controls viroplasm assembly. The cellular kinase CK1α phosphorylates NSP2 on serine 313, triggering the localization of vNSP2 to sites of viroplasm assembly and its association with hyperphosphorylated NSP5. Using reverse genetics, we generated a rotavirus with a phosphomimetic NSP2 (S313D) mutation to directly evaluate the role of CK1α NSP2 phosphorylation in viroplasm formation. Recombinant rotavirus NSP2 S313D (rRV NSP2 S313D) is significantly delayed in viroplasm formation and in virus replication and interferes with wild-type RV replication in coinfection. Taking advantage of the delay in viroplasm formation, the NSP2 phosphomimetic mutant was used as a tool to observe very early events in viroplasm assembly. We show that (i) viroplasm assembly correlates with NSP5 hyperphosphorylation and (ii) vNSP2 S313D colocalizes with RV-induced LDs without NSP5, suggesting that vNSP2 phospho-S313 is sufficient for interacting with LDs and may be the virus factor required for RV-induced LD formation. Further studies with the rRV NSP2 S313D virus are expected to reveal new aspects of viroplasm and LD initiation and assembly. IMPORTANCE Reverse genetics was used to generate a recombinant rotavirus with a single phosphomimetic mutation in nonstructural protein 2 (NSP2 S313D) that exhibits delayed viroplasm formation, delayed replication, and an interfering phenotype during coinfection with wild-type rotavirus, indicating the importance of this amino acid during virus replication. Exploiting the delay in viroplasm assembly, we found that viroplasm-associated NSP2 colocalizes with rotavirus-induced lipid droplets prior to the accumulation of other rotavirus proteins that are required for viroplasm formation and that NSP5 hyperphosphorylation is required for viroplasm assembly. These data suggest that NSP2 phospho-S313 is sufficient for interaction with lipid droplets and may be the virus factor that induces lipid droplet biogenesis in rotavirus-infected cells. Lipid droplets are cellular organelles critical for the replication of many viral and bacterial pathogens, and thus, understanding the mechanism of NSP2-mediated viroplasm/lipid droplet initiation and interaction will lead to new insights into this important host-pathogen interaction.

scholarly journals Ancient ubiquitous protein-1 mediates sterol-induced ubiquitination of 3-hydroxy-3-methylglutaryl CoA reductase in lipid droplet–associated endoplasmic reticulum membranes

2013 ◽  
Vol 24 (3) ◽  
pp. 169-183 ◽  
Author(s):  
Youngah Jo ◽  
Isamu Z. Hartman ◽  
Russell A. DeBose-Boyd
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Regulatory Element ◽  
Cholesterol Homeostasis ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Element Binding Protein ◽  
Associated Proteins ◽  
Coa Reductase

Sterol-induced binding to Insigs in endoplasmic reticulum (ER) membranes triggers ubiquitination of the cholesterol biosynthetic enzyme 3-hydroxy-3-methylglutaryl CoA reductase. This ubiquitination, which is mediated by Insig-associated ubiquitin ligases gp78 and Trc8, is obligatory for extraction of reductase from lipid droplet–associated ER membranes into the cytosol for proteasome-mediated, ER-associated degradation (ERAD). In this study, we identify lipid droplet–associated, ancient, ubiquitous protein-1 (Aup1) as one of several proteins that copurify with gp78. RNA interference (RNAi) studies show that Aup1 recruits the ubiquitin-conjugating enzyme Ubc7 to lipid droplets and facilitates its binding to both gp78 and Trc8. The functional significance of these interactions is revealed by the observation that RNAi-mediated knockdown of Aup1 blunts sterol-accelerated ubiquitination of reductase, which appears to occur in lipid droplet–associated membranes and subsequent ERAD of the enzyme. In addition, Aup1 knockdown inhibits ERAD of Insig-1, another substrate for gp78, as well as that of membrane-bound precursor forms of sterol-regulatory, element-binding protein-1 and -2, transcription factors that modulate expression of genes encoding enzymes required for cholesterol synthesis. Considered together, these findings not only implicate a role for Aup1 in maintenance of intracellular cholesterol homeostasis, but they also highlight the close connections among ERAD, lipid droplets, and lipid droplet–associated proteins.

scholarly journals Topography of Lipid Droplet-Associated Proteins: Insights from Freeze-Fracture Replica Immunogold Labeling

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Horst Robenek ◽  
Insa Buers ◽  
Mirko J. Robenek ◽  
Oliver Hofnagel ◽  
Anneke Ruebel ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
Lipid Droplets ◽  
Spatial Organization ◽  
Freeze Fracture ◽  
Protein Composition ◽  
Immunogold Labeling ◽  
Intracellular Lipids ◽  
Associated Proteins ◽  
Developing Area ◽  
And Function

Lipid droplets are not merely storage depots for superfluous intracellular lipids in times of hyperlipidemic stress, but metabolically active organelles involved in cellular homeostasis. Our concepts on the metabolic functions of lipid droplets have come from studies on lipid droplet-associated proteins. This realization has made the study of proteins, such as PAT family proteins, caveolins, and several others that are targeted to lipid droplets, an intriguing and rapidly developing area of intensive inquiry. Our existing understanding of the structure, protein organization, and biogenesis of the lipid droplet has relied heavily on microscopical techniques that lack resolution and the ability to preserve native cellular and protein composition. Freeze-fracture replica immunogold labeling overcomes these disadvantages and can be used to define at high resolution the precise location of lipid droplet-associated proteins. In this paper illustrative examples of how freeze-fracture immunocytochemistry has contributed to our understanding of the spatial organization in the membrane plane and function of PAT family proteins and caveolin-1 are presented. By revisiting the lipid droplet with freeze-fracture immunocytochemistry, new perspectives have emerged which challenge prevailing concepts of lipid droplet biology and may hopefully provide a timely impulse for many ongoing studies.

scholarly journals Imaging cytoplasmic lipid droplets in vivo with fluorescent perilipin 2 and perilipin 3 knock-in zebrafish

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Meredith H Wilson ◽  
Stephen C Ekker ◽  
Steven Arthur Farber
Keyword(s):  
Lipid Droplet ◽  
Lipid Droplets ◽  
Cultured Cells ◽  
Droplet Dynamics ◽  
Associated Proteins ◽  
Perilipin 2 ◽  
Cytoplasmic Lipid Droplets ◽  
Endogenous Loci

Cytoplasmic lipid droplets are highly dynamic storage organelles that are critical for cellular lipid homeostasis. While the molecular details of lipid droplet dynamics are a very active area of investigation, this work has been primarily performed in cultured cells. Taking advantage of the powerful transgenic and in vivo imaging opportunities available in zebrafish, we built a suite of tools to study lipid droplets in real-time from the subcellular to the whole organism level. Fluorescently tagging the lipid-droplet-associated proteins, perilipin 2 and perilipin 3, in the endogenous loci permits visualization of lipid droplets in the intestine, liver, and adipose tissue. Using these tools, we found that perilipin 3 is rapidly loaded on intestinal lipid droplets following a high-fat meal and later replaced by perilipin 2. These powerful new tools will facilitate studies on the role of lipid droplets in different tissues, under different genetic and physiological manipulations, and in a variety of human disease models.

Thyroid Hormone Deficiency Modifies Hepatic Lipid Droplet Morphology and Molecular Properties in Lithogenic-Diet Supplemented Mice

2021 ◽  
Author(s):  
Irina Kube ◽  
Holger Jastrow ◽  
Dagmar Führer ◽  
Denise Zwanziger
Keyword(s):  
Gene Expression ◽  
Thyroid Hormone ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Molecular Properties ◽  
Hormone Deficiency ◽  
Hepatic Lipid ◽  
Lithogenic Diet ◽  
Associated Proteins ◽  
Droplet Morphology

Abstract Objective Thyroid hormones have been associated with a hepatic lipid lowering effect and thyroid function has been shown to play a substantial role in development of non-alcoholic fatty liver disease. Hepatic lipid droplets differ in the number, size and molecular properties depending on metabolic state or pathological condition. However, in how far thyroid hormone deficiency affects hepatic lipid droplet morphology and molecular properties is still poorly understood. Therefore, we performed a study in mice using a lithogenic diet model of steatohepatitis and modulated the thyroid hormone status. Methods Male and female three months old C57BL/6 mice were divided into a euthyroid (control), a lithogenic (litho) and a lithogenic+thyroid hormone deficient (litho+hypo) group and treated for six weeks. Hepatic transmission electron microscopy and gene expression analysis of lipid-droplet associated proteins were performed. Results Increased mean diameters of hepatic lipid droplets and a shift towards raised electron-density in lipid droplets was observed under thyroid hormone deficiency. Furthermore thyroid hormone deficiency altered hepatic expression of genes involved in lipophagy and triacylglycerol mobilization. Interestingly, while the impact of thyroid hormone deficiency on lipid droplet morphology seems to be sex-independent, hepatic lipid droplet-associated gene expression differed significantly between both sexes. Conclusion This study demonstrates that thyroid hormone deficiency alters hepatic lipid droplet morphology and hepatic gene expression of lipid droplet-associated proteins in a lithogenic diet mouse model of steatohepatitis.

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