Name: lipid droplet isolation for quantitative mass spectrometry analysis
Uploaded: 2017-04-17T13:00:00
Description: Watch this Scientific Journal Video about Lipid Droplet Isolation for Quantitative Mass Spectrometry Analysis at JoVE.com

We thank R. Bartenschlager (University of Heidelberg) for the Jc1 constructs, C.M. Rice (Rockefeller University) for the Huh7.5 cells, J. McLauchlan (Medical Research Council Virology Unit) for the JFH1 construct, T. Wakita (National Institute of Infectious Diseases, Japan) for the JFH1, and B. Webster and W.C. Greene (Gladstone Institute of Virology and Immunology) for the HCVcc reporter constructs. This work was supported by funds from the DFG (HE 6889/2-1 (EH), INST 337/15-1 2013, and INST 337/16-1 2013 (HS)). The Heinrich Pette Institute, Leibniz Institute for Experimental Virology is supported by the Free and Hanseatic City of Hamburg and the Federal Ministry of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

1. Preparation of Media for Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC)
NOTE: Here, the SILAC Protein Quantitation Kit - DMEM supplemented with 50 mg of 13C6 L-Arginine-HCl was used for SILAC labeling. The dialyzed Fetal Calf Serum (FCS) is provided with the SILAC Protein Quantitation Kit.
<ol>
	<li>Remove 50 mL from each bottle of DMEM medium and add 50 mL of dialyzed FCS.</li>
	<li>Dissolve 50 mg of 13C6 L-Lysine-2HCl and 50 ...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ins+and+outs+of+hepatitis+C+virus+entry+and+assembly.">The ins and outs of hepatitis C virus entry and assembly.</a> Nat Rev Microbiol. 11 (10), 688-700 (2013).</li><li>Barba, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+C+virus+core+protein+shows+a+cytoplasmic+localization+and+associates+to+cellular+lipid+storage+droplets.">Hepatitis C virus core protein shows a cytoplasmic localization and associates to cellular lipid storage droplets.</a> Proc Natl Acad Sci U S A. 94 (4), 1200-1205 (1997).</li><li>Shi, S. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+C+virus+NS5A+colocalizes+with+the+core+protein+on+lipid+droplets+and+interacts+with+apolipoproteins.">Hepatitis C virus NS5A colocalizes with the core protein on lipid droplets and interacts with apolipoproteins.</a> Virology. 292 (2), 198-210 (2002).</li><li>Herker, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+hepatitis+C+virus+particle+formation+requires+diacylglycerol+acyltransferase-1.">Efficient hepatitis C virus particle formation requires diacylglycerol acyltransferase-1.</a> Nat Med. 16 (11), 1295-1298 (2010).</li><li>Camus, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diacylglycerol+acyltransferase-1+localizes+hepatitis+C+virus+NS5A+protein+to+lipid+droplets+and+enhances+NS5A+interaction+with+the+viral+capsid+core.">Diacylglycerol acyltransferase-1 localizes hepatitis C virus NS5A protein to lipid droplets and enhances NS5A interaction with the viral capsid core.</a> J Biol Chem. 288 (14), 9915-9923 (2013).</li><li>Miyanari, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+lipid+droplet+is+an+important+organelle+for+hepatitis+C+virus+production.">The lipid droplet is an important organelle for hepatitis C virus production.</a> Nat Cell Biol. 9 (9), 1089-1097 (2007).</li><li>Boulant, S., Targett-Adams, P., McLauchlan, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disrupting+the+association+of+hepatitis+C+virus+core+protein+with+lipid+droplets+correlates+with+a+loss+in+production+of+infectious+virus.">Disrupting the association of hepatitis C virus core protein with lipid droplets correlates with a loss in production of infectious virus.</a> J Gen Virol. 88 (Pt 8), 2204-2213 (2007).</li><li>Vogt, D. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipid+droplet-binding+protein+TIP47+regulates+hepatitis+C+Virus+RNA+replication+through+interaction+with+the+viral+NS5A+protein.">Lipid droplet-binding protein TIP47 regulates hepatitis C Virus RNA replication through interaction with the viral NS5A protein.</a> PLoS Pathog. 9 (4), e1003302 (2013).</li><li>Ploen, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TIP47+plays+a+crucial+role+in+the+life+cycle+of+hepatitis+C+virus.">TIP47 plays a crucial role in the life cycle of hepatitis C virus.</a> J Hepatol. 58 (6), 1081-1088 (2013).</li><li>Ploen, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TIP47+is+associated+with+the+hepatitis+C+virus+and+its+interaction+with+Rab9+is+required+for+release+of+viral+particles.">TIP47 is associated with the hepatitis C virus and its interaction with Rab9 is required for release of viral particles.</a> Eur J Cell Biol. 92 (12), 374-382 (2013).</li><li>Rosch, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+Lipid+Droplet+Proteome+Analysis+Identifies+Annexin+A3+as+a+Cofactor+for+HCV+Particle+Production.">Quantitative Lipid Droplet Proteome Analysis Identifies Annexin A3 as a Cofactor for HCV Particle Production.</a> Cell Rep. 16 (12), 3219-3231 (2016).</li><li>Kwiatkowski, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+extraction+of+proteins+from+tissues+using+desorption+by+impulsive+vibrational+excitation.">Ultrafast extraction of proteins from tissues using desorption by impulsive vibrational excitation.</a> Angew Chem Int Ed Engl. 54 (1), 285-288 (2015).</li><li>Webster, B., Ott, M., Greene, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evasion+of+superinfection+exclusion+and+elimination+of+primary+viral+RNA+by+an+adapted+strain+of+hepatitis+C+virus.">Evasion of superinfection exclusion and elimination of primary viral RNA by an adapted strain of hepatitis C virus.</a> J Virol. 87 (24), 13354-13369 (2013).</li><li>Shevchenko, A., Tomas, H., Havlis, J., Olsen, J. V., Mann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-gel+digestion+for+mass+spectrometric+characterization+of+proteins+and+proteomes.">In-gel digestion for mass spectrometric characterization of proteins and proteomes.</a> Nat Protoc. 1 (6), 2856-2860 (2006).</li><li>Ting, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Normalization+and+statistical+analysis+of+quantitative+proteomics+data+generated+by+metabolic+labeling.">Normalization and statistical analysis of quantitative proteomics data generated by metabolic labeling.</a> Mol Cell Proteomics. 8 (10), 2227-2242 (2009).</li><li>Brasaemle, D. 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Here, we describe a protocol to isolate lipid droplets for quantitative lipid droplet proteome analysis to compare the enrichment and depletion of proteins associated with lipid droplets under diverse culture conditions, such as viral infections. As an alternative method, the proteome analysis can be performed with label-free quantifications based on total peak intensities. This method has no dynamic range limitation and avoids metabolic problems. The advantage of the SILAC approach is that the samples are pooled prior l...

Lipid droplets are highly dynamic cytoplasmic (and nuclear) cell organelles composed of a core of neutral lipids (triglycerides (TG) and cholesterol ester (CE)) enclosed by a monolayer of phospholipids with embedded proteins1. All cell types produce lipid droplets, but they vary in size, lipid composition, and protein decoration. Lipid droplets fulfill diverse functions, including serving as energy and membrane precursor reservoirs or as protein deposits. In addition, through the uptake of lipids, they protect cells from lipotoxicity, release lipids as signaling molecules, and are involved in protein degradation and endoplasmic reticulum (ER) stress responses2. As such, a host of proteins bind to lipid droplets and govern their generation, degradation, trafficking, and interaction with other organelles. Among them are the perilipin family of bona fide lipid droplet binding proteins (PLIN1-5)3.
Lipid droplet biogenesis likely starts at the ER, where ER-resident enzymes catalyze the synthesis of neutral lipids that accumulate within the membrane bilayer, forming a lens of neutral lipids, a process that was recently visualized nicely in yeast4. Membrane bending and elevated phosphatidic acid and diacylglycerol levels are then thought to attract proteins involved in phospholipid biosynthesis, as the simultaneous synthesis of the core neutral lipids and the shielding phospholipids is required for lipid droplet generation5. Enzymes harboring transmembrane domains that reside at the ER catalyze this process. Expansion to large lipid droplets requires the activity of a different class of lipid-synthesizing enzymes that harbor an amphipathic helix and can thus travel from the ER to lipid droplets. The mobilization of lipids from lipid droplets occurs through the local activation of the triglyceride and diacylglycerol lipases adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) or by different autophagic pathways, such as macro- and microlipophagy or chaperone-mediated autophagy6. Lipid droplets interact with other cellular organelles, such as mitochondria (for beta-oxidation and lipid synthesis) and ER (for lipid synthesis and protein trafficking), but also with lysosomes, endosomes, and the vacuoles induced by intracellular bacteria7. Indeed bacteria, viruses, and even parasites target lipid droplets for replication and persistence, among them HCV8.
HCV infection is one of the leading causes of liver-related morbidity and mortality worldwide, accounting for approximately 0.5 million deaths per year9. The true number of HCV infections is unknown, but recent estimates suggest that 130 - 150 million people are chronically infected. No vaccine exists, but the recently approved direct-acting antivirals dramatically increase therapeutic responses compared to the standard interferon-based therapy. However, worldwide, the treatment of patients will likely be restricted due to the extremely high costs of the new therapeutics. About half of all individuals chronically infected with HCV develop fatty liver disease (steatosis), a condition characterized by the excessive accumulation of lipid droplets in hepatocytes. Intriguingly, lipid droplets also emerged as vital cellular organelles for HCV replication, putatively serving as viral assembly sites10,11.
In HCV-infected cells, the viral protein core and NS5A localize to lipid droplets in a process that depends on triglyceride biosynthesis, as inhibitors of diacylglycerol acyltransferase-1 (DGAT1) impair trafficking to lipid droplets and subsequent HCV particle production12,13,14,15. In addition, mutations in the lipid droplet-binding domains of either core or NS5A suppress HCV assembly16,17. Core and NS5A then recruit all other viral proteins, as well as viral RNA replication complexes, to membranes closely associated with lipid droplets16. A concerted action of all viral proteins is required for the successful production of infectious viral progeny10,11. The structural proteins are part of the virions, and the nonstructural proteins promote the protein-protein interactions required for this process. Intriguingly, the bona fide lipid droplet-binding protein PLIN3/TIP47 is required for both HCV RNA replication and the release of virions18,19,20. Despite these recent advances, the mechanistic details, especially of virus-host interactions during the late stages of HCV replication, remain ill-defined, and the precise function of the lipid droplets is unknown.
Here, we describe a method to isolate lipid droplets for the quantitative mass spectrometry of associated proteins. Using this method, we found profound changes in the lipid droplet proteome during HCV infection and identified annexin A3 as a host protein that co-fractionates with lipid droplets and is required for efficient HCV maturation21.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>SILAC Protein Quantitation Kit - DMEM</td>
			<td>Thermo Fisher</td>
			<td>89983&#160;</td>
		</tr>
		<tr>
			<td>13C6 L-Arginine-HCl 50 mg</td>
			<td>Thermo Fisher</td>
			<td>88210&#160;</td>
		</tr>
		<tr>
			<td>Roti-Load 1</td>
			<td>Roth GmbH</td>
			<td>K929.1</td>
		</tr>
		<tr>
			<td>Roti-Blue 5x-Concentrate</td>
			<td>Roth GmbH</td>
			<td>A152.2&#160;</td>
		</tr>
		<tr>
			<td>10x SDS-Tris-Glycine - Buffer&#160;</td>
			<td>Geyer Th. GmbH &#38; Co.KG&#160;</td>
			<td>A1415,0250&#160;</td>
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		<tr>
			<td>GlutaMAX (100x)</td>
			<td>Life Technologies GmbH&#160;</td>
			<td>350500038&#160;</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin Solution for Cell Culture</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>P4333-100ml&#160;</td>
		</tr>
		<tr>
			<td>PBS 1x Dulbeccos Phosphate Buffered Saline</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>D8537&#160;</td>
		</tr>
		<tr>
			<td>Trypsin-EDTA</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>T3924-100ML&#160;</td>
		</tr>
		<tr>
			<td>Sodium Chloride BioChemica</td>
			<td>AppliChem GmbH</td>
			<td>A1149,1000</td>
		</tr>
		<tr>
			<td>Tris Ultrapure&#160;&#160;</td>
			<td>AppliChem GmbH</td>
			<td>A1086,5000A&#160;</td>
		</tr>
		<tr>
			<td>EDTA BioChemica</td>
			<td>AppliChem GmbH</td>
			<td>A1103,0250</td>
		</tr>
		<tr>
			<td>Protease Inhibitor Cocktail 5ml</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>P8340-5ML&#160;</td>
		</tr>
		<tr>
			<td>D(+)-Sucrose BioChemica</td>
			<td>AppliChem GmbH</td>
			<td>A3935,1000</td>
		</tr>
		<tr>
			<td>Hydrochloric acid 37% pure Ph. Eur., NF</td>
			<td>AppliChem GmbH</td>
			<td>A0625</td>
		</tr>
		<tr>
			<td>DC Protein Assay&#160;</td>
			<td>Bio-Rad Laboratoris GmbH&#160;</td>
			<td>500-0116&#160;</td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>AppliChem GmbH</td>
			<td>151339</td>
		</tr>
		<tr>
			<td>SDS Ultrapure</td>
			<td>AppliChem GmbH</td>
			<td>A1112</td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>AppliChem GmbH</td>
			<td>A2331</td>
		</tr>
		<tr>
			<td>&#946;-Mercaptoethanol&#160;</td>
			<td>AppliChem GmbH</td>
			<td>A4338</td>
		</tr>
		<tr>
			<td>Blasticidin</td>
			<td>Invivogen</td>
			<td>ant-bl-1&#160;</td>
		</tr>
		<tr>
			<td>Potassium Chloride&#160;</td>
			<td>AppliChem GmbH</td>
			<td>A1039</td>
		</tr>
		<tr>
			<td>Phenylmethanesulfonyl Fluoride&#160;</td>
			<td>AppliChem GmbH</td>
			<td>A0999</td>
		</tr>
		<tr>
			<td>Potassium Phosphate Monobasic</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>221309</td>
		</tr>
		<tr>
			<td>Dipotassium Hydrogenphosphate</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>P3786&#160;</td>
		</tr>
		<tr>
			<td>DTT&#160;</td>
			<td>AppliChem GmbH</td>
			<td>A2948</td>
		</tr>
		<tr>
			<td>NP-40</td>
			<td>AppliChem</td>
			<td>A1694</td>
		</tr>
		<tr>
			<td>TWEEN 20</td>
			<td>AppliChem</td>
			<td>A4974</td>
		</tr>
		<tr>
			<td>Nonfat dried milk powder</td>
			<td>AppliChem</td>
			<td>A0830</td>
		</tr>
		<tr>
			<td>Anti-ADFP/ ADRP&#160;</td>
			<td>abcam</td>
			<td>ab52355</td>
		</tr>
		<tr>
			<td>M6PRB1/TIP47 100&#181;g&#160;</td>
			<td>abcam</td>
			<td>ab47639</td>
		</tr>
		<tr>
			<td>Calreticulin, pAb 200 &#181;g</td>
			<td>Enzo Life Science GmbH&#160;</td>
			<td>ADI-SPA-600-F&#160;</td>
		</tr>
		<tr>
			<td>Anti-&#223;-Tubulin&#160;</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>T6074 200&#181;l &#160;</td>
		</tr>
		<tr>
			<td>Ethanol absolute</td>
			<td>Geyer Th. GmbH &#38; Co.KG&#160;</td>
			<td>A3678,0250 &#160;</td>
		</tr>
		<tr>
			<td>Anti-MnSOD</td>
			<td>Enzo Life Science GmbH&#160;</td>
			<td>ADI-SOD-110-F</td>
		</tr>
		<tr>
			<td>Anti-mouse HRP</td>
			<td>Thermo Fisher Pierce</td>
			<td>32430</td>
		</tr>
		<tr>
			<td>Anti-rabbit HRP</td>
			<td>Thermo Fisher&#160; Pierce</td>
			<td>32460</td>
		</tr>
		<tr>
			<td>Amersham Hyperfilm ECL</td>
			<td>GE Healthcare</td>
			<td>28906836</td>
		</tr>
		<tr>
			<td>Lumi-Light Western Blotting Substrate</td>
			<td>Sigma-Aldrich Chemie GmbH&#160;</td>
			<td>12015196001</td>
		</tr>
		<tr>
			<td>96 Well Cell Culture Plate</td>
			<td>Greiner Bio-One GmbH&#160;</td>
			<td>655 180&#160;</td>
		</tr>
		<tr>
			<td>Terumo Syringe 1 ml</td>
			<td>Terumo</td>
			<td>SS-01T</td>
		</tr>
		<tr>
			<td>Filtropur BT 50, 500 ml, 0.45 &#181;m&#160;</td>
			<td>SARSTEDT&#160;</td>
			<td>83.1823.100&#160;</td>
		</tr>
		<tr>
			<td>Mini-PROTEAN TGX Precast Gels, Any kD resolving gel</td>
			<td>Bio-Rad Laboratoris GmbH&#160;</td>
			<td>456-9034&#160;</td>
		</tr>
		<tr>
			<td>6 Well Cell Culture Plate</td>
			<td>Greiner Bio-One GmbH&#160;</td>
			<td>657160&#160;</td>
		</tr>
		<tr>
			<td>Dishes Nunclon 150/20&#160;</td>
			<td>Fisher Scientific GmbH&#160;</td>
			<td>10098720 - 168381&#160;</td>
		</tr>
		<tr>
			<td>Cell Scraper</td>
			<td>neoLab Migge GmbH&#160;</td>
			<td>C-8120&#160;</td>
		</tr>
		<tr>
			<td>Tube, 50 ml</td>
			<td>Greiner Bio-One GmbH&#160;</td>
			<td>227261&#160;</td>
		</tr>
		<tr>
			<td>SafeSeal Tube RNase-free&#160;</td>
			<td>SARSTEDT&#160;</td>
			<td>72.706.400&#160;</td>
		</tr>
		<tr>
			<td>Ultra Clear Centrifuge Tubes 11 x 60 mm</td>
			<td>Beckman Coulter GmbH&#160;</td>
			<td>344062&#160;</td>
		</tr>
		<tr>
			<td>Suction Needles</td>
			<td>Transcodent</td>
			<td>6482</td>
		</tr>
		<tr>
			<td>Biosphere Fil. Tip 1000&#160;</td>
			<td>SARSTEDT&#160;</td>
			<td>70.762.211&#160;</td>
		</tr>
		<tr>
			<td>Biosphere Fil. Tip 200</td>
			<td>SARSTEDT&#160;</td>
			<td>70.760.211&#160;</td>
		</tr>
		<tr>
			<td>Biosphere Fil. Tip 10</td>
			<td>SARSTEDT&#160;</td>
			<td>70.1130.210&#160;</td>
		</tr>
		<tr>
			<td>Dounce Tissue Grinder</td>
			<td>Fisher Scientific GmbH&#160;</td>
			<td>11883722</td>
		</tr>
		<tr>
			<td>Pestles For Dounce All-Glass Tissue Grinders</td>
			<td>Fisher Scientific GmbH&#160;</td>
			<td>10389444</td>
		</tr>
		<tr>
			<td>Orbitrap Fusion</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Branson Sonifier 450</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Thermomixer comfort, with Thermoblock 1.5 ml</td>
			<td>Eppendorf</td>
			<td>5355&#160;000.127</td>
		</tr>
		<tr>
			<td>Mini-PROTEAN Tetra Cell, Mini Trans-Blot Module, and PowerPac Basic Power Supply,&#160;</td>
			<td>BioRad</td>
			<td>165-8033</td>
		</tr>
		<tr>
			<td>Mini-PROTEAN 3 Multi-Casting Chamber</td>
			<td>BioRad</td>
			<td>165-4110</td>
		</tr>
		<tr>
			<td>PowerPac HC Power Supply</td>
			<td>Biorad</td>
			<td>164-5052</td>
		</tr>
		<tr>
			<td>Centrifuge&#160;</td>
			<td>Eppendorf</td>
			<td>5424R</td>
		</tr>
		<tr>
			<td>Centrifuge&#160;</td>
			<td>Eppendorf</td>
			<td>5424</td>
		</tr>
		<tr>
			<td>Optima L-90K</td>
			<td>Beckman Coulter GmbH&#160;</td>
			<td>365670</td>
		</tr>
		<tr>
			<td>SW 60 Ti Rotor</td>
			<td>Beckman Coulter GmbH&#160;</td>
			<td>335649</td>
		</tr>
		<tr>
			<td>Infinite M1000 PRO</td>
			<td>Tecan</td>
			<td></td>
		</tr>
	</tbody>
</table>

lipid droplet isolation for quantitative mass spectrometry analysis

Lipid droplets are vital to the replication of a variety of different pathogens, most prominently the Hepatitis C Virus (HCV), as the putative site of virion morphogenesis. Quantitative lipid droplet proteome analysis can be used to identify proteins that localize to or are displaced from lipid droplets under conditions such as virus infections. Here, we describe a protocol that has been successfully used to characterize the changes in the lipid droplet proteome following infection with HCV. We use Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC) and thus label the complete proteome of one population of cells with &#34;heavy&#34; amino acids to quantitate the proteins by mass spectrometry. For lipid droplet isolation, the two cell populations (i.e.&#160;HCV-infected/&#34;light&#34; amino acids and uninfected control/&#34;heavy&#34; amino acids) are mixed 1:1 and lysed mechanically in hypotonic buffer. After removing the nuclei and cell debris by low speed centrifugation, lipid droplet-associated proteins are enriched by two subsequent ultracentrifugation steps followed by three washing steps in isotonic buffer. The purity of the lipid droplet fractions is analyzed by western blotting with antibodies recognizing different subcellular compartments. Lipid droplet-associated proteins are then separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Coomassie staining. After tryptic digest, the peptides are quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Using this method, we identified proteins recruited to lipid droplets upon HCV infection that might represent pro- or antiviral host factors. Our method can be applied to a variety of different cells and culture conditions, such as infection with pathogens, environmental stress, or drug treatment.

Lipid droplets are vital to HCV&#160;infection as the putative sites of virion assembly, but the molecular mechanisms of morphogenesis and egress of virions are largely unknown. To identify novel host dependency factors involved in that process, we performed quantitative lipid droplet proteome analysis of HCV-infected cells21 (Figure 1A). We established a protocol for purifying lipid droplets and routinely detected a strong enrichment of the lipid ...

Watch this Scientific Journal Video about Lipid Droplet Isolation for Quantitative Mass Spectrometry Analysis at JoVE.com

Lipid Droplet Isolation for Quantitative Mass Spectrometry Analysis

Lipid droplets are important organelles for the replication of several pathogens, including the Hepatitis C Virus (HCV). We describe a method to isolate lipid droplets for quantitative mass spectrometry of associated proteins; it can be used under a variety of conditions, such as virus infection, environmental stress, or drug treatment.

Lipid droplets are vital to the replication of a variety of different pathogens, most prominently the Hepatitis C Virus (HCV), as the putative site of ...

Research

JoVE Journal

Biochemistry

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