title: COPI buds 60-nm lipid droplets from reconstituted water-phospholipid-triacylglyceride interfaces, suggesting a tension clamp function.
abstract: Intracellular trafficking between organelles is achieved by coat protein complexes, coat protomers, that bud vesicles from bilayer membranes. Lipid droplets are protected by a monolayer and thus seem unsuitable targets for coatomers. Unexpectedly, coat protein complex I (COPI) is required for lipid droplet targeting of some proteins, suggesting a possible direct interaction between COPI and lipid droplets. Here, we find that COPI coat components can bud 60-nm triacylglycerol nanodroplets from artificial lipid droplet (LD) interfaces. This budding decreases phospholipid packing of the monolayer decorating the mother LD. As a result, hydrophobic triacylglycerol molecules become more exposed to the aqueous environment, increasing LD surface tension. In vivo, this surface tension increase may prime lipid droplets for reactions with neighboring proteins or membranes. It provides a mechanism fundamentally different from transport vesicle formation by COPI, likely responsible for the diverse lipid droplet phenotypes associated with depletion of COPI subunits.
authors.affiliation: Department of Cell Biology, School of Medicine, Yale University, New Haven, CT 06520, USA.
authors.forename: Abdou Rachid
authors.initials: AR
authors.lastname: Thiam
authors.forename: Bruno
authors.initials: B
authors.lastname: Antonny
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Jérôme
authors.initials: J
authors.lastname: Delacotte
authors.forename: Florian
authors.initials: F
authors.lastname: Wilfling
authors.forename: Tobias C
authors.initials: TC
authors.lastname: Walther
authors.forename: Rainer
authors.initials: R
authors.lastname: Beck
authors.forename: James E
authors.initials: JE
authors.lastname: Rothman
authors.forename: Frédéric
authors.initials: F
authors.lastname: Pincet
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000235:genetics; D000818:Animals; D020755:Coat Protein Complex I / Q000737:chemistry*; D004926:Escherichia coli; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D008854:Microscopy, Electron; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010743:Phospholipids / Q000737:chemistry; D021381:Protein Transport / Q000502:physiology*; D061987:Sf9 Cells; D013050:Spectrometry, Fluorescence; D018411:Spodoptera; D013500:Surface Tension; D022161:Transport Vesicles / Q000737:chemistry*; D014280:Triglycerides / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D020755:Coat Protein Complex I; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D014280:Triglycerides; D014867:Water; D020823:ADP-Ribosylation Factor 1; C017251:1,2-oleoylphosphatidylcholine
keywords: buffer-in-oil drops; lipid droplet targetting; membrane tension; regulator
references.citation: Biochim Biophys Acta. 2013 Mar;1831(3):589-94
references.pmid: 23246574
references.citation: Biophys J. 2003 Mar;84(3):1977-84
references.pmid: 12609900
references.citation: J Cell Biol. 2008 Nov 17;183(4):725-35
references.pmid: 19015319
references.citation: Dev Cell. 2013 Feb 25;24(4):384-99
references.pmid: 23415954
references.citation: Cell. 1999 Feb 19;96(4):495-506
references.pmid: 10052452
references.citation: J Biol Chem. 2011 Aug 12;286(32):28235-46
references.pmid: 21680734
references.citation: PLoS Biol. 2008 Nov 25;6(11):e292
references.pmid: 19067489
references.citation: J Cell Biol. 2011 Jul 11;194(1):89-103
references.pmid: 21746853
references.citation: Proc Natl Acad Sci U S A. 1998 Sep 15;95(19):11199-204
references.pmid: 9736713
references.citation: J Biol Chem. 2002 Feb 22;277(8):6344-52
references.pmid: 11744721
references.citation: J Lipid Res. 2008 Nov;49(11):2283-301
references.pmid: 18757836
references.citation: J Cell Sci. 2009 Jun 1;122(Pt 11):1834-41
references.pmid: 19461073
references.citation: Cell. 2009 Nov 25;139(5):855-60
references.pmid: 19945371
references.citation: Biophys J. 1996 Mar;70(3):1112-21
references.pmid: 8785271
references.citation: J Proteome Res. 2007 Aug;6(8):3256-65
references.pmid: 17608402
references.citation: Proc Natl Acad Sci U S A. 2008 Sep 30;105(39):14763-8
references.pmid: 18824695
references.citation: Nature. 2008 May 29;453(7195):657-61
references.pmid: 18408709
references.citation: J Cell Sci. 2011 Jul 15;124(Pt 14):2424-37
references.pmid: 21693588
references.citation: Cell. 1991 Oct 18;67(2):239-53
references.pmid: 1680566
references.citation: Traffic. 2011 Jun;12(6):682-92
references.pmid: 21324056
references.citation: Trends Cell Biol. 2013 Jun;23(6):279-88
references.pmid: 23414967
references.citation: Mol Cell Biol. 2010 Mar;30(5):1231-42
references.pmid: 20038528
references.citation: Biochem Biophys Res Commun. 2005 Sep 16;335(1):117-23
references.pmid: 16054594
references.citation: PLoS One. 2011;6(7):e21889
references.pmid: 21789191
references.citation: Biochim Biophys Acta. 2009 Jun;1791(6):399-407
references.pmid: 18996222
references.citation: Proc Natl Acad Sci U S A. 1992 Jul 15;89(14):6408-12
references.pmid: 1631136
references.citation: J Lipid Res. 2009 Jan;50(1):3-21
references.pmid: 18952573
references.citation: Proc Natl Acad Sci U S A. 2008 Nov 4;105(44):16946-51
references.pmid: 18974217