title: S3-12, Adipophilin, and TIP47 package lipid in adipocytes.
abstract: Animals have evolved mechanisms to maintain circulating nutrient levels when energy demands exceed feeding opportunities. Mammals store most of their energy as triacylglycerol in the perilipin-coated lipid droplets of adipocytes. How newly synthesized triacylglycerol is delivered to perilipin-coated lipid droplets is poorly understood. Perilipin is a member of the evolutionarily related family of PAT proteins (Perilipin, Adipophilin, TIP47), which is defined by sequence similarity and association with lipid droplets. We previously showed that S3-12, which is also a member of this family, associates with a separate pool of lipid droplets that emerge when triacylglycerol storage is driven by adding oleate to the culture medium of adipocytes. Our current data extend these findings to demonstrate that nascent lipid droplets emerge with a coat composed of S3-12, TIP47, and adipophilin. After 100 min of oleate treatment, the nascent lipid droplets are more heterogeneous: S3-12 and TIP47 coat smaller, peripheral droplets and adipophilin coats a more medial population of droplets. Fractionation of untreated and oleate-treated adipocytes shows oleate-dependent redistribution of TIP47 and adipophilin from cytosolic fractions to the lipid droplet fraction. Inhibition of protein synthesis with cycloheximide does not block the oleate-induced formation of the nascent lipid droplets, nor does it prevent TAG accumulation. We suggest that the non-lipid droplet pools of S3-12, adipophilin, and TIP47 constitute a ready reservoir of coat proteins to permit rapid packaging of newly synthesized triacylglycerol and to maximize energy storage during nutrient excess.
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Nathan E
authors.initials: NE
authors.lastname: Wolins
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Quaynor
authors.forename: James R
authors.initials: JR
authors.lastname: Skinner
authors.forename: Marissa J
authors.initials: MJ
authors.lastname: Schoenfish
authors.forename: Anatoly
authors.initials: A
authors.lastname: Tzekov
authors.forename: Perry E
authors.initials: PE
authors.lastname: Bickel
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D019301:Oleic Acid / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D000070778:Perilipin-1; D000070780:Perilipin-2; D000070796:Perilipin-3; D000071229:Perilipin-4; D010750:Phosphoproteins / Q000737:chemistry; D011257:Pregnancy Proteins / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014280:Triglycerides / Q000378:metabolism; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005227:Fatty Acids; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D008055:Lipids; D008565:Membrane Proteins; C000602982:PLIN2 protein, human; C038196:PLIN3 protein, human; D010455:Peptides; D000070778:Perilipin-1; D000070780:Perilipin-2; D000070796:Perilipin-3; D000071229:Perilipin-4; D010750:Phosphoproteins; C000602983:Plin2 protein, mouse; C487119:Plin4 protein, mouse; D011257:Pregnancy Proteins; D011500:Protein Synthesis Inhibitors; D014280:Triglycerides; D033921:Vesicular Transport Proteins; D019301:Oleic Acid; D003513:Cycloheximide; D005947:Glucose