title: The proteome of cholesteryl-ester-enriched versus triacylglycerol-enriched lipid droplets.
abstract: Within cells, lipids are stored in the form of lipid droplets (LDs), consisting of a neutral lipid core, surrounded by a phospholipid monolayer and an outer layer of protein. LDs typically accumulate either triacylglycerol (TAG) and diacylglycerol or cholesteryl ester (CE), depending on the type of tissue. Recently, there has been an increased interest in the proteins that surround LDs. LD proteins have been found to be quite diverse, from structural proteins to metabolic enzymes, proteins involved in vesicular transport, and proteins that may play a role in LD formation. Previous proteomics analyses have focused on TAG-enriched LDs, whereas CE-enriched LDs have been largely ignored. Our study has compared the LD proteins from CE-enriched LDs to TAG-enriched LDs in steroidogenic cells. In primary rat granulosa cells loaded with either HDL to produce CE-enriched LDs or fatty acids to produce TAG-enriched LDs, 61 proteins were found to be elevated in CE-enriched LDs and 40 proteins elevated in TAG-enriched LDs with 278 proteins in similar amounts. Protein expression was further validated by selected reaction monitoring (SRM) mass spectrometry (MS). SRM verified expression of 25 of 27 peptides that were previously detected by tandem mass tagging MS. Several proteins were confirmed to be elevated in CE-enriched LDs by SRM including the intermediate filament vimentin. This study is the first to compare the proteins found on CE-enriched LDs with TAG-enriched LDs and constitutes the first step in creating a better understanding of the proteins found on CE-enriched LDs in steroidogenic cells.
authors.affiliation: Division of Endocrinology, Gerontology and Metabolism, Stanford University, Stanford, California, United States of America; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Victor K
authors.initials: VK
authors.lastname: Khor
authors.affiliation: Department of Chemical and Systems Biology, Stanford University, Stanford, California, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Ahrends
authors.affiliation: Division of Endocrinology, Gerontology and Metabolism, Stanford University, Stanford, California, United States of America; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Ye
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Division of Endocrinology, Gerontology and Metabolism, Stanford University, Stanford, California, United States of America; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Shen
authors.affiliation: Mass Spectrometry Center, Stanford University, Stanford, California, United States of America.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Adams
authors.affiliation: Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Ann Nomoto
authors.initials: AN
authors.lastname: Roseman
authors.affiliation: Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cortez
authors.affiliation: Department of Chemical and Systems Biology, Stanford University, Stanford, California, United States of America.
authors.forename: Mary N
authors.initials: MN
authors.lastname: Teruel
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Stanford University, Stanford, California, United States of America; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Salman
authors.initials: S
authors.lastname: Azhar
authors.affiliation: Division of Endocrinology, Gerontology and Metabolism, Stanford University, Stanford, California, United States of America; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States of America.
authors.forename: Fredric B
authors.initials: FB
authors.lastname: Kraemer
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism*; D004330:Drosophila; D005260:Female; D020869:Gene Expression Profiling; D006107:Granulosa Cells / Q000378:metabolism; D066292:Lipid Droplets / Q000378:metabolism*; D050356:Lipid Metabolism; D011506:Proteins / Q000032:analysis*; D020543:Proteome / Q000032:analysis* / Q000378:metabolism; D040901:Proteomics / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D002788:Cholesterol Esters; D011506:Proteins; D020543:Proteome; D014280:Triglycerides
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