Dynamic Activity of Lipid Droplets: Protein Phosphorylation and GTP-Mediated Protein Translocation

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• 作者：René ; Bartz ; John K. Zehmer ; Meifang Zhu ; Yue Chen ; Ginette Serrero ; Yingming Zhao ; Pingsheng Liu
• 刊名：Journal of Proteome Research
• 出版年：2007
• 出版时间：August 2007
• 年：2007
• 卷：6
• 期：8
• 页码：3256 - 3265
• 全文大小：256K
• 年卷期：v.6,no.8(August 2007)
• ISSN：1535-3907

文摘

Lipid droplet is a cellular organelle with a neutral lipid core surrounded by a phospholipid monolayerand coated with structural as well as functional proteins. The determination of these proteins, especiallytheir functional regulations and dynamic movement on and off droplets, holds a key to resolving thebiological functions of the cellular organelle. To address this, we carried out a comprehensive proteomicstudy that includes a complete proteomic, a phosphoprotein proteomic, and a comparative proteomicanalysis using purified lipid droplets and mass spectrometry techniques. The complete proteomeidentified 125 proteins of which 70 proteins had not been identified on droplets of mammalian cellspreviously. In phosphoprotein proteomic analysis, 7 functional lipid droplet proteins were determinedto be phosphorylated, including adipose differentiation related protein (ADRP/ADFP), two Rab proteins,and four lipid metabolism enzymes, including adipose triglyceride lipase (ATGL). To understand thedynamics of lipid droplets, GTP-dependent protein recruitment was analyzed by comparative proteomics.Arf1 and some of its coatomers, three other Arfs, several other small G-proteins including 3 Rabs, andseveral lipid synthetic enzymes were recruited from cytosol to purified droplets. Together, the presentstudy suggests that lipid droplet is an active and dynamic cellular organelle that governs lipidhomeostasis and intracellular trafficking through protein phosphorylation as well as GTP-regulatedprotein translocation.