Department of Biochemistry & Molecular Biology, Oklahoma State University, Stillwater, OK 74074, USA.
Insect Biochem Mol Biol. 2012 May;42(5):305-20. doi: 10.1016/j.ibmb.2012.01.001. Epub 2012 Jan 5.
The lipid droplets (LDs) are intracellular organelles mainly dedicated to the storage and provision of fatty acids. To accomplish these functions the LDs interact with other organelles and cytosolic proteins. In order to explore possible correlations between the physiological states of cells and the protein composition of LDs we have determined and compared the proteomic profiles of lipid droplets isolated from the fat bodies of 5th-instar larvae and adult Manduca sexta insects and from ovaries. These LD-rich tissues represent three clearly distinct metabolic states in regard to lipid metabolism: 1) Larval fat body synthesizes fatty acids (FA) and accumulates large amounts as triglyceride (TG); 2) Fat body from adult insects provides FA to support reproduction and flight; 3) Ovaries do not synthesize FA, but accumulate considerable amounts of TG in LDs. Major qualitative and semi-quantitative variations in the protein compositions of the LDs isolated from these three tissues were observed by MS/MS and partially validated by immuno-blotting. The differences observed included changes in the abundance of lipid droplet specific proteins, cytosolic proteins, mitochondrial proteins and also proteins associated with the machinery of protein synthesis. These results suggest that changes in the interaction of LDs with other organelles and cytosolic proteins are tightly related to the physiological state of cells. Herein, we summarize and compare the protein compositions of three subtypes of LDs and also describe for the first time the proteomic profile of LDs from an insect ovary. The compositions and compositional differences found among the LDs are discussed to provide a platform for future studies on the role of LDs, and their associated proteins, in cellular metabolism.
脂滴（LDs）是主要致力于储存和提供脂肪酸的细胞内细胞器。为了完成这些功能，LDs 与其他细胞器和胞质蛋白相互作用。为了探索细胞的生理状态和 LDs 蛋白质组成之间可能存在的相关性，我们已经确定并比较了来自 5 龄幼虫和成年曼陀罗昆虫的脂肪体以及卵巢的分离的 LDs 的蛋白质组学图谱。这些富含 LD 的组织在脂质代谢方面代表了三种截然不同的代谢状态：1）幼虫脂肪体合成脂肪酸（FA）并积累大量甘油三酯（TG）；2）来自成年昆虫的脂肪体提供 FA 以支持繁殖和飞行；3）卵巢不合成 FA，但在 LD 中积累相当数量的 TG。通过 MS/MS 和部分免疫印迹验证观察到从这三种组织分离的 LDs 的蛋白质组成的主要定性和半定量变化。观察到的差异包括 LD 特异性蛋白质、胞质蛋白、线粒体蛋白以及与蛋白质合成机制相关的蛋白质的丰度变化。这些结果表明，LDs 与其他细胞器和胞质蛋白相互作用的变化与细胞的生理状态密切相关。在此，我们总结并比较了三种 LDs 亚型的蛋白质组成，并首次描述了昆虫卵巢的 LD 蛋白质组学图谱。讨论了在 LDs 之间发现的组成和组成差异，为研究 LDs 及其相关蛋白质在细胞代谢中的作用提供了一个平台。
