Pol A, Luetterforst R, Lindsay M, Heino S, Ikonen E, Parton R G
Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis and Department of Physiology and Pharmacology, University of Queensland, Queensland 4072, Australia.
J Cell Biol. 2001 Mar 5;152(5):1057-70. doi: 10.1083/jcb.152.5.1057.
Recent studies have indicated a role for caveolin in regulating cholesterol-dependent signaling events. In the present study we have analyzed the role of caveolins in intracellular cholesterol cycling using a dominant negative caveolin mutant. The mutant caveolin protein, cav-3(DGV), specifically associates with the membrane surrounding large lipid droplets. These structures contain neutral lipids, and are accessed by caveolin 1-3 upon overexpression. Fluorescence, electron, and video microscopy observations are consistent with formation of the membrane-enclosed lipid rich structures by maturation of subdomains of the ER. The caveolin mutant causes the intracellular accumulation of free cholesterol (FC) in late endosomes, a decrease in surface cholesterol and a decrease in cholesterol efflux and synthesis. The amphiphile U18666A acts synergistically with cav(DGV) to increase intracellular accumulation of FC. Incubation of cells with oleic acid induces a significant accumulation of full-length caveolins in the enlarged lipid droplets. We conclude that caveolin can associate with the membrane surrounding lipid droplets and is a key component involved in intracellular cholesterol balance and lipid transport in fibroblasts.
最近的研究表明小窝蛋白在调节胆固醇依赖性信号事件中发挥作用。在本研究中，我们使用显性负性小窝蛋白突变体分析了小窝蛋白在细胞内胆固醇循环中的作用。突变型小窝蛋白cav-3(DGV)特异性地与围绕大脂滴的膜结合。这些结构含有中性脂质，过表达时小窝蛋白1-3可进入其中。荧光、电子和视频显微镜观察结果与内质网亚结构域成熟形成膜包被的富含脂质结构一致。小窝蛋白突变体导致晚期内体中游离胆固醇(FC)在细胞内积累，表面胆固醇减少，胆固醇流出和合成减少。两亲性化合物U18666A与cav(DGV)协同作用，增加细胞内FC的积累。用油酸孵育细胞会导致全长小窝蛋白在增大的脂滴中显著积累。我们得出结论，小窝蛋白可与脂滴周围的膜结合，是成纤维细胞内胆固醇平衡和脂质转运的关键成分。
