Mishra Shirish, Khaddaj Rasha, Cottier Stéphanie, Stradalova Vendula, Jacob Claire, Schneiter Roger
University of Fribourg, Department of Biology, Fribourg 1700, Switzerland.
University of Fribourg, Department of Biology, Fribourg 1700, Switzerland
J Cell Sci. 2016 Oct 15;129(20):3803-3815. doi: 10.1242/jcs.189191. Epub 2016 Sep 2.
Lipid droplets are found in most organisms where they serve to store energy in the form of neutral lipids. They are formed at the endoplasmic reticulum (ER) membrane where the neutral-lipid-synthesizing enzymes are located. Recent results indicate that lipid droplets remain functionally connected to the ER membrane in yeast and mammalian cells to allow the exchange of both lipids and integral membrane proteins between the two compartments. The precise nature of the interface between the ER membrane and lipid droplets, however, is still ill-defined. Here, we probe the topology of lipid droplet biogenesis by artificially targeting proteins that have high affinity for lipid droplets to inside the luminal compartment of the ER. Unexpectedly, these proteins still localize to lipid droplets in both yeast and mammalian cells, indicating that lipid droplets are accessible from within the ER lumen. These data are consistent with a model in which lipid droplets form a specialized domain in the ER membrane that is accessible from both the cytosolic and the ER luminal side.
脂滴存在于大多数生物体中，它们以中性脂质的形式储存能量。脂滴在内质网（ER）膜上形成，中性脂质合成酶位于该膜上。最近的研究结果表明，在酵母和哺乳动物细胞中，脂滴在功能上仍与内质网膜相连，以便在这两个区室之间交换脂质和整合膜蛋白。然而，内质网膜与脂滴之间界面的确切性质仍不明确。在这里，我们通过人工将对脂滴具有高亲和力的蛋白质靶向到内质网腔室内部，来探究脂滴生物发生的拓扑结构。出乎意料的是，这些蛋白质在酵母和哺乳动物细胞中仍定位于脂滴，这表明从内质网腔内可以接触到脂滴。这些数据与一个模型一致，即脂滴在内质网膜上形成一个特殊的区域，从胞质侧和内质网腔侧都可以接触到该区域。
