Lipid droplets (LDs) are globular intracellular structures dedicated to the storage of neutral lipids. They are closely associated with the endoplasmic reticulum (ER) and are delineated by a monolayer of phospholipids that is continuous with the cytoplasmic leaflet of the ER membrane. LDs contain a specific set of proteins, but how these proteins are targeted to the LD surface is not fully understood. Here, we devised a yeast mating-based microscopic readout to monitor the transfer of LD proteins upon zygote formation. The results of this analysis indicate that ER fusion between mating partners is required for transfer of LD proteins and that this transfer is continuous, bidirectional and affects most LDs simultaneously. These observations suggest that LDs do not fuse upon mating of yeast cells, but that they form a network that is interconnected through the ER membrane. Consistent with this, ER-localized LD proteins rapidly move onto LDs of a mating partner and this protein transfer is affected by seipin, a protein important for proper LD biogenesis and the functional connection of LDs with the ER membrane.

中文翻译：

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脂滴形成一个由内质网相互连接的网络，它们的蛋白质通过该网络平衡。

脂滴 (LD) 是专门用于储存中性脂质的球状细胞内结构。它们与内质网 (ER) 密切相关，并由与 ER 膜的细胞质小叶连续的单层磷脂划定。LD 包含一组特定的蛋白质，但这些蛋白质如何靶向 LD 表面尚不完全清楚。在这里，我们设计了一种基于酵母交配的显微读数来监测 LD 蛋白在合子形成时的转移。该分析的结果表明，交配伙伴之间的 ER 融合是 LD 蛋白转移所必需的，并且这种转移是连续的、双向的，并且同时影响大多数 LD。这些观察结果表明 LD 在酵母细胞交配时不会融合，但它们形成了一个通过 ER 膜相互连接的网络。与此一致，ER 定位的 LD 蛋白迅速移动到交配伴侣的 LD 上，并且这种蛋白质转移受到 seipin 的影响，seipin 是一种对适当的 LD 生物发生和 LD 与 ER 膜的功能连接很重要的蛋白质。