Membrane contact sites, where two organelles are in close proximity, are critical regulators of cellular membrane homeostasis, with roles in signaling, lipid metabolism, and ion dynamics. A growing catalog of specialized lipid transfer proteins carry out lipid exchange at these sites. Currently characterized eukaryotic lipid transport proteins are shuttles that typically extract a single lipid from the membrane of the donor organelle, solubilize it during transport through the cytosol, and deposit it in the acceptor organelle membrane. Here, we highlight the recently identified chorein_N family of lipid transporters, including the Vps13 proteins and the autophagy protein Atg2. These are elongated proteins that, distinct from previously characterized transport proteins, bind tens of lipids at once. They feature an extended channel, most likely lined with hydrophobic residues. We discuss the possibility that they are not shuttles but instead are bridges between membranes, with lipids traversing the cytosol via the hydrophobic channel.

中文翻译：

---

细胞器间脂质转移：Vps13 和舞蹈素-N 基序蛋白的通道模型。

膜接触位点，其中两个细胞器非常接近，是细胞膜稳态的关键调节剂，在信号传导、脂质代谢和离子动力学中发挥作用。越来越多的专门脂质转移蛋白在这些位点进行脂质交换。目前表征的真核脂质转运蛋白是穿梭，通常从供体细胞器的膜中提取单个脂质，在通过细胞溶质的运输过程中溶解它，并将其沉积在受体细胞器膜中。在这里，我们重点介绍了最近发现的 chorein_N 脂质转运蛋白家族，包括 Vps13 蛋白和自噬蛋白 Atg2。这些是细长的蛋白质，与先前表征的转运蛋白不同，可同时结合数十种脂质。它们具有扩展通道，最有可能内衬疏水残基。我们讨论了它们不是穿梭机而是膜之间的桥梁的可能性，脂质通过疏水通道穿过细胞质。