Cell Screening Laboratory, UCD School of Biology & Environmental Science, University College Dublin, Dublin, Ireland.
Small GTPases. 2023 Dec;14(1):26-44. doi: 10.1080/21541248.2023.2238330.
Next year marks one-quarter of a century since the discovery of the so-called COPI-independent pathway, which operates between the Golgi apparatus and the endoplasmic reticulum (ER) in eukaryotic cells. Unlike almost all other intracellular trafficking pathways, this pathway is not regulated by the physical accumulation of multisubunit proteinaceous coat molecules, but instead by the small GTPase Rab6. What also sets it apart from other pathways is that the transport carriers themselves often take the form of tubules, rather than conventional vesicles. In this review, we assess the relevant literature that has accumulated to date, in an attempt to provide a concerted description of how this pathway is regulated. We discuss the possible cargo molecules that are carried in this pathway, and the likely mechanism of Rab6 tubule biogenesis, including how the cargo itself may play a critical role. We also provide perspective surrounding the various molecular motors of the kinesin, myosin and dynein families that have been implicated in driving Rab6-coated tubular membranes long distances through the cell prior to delivering their cargo to the ER. Finally, we also raise several important questions that require resolution, if we are to ultimately provide a comprehensive molecular description of how the COPI-independent pathway is controlled.
明年将是发现所谓的 COPI 非依赖性途径的四分之一世纪,该途径在真核细胞的高尔基体和内质网(ER)之间运作。与几乎所有其他细胞内运输途径不同,该途径不受多亚基蛋白衣壳分子的物理积累调节,而是由小 GTPase Rab6 调节。使它与其他途径区别开来的还有,运输载体本身通常采取小管的形式,而不是常规的囊泡。在这篇综述中,我们评估了迄今为止积累的相关文献,试图提供对该途径如何被调节的一致描述。我们讨论了可能在该途径中携带的货物分子,以及 Rab6 小管发生的可能机制,包括货物本身如何发挥关键作用。我们还围绕驱动 Rab6 包被的管状膜通过细胞远距离运输的驱动蛋白、肌球蛋白和动力蛋白家族的各种分子马达提供了视角,然后将其货物递送到 ER。最后,如果我们要最终提供对 COPI 非依赖性途径如何被控制的全面分子描述,我们还提出了几个需要解决的重要问题。