Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, 686 Bay Street, 19-9800, Toronto, ON, M5G 0A4, Canada.
Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, 686 Bay Street, 19-9800, Toronto, ON, M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Canada.
Curr Opin Cell Biol. 2021 Aug;71:77-86. doi: 10.1016/j.ceb.2021.02.006. Epub 2021 Mar 8.
Endocytic traffic is a complex and elegant operation involving cargo sorting, membrane budding and tubulation, generation of force, and the formation of organellar contacts. The role of specific proteins and lipids in these processes has been studied extensively. By comparison, precious little is understood about the contribution of the endocytic fluid to these events, despite much evidence that alteration of the contents can severely affect membrane traffic along the endocytic pathway. In particular, it has long been appreciated that dissipation of ionic gradients arrests endosome-to-lysosome maturation. How cells sense inorganic ions and transmit this information have remained largely enigmatic. Herein, we review the experimental findings that reveal an intimate association between luminal ions, their transport, and endocytic traffic. We then discuss the ionic sensors and the mechanisms proposed to convert ion concentrations into protein-based trafficking events, highlighting the current paucity of convincing explanations.
内吞运输是一个复杂而精巧的过程，涉及货物分拣、膜出芽和管状化、力的产生以及细胞器接触的形成。特定蛋白质和脂质在这些过程中的作用已经得到了广泛的研究。相比之下，尽管有大量证据表明内吞液内容物的改变会严重影响沿内吞途径的膜运输，但对于内吞液对这些事件的贡献却知之甚少。特别是，人们早就认识到，离子梯度的耗散会阻止内体向溶酶体的成熟。细胞如何感知无机离子以及如何传递这种信息，在很大程度上仍然是个谜。本文综述了揭示腔内腔离子及其运输与内吞运输之间密切关联的实验发现。然后，我们讨论了离子传感器和提出的将离子浓度转化为基于蛋白质的运输事件的机制，强调了目前缺乏令人信服的解释。
