Structural Insights into AQP2 Targeting to Multivesicular Bodies
Structural Insights into AQP2 Targeting to Multivesicular Bodies
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DOI：
10.3390/ijms20215351
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发表时间：
2019-11-01
影响因子：
5.6
通讯作者：
Tornroth-Horsefield, Susanna
中科院分区：
文献类型：
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作者：
Roche, Jennifer Virginia;Nesverova, Veronika;Tornroth-Horsefield, Susanna
血管加压素依赖的AQP2在肾脏集合管中的运输对于水稳态的调节是至关重要的。这一过程包括在脱水过程中将AQP2靶向到顶膜，以及在水合水平恢复后将其移除。后者包括AQP2内吞作用和分选成多泡小体(MVB)，在那里它可以被回收，在溶酶体中降解，或通过外切体释放到尿液中。溶酶体转运调节因子相互作用蛋白5(LIP5)通过协调转运所需的内体分选复合体(ESCRT-III)和空泡蛋白分选4(Vps4)ATPase的作用，导致AQP2插入MVB内囊中，从而在这一过程中发挥关键作用。虽然LIP5与ESCRT-III复合体和Vps4之间的相互作用已被很好地描述，但对LIP5如何与AQP2或任何其他膜蛋白货物相互作用知之甚少。在这里，我们使用荧光光谱和计算机建模的组合来提供LIP5如何与人AQP2相互作用的结构模型。我们证明，AQP2四聚体与两个LIP5分子结合，并且这种相互作用类似于LIP5与ESCRT-III组分带电多囊体蛋白1B(CHMP1B)之间的作用。这些研究为LIP5如何使膜蛋白插入MVB内囊泡提供了第一个结构性的见解，并显著增加了我们对AQP2运输机制的理解。
Vasopressin-dependent trafficking of AQP2 in the renal collecting duct is crucial for the regulation of water homeostasis. This process involves the targeting of AQP2 to the apical membrane during dehydration as well as its removal when hydration levels have been restored. The latter involves AQP2 endocytosis and sorting into multivesicular bodies (MVB), from where it may be recycled, degraded in lysosomes, or released into urine via exosomes. The lysosomal trafficking regulator-interacting protein 5 (LIP5) plays a crucial role in this by coordinating the actions of the endosomal sorting complex required for transport III (ESCRT-III) and vacuolar protein sorting 4 (Vps4) ATPase, resulting in the insertion of AQP2 into MVB inner vesicles. While the interaction between LIP5 and the ESCRT-III complex and Vps4 is well characterized, very little is known about how LIP5 interacts with AQP2 or any other membrane protein cargo. Here, we use a combination of fluorescence spectroscopy and computer modeling to provide a structural model of how LIP5 interacts with human AQP2. We demonstrate that, the AQP2 tetramer binds up to two LIP5 molecules and that the interaction is similar to that seen in the complex between LIP5 and the ESCRT-III component, charged multivesicular body protein 1B (CHMP1B). These studies give the very first structural insights into how LIP5 enables membrane protein insertion into MVB inner vesicles and significantly increase our understanding of the AQP2 trafficking mechanism.