Intracellular organelles change their size during trafficking and maturation. This requires the transport of ions and water across their membranes. Macropinocytosis, a ubiquitous form of endocytosis of particular importance for immune and cancer cells, generates large vacuoles that can be followed optically. Shrinkage of macrophage macropinosomes depends on TPC-mediated Na⁺ efflux and Cl⁻ exit through unknown channels. Relieving osmotic pressure facilitates vesicle budding, positioning osmotic shrinkage upstream of vesicular sorting and trafficking. Here we identify the missing macrophage Cl⁻ channel as the proton-activated Cl⁻ channel ASOR/TMEM206. ASOR activation requires Na⁺-mediated depolarization and luminal acidification by redundant transporters including H⁺-ATPases and CLC 2Cl⁻/H⁺ exchangers. As corroborated by mathematical modelling, feedback loops requiring the steep voltage and pH dependencies of ASOR and CLCs render vacuole resolution resilient towards transporter copy numbers. TMEM206 disruption increased albumin-dependent survival of cancer cells. Our work suggests a function for the voltage and pH dependence of ASOR and CLCs, provides a comprehensive model for ion-transport-dependent vacuole maturation and reveals biological roles of ASOR.

细胞内细胞器在运输和成熟过程中会改变其大小。这需要离子和水穿过它们的膜。巨胞饮作用是一种普遍存在的内吞作用形式，对免疫细胞和癌细胞特别重要，它会产生大的液泡，这些液泡可以进行光学追踪。巨噬细胞巨噬细胞体的收缩取决于 TPC 介导的 Na ⁺流出和 Cl ^-通过未知通道排出。降低渗透压有助于囊泡出芽，将渗透压收缩定位在囊泡分选和运输的上游。在这里，我们将缺失的巨噬细胞 Cl ^-通道识别为质子激活的 Cl ^-通道 ASOR/TMEM206。ASOR激活需要Na ⁺-通过冗余转运蛋白介导的去极化和管腔酸化，包括 H ⁺ -ATP 酶和 CLC 2Cl ^- /H ⁺交换剂。正如数学模型所证实的那样，需要 ASOR 和 CLC 的陡峭电压和 pH 依赖性的反馈回路使液泡分辨率对转运蛋白拷贝数具有弹性。TMEM206破坏增加了癌细胞的白蛋白依赖性存活。我们的工作提出了 ASOR 和 CLC 的电压和 pH 依赖性函数，为离子传输依赖性液泡成熟提供了一个综合模型，并揭示了 ASOR 的生物学作用。