Schrecker Marina, Son Yeeun, Planells-Cases Rosa, Kar Sumanta, Vorobeva Viktoriia, Schulte Uwe, Fakler Bernd, Jentsch Thomas J, Hite Richard K
Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
BCMB Allied Program, Weill Cornell Graduate School, New York, NY, USA.
Nat Struct Mol Biol. 2025 Jul 16. doi: 10.1038/s41594-025-01617-2.
The trafficking and activity of endosomes relies on the exchange of chloride ions and protons by members of the CLC family of chloride channels and transporters; mutations of the genes encoding these transporters are associated with numerous diseases. Despite their critical roles, the mechanisms by which CLC transporters are regulated are poorly understood. Here we show that two related accessory β-subunits, TMEM9 and TMEM9B, directly interact with ClC-3, ClC-4 and ClC-5. Cryo-electron microscopy structures reveal that TMEM9 inhibits ClC-3 by sealing the cytosolic entrance to the Cl ion pathway. Unexpectedly, we find that phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P) stabilizes the interaction between TMEM9 and ClC-3 and is required for proper regulation of ClC-3 by TMEM9. Collectively, our findings reveal that TMEM9 and PtdIns(3,5)P collaborate to regulate endosomal ion homeostasis by modulating the activity of ClC-3.
内体的运输和活性依赖于氯离子通道和转运蛋白的CLC家族成员对氯离子和质子的交换；编码这些转运蛋白的基因突变与多种疾病相关。尽管它们起着关键作用，但人们对CLC转运蛋白的调节机制却知之甚少。在这里，我们表明两个相关的辅助β亚基TMEM9和TMEM9B直接与ClC-3、ClC-4和ClC-5相互作用。冷冻电子显微镜结构显示，TMEM9通过封闭氯离子通道的胞质入口来抑制ClC-3。出乎意料的是，我们发现磷脂酰肌醇3,5-二磷酸（PtdIns(3,5)P）稳定了TMEM9与ClC-3之间的相互作用，并且是TMEM9对ClC-3进行适当调节所必需的。总的来说，我们的研究结果表明，TMEM9和PtdIns(3,5)P通过调节ClC-3的活性协同调节内体离子稳态。
