Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
Cell Calcium. 2017 Dec;68:1-4. doi: 10.1016/j.ceca.2017.09.003. Epub 2017 Sep 29.
Two-pore channels (TPCs) are two-domain members of the voltage-gated ion channel superfamily that localize to acidic organelles. Their mechanism of activation (ligands such as NAADP/PI(3,5)P versus voltage) and ion selectivity (Ca versus Na) is debated. Here we report that a cluster of arginine residues in the first domain required for selective voltage-gating of TPC1 map not to the voltage-sensing fourth transmembrane region (S4) but to a cytosolic downstream region (S4-S5 linker). These residues are conserved between TPC isoforms suggesting a generic role in TPC activation. Accordingly, mutation of residues in TPC1 but not the analogous region in the second domain prevents Ca release by NAADP in intact cells. Our data affirm the role of TPCs in NAADP-mediated Ca signalling and unite differing models of channel activation through identification of common domain-specific residues.
双孔通道（TPCs）是电压门控离子通道超家族的两域成员，定位于酸性细胞器。它们的激活机制（配体如 NAADP/PI(3,5)P 与电压相比）和离子选择性（Ca 与 Na）存在争议。在这里，我们报告说，第一结构域中一组精氨酸残基对于 TPC1 的选择性电压门控不是必需的，而是对于第四跨膜区域（S4）的细胞质下游区域（S4-S5 接头）。这些残基在 TPC 同工型之间是保守的，这表明它们在 TPC 激活中具有通用作用。因此，TPC1 中残基的突变而不是第二结构域中类似区域的突变会阻止 NAADP 在完整细胞中释放 Ca。我们的数据证实了 TPCs 在 NAADP 介导的 Ca 信号中的作用，并通过鉴定共同的特定于结构域的残基将不同的通道激活模型统一起来。
