Kühn Frank J P, Kühn Cornelia, Lückhoff Andreas
Institute of Physiology, Medical Faculty, RWTH Aachen, D52057 Aachen, Germany.
Sci Rep. 2015 Jan 26;5:8032. doi: 10.1038/srep08032.
The human non-selective cation channel TRPM2 represents a mediator of apoptosis triggered by oxidative stress. The principal agonist ADP-ribose binds to the cytosolic domain of TRPM2, which is homologous to the human ADP-ribose pyrophosphatase NUDT9. To further elucidate the structure-function relationship of this channel, we characterised a TRPM2 orthologue from the cnidarian Nematostella vectensis, after its expression in a human cell line. This far distant relative shows only 31% total sequence similarity to hTRPM2, while its C-terminal domain has a greater resemblance to the NUDT9 enzyme. Current through nvTRPM2 was induced by ADPR, with a more pronounced sensitivity and faster kinetics than in hTRPM2. In contrast to hTRPM2, there was no response to H2O2 and hardly any modulatory effect by intracellular Ca(2+). The deletion of a stretch of 15 residues from the NUDT9 domain of nvTRPM2, which is absent in hTRPM2, did not change the response to ADPR but enabled activation of the channel by H2O2 and increased the effects of intracellular Ca(2+). These findings shed new light on the evolution of TRPM2 and establish nvTRPM2 as a promising tool to decipher its complex gating mechanisms.
人类非选择性阳离子通道TRPM2是氧化应激引发的细胞凋亡的介质。主要激动剂ADP-核糖与TRPM2的胞质结构域结合，该结构域与人类ADP-核糖焦磷酸酶NUDT9同源。为了进一步阐明该通道的结构-功能关系，我们在人细胞系中表达了来自刺胞动物星状海葵的TRPM2直系同源物并对其进行了表征。这个远缘亲属与hTRPM2的总序列相似性仅为31%，而其C端结构域与NUDT9酶更为相似。通过nvTRPM2的电流由ADPR诱导，其敏感性比hTRPM2更明显，动力学更快。与hTRPM2不同，nvTRPM2对H2O2无反应，细胞内Ca(2+)几乎没有调节作用。在nvTRPM2的NUDT9结构域中缺失一段15个残基（hTRPM2中不存在），并没有改变对ADPR的反应，但使通道能够被H2O2激活，并增强了细胞内Ca(2+)的作用。这些发现为TRPM2的进化提供了新的线索，并将nvTRPM2确立为破译其复杂门控机制的有前途的工具。
