Osmoregulatory inositol transporter SMIT1 modulates electrical activity by adjusting PI(4,5)P2 levels
Osmoregulatory inositol transporter SMIT1 modulates electrical activity by adjusting PI(4,5)P2 levels
复制标题
DOI：
10.1073/pnas.1606348113
复制
发表时间：
2016-06-07
影响因子：
11.1
通讯作者：
Hille, Bertil
中科院分区：
文献类型：
--
作者：
Dai, Gucan;Yu, Haijie;Hille, Bertil
肌醇是一种重要的细胞渗透剂，在细胞体积和液体平衡的自动调节中，特别是对于哺乳动物的脑和肾细胞。我们发现它也调节兴奋性。肌醇是磷酸肌醇的前体，磷酸肌醇是关键信号脂质，包括磷脂酰肌醇4，5-二磷酸[PI（4，5）P-2]。然而，肌醇积累过程中是否肌醇调节影响信号和兴奋性尚未得到充分探讨。我们发现过表达的Na+/肌醇协同转运蛋白（SMIT 1）和肌醇补充扩大细胞内PI（4，5）P-2池，调制几个PI（4，5）P-2依赖的离子通道，包括KCNQ 2/3通道，并减弱动作电位放电的上级颈神经节神经元。使用雷帕霉素可募集磷酸酶Sac 1水解PI（4）P和P4 M探针可视化PI（4）P的进一步实验表明，在补充肌醇并表达SMIT 1后，PI（4）P水平增加。使用质谱法直接证实PIP和PIP 2的相对水平升高。补充肌醇后，三磷酸肌醇的产生和细胞内钙的释放也增加。最后，我们发现，高渗溶液的治疗模拟了我们观察到的SMIT 1过表达的效果，而沉默张力响应增强子结合蛋白阻止了这些效果。这些结果表明，离子通道功能和细胞兴奋性的调节下，由几个“生理”的操纵，改变PI（4，5）P-2的设定点。我们证明了一个以前未被认识到的联系细胞外渗透压变化和兴奋细胞的电特性。
Myo-inositol is an important cellular osmolyte in autoregulation of cell volume and fluid balance, particularly for mammalian brain and kidney cells. We find it also regulates excitability. Myo-inositol is the precursor of phosphoinositides, key signaling lipids including phosphatidylinositol 4,5-bisphosphate [PI(4,5)P-2]. However, whether myo-inositol accumulation during osmoregulation affects signaling and excitability has not been fully explored. We found that overexpression of the Na+/myo-inositol cotransporter (SMIT1) and myoinositol supplementation enlarged intracellular PI(4,5)P-2 pools, modulated several PI(4,5)P-2-dependent ion channels including KCNQ2/3 channels, and attenuated the action potential firing of superior cervical ganglion neurons. Further experiments using the rapamycin-recruitable phosphatase Sac1 to hydrolyze PI(4)P and the P4M probe to visualize PI(4) P suggested that PI(4) P levels increased after myoinositol supplementation with SMIT1 expression. Elevated relative levels of PIP and PIP2 were directly confirmed using mass spectrometry. Inositol trisphosphate production and release of calcium from intracellular stores also were augmented after myo-inositol supplementation. Finally, we found that treatment with a hypertonic solution mimicked the effect we observed with SMIT1 overexpression, whereas silencing tonicity-responsive enhancer binding protein prevented these effects. These results show that ion channel function and cellular excitability are under regulation by several "physiological" manipulations that alter the PI(4,5)P-2 setpoint. We demonstrate a previously unrecognized linkage between extracellular osmotic changes and the electrical properties of excitable cells.