Synergism of inositol trisphosphate and tetrakisphosphate in activating Ca2+-dependent K+ channels
Synergism of inositol trisphosphate and tetrakisphosphate in activating Ca2+-dependent K+ channels
复制标题
肌醇三磷酸和四磷酸在激活 Ca2 依赖性 K 通道中的协同作用
作者：
Andrew P. Morris;D. Gallacher;R. Irvine;Ole H. Petersen
肌醇1,4,5-三磷酸（inp3）是释放细胞内Ca2+到细胞质- 5的第二信使。最近有研究提出，由Ins P3-3-激酶形成的肌醇1,3,4,5-四磷酸（Ins P4）通过促进细胞外Ca2+进入与Ins P3一起作为第二信使起作用7。有研究表明，尽管不排除Ins P4的生理功能，但Ins P3本身可以刺激细胞外液对Ca2+的摄取8,9。在细胞内灌注液可以在单个实验中多次改变的条件下，现在可以通过电压箝位在单个细胞中测量跨膜电流10,11。我们已经用这种方法测试了inp3和inp4对Ca2+激活的K+电流的影响12,13，现在表明，无论是单独的inp3还是单独的inp4都不能激活持续电流，而inp3和inp4联合使用可以引起依赖于外部Ca2+的Ca2+激活的K+电流的持续增加。
Inositol 1,4,5-trisphosphate (Ins P3) is a second messenger releasing intracellular Ca2+ into the cytosol–5. It has recently been proposed that inositol 1,3,4,5-tetrakisphosphate (Ins P4), which is formed from Ins P3 by Ins P3-3-kinase (ref. 6), acts with Ins P3 as a second messenger by promoting extracellular Ca2+ entry7. It has been suggested that Ins P3 itself can act to stimulate Ca2+ uptake from the extracellular fluid, although a physiological function for Ins P4 was not excluded8,9. Transmembrane currents can now be measured in single cells by voltage clamping under conditions where the intracellular perfusion fluid can be changed several times during individual experiments10,11. We have used this method to test the effects of Ins P3 and Ins P4 on the Ca2+-activated K+ current12,13, and now show that neither Ins P3 alone nor Ins P4 alone can activate a sustained current, whereas Ins P3 and Ins P4 in combination evoke a sustained increase in Ca2+-activated K+ current which is dependent on external Ca2+.