Interaction between the RGS domain of RGS4 with G protein α subunits mediates the voltage-dependent relaxation of the G protein-gated potassium channel
Interaction between the RGS domain of RGS4 with G protein α subunits mediates the voltage-dependent relaxation of the G protein-gated potassium channel
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DOI：
10.1111/j.1469-7793.2001.t01-1-00133.x
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发表时间：
2001-08-15
影响因子：
5.5
通讯作者：
Kurachi, Y
中科院分区：
文献类型：
--
作者：
Inanobe, A;Fujita, S;Kurachi, Y
1.在天然心肌细胞中，G蛋白门控内向整流K+（K-G）通道电流在电压阶跃期间具有时间依赖性，随着乙酰胆碱浓度的增加而加速。这种现象被称为“松弛”，并且在非洲爪蟾卵母细胞中的重建的Kir3.1/Kir3.4通道中不再现。我们已经表明，RGS 4，G蛋白信号的调节，恢复松弛重建Kir3.1/Kir3.4通道。在本研究中，我们通过在非洲爪蟾卵母细胞中表达膜受体、G蛋白、Kir3.0亚基和RGS 4突变体的各种组合来研究这种现象的机制. RGS 4恢复了对百日咳毒素（PTX）敏感的G蛋白偶联m（2）-毒蕈碱受体激活的K-G通道的舒张，但不恢复对G（s）蛋白偶联β（2）-肾上腺素能受体激活的K-G通道的舒张. RGS 4不仅在由Kir3.1和Kir3.4组成的异聚体K-G通道中诱导松弛，而且在Kir3.1的活性突变体（Kir3.1/F137 S）或Kir3.2的同种型（Kir3.2d）的同源组装体中也诱导松弛。RGS 4的截短突变体表明RGS结构域本身对于再现野生型RGS 4对K-G通道的作用是必不可少的.与G蛋白的α亚基相互作用的RGS结构域中的残基的突变损害了RGS4.6的作用。因此，这项研究表明，RGS结构域和PTX敏感性G（α）亚基之间的相互作用介导了RGS 4对K-G通道激动剂浓度依赖性舒张的作用。
1. In native cardiac myocytes, there is a time dependence to the G protein-gated inwardly rectifying K+ (K-G) channel current during voltage steps that accelerates as the concentration of acetylcholine is increased. This Phenomenon has been called 'relaxation' and is not reproduced in the reconstituted Kir3.1/Kir3.4 channel in Xenopus oocytes. We have shown that RGS4, a regulator of G protein signalling, restores relaxation to the reconstituted Kir3.1/Kir3.4 channel. In this study, we examined the mechanism of this phenomenon by expressing various combinations of membrane receptors, G proteins, Kir3.0 subunits and mutants of RGS4 in Xenopus oocytes.2. RGS4 restored relaxation to K-G channels activated by the pertussis toxin (PTX)-sensitive G protein-coupled m(2)-muscarinic receptor but not to those activated by the G(s) protein-coupled beta (2)-adrenergic receptor.3. RGS4 induced relaxation not only in heteromeric K-G channels composed of Kir3.1 and Kir3.4 but also in homomeric assemblies of either an active mutant of Kir3.1 (Kir3.1/F137S) or an isoform of Kir3.2 (Kir3.2d).4. Truncation mutants of RGS4 showed that the RGS domain itself was essential to reproduce the effect of wild-type RGS4 on the K-G channel.5. The mutation of residues in the RGS domain which interact with the alpha subunit of the G protein impaired the effect of RGS4.6. This study therefore shows that interaction between the RGS domain and PTX-sensitive G(alpha) subunits mediates the effect of RGS4 on the agonist concentration-dependent relaxation of K-G channels.