Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel.
PLoS One. 2013 Sep 3;8(9):e74354. doi: 10.1371/journal.pone.0074354. eCollection 2013.
G-protein coupled receptors (GPCRs) comprise the largest protein family and mediate the vast majority of signal transduction processes in the body. Until recently GPCRs were not considered to be voltage dependent. Newly it was shown for several GPCRs that the first step in GPCR activation, the binding of agonist to the receptor, is voltage sensitive: Voltage shifts the receptor between two states that differ in their binding affinity. Here we show that this shift involves the rate constant of dissociation. We used the m2 muscarinic receptor (m2R) a prototypical GPCR and measured directly the dissociation of [(3)H]ACh from m2R expressed Xenopus oocytes. We show, for the first time, that the voltage dependent change in affinity is implemented by voltage shifting the receptor between two states that differ in their rate constant of dissociation. Furthermore, we provide evidence that suggest that the above shift is achieved by voltage regulating the coupling of the GPCR to its G protein.
G 蛋白偶联受体（GPCRs）是最大的蛋白质家族，介导体内绝大多数信号转导过程。直到最近，人们才发现 GPCRs 不依赖于电压。最近的研究表明，对于几种 GPCR 来说，GPCR 激活的第一步，即激动剂与受体的结合，是电压敏感的：电压将受体在两种结合亲和力不同的状态之间转换。在这里，我们表明这种转变涉及离解的速率常数。我们使用了 m2 毒蕈碱受体（m2R）作为典型的 GPCR，并直接测量了在表达非洲爪蟾卵母细胞的 m2R 上从 [(3)H]ACh 的解离。我们首次表明，亲和力的电压依赖性变化是通过将受体在两种解离速率常数不同的状态之间转换来实现的。此外，我们提供的证据表明，上述转变是通过电压调节 GPCR 与其 G 蛋白的偶联来实现的。
