Modulation of Gq-protein-coupled inositol trisphosphate and Ca2+ signaling by the membrane potential.
Modulation of Gq-protein-coupled inositol trisphosphate and Ca2+ signaling by the membrane potential.
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DOI：
10.1523/jneurosci.2773-06.2006
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发表时间：
2006-09-27
期刊：
影响因子：
--
通讯作者：
Nahorski SR
中科院分区：
文献类型：
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作者：
Billups D;Billups B;Challiss RA;Nahorski SR
Gq蛋白偶联受体(GqPCRs)广泛分布于中枢神经系统，在多种神经元突起中发挥重要作用。它们的激活导致PIP2水解，并通过PLC-IP3信号通路从细胞内存储中释放钙离子。由于早期的GqPCR信号发生在神经元的质膜上，它们可能会受到膜电位变化的影响。在这项研究中，我们使用膜片钳和成像相结合的方法来研究膜电位的变化是否可以调节神经元中的GqPCR信号。我们的结果表明，人神经细胞系SH-SY5Y和大鼠小脑颗粒神经元中的GqPCR信号对膜电位的变化直接敏感，即使在没有细胞外钙的情况下也是如此。去极化对GqPCR信号转导有双向作用，可增强Thapsigargin敏感的Ca~(2+)对M受体激活的反应，但减弱由缓激肽受体介导的反应。M胆碱信号的去极化增强是分级的、双极的、非失活的，没有明显的上限，排除了传统的电压门控离子通道作为主要电压传感器的可能性。笼式IP3/GPIP2的闪光光解将电压传感器置于钙离子存储的水平之前，并且使用荧光生物探针eGFP-phplcδ的测量直接证明了电压在IP3产生途径的水平上影响毒扁豆碱信号。神经元中GqPCRIP3信号对电压本身的敏感性可能代表了一种基本机制，通过这种机制，离子性信号可以塑造神经元中的代谢性受体活性，并影响突触可塑性等过程，其中一致信号的检测是至关重要的。
Gq protein-coupled receptors (GqPCRs) are widely distributed in the CNS and play fundamental roles in a variety of neuronal processes. Their activation results in PIP2 hydrolysis and Ca2+ release from intracellular stores via the PLC-IP3 signaling pathway. Since early GqPCR signaling events occur at the plasma membrane of neurons, they might be influenced by changes in membrane potential. In this study we use combined patch-clamp and imaging methods to investigate whether membrane potential changes can modulate GqPCR signaling in neurons. Our results demonstrate that GqPCR signaling in the human neuronal cell line SH-SY5Y and in rat cerebellar granule neurons is directly sensitive to changes in membrane potential, even in the absence of extracellular Ca2+. Depolarization has a bi-directional effect on GqPCR signaling, potentiating thapsigargin-sensitive Ca2+ responses to muscarinic receptor activation but attenuating those mediated by bradykinin receptors. The depolarization-evoked potentiation of the muscarinic signaling is graded, bipolar, non-inactivating and with no apparent upper limit, ruling out traditional voltage-gated ion channels as the primary voltage sensors. Flash photolysis of caged IP3/GPIP2 places the voltage-sensor before the level of the Ca2+ store and measurements using the fluorescent bioprobe eGFP-PHPLCδ directly demonstrate that voltage affects muscarinic signaling at the level of the IP3 production pathway. The sensitivity of GqPCR IP3 signaling in neurons to voltage itself may represent a fundamental mechanism by which ionotropic signals can shape metabotropic receptor activity in neurons and influence processes such as synaptic plasticity in which the detection of coincident signals is crucial.