Voltage Dependence of a Neuromodulator-Activated Ionic Current.
Voltage Dependence of a Neuromodulator-Activated Ionic Current.
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DOI：
10.1523/eneuro.0038-16.2016
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发表时间：
2016-03
期刊：
影响因子：
3.4
通讯作者：
Golowasch J
中科院分区：
文献类型：
--
作者：
Gray M;Golowasch J
北蟹口胃神经节神经元产生的神经调节内向电流（IMI）是一种向内电流，其电压依赖性在该系统幽门神经网络振荡活动的激活中起着至关重要的作用。先前已经表明，IMI在低细胞外钙条件下失去其电压依赖性，但这种影响似乎是由细胞内钙调蛋白调节的。电压依赖性很少受到细胞内信号机制的调节。在这里，我们提出了一个假设，即IMI的电压依赖性是由细胞外钙激活的细胞内信号通路介导的。我们证明钙调素抑制剂和ryanodine拮抗剂可以降低正常Ca2+条件下IMI电压依赖性，但是，在低Ca2+条件下，钙调素激活剂不能恢复IMI电压依赖性。此外，我们展示了CaMKII改变IMI电压依赖性的证据。这些结果表明钙调素对IMI电压依赖性是必要的，但不是充分的。因此，我们假设Ca2+/钙调素对IMI电压依赖性的需求是由于GPCR家族钙敏感受体（CaSR）对细胞外钙的主动感知，而钙调素抑制剂对IMI电压依赖性的降低是由于CaSR内噬作用。支持这一点的是，预孵育内吞抑制剂可防止W7 （N-（6-氨基己基）-5-氯-1-萘磺酰胺盐酸盐）诱导的IMI电压依赖性丧失，CaSR拮抗剂可降低IMI电压依赖性。此外，已知位于CaSR下游的肌球蛋白轻链激酶似乎在调节IMI电压依赖性中发挥作用。最后，g βγ-亚基抑制剂也影响IMI电压依赖性，支持该过程由g蛋白偶联CaSR调节的假设。
The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca2+, but that, in conditions of low Ca2+, calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca2+/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR.