Cruzblanca H, Koh D S, Hille B
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):7151-6. doi: 10.1073/pnas.95.12.7151.
A variety of intracellular signaling pathways can modulate the properties of voltage-gated ion channels. Some of them are well characterized. However, the diffusible second messenger mediating suppression of M current via G protein-coupled receptors has not been identified. In superior cervical ganglion neurons, we find that the signaling pathways underlying M current inhibition by B2 bradykinin and M1 muscarinic receptors respond very differently to inhibitors. The bradykinin pathway was suppressed by the phospholipase C inhibitor U-73122, by blocking the IP3 receptor with pentosan polysulfate or heparin, and by buffering intracellular calcium, and it was occluded by allowing IP3 to diffuse into the cytoplasm via a patch pipette. By contrast, the muscarinic pathway was not disrupted by any of these treatments. The addition of bradykinin was accompanied by a [Ca2+]i rise with a similar onset and time to peak as the inhibition of M current. The M current inhibition and the rise of [Ca2+]i were blocked by depletion of Ca2+ internal stores by thapsigargin. We conclude that bradykinin receptors inhibit M current of sympathetic neurons by activating phospholipase C and releasing Ca2+ from IP3-sensitive Ca2+ stores, whereas muscarinic receptors do not use the phospholipase C pathway to inhibit M current channels.
多种细胞内信号通路可调节电压门控离子通道的特性。其中一些已得到充分表征。然而，介导通过G蛋白偶联受体抑制M电流的可扩散第二信使尚未确定。在颈上神经节神经元中，我们发现B2缓激肽和M1毒蕈碱受体抑制M电流的信号通路对抑制剂的反应非常不同。缓激肽通路被磷脂酶C抑制剂U-73122抑制，被戊聚糖多硫酸盐或肝素阻断IP3受体，以及通过缓冲细胞内钙来抑制，并且通过允许IP3通过膜片吸管扩散到细胞质中而被阻断。相比之下，毒蕈碱通路不受这些处理的任何一种干扰。缓激肽的添加伴随着细胞内钙浓度升高，其起始和达到峰值的时间与M电流的抑制相似。毒胡萝卜素耗尽细胞内钙储存后，M电流抑制和细胞内钙浓度升高被阻断。我们得出结论，缓激肽受体通过激活磷脂酶C并从IP3敏感的钙储存中释放钙来抑制交感神经元的M电流，而毒蕈碱受体不使用磷脂酶C通路来抑制M电流通道。
