Murakami Manabu, Ohba Takayoshi, Xu Feng, Satoh Eisaku, Miyoshi Ichiro, Suzuki Takashi, Takahashi Yoichirou, Takahashi Eiki, Watanabe Hiroyuki, Ono Kyoichi, Sasano Hironobu, Kasai Noriyuki, Ito Hiroshi, Iijima Toshihiko
Department of Pharmacology, Akita University School of Medicine, Akita 010-8543, Japan.
J Biol Chem. 2008 Sep 5;283(36):24554-60. doi: 10.1074/jbc.M802319200. Epub 2008 Jul 15.
N-type voltage-dependent calcium channels (VDCCs) play determining roles in calcium entry at sympathetic nerve terminals and trigger the release of the neurotransmitter norepinephrine. The accessory beta3 subunit of these channels preferentially forms N-type channels with a pore-forming CaV2.2 subunit. To examine its role in sympathetic nerve regulation, we established a beta3-overexpressing transgenic (beta3-Tg) mouse line. In these mice, we analyzed cardiovascular functions such as electrocardiography, blood pressure, echocardiography, and isovolumic contraction of the left ventricle with a Langendorff apparatus. Furthermore, we compared the cardiac function with that of beta3-null and CaV2.2 (alpha1B)-null mice. The beta3-Tg mice showed increased expression of the beta3 subunit, resulting in increased amounts of CaV2.2 in supracervical ganglion (SCG) neurons. The beta3-Tg mice had increased heart rate and enhanced sensitivity to N-type channel-specific blockers in electrocardiography, blood pressure, and echocardiography. In contrast, cardiac atria of the beta3-Tg mice revealed normal contractility to isoproterenol. Furthermore, their cardiac myocytes showed normal calcium channel currents, indicating unchanged calcium influx through VDCCs. Langendorff heart perfusion analysis revealed enhanced sensitivity to electric field stimulation in the beta3-Tg mice, whereas beta3-null and Cav2.2-null showed decreased responsiveness. The plasma epinephrine and norepinephrine levels in the beta3-Tg mice were significantly increased in the basal state, indicating enhanced sympathetic tone. Electrophysiological analysis in SCG neurons of beta3-Tg mice revealed increased calcium channel currents, especially N- and L-type currents. These results identify a determining role for the beta3 subunit in the N-type channel population in SCG and a major role in sympathetic nerve regulation.
N型电压依赖性钙通道（VDCCs）在交感神经末梢的钙内流中起决定性作用，并触发神经递质去甲肾上腺素的释放。这些通道的辅助β3亚基优先与形成孔道的CaV2.2亚基形成N型通道。为了研究其在交感神经调节中的作用，我们建立了一个过表达β3的转基因（β3-Tg）小鼠品系。在这些小鼠中，我们分析了心血管功能，如心电图、血压、超声心动图以及使用Langendorff装置对左心室等容收缩的分析。此外，我们将其心脏功能与β3基因敲除小鼠和CaV2.2（α1B）基因敲除小鼠的心脏功能进行了比较。β3-Tg小鼠显示β3亚基表达增加，导致颈上神经节（SCG）神经元中CaV2.2的量增加。β3-Tg小鼠心率增加，在心电图、血压和超声心动图方面对N型通道特异性阻滞剂的敏感性增强。相比之下，β3-Tg小鼠的心房肌对异丙肾上腺素显示出正常的收缩性。此外，它们的心肌细胞显示出正常的钙通道电流，表明通过VDCCs的钙内流未发生改变。Langendorff心脏灌注分析显示β3-Tg小鼠对电场刺激的敏感性增强，而β3基因敲除小鼠和Cav2.2基因敲除小鼠的反应性降低。β3-Tg小鼠基础状态下血浆肾上腺素和去甲肾上腺素水平显著升高，表明交感神经张力增强。对β3-Tg小鼠SCG神经元的电生理分析显示钙通道电流增加，尤其是N型和L型电流。这些结果确定了β3亚基在SCG的N型通道群体中的决定性作用以及在交感神经调节中的主要作用。
