Howard Hughes Medical Institute, Department of Cardiology, Boston Children's Hospital, Boston, Massachusetts 02115, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, Massachusetts 02478, and Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia.
J Neurosci. 2014 Mar 5;34(10):3653-67. doi: 10.1523/JNEUROSCI.2274-13.2014.
Transient receptor potential (TRP) channels are abundant in the brain where they regulate transmission of sensory signals. The expression patterns of different TRPC subunits (TRPC1, 4, and 5) are consistent with their potential role in fear-related behaviors. Accordingly, we found recently that mutant mice lacking a specific TRP channel subunit, TRPC5, exhibited decreased innate fear responses. Both TRPC5 and another member of the same subfamily, TRPC4, form heteromeric complexes with the TRPC1 subunit (TRPC1/5 and TRPC1/4, respectively). As TRP channels with specific subunit compositions may have different functional properties, we hypothesized that fear-related behaviors could be differentially controlled by TRPCs with distinct subunit arrangements. In this study, we focused on the analysis of mutant mice lacking the TRPC4 subunit, which, as we confirmed in experiments on control mice, is expressed in brain areas implicated in the control of fear and anxiety. In behavioral experiments, we found that constitutive ablation of TRPC4 was associated with diminished anxiety levels (innate fear). Furthermore, knockdown of TRPC4 protein in the lateral amygdala via lentiviral-mediated gene delivery of RNAi mimicked the behavioral phenotype of constitutive TRPC4-null (TRPC4(-/-)) mouse. Recordings in brain slices demonstrated that these behavioral modifications could stem from the lack of TRPC4 potentiation in neurons in the lateral nucleus of the amygdala through two Gαq/11 protein-coupled signaling pathways, activated via Group I metabotropic glutamate receptors and cholecystokinin 2 receptors, respectively. Thus, TRPC4 and the structurally and functionally related subunit, TRPC5, may both contribute to the mechanisms underlying regulation of innate fear responses.
瞬时受体电位 (TRP) 通道在大脑中丰富存在，它们调节感觉信号的传递。不同 TRPC 亚基（TRPC1、4 和 5）的表达模式与其在与恐惧相关的行为中的潜在作用一致。因此，我们最近发现缺乏特定 TRP 通道亚基 TRPC5 的突变小鼠表现出降低的先天恐惧反应。TRPC5 和同一亚家族的另一个成员 TRPC4 都与 TRPC1 亚基形成异源三聚体复合物（分别为 TRPC1/5 和 TRPC1/4）。由于具有特定亚基组成的 TRP 通道可能具有不同的功能特性，我们假设具有不同亚基排列的 TRPC 可能会以不同的方式控制与恐惧相关的行为。在这项研究中，我们专注于分析缺乏 TRPC4 亚基的突变小鼠，正如我们在对照小鼠实验中证实的那样，TRPC4 亚基在参与恐惧和焦虑控制的大脑区域中表达。在行为实验中，我们发现 TRPC4 的组成性缺失与焦虑水平降低（先天恐惧）有关。此外，通过慢病毒介导的 RNAi 基因传递在外侧杏仁核中敲低 TRPC4 蛋白模拟了组成型 TRPC4 缺失（TRPC4(-/-)）小鼠的行为表型。脑片记录表明，这些行为改变可能源于外侧杏仁核神经元中缺乏 TRPC4 的增强作用，这是通过两种 Gαq/11 蛋白偶联信号通路实现的，分别通过 I 组代谢型谷氨酸受体和胆囊收缩素 2 受体激活。因此，TRPC4 和结构和功能相关的亚基 TRPC5 可能都有助于调节先天恐惧反应的机制。
