Direct Observation of Compartment-Specific Localization and Dynamics of Voltage-Gated Sodium Channels.
Direct Observation of Compartment-Specific Localization and Dynamics of Voltage-Gated Sodium Channels.
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DOI：
10.1523/jneurosci.0086-22.2022
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发表时间：
2022-07-13
影响因子：
5.3
通讯作者：
Liu, Zhe
中科院分区：
文献类型：
--
作者：
Liu, Hui;Wang, Hong-Gang;Pitt, Geoffrey;Liu, Zhe
关键词：
脑富集的电压门控钠通道（VGSC）Nav1.2和Nav1.6对于CNS中的电信号传导是关键的。先前的研究已经广泛地表征了这两种VGSC的细胞类型特异性表达和电生理特性，以及它们的差异如何有助于神经元兴奋性的微调。然而，由于缺乏可靠的标记和成像方法，这些同源Nav1.2和Nav1.6通道的亚细胞定位和动力学仍然研究不足。为了克服这一挑战，我们结合了基因组编辑，超分辨率和活细胞单分子成像来探测培养的小鼠和大鼠神经元以及雄性和雌性小鼠大脑中Nav1.2和Nav1.6的亚细胞组成，相对丰度和运输动力学。我们发现了一个以前未表征的运输途径，其靶向Nav1.2到无髓鞘神经元的远端轴突。该途径使用存在于跨膜结构域I和II之间的胞内环1中的不同信号来抑制Nav1.2在轴突起始段中的保留并促进其在远端轴突处的膜负载。随着小鼠锥体神经元经历髓鞘形成，Nav1.2逐渐从远端轴突中排除，因为Nav1.6成为轴突初始段和Ranvier结中的主导VGSC。此外，我们揭示了Nav1.2和Nav1.6定位在轴突起始段和树突的精致发育调控，澄清了这些亚细胞区室中钠通道的分子身份。总之，这些结果揭示了VGSC的隔室特异性定位和运输机制，可以单独调节以调节大脑中的膜兴奋性。对内源性电压门控钠通道的直接观察揭示了一种以前未表征的远端轴突靶向机制和不同亚细胞区室中钠通道的分子特性。
Brain enriched voltage-gated sodium channel (VGSC) Nav1.2 and Nav1.6 are critical for electrical signaling in the CNS. Previous studies have extensively characterized cell-type-specific expression and electrophysiological properties of these two VGSCs and how their differences contribute to fine-tuning of neuronal excitability. However, because of a lack of reliable labeling and imaging methods, the subcellular localization and dynamics of these homologous Nav1.2 and Nav1.6 channels remain understudied. To overcome this challenge, we combined genome editing, super-resolution, and live-cell single-molecule imaging to probe subcellular composition, relative abundances, and trafficking dynamics of Nav1.2 and Nav1.6 in cultured mouse and rat neurons and in male and female mouse brain. We discovered a previously uncharacterized trafficking pathway that targets Nav1.2 to the distal axon of unmyelinated neurons. This pathway uses distinct signals residing in the intracellular loop 1 between transmembrane domain I and II to suppress the retention of Nav1.2 in the axon initial segment and facilitate its membrane loading at the distal axon. As mouse pyramidal neurons undergo myelination, Nav1.2 is gradually excluded from the distal axon as Nav1.6 becomes the dominant VGSC in the axon initial segment and nodes of Ranvier. In addition, we revealed exquisite developmental regulation of Nav1.2 and Nav1.6 localizations in the axon initial segment and dendrites, clarifying the molecular identity of sodium channels in these subcellular compartments. Together, these results unveiled compartment-specific localizations and trafficking mechanisms for VGSCs, which could be regulated separately to modulate membrane excitability in the brain. SIGNIFICANCE STATEMENT Direct observation of endogenous voltage-gated sodium channels reveals a previously uncharacterized distal axon targeting mechanism and the molecular identity of sodium channels in distinct subcellular compartments.