Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.
PLoS One. 2012;7(8):e40079. doi: 10.1371/journal.pone.0040079. Epub 2012 Aug 1.
Voltage-gated sodium channels (VGSCs) play a key role in the initiation and propagation of action potentials in neurons. Na(V)1.8 is a tetrodotoxin (TTX) resistant VGSC expressed in nociceptors, peripheral small-diameter neurons able to detect noxious stimuli. Na(V)1.8 underlies the vast majority of sodium currents during action potentials. Many studies have highlighted a key role for Na(V)1.8 in inflammatory and chronic pain models. Lipid rafts are microdomains of the plasma membrane highly enriched in cholesterol and sphingolipids. Lipid rafts tune the spatial and temporal organisation of proteins and lipids on the plasma membrane. They are thought to act as platforms on the membrane where proteins and lipids can be trafficked, compartmentalised and functionally clustered. In the present study we investigated Na(V)1.8 sub-cellular localisation and explored the idea that it is associated with lipid rafts in nociceptors. We found that Na(V)1.8 is distributed in clusters along the axons of DRG neurons in vitro and ex vivo. We also demonstrated, by biochemical and imaging studies, that Na(V)1.8 is associated with lipid rafts along the sciatic nerve ex vivo and in DRG neurons in vitro. Moreover, treatments with methyl-β-cyclodextrin (MβCD) and 7-ketocholesterol (7KC) led to the dissociation between rafts and Na(V)1.8. By calcium imaging we demonstrated that the lack of association between rafts and Na(V)1.8 correlated with impaired neuronal excitability, highlighted by a reduction in the number of neurons able to conduct mechanically- and chemically-evoked depolarisations. These findings reveal the sub-cellular localisation of Na(V)1.8 in nociceptors and highlight the importance of the association between Na(V)1.8 and lipid rafts in the control of nociceptor excitability.
电压门控钠离子通道(VGSCs)在神经元动作电位的产生和传播中起着关键作用。Na(V)1.8 是一种河豚毒素(TTX)抗性 VGSC,在伤害感受器中表达,伤害感受器是能够检测到有害刺激的外周小直径神经元。Na(V)1.8 是动作电位期间绝大多数钠离子电流的基础。许多研究强调了 Na(V)1.8 在炎症和慢性疼痛模型中的关键作用。脂筏是富含胆固醇和鞘脂的质膜的微区。脂筏调节质膜上蛋白质和脂质的空间和时间组织。它们被认为是质膜上的平台,蛋白质和脂质可以在那里运输、分隔和功能聚类。在本研究中,我们研究了 Na(V)1.8 的亚细胞定位,并探讨了它与伤害感受器中脂筏相关的想法。我们发现 Na(V)1.8 沿 DRG 神经元的轴突在体外和体内呈簇状分布。我们还通过生化和成像研究证明,Na(V)1.8 与坐骨神经体外和 DRG 神经元体外的脂筏相关。此外,用甲基-β-环糊精(MβCD)和 7-酮胆固醇(7KC)处理导致筏和 Na(V)1.8 分离。通过钙成像,我们证明了筏和 Na(V)1.8 之间缺乏关联与神经元兴奋性受损相关,这表现为能够进行机械和化学去极化的神经元数量减少。这些发现揭示了伤害感受器中 Na(V)1.8 的亚细胞定位,并强调了 Na(V)1.8 与脂筏之间的关联在控制伤害感受器兴奋性中的重要性。