Chen Wei Chun, Davis Robin L
Department of Cell Biology and Neuroscience, Nelson Laboratories, Rutgers University, 604 Allison Road, Piscataway, NJ 08854, USA.
Hear Res. 2006 Dec;222(1-2):89-99. doi: 10.1016/j.heares.2006.09.002. Epub 2006 Nov 1.
The systematically varied firing features of spiral ganglion neurons provide an excellent model system for the exploration of how graded ion channel distributions can be used to organize neuronal firing across a population of neurons. Elucidating the underlying mechanisms that determine neuronal response properties requires a complete understanding of the combination of ion channels, auxiliary proteins, modulators, and second messengers that form this highly organized system in the auditory periphery. Toward this goal, we built upon previous studies of voltage-gated K+-selective ion channels (Kv), and expanded our analysis to K+-selective leak channels (KCNK), which can play a major role in setting the basic firing characteristics of spiral ganglion neurons. To begin a more comprehensive analysis of Kv and KCNK channels, a screening approach was employed. RT-PCR was utilized to examine gene expression, the major results of which were confirmed with immunocytochemistry. Initial studies validated this approach by accurately detecting voltage-dependent K+ channels that were documented previously in the spiral ganglion. Furthermore, an additional channel type within the Kv3 family, Kv3.3, was identified and further characterized. The major focus of the study, however, was to systematically examine gene expression levels of the KCNK family of K+-selective leak channels. These channel types determine the resting membrane potential which has a major impact on setting the level of neuronal excitation. TWIK-1, TASK-3, TASK-1, and TREK-1 were expressed in the spiral ganglion; TWIK-1 was specifically localized with immunocytochemistry to the neuronal somata and initial processes of spiral ganglion neurons in vitro.
螺旋神经节神经元系统变化的放电特征为探索分级离子通道分布如何用于组织神经元群体的放电提供了一个出色的模型系统。阐明决定神经元反应特性的潜在机制需要全面了解形成听觉外周这个高度组织化系统的离子通道、辅助蛋白、调节剂和第二信使的组合。为了实现这一目标，我们在先前对电压门控钾离子选择性离子通道（Kv）的研究基础上，将分析扩展到钾离子选择性泄漏通道（KCNK），其在设定螺旋神经节神经元的基本放电特征中可能起主要作用。为了开始对Kv和KCNK通道进行更全面的分析，采用了一种筛选方法。利用逆转录聚合酶链反应（RT-PCR）检测基因表达，其主要结果通过免疫细胞化学得到证实。初步研究通过准确检测先前在螺旋神经节中记录的电压依赖性钾离子通道验证了该方法。此外，还鉴定并进一步表征了Kv3家族中的另一种通道类型Kv3.3。然而，该研究的主要重点是系统地检查钾离子选择性泄漏通道KCNK家族的基因表达水平。这些通道类型决定静息膜电位，而静息膜电位对设定神经元兴奋水平有重大影响。TWIK-1、TASK-3、TASK-1和TREK-1在螺旋神经节中表达；在体外，通过免疫细胞化学将TWIK-1特异性定位到螺旋神经节神经元的胞体和起始突起。
