Genetic, Cellular, and Functional Evidence for Ca2+ Inflow through Cav1.2 and Cav1.3 Channels in Murine Spiral Ganglion Neurons
Genetic, Cellular, and Functional Evidence for Ca2+ Inflow through Cav1.2 and Cav1.3 Channels in Murine Spiral Ganglion Neurons
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小鼠螺旋神经节神经元中 Ca2 通过 Cav1.2 和 Cav1.3 通道流入的遗传、细胞和功能证据
DOI：
10.1523/jneurosci.5416-13.2014
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发表时间：
2014-05-21
影响因子：
5.3
通讯作者：
Yamoah, Ebenezer N.
中科院分区：
文献类型：
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作者：
Lv, Ping;Kim, Hyo Jeong;Yamoah, Ebenezer N.
第八神经的螺旋神经节神经元（SGN）充当毛细胞和耳蜗核之间的桥梁。毛细胞使用 Ca(v)1.3 作为 Ca2+ 流入的主要通道来介导递质释放。相比之下，SGN 配备多个 Ca2+ 通道来介导 Ca2+ 依赖性功能。我们使用 Ca(v)1.3 缺陷小鼠 (Ca(v)1.3(-/-)) 直接检查了 Ca(v)1.3 通道在 SGN 中的作用。我们发现了一个令人惊讶的发现，即 SGN 功能性地表达心脏特异性 Ca(v)1.2 以及神经元 Ca(v)1.3 通道。我们发现，与野生型 (Ca(v)1.3(+/+)) 小鼠相比，SGN 记录的诱发动作电位显示 Ca(v)1.3(-/-) 小鼠的放电频率显着降低。尽管 Ca(v)1.3 是神经元中指定的 L 型通道，但在 Ca(v)1.3(-/-) 小鼠分离的 SGN 中记录的全细胞电流显示出令人惊讶的残余电流，对二氢吡啶 (DHP) 激动剂和拮抗剂具有敏感性，并且与 Ca(v)1.3(+/+) 小鼠相比，电压依赖性激活存在去极化转变。事实上，对 Ca(v)1.3(+/+) 神经元中 Ca2+ 通道基本特性的直接测量证实了两个 DHP 敏感单通道电流的存在，具有不同的开放概率和电导。我们证明 Ca(v)1.3(-/-) 小鼠中的 DHP 敏感电流源自 Ca(v)1.2 通道活动，据我们所知，首次提供了神经元中 Ca(v)1.2 电流表达的功能数据。最后，使用 shRNA 基因敲低方法，并对 Ca(v)1.2(+/-) 和 Ca(v)1.3(+/-) 小鼠的 SGN 进行组织学分析，我们能够确定 Ca(v)1.2 和 Ca(v)1.3 在 SGN 中的不同作用。
Spiral ganglion neurons (SGNs) of the eighth nerve serve as the bridge between hair cells and the cochlear nucleus. Hair cells use Ca(v)1.3 as the primary channel for Ca2+ inflow to mediate transmitter release. In contrast, SGNs are equipped with multiple Ca2+ channels to mediate Ca2+-dependent functions. We examined directly the role of Ca(v)1.3 channels in SGNs using Ca(v)1.3-deficient mice (Ca(v)1.3(-/-)). We revealed a surprising finding that SGNs functionally express the cardiac-specific Ca(v)1.2, as well as neuronal Ca(v)1.3 channels. We show that evoked action potentials recorded from SGNs show a significant decrease in the frequency of firing in Ca(v)1.3(-/-) mice compared with wild-type (Ca(v)1.3(+/+)) littermates. Although Ca(v)1.3 is the designated L-type channel in neurons, whole-cell currents recorded in isolated SGNs from Ca(v)1.3(-/-) mice showed a surprising remnant current with sensitivity toward the dihydropyridine (DHP) agonist and antagonist, and a depolarization shift in the voltage- dependent activation compared with that in the Ca(v)1.3(+/+) mice. Indeed, direct measurement of the elementary properties of Ca2+ channels, in Ca(v)1.3(+/+) neurons, confirmed the existence of two DHP- sensitive single- channel currents, with distinct open probabilities and conductances. Wedemonstrate that the DHP-sensitive current in Ca(v)1.3(-/-) mice is derived from Ca(v)1.2 channel activity, providing for the first time, to our knowledge, functional data for the expression of Ca(v)1.2 currents in neurons. Finally, using shRNA gene knockdown methodology, and histological analyses of SGNs from Ca(v)1.2(+/-) and Ca(v)1.3(+/-) mice, we were able to establish the differential roles of Ca(v)1.2 and Ca(v)1.3 in SGNs.