Neuronal excitability is determined by the combination of different ion channels and their sub-neuronal localization. This study utilizes protein trap fly strains with endogenously tagged channels to analyze the spatial expression patterns of the four Shaker-related voltage-gated potassium channels, Kv1-4, in the larval, pupal, and adult Drosophila ventral nerve cord. We find that all four channels (Shaker, Kv1; Shab, Kv2; Shaw, Kv3; and Shal, Kv4) each show different spatial expression patterns in the Drosophila ventral nerve cord and are predominantly targeted to different sub-neuronal compartments. Shaker is abundantly expressed in axons, Shab also localizes to axons but mostly in commissures, Shaw expression is restricted to distinct parts of neuropils, and Shal is found somatodendritically, but also in axons of identified motoneurons. During early pupal life expression of all four Shaker-related channels is markedly decreased with an almost complete shutdown of expression at early pupal stage 5 (∼30% through metamorphosis). Re-expression of Kv1-4 channels at pupal stage 6 starts with abundant channel localization in neuronal somata, followed by channel targeting to the respective sub-neuronal compartments until late pupal life. The developmental time course of tagged Kv1-4 channel expression corresponds with previously published data on developmental changes in single neuron physiology, thus indicating that protein trap fly strains are a useful tool to analyze developmental regulation of potassium channel expression. Finally, we take advantage of the large diameter of the giant fiber (GF) interneuron to map channel expression onto the axon and axon terminals of an identified interneuron. Shaker, Shaw, and Shal but not Shab channels localize to the non-myelinated GF axonal membrane and axon terminals. This study constitutes a first step toward systematically analyzing sub-neuronal potassium channel localization in Drosophila. Functional implications as well as similarities and differences to Kv1-4 channel localization in mammalian neurons are discussed.

中文翻译：

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果蝇变态过程中电压门控钾通道的差异定位。

神经元兴奋性由不同离子通道及其亚神经元定位的组合决定。本研究利用具有内源性标记通道的蛋白诱捕蝇株来分析四个 Shaker 相关电压门控钾通道 Kv1-4 在幼虫、蛹和成虫果蝇腹神经索中的空间表达模式。我们发现所有四个通道（Shaker，Kv1；Shab，Kv2；Shaw，Kv3；Shal，Kv4）在果蝇腹侧神经索中均显示出不同的空间表达模式，并且主要针对不同的亚神经元隔室。Shaker 在轴突中大量表达，Shab 也定位于轴突，但主要位于连合处，Shaw 表达仅限于神经纤维的不同部分，Shal 存在于躯体树突中，但也在已识别运动神经元的轴突中。在蛹的早期，所有四个 Shaker 相关通道的表达都显着降低，在蛹早期 5 阶段几乎完全停止表达（约 30% 通过变态）。Kv1-4 通道在蛹第 6 阶段的重新表达始于神经元胞体中丰富的通道定位，然后是通道靶向各自的亚神经元隔室，直到蛹生命晚期。标记 Kv1-4 通道表达的发育时间过程与先前公布的关于单个神经元生理发育变化的数据相对应，因此表明蛋白质陷阱蝇株是分析钾通道表达发育调节的有用工具。最后，我们利用巨纤维 (GF) 中间神经元的大直径将通道表达映射到已识别中间神经元的轴突和轴突末端。Shaker、Shaw 和 Shaw（但不是 Shab 通道）定位于无髓鞘 GF 轴突膜和轴突末端。这项研究是系统分析果蝇亚神经元钾通道定位的第一步。讨论了哺乳动物神经元中 Kv1-4 通道定位的功能意义以及异同。