果蝇的听觉系统与人类很相似，Iowa大学的生物学家Daniel Eberl及其同事利用果蝇的“情歌”进行研究，发现听觉系统拥有与汽车蓄电池类似的机制。这项研究作为封面文章发表在最近一期的美国国家科学院院刊PNAS杂志上。
对于可兴奋细胞的活性（听觉细胞等）来说，离子内稳态特别重要，而这依赖于一种相当于Na+/K+泵的蛋白——Na+/K+ ATPase。该蛋白由一个α亚基和一个β亚基组成，也常被简称为钠泵。研究人员发现，在果蝇耳部专门的支持细胞（scolopale细胞）中，这种钠泵高度表达。
在果蝇的听觉系统中scolopale细胞是很重要的，它环绕着果蝇耳部的感觉末梢，形成密闭的细胞外隔室（scolopale space）。研究人员指出，果蝇听觉系统的这种小隔室与蓄电池作用相似，需要先充电然后才能在系统中释放电子。充电完成后，这种隔室释放出的离子就会通过感觉末梢上的膜通道，这些通道是由声音激活而短暂开启的。
果蝇的“情歌”是指一种翅膀振动发出的声音，研究人员巧妙利用这一求爱之声，根据果蝇是否能听见这种声音，来研究其听觉系统的电反应。为此，研究人员在果蝇的触须里插入了微小的电极，随后他们用电脑播放果蝇的求爱之歌，并对其间的电反应进行检测。
研究显示，钠泵在scolopale细胞中有着特别重要的作用，负责帮助细胞向隔室中补充正确的离子，如果钠泵出现故障就会导致果蝇丧失听力。
人类耳部的听觉系统也存在着一种隔室——中阶（scala media），其作用也是向耳部的感觉细胞释放离子。研究人员指出，果蝇和人类的听觉系统有许多相似之处。在果蝇模型中研究耳部离子平衡所需的各项元件，有助于人们进一步了解人类的听觉系统。(生物谷Bioon.com)
doi: 10.1073/pnas.1208866110
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Cell-type–specific roles of Na+/K+ ATPase subunits in Drosophila auditory mechanosensation
Madhuparna Roy, Elena Sivan-Loukianova, and Daniel F. Eberl1
Ion homeostasis is a fundamental cellular process particularly important in excitable cell activities such as hearing. It relies on the Na+/K+ ATPase (also referred to as the Na pump), which is composed of a catalytic α subunit and a β subunit required for its transport to the plasma membrane and for regulating its activity. We show that α and β subunits are expressed in Johnston's organ (JO), the Drosophila auditory organ. We knocked down expression of α subunits (ATPα and α-like) and β subunits (nrv1, nrv2, and nrv3) individually in JO with UAS/Gal4-mediated RNAi. ATPα shows elevated expression in the ablumenal membrane of scolopale cells, which enwrap JO neuronal dendrites in endolymph-like compartments. Knocking down ATPα, but not α-like, in the entire JO or only in scolopale cells using specific drivers, resulted in complete deafness. Among β subunits, nrv2 is expressed in scolopale cells and nrv3 in JO neurons. Knocking down nrv2 in scolopale cells blocked Nrv2 expression, reduced ATPα expression in the scolopale cells, and caused almost complete deafness. Furthermore, knockdown of either nrv2 or ATPα specifically in scolopale cells causes abnormal, electron-dense material accumulation in the scolopale space. Similarly, nrv3 functions in JO but not in scolopale cells, suggesting neuron specificity that parallels nrv2 scolopale cell–specific support of the catalytic ATPα. Our studies provide an amenable model to investigate generation of endolymph-like extracellular compartments.
