Homma Kazuaki, Miller Katharine K, Anderson Charles T, Sengupta Soma, Du Guo-Guang, Aguiñaga Salvador, Cheatham Maryann, Dallos Peter, Zheng Jing
Department of Communication Sciences and Disorders, The Hugh Knowles Center, Northwestern University, Evanston, IL 60208, USA.
Biochim Biophys Acta. 2010 Jun;1798(6):1029-40. doi: 10.1016/j.bbamem.2010.02.001. Epub 2010 Feb 6.
Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated chloride channel that is present in a variety of epithelial cell types, and usually expressed in the luminal membrane. In contrast, prestin (SLC26A5) is a voltage-dependent motor protein, which is present in the basolateral membrane of cochlear outer hair cells (OHCs), and plays an important role in the frequency selectivity and sensitivity of mammalian hearing. By using in situ hybridization and immunofluorescence, we found that both mRNA and protein of CFTR are present in OHCs, and that CFTR localizes in both the apical and the lateral membranes. CFTR was not detected in the lateral membrane of inner hair cells (IHCs) or in that of OHCs derived from prestin-knockout mice, i.e., in instances where prestin is not expressed. These results suggest that prestin may interact physically with CFTR in the lateral membrane of OHCs. Immunoprecipitation experiments confirmed a prestin-CFTR interaction. Because chloride is important for prestin function and for the efferent-mediated inhibition of cochlear output, the prestin-directed localization of CFTR to the lateral membrane of OHCs has a potential physiological significance. Aside from its role as a chloride channel, CFTR is known as a regulator of multiple protein functions, including those of the solute carrier family 26 (SLC26). Because prestin is in the SLC26 family, several members of which interact with CFTR, we explored the potential modulatory relationship associated with a direct, physical interaction between prestin and CFTR. Electrophysiological experiments demonstrated that cAMP-activated CFTR is capable of enhancing voltage-dependent charge displacement, a signature of OHC motility, whereas prestin does not affect the chloride conductance of CFTR.
囊性纤维化跨膜传导调节因子（CFTR）是一种由环磷酸腺苷（cAMP）激活的氯离子通道，存在于多种上皮细胞类型中，通常表达于管腔膜。相比之下，prestin（溶质载体家族26成员5，SLC26A5）是一种电压依赖性马达蛋白，存在于耳蜗外毛细胞（OHC）的基底外侧膜中，在哺乳动物听力的频率选择性和敏感性方面发挥重要作用。通过原位杂交和免疫荧光技术，我们发现CFTR的信使核糖核酸（mRNA）和蛋白质均存在于OHC中，且CFTR定位于顶端膜和侧面膜。在内毛细胞（IHC）的侧面膜或来自prestin基因敲除小鼠的OHC侧面膜中未检测到CFTR，即在prestin不表达的情况下。这些结果表明，prestin可能在OHC的侧面膜中与CFTR发生物理相互作用。免疫沉淀实验证实了prestin与CFTR之间的相互作用。由于氯离子对prestin功能以及传出神经介导的耳蜗输出抑制很重要，CFTR在prestin引导下定位到OHC的侧面膜具有潜在的生理意义。除了作为氯离子通道的作用外，CFTR还作为多种蛋白质功能的调节因子而为人所知，包括溶质载体家族26（SLC26）的蛋白质功能。由于prestin属于SLC26家族，该家族的几个成员与CFTR相互作用，我们探讨了prestin与CFTR之间直接物理相互作用相关的潜在调节关系。电生理实验表明，cAMP激活的CFTR能够增强电压依赖性电荷位移，这是OHC运动性的一个特征，而prestin不影响CFTR的氯电导。
