Maintenance of stereocilia and apical junctional complexes by Cdc42 in cochlear hair cells
Maintenance of stereocilia and apical junctional complexes by Cdc42 in cochlear hair cells
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DOI：
10.1242/jcs.143602
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发表时间：
2014-05-01
影响因子：
4
通讯作者：
Saito, Naoaki
中科院分区：
文献类型：
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作者：
Ueyama, Takehiko;Sakaguchi, Hirofumi;Saito, Naoaki
cdc 42是动态肌动蛋白组织的关键调节因子。然而，很少有人知道Cdc 42依赖的肌动蛋白调节如何影响稳态肌动蛋白结构在分化的上皮细胞。我们采用内耳毛细胞特异性条件性敲除分析Cdc 42在具有高度精细稳定的肌动蛋白突起（静纤毛）的毛细胞中的作用。Atoh 1-Cre毛细胞; cdc 42（flox/flox）小鼠发育正常，但成熟后逐渐退化，导致进行性听力损失，特别是在高频。内毛细胞比外毛细胞更强烈的耳蜗毛细胞变性，并开始静纤毛融合和耗尽，伴随着变薄和波浪形的环形肌动蛋白带在顶端连接复合体（AJCs）。腺病毒编码的GFP-Cdc 42在毛细胞中的表达和来自表达Cdc 42-FRET生物传感器的转基因小鼠的毛细胞的荧光共振能量转移（FRET）成像表明Cdc 42在耳蜗毛细胞中的静纤毛膜和AJCs处的存在和活化。Cdc 42敲低MDCK细胞产生的表型类似于Cdc 42缺失的毛细胞，包括异常的微绒毛和破坏的AJC，并下调肌动蛋白的营业额由磷酸化cofilin水平的提高。因此，Cdc 42通过精细调节肌动蛋白周转来影响稳定肌动蛋白结构的维持，并维持耳蜗毛细胞的功能和活力。
Cdc42 is a key regulator of dynamic actin organization. However, little is known about how Cdc42-dependent actin regulation influences steady-state actin structures in differentiated epithelia. We employed inner ear hair-cell-specific conditional knockout to analyze the role of Cdc42 in hair cells possessing highly elaborate stable actin protrusions (stereocilia). Hair cells of Atoh1-Cre; Cdc42(flox/flox) mice developed normally but progressively degenerated after maturation, resulting in progressive hearing loss particularly at high frequencies. Cochlear hair cell degeneration was more robust in inner hair cells than in outer hair cells, and began as stereocilia fusion and depletion, accompanied by a thinning and waving circumferential actin belt at apical junctional complexes (AJCs). Adenovirus-encoded GFP-Cdc42 expression in hair cells and fluorescence resonance energy transfer (FRET) imaging of hair cells from transgenic mice expressing a Cdc42-FRET biosensor indicated Cdc42 presence and activation at stereociliary membranes and AJCs in cochlear hair cells. Cdc42-knockdown in MDCK cells produced phenotypes similar to those of Cdc42-deleted hair cells, including abnormal microvilli and disrupted AJCs, and downregulated actin turnover represented by enhanced levels of phosphorylated cofilin. Thus, Cdc42 influenced the maintenance of stable actin structures through elaborate tuning of actin turnover, and maintained function and viability of cochlear hair cells.