Apical endocytosis in outer hair cells of the mammalian cochlea
Apical endocytosis in outer hair cells of the mammalian cochlea
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DOI：
10.1111/j.0953-816x.2004.03452.x
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发表时间：
2004-07-01
影响因子：
3.4
通讯作者：
Ashmore, JF
中科院分区：
文献类型：
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作者：
Griesinger, CB;Richards, CD;Ashmore, JF
外毛细胞（OHC）是哺乳动物耳蜗的感觉运动细胞，在其顶端静纤毛下方含有一个内吞的管泡室。我们已经使用了双光子成像的FM 1 -43在完整的上皮细胞显示，这些细胞采取膜在一个Ca 2+依赖的方式从一个不同的顶端网站。摄取速率为0.8 μ m（2）/s，内化的膜被迅速运输到一个隔室沿着侧壁和不同的细胞内隔室。用FM 1 -43和DiOC（6）（一种内质网（ER）标记物）进行双标记，表明这些隔室是OHC的管泡内质网的一部分。用溶酶体标记物标记显示OHC溶酶体局限于顶端。使用蛋白质标记小麦胚芽凝集素（WGA-FITC），我们证明，顶端蛋白质的内化和贩运是约8倍慢于膜内化。使用FM 1 -43和WGA-FITC双标记，我们表明，膜和蛋白质的内化是顶部共定位，但蛋白质和膜交通的模式不同。蛋白质仅针对侧壁的最顶端的三分之一。在对照条件下，OHC显示只有弱的WGA-FITC表面标记的网站的内吞作用。降低顶端内吞速率会增加这种表面信号。结果表明，OHCs内吞膜和膜蛋白具有高周转率，这些细胞可以使用顶端内吞通过间接途径对侧膜的蛋白质进行分选。
Outer hair cells (OHCs), the sensory-motor cells of the mammalian cochlea, contain an endocytic tubulovesicular compartment below their apical stereocilia. We have used two-photon imaging of FM1-43 in the intact epithelium to show that these cells take up membrane in a Ca2+-dependent manner from a distinct apical site. The uptake rate was 0.8 mum(2)/s and internalized membrane was trafficked rapidly to a compartment along the lateral wall and distinct intracellular compartments. Double labelling with FM1-43 and DiOC(6), an endoplasmic reticulum (ER) marker, showed that these compartments are part of the tubulovesicular endoplasmic reticulum of OHCs. Labelling with a lysosomal marker showed that OHC lysosomes are restricted to the apex. Using the protein marker wheat germ agglutinin (WGA-FITC) we demonstrate that apical protein internalization and trafficking is about eight times slower than membrane internalization. Using double labelling with FM1-43 and WGA-FITC, we show that membrane and protein internalization are apically colocalized but that patterns of protein and membrane traffic differ. Protein was targeted only to the most apical third of the lateral wall. In control conditions, OHCs displayed only weak WGA-FITC surface labelling at the site of endocytosis. Lowering the rate of apical endocytosis increased this surface signal. The results suggest that OHCs endocytose membrane and membrane proteins with a high turnover rate and that these cells may use apical endocytosis to sort proteins via an indirect pathway to the lateral membrane.