The dimensions and structural attachments of tip links in mammalian cochlear hair cells and the effects of exposure to different levels of extracellular calcium
The dimensions and structural attachments of tip links in mammalian cochlear hair cells and the effects of exposure to different levels of extracellular calcium
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DOI：
10.1016/j.neuroscience.2008.02.010
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发表时间：
2008-06-12
期刊：
影响因子：
3.3
通讯作者：
Hackney, C. M.
中科院分区：
文献类型：
--
作者：
Furness, D. N.;Katori, Y.;Hackney, C. M.
已经提出听外侧毛细胞的静纤毛之间的尖端连接包含钙粘蛋白23（CDH 23），其包括结合到由原钙粘蛋白15（PCDH 15）组成的下部的上部分支部分。CDH 23的分子构象、其与PCDH 15的结合、尖端连接和机械电转导先前都已被证明对暴露于低水平的钙敏感。本研究的目的是比较豚鼠耳蜗毛细胞的尖端链接的特性与报道的CDH 23-PCDH 15复合物的特性。使用场发射扫描电子显微镜和透射电子显微镜在常规制剂和处理后的洗涤剂Triton-X-100或不同的钙浓度的细胞外溶液中的尖端链接进行了检查。结果表明，尖端链接有一个扭曲的双链外观与分支的上部区域。它们在静纤毛被去污剂脱膜后存活下来，表明它们在两端都有跨膜结构域。当在2 mM细胞外钙的存在下固定时，它们的长度类似于150 nm。在先前暴露于1 mM钙的情况下，它们的长度与164 nm相似。在50 μ M钙中的长度类似于（类似于185 nm）在100 μ M钙中的CDH 23-PCDH 15复合物中报道的长度（类似于180 nm）。暴露于1 μ M的钙引起的损失的提示链接和剩余的附着点之间的距离增加。数据表明，细胞外钙浓度影响尖端连接长度。与最近提出的尖端-连接结构相容的一个模型是CDH 23双链经历钙依赖性展开，改变连接的长度。束也可能倾斜的方向上最高的行静纤毛的尖端链接延长，然后丢失。总的来说，我们的数据与CDH 23和PCDH 15复合物组成的尖端连接一致，但不排除其他可能性。(C)2008年IBRO。由爱思唯尔有限公司出版。保留所有权利。
The tip links between stereocilia of acousticolateral hair cells have been suggested to contain cadherin 23 (CDH23) comprising an upper branched portion that is bound to a lower portion composed of protocadherin 15 (PCDH15). The molecular conformation of CDH23, its binding to PCDH15, the tip links, and mechanoelectrical transduction have all been shown previously to be sensitive to exposure to low levels of calcium. The aim of this study was to compare the characteristics of tip links in guinea-pig cochlear hair cells with reported features of the CDH23-PCDH15 complex. Tip links were examined using field emission scanning electron microscopy and transmission electron microscopy in conventional preparations and after treatment with the detergent Triton-X-100 or varying calcium concentrations in the extracellular solution. The results showed that tip links have a twisted double-stranded appearance with a branched upper region. They survived demembranation of the stereocilia by detergent suggesting that they have transmembrane domains at both ends. Their lengths, when fixed in the presence of 2 mM extracellular calcium, were similar to 150 nm. With prior exposure to 1 mM calcium their lengths were similar to 164 nm. The lengths in 50 mu M calcium are similar (similar to 185 nm) to those reported for CDH23-PCDH15 complexes in 100 mu M calcium (similar to 180 nm). Exposure to 1 mu M calcium caused loss of tip links and an increased distance between the residual attachment sites. The data indicate that extracellular calcium concentration affects tip-link length. One model compatible with the recently proposed tip-link structure is that the CDH23 double strand undergoes calcium-dependent unfolding, changing the length of the links. The bundle may also tilt in the direction of the tallest row of stereocilia as the tip link lengthens and then is lost. Overall, our data are consistent with a tip link composed of complexes of CDH23 and PCDH15 but do not rule out other possibilities. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.