Tectorins crosslink type II collagen fibrils and connect the tectorial membrane to the spiral limbus.
Tectorins crosslink type II collagen fibrils and connect the tectorial membrane to the spiral limbus.
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DOI：
10.1016/j.jsb.2016.01.006
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发表时间：
2016-05
影响因子：
3
通讯作者：
Kachar B
中科院分区：
文献类型：
--
作者：
Andrade LR;Salles FT;Grati M;Manor U;Kachar B
所有的内耳器官都具有覆盖感觉上皮的细胞外基质附件，这对于它们的正常功能至关重要。覆膜（TM）是位于听觉感觉上皮上方的凝胶状无细胞膜，主要由II型胶原蛋白以及α-和β-tectorins组成。TM分子在内淋巴液环境中自组装，中间与螺旋利姆布斯相互作用，远端与外毛细胞静纤毛相互作用。在这里，我们使用免疫金标记在冷冻替代小鼠耳蜗，以评估两个tectorins在不同的TM区域的精细定位。我们观察到TM通过富含α-和β-tectorin的致密薄基质粘附在螺旋状利姆布斯上，两者都可能与牙间细胞的膜结合。冷冻蚀刻图像显示，II型胶原原纤维由短细丝（4 ± 1.5 nm，宽度）交联，类似于另一种胶原蛋白类型的蛋白质，或球状元件链（15 ± 3.2 nm，直径）。两种tectorins的金颗粒也位于II型胶原纤维附近，表明这些小球可能主要由α-和β-tectorins组成。最后，在TM下侧存在金颗粒表明，外毛细胞静纤毛膜有一个分子伴侣tectorins，可能是stereocilin，允许TM和Corti器官之间的物理连接。
All inner ear organs possess extracellular matrix appendices over the sensory epithelia that are crucial for their proper function. The tectorial membrane (TM) is a gelatinous acellular membrane located above the hearing sensory epithelium and is composed mostly of type II collagen, and α– and β–tectorins. TM molecules self-assemble in the endolymph fluid environment, interacting medially with the spiral limbus and distally with the outer hair cell stereocilia. Here, we used immunogold labeling in freeze-substituted mouse cochleae to assess the fine localization of both tectorins in distinct TM regions. We observed that the TM adheres to the spiral limbus through a dense thin matrix enriched in α- and β–tectorin, both likely bound to the membranes of interdental cells. Freeze-etching images revealed that type II collagen fibrils were crosslinked by short thin filaments (4 ± 1.5 nm, width), resembling another collagen type protein, or chains of globular elements (15 ± 3.2 nm, diameter). Gold-particles for both tectorins also localized adjacent to the type II collagen fibrils, suggesting that these globules might be composed essentially of α- and β-tectorins. Finally, the presence of gold-particles at the TM lower side suggests that the outer hair cell stereocilia membrane has a molecular partner to tectorins, probably stereocilin, allowing the physical connection between the TM and the organ of Corti.