Differential distribution of harmonin isoforms and their possible role in Usher-1 protein complexes in mammalian photoreceptor cells
Differential distribution of harmonin isoforms and their possible role in Usher-1 protein complexes in mammalian photoreceptor cells
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DOI：
10.1167/iovs.03-0483
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发表时间：
2003-11-01
影响因子：
4.4
通讯作者：
Wolfrum, U
中科院分区：
文献类型：
--
作者：
Reiners, J;Reidel, B;Wolfrum, U
目的。人类Usher综合征是耳聋和失明的最常见形式。Usher I型（USH1）是最严重的类型，其特征是重度先天性耳聋，持续的前庭功能障碍和青春期前发病的视网膜色素变性。先前的研究表明，ush1蛋白myosin VIIa、harmonin和cadherin 23在内耳毛细胞分化过程中相互作用并形成一个功能网络。本研究的目的是分析这些USH1蛋白在哺乳动物视网膜中的分子和细胞功能。产生USH1蛋白抗体，并将其用于视网膜亚细胞光感受器组分的Western blot分析和免疫荧光和电镜观察。和谐素剪接变异体在感光细胞区室中有差异表达。和谐蛋白b同型体局限于光敏感的外段，而和谐蛋白a和c同型体则广泛分布于光感受器中。在感光细胞的突触末端，和声素a和c与肌球蛋白VIIa和钙粘蛋白共定位。USH1分子可以在光感受器突触上组装成一个超分子复合物。这种复合物可能有助于突触前和突触后区域的皮质细胞骨架基质，这被认为在突触连接的组织中起着基本作用。任何USH1复合物伴侣的功能障碍都可能导致突触功能障碍，导致视网膜色素性视网膜炎，这是USH1患者视网膜的临床表型。此外，在光感受器外段，和声素也可能有助于外段蛋白质聚集成超分子复合物。
PURPOSE. Human Usher syndrome is the most common form of combined deafness and blindness. Usher type I (USH1), the most severe form, is characterized by profound congenital deafness, constant vestibular dysfunction, and prepubertal onset retinitis pigmentosa. Previous studies have shown that the USH1-proteins myosin VIIa, harmonin, and cadherin 23 interact and form a functional network during hair cell differentiation in the inner ear. The purpose of the present study was to analyze the molecular and cellular functions of these USH1 proteins in the mammalian retina.METHODS. Antibodies to USH1 proteins were generated and used in Western blot analysis of subcellular photoreceptor fractions and immunofluorescence and electron microscopy of the retina.RESULTS. Splice variants of harmonin were differentially expressed in the photoreceptor cell compartments. Whereas harmonin b isoforms were restricted to the light-sensitive outer segment, the harmonin a and c isoforms were more ubiquitously distributed in the photoreceptors. At the synaptic terminal of photoreceptor cells, harmonin a and c colocalized with myosin VIIa and cadherin 23.CONCLUSIONS. USH1 molecules can assemble to a supramolecular complex at photoreceptor synapses. Such a complex may contribute to the cortical cytoskeletal matrices of the pre- and postsynaptic regions, which are thought to play a fundamental role in the organization of synaptic junctions. Dysfunction of any of the USH1 complex partners may lead to synaptic dysfunction causing retinitis pigmentosa, the clinical phenotype in the retina of patients with USH1. Furthermore, in photoreceptor outer segments, harmonin may also contribute to the clustering of outer segment proteins into supramolecular complexes.