Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616.
Department of Biology, Santa Clara University, Santa Clara, CA 95053.
Mol Biol Cell. 2021 Nov 1;32(21):br8. doi: 10.1091/mbc.E20-12-0786. Epub 2021 Aug 18.
The core structure of motile cilia and flagella, the axoneme, is built from a stable population of doublet microtubules. This unique stability is brought about, at least in part, by a network of microtubule inner proteins (MIPs) that are bound to the luminal side of the microtubule walls. Rib72A and Rib72B were identified as MIPs in the motile cilia of the protist . Loss of these proteins leads to ciliary defects and loss of additional MIPs. We performed mass spectrometry coupled with proteomic analysis and bioinformatics to identify the MIPs lost in knockout axonemes. We identified a number of candidate MIPs and pursued one, Fap115, for functional characterization. We find that loss of Fap115 results in disrupted cell swimming and aberrant ciliary beating. Cryo-electron tomography reveals that Fap115 localizes to MIP6a in the A-tubule of the doublet microtubules. Overall, our results highlight the complex relationship between MIPs, ciliary structure, and ciliary function.
运动纤毛和鞭毛的核心结构轴丝是由稳定的二联体微管组成的。这种独特的稳定性至少部分是由微管内蛋白（MIPs）网络带来的，这些 MIPs 结合在微管壁的内腔侧。Rib72A 和 Rib72B 被鉴定为原生生物运动纤毛中的 MIPs。这些蛋白质的缺失会导致纤毛缺陷和额外 MIPs 的丢失。我们进行了质谱分析结合蛋白质组学分析和生物信息学，以鉴定 缺失的 MIPs。我们鉴定了一些候选 MIPs，并对其中一个，Fap115，进行了功能特征分析。我们发现 Fap115 的缺失会导致细胞游动和纤毛摆动异常。冷冻电子断层扫描显示 Fap115 定位于二联体微管 A 管的 MIP6a。总的来说，我们的结果强调了 MIPs、纤毛结构和纤毛功能之间的复杂关系。
