Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
Department of Pediatrics, Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd, The University of Texas at Austin, Dell Medical School, Austin, TX 78712, USA.
J Cell Sci. 2023 Mar 1;136(5). doi: 10.1242/jcs.259535. Epub 2022 Jun 22.
Most motile cilia have a stereotyped structure of nine microtubule outer doublets and a single central pair of microtubules. The central pair of microtubules are surrounded by a set of proteins, termed the central pair apparatus. A specific kinesin, Klp1 projects from the central pair and contributes to ciliary motility in Chlamydomonas. The vertebrate ortholog, Kif9, is required for beating in mouse sperm flagella, but the mechanism of Kif9/Klp1 function remains poorly defined. Here, using Xenopus epidermal multiciliated cells, we show that Kif9 is necessary for ciliary motility and the proper distal localization of not only central pair proteins, but also radial spokes and dynein arms. In addition, single-molecule assays in vitro reveal that Xenopus Kif9 is a long-range processive motor, although it does not mediate long-range movement in ciliary axonemes in vivo. Together, our data suggest that Kif9 is integral for ciliary beating and is necessary for proper axonemal distal end integrity.
大多数运动纤毛具有九对外周微管二联体和一个单一的中央微管对的刻板结构。中央微管对被一组称为中央对装置的蛋白质所包围。一种特定的驱动蛋白 Klp1 从中央对中伸出，并有助于衣藻中的纤毛运动。脊椎动物的同源物 Kif9 对于小鼠精子鞭毛的跳动是必需的，但 Kif9/Klp1 功能的机制仍未得到很好的定义。在这里，我们使用非洲爪蟾表皮多纤毛细胞表明，Kif9 对于纤毛运动和不仅中央对蛋白，而且辐条和动力蛋白臂的适当远端定位都是必需的。此外，体外的单分子测定表明，非洲爪蟾 Kif9 是一种长程的进行性马达，尽管它在体内的纤毛轴突中并不介导长程运动。总之，我们的数据表明 Kif9 对于纤毛的跳动是必不可少的，并且对于轴突末端的完整性是必要的。
