Tasaki Koshi, Satoda Yuuki, Chiba Shuhei, Shin Hye-Won, Katoh Yohei, Nakayama Kazuhisa
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
Laboratory of Molecular and Cellular Biology, Tohoku University, Aobayama, Sendai, Miyagi 980-8578, Japan.
Mol Biol Cell. 2025 Apr 1;36(4):ar48. doi: 10.1091/mbc.E24-11-0509. Epub 2025 Feb 28.
The intraflagellar transport (IFT) machinery, containing the IFT-A and IFT-B complexes and powered by dynein-2 and kinesin-2 motors, is crucial for bidirectional trafficking of ciliary proteins and their import/export across the transition zone (TZ). Stepwise assembly of anterograde IFT trains was proposed previously; that is, the IFT-B complex first forms a TZ-tethered scaffold with sequential incorporation of IFT-A, dynein-2, and finally kinesin-2. However, IFT-A and IFT-B complexes also demonstrate distinct localization to the basal body/mother centriole. We show that IFT-A, IFT-B, and dynein-2 complexes are recruited to the mother centriole independently of ciliogenesis. Furthermore, mother centriole recruitment of IFT-A and IFT-B can occur in the absence of IFT-B and IFT-A, respectively, and dynein-2 recruitment is independent of IFT-A and IFT-B. Expansion microscopy revealed that the IFT-A/IFT-B pool at the basal body is distinct from that at the TZ. We conclude that IFT-A and IFT-B are recruited to the mother centriole in a mutually independent and ciliogenesis-independent manner before IFT train assembly.
鞭毛内运输（IFT）机制包含IFT-A和IFT-B复合物，并由动力蛋白-2和驱动蛋白-2驱动，对纤毛蛋白的双向运输及其在过渡区（TZ）的进出至关重要。先前有人提出了顺行IFT列车的逐步组装过程；也就是说，IFT-B复合物首先形成一个与TZ相连的支架，随后依次加入IFT-A、动力蛋白-2，最后是驱动蛋白-2。然而，IFT-A和IFT-B复合物在基体/母中心粒上也表现出不同的定位。我们发现，IFT-A、IFT-B和动力蛋白-2复合物被招募到母中心粒的过程与纤毛发生无关。此外，IFT-A和IFT-B分别在不存在IFT-B和IFT-A的情况下也能被招募到母中心粒，并且动力蛋白-2的招募与IFT-A和IFT-B无关。扩展显微镜显示，基体处的IFT-A/IFT-B库与TZ处的不同。我们得出结论，在IFT列车组装之前，IFT-A和IFT-B以相互独立且与纤毛发生无关的方式被招募到母中心粒。
