Trypanosome Cell Biology Unit, Institut Pasteur, Université de Paris Cité, INSERM U1201, Paris, France.
Sorbonne Université, école doctorale complexité du vivant, ED 515, 7, quai Saint-Bernard, case 32, 75252 Paris Cedex 05, France.
Mol Biol Cell. 2024 Aug 1;35(8):ar106. doi: 10.1091/mbc.E23-11-0425. Epub 2024 Jun 12.
Outer dynein arms (ODAs) are responsible for ciliary beating in eukaryotes. They are assembled in the cytoplasm and shipped by intraflagellar transport (IFT) before attachment to microtubule doublets via the docking complex. The LRRC56 protein has been proposed to contribute to ODAs maturation. Mutations or deletion of the gene lead to reduced ciliary motility in all species investigated so far, but with variable impact on dynein arm presence. Here, we investigated the role of LRRC56 in the protist where its absence results in distal loss of ODAs, mostly in growing flagella. We show that LRRC56 is a transient cargo of IFT trains during flagellum construction and surprisingly, is required for efficient attachment of a subset of docking complex proteins present in the distal portion of the organelle. This relation is interdependent since the knockdown of the distal docking complex prevents LRRC56's association with the flagellum. Intriguingly, cells display shorter flagella whose maturation is delayed. Inhibition of cell division compensates for the distal ODAs absence thanks to the redistribution of the proximal docking complex, restoring ODAs attachment but not the flagellum length phenotype. This work reveals an unexpected connection between LRRC56 and the docking complex.
外动力蛋白臂（ODAs）负责真核生物纤毛的摆动。它们在细胞质中组装，并通过鞭毛内运输（IFT）运输，然后通过对接复合物附着到微管 doublets 上。LRRC56 蛋白被认为有助于 ODAs 的成熟。到目前为止，在所有研究过的物种中，基因的突变或缺失都会导致纤毛运动减少，但对动力蛋白臂的存在的影响不同。在这里，我们研究了 LRRC56 在原生动物中的作用，其缺失会导致 ODAs 的远端缺失，主要是在生长的鞭毛中。我们表明，LRRC56 是鞭毛构建过程中 IFT 列车的瞬时货物，令人惊讶的是，它对于有效附着存在于细胞器远端的一部分对接复合物蛋白是必需的。这种关系是相互依存的，因为远端对接复合物的敲低会阻止 LRRC56 与鞭毛的结合。有趣的是，细胞显示出较短的鞭毛，其成熟被延迟。细胞分裂的抑制通过近端对接复合物的重新分布来补偿远端 ODAs 的缺失，恢复了 ODAs 的附着，但不能恢复鞭毛长度表型。这项工作揭示了 LRRC56 和对接复合物之间的意外联系。
