The human parasite Trypanosoma brucei transitions from the trypomastigote form to the epimastigote form in the insect vector by repositioning its mitochondrial genome and flagellum-associated cytoskeleton. The molecular mechanisms underlying such changes in cell morphology remain elusive, but recent works demonstrated the involvement of three flagellar proteins, FLAM3, ClpGM6 and KIN-E, in this process by controlling the elongation of the flagellum attachment zone (FAZ). In this report, we identified a FAZ flagellum domain-localizing protein named FAZ27 and characterized its role in cell morphogenesis. Depletion of FAZ27 in the trypomastigote form caused major morphological changes and repositioning of the mitochondrial genome and flagellum-associated cytoskeleton, generating epimastigote-like cells. Furthermore, proximity biotinylation and co-immunoprecipitation identified FLAM3 and ClpGM6 as FAZ27-interacting proteins, and analyses of their functional interplay revealed an interdependency for assembly into the FAZ flagellum domain. Finally, we showed that assembly of FAZ27 occurred proximally, identical to the assembly pattern of other FAZ sub-domain proteins. Taken together, these results demonstrate a crucial role for the FAZ flagellum domain in controlling cell morphogenesis and suggest a coordinated assembly of all the FAZ sub-domains at the proximal end of the FAZ.

人类寄生虫布氏锥虫通过重新定位其线粒体基因组和鞭毛相关细胞骨架，在昆虫载体中从锥鞭毛体形式转变为上鞭毛体形式。这种细胞形态变化背后的分子机制仍然难以捉摸，但最近的研究表明，三种鞭毛蛋白 FLAM3、ClpGM6 和 KIN-E 通过控制鞭毛附着区 (FAZ) 的伸长参与了这一过程。在本报告中，我们鉴定了一种名为 FAZ27 的 FAZ 鞭毛结构域定位蛋白，并表征了其在细胞形态发生中的作用。锥鞭毛体形式的 FAZ27 缺失导致重大形态变化以及线粒体基因组和鞭毛相关细胞骨架的重新定位，从而产生表鞭毛体样细胞。此外，邻近生物素化和免疫共沉淀将 FLAM3 和 ClpGM6 鉴定为 FAZ27 相互作用蛋白，对其功能相互作用的分析揭示了组装到 FAZ 鞭毛结构域中的相互依赖性。最后，我们表明 FAZ27 的组装发生在近端，与其他 FAZ 子结构域蛋白的组装模式相同。综上所述，这些结果证明了 FAZ 鞭毛结构域在控制细胞形态发生中的关键作用，并表明所有 FAZ 子结构域在 FAZ 近端的协调组装。