Zhou Qing, Hu Huiqing, Li Ziyin
Department of Microbiology and Molecular Genetics, MGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
mBio. 2025 Jul 9;16(7):e0037125. doi: 10.1128/mbio.00371-25. Epub 2025 May 30.
The flagellum in plays crucial roles in cell locomotion, cell morphogenesis, and cell division, and its inheritance depends on the faithful duplication of multiple flagellum-associated structures. One of such cytoskeletal structures is a hairpin-like structure termed the hook complex, composed of a fishhook-like structure and a centrin arm structure, whose cellular functions remain poorly understood. We recently identified KIN-G, an orphan kinesin that promotes hook complex and Golgi biogenesis. Here we report a WD40 repeat-containing protein named 40 epeat-containing protein (WDR2), which interacts with and regulates KIN-G. WDR2 co-localizes with KIN-G at the centrin arm, and knockdown of WDR2 disrupts hook complex integrity and morphology, inhibits flagellum attachment zone elongation and flagellum positioning, and arrests cytokinesis. Knockdown of WDR2 also disrupts the maturation of the centrin arm-associated Golgi apparatus, thereby impairing Golgi biogenesis. WDR2 interacts with KIN-G via the N-terminal domain of unknown function, the middle domain containing a coiled-coil motif and a PB1 motif, and the C-terminal WD40 domain, and targets KIN-G to its subcellular location. These results uncover a regulatory role for WDR2 in recruiting KIN-G to regulate hook complex and Golgi biogenesis, thereby impacting flagellum inheritance and cell division plane positioning for a symmetrical cytokinesis.IMPORTANCE is a unicellular eukaryotic parasite and the causative agent for sleeping sickness in humans and nagana in cattle in sub-Saharan Africa. This parasite has a motile flagellum, which controls cell morphogenesis and cell division. The flagellum associates, at its proximal region, with a specialized cytoskeletal structure termed the hook complex, which comprises a fishhook-like structure and a bar-shaped structure named the centrin arm. The Golgi apparatus associates with the centrin arm and depends on the latter for biogenesis. We previously discovered an orphan kinesin named KIN-G that plays essential roles in promoting hook complex and Golgi biogenesis. Here we identified a KIN-G-interacting protein named WDR2, which regulates KIN-G localization and stability and promotes hook complex and Golgi biogenesis. These results discovered a new protein complex at the centrin arm and uncovered a mechanistic role of WDR2 in recruiting KIN-G to regulate the biogenesis of the hook complex and the Golgi apparatus, further impacting flagellum inheritance and cell division in this early divergent protozoan parasite.
鞭毛在细胞运动、细胞形态发生和细胞分裂中发挥着关键作用，其遗传依赖于多种鞭毛相关结构的忠实复制。其中一种细胞骨架结构是一种发夹状结构，称为钩复合体，由鱼钩状结构和中心粒臂结构组成，其细胞功能仍知之甚少。我们最近鉴定出KIN-G，一种促进钩复合体和高尔基体生物发生的孤儿驱动蛋白。在此，我们报道一种名为含WD40重复序列蛋白（WDR2）的蛋白，它与KIN-G相互作用并对其进行调节。WDR2与KIN-G在中心粒臂处共定位，敲低WDR2会破坏钩复合体的完整性和形态，抑制鞭毛附着区伸长和鞭毛定位，并使胞质分裂停滞。敲低WDR2还会破坏与中心粒臂相关的高尔基体的成熟，从而损害高尔基体生物发生。WDR2通过功能未知的N端结构域、包含卷曲螺旋基序和PB1基序的中间结构域以及C端WD40结构域与KIN-G相互作用，并将KIN-G靶向其亚细胞定位。这些结果揭示了WDR2在招募KIN-G以调节钩复合体和高尔基体生物发生方面的调节作用，从而影响鞭毛遗传和细胞分裂平面定位以实现对称的胞质分裂。重要性：是一种单细胞真核寄生虫，是撒哈拉以南非洲地区人类昏睡病和牛那加那病的病原体。这种寄生虫有一条能动的鞭毛，它控制细胞形态发生和细胞分裂。鞭毛在其近端区域与一种特殊的细胞骨架结构——钩复合体相关联，钩复合体由鱼钩状结构和一个名为中心粒臂的杆状结构组成。高尔基体与中心粒臂相关联，并依赖于后者进行生物发生。我们之前发现了一种名为KIN-G的孤儿驱动蛋白，它在促进钩复合体和高尔基体生物发生中起重要作用。在此，我们鉴定出一种与KIN-G相互作用的蛋白WDR2，它调节KIN-G的定位和稳定性，并促进钩复合体和高尔基体生物发生。这些结果在中心粒臂处发现了一种新的蛋白复合体，并揭示了WDR2在招募KIN-G以调节钩复合体和高尔基体生物发生方面的机制作用，进一步影响了这种早期分化的原生动物寄生虫的鞭毛遗传和细胞分裂。
