Zhou Qing, Kurasawa Yasuhiro, Hu Huiqing, Souza Onofre Thiago, Li Ziyin
Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
mBio. 2024 Dec 11;15(12):e0263424. doi: 10.1128/mbio.02634-24. Epub 2024 Oct 30.
Kinesins are microtubule-based motor proteins that play diverse cellular functions by regulating microtubule dynamics and intracellular transport in eukaryotes. The early branching kinetoplastid protozoan has an expanded repertoire of kinetoplastid-specific kinesins and orphan kinesins, many of which have unknown functions. We report here the identification of an orphan kinesin named KIN-G that plays an essential role in maintaining hook complex integrity and promoting Golgi biogenesis in . KIN-G localizes to the distal portion of the centrin arm of the flagellum-associated hook complex through association with the centrin arm protein TbCentrin4. Knockdown of KIN-G in disrupts the integrity of the hook complex by reducing the length of the centrin arm and eliminating the shank part of the hook complex, thereby impairing flagellum attachment zone elongation and flagellum positioning, which leads to unequal cytokinesis. KIN-G associates with Golgi through a centrin arm-localized Golgi peripheral protein named CAAP1, which maintains Golgi-centrin arm association to facilitate Golgi biogenesis. Knockdown of KIN-G impairs Golgi biogenesis by disrupting CAAP1 at the centrin arm, thereby impairing the maturation of centrin arm-associated Golgi. microtubule gliding assays demonstrate that KIN-G is a plus end-directed motor protein, and its motor activity is required for hook complex assembly and Golgi biogenesis. Together, these results identify a kinesin motor protein for promoting hook complex assembly and uncover a control mechanism for Golgi biogenesis through KIN-G-mediated maintenance of Golgi-hook complex association.IMPORTANCE has a motile flagellum, which controls cell motility, cell morphogenesis, cell division, and cell-cell communication, and a set of cytoskeletal structures, including the hook complex and the centrin arm, associates with the flagellum. Despite the essentiality of these flagellum-associated cytoskeletal structures, their mechanistic roles and the function of their associated proteins remain poorly understood. Here, we demonstrate that the orphan kinesin KIN-G functions to promote the biogenesis of the hook complex and the Golgi apparatus. KIN-G exerts this function by mediating the association between centrin arm and Golgi through the centrin arm protein TbCentrin4 and a novel Golgi scaffold protein named CAAP1, thereby bridging the two structures and maintaining their close association to facilitate the assembly of the two structures. These findings uncover the essential involvement of a kinesin motor protein in regulating the biogenesis of the hook complex and the Golgi in trypanosomes.
驱动蛋白是基于微管的运动蛋白，通过调节真核生物中的微管动力学和细胞内运输发挥多种细胞功能。早期分支的动基体原生动物拥有大量动基体特异性驱动蛋白和孤儿驱动蛋白，其中许多功能未知。我们在此报告鉴定出一种名为KIN-G的孤儿驱动蛋白，它在维持钩复合体完整性和促进动基体生物发生中起关键作用。KIN-G通过与中心粒臂蛋白TbCentrin4结合，定位于鞭毛相关钩复合体中心粒臂的远端部分。在动基体中敲低KIN-G会破坏钩复合体的完整性，减少中心粒臂的长度并消除钩复合体的柄部，从而损害鞭毛附着区的伸长和鞭毛定位，导致不均等胞质分裂。KIN-G通过一种名为CAAP1的定位于中心粒臂的高尔基体周边蛋白与高尔基体结合，该蛋白维持高尔基体与中心粒臂的关联以促进高尔基体生物发生。敲低KIN-G会通过破坏中心粒臂处的CAAP1来损害高尔基体生物发生，从而损害与中心粒臂相关的高尔基体的成熟。微管滑动试验表明KIN-G是一种正端定向运动蛋白，其运动活性是钩复合体组装和高尔基体生物发生所必需的。总之，这些结果鉴定出一种促进钩复合体组装的驱动蛋白运动蛋白，并揭示了通过KIN-G介导的高尔基体-钩复合体关联来控制高尔基体生物发生的机制。重要性：动基体有一条能动的鞭毛，控制细胞运动、细胞形态发生、细胞分裂和细胞间通讯，还有一组细胞骨架结构，包括钩复合体和中心粒臂，与鞭毛相关。尽管这些与鞭毛相关的细胞骨架结构至关重要，但其机制作用及其相关蛋白的功能仍知之甚少。在此，我们证明孤儿驱动蛋白KIN-G的功能是促进钩复合体和高尔基体的生物发生。KIN-G通过中心粒臂蛋白TbCentrin4和一种名为CAAP1的新型高尔基体支架蛋白介导中心粒臂与高尔基体之间的关联来发挥此功能，从而连接这两个结构并维持它们的紧密关联以促进这两个结构的组装。这些发现揭示了一种驱动蛋白运动蛋白在调节锥虫中钩复合体和高尔基体生物发生中的重要作用。
