Deciphering the molecular rules of evolutionary diversification of Intraflagellar Transport

破译鞭毛内运输进化多样化的分子规则

• 批准号: 520475795
• 负责人: Dr. Zeynep Ökten
• 金额: --
• 依托单位: Lehrstuhl für Molekulare Biophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/520475795?language=en
• 关键词: Deciphering; molecular; rules; evolutionary; diversification

Cilia (aka flagella) are ubiquitous organelles that project from the surface of most eukaryotic cells, including the cell types in the human body. Virtually all cilia require the non-membrane bound IntraFlagellar Transport (IFT) for their construction and function. IFT is a continuous transport of ciliary building blocks by the so-called IFT trains that are powered by the kinesin-2 and dynein-2 motors. A hallmark of IFT is the site-specific and mutually exclusive activation and deactivation of the two oppositely directed motors at the ciliary base and tip. It is becoming increasingly clear that a hierarchical assembly of the IFT trains enforces the strictly ordered events of the IFT process. At the ciliary base, large multi mega-Dalton IFT trains are assembled starting with the IFT-B complex. This IFT-B complex constitutes the backbone that scaffolds the IFT-A complex and the dynein-2 motor. In the last step of the assembly, the kinesin-2 motor is recruited to move the trains towards the ciliary tip. Whereas IFT-B and IFT-A complexes have been linked to the kinesin-2 and dynein-2 activities in vivo, their specific contributions to the regulation of IFT motors remain largely unknown at the molecular level. It also became clear that the composition of the respective IFT-B and IFT-A complexes are species-specific and highly diverse. The latter provokes the question of how the various organisms deploy the respective IFT subunits to orchestrate the orderly steps of the IFT process in vivo. Here, we investigate and contrast IFT of the Chromalveolates T. thermophila and T. pseudonana. Despite being members of the same evolutionary super group, these organisms deploy an astonishingly different set of IFT subunits and kinesin-2 motors, yet end up building essentially the same cellular ultrastructure, a motile cilium. T. pseudonana model is of particular interest as it has eliminated most IFT subunits but retained the ability to orchestrate the IFT process using only a subset of subunits from the IFT-B complex. This ‘minimal’ IFT model will likely teach us the limits of functional flexibility that can be coded into a specific set of proteins to create complex biological function. As already evident from our preliminary data, the kinesin-2 orthologs from the ‘minimal’ T. pseudonana and ‘canonical’ T. thermophila models display vastly different self-regulatory and kinetic properties. Yet all kinesin-2 motors are expected to obey the rules of the highly orderly steps of IFT. Delineating the molecular requirements of these key steps will expose the rules of linking the motors to specific IFT subunits that ultimately give rise to the strict chronology of events during the IFT process in the ‘minimal’ T. pseudonana and ‘canonical’ T. thermophila models, respectively. This proposal will bring us closer to derive the rules of establishing an orderly IFT process in a given organism based on the set of IFT subunits and the type(s) of kinesin-2 that it deploys.

纤毛（又名鞭毛）是普遍存在的细胞器，从大多数真核细胞的表面伸出，包括人体中的细胞类型。事实上，所有纤毛都需要非膜结合的鞭毛内转运（IFT）来实现其结构和功能。IFT是通过由驱动蛋白-2和动力蛋白-2马达提供动力的所谓IFT序列连续运输纤毛构件。IFT的一个标志是在睫状体基部和尖端的两个相反方向的马达的位点特异性和互斥的激活和失活。越来越清楚的是，IFT序列的分层组装强制执行IFT过程的严格有序事件。在睫状体基部，从IFT-B复合物开始组装大型多兆道尔顿IFT序列。该IFT-B复合物构成支撑IFT-A复合物和动力蛋白-2马达的骨架。在组装的最后一步中，驱动蛋白-2马达被募集以使序列朝向睫状体尖端移动。尽管IFT-B和IFT-A复合物已与体内驱动蛋白-2和动力蛋白-2的活性相关，但它们对IFT马达调节的具体贡献在分子水平上仍然很大程度上未知。还清楚地表明，IFT-B和IFT-A复合物的组成具有物种特异性和高度多样性。后者引发了一个问题，即各种生物体如何部署各自的IFT亚基来协调体内IFT过程的有序步骤。本文研究和对比了Chromalveolates T. thermophila和T.假阿纳。尽管是同一进化超级群体的成员，但这些生物体部署了一组截然不同的IFT亚基和驱动蛋白-2马达，但最终构建了基本相同的细胞超微结构，即能动的纤毛。T. Bifana模型特别令人感兴趣，因为它消除了大多数IFT子单元，但保留了仅使用来自IFT-B复合体的子单元子集来编排IFT过程的能力。这种“最小”IFT模型可能会告诉我们功能灵活性的极限，这些功能灵活性可以编码到一组特定的蛋白质中，以创造复杂的生物功能。从我们的初步数据中已经可以看出，来自“最小”T. Anchorana和'canonical' T.嗜热菌模型显示出截然不同的自我调节和动力学特性。然而，所有的驱动蛋白-2马达都应该遵守IFT高度有序的步骤规则。描述这些关键步骤的分子要求将揭示将马达连接到特定IFT亚基的规则，这些亚基最终在“最小”T中的IFT过程中产生严格的事件年表。Anchorana和'canonical' T. thermophila模式，分别。该提案将使我们更接近于根据IFT亚基集和其部署的驱动蛋白-2的类型推导出在给定生物体中建立有序IFT过程的规则。