Mechanisms of the unusual cytokinesis in trypanosomes

布鲁氏锥虫的胞质分裂，一种寄生的原生动物，人类睡眠的病原体 疾病是从新的鞭毛附着区(FAZ)丝的前端开始的。胞质分裂 卵裂沟沿纵轴从前向后单向嵌入 细胞的末端，没有肌动球蛋白收缩环的参与，这是在布氏锥虫之后出现的 与上一个真核生物的共同祖先背道而驰。布鲁氏毛滴虫的胞质分裂是完全不同的 因此是一个很有希望的药物靶点。据认为，胞质分裂 布氏毛滴虫的调控途径不同于大多数真核生物，布氏毛滴虫的卵裂沟 涉及到新的组件。然而，对胞质分裂调控途径和细胞分裂调控途径知之甚少。 因此，很大程度上阻碍了我们对棉铃虫致病机理的理解。 这种可怕的人类病原体的胞质分裂。目前的建议建立在最近发现的胞质分裂信号级联的基础上，旨在解决以下问题。(1)。布氏毛滴虫不同生活史中的胞质分裂信号通路是什么？我们推测，多种调节因子，包括进化上保守的蛋白激酶和激动素特异性调节因子，在新的FAZ细丝的前端协同调节胞质分裂的启动，并在卵裂沟促进分裂沟的进入。我们的重点是机械学上的 两种新蛋白CIF3和CIF4在胞质分裂中的作用及其与已知 胞质分裂调节剂在昆虫和血液中发挥其生物学功能。(2)。何谓 蛋白质磷酸化和去磷酸化在细胞质分裂中的生理作用？参与其中的 胞质分裂中的两种蛋白激酶TbPLK和TbAUK1提示胞质分裂的广泛磷酸化 监管者受这两个因素的影响。重要的是，我们鉴定了一种动质体特异性蛋白磷酸酶，名为 KPP1(激动素特异性蛋白磷酸酶1)，似乎拮抗TbPLK。我们建议 研究TbPLK和TbAUK1对CIF1和CIF2磷酸化的生理作用以及TbAUK1对CIF1和CIF2的调节作用 KPP1对胞质分裂的贡献。(3)。是什么驱动了卵裂沟的内向，其组成部分是什么？ 乳沟的位置吗？我们鉴定了一种新的蛋白质，它包含一个运动蛋白结构域和两个 原肌球蛋白结构域，并在胞质分裂过程中定位于卵裂沟。因此，我们假设T. Brucei采用了一种新的基于原肌球蛋白的收缩机械来进行沟槽内进和正末端定向收缩 动蛋白马达驱动从细胞前端(减端)的单向沟槽内移 微管)朝向后细胞端(加上微管的末端)。我的实验室的长期目标是描绘控制布氏毛滴虫胞质分裂的调控途径，并探索在不同生命周期形式中不同细胞周期控制的机制。这些研究将有助于我们从根本上理解胞质分裂的分子基础，而不同于通常认为的通过肌动球蛋白收缩环作用的细胞分裂机制。这些研究结果不仅将具有重要的生物学意义，而且可能为抗锥虫化疗提供新的靶点。

Cytokinesis in Trypanosoma brucei, a parasitic protozoan and the causative agent of human sleeping sickness, is initiated from the anterior tip of the new flagellum attachment zone (FAZ) filament. The cytokinesis cleavage furrow ingresses uni-directionally along the longitudinal axis from the anterior towards the posterior end of the cell, without the involvement of an actomyosin contractile ring, which appeared after T. brucei diverged from the last eukaryotic common ancestor. Cytokinesis in T. brucei is known to be totally different from that in its human host, and therefore is a promising drug target. It is believed that the cytokinesis regulatory pathway in T. brucei is different from most eukaryotes and that the cleavage furrow in T. brucei involves novel components. However, little is known about the cytokinesis regulatory pathway and the cleavage furrow components in T. brucei, thus significantly hindering our understanding of the mechanisms of cytokinesis in this dreadful human pathogen. The current proposal is built upon the recently discovered cytokinesis signaling cascade, and aims to address the following questions. (1). What are the cytokinesis signaling pathways in different life cycle forms of T. brucei? We hypothesize that multiple regulators, including evolutionarily conserved protein kinases and kinetoplstid-specific regulators, cooperate at the anterior tip of the new FAZ filament to regulate cytokinesis initiation and at the cleavage furrow to promote cleavage furrow ingression. Our focus is on the mechanistic roles of two novel proteins, named CIF3 and CIF4, in cytokinesis and how they cooperate with the known cytokinesis regulators to fulfil their biological function in both the insect and bloodstream forms. (2). What are the physiological roles of protein phosphorylation and dephosphorylation in cytokinesis? The involvement of two protein kinases, TbPLK and TbAUK1, in cytokinesis suggests an extensive phosphorylation of cytokinesis regulators by the two kinases. Importantly, we identified a kinetoplastid-specific protein phosphatase, named KPP1 (Kinetoplstid-specific Protein Phosphatase 1), that appears to antagonize TbPLK. We propose to investigate the physiological roles of CIF1 and CIF2 phosphorylation by TbPLK and TbAUK1 and the contribution of KPP1 to cytokinesis. (3). What drives cleavage furrow ingression and what are the components of the cleavage furrow? We identified a novel protein that contains a kinesin motor domain and two tropomyosin domains and localizes to the cleavage furrow during cytokinesis. We thus hypothesize that T. brucei employs a novel tropomyosin-based contractile machinery for furrow ingression and a plus end-directed kinesin motor to drive the uni-directional furrow ingression from the anterior cell end (minus end of the microtubules) toward the posterior cell end (plus ends of the microtubules). The long-term goal of my laboratory is to delineate the regulatory pathway that controls cytokinesis in T. brucei and explore the mechanisms underlying the distinct cell cycle control in different life cycle forms. These studies will facilitate our fundamental understanding of the molecular basis of cytokinesis that is different from the commonly recognized cell division mechanism through the action of an actomyosin contractile ring. The outcomes from these investigations not only will have important biological significance, but also could provide novel targets for anti-trypanosome chemotherapy.