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.

Public Health Relevance

Human African Trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease causing 300,000 to 500,000 infections each year. Since drugs to cure the disease are few and often toxic to humans, further understanding of the parasite and drug development are urgently needed. The proposed studies in this application will explore the function and regulation of several cytokinesis regulatory proteins that are indispensable for Trypanosoma brucei to survive in its human and insect hosts. These regulatory proteins include a number of trypanosome-specific proteins essential for parasite proliferation and viability. The studies may provide novel targets for chemotherapy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
2R01AI101437-05
Application #
9310309
Study Section
Pathogenic Eukaryotes Study Section (PTHE)
Program Officer
Mcgugan, Glen C
Project Start
2013-06-06
Project End
2022-05-31
Budget Start
2017-06-01
Budget End
2018-05-31
Support Year
5
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Texas Health Science Center Houston
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
800771594
City
Houston
State
TX
Country
United States
Zip Code
77030
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Zhou, Qing; Lee, Kyu Joon; Kurasawa, Yasuhiro et al. (2018) Faithful chromosome segregation in Trypanosoma brucei requires a cohort of divergent spindle-associated proteins with distinct functions. Nucleic Acids Res 46:8216-8231
Kurasawa, Yasuhiro; Hu, Huiqing; Zhou, Qing et al. (2018) The trypanosome-specific protein CIF3 cooperates with the CIF1 protein to promote cytokinesis in Trypanosoma brucei. J Biol Chem 293:10275-10286
An, Tai; Liu, Yi; Gourguechon, Stéphane et al. (2018) CDK Phosphorylation of Translation Initiation Factors Couples Protein Translation with Cell-Cycle Transition. Cell Rep 25:3204-3214.e5
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Hu, Huiqing; Majneri, Paul; Li, Dielan et al. (2017) Functional analyses of the CIF1-CIF2 complex in trypanosomes identify the structural motifs required for cytokinesis. J Cell Sci 130:4108-4119

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