The African trypanosome, Trypanosoma brucei, is a protozoan parasite that causes fatal sleeping sickness in humans and related debilitating diseases in animals. Existing treatments for these diseases are outdated, toxic and hard to administer, highlighting the need for research that opens up avenues to identify new therapeutic targets. T. brucei is capable of infecting a diverse range of mammalian hosts and is transmitted by a tsetse fly vector. In order to infect such diverse hosts, T. brucei must be able to perceive host-specific signals and respond to meet the demands presented by each host environment. These functions are largely provided by parasite cell surface proteins that form the host-parasite interface. However, to date, only a handful of T. brucei surface proteins have been identified and characterized, leaving large gaps in our understanding of host-pathogen interactions. The single flagellum of T. brucei is important for motility and is postulated to provide important signaling functions, as has been demonstrated for flagella in other eukaryotes. The flagellar membrane is proposed to be a key host-parasite interface that interacts directly with host tissues and directs signaling events important for infection and pathogenesis. By developing a novel strategy for isolation of intact membrane-enclosed flagella, combined with surface biotinylation and shotgun proteomics, we have conducted the first proteomic analysis of the flagellar membrane from bloodstream form T. brucei. Preliminary analysis of the flagellum from procyclic form parasites identified different adenylate cyclases in each life cycle stage. The function of ACs is unknown, but they are suggested to function in signaling events important for host infection. We will test the hypothesis that ACs upregulated in bloodstream form parasites mediate host-parasite interactions that affect the outcome of mammalian infection and pathogenesis. Additionally, since the flagellum is an important site of signaling and host-pathogen interaction, we will define mechanisms for targeting these receptor proteins to the flagellar membrane. Together, the proposed experiments will increase understanding of the role of trypanosome surface proteins during infection and advance efforts to understand and exploit the flagellum as a key host-parasite interface.

Public Health Relevance

Millions of people worldwide suffer from parasitic diseases, however parasitic infections remain understudied and less well-understood than bacterial and viral infections. African trypanosomes are devastating pathogens that cause significant mortality in humans and a variety of animal hosts, but the parasite cell surface proteins that make up the host-parasite interface and allow adaptation to different hosts are largely unknown. Studying Trypanosoma brucei cell surface proteins that are important for mammalian infection and pathogenesis will uncover fundamental concepts of trypanosome biology and may reveal new therapeutic targets.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Postdoctoral Individual National Research Service Award (F32)
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Special Emphasis Panel (ZRG1)
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Wali, Tonu M
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University of California Los Angeles
Schools of Medicine
Los Angeles
United States
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Langousis, Gerasimos; Shimogawa, Michelle M; Saada, Edwin A et al. (2016) Loss of the BBSome perturbs endocytic trafficking and disrupts virulence of Trypanosoma brucei. Proc Natl Acad Sci U S A 113:632-7
Shimogawa, Michelle M; Saada, Edwin A; Vashisht, Ajay A et al. (2015) Cell Surface Proteomics Provides Insight into Stage-Specific Remodeling of the Host-Parasite Interface in Trypanosoma brucei. Mol Cell Proteomics 14:1977-88
Saada, Edwin A; Kabututu, Z Pius; Lopez, Miguel et al. (2014) Insect stage-specific receptor adenylate cyclases are localized to distinct subdomains of the Trypanosoma brucei Flagellar membrane. Eukaryot Cell 13:1064-76