The broad goal of this proposal is to understand basic processes of secretory protein transport in African trypanosomes, with special regard to glycosylphosphatidylinositol (GPI) membrane anchors. These processes have been traditionally studied in yeast and mammals, but the availability of sophisticated genetic strategies in Trypanosoma brucei provides a potent alternative system to study eukaryotic secretory cell biology. Importantly, two features make African trypanosomes especially relevant for study. First, trypanosomes are high impact human and veterinary pathogens in sub-Saharan Africa. The WHO estimates that >60 million people in 36 countries are at risk of acquiring Human African Trypanosomiasis (HAT). Few drugs are available, the best of which (eflornithine) is expensive and requires a difficult regimen, the worst of which (melarsoprol) kills up to 10% of recipients. Infection is always fatal without intervention, vaccination is not an option, and there is a critical need for new therapies. Second, the ancient phylogenetic status of trypanosomes, and their unique secretory architecture, ensure that novel results relative to the `standard' eukaryotic model systems will be obtained. The lynchpins of pathogenesis in trypanosomiasis are the GPI- anchored variant surface glycoprotein (VSG), and related transferrin receptor (TfR), of the bloodstream stage of the life cycle. Understanding how they are transported to the cell surface, and the role of GPIs in this trafficking, are critical to understanding the parasite half of the host-parasite relationship. This proposal is designed to investigate these processes.
The Specific Aims all derive directly from progress from the previous funding period. First, we have identified a gene family of p24 membrane proteins as putative loading receptors for exit of secretory cargo, including VSG, from the ER (Aim #1). Second, we have demonstrated that non- functional GPI-anchored proteins are monitored and degraded by the ERAD (ER-Associated Degradation) pathway (Aim #2). Third, we have developed a strategy for in situ modification of the TfR heterodimer subunits (ESAG6/ESAG7) that allows us to test the hypothesis that GPI valence regulates progression/stability of proteins within post-Golgi pathways (Aim #3). These results will drive deeper investigations of secretory trafficking in trypanosomes to illuminate critical aspects of basic trypanosome cell biology. It is our belief that this work may help lay the foundation for future drug development, and will highlight not just the differences, but also the similarities of cell biological processes common to the full range of eukaryotic evolution.

Public Health Relevance

African trypanosomes are parasitic protozoa that cause human African trypanosomiasis (HAT, sleeping sickness), as well as nagana in cattle and other livestock. Current drugs are toxic and vaccination is not an option, consequently new prevention strategies are needed. The major variant surface glycoprotein and transferrin receptor are critical for parasite viability and pathogenesis, and studies of these proteins will provide a basic foundation for cell biological approaches to parasite control.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI035739-25
Application #
9936419
Study Section
Pathogenic Eukaryotes Study Section (PTHE)
Program Officer
Mcgugan, Glen C
Project Start
1994-12-01
Project End
2021-05-31
Budget Start
2020-06-01
Budget End
2021-05-31
Support Year
25
Fiscal Year
2020
Total Cost
Indirect Cost
Name
State University of New York at Buffalo
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
038633251
City
Amherst
State
NY
Country
United States
Zip Code
14228
Tiengwe, Calvin; Koeller, Carolina M; Bangs, James D (2018) Endoplasmic reticulum-associated degradation and disposal of misfolded GPI-anchored proteins in Trypanosoma brucei. Mol Biol Cell 29:2397-2409
Kruzel, Emilia K; Zimmett 3rd, George P; Bangs, James D (2017) Life Stage-Specific Cargo Receptors Facilitate Glycosylphosphatidylinositol-Anchored Surface Coat Protein Transport in Trypanosoma brucei. mSphere 2:
Tiengwe, Calvin; Bush, Peter J; Bangs, James D (2017) Controlling transferrin receptor trafficking with GPI-valence in bloodstream stage African trypanosomes. PLoS Pathog 13:e1006366
Tiengwe, Calvin; Muratore, Katherine A; Bangs, James D (2016) Surface proteins, ERAD and antigenic variation in Trypanosoma brucei. Cell Microbiol 18:1673-1688
Biéler, Sylvain; Waltenberger, Harald; Barrett, Michael P et al. (2016) Evaluation of Antigens for Development of a Serological Test for Human African Trypanosomiasis. PLoS One 11:e0168074
Aksoy, Emre; Vigneron, Aurélien; Bing, XiaoLi et al. (2016) Mammalian African trypanosome VSG coat enhances tsetse's vector competence. Proc Natl Acad Sci U S A 113:6961-6
Tiengwe, Calvin; Brown, Abigail E N A; Bangs, James D (2015) Unfolded Protein Response Pathways in Bloodstream-Form Trypanosoma brucei? Eukaryot Cell 14:1094-101
Jelk, Jennifer; Gao, Ningguo; Serricchio, Mauro et al. (2013) Glycoprotein biosynthesis in a eukaryote lacking the membrane protein Rft1. J Biol Chem 288:20616-23
Liu, Li; Xu, Yu-Xin; Caradonna, Kacey L et al. (2013) Inhibition of nucleotide sugar transport in Trypanosoma brucei alters surface glycosylation. J Biol Chem 288:10599-615
Schwartz, Kevin J; Peck, Ronald F; Bangs, James D (2013) Intracellular trafficking and glycobiology of TbPDI2, a stage-specific protein disulfide isomerase in Trypanosoma brucei. Eukaryot Cell 12:132-41

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