Date of Award

May 2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Genetics and Biochemistry

Committee Member

Meredith T Morris

Committee Member

Lesly Temesvari

Committee Member

Lukasz Kozubowski

Committee Member

Cheryl Ingram-Smith

Abstract

Trypanosoma brucei is the protozoan parasite responsible for Human African Trypanosomiasis (HAT) and the cattle wasting disease Nagana endemic to sub-Saharan Africa. T. brucei and other kinetoplastids possess specialized peroxisomes called glycosomes that compartmentalize many processes including glycolysis and gluconeogesis. While most studies on T. brucei has been performed on lab-adapted 29-13 strain parasites, it has been observed that glucose is an important signaling cue for differentiation of AnTat1.1 cells. Currently, most parasites are maintained in the glucose-rich medium SDM-79, and studies using low glucose media have used either SDM-80 or SDM-79 in which glucose has been depleted by cell culture. Both of these solutions pose a problem by confounding the effect of glucose alone. Here, I present differences in cell morphology, gene expression and glycosome composition between SDM-79 and SDM-79θ as well as between strains. These results show that strain variation and culture conditions are important considerations in the study of T. brucei. Because all glycosomal matrix proteins are imported post-translationally and translocated into the organelle matrix by the docking and translocation module (DTM) comprised primarily of Pex13 and Pex14. Unique to kinetoplastids is the presence of two highly different (<20% similarity) Pex13s, Pex13.1 and Pex13.2. Here, I analyze the role of TbPex13.2 in the import process. We found that knockdown of TbPex13.2 under our conditions did not lead to a growth defect, however, it did result in mislocalization of PTS2 harboring proteins, suggesting a role in the PTS2 import pathway. Additionally, I examine the organization of the unique docking complex. Because kinetoplastids have two Pex13s, the organization of the docking and transport module (DTM) and specific function of each Pex13 unclear. I provide evidence that TbPex13.1 and TbPex13.2 are present in the same organelles and directly interact. Because glycosomes are essential organelles, understanding mechanisms for their biogenesis and protein import are crucial for better targeting the organelles for treatment of disease caused by kinetoplastid parasites.

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