Biology ETDs

Publication Date

Summer 7-15-2019

Abstract

The microbial pathogen Toxoplasma gondii is an intracellular protozoan that actively invades host cells and simultaneously creates a specialized parasitophorous vacuole within which the parasite lives and replicates. The parasite molecular machinery that drives establishment of the intracellular niche is relatively well known. However, it is now emerging that Toxoplasma exploits less well-understood host cell components to enable successful infection. Here, we examined the role of host Wnt/β-catenin during T. gondii infection. Using human fibroblasts and a mouse dendritic cell line, we found that infection with Toxoplasma stimulated both upregulation and nuclear localization of β-catenin. Using a transwell experimental approach, we obtained data indicating that direct contact between parasites and cells is required for increased β-catenin expression. To examine the functional consequences of augmented β-catenin levels, we determined the effect of a panel of Wnt/β-catenin inhibitors on the ability of T. gondii to successfully establish infection. Using both dendritic cells and fibroblasts, we found up to 80% inhibition of infection in the presence of the small molecule inhibitors. Subsequent efforts were directed towards determining whether host β-catenin is required for the invasion event itself, or whether its role is in maintenance of the parasitophorous vacuole in newly invaded cells. Synchronized invasion analysis indicates that β-catenin is likely exploited by the parasite during invasion, but may not be as vital later in infection. Finally, the consequences of enhanced host β-catenin expression were assessed using a panel of small molecule β-catenin enhancers. Drug-augmentation of host cell β-catenin promoted T. gondii infection in human foreskin fibroblasts, and specifically assisted the parasite during invasion. Together, the results from this study suggest that Toxoplasma gondii exploits host cell β-catenin during its active invasion event, and give light to a previously unexplored mechanism for inhibiting T. gondii infection.

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Dr. Eric Y. Denkers

Second Committee Member

Dr. Robert D. Miller

Third Committee Member

Dr. Christopher Johnston

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