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  • Oral presentation
  • T61

Stuck Together: Investigating Interorganellar Communication in Toxoplasma gondii

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Goethe-Saal & Galerie

Session

Session IX: Cell Biology II

Topic

  • Cell Biology

Authors

Kaelynn Parker (Athens, GA / US), Dr. Diego Huet (Athens, GA / US)

Abstract

In conventional model organisms, it has been shown that organellar interactions are essential for metabolite and lipid exchange, organelle dynamics, cellular homeostasis, and cell fate. While organelles allow for specialized biochemical processes to occur, this necessitates communication between organelles to share signals and metabolites. Originally, it was thought this occurred simply through cytoplasmic diffusion or vesicular trafficking before recent work highlighted the importance of direct contact between organelles. These interactions are supported by areas of close proximity between the two organelles, maintained by protein tethers, and referred to as membrane contact sites. Currently, the majority of our knowledge on membrane contact sites is limited to yeast and mammals, which are part of the Opisthokont clade. Thanks to its genetic amenability, Toxoplasma gondii provides the unique opportunity to investigate membrane contact sites in a divergent model eukaryote. Additionally, T. gondii possesses a phylum-specific organelle, the apicoplast, which has long been observed in close proximity to the mitochondrion. The two organelles have co-evolved in Apicomplexans, resulting in shared biosynthetic and biochemical pathways. We hypothesize that phylum-specific contacts mediate the proximity of these organelles and promote the exchange of materials. To identify membrane contact site candidates in T. gondii, we have taken an unbiased proximity biotinylation-based approach by generating localization handles to anchor a biotin ligase to the surface of the apicoplast, mitochondrion, and also the ER. Preliminary biotinylation experiments followed by mass spectrometry analysis uncovered membrane contact site protein candidates. Our results include several proteins with expected membrane contact site functions, such as lipid-transfer proteins and small GTPases. We also found apicomplexan-specific proteins with no predictable functions or domains that may serve as potential drug targets. Finally, we will also use our data to generate surface proteomes for the ER, mitochondrion, and apicoplast. The results of this work will both expand our knowledge of membrane contact sites across the evolutionary tree, potentially uncover apicomplexan-specific ones, and provide an additional protein localization resource for the community.

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