Characterization and Functional Analysis of Golgi-associated Proteins Identified by Proximity Labeling

Importance: Apicomplexan parasites such as infect a large percentage of the world's population and cause substantial human disease. These widespread pathogens use specialized secretory organelles to infect their host cells, modulate host cell functions, and cause disease. While the functions of the secretory organelles are now better understood, the Golgi apparatus of the parasite remains largely unexplored, particularly regarding parasite-specific innovations that may help direct traffic intracellularly. In this work, we characterize ULP1, a protein that is unique to parasites but shares structural similarity to the eukaryotic trafficking factor p115/Uso1. We show that ULP1 plays an important role in parasite fitness and demonstrate that it interacts with the conserved oligomeric Golgi (COG) complex. We then use ULP1 proximity labeling to identify 11 additional Golgi-associated proteins, which we functionally analyze via conditional knockdown. This work expands our knowledge of the Golgi apparatus and identifies potential targets for therapeutic intervention.