Browsing by Author "Krueger, Amanda"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Elucidating the Role of the Essential Kinase TgGSK in the Human Parasite Toxoplasma Gondii
    (2025-02) Krueger, Amanda; Yeh, Elizabeth; Arrizabalaga, Gustavo; Sullivan, William; Nass, Richard; Aoki, Scott
    Toxoplasma gondii is an intracellular parasite that infects nearly a third of the world’s human population. While infection is largely asymptomatic in an immunocompetent host, Toxoplasma infection in immunocompromised or immunosuppressed individuals can lead to toxoplasmosis, which can include brain lesions and lead to death. Similarly, toxoplasmosis can result in birth defects, brain swelling, and blindness of a developing fetus in the case of a congenital infection. With minimal treatments for toxoplasmosis available, it is crucial to study parasite-specific processes that could be potential drug targets for the treatment of toxoplasmosis. Toxoplasma gondii divides through a unique process known as endodyogeny, where two daughter parasites are formed within a mother. In this study, we investigated a novel protein called TgGSK that is crucial for proper parasite division. Experiments reveal that TgGSK changes its localization within the parasite dependent on the stage of division. Knockdown of TgGSK causes abnormal division phenotypes and causes Toxoplasma to be unable to complete its propagation cycle. We determined through microscopy and phosphoproteomics that TgGSK may play its role in parasite division through an interaction with the centrosome, an organelle which is a main feature of cell division in many organisms. Our findings suggest that TgGSK also regulates messenger RNA processing. Finally, our study suggests that TgGSK is regulated and stabilized through acetylation from the GCN5b lysine acetyltransferase complex. Taken together, we have performed an in-depth study of the functional role of the essential protein TgGSK in Toxoplasma gondii. This and future studies have potential to demonstrate that TgGSK is a parasite-specific drug target for the therapeutic treatment of toxoplasmosis.
  • Thumbnail Image
    Item
    The essential kinase TgGSK regulates centrosome division and endodyogeny in Toxoplasma gondii
    (bioRxiv, 2024-09-27) Krueger, Amanda; Horjales, Sofia; Yang, Chunlin; Blakely, William J.; Francia, Maria E.; Arrizabalaga, Gustavo; Pharmacology and Toxicology, School of Medicine
    Intracellular replication is crucial for the success of apicomplexan parasites, including Toxoplasma gondii. Therefore, essential players in parasite replication present potential targets for drug development. In this study, we have characterized TgGSK, a glycogen synthase kinase homolog that plays an important role in Toxoplasma endodyogeny. We have shown that TgGSK has a dynamic localization that is concurrent with the cell cycle. In non-dividing parasites, this kinase is highly concentrated in the nucleus. However, during division, TgGSK displays a cytosolic localization, with concentration foci at the centrosomes, a key organelle involved in parasite division, and the basal end. Conditional knockdown of TgGSK determined that it is essential for the completion of the lytic cycle and proper parasite division. Parasites lacking endogenous protein levels of TgGSK exhibited defects in division synchronicity and the segregation of the nucleus and apicoplast into forming daughter cells. These phenotypes are associated with defects in centrosome duplication and fission. Global phosphoproteomic analysis determined TgGSK-dependent phosphorylation of RNA-processing, basal end, and centrosome proteins. Consistent with the putative regulation of RNA-processing proteins, global transcriptomic analysis suggests that TgGSK is needed for proper splicing. Finally, we show that TgGSK interacts with GCN5b, a well-characterized acetyltransferase with roles in transcriptional control. Conversely, GCN5b chemical inhibition results in specific degradation of TgGSK. Thus, these studies reveal the involvement of TgGSK in various crucial processes, including endodyogeny and splicing, and identify acetylation as a possible mechanism by which this essential kinase is regulated.