Systematic Identification of the Lysine lactylation in the Protozoan Parasite Toxoplasma gondii

Lysine lactylation (Kla) is a new posttranslational modification (PTM) identified in histone and nonhistone proteins of several eukaryotic cells that directly activate gene expression and DNA replication. However, very little is known about their scope and cellular distribution in apicomplexan parasites that are important to public and animal health. Toxoplasma gondii, the agent of toxoplasmosis, is one of obligate intracellular apicomplexan parasite that can infect all kinds of nucleated cells of animals and humans. Using this parasite as model organism, herein, we produced the first global lysine lactylome profile through LC-MS/MS. Overall, a total of 983 Kla sites occurred on 523 lactylated proteins were identified in Toxoplasma tachyzoites, the acute toxoplasmosis-causing stage. Bioinformatics analysis revealed that these lactylated proteins are evolutionarily conserved and involved in a wide variety of cellular functions such as energy metabolism, gene regulation and protein biosynthesis. Moreover, the results from subcellular localization analysis and IFA showed that the majority of lactylated T. gondii proteins localized in the nucleus, indicating a potential impact of Kla on gene regulation. Notably, an extensive batch of parasite-specific proteins unique to Apicomplexa is lactylated in T. gondii. Our findings revealed that Kla was widespread in the early branching eukaryotic cell, and that lactylated proteins, including a crowd of unique parasite proteins, were involved in a remarkably diverse array of cellular functions. These valuable data will improve our understanding of the evolution of Kla while potentially providing novel therapeutic avenues.