Transcriptional changes in Toxoplasma gondii in response to treatment with monensin

Abstract

Background: Infection with the apicomplexan protozoan parasite T. gondii can cause severe and potentially fatal cerebral and ocular disease, especially in immunocompromised individuals. The anticoccidial ionophore drug monensin has been shown to have anti-Toxoplasma gondii properties. However, the comprehensive molecular mechanisms that underlie the effect of monensin on T. gondii are still largely unknown. We hypothesized that analysis of T. gondii transcriptional changes induced by monensin treatment can reveal new aspects of the mechanism of action of monensin against T. gondii.Methods: Porcine kidney (PK)-15 cells were infected with tachyzoites of T. gondii RH strain. Three hours post-infection, PK-15 cells were treated with 0.1 μM monensin, while control cells were treated with medium only. PK-15 cells containing intracellular tachyzoites were harvested at 6 and 24 h post-treatment, and the transcriptomic profiles of T. gondii-infected PK-15 cells were examined using high-throughput RNA sequencing (RNA-seq). Quantitative real-time PCR was used to verify the expression of 15 differentially expressed genes (DEGs) identified by RNA-seq analysis.Results: A total of 4868 downregulated genes and three upregulated genes were identified in monensin-treated T. gondii, indicating that most of T. gondii genes were suppressed by monensin. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of T. gondii DEGs showed that T. gondii metabolic and cellular pathways were significantly downregulated. Spliceosome, ribosome, and protein processing in endoplasmic reticulum were the top three most significantly enriched pathways out of the 30 highly enriched pathways detected in T. gondii. This result suggests that monensin, via down-regulation of protein biosynthesis in T. gondii, can limit the parasite growth and proliferation. Conclusions:Our findings provide a comprehensive insight into T. gondii genes and pathways with altered expression following monensin treatment. These data can be further explored to achieve better understanding of the specific mechanism of action of monensin against T. gondii.

Transcriptome Profiling of Toxoplasma gondii-Infected Human Cerebromicrovascular Endothelial Cell Response to Treatment with Monensin

“…These results suggest that parasite inhibition may have been achieved through dysregulation of the biosynthesis of key nutrients in the host cells and/or inhibition of nutrient transport between cell organelles, limiting their transport into parasitophorous vacuole. This finding is consistent with a previous transcriptomic study of monensin-treated porcine kidney (PK)-15 cells, which revealed an overrepresentation of the downregulated genes involved in the biosynthesis of spliceosome, ribosome, and protein processing in ER, suggesting that monensin, via down-regulation of protein biosynthesis, can limit the parasite growth and proliferation [41].…”

Early Transcriptional Response to Monensin in Sensitive and Resistant Strains of Eimeria tenella

“…However, these genes were then upregulated after 4 h of treatment in the E. tenella- resistant strain. Different results were observed in the T. gondii RH strain, cytoskeletal and transmembrane proteins were differently expressed in the monensin-resistant strain determined by proteomics (Thabet et al, 2018 ), and the other study showed that protein biosynthesis-related pathways (spliceosome, ribosome, and protein processing in the endoplasmic reticulum) were downregulated in T. gondii RH strain in response to 24 h of monensin treatment (Zhai et al, 2020 ). These results suggest that monensin treatment affects parasite protein synthesis and may have different effects on different parasite stages (e.g., sporozoites and tachyzoites).…”

“…Lavine and Arrizabalaga (Lavine and Arrizabalaga, 2011 ) highlighted that canonical histones were significantly upregulated in T. gondii after 24 h of exposure to monensin, suggesting that monensin alters the cell cycle of the parasite. More recently, Zhai et al ( 2020 ) showed that protein biosynthesis-related pathways were significantly downregulated in T. gondii after monensin treatment. Quantitative proteomic analysis was also used to understand the differences in gene expression between E. tenella -sensitive and -resistant strains (Thabet et al, 2017 ).…”

Genome-Wide CRISPR/Cas9 Screen Identifies New Genes Critical for Defense Against Oxidant Stress in Toxoplasma gondii

“…As shown in our previous study that TR in T. gondii is an essential virulence effector with antioxidant function, which is critical for parasite growth and survival ( Xue et al, 2017 ). Moreover, in-depth studies of T. gondii antioxidant-related genes may provide a theoretical basis for developing anti- T. gondii drugs because some currently available drugs (such as monensin, mefloquine, and artemisinin) that induce ROS production and target the antioxidant system have been shown to be effective against T. gondii and/or Plasmodium ( Berens et al, 1998 ; Charvat and Arrizabalaga, 2016 ; Gunjan et al, 2016 ; Zhai et al, 2020 ). Therefore, identification parasite antioxidant genes is important for understanding the mechanisms of T. gondii in eliminating ROS, as well as for identifying useful targets for anti- Toxoplasma drugs, and this requires further investigations.…”