Proteomic analysis of L-Methionine Sulfoximine (MSO)-treated Plasmodium falciparum by LC-MS/MS

LC-MS/MS of in-solution trypsin digested parasite protein extracts was carried out to examine the proteome of MSO-treated Pf parasites. Proteins were extracted from the untreated and MSO-treated parasite pellets of two independent experiments (Exp1: T7_R Vs T8; Exp2: T3_R Vs T4_R). For each experiment, two different sets of untreated and MSO-treated cultures synchronized for ring stages and early trophozoites were used. MSO treatment was carried out at 50 M concentration for 12 h. A total number of 149 proteins associated with various metabolic and cellular functions, cytoadherence and host invasion, Hb degradation, etc., were downregulated in MSO-treated parasites. This also included important asparagine-rich proteins such as tRNA ligases, components of RNA processing and protein degradation pathways, lipocalin associated with hemozoin formation and antimalarial drug sensitivity, heat shock protein 110c essential for stabilizing the asparagine repeat-rich parasite proteins etc. Only ten proteins were found to be upregulated in MSO-treated Pf3D7 parasites. For downregulated proteins, proteins identified in both the untreated controls of two independent experiments and either undetectable or significantly downregulated (>1.5 fold) in MSO-treated Pf3D7 parasites were considered. For upregulated proteins, proteins significantly upregulated (>1.5 fold) in both the MSO-treated parasites of two independent experiments and/or undetectable in the untreated controls but detectable in the MSO-treated parasites were considered.