A suggested vital function for eIF‐5A and dhs genes during murine malaria blood‐stage infection

Abstract

The biological function of the post‐translational modification hypusine in the eukaryotic initiation factor 5A ( EIF ‐5A) in eukaryotes is still not understood. Hypusine is formed by two sequential enzymatic steps at a specific lysine residue in the precursor protein EIF ‐5A. One important biological function of EIF ‐5A which was recently identified is the translation of polyproline‐rich mRNA , suggesting its biological relevance in a variety of biological processes. Hypusinated eIF ‐5A controls the proliferation of cancer cells and inflammatory processes in malaria. It was shown that pharmacological inhibition of the enzymes involved in this pathway, deoxyhypusine synthase ( DHS ) and the deoxyhypusine hydroxylase ( DOHH ), arrested the growth of malaria parasites. Down‐regulation of both the malarial eIF ‐5A and dhs genes by in vitro and in vivo silencing led to decreased transcript levels and protein expression and, in turn, to low parasitemia, confirming a critical role of hypusination in eIF ‐5A for proliferation in Plasmodium . To further investigate whether eIF ‐5A and the activating enzyme DHS are essential for Plasmodium erythrocytic stages, targeted gene disruption was performed in the rodent malaria parasite Plasmodium berghei . Full disruption of both genes was not successful; instead parasites harboring the episome for eIF ‐5A and dhs genes were obtained, suggesting that these genes may perform vital functions during the pathogenic blood cell stage. Next, a knock‐in strategy was pursued for both endogenous genes eIF ‐5A and dhs from P. berghei . The latter resulted in viable recombinant parasites, strengthening the observation that they might be essential for proliferation during asexual development of the malaria parasite.

The Role of Spermidine and Its Key Metabolites in Important, Pathogenic Human Viruses and in Parasitic Infections Caused by Plasmodium falciparum and Trypanosoma brucei

“…Spd is an essential substrate for hypusine formation in Plasmodium [47]. Both enzymes of the hypusine pathway have been cloned and characterized and have shown to be vital genes in murine blood-stages [48] using reverse genetics similar to homologous recombination techniques, suggesting the importance of the pathway for infection. Moreover, a recent targeting of SpdS in P. yoelii, by deletion/complementation analyses, demonstrated the gene to be essential for blood-stage growth [49].…”

Investigation of an Allosteric Deoxyhypusine Synthase Inhibitor in P. falciparum

“…Different small-molecule inhibitors targeting either dhs or DOHH arrest the growth of the malaria parasite [12]. To further investigate the essential function of the eIF5A precursor protein and the activating dhs enzyme in the pathogenic blood cell stage, targeted gene disruption was performed in the rodent malaria parasite P. berghei [13]. However, only transgenic parasites with either eIF5A or dhs in their episome were obtained, suggesting a vital function in murine malaria blood stages.…”

Validation ofPlasmodium falciparumdeoxyhypusine synthase as an antimalarial target

“…Hypusination of eIF5A by Pf DHS is likely to be essential since P. falciparum is moderately sensitive to growth inhibition by GC7 (Kaiser et al, 2001) and no insertions of piggyBac transposon within the Pf DHS gene are tolerated (Zhang et al, 2018). The orthologous gene encoding DHS enzyme in the murine malaria parasite P. berghei is essential, since clonal transgenic P. berghei parasites with knockout of the DHS gene cannot be isolated (Kersting et al, 2016), and P. berghei DHS knockout parasites have a severe growth defect causing them to rapidly disappear from host animals co-infected with other transgenic parasites (Bushell et al, 2017).…”