Effect of drugs inhibiting spermidine biosynthesis and metabolism on the in vitro development of Plasmodium falciparum

Abstract

Treatment of Plasmodium falciparum with the potent inhibitor dicyclohexylamine completely arrests in vitro cell proliferation of the chloroquine-susceptible P. falciparum strain NF54 and the R strain, which shows less sensivity to chloroquine. The average inhibitory concentration (IC 50 ) values determined for both strains revealed dierent inhibition pro®les. The IC 50 value for the chloroquine-sensitive NF54 strain was 97 lM and 501 lM for the R strain. Monitoring polyamine pools after treatment with dicyclohexylamine leads to a signi®cant decrease in the intracellular spermidine content, which was nearly reversed by supplementation with spermidine. Since spermidine is an important precursor for the biosynthesis of hypusine and homospermidine in eukaryotes, we studied the developmental eect on both P. falciparum strains of 1,7-diaminoheptane as an inhibitor of deoxyhypusine synthase (EC 1.1.1.249) in mammalian cells, and agmatine as a moderate inhibitor of homospermidine synthase (EC 2.5.1.44). Inhibition pro®les with 1,7-diaminoheptane resulted in an IC 50 value of 466 lM for the NF54 strain and 319 lM for the R strain. Spermidine pools changed signi®cantly. Inhibition with agmatine caused a strong decrease in parasitemia for the chloroquine-susceptible NF54 strain, with a determined IC 50 value of 431 lM and an IC 50 value of 340 lM for the less chloroquine-susceptible R strain. Spermidine was not detectable after inhibition. The uncommon triamine homospermidine occurred in both P. falciparum strains. To our knowledge this is the ®rst evidence of homo-spermidine in P. falciparum. The use of speci®c inhibitors of spermidine metabolism might be a novel strategy for the design of new antimalarials, and suggests the occurrence of both enzymes in the parasite.

Crystallization and preliminary X-ray diffraction analysis of spermidine synthase fromHelicobacter pylori

“…A decrease in polyamine levels, especially levels of spermidine and spermine, is often lethal, resulting in cell-cycle arrest or apoptosis (Schipper et al, 2000;Nitta et al, 2002;Wallace et al, 2003). Polyamine analogues have been used in the treatment of a number of parasitic infections (Kaiser et al, 2001;Heby et al, 2003). The growth inhibition of Helicobacter pylori by a multi-enzyme inhibitor of polyamine biosynthesis has also been investigated (Takaji et al, 1997).…”

Completing the hypusine pathway in Plasmodium

“…dohh is present as a single-copy gene on chromosome 13 in P. falciparum and is transcribed in asexual blood stages (http://plasmodb.org/plasmo/). Inhibition of spermidine synthase [5] depletes hypusine formation and parasite proliferation in vitro. In this context, it would be of considerable interest for the future to study the phenotype of a dohh knockout mutant by targeted gene disruption that progresses through the malaria life-cycle of a Plasmodium berghei rodent model with impaired function [22].…”

“…The triamine spermidine [5] is essential for proliferation of the parasite and is an essential substrate in the biosynthesis of hypusine [N(epsilon)-(4-amino-2-hydroxybutyl) lysine], a novel amino acid present in eukaryotic initiation factor-5A (eIF-5A). Hypusine is formed in a post-translational modification that involves two sequential enzymatic steps catalyzed by deoxyhypusine synthase (DHS; EC 1.11.2249) and deoxyhypusine hydroxylase (DOHH; EC 1.14.9929) [6].…”

Peer Review #2 of "Validation of Plasmodium falciparum deoxyhypusine synthase as an antimalarial target (v0.1)"

“…The enzymatic activity of PfDHS is inhibited by N 1 -guanyl-1,7-diaminoheptane (GC7), a known inhibitor of human DHS enzyme (Kaiser et al, 2007). Hypusination of eIF5A by PfDHS 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 PfDHS 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).…”