Inhibition of Plasmodium falciparum Choline Kinase by Hexadecyltrimethylammonium Bromide: a Possible Antimalarial Mechanism

Abstract

Choline kinase is the first enzyme in the Kennedy pathway (CDP-choline pathway) for the biosynthesis of the most essential phospholipid, phosphatidylcholine, in Plasmodium falciparum. In addition, choline kinase also plays a pivotal role in trapping essential polar head group choline inside the malaria parasite. Recently, Plasmodium falciparum choline kinase (PfCK) has been cloned, overexpressed, and purified. However, the function of this enzyme in parasite growth and survival has not been evaluated owing to the lack of a suitable inhibitor. Purified recombinant PfCK enabled us to identify an inhibitor of PfCK, hexadecyltrimethylammonium bromide (HDTAB), which has a very close structural resemblance to hexadecylphosphocholine (miltefosin), the well-known antiproliferative and antileishmanial drug. HDTAB inhibited PfCK in a dose-dependent manner and offered very potent antimalarial activity in vitro against Plasmodium falciparum. Moreover, HDTAB exhibited profound antimalarial activity in vivo against the rodent malaria parasite Plasmodium yoelii (N-67 strain). Interestingly, parasites at the trophozoite and schizont stages were found to be particularly sensitive to HDTAB. The stage-specific antimalarial effect of HDTAB correlated well with the expression pattern of PfCK in P. falciparum, which was observed by reverse transcription-PCR and immunofluorescence microscopy. Furthermore, the antimalarial activity of HDTAB paralleled the decrease in phosphatidylcholine content, which was found to correlate with the decreased phosphocholine generation. These results suggest that inhibition of choline kinase by HDTAB leads to decreased phosphocholine, which in turn causes a decrease in phosphatidylcholine biosynthesis, resulting in death of the parasite.

Preclinical Characterization of RSM-932A, a Novel Anticancer Drug Targeting the Human Choline Kinase Alpha, an Enzyme Involved in Increased Lipid Metabolism of Cancer Cells

“…Once the proof-of-principle that ChoKa is a validated target in oncology has been set up, a very intensive activity has been developed for the identification of novel ChoKa inhibitors with potential use as antitumoral drugs (15)(16)(17)(18)(19)(20)(28)(29)(30)(31) and also as antiparasitic compounds (32,33).…”

Antiplasmodial Activity and Mechanism of Action of RSM-932A, a Promising Synergistic Inhibitor of Plasmodium falciparum Choline Kinase

“…The primary sequence of the catalytic site (12) and the tertiary structure (PDB 3FI8; www.pdb.org) of p.f.-ChoK are conserved with respect to other ChoKs. Furthermore, p.f.-ChoK is more highly expressed in growth phases of P. falciparum (12), and inhibition of ChoK affects the parasite's viability in in vitro and mouse models of malaria (13). HC-3 has been shown to inhibit recombinant p.f.-ChoK (14) and to be lethal against the parasite (15).…”

Effects of miltefosine treatment in fibroblast cell cultures and in mice experimentally infected withNeospora caninumtachyzoites

“…The mode of action of miltefosine against Leishmania parasites involves the interaction with membrane phospholipids and sterols, and the drug interferes with the functionality of a number of enzymes involved in phospholipid metabolism such as protein kinase C and the phospholipases A, C and D, finally leading to apoptosis (Barratt et al 2009). Hexadecyltrimethylammonium bromide, a compound structurally similar to miltefosine, was demonstrated to exhibit potent in vitro activity against Plasmodium falciparum (Walochnik et al 2002;Schuster et al 2006;Choubey et al 2007).…”