Inhibition of the malaria parasite polyprenol kinase enzyme

Plasmodium falciparum is the etiological agent of human sickle cell malaria, one of the most prevalent diseases in tropical and subtropical regions of the world. One of the biggest problems for disease control is the emergence of drug resistance, leading to the need to discover new antimalarial compounds and more effective pharmaceutical combinations. One of the most studied metabolic pathways for the development of antimalarials is the methylerythritol 4-phosphate (MEP) pathway, which is absent in humans. The MEP pathway can be inhibited by fosmidomycin and ribosomal inhibitors (eg clindamycin, chloramphenicol). However, both types of compounds show little effectiveness and high rates of recrudescence in the treatment of human malaria. Therefore, it is necessary to find ways to enhance the effect of these drugs. The products of the MEP pathway, isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), are condensed to form longer isoprenoids, such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). These isoprenoids are initial substrates for the biosynthesis of several metabolites such as dolichols, ubiquinone and for the isoprenylation of proteins, a post-translational modification that occurs mainly in proteins that regulate intracellular traffic, such as Ras and Rap proteins. Several studies point out that the loss of protein isoprenylation process is the proximal cause of death of parasites whose isoprenoid biosynthesis has been pharmacologically inhibited. Although the natural substrates of protein isoprenylation are FPP or GGPP, it has already been demonstrated that polyprenols such as farnesol (FOH) and geranylgeraniol (GGOH), present in human food and blood plasma, can rescue parasites from the effect of MEP pathway inhibitors . These data suggest that the parasite has a pathway for the reuse of polyprenols via phosphorylation whose pharmacological inhibition could enable the use of fosmidomycin and ribosomal inhibitors for the treatment of the disease. Genes involved in this pathway have only been identified in plants, but biochemical evidence exists that they are also present in archaea and animals, in which the pathway would be strongly related to different types of cancer and dyslipidemias. In any case, evidence from the literature indicates that the polyprenols recycling pathway is universally carried out by two enzymes, a polyprenol kinase and a polyprenyl-P kinase. Previous studies led to the identification of the gene that codes for P. falciparum polyprenol kinase. Catalytic activity was evaluated using [1-(n)-3H] GGOH and [1-(n)-3H] FOH and knockout parasites were shown to be viable, but more sensitive to MEP pathway inhibitors and lacking the ability to metabolize polyprenols. This project also proposes to create P. berghei knockout parasites for the locus that encodes polyprenol kinase (the etiological agent of murine malaria) to assess whether the parasite can sustain itself with exogenous polyprenols during the treatment of animals with inhibitors of the MEP pathway. Finally, it will also look for inhibitors of this enzyme and, if found, test them in vitro and in vivo, alone or in combination with other drugs. It is believed that the present project can lead to the discovery of synergistic molecules with MEP pathway inhibitors and elucidate one of the least studied metabolic pathways in biology. Furthermore, it could set an important precedent to be explored for the treatment of other infectious diseases and several types of cancer.

Project details

Basic Science

Jun 2023 — May 2025

Brazil