# Characterization of Entamoeba fatty acid elongases; validation as targets and provision of promising leads for new drugs against amebiasis

## TL;DR

Researchers identified fatty acid elongases in Entamoeba histolytica as potential drug targets and found herbicides that could inhibit the parasite's growth without harming human cells.

## Contribution

The study characterizes fatty acid elongases in Entamoeba and validates them as drug targets with promising herbicides as leads.

## Key findings

- E. histolytica fatty acid elongases (EhFAEs) are responsible for producing unique acyl chain diversity in the parasite's lipids.
- Herbicides like flufenacet, cafenstrole, and fenoxasulfone inhibit very long acyl chain production and impair parasite proliferation and cyst formation.
- These herbicides show no toxicity to human cells, making EhFAEs viable targets for new anti-amebiasis drugs.

## Abstract

Entamoeba histolytica is a protozoan parasite belonging to the phylum Amoebozoa that causes amebiasis, a global public health problem. E. histolytica alternates its form between a proliferative trophozoite and a dormant cyst. Trophozoite proliferation is closely associated with amebiasis symptoms and pathogenesis whereas cysts transmit the disease. Drugs are available for clinical use; however, they have issues of adverse effects and dual targeting of disease symptoms and transmission remains to be improved. Development of new drugs is therefore urgently needed. An untargeted lipidomics analysis recently revealed structural uniqueness of the Entamoeba lipidome at different stages of the parasite’s life cycle involving very long (26–30 carbons) and/or medium (8–12 carbons) acyl chains linked to glycerophospholipids and sphingolipids. Here, we investigated the physiology of this unique acyl chain diversity in Entamoeba, a non-photosynthetic protist. We characterized E. histolytica fatty acid elongases (EhFAEs), which are typically components of the fatty acid elongation cycle of photosynthetic protists and plants. An approach combining genetics and lipidomics revealed that EhFAEs are involved in the production of medium and very long acyl chains in E. histolytica. This approach also showed that the K3 group herbicides, flufenacet, cafenstrole, and fenoxasulfone, inhibited the production of very long acyl chains, thereby impairing Entamoeba trophozoite proliferation and cyst formation. Importantly, none of these three compounds showed toxicity to a human cell line; therefore, EhFAEs are reasonable targets for developing new anti-amebiasis drugs and these compounds are promising leads for such drugs. Interestingly, in the Amoebazoan lineage, gain and loss of the genes encoding two different types of fatty acid elongase have occurred during evolution, which may be relevant to parasite adaptation. Acyl chain diversity in lipids is therefore a unique and indispensable feature for parasitic adaptation of Entamoeba.

Entamoeba, a protozoan parasite, thrives in its niche by alternating its form between a proliferative trophozoite and a dormant cyst. Entamoeba parasites were recently shown to generate lipid acyl chain diversity throughout their life cycle. Here, we provide insight into the mechanism generating this acyl chain diversity and its importance in maintaining the parasite’s life cycle. We also show that the E. histolytica isozymes responsible for generating this diversity are reasonable targets for developing new anti-amebiasis drugs, and that the herbicides, flufenacet, cafenstrole, and fenoxasulfone, are promising leads for such drugs. Interestingly, gain and loss of the two genes encoding the isozymes controlling acyl chain diversity is plausibly related to E. histolytica host adaptation.