Dataset Information

The Antifungal Drug Isavuconazole Is both Amebicidal and Cysticidal against Acanthamoeba castellanii.

ABSTRACT: Current treatments for Acanthamoeba keratitis rely on a combination of chlorhexidine gluconate, propamidine isethionate, and polyhexamethylene biguanide. These disinfectants are nonspecific and inherently toxic, which limits their effectiveness. Furthermore, in 10% of cases, recurrent infection ensues due to the difficulty in killing both trophozoites and double-walled cysts. Therefore, development of efficient, safe, and target-specific drugs which are capable of preventing recurrent Acanthamoeba infection is a critical unmet need for averting blindness. Since both trophozoites and cysts contain specific sets of membrane sterols, we hypothesized that antifungal drugs targeting sterol 14-demethylase (CYP51), known as conazoles, would have deleterious effects on A. castellanii trophozoites and cysts. To test this hypothesis, we first performed a systematic screen of the FDA-approved conazoles against A. castellanii trophozoites using a bioluminescence-based viability assay adapted and optimized for Acanthamoeba The most potent drugs were then evaluated against cysts. Isavuconazole and posaconazole demonstrated low nanomolar potency against trophozoites of three clinical strains of A. castellanii Furthermore, isavuconazole killed trophozoites within 24?h and suppressed excystment of preformed Acanthamoeba cysts into trophozoites. The rapid action of isavuconazole was also evident from the morphological changes at nanomolar drug concentrations causing rounding of trophozoites within 24?h of exposure. Given that isavuconazole has an excellent safety profile, is well tolerated in humans, and blocks A. castellanii excystation, this opens an opportunity for the cost-effective repurposing of isavuconazole for the treatment of primary and recurring Acanthamoeba keratitis.

SUBMITTER: Shing B

PROVIDER: S-EPMC7179639 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The Antifungal Drug Isavuconazole Is both Amebicidal and Cysticidal against Acanthamoeba castellanii.

Shing Brian B Singh Seema S Podust Larissa M LM McKerrow James H JH Debnath Anjan A

Antimicrobial agents and chemotherapy 20200421 5

Current treatments for <i>Acanthamoeba</i> keratitis rely on a combination of chlorhexidine gluconate, propamidine isethionate, and polyhexamethylene biguanide. These disinfectants are nonspecific and inherently toxic, which limits their effectiveness. Furthermore, in 10% of cases, recurrent infection ensues due to the difficulty in killing both trophozoites and double-walled cysts. Therefore, development of efficient, safe, and target-specific drugs which are capable of preventing recurrent <i> ...[more]

PMID: 32094126

Similar Datasets

Project description:Cytochromes P450 (P450, CYP) metabolize a wide variety of endogenous and exogenous lipophilic molecules, including most drugs. Sterol 14α-demethylase (CYP51) is a target for antifungal drugs known as conazoles. Using X-ray crystallography, we have discovered a domain-swap homodimerization mode in CYP51 from a human pathogen, Acanthamoeba castellanii CYP51 (AcCYP51). Recombinant AcCYP51 with a truncated transmembrane helix was purified as a heterogeneous mixture corresponding to the dimer and monomer units. Spectral analyses of these two populations have shown that the CO-bound ferrous form of the dimeric protein absorbed at 448 nm (catalytically competent form), whereas the monomeric form absorbed at 420 nm (catalytically incompetent form). AcCYP51 dimerized head-to-head via N-termini swapping, resulting in formation of a nonplanar protein-protein interface exceeding 2000 Å2 with a total solvation energy gain of -35.4 kcal/mol. In the dimer, the protomers faced each other through the F and G α-helices, thus blocking the substrate access channel. In the presence of the drugs clotrimazole and isavuconazole, the AcCYP51 drug complexes crystallized as monomers. Although clotrimazole-bound AcCYP51 adopted a typical CYP monomer structure, isavuconazole-bound AcCYP51 failed to refold 74 N-terminal residues. The failure of AcCYP51 to fully refold upon inhibitor binding in vivo would cause an irreversible loss of a structurally aberrant enzyme through proteolytic degradation. This assumption explains the superior potency of isavuconazole against A. castellanii The dimerization mode observed in this work is compatible with membrane association and may be relevant to other members of the CYP family of biologic, medical, and pharmacological importance. SIGNIFICANCE STATEMENT: We investigated the mechanism of action of antifungal drugs in the human pathogen Acanthamoeba castellanii. We discovered that the enzyme target [Acanthamoeba castellanii sterol 14α-demethylase (AcCYP51)] formed a dimer via an N-termini swap, whereas drug-bound AcCYP51 was monomeric. In the AcCYP51-isavuconazole complex, the protein target failed to refold 74 N-terminal residues, suggesting a fundamentally different mechanism of AcCYP51 inactivation than only blocking the active site. Proteolytic degradation of a structurally aberrant enzyme would explain the superior potency of isavuconazole against A. castellanii.

Dataset Information

The Antifungal Drug Isavuconazole Is both Amebicidal and Cysticidal against Acanthamoeba castellanii.

Publications

The Antifungal Drug Isavuconazole Is both Amebicidal and Cysticidal against Acanthamoeba castellanii.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets