Fungicidal amphotericin B sponges are assemblies of staggered asymmetric homodimers encasing large void volumes

Lewandowska, Agnieszka; Soutar, Corinne P.; Greenwood, Alexander I.; Nimerovsky, Evgeny; Lio, Ashley M. De; Holler, Jordan T; Hisao, Grant S.; Khandelwal, Ankur; Zhang, Jiabao; SantaMaria, Anna M.; Schwieters, Charles D.; Pogorelov, Taras V.; Burke, Martin D.; Rienstra, Chad M.

doi:10.1038/s41594-021-00685-4

Cited by 25 publications

(17 citation statements)

References 61 publications

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“…Furthermore, indoles and other nitrogen-based heterocyclic compounds inhibit the conversion of lanosterol into ergosterol [ 88 , 89 , 90 ]. Our findings corroborate those reported in the literature, as both nitrofuran and indole derivatives can inhibit/reduce fungal membrane ergosterol; however, we cannot predict if they act in the biosynthesis or directly on the membrane, as in the case of AmB, which binds to the membrane ergosterol and can cause a “sponge effect” extracting the ergosterol [ 91 , 92 , 93 ], and ITZ, which interferes with its synthesis, in both cases with a consequent reduction in the amount of ergosterol in the fungal membrane [ 51 , 62 ].…”

Section: Discussionsupporting

confidence: 86%

Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

et al. 2022

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Histoplasma capsulatum is a fungus that causes histoplasmosis. The increased evolution of microbial resistance and the adverse effects of current antifungals help new drugs to emerge. In this work, fifty-four nitrofurans and indoles were tested against the H. capsulatum EH-315 strain. Compounds with a minimum inhibitory concentration (MIC90) equal to or lower than 7.81 µg/mL were selected to evaluate their MIC90 on ATCC G217-B strain and their minimum fungicide concentration (MFC) on both strains. The quantification of membrane ergosterol, cell wall integrity, the production of reactive oxygen species, and the induction of death by necrosis–apoptosis was performed to investigate the mechanism of action of compounds 7, 11, and 32. These compounds could reduce the extracted sterol and induce necrotic cell death, similarly to itraconazole. Moreover, 7 and 11 damaged the cell wall, causing flaws in the contour (11), or changing the size and shape of the fungal cell wall (7). Furthermore, 7 and 32 induced reactive oxygen species (ROS) formation higher than 11 and control. Finally, the cytotoxicity was measured in two models of cell culture, i.e., monolayers (cells are flat) and a three-dimensional (3D) model, where they present a spheroidal conformation. Cytotoxicity assays in the 3D model showed a lower toxicity in the compounds than those performed on cell monolayers. Overall, these results suggest that derivatives of nitrofurans and indoles are promising compounds for the treatment of histoplasmosis.

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Section: Discussionsupporting

confidence: 86%

Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

et al. 2022

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“…7 AMB has also been proposed to exert antifungal activity by several modes of action, including the sequestration of ergosterol leading to disruption of the membrane stability, 37 the induction of oxidative bursts within fungi by directly acting as a prooxidant, 7 and by causing mitochondrial damage. 38 In addition, a sterol-sponge model 9,10 has been proposed in which AMB forms a self-assembled aggregate, the sterol-sponge, that extracts ergosterol from the cell membrane. The cell wall structures of fungi consist of multilayers of mannoprotein, β-glucan, and chitin and the plasma membrane (Figure 1C), and these multilayers are believed to prevent AMB and chitinases from interacting with the plasma membrane and chitins, respectively.…”

Section: ■ Discussionmentioning

confidence: 99%

“…7 The primary mechanism is the interaction of AMB with ergosterol in the fungal cell membrane to form small pores on the plasma membrane, whereby small ions leak out through these pores, resulting in the death of the fungi. Other reported mechanisms of AMB are the sequestration 8 and extraction of ergosterol 9,10 the plasma membrane and the induction of oxidative stress. 11 However, AMB also interacts weakly with cholesterolan analogue of ergosterol used in mammalian cell membranes and exerts similar destructive effects on mammalian cells, resulting in strong toxicity when prescribed at high concentrations.…”

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confidence: 99%

Enhancement of the Antifungal Activity of Chitinase by Palmitoylation and the Synergy of Palmitoylated Chitinase with Amphotericin B

et al. 2022

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Combinations of antifungal drugs can have synergistic antifungal activity, achieving high therapeutic efficacy while minimizing the side effects. Amphotericin B (AMB) has been used as a standard antifungal drug for fungal infections; however, because of its high toxicity, new strategies to minimize the required dose are desirable. Chitinases have recently received attention as alternative safe antifungal agents. Herein, we report the combination of palmitoylated chitinase domains with AMB to enhance the antifungal activity. The chitin-binding domain (LysM) from Pteris ryukyuensis chitinase was site-specifically palmitoylated by conjugation reaction catalyzed by microbial transglutaminase. The palmitoylated LysM (LysM-Pal) exhibited strong antifungal activity against Trichoderma viride, inhibiting the growth completely at a concentration of 2 μM. This antifungal effect of LysM-Pal was mainly due to the effect of anchoring of palmitic acid motif to the plasma membrane of fungi. A combination of AMB with LysM-Pal resulted in synergistic enhancement of the antifungal activity. Intriguingly, LysM-Pal exhibited higher level of antifungal activity enhancement than palmitoylated catalytic domain (CatD) and fusion of LysM and CatD. Addition of 0.5 μM LysM-Pal to AMB reduced the minimal inhibition concentration of AMB to 0.31 μM (2.5 μM without LysM-Pal). The possible mechanism of the synergistic effect of AMB and LysM-Pal is destabilization of the plasma membrane by anchoring of palmitic acid and ergosterol extraction by AMB and destabilization of the chitin layer by LysM binding. The combination of LysM-Pal with AMB can drastically reduce the dose of AMB and may be a useful strategy to treat fungal infections.

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“…2B ), indicating that molecular motion was slow enough to allow accurate measurements of the 13 C- 19 F distances in the membrane. With these distance constraints in hand, we investigated an assembly structure that could account for the NMR results without being constrained by previous models, such as the barrel-stave model and sterol-sponge model ( 24 , 25 ). Recently, we found that the vertical penetration of AmB through the lipid bilayer corresponds to the length of a single drug molecule under experimental conditions similar to those used in this study ( 26 , 27 ).…”

Section: Resultsmentioning

confidence: 99%

Amphotericin B assembles into seven-molecule ion channels: An NMR and molecular dynamics study

et al. 2022

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Amphotericin B, an antifungal drug with a long history of use, forms fungicidal ion-permeable channels across cell membranes. Using solid-state nuclear magnetic resonance spectroscopy and molecular dynamics simulations, we experimentally elucidated the three-dimensional structure of the molecular assemblies formed by this drug in membranes in the presence of the fungal sterol ergosterol. A stable assembly consisting of seven drug molecules was observed to form an ion conductive channel. The structure is somewhat similar to the upper half of the barrel-stave model proposed in the 1970s but substantially different in the number of molecules and in their arrangement. The present structure explains many previous findings, including structure-activity relationships of the drug, which will be useful for improving drug efficacy and reducing adverse effects.

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Fungicidal amphotericin B sponges are assemblies of staggered asymmetric homodimers encasing large void volumes

Cited by 25 publications

References 61 publications

Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

Enhancement of the Antifungal Activity of Chitinase by Palmitoylation and the Synergy of Palmitoylated Chitinase with Amphotericin B

Amphotericin B assembles into seven-molecule ion channels: An NMR and molecular dynamics study

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