Effect of Sterol Side Chain on Ion Channel Formation by Amphotericin B in Lipid Bilayers

Nakagawa, Yasuo; Umegawa, Yuichi; Takano, Tetsuro; Tsuchikawa, Hiroshi; Matsumori, Nobuaki; Murata, Michio

doi:10.1021/bi500122c

Cited by 14 publications

(25 citation statements)

References 40 publications

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“…Whilst the mechanism of AmB-ergosterol binding is not fully understood, in vitro analysis of the role of specific functional groups in ergosterol on AmB activity has revealed the importance both the C24-methyl group and 5(6)-7(8) double bond conjugation [16,17]. The former was suggested to promote Van der Waals interactions with AmB within the membrane [17], whereas the latter influences the rigidity of the ergosterol ring system, the structure thought to mediate Van der Waals interactions with the AmB heptaene moiety [46]. Therefore, in both cases, sterol changes could directly affect AmB binding, thus reducing its activity.…”

Section: Discussionmentioning

confidence: 99%

“…AmB exhibits specific cidal activity against Leishmania , as well as fungi, through interaction with ergosterol and close structural relatives, the major membrane sterol components in these organisms. Binding to cholesterol, the primary mammalian membrane sterol, is less avid due to its lacking conjugated 5(6)-7(8) double bonds in the ring structure (cholesterol has only a 5(6) double bond), and also methylation at the C24 position found in ergosterol [16,17]. Selection for AmB resistance in Leishmania in the cultured promastigote form has revealed loss of ergosterol-like sterols and accumulation of intermediates lacking one or both of these features in resistant lines [18–21].…”

Section: Introductionmentioning

confidence: 99%

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Genomic instability at the locus of sterol C24-methyltransferase promotes amphotericin B resistance in Leishmania parasites

et al. 2019

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Amphotericin B is an increasingly important tool in efforts to reduce the global disease burden posed by Leishmania parasites. With few other chemotherapeutic options available for the treatment of leishmaniasis, the potential for emergent resistance to this drug is a considerable threat. Here we characterised four novel amphotericin B-resistant Leishmania mexicana lines. All lines exhibited altered sterol biosynthesis, and hypersensitivity to pentamidine. Whole genome sequencing demonstrated resistance-associated mutation of the sterol biosynthesis gene sterol C5-desaturase in one line. However, in three out of four lines, RNA-seq revealed loss of expression of sterol C24-methyltransferase (SMT) responsible for drug resistance and altered sterol biosynthesis. Additional loss of the miltefosine transporter was associated with one of those lines. SMT is encoded by two tandem gene copies, which we found to have very different expression levels. In all cases, reduced overall expression was associated with loss of the 3’ untranslated region of the dominant gene copy, resulting from structural variations at this locus. Local regions of sequence homology, between the gene copies themselves, and also due to the presence of SIDER1 retrotransposon elements that promote multi-gene amplification, correlate to these structural variations. Moreover, in at least one case loss of SMT expression was not associated with loss of virulence in primary macrophages or in vivo . Whilst such repeat sequence-mediated instability is known in Leishmania genomes, its presence associated with resistance to a major antileishmanial drug, with no evidence of associated fitness costs, is a significant concern.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Genomic instability at the locus of sterol C24-methyltransferase promotes amphotericin B resistance in Leishmania parasites

et al. 2019

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“…Among clinically approved drugs, azoles inhibit ergosterol biosynthesis and polyene antimycotics, e.g., AmB directly interacts with ergosterol present in the membrane (71,72). We investigated the transcriptional effects of these drugs on osh genes in A. fumigatus.…”

Section: Resultsmentioning

confidence: 99%

Functional Analysis of Sterol Transporter Orthologues in the Filamentous Fungus Aspergillus nidulans

2015

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cPolarized growth in filamentous fungi needs a continuous supply of proteins and lipids to the growing hyphal tip. One of the important membrane compounds in fungi is ergosterol. At the apical plasma membrane ergosterol accumulations, which are called sterol-rich plasma membrane domains (SRDs). The exact roles and formation mechanism of the SRDs remained unclear, although the importance has been recognized for hyphal growth. Transport of ergosterol to hyphal tips is thought to be important for the organization of the SRDs. Oxysterol binding proteins, which are conserved from yeast to human, are involved in nonvesicular sterol transport. In Saccharomyces cerevisiae seven oxysterol-binding protein homologues (OSH1 to -7) play a role in ergosterol distribution between closely located membranes independent of vesicle transport. We found five homologous genes (oshA to oshE) in the filamentous fungi Aspergillus nidulans. The functions of OshA-E were characterized by gene deletion and subcellular localization. Each gene-deletion strain showed characteristic phenotypes and different sensitivities to ergosterolassociated drugs. Green fluorescent protein-tagged Osh proteins showed specific localization in the late Golgi compartments, puncta associated with the endoplasmic reticulum, or diffusely in the cytoplasm. The genes expression and regulation were investigated in a medically important species Aspergillus fumigatus, as well as A. nidulans. Our results suggest that each Osh protein plays a role in ergosterol distribution at distinct sites and contributes to proper fungal growth. Filamentous fungi grow by continuous tip elongation and branching and form hyphae and mycelium. Hyphal growth requires continuous transport of the proteins and lipids necessary for the extension of the cell wall and cell membrane. Polarized growth of filamentous fungi depends on the microtubule and actin cytoskeletons, along with their associated motor proteins (1-5). Apical membrane-associated landmark proteins, called "cell end markers," link these two cytoskeletons in Aspergillus nidulans (6-9). Furthermore, apical membrane domains play an important role in polarized growth and the localization of cell end markers (8,10,11).Membranes in eukaryotic cells are differentiated into different functional areas (12, 13). Sterols and sphingolipids can cluster into domains within mixtures of glycerophospholipids. These domains, termed "lipid rafts," contribute to specific protein localization at specific sites, such as glycosylphosphatidylinositol-anchored and lipid-associated proteins, and play important roles in cell signaling and cell polarity (14-16). One type of domain, characterized by a high sterol content, is found in fungi (17). Sterolrich membrane domains (SRDs) were visualized using the sterolbinding fluorescent dye filipin. The most abundant sterol found in fungi is ergosterol (18). Filipin stained the tips of mating projections in Saccharomyces cerevisiae (19) and Cryptococcus neoformans (20), cell ends in Schizosaccharomyces pombe (21),...

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“…Recently, we have reported the SAR results of various sterol analogs, and found that the AmB-ergosterol interaction is probably stabilized by face-face VDW interaction. 7,8 Thus, the gauche-containing conformation induced by 7a-OH-AmB may prevent the VDW contact between the AmB macrolide and sterol, consequently altering the sterol selectivity of 3 ( Fig. 3f/g).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, detailed SAR studies on sterols were conducted to evaluate their hydrophobic interactions. 7,8 For the mycosamine moiety, chemical modification of the C3 0 -amine group revealed that the positive charge of the amine was necessary for its activity. 9 More recent SAR studies disclosed that the C2 0 -OH group affects the sterol selectivity.…”

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confidence: 99%

Role of polyol moiety of amphotericin B in ion channel formation and sterol selectivity in bilayer membrane

Yamamoto

Umegawa

Tsuchikawa

et al. 2015

Bioorganic & Medicinal Chemistry

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Amphotericin B (AmB) is a polyene macrolide antibiotic widely used to treat mycotic infections. In this paper, we focus on the role of the polyol moiety of AmB in sterol selectivity using 7-oxo-AmB, 7α-OH-AmB, and 7β-OH-AmB. The 7-OH analogs were prepared from 7-oxo-AmB. Their K(+) flux activity in liposomes showed that introduction of an additional ketone or hydroxy group on the polyol moiety reduces the original activity. Conformational analyses of these derivatives indicated that intramolecular hydrogen-bonding network possibly influenced the conformational rigidity of the macrolactone ring, and stabilized the active conformation in the membrane. Additionally, the flexible polyol leads to destabilization of the whole macrolactone ring conformation, resulting in a loss of sterol selectivity.

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Effect of Sterol Side Chain on Ion Channel Formation by Amphotericin B in Lipid Bilayers

Cited by 14 publications

References 40 publications

Genomic instability at the locus of sterol C24-methyltransferase promotes amphotericin B resistance in Leishmania parasites

Genomic instability at the locus of sterol C24-methyltransferase promotes amphotericin B resistance in Leishmania parasites

Functional Analysis of Sterol Transporter Orthologues in the Filamentous Fungus Aspergillus nidulans

Role of polyol moiety of amphotericin B in ion channel formation and sterol selectivity in bilayer membrane

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