The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles

ABSTRACT The fungal cell wall is a critically important structure that represents a permeability barrier and protective shield. We probed Candida albicans and Cryptococcus neoformans with liposomes containing amphotericin B (AmBisome), with or without 15-nm colloidal gold particles. The liposomes ha...

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Autores principales:	Louise Walker, Prashant Sood, Megan D. Lenardon, Gillian Milne, Jon Olson, Gerard Jensen, Julie Wolf, Arturo Casadevall, Jill Adler-Moore, Neil A. R. Gow
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2018
Materias:	amphotericin B antifungal drug cell membranes fungal cell wall mannoproteins Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/1d4cb09fdbb94153b48f0ccb07f36441
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spelling	oai:doaj.org-article:1d4cb09fdbb94153b48f0ccb07f364412021-11-15T15:53:26ZThe Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles10.1128/mBio.02383-172150-7511https://doaj.org/article/1d4cb09fdbb94153b48f0ccb07f364412018-03-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02383-17https://doaj.org/toc/2150-7511ABSTRACT The fungal cell wall is a critically important structure that represents a permeability barrier and protective shield. We probed Candida albicans and Cryptococcus neoformans with liposomes containing amphotericin B (AmBisome), with or without 15-nm colloidal gold particles. The liposomes have a diameter of 60 to 80 nm, and yet their mode of action requires them to penetrate the fungal cell wall to deliver amphotericin B to the cell membrane, where it binds to ergosterol. Surprisingly, using cryofixation techniques with electron microscopy, we observed that the liposomes remained intact during transit through the cell wall of both yeast species, even though the predicted porosity of the cell wall (pore size, ~5.8 nm) is theoretically too small to allow these liposomes to pass through intact. C. albicans mutants with altered cell wall thickness and composition were similar in both their in vitro AmBisome susceptibility and the ability of liposomes to penetrate the cell wall. AmBisome exposed to ergosterol-deficient C. albicans failed to penetrate beyond the mannoprotein-rich outer cell wall layer. Melanization of C. neoformans and the absence of amphotericin B in the liposomes were also associated with a significant reduction in liposome penetration. Therefore, AmBisome can reach cell membranes intact, implying that fungal cell wall viscoelastic properties are permissive to vesicular structures. The fact that AmBisome can transit through chemically diverse cell wall matrices when these liposomes are larger than the theoretical cell wall porosity suggests that the wall is capable of rapid remodeling, which may also be the mechanism for release of extracellular vesicles. IMPORTANCE AmBisome is a broad-spectrum fungicidal antifungal agent in which the hydrophobic polyene antibiotic amphotericin B is packaged within a 60- to 80-nm liposome. The mode of action involves perturbation of the fungal cell membrane by selectively binding to ergosterol, thereby disrupting membrane function. We report that the AmBisome liposome transits through the cell walls of both Candida albicans and Cryptococcus neoformans intact, despite the fact that the liposome is larger than the theoretical cell wall porosity. This implies that the cell wall has deformable, viscoelastic properties that are permissive to transwall vesicular traffic. These observations help explain the low toxicity of AmBisome, which can deliver its payload directly to the cell membrane without unloading the polyene in the cell wall. In addition, these findings suggest that extracellular vesicles may also be able to pass through the cell wall to deliver soluble and membrane-bound effectors and other molecules to the extracellular space.Louise WalkerPrashant SoodMegan D. LenardonGillian MilneJon OlsonGerard JensenJulie WolfArturo CasadevallJill Adler-MooreNeil A. R. GowAmerican Society for Microbiologyarticleamphotericin Bantifungal drugcell membranesfungal cell wallmannoproteinsMicrobiologyQR1-502ENmBio, Vol 9, Iss 1 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	amphotericin B antifungal drug cell membranes fungal cell wall mannoproteins Microbiology QR1-502
spellingShingle	amphotericin B antifungal drug cell membranes fungal cell wall mannoproteins Microbiology QR1-502 Louise Walker Prashant Sood Megan D. Lenardon Gillian Milne Jon Olson Gerard Jensen Julie Wolf Arturo Casadevall Jill Adler-Moore Neil A. R. Gow The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles
description	ABSTRACT The fungal cell wall is a critically important structure that represents a permeability barrier and protective shield. We probed Candida albicans and Cryptococcus neoformans with liposomes containing amphotericin B (AmBisome), with or without 15-nm colloidal gold particles. The liposomes have a diameter of 60 to 80 nm, and yet their mode of action requires them to penetrate the fungal cell wall to deliver amphotericin B to the cell membrane, where it binds to ergosterol. Surprisingly, using cryofixation techniques with electron microscopy, we observed that the liposomes remained intact during transit through the cell wall of both yeast species, even though the predicted porosity of the cell wall (pore size, ~5.8 nm) is theoretically too small to allow these liposomes to pass through intact. C. albicans mutants with altered cell wall thickness and composition were similar in both their in vitro AmBisome susceptibility and the ability of liposomes to penetrate the cell wall. AmBisome exposed to ergosterol-deficient C. albicans failed to penetrate beyond the mannoprotein-rich outer cell wall layer. Melanization of C. neoformans and the absence of amphotericin B in the liposomes were also associated with a significant reduction in liposome penetration. Therefore, AmBisome can reach cell membranes intact, implying that fungal cell wall viscoelastic properties are permissive to vesicular structures. The fact that AmBisome can transit through chemically diverse cell wall matrices when these liposomes are larger than the theoretical cell wall porosity suggests that the wall is capable of rapid remodeling, which may also be the mechanism for release of extracellular vesicles. IMPORTANCE AmBisome is a broad-spectrum fungicidal antifungal agent in which the hydrophobic polyene antibiotic amphotericin B is packaged within a 60- to 80-nm liposome. The mode of action involves perturbation of the fungal cell membrane by selectively binding to ergosterol, thereby disrupting membrane function. We report that the AmBisome liposome transits through the cell walls of both Candida albicans and Cryptococcus neoformans intact, despite the fact that the liposome is larger than the theoretical cell wall porosity. This implies that the cell wall has deformable, viscoelastic properties that are permissive to transwall vesicular traffic. These observations help explain the low toxicity of AmBisome, which can deliver its payload directly to the cell membrane without unloading the polyene in the cell wall. In addition, these findings suggest that extracellular vesicles may also be able to pass through the cell wall to deliver soluble and membrane-bound effectors and other molecules to the extracellular space.
format	article
author	Louise Walker Prashant Sood Megan D. Lenardon Gillian Milne Jon Olson Gerard Jensen Julie Wolf Arturo Casadevall Jill Adler-Moore Neil A. R. Gow
author_facet	Louise Walker Prashant Sood Megan D. Lenardon Gillian Milne Jon Olson Gerard Jensen Julie Wolf Arturo Casadevall Jill Adler-Moore Neil A. R. Gow
author_sort	Louise Walker
title	The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles
title_short	The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles
title_full	The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles
title_fullStr	The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles
title_full_unstemmed	The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles
title_sort	viscoelastic properties of the fungal cell wall allow traffic of ambisome as intact liposome vesicles
publisher	American Society for Microbiology
publishDate	2018
url	https://doaj.org/article/1d4cb09fdbb94153b48f0ccb07f36441
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The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles

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