title: β-(1,3)-Glucan Unmasking in Some Candida albicans Mutants Correlates with Increases in Cell Wall Surface Roughness and Decreases in Cell Wall Elasticity.
abstract: Candida albicans is among the most common human fungal pathogens, causing a broad range of infections, including life-threatening systemic infections. The cell wall of C. albicans is the interface between the fungus and the innate immune system. The cell wall is composed of an outer layer enriched in mannosylated glycoproteins (mannan) and an inner layer enriched in β-(1,3)-glucan and chitin. Detection of C. albicans by Dectin-1, a C-type signaling lectin specific for β-(1,3)-glucan, is important for the innate immune system to recognize systemic fungal infections. Increased exposure of β-(1,3)-glucan to the immune system occurs when the mannan layer is altered or removed in a process called unmasking. Nanoscale changes to the cell wall during unmasking were explored in live cells with atomic force microscopy (AFM). Two mutants, the cho1Δ/Δ and kre5Δ/Δ mutants, were selected as representatives that exhibit modest and strong unmasking, respectively. Comparisons of the cho1Δ/Δ and kre5Δ/Δ mutants to the wild type reveal morphological changes in their cell walls that correlate with decreases in cell wall elasticity. In addition, AFM tips functionalized with Dectin-1 revealed that the forces of binding of Dectin-1 to all of the strains were similar, but the frequency of binding was highest for the kre5Δ/Δ mutant, decreased for the cho1Δ/Δ mutant, and rare for the wild type. These data show that nanoscale changes in surface topology are correlated with increased Dectin-1 adhesion and decreased cell wall elasticity. AFM, using tips functionalized with immunologically relevant molecules, can map epitopes of the cell wall and increase our understanding of pathogen recognition by the immune system.
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA.
authors.forename: Sahar
authors.initials: S
authors.lastname: Hasim
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.|Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Allison
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.|Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
authors.forename: Scott T
authors.initials: ST
authors.lastname: Retterer
authors.affiliation: Department of Molecular and Biomedical Sciences, University of Maine, Orono, Maine, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Hopke
authors.affiliation: Department of Molecular and Biomedical Sciences, University of Maine, Orono, Maine, USA.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Wheeler
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.|Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
authors.forename: Mitchel J
authors.initials: MJ
authors.lastname: Doktycz
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA treynol6@utk.edu.
authors.forename: Todd B
authors.initials: TB
authors.lastname: Reynolds
mesh_terms: D002176:Candida albicans / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D002473:Cell Wall / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D002686:Chitin / Q000378:metabolism; D004548:Elasticity / Q000502:physiology*; D037181:Lectins, C-Type / Q000378:metabolism; D008351:Mannans / Q000378:metabolism; D009154:Mutation / Q000276:immunology / Q000502:physiology; D047071:beta-Glucans / Q000378:metabolism*; D000099181:Dectin-1
chemical_list: D002686:Chitin; D037181:Lectins, C-Type; D008351:Mannans; D047071:beta-Glucans; D000099181:Dectin-1
keywords: Candida albicans; Dectin-1; Young's modulus; adhesion force mapping; atomic force microscopy; caspofungin; elasticity; gelatin immobilization; indentation force mapping; macrophages; β-(1,3)-glucan