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Candida albicans-epithelial interactions: dissecting the roles of active penetration, induced endocytosis and host factors on the infection process.

Wächtler B, Citiulo F, Jablonowski N, Förster S, Dalle F, Schaller M, Wilson D, Hube B - PLoS ONE (2012)

Bottom Line: Here we investigated the contributions of the two invasion routes of C. albicans to epithelial invasion.Using selective cellular inhibition approaches and differential fluorescence microscopy, we demonstrate that induced endocytosis contributes considerably to the early time points of invasion, while active penetration represents the dominant epithelial invasion route.Although induced endocytosis depends mainly on Als3-E-cadherin interactions, we observed E-cadherin independent induced endocytosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology-Hans Knoell Institute Jena (HKI), Jena, Germany.

ABSTRACT
Candida albicans frequently causes superficial infections by invading and damaging epithelial cells, but may also cause systemic infections by penetrating through epithelial barriers. C. albicans is a remarkable pathogen because it can invade epithelial cells via two distinct mechanisms: induced endocytosis, analogous to facultative intracellular enteropathogenic bacteria, and active penetration, similar to plant pathogenic fungi. Here we investigated the contributions of the two invasion routes of C. albicans to epithelial invasion. Using selective cellular inhibition approaches and differential fluorescence microscopy, we demonstrate that induced endocytosis contributes considerably to the early time points of invasion, while active penetration represents the dominant epithelial invasion route. Although induced endocytosis depends mainly on Als3-E-cadherin interactions, we observed E-cadherin independent induced endocytosis. Finally, we provide evidence of a protective role for serum factors in oral infection: human serum strongly inhibited C. albicans adhesion to, invasion and damage of oral epithelial cells.

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Contributions of fungal invasins, induced endocytosis and active penetration to C. albicans oral epithelial invasion.(A and B) Untreated or thimerosal-inactivated C. albicans cells were co-incubated with either untreated or cytochalasin D treated TR-146 oral epithelial cells for 2 h (A) and 3 h (B). After fixation, the samples were differentially stained and analyzed by fluorescence microscopy. The experiment was performed at least two times in duplicates. */**, indicates significant difference compared to the corresponding wild type control (Wt) (p<0.05/p<0.01, respectively). (C) Micrographs of invading hyphae. C. albicans appears blue (calcofluor white), with extracellular section of the hypha stained red (Concanavalin A); epithelial cells are stained yellow (Dil). Upper panel: a living hypha penetrating through several epithelial cells. Lower panel: a killed hypha, fully phagocytosed by an epithelial cell. Only viable hyphae are able to undergo inter-epithelial invasion. Numbers indicate the number of invaded epithelial cells and arrows mark internalized cells. Scale bar = 10 µm.
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pone-0036952-g002: Contributions of fungal invasins, induced endocytosis and active penetration to C. albicans oral epithelial invasion.(A and B) Untreated or thimerosal-inactivated C. albicans cells were co-incubated with either untreated or cytochalasin D treated TR-146 oral epithelial cells for 2 h (A) and 3 h (B). After fixation, the samples were differentially stained and analyzed by fluorescence microscopy. The experiment was performed at least two times in duplicates. */**, indicates significant difference compared to the corresponding wild type control (Wt) (p<0.05/p<0.01, respectively). (C) Micrographs of invading hyphae. C. albicans appears blue (calcofluor white), with extracellular section of the hypha stained red (Concanavalin A); epithelial cells are stained yellow (Dil). Upper panel: a living hypha penetrating through several epithelial cells. Lower panel: a killed hypha, fully phagocytosed by an epithelial cell. Only viable hyphae are able to undergo inter-epithelial invasion. Numbers indicate the number of invaded epithelial cells and arrows mark internalized cells. Scale bar = 10 µm.

Mentions: In agreement with previous studies [9], [19], killed hyphae (induced endocytosis only) were internalized by oral epithelial cells in a time dependent manner (Wt, Thimerosal, Fig. 2A and B). Occasionally, we observed both viable and killed hyphae which had been entirely internalized (Fig. 2C), demonstrating that induced endocytosis can result in complete uptake of C. albicans. Indeed, a noteworthy proportion of killed hyphae were internalized (2.5 and 12.2% at 2 and 3 h, respectively – Fig. 2A and B Wt, Thimerosal); however, the comparative invasion potential of untreated living fungi was much higher (32.7 and 69.4% at 2 and 3 h, respectively – control, Fig. 2A and B). As described previously, we did not observe internalization of killed yeast cells; these cells remained on the epithelial surface ([9] and data not shown).


Candida albicans-epithelial interactions: dissecting the roles of active penetration, induced endocytosis and host factors on the infection process.

Wächtler B, Citiulo F, Jablonowski N, Förster S, Dalle F, Schaller M, Wilson D, Hube B - PLoS ONE (2012)

Contributions of fungal invasins, induced endocytosis and active penetration to C. albicans oral epithelial invasion.(A and B) Untreated or thimerosal-inactivated C. albicans cells were co-incubated with either untreated or cytochalasin D treated TR-146 oral epithelial cells for 2 h (A) and 3 h (B). After fixation, the samples were differentially stained and analyzed by fluorescence microscopy. The experiment was performed at least two times in duplicates. */**, indicates significant difference compared to the corresponding wild type control (Wt) (p<0.05/p<0.01, respectively). (C) Micrographs of invading hyphae. C. albicans appears blue (calcofluor white), with extracellular section of the hypha stained red (Concanavalin A); epithelial cells are stained yellow (Dil). Upper panel: a living hypha penetrating through several epithelial cells. Lower panel: a killed hypha, fully phagocytosed by an epithelial cell. Only viable hyphae are able to undergo inter-epithelial invasion. Numbers indicate the number of invaded epithelial cells and arrows mark internalized cells. Scale bar = 10 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3351431&req=5

pone-0036952-g002: Contributions of fungal invasins, induced endocytosis and active penetration to C. albicans oral epithelial invasion.(A and B) Untreated or thimerosal-inactivated C. albicans cells were co-incubated with either untreated or cytochalasin D treated TR-146 oral epithelial cells for 2 h (A) and 3 h (B). After fixation, the samples were differentially stained and analyzed by fluorescence microscopy. The experiment was performed at least two times in duplicates. */**, indicates significant difference compared to the corresponding wild type control (Wt) (p<0.05/p<0.01, respectively). (C) Micrographs of invading hyphae. C. albicans appears blue (calcofluor white), with extracellular section of the hypha stained red (Concanavalin A); epithelial cells are stained yellow (Dil). Upper panel: a living hypha penetrating through several epithelial cells. Lower panel: a killed hypha, fully phagocytosed by an epithelial cell. Only viable hyphae are able to undergo inter-epithelial invasion. Numbers indicate the number of invaded epithelial cells and arrows mark internalized cells. Scale bar = 10 µm.
Mentions: In agreement with previous studies [9], [19], killed hyphae (induced endocytosis only) were internalized by oral epithelial cells in a time dependent manner (Wt, Thimerosal, Fig. 2A and B). Occasionally, we observed both viable and killed hyphae which had been entirely internalized (Fig. 2C), demonstrating that induced endocytosis can result in complete uptake of C. albicans. Indeed, a noteworthy proportion of killed hyphae were internalized (2.5 and 12.2% at 2 and 3 h, respectively – Fig. 2A and B Wt, Thimerosal); however, the comparative invasion potential of untreated living fungi was much higher (32.7 and 69.4% at 2 and 3 h, respectively – control, Fig. 2A and B). As described previously, we did not observe internalization of killed yeast cells; these cells remained on the epithelial surface ([9] and data not shown).

Bottom Line: Here we investigated the contributions of the two invasion routes of C. albicans to epithelial invasion.Using selective cellular inhibition approaches and differential fluorescence microscopy, we demonstrate that induced endocytosis contributes considerably to the early time points of invasion, while active penetration represents the dominant epithelial invasion route.Although induced endocytosis depends mainly on Als3-E-cadherin interactions, we observed E-cadherin independent induced endocytosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology-Hans Knoell Institute Jena (HKI), Jena, Germany.

ABSTRACT
Candida albicans frequently causes superficial infections by invading and damaging epithelial cells, but may also cause systemic infections by penetrating through epithelial barriers. C. albicans is a remarkable pathogen because it can invade epithelial cells via two distinct mechanisms: induced endocytosis, analogous to facultative intracellular enteropathogenic bacteria, and active penetration, similar to plant pathogenic fungi. Here we investigated the contributions of the two invasion routes of C. albicans to epithelial invasion. Using selective cellular inhibition approaches and differential fluorescence microscopy, we demonstrate that induced endocytosis contributes considerably to the early time points of invasion, while active penetration represents the dominant epithelial invasion route. Although induced endocytosis depends mainly on Als3-E-cadherin interactions, we observed E-cadherin independent induced endocytosis. Finally, we provide evidence of a protective role for serum factors in oral infection: human serum strongly inhibited C. albicans adhesion to, invasion and damage of oral epithelial cells.

Show MeSH
Related in: MedlinePlus