Enterocytes'tight junctions play a protective role in limiting invasion of Candida albicans into intestinal cells

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Goyer, Marianne | Albac, Sandrine | Thenet, Sophie | Bon, Fabienne | Dalle, Frédéric

Edité par CCSD -

EA MERS CT3 EJ3. National audience. C. albicans is a commensal yeast of the mucous membranes in healthy humans that can also be responsible for disseminated candidiasis, mainly originating from the digestive tract in vulnerable patients. Deciphering the cellular and molecular mechanisms of the interaction of C. albicans with enterocytes is necessary to better understand the basis of commensalism and pathogenicity of the yeast and to improve the management of disseminated candidiasis. In intestinal epithelia, E-cadherin is constitutive of the Adherens Junctions localized just below the Tight Junctions (TJs) which ensure impermeability of the intestinal barrier. We hypothesized the absence of endocytosis of C. albicans in enterocytes could result from inaccessibility of C. albicans to E-cadherin blocked by TJs. We conducted experiments aimed at studying the kinetics of TJs formation in parallel with invasion of the intestinal cell line Caco-2 by C. albicans. Invasion of C. albicans in either non differentiated enterocytes (i.e. without TJs) or differentiated Caco-2 cells with chemically altered TJs was also investigated. Enterocytes were further treated with endocytosis inhibitors in order to determine whether accessibility of C. albicans to E-cadherin in Caco-2 cells could trigger endocytosis of the yeast. Our results reported an increase in invasion of C. albicans in both non differentiated Caco-2 cells and differentiated Caco-2 cells with chemically altered TJs, suggesting that TJs play a crucial role in limiting invasion of the enterocytes by the fungus. Moreover, using pharmacological inhibitors of endocytosis, we observed a decrease in the invasion of Caco-2 cells with chemically altered TJs by C. albicans, suggesting that facilitating access of the yeast to the basolateral side of the epithelial cells promote endocytosis of C. albicans. These data were confirmed with SEM observations of C. albicans interacting with differentiated Caco-2 cells with chemically altered TJs, showing membranes’ protrusions suggestive of endocytic internalization of C. albicans. Involvement of E-cadherin in endocytosis of C. albicans by intestinal cells is currently under investigations using mAbs anti-E-cadherin aimed at blocking E-cadherin at different stages of differentiation of Caco-2 cells. In addition, experiments using KO mutants of C. albicans will be conducted aimed at specifying the molecules of the fungus involved in these processes.

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