The ABC transporter-encoding geneAFR1affects the resistance ofCryptococcus neoformansto microglia-mediated antifungal activity by delaying phagosomal maturation

Abstract

The pathogenic yeast Cryptococcus neoformans has evolved several strategies to survive within phagocytes. Recently, it has been demonstrated that upregulation of the ATP binding cassette transporter-encoding gene antifungal resistance 1 (AFR1) is important not only for determining the resistance of C. neoformans to fluconazole but also in influencing fungal virulence. In the present study, we showed that the fluconazole-resistant AFR1-overexpressing mutant strain was not sensitive to microglia-mediated anticryptococcal activity, as compared with the fluconazole-susceptible isogenic strains, the wild type and the afr1Delta mutant. Interestingly, although the three strains were phagocytosed to a similar extent, reduced acidification and delayed maturation were observed in phagosomes containing the AFR1-overexpressing strain with respect to the others. These findings provide the first evidence that upregulation of the AFR1 gene affects C. neoformans-microglia interplay, adding insights to the complexity of cryptococcal virulence and to its unexpected link with azole resistance.

Contribution of CgPDR1-Regulated Genes in Enhanced Virulence of Azole-Resistant Candida glabrata

“…For example, the Cryptococcus neoformans ABC transporter AFR1 was shown to interfere with lysosome acidification in macrophages to increase its survival. In particular, azole-resistant isolates showing increased AFR1 expression were more virulent than their parental azole-susceptible isolates [35], [36], [37], which highlights the relevance of the association between drug resistance and virulence observed here. Interestingly, a recent study reported that AFR1 upregulation could be obtained by reversible chromosome duplication and thus suggests C. neoformans could use this mechanism to modulate its virulence [38].…”

ABC proteins in yeast and fungal pathogens

“…ABC transporters in Cryptococcus neoformans are implicated in azole transport, as shown for CnMDR1 by heterologous expression in S. cerevisiae or as in the case of CnAFR1 in C. neoformans directly. Furthermore, interaction studies with a CnAFR1-overexpressing strain and microglia (macrophages residing in the brain) showed reduced acidification and delayed maturation of the phagolysosome [34]. This leads to an interesting connection between azole resistance and virulence, which has also been observed for C. glabrata azole-resistant strains [35].…”

The fungal pathogenCryptococcus neoformansmanipulates macrophage phagosome maturation

“…A lack of cryptococcal killing by human alveolar macrophages in a previous study was hypothesized to be due to a lack of phagosome–lysosome fusion (Vecchiarelli et al ., ). A similar lack of acidification has been seen in microglia cells (specialized phagocytes of the central nervous system), in which only 35% of phagosomes underwent full acidification (Orsi et al ., ).…”