Cryptococcus neoformans Yop1 , an endoplasmic reticulum curvature-stabilizing protein, participates with Sey1 in influencing fluconazole-induced disomy formation.
ABSTRACT Cryptococcus neoformans, an opportunistic fungal pathogen, manifests an intrinsic adaptive mechanism of resistance toward fluconazole (FLC) termed heteroresistance. Heteroresistance is characterized by the emergence of minor resistant subpopulations at levels of FLC that are higher than the strain's minimum inhibitory concentration. The heteroresistant clones that tolerate high concentrations of FLC often contain disomic chromosome 4 (Chr4). SEY1 , GLO3 , and GCS2 on Chr4 are responsible for endoplasmic reticulum (ER) integrity and important for Chr4 disomy formation under FLC stress. We sought an evidence of a direct relationship between ER morphology and Chr4 disomy formation. Deletion of the YOP1 gene on Chr7, which encodes an ER curvature-stabilizing protein that interacts with Sey1 , perturbed ER morphology without affecting FLC susceptibility or the frequency of FLC-induced disomies. However, deletion of both YOP1 and SEY1 , not only perturbed ER morphology more severely than in sey1∆ or yop1∆ strains, but also abrogated the FLC-induced disomy. Although the heteroresistance phenotype was retained in the sey1∆yop1∆ strains, tolerance to FLC appeared to have resulted not from chromosome duplication but from gene amplification restricted to the region surrounding ERG11 on Chr1. These data support the importance of ER integrity in C. neoformans for the formation of disomy under FLC stress.
- SourceAvailable from: Kyung J Kwon-ChungPLoS Pathogens 11/2012; 8(11):e1003022. · 8.06 Impact Factor
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ABSTRACT: Changes in ploidy have a profound and usually negative influence on cellular viability and proliferation, yet the vast majority of cancers and tumours exhibit an aneuploid karyotype. Whether this genomic plasticity is a cause or consequence of malignant transformation remains uncertain. Systemic fungal pathogens regularly develop aneuploidies in a similar manner during human infection, often far in excess of the natural rate of chromosome nondisjunction. As both processes fundamentally represent cells evolving under selective pressures, this suggests that changes in chromosome number may be a concerted mechanism to adapt to the hostile host environment. Here, we examine the mechanisms by which aneuploidy and polyploidy are generated in the fungal pathogens Candida albicans and Cryptococcus neoformans and investigate whether these represent an adaptive strategy under severe stress through the rapid generation of large-scale mutations. Insights into fungal ploidy changes, strategies for tolerating aneuploidies and proliferation during infection may yield novel targets for both antifungal and anticancer therapies.Seminars in Cell and Developmental Biology 02/2013; · 6.20 Impact Factor