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The bZip transcription factor Cap1p is involved in multidrug resistance and oxidative stress response in Candida
1Institut de Recherches Cliniques de Montréal, Montréal, Québec, Canada H2W 1R7.
Abstract:
Candida albicans is an opportunistic pathogenic yeast which frequently develops resistance to the antifungal agent fluconazole (FCZ) in patients undergoing long-term therapy. FCZ-resistant strains often display a reduced intracellular FCZ accumulation which correlates with the overexpression of the ATP-binding cassette transporters CDR1 and CDR2 or the major facilitator (MF) MDR1. We have recently cloned a C. albicans gene, named CAP1, which codes for a bZip transcription factor of the AP-1 family homologous to the Yap1 protein involved in multidrug resistance and response to oxidative stress in Saccharomyces cerevisiae. CAP1 was found to confer FCZ resistance in S. cerevisiae by transcriptionally activating FLR1, a gene coding for an MF homologous to the C. albicans MDR1 gene product (A.-M. Alarco, I. Balan, D. Talibi, N. Mainville, and M. Raymond, J. Biol. Chem. 272:19304-19313, 1997). To study the role of CAP1 in C. albicans, we constructed a CAI4-derived mutant strain carrying a homozygous deletion of the CAP1 gene (CJD21). We found that deletion of CAP1 did not affect the susceptibility of CJD21 cells to FCZ, cerulenin, brefeldin A, and diamide but caused hypersensitivity to cadmium, 4-nitroquinoline N-oxide, 1,10-phenanthroline, and hydrogen peroxide, an effect which was reverted by reintroduction of the CAP1 gene in these cells. Introduction of a hyperactive truncated allele of CAP1 (CAP1-TR) in CJD21 resulted in resistance of the cells to all of the above compounds except hydrogen peroxide. The hyperresistant phenotype displayed by the CJD21 CAP1-TR transformants was found to correlate with the overexpression of a number of potential CAP1 transcriptional targets such as MDR1, CaYCF1, CaGLR1, and CaTRR1. Taken together, our results demonstrate that CAP1 is involved in multidrug resistance and oxidative stress response in C. albicans. Finally, disruption of CAP1 in strain FR2, selected in vitro for FCZ resistance and constitutively overexpressing MDR1, did not suppress but rather increased the levels of MDR1 expression, demonstrating that CAP1 acts as a negative transcriptional regulator of the MDR1 gene in FR2 and is not responsible for MDR1 overexpression in this strain.
Insights
The CAP1 gene in Candida albicans is crucial for multidrug resistance and oxidative stress response. Deleting CAP1 causes hypersensitivity to certain toxins, while its overexpression confers resistance, highlighting its regulatory role.
Area of Science:
- Mycology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Candida albicans frequently develops fluconazole (FCZ) resistance.
- Resistance is linked to ABC transporters (CDR1, CDR2) or MDR1.
- The CAP1 gene encodes a transcription factor homologous to Yap1, involved in stress response.
Purpose of the Study:
- To investigate the role of CAP1 in Candida albicans.
- To understand CAP1's involvement in multidrug resistance and oxidative stress.
Main Methods:
- Constructed a CAP1 deletion mutant (CJD21) in C. albicans.
- Assessed susceptibility to various agents (FCZ, toxins, oxidants).
- Introduced a hyperactive CAP1 allele (CAP1-TR) and analyzed target gene expression.
Main Results:
- CAP1 deletion caused hypersensitivity to cadmium, 4-nitroquinoline N-oxide, 1,10-phenanthroline, and hydrogen peroxide.
- CAP1-TR conferred resistance to these agents, except hydrogen peroxide.
- CAP1 regulates MDR1, CaYCF1, CaGLR1, and CaTRR1 expression.
- CAP1 negatively regulates MDR1 in FCZ-resistant strains.
Conclusions:
- CAP1 is essential for multidrug resistance and oxidative stress response in C. albicans.
- CAP1 acts as a negative regulator of MDR1 in specific resistant strains.