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Significance of differential expression profiles of ABC transporters in azole susceptibility between Cryptococcus
Xinying Xue1,2,3, Xuelei Zang4,5, Meng Xiao6
1Department of Respiratory and Critical Care, Beijing Shijitan Hospital, Capital Medical University; Peking University Ninth School of Clinical Medicine, Haidian District, Beijing 100871, China.
Abstract:
Azoles were used as the primary antifungal agents to treat the Cryptococcus gattii infection. Evidence showed that subtypes of C. gattii respond differently to azoles, but the mechanism is largely elusive. In this study, we aimed to find the mechanisms of differences in azole drug susceptibility in different subtypes of C. gattii. Eight clinical strains of C. gattii were collected for molecular typing, multilocus sequence typing (MLST) analysis, and antifungal susceptibility testing. Based on drug susceptibility differences, the RNA sequencing data were analyzed to find candidate azole drug susceptibility genes, and qPCR validation was performed. Five VGI subtypes and three VGII subtypes were identified among the eight strains of C. gattii. The clinical isolates showed high genetic diversity, and seven sequence types (STs) were identified. The geometric mean (GM) of minimum inhibitory concentration (MIC) for fluconazole, voriconazole, and itraconazole of VGI subtype was significantly lower than that of VGII subtype, and genes related to transporter activities were differentially expressed between VGI and VGII strains. The results of the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs (differential expressed genes) were found to be enriched in multiple ABC transporters. We further performed qPCR to quantify the expression level of seven ABC transporters. We found that ABC transporters ATM1, MDR1, PDR5, PDR5-3, and PXA2 were expressed significantly higher in VGII strains than in VGI strains. Our work revealed four novel ABC transporters, ATM1, PDR5, PDR5-3, and PXA2, promising candidate targets regulating azole susceptibility in C. gattii strains.
Lay Summary:
Azoles were used as the primary antifungal agents for treating Cryptococuss gattii infection. Since subtypes of C. gattii respond differently to azoles. We analyzed mRNA expression profiles of different subtypes and identified four ABC transporters that could be potential genes regulating azole sensitivity.
Insights
Cryptococcus gattii subtypes show varied azole antifungal drug susceptibility. Researchers identified specific ABC transporter genes that are highly expressed in less susceptible strains, offering potential new drug targets.
Area of Science:
- Mycology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Azoles are key antifungals for Cryptococcus gattii infections.
- Distinct C. gattii subtypes exhibit differential responses to azole treatments.
- The underlying molecular mechanisms for this varied susceptibility remain largely unknown.
Purpose of the Study:
- To elucidate the molecular mechanisms behind differential azole drug susceptibility in C. gattii subtypes.
- To identify specific genes and pathways involved in azole resistance in different C. gattii strains.
Main Methods:
- Collected and characterized eight clinical C. gattii strains using molecular typing and multilocus sequence typing (MLST).
- Performed antifungal susceptibility testing to determine Minimum Inhibitory Concentrations (MICs) for azoles.
- Conducted RNA sequencing to analyze differential gene expression between susceptible and resistant subtypes.
- Validated key differentially expressed genes, focusing on ABC transporters, using quantitative PCR (qPCR).
Main Results:
- Identified five VGI and three VGII C. gattii subtypes with significant genetic diversity.
- Demonstrated significantly lower azole MICs for the VGI subtype compared to the VGII subtype.
- Revealed differential expression of transporter activity genes, particularly ABC transporters, between VGI and VGII strains.
- Quantified higher expression of ABC transporters ATM1, MDR1, PDR5, PDR5-3, and PXA2 in the less susceptible VGII strains.
Conclusions:
- The study highlights significant differences in azole susceptibility between C. gattii VGI and VGII subtypes.
- Differential expression of specific ABC transporters is a key mechanism contributing to varied azole drug responses.
- Four novel ABC transporters (ATM1, PDR5, PDR5-3, PXA2) are identified as promising targets for understanding and potentially overcoming azole resistance in C. gattii.
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