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In Candida glabrata, ERMES Component GEM1 Controls Mitochondrial Morphology, mtROS, and Drug Efflux Pump Expression,
Michiyo Okamoto1, Keiko Nakano1, Azusa Takahashi-Nakaguchi1
1Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan.
Abstract:
Mitochondrial dysfunction or morphological abnormalities in human pathogenic fungi are known to contribute to azole resistance; however, the underlying molecular mechanisms are unknown. In this study, we investigated the link between mitochondrial morphology and azole resistance in Candida glabrata, which is the second most common cause of human candidiasis worldwide. The ER-mitochondrial encounter structure (ERMES) complex is thought to play an important role in the mitochondrial dynamics necessary for mitochondria to maintain their function. Of the five components of the ERMES complex, deletion of GEM1 increased azole resistance. Gem1 is a GTPase that regulates the ERMES complex activity. Point mutations in GEM1 GTPase domains were sufficient to confer azole resistance. The cells lacking GEM1 displayed abnormalities in mitochondrial morphology, increased mtROS levels, and increased expression of azole drug efflux pumps encoded by CDR1 and CDR2. Interestingly, treatment with N-acetylcysteine (NAC), an antioxidant, reduced ROS production and the expression of CDR1 in Δgem1 cells. Altogether, the absence of Gem1 activity caused an increase in mitochondrial ROS concentration, leading to Pdr1-dependent upregulation of the drug efflux pump Cdr1, resulting in azole resistance.
Insights
The absence of Gem1 protein in Candida glabrata leads to increased azole resistance by causing mitochondrial abnormalities and boosting drug efflux pump expression. This finding sheds light on fungal drug resistance mechanisms.
Area of Science:
- Mycology
- Molecular Biology
- Biochemistry
Background:
- Mitochondrial dysfunction is linked to azole resistance in pathogenic fungi.
- The molecular basis for this connection remains largely unknown.
- Candida glabrata is a significant cause of human candidiasis globally.
Purpose of the Study:
- To investigate the relationship between mitochondrial morphology and azole resistance in Candida glabrata.
- To elucidate the molecular mechanisms underlying azole resistance in this fungal pathogen.
Main Methods:
- Investigated the role of the ER-mitochondrial encounter structure (ERMES) complex, specifically the GEM1 gene.
- Generated gene deletion and point mutants in GEM1.
- Assessed mitochondrial morphology, mitochondrial reactive oxygen species (mtROS) levels, and expression of drug efflux pumps (CDR1, CDR2).
- Utilized antioxidant treatment (N-acetylcysteine) to evaluate the role of ROS.
Main Results:
- Deletion of GEM1 significantly increased azole resistance in Candida glabrata.
- GEM1 GTPase domain mutations were sufficient to confer azole resistance.
- gem1 deletion mutants exhibited abnormal mitochondrial morphology, elevated mtROS, and increased CDR1/CDR2 expression.
- Antioxidant treatment reduced ROS and CDR1 expression in gem1 deletion mutants.
Conclusions:
- Gem1 absence disrupts mitochondrial morphology and increases mitochondrial ROS.
- Elevated ROS triggers Pdr1-dependent upregulation of the Cdr1 efflux pump, conferring azole resistance.
- Targeting Gem1 or ROS pathways could offer new strategies against azole-resistant fungal infections.
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