In Candida glabrata, ERMES Component GEM1 Controls Mitochondrial Morphology, mtROS, and Drug Efflux Pump Expression, Resulting in Azole Susceptibility

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 ∆gem1 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.

Genome‐wide profiling of piggyBac transposon insertion mutants reveals loss of the F1F0 ATPase complex causes fluconazole resistance in Candida glabrata

“…However, F 1 complex dysfunction did not contribute to the increased cycloheximide tolerance (Zhang & Moye‐Rowley, 2001). Acquired azole resistance in C. glabrata has been linked to mitochondrial dysfunction, although the underlying molecular mechanism is unclear (Defontaine et al., 1999; Ferrari et al., 2011; Gale et al., 2023; Okamoto et al., 2023; Sanglard et al., 2001). In a separate report, Gale et al.…”

“…The authors put forth an alternative hypothesis that Pdr1 functions as an indirect sensor of cellular stresses, rather than a direct sensor of xenobiotic stress. A recent study hypothesized that it is the increased mitochondrial ROS levels arising from mitochondrial dysfunction that leads to Pdr1‐dependent upregulation of efflux pumps (Okamoto et al., 2023). It has previously been shown that azoles localize to the mitochondria of C. albicans (Benhamou et al., 2017) and that C. glabrata gains transient fluconazole resistance through reversible loss of mitochondrial function (Kaur et al., 2004).…”

Mitochondrial Reactive Oxygen Species in Infection and Immunity

“…Elevated mt-ROS is also implicated in acquiring drug resistance, for instance in Candida glabrata -azole resistance. A deficiency in the ERMES (ER-mitochondrial encounter structure) component GEM-1 leads to mt-ROS generation, along with mitochondrial dysfunction and azole efflux pump upregulation, leading to azole resistance [ 177 ]. Fungal mitochondria have a completely different take when inducing pathogenicity.…”

Evaluation of Antifungal Selective Toxicity Using Candida glabrata ERG25 and Human SC4MOL Knock-In Strains

“…In the case of C. glabrata, the primary mechanism driving azole resistance involves the upregulation of efflux pumps, particularly CDR1, which is mediated by a transcription factor, PDR1 [17][18][19][20][21][22][23][24]. Other studies have also highlighted that azole resistance coincides with stress induced by mitochondrial loss or dysfunction, leading to the activation of PDR1, and subsequently, the upregulation of CDR1 [25][26][27][28][29][30]. Furthermore, as a strategy for azole resistance in C. glabrata, our attention has been directed towards the role of host cholesterol uptake.…”