Requirement of a putative mitochondrial GTPase, GemA, for azole susceptibility, virulence, and cell wall integrity in Aspergillus fumigatus

Abstract

Drug resistance in fungal pathogens is a new challenge in clinical aspergillosis treatment. Mitochondria as dynamic organelles are involved in numerous biological processes in fungi, including drug resistance. However, little is known about the mechanism underlying mitochondrial regulation of the response of fungal pathogens to antifungal drugs. Here, we showed that a putative mitochondrial GTPase, GemA, a yeast Gem1 homolog, is crucial for the azole response and cell wall integrity in the opportunistic pathogen Aspergillus fumigatus. The fluorescence observation showed that GFP-labeled GemA is located in mitochondria, and loss of gemA results in aberrant giant mitochondrial morphology and abnormal mitochondrial membrane potential. Moreover, a ΔgemA mutant attenuates fungal virulence in the Galleria mellonella model of aspergillosis. Furthermore, gemA loss increases resistance to azoles and terbinafine but not to amphotericin B. Of note, RNA-seq combined with RT-qPCR showed that a series of drug efflux pumps were upregulated in the gemA deletion mutant. Deleting mdr1 or inhibiting the expression of drug efflux pumps can partially decrease the resistance to azoles resulting from the gemA mutant, implying that GemA influences azole response by affecting the expression of drug efflux pumps. Importantly, the ΔgemA mutant is susceptible to the cell wall-perturbing reagent CR, but not to CFW, and this defect can be partly rescued by hyperosmotic stress. TEM revealed that the cell wall of ΔgemA was thicker than that of the WT strain, demonstrating that GemA plays a role in cell wall composition and integrity. Collectively, we identified a putative mitochondrial GTPase, GemA, which is critical for hyphal growth, virulence, azole susceptibility, and cell wall integrity and acts by affecting mitochondrial function.

The metal chaperone protein MtmA plays important roles in antifungal drug susceptibility in Aspergillus fumigatus

“…As an organelle necessary for energy production in eukaryotic cells, mitochondria are involved in a series of metabolic processes, such as apoptosis, Ca 2+ homeostasis, and lipid and other metabolite biosynthesis (Vakifahmetoglu-Norberg et al, 2017;Akbari et al, 2019;Rossi et al, 2019). Currently, much evidence suggests that the integrity of mitochondrial function plays an important role in susceptibility to azole antifungal drugs (Neubauer et al, 2015;Li et al, 2020;Zhou et al, 2022). Here, phenotypic analysis revealed that repression of MtmA expression resulted in significant resistance to the azole drug itraconazole (Figure 1).…”

“…Recent studies have shown that pathogenic fungi adopt an adaptive strategy to reduce mitochondrial metabolic function in response to antifungal drug adversity (Li et al, 2020). Moreover, studies have shown that the expression of mitochondria-related genes is closely associated with the resistance of pathogenic fungi to antifungal azoles (Neubauer et al, 2015;Li et al, 2020;Zhou et al, 2022). Mitochondria are involved not only in many biological processes as energy factories but also as intracellular Ca 2+ stores capable of participating in the response to external stimuli (Ganitkevich, 2003).…”

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

“…Recently, the yeast Gem1 homolog was isolated as GemA in A . fumigatus and was shown to be required for azole susceptibility, hyphal growth, virulence, and cell wall integrity [ 37 ].…”