Potassium Uptake Mediated by Trk1 Is Crucial for Candida glabrata Growth and Fitness.

Vicent Llopis-Torregrosa,Barbora Hušeková,Hana Sychrová,Graça Soveral

doi:10.1371/journal.pone.0153374

Vicent Llopis-Torregrosa, Barbora Hušeková + Show 2 more

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https://doi.org/10.1371/journal.pone.0153374

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Abstract

The maintenance of potassium homeostasis is crucial for all types of cells, including Candida glabrata. Three types of plasma-membrane systems mediating potassium influx with different transport mechanisms have been described in yeasts: the Trk1 uniporter, the Hak cation-proton symporter and the Acu ATPase. The C. glabrata genome contains only one gene encoding putative system for potassium uptake, the Trk1 uniporter. Therefore, its importance in maintaining adequate levels of intracellular potassium appears to be critical for C. glabrata cells. In this study, we first confirmed the potassium-uptake activity of the identified gene’s product by heterologous expression in a suitable S. cerevisiae mutant, further we generated a corresponding deletion mutant in C. glabrata and analysed its phenotype in detail. The obtained results show a pleiotropic effect on the cell physiology when CgTRK1 is deleted, affecting not only the ability of trk1Δ to grow at low potassium concentrations, but also the tolerance to toxic alkali-metal cations and cationic drugs, as well as the membrane potential and intracellular pH. Taken together, our results find the sole potassium uptake system in C. glabrata cells to be a promising target in the search for its specific inhibitors and in developing new antifungal drugs.

Highlights

Candida glabrata is considered to be part of the human mycobiome in healthy individuals, even though in recent decades it has become a major fungal opportunistic pathogen, especially in immunocompromised patients [1,2,3]
In order to confirm the predicted potassium uptake function of the C. glabrata CAGL0L05654g gene’s product, we first utilised the heterologous expression of CgTRK1 in the S. cerevisiae BYT12 strain, lacking endogenous plasma-membrane potassium transporters and known to exhibit an affected growth rate under potassium-limiting conditions
As shown in comparative growth tests (Fig 1B), the presence of YEp-CgTRK1 was clearly able to improve the growth of BYT12 in media with limiting KCl concentrations, showing that the heterologous expression of CgTrk1 complements the growth deficiency of the BYT12 strain at low potassium concentrations, reaching similar levels to those observed for the wild type

Summary

Introduction

Candida glabrata is considered to be part of the human mycobiome in healthy individuals, even though in recent decades it has become a major fungal opportunistic pathogen, especially in immunocompromised patients [1,2,3]. The rise in the relative incidence of C. glabrata is due to its intrinsic high tolerance to most existing antifungal drugs [5], resulting in complications in the treatment of infections. For this reason, the identification of new molecular targets for drug development is an important field of research, focusing on finding new ways to kill this pathogenic yeast.

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