Effects of Disruption of PMC1 in the tfp1∆/∆ Mutant on Calcium Homeostasis, Oxidative and Osmotic Stress Resistance in Candida albicans

The Importance of Vacuolar Ion Homeostasis and Trafficking in Hyphal Development and Virulence in Candida albicans

The vacuole of Candida albicans plays a significant role in many processes including homeostasis control, cellular trafficking, dimorphic switching, and stress tolerance. Thus, understanding the factors affecting vacuole function is important for the identification of new drug targets needed in response to the world’s increasing levels of invasive infections and the growing issue of fungal drug resistance. Past studies have shown that vacuolar proton-translocating ATPases (V-ATPases) play a central role in pH homeostasis and filamentation. Vacuolar protein sorting components (VPS) regulate V-ATPases assembly and at the same time affect hyphal development. As well, vacuolar calcium exchange systems like Yvc1 and Pmc1 maintain cytosolic calcium levels while being affected by V-ATPases function. All these proteins play a role in the virulence and pathogenesis of C. albicans. This review highlights the relationships among V-ATPases, VPS, and vacuolar calcium exchange proteins while summarizing their importance in C. albicans infections.

Calcium Transport Proteins in Fungi: The Phylogenetic Diversity of Their Relevance for Growth, Virulence, and Stress Resistance

The key players of calcium (Ca²⁺) homeostasis and Ca²⁺ signal generation, which are Ca²⁺ channels, Ca²⁺/H⁺ antiporters, and Ca²⁺-ATPases, are present in all fungi. Their coordinated action maintains a low Ca²⁺ baseline, allows a fast increase in free Ca²⁺ concentration upon a stimulus, and terminates this Ca²⁺ elevation by an exponential decrease – hence forming a Ca²⁺ signal. In this respect, the Ca²⁺ signaling machinery is conserved in different fungi. However, does the similarity of the genetic inventory that shapes the Ca²⁺ peak imply that if “you’ve seen one, you’ve seen them all” in terms of physiological relevance? Individual studies have focused mostly on a single species, and mechanisms elucidated in few model organisms are usually extrapolated to other species. This mini-review focuses on the physiological relevance of the machinery that maintains Ca²⁺ homeostasis for growth, virulence, and stress responses. It reveals common and divergent functions of homologous proteins in different fungal species. In conclusion, for the physiological role of these Ca²⁺ transport proteins, “seen one,” in many cases, does not mean: “seen them all.”

Harnessing Metal Homeostasis Offers Novel and Promising Targets Against Candida albicans

Fungal infections, particularly of Candida species, which are the commensal organisms of human, are one of the major debilitating diseases in immunocompromised patients. The limited number of antifungal drugs available to treat Candida infections, with the concomitant increasing incidence of multidrug-resistant (MDR) strains, further worsens the therapeutic options. Thus, there is an urgent need for the better understanding of MDR mechanisms, and their reversal, by employing new strategies to increase the efficacy and safety profiles of currently used therapies against the most prevalent human fungal pathogen, Candida albicans. Micronutrient availability during C. albicans infection is regarded as a critical factor that influences the progression and magnitude of the disease. Intracellular pathogens colonize a variety of anatomical locations that are likely to be scarce in micronutrients, as a defense strategy adopted by the host, known as nutritional immunity. Indispensable critical micronutrients are required both by the host and by C. albicans, especially as a cofactor in important metabolic functions. Since these micronutrients are not freely available, C. albicans need to exploit host reservoirs to adapt within the host for survival. The ability of pathogenic organisms, including C. albicans, to sense and adapt to limited micronutrients in the hostile environment is essential for survival and confers the basis of its success as a pathogen. This review describes that micronutrients availability to C. albicans is a key attribute that may be exploited when one considers designing strategies aimed at disrupting MDR in this pathogenic fungi. Here, we discuss recent advances that have been made in our understanding of fungal micronutrient acquisition and explore the probable pathways that may be utilized as targets.