Sugar Phosphorylation Controls Carbon Source Utilization and Virulence of Candida albicans

Abstract

Candida albicans is an opportunistic human fungal pathogen that relies upon different virulence traits, including morphogenesis, invasion, biofilm formation, and nutrient acquisition from host sources as well as metabolic adaptations during host invasion. In this study, we show how sugar kinases at the start of glycolysis modulate virulence of C. albicans. Sequence comparison with Saccharomyces cerevisiae identified four enzymes (Hxk1, Hxk2, Glk1, and Glk4) in C. albicans with putative roles in sugar phosphorylation. Hxk2, Glk1, and Glk4 demonstrate a critical role in glucose metabolism, while Hxk2 is the only kinase important for fructose metabolism. Additionally, we show that Hxk1 controls HXK2, GLK1, and GLK4 expression in the presence of fermentable as well as non-fermentable carbon sources, thereby indirectly controlling glycolysis. Moreover, these sugar kinases are important during virulence. Disabling the glycolytic pathway reduces adhesion capacity, while deletion of HXK1 decreases biofilm formation. Finally, we demonstrate that hxk2 / glk1 / glk4 / and hxk1 / hxk2 / glk1 / glk4 / have attenuated virulence upon systemic infections in mice. These results indicate a regulatory role for Hxk1 during sugar phosphorylation. Furthermore, these kinases are essential during growth on glucose or fructose, and C. albicans relies on a functional glycolytic pathway for maximal virulence.

Candida albicans Hexokinase 2 Challenges the Saccharomyces cerevisiae Moonlight Protein Model

“…In a previous study [ 13 ], we showed that the hexokinase Ca Hxk2 is essential for fitness and virulence in C. albicans , which was reconfirmed by the work of Wijnants et al [ 14 ]. Glucose phosphorylation by Ca Hxk2 is not only necessary for glucose metabolism, but is also a key step for filamentation, stress response, macrophage and Galleria melonnella infection [ 13 ].…”

Neofunctionalization of Glycolytic Enzymes: An Evolutionary Route to Plant Parasitism in the Oomycete Phytophthora nicotianae

“…The occurrence of several hexose kinases is common among living organisms. Hence, higher plants and fungi generally possess both hexokinases and glucokinases, where they catalyze the first step of glucose metabolism but also play a major role in glucose sensing signal transduction, development, growth, cell death, and hormone pathways [90][91][92], with distinct enzymatic properties and even separate functions [93][94][95][96]. In these cases, glucokinases may even be devoid of catalytic activity, whereas the canonical hexose activity is mediated by the hexokinase.…”

CRISPR-Based Genetic Manipulation of Candida Species: Historical Perspectives and Current Approaches

“…While the gene drive platform allows for rapid, high-throughput generation of mutant libraries in C. albicans , CRISPR-Cas9 also enables the generation of higher-order mutants beyond pairwise gene mutations. Recent work by Wijnants et al used CRISPR-Cas9 to characterize putative sugar phosphorylation genes in this manner, demonstrating how different combinations of genes affected cell metabolism and virulence in a murine model (Wijnants et al, 2020 ). Double, triple, and quadruple mutants of putative C. albicans sugar kinase genes ( HXK1, HXK2, GLK1 , and GLK4 ), were generated using a CRISPR marker-recycling system.…”

“…Meanwhile, hxk1 mutants formed the weakest biofilms, despite comparable adhesion levels to the wild type. The reduced virulence of all the other hxk1 mutants, given their weak biofilm formation but hyperfilamentous phenotypes, alludes to the interplay between morphogenesis and glycolytic metabolism in orchestrating a systemic infection (Wijnants et al, 2020 ). This is a powerful study that used higher-order mutants to decouple adherence mechanisms, robust biofilm formation, and virulence, which provides clearer insight into multiple interconnected pathways in C. albicans .…”