Candida albicans Hxk1 influences expression of metabolic- and virulence-related genes.

Abstract

The Hxk1 protein of Candida albicans phosphorylates N-acetylglucosamine (GlcNAc) which is necessary for various cellular functions, including energy production and chitin synthesis. Further, this protein also regulates morphogenesis independently of its role in GlcNAc catabolism. When HXK1 is deleted, cells are hyperfilamentous on serum-containing medium. Furthermore, Hxk1 translocates to the nucleus in the presence of glucose. To gain a broad understanding of the effect of Hxk1 on gene expression in C. albicans, we performed genome-wide transcriptional profiling of the hxk1 mutant strain by RNA-Seq. The analysis of these RNA-Seq data showed that Hxk1 affects gene expression in both a carbon source-dependent and -independent manner. However, the effect on gene expression occurs via an indirect mechanism, as genome-wide CUT&RUN binding experiments demonstrated that Hxk1 does not bind to the upstream intergenic regions of the differentially expressed genes. Deletion of HXK1 not only resulted in differences in gene expression of genes present in the GlcNAc and galactose regulons, but also in glucose transporter genes, including HGT13. Hxk1 also negatively influences the expression of virulence-associated genes, including HWP1, BRG1, and UME6. Consequently, an hxk1 mutant strain showed higher toxicity toward gut epithelial cells compared to the WT strain. Furthermore, the hxk1 mutant strain had higher expression levels of SOD4 and SOD5 and showed higher resistance toward H₂O₂. These findings highlight the multiple functions of Hxk1 in different cellular processes.IMPORTANCECandida albicans is a fungus that lives in the human body but does not cause any harm in healthy individuals. However, when the immune system is weakened, C. albicans can spread via the bloodstream all over the body and can lead to severe illness and even death. To infect the human body, multiple proteins hold distinct functions. Hxk1 is one of these proteins. This protein is involved in N-acetylglucosamine (GlcNAc) phosphorylation, as well as hyphae formation and glucose transport. To obtain a complete view of the processes regulated by Hxk1, we performed an RNA-Seq experiment. These data revealed that Hxk1 influences the regulation of genes involved in metabolic and virulence-related processes, such as GlcNAc metabolism, sterol metabolism, and oxidative stress resistance. These findings are important to better understand how C. albicans adapted itself to infect the host.