N -Acetylglucosamine (GlcNAc)-Inducible Gene GIG2 Is a Novel Component of GlcNAc Metabolism in Candida albicans

Candida albicans is an opportunistic fungal pathogen that resides in the human body as a commensal and can turn pathogenic when the host is immunocompromised. Adaptation ofC. albicans to host niche-specific conditions is important for the establishment of pathogenicity, where the ability ofC. albicans to utilize multiple carbon sources provides additional flexibility. One alternative sugar isN -acetylglucosamine (GlcNAc), which is now established as an important carbon source for many pathogens and can also act as a signaling molecule. Although GlcNAc catabolism has been well studied in many pathogens, the importance of several enzymes involved in the formation of metabolic intermediates still remains elusive. In this context, microarray analysis was carried out to investigate the transcriptional responses induced by GlcNAc under different conditions. A novel gene that was highly upregulated immediately following the GlcNAc catabolic genes was identified and was namedGIG2 (GlcNAc-induced gene 2). This gene is regulated in a manner distinct from that of the GlcNAc-induced genes described previously in that GlcNAc metabolism is essential for its induction. Furthermore, this gene is involved in the metabolism ofN -acetylneuraminate (sialic acid), a molecule equally important for initial host-pathogen recognition. Mutant cells showed a considerable decrease in fungal burden in mouse kidneys and were hypersensitive to oxidative stress conditions. SinceGIG2 is also present in many other fungal and enterobacterial genomes, targeted inhibition of its activity would offer insight into the treatment of candidiasis and other fungal or enterobacterial infections.