Identification and Functional Analysis of GTP Cyclohydrolase II in Candida glabrata in Response to Nitrosative Stress

Abstract

Reactive nitrogen species (RNS) are signal molecules involved in various biological events; however, excess levels of RNS cause nitrosative stress, leading to cell death and/or cellular dysfunction. During the process of infection, pathogens are exposed to nitrosative stress induced by host-derived RNS. Therefore, the nitrosative stress resistance mechanisms of pathogenic microorganisms are important for their infection and pathogenicity, and could be promising targets for antibiotics. Previously, we demonstrated that theRIB1gene encoding GTP cyclohydrolase II (GCH2), which catalyzes the first step of the riboflavin biosynthesis pathway, is important for nitrosative stress resistance in the yeastSaccharomyces cerevisiae. Here, we identified and characterized theRIB1gene in the opportunistic pathogenic yeastCandida glabrata. Our genetic and biochemical analyses indicated that the open reading frame of CAGL0F04279g functions asRIB1inC. glabrata(CgRIB1). Subsequently, we analyzed the effect ofCgRIB1on nitrosative stress resistance by a growth test in the presence of RNS. Overexpression or deletion ofCgRIB1increased or decreased the nitrosative stress resistance ofC. glabrata, respectively, indicating that GCH2 confers nitrosative stress resistance on yeast cells. Moreover, we showed that the proliferation ofC. glabratain cultures of macrophage-like cells required the GCH2-dependent nitrosative stress detoxifying mechanism. Additionally, an infection assay using silkworms as model host organisms indicated thatCgRIB1is indispensable for the virulence ofC. glabrata. Our findings suggest that the GCH2-dependent nitrosative stress detoxifying mechanism is a promising target for the development of novel antibiotics.