AUTHOR=Van Ende Mieke , Wijnants Stefanie , Van Dijck Patrick 

TITLE=Sugar Sensing and Signaling in Candida albicans and Candida glabrata

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00099

DOI=10.3389/fmicb.2019.00099

ISSN=1664-302X

ABSTRACT=<p><italic>Candida</italic> species, such as <italic>Candida albicans</italic> and <italic>Candida glabrata</italic>, cause infections at different host sites because they adapt their metabolism depending on the available nutrients. They are able to proliferate under both nutrient-rich and nutrient-poor conditions. This adaptation is what makes these fungi successful pathogens. For both species, sugars are very important nutrients and as the sugar level differs depending on the host niche, different sugar sensing systems must be present. <italic>Saccharomyces cerevisiae</italic> has been used as a model for the identification of these sugar sensing systems. One of the main carbon sources for yeast is glucose, for which three different pathways have been described. First, two transporter-like proteins, <italic><underline>Sc</underline></italic>Snf3 and <italic><underline>Sc</underline></italic>Rgt2, sense glucose levels resulting in the induction of different hexose transporter genes. This situation is comparable in <italic>C. albicans</italic> and <italic>C. glabrata</italic>, where sensing of glucose by <italic><underline>Ca</underline></italic>Hgt4 and <italic><underline>Cg</underline></italic>Snf3, respectively, also results in hexose transporter gene induction. The second glucose sensing mechanism in <italic>S. cerevisiae</italic> is via the G-protein coupled receptor <italic><underline>Sc</underline></italic>Gpr1, which causes the activation of the cAMP/PKA pathway, resulting in rapid adaptation to the presence of glucose. The main components of this glucose sensing system are also conserved in <italic>C. albicans</italic> and <italic>C. glabrata</italic>. However, it seems that the ligand(s) for <italic><underline>Ca</underline></italic>Gpr1 are not sugars but lactate and methionine. In <italic>C. glabrata</italic>, this pathway has not yet been investigated. Finally, the glucose repression pathway ensures repression of respiration and repression of the use of alternative carbon sources. This pathway is not well characterized in <italic>Candida</italic> species. It is important to note that, apart from glucose, other sugars and sugar-analogs, such as <italic>N</italic>-acetylglucosamine in the case of <italic>C. albicans</italic>, are also important carbon sources. In these fungal pathogens, sensing sugars is important for a number of virulence attributes, including adhesion, oxidative stress resistance, biofilm formation, morphogenesis, invasion, and antifungal drug tolerance. In this review, the sugar sensing and signaling mechanisms in these <italic>Candida</italic> species are compared to <italic>S. cerevisiae.</italic></p>