-Acetylglucosamine Metabolism Promotes Survival of in the Phagosome.

Phagocytosis by innate immune cells is one of the most effective barriers against the multiplication and dissemination of microbes within the mammalian host. , a pathogenic yeast, has robust mechanisms that allow survival upon macrophage phagocytosis. survives in part because it can utilize the alternative carbon sources available in the phagosome, including carboxylic acids and amino acids. Furthermore, metabolism of these compounds raises the pH of the extracellular environment, which combats the acidification and maturation of the phagolysosome. In this study, we demonstrate that metabolism by of an additional carbon source, -acetylglucosamine (GlcNAc), facilitates neutralization of the phagosome by a novel mechanism. Catabolism of GlcNAc raised the ambient pH through release of ammonia, which is distinct from growth on carboxylic acids but similar to growth on amino acids. However, the effect of GlcNAc metabolism on pH was genetically distinct from the neutralization induced by catabolism of amino acids, as mutation of or did not impair the effects of GlcNAc. In contrast, mutants lacking the dedicated GlcNAc transporter gene or the enzymes responsible for catabolism of GlcNAc were defective in altering the pH of the phagosome. This correlated with reduced survival following phagocytosis and decreased ability to damage macrophages. Thus, GlcNAc metabolism represents the third genetically independent mechanism that utilizes to combat the rapid acidification of the phagolysosome, allowing for cells to escape and propagate infection. is the most important medically relevant fungal pathogen, with disseminated candidiasis being the fourth most common hospital-associated bloodstream infection. Macrophages and neutrophils are innate immune cells that play a key role in host defense by phagocytosing and destroying cells. To survive this attack by macrophages, generates energy by utilizing alternative carbon sources that are available in the phagosome. Interestingly, metabolism of amino acids and carboxylic acids by raises the pH of the phagosome and thereby blocks the acidification of the phagosome, which is needed to initiate antimicrobial attack. In this work, we demonstrate that metabolism of a third type of carbon source, the amino sugar GlcNAc, also induces pH neutralization and survival of upon phagocytosis. This mechanism is genetically and physiologically distinct from the previously described mechanisms of pH neutralization, indicating that the robust metabolic plasticity of ensures survival upon macrophage phagocytosis.