Glutamate dehydrogenase (Gdh2)-dependent alkalization is dispensable for escape from macrophages and virulence ofCandida albicans

Abstract

31Candida albicans cells depend on the energy derived from amino acid catabolism to 32 induce and sustain hyphal growth inside phagosomes of engulfing macrophages. 33The concomitant deamination of amino acids is thought to neutralize the acidic 34 microenvironment of phagosomes, a presumed requisite for survival and initiation of 35 hyphal growth. Here, in contrast to an existing model, we show that mitochondrial-36 localized NAD + -dependent glutamate dehydrogenase (GDH2) catalyzing the 37 deamination of glutamate to α-ketoglutarate, and not the cytosolic urea amidolyase 38 (DUR1,2), accounts for the observed alkalization of media when amino acids are the 39 sole sources of carbon and nitrogen. C. albicans strains lacking GDH2 (gdh2-/-) are 40 viable and do not extrude ammonia on amino acid-based media. Environmental 41 alkalization does not occur under conditions of high glucose (2%), a finding 42 attributable to glucose-repression of GDH2 expression and mitochondrial function. 43

Diverse mechanisms control amino acid-dependent environmental alkalization byCandida albicans

“…S1A) [14]; we designate stp2-/-/-as stp2. As in previous reports, the stp2 strain showed a clear defect in Silao et al, 2023 Gdh2 functions as a rheostat controlling extracellular pH alkalization even at high density (OD  5) (Fig. 4A, upper panel).…”

“…The copyright holder for this preprint this version posted August 4, 2023. ; https://doi.org/10.1101/2023.08.04.551922 doi: bioRxiv preprint Silao et al, 2023 Gdh2 functions as a rheostat controlling extracellular pH Silao et al, 2023 Gdh2 functions as a rheostat controlling extracellular pH normally thrives in the acidic vaginal microenvironment, we found that environmental alkalization does not directly limit the growth of this competing microorganism.…”

“…2A). Consequently, cells growing in the presence of Silao et al, 2023 Gdh2 functions as a rheostat controlling extracellular pH high glucose, should retain a limited capacity to produce ammonia and to alkalinize the medium. To reconcile these findings, we posited that the substrate glutamate becomes limiting due to glucose repression of processes that generate it.…”

“…The copyright holder for this preprint this version posted August 4, 2023. ; https://doi.org/10.1101/2023.08.04.551922 doi: bioRxiv preprint Silao et al, 2023 Gdh2 functions as a rheostat controlling extracellular pH harmless commensal, thriving as a benign member of human microbiota in healthy individuals. Amino acids are among the most abundant nutrients in human hosts capable of supporting growth of this fungus.…”

Post-transcriptional regulation of glutamate metabolism ofPichia pastorisand development of a glutamate-inducible yeast expression system

“…A third, NAD-dependent GDH (GDH2) localized in the mitochondria degrades glutamate to α-ketoglutarate and ammonia and thus contributes to anaplerosis of Krebs cycle. Glutamate and glutamine contribute for 85% and 15% of total cellular nitrogen, respectively in S. cerevisiae (Miller and Magasanik, 1990) (Mara et al, 2018) (https://www.yeastgenome.org/locus/S000002374#protein) (Silao et al, 2020). In addition to being a nitrogen donor, Glutamate is also utilized as the sole source of carbon by Pichia pastoris ( a.k.a.…”