Min Kyu Kwak
Seoul National University, South Korea
Title: Candida albicans glutathione reductase downregulates Efg1-mediated cyclic AMP/protein kinase-A pathway and leads to defective hyphal growth and virulence upon decreased cellular methylglyoxal content accompanied by activating alcohol dehydrogenase and glycolytic enzymes
Biography
Biography: Min Kyu Kwak
Abstract
Glutathione reductase maintains the glutathione level in a reduced state. As previously demonstrated, glutathione is required for cell growth/division and its biosynthesizing-enzyme deficiency causes methylglyoxal accumulation. However, experimental evidences for reciprocal relationships between Cph1-/Efg1-mediated signaling pathway regulation and methylglyoxal production exerted by glutathione reductase on yeast morphology remain unclear. Glutathione reductase (GLR1) disruption/overexpression was performed to investigate aspects of pathological/morphological alterations in Candida albicans. These assumptions were proved by observations of cellular susceptibility to oxidants and thiols, and measurements of methylglyoxal and glutathione content in hyphal-inducing conditions mainly through the activity of GLR1-overexpressing cells. Additionally, the transcriptional/translational levels of bio-energetic enzymes and dimorphism-regulating protein kinases were examined in the strain. The GLR1-deficient strain was non-viable when GLR1 expression under the control of a CaMAL2 promoter was conditionally repressed, despite partial rescue of growth by exogenous thiols. During filamentation, non-growing hyphal GLR1-overexpressing cells exhibited resistance against oxidants and cellular methylglyoxal was significantly decreased, which concomitantly increased expressions of genes encoding energy-generating enzymes, including fructose-1,6-bisphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, and alcohol dehydrogenase (ADH1), with remarkable repression of Efg1-signaling cascades. This is the first report that GLR1-triggered Efg1-mediated signal transduction repression strictly reduces dimorphic switching and virulence by maintaining the basal level of methylglyoxal following the enhanced gene expressions of glycolytic enzymes and ADH1. The Efg1 downregulatory mechanism by GLR1 expression has possibilities to involve in other complex network of signal pathways. Understanding how GLR1 overexpression affects multiple signaling pathways can help identify attractive targets for antifungal drugs.
References:
- Kwak M K, Liu R, Kwon J O, Kim M K, Kim A H, Kang S O (2013) Cyclic dipeptides from lactic acid bacteria inhibit proliferation of the influenza A virus. J. Microbiol. 51: 836-843.
- Kwak M K, Liu R, Kim M K, Moon D, Kim A H, Song S H, Kang S O (2014) Cyclic dipeptides from lactic acid bacteria inhibit the proliferation of pathogenic fungi. J. Microbiol. 52: 64-70.
- Kwak M K, Ku M, Kang S O (2014) NAD+-linked alcohol dehydrogenase 1 regulates methylglyoxal concentration in Candida albicans. FEBS Lett. 588(7): 1144-1153.
- Kwak M K, Song S H, Ku M, Kang S O (2015) Candida albicans erythroascorbate peroxidase regulates intracellular methylglyoxal and reactive oxygen species independently of D-erythroascorbic acid. FEBS Lett. 589(15): 1863-1871.
- Kwak M K, Lee M H, Park S J, Shin S M, Liu R, Kang S O (2016) Polyamines regulate cell growth and cellular methylglyoxal in high-glucose medium independently of intracellular glutathione. FEBS Lett. 590(6): 739-749.