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.
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 were 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 bioenergetic 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.
authors.affiliation: Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: MyungHee
authors.initials: M
authors.lastname: Ku
authors.affiliation: Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Yong-Un
authors.initials: YU
authors.lastname: Baek
authors.affiliation: Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: genie6@snu.ac.kr.
authors.forename: Min-Kyu
authors.initials: MK
authors.lastname: Kwak
authors.affiliation: Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: kangsaou@snu.ac.kr.
authors.forename: Sa-Ouk
authors.initials: SO
authors.lastname: Kang
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D002176:Candida albicans / Q000254:growth & development / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology; D005656:Fungal Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D005980:Glutathione Reductase / Q000378:metabolism*; D006019:Glycolysis / Q000502:physiology; D025301:Hyphae / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D011765:Pyruvaldehyde / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism*; D014774:Virulence / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; C121438:EFG1 protein, Candida albicans; D005656:Fungal Proteins; D014157:Transcription Factors; D011765:Pyruvaldehyde; D000242:Cyclic AMP; D000426:Alcohol Dehydrogenase; D005980:Glutathione Reductase; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Alcohol dehydrogenase; Candida albicans; Efg1-mediated cyclic AMP/protein kinase A pathways; Glutathione; Glutathione reductase; Hyphal growth; Methylglyoxal