• Media type: E-Article
  • Title: Lipid Signaling via Pkh1/2 Regulates Fungal CO 2 Sensing through the Kinase Sch9
  • Contributor: Pohlers, Susann; Martin, Ronny; Krüger, Thomas; Hellwig, Daniela; Hänel, Frank; Kniemeyer, Olaf; Saluz, Hans Peter; Van Dijck, Patrick; Ernst, Joachim F.; Brakhage, Axel; Mühlschlegel, Fritz A.; Kurzai, Oliver
  • imprint: American Society for Microbiology, 2017
  • Published in: mBio
  • Language: English
  • DOI: 10.1128/mbio.02211-16
  • ISSN: 2161-2129; 2150-7511
  • Keywords: Virology ; Microbiology
  • Origination:
  • Footnote:
  • Description: <jats:title>ABSTRACT</jats:title> <jats:p> Adaptation to alternating CO <jats:sub>2</jats:sub> concentrations is crucial for all organisms. Carbonic anhydrases—metalloenzymes that have been found in all domains of life—enable fixation of scarce CO <jats:sub>2</jats:sub> by accelerating its conversion to bicarbonate and ensure maintenance of cellular metabolism. In fungi and other eukaryotes, the carbonic anhydrase Nce103 has been shown to be essential for growth in air (~0.04% CO <jats:sub>2</jats:sub> ). Expression of <jats:italic>NCE103</jats:italic> is regulated in response to CO <jats:sub>2</jats:sub> availability. In <jats:italic>Saccharomyces cerevisiae</jats:italic> , <jats:italic>NCE103</jats:italic> is activated by the transcription factor ScCst6, and in <jats:italic>Candida albicans</jats:italic> and <jats:italic>Candida glabrata</jats:italic> , it is activated by its homologues CaRca1 and CgRca1, respectively. To identify the kinase controlling Cst6/Rca1, we screened an <jats:italic>S. cerevisiae</jats:italic> kinase/phosphatase mutant library for the ability to regulate <jats:italic>NCE103</jats:italic> in a CO <jats:sub>2</jats:sub> -dependent manner. We identified ScSch9 as a potential ScCst6-specific kinase, as the <jats:italic>sch9</jats:italic> Δ mutant strain showed deregulated <jats:italic>NCE103</jats:italic> expression on the RNA and protein levels. Immunoprecipitation revealed the binding capabilities of both proteins, and detection of ScCst6 phosphorylation by ScSch9 <jats:italic>in vitro</jats:italic> confirmed Sch9 as the Cst6 kinase. We could show that CO <jats:sub>2</jats:sub> -dependent activation of Sch9, which is part of a kinase cascade, is mediated by lipid/Pkh1/2 signaling but not TORC1. Finally, we tested conservation of the identified regulatory cascade in the pathogenic yeast species <jats:italic>C. albicans</jats:italic> and <jats:italic>C. glabrata</jats:italic> . Deletion of <jats:italic>SCH9</jats:italic> homologues of both species impaired CO <jats:sub>2</jats:sub> -dependent regulation of <jats:italic>NCE103</jats:italic> expression, which indicates a conservation of the CO <jats:sub>2</jats:sub> adaptation mechanism among yeasts. Thus, Sch9 is a Cst6/Rca1 kinase that links CO <jats:sub>2</jats:sub> adaptation to lipid signaling via Pkh1/2 in fungi. </jats:p> <jats:p> <jats:bold>IMPORTANCE</jats:bold> All living organisms have to cope with alternating CO <jats:sub>2</jats:sub> concentrations as CO <jats:sub>2</jats:sub> levels range from very low in the atmosphere (0.04%) to high (5% and more) in other niches, including the human body. In fungi, CO <jats:sub>2</jats:sub> is sensed via two pathways. The first regulates virulence in pathogenic yeast by direct activation of adenylyl cyclase. The second pathway, although playing a fundamental role in fungal metabolism, is much less understood. Here the transcription factor Cst6/Rca1 controls carbon homeostasis by regulating carbonic anhydrase expression. Upstream signaling in this pathway remains elusive. We identify Sch9 as the kinase controlling Cst6/Rca1 activity in yeast and demonstrate that this pathway is conserved in pathogenic yeast species, which highlights identified key players as potential pharmacological targets. Furthermore, we provide a direct link between adaptation to changing CO <jats:sub>2</jats:sub> conditions and lipid/Pkh1/2 signaling in yeast, thus establishing a new signaling cascade central to metabolic adaptation. </jats:p>
  • Access State: Open Access