title: Yeast 14-3-3 proteins participate in the regulation of cell cation homeostasis via interaction with Nha1 alkali-metal-cation/proton antiporter.
abstract: BACKGROUND
  In yeast, 14-3-3 proteins bind to hundreds of phosphorylated proteins and play a role in the regulation of many processes including tolerance to NaCl. However, the mechanism of 14-3-3 involvement in the cell answer to salt or osmotic stresses is weakly understood.
  
  
  METHODS
  We studied the role of the Saccharomyces cerevisiae 14-3-3 homologs Bmh1 and Bmh2 in the regulation of alkali-metal-cation homeostasis using the genetic-interaction approach. Obtained results were confirmed with the Bimolecular-Fluorescence-Complementation method.
  
  
  RESULTS
  Deletion of BMH1, encoding the major 14-3-3 isoform, resulted in an increased sensitivity to Na+, Li+ and K+ and to cationic drugs but did not affect membrane potential. This bmh1Δ phenotype was complemented by overexpression of BMH2. Testing the genetic interaction between BMH genes and genes encoding plasma-membrane cation transporters revealed, that 14-3-3 proteins neither interact with the potassium uptake systems, nor with the potassium-specific channel nor with the Na+(K+)-ATPases. Instead, a genetic interaction was identified between BMH1 and NHA1 which encodes an Na+(K+)/H+ antiporter. In addition, a physical interaction between 14-3-3 proteins and the Nha1 antiporter was shown. This interaction does not depend on the phosphorylation of the Nha1 antiporter by Hog1 kinase. Our results uncovered a previously unknown interaction partner of yeast 14-3-3 proteins and provided evidence for the previously hypothesized involvement of Bmh proteins in yeast salt tolerance.
  
  
  CONCLUSIONS
  Our results showed for the first time that the yeast 14-3-3 proteins and an alkali-metal-cation efflux system interact and that this interaction enhances the cell survival upon salt stress.
authors.affiliation: Department of Membrane Transport, Institute of Physiology Academy of Sciences of the Czech Republic, v.v.i., 142 20 Prague 4, Czech Republic.
authors.forename: Jaromír
authors.initials: J
authors.lastname: Zahrádka
authors.forename: G Paul H
authors.initials: GP
authors.lastname: van Heusden
authors.forename: Hana
authors.initials: H
authors.lastname: Sychrová
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000378:metabolism*; D002412:Cations / Q000378:metabolism*; D002470:Cell Survival; D005434:Flow Cytometry; D006706:Homeostasis / Q000502:physiology*; D008564:Membrane Potentials; D008672:Metals, Alkali / Q000378:metabolism*; D010766:Phosphorylation; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; C075852:BMH1 protein, S cerevisiae; D027682:Cation Transport Proteins; D002412:Cations; D008672:Metals, Alkali; C000631624:NHA1 protein, S cerevisiae; D011522:Protons; D029701:Saccharomyces cerevisiae Proteins; D017923:Sodium-Hydrogen Exchangers