Yeast 14-3-3 proteins participate in the regulation of cell cation homeostasis via interaction with Nha1 alkali-metal-cation/proton antiporter

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 bmh1 Delta 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. General significance: Our results showed for the first time that the yeast 14-3-3 proteins and an alkali-metalcation efflux system interact and that this interaction enhances the cell survival upon salt stress. (C) 2012 Elsevier B.V. All rights reserved.