title: The sodium pump Ena1p provides mechanistic insight into the salt sensitivity of vacuolar protein sorting mutants.
abstract: The vacuolar/endosomal network has an important but as yet undefined role in the cellular tolerance to salt stress. We hypothesized that the mechanistic basis for the importance of vacuolar protein sorting (vps) components in salt tolerance is the targeting of the crucial sodium exporter Ena1p to the plasma membrane. The link between Ena1p and the vps components was established by the observation that overexpression of Ena1p could suppress the salt sensitivity of the ESCRT knockouts vps20Delta, snf7/vps32Delta and snf8/vps22Delta. To further investigate this functional interaction, fluorescence microscopy was utilized to monitor localization of GFP-tagged Ena1p. For all analyzed vps mutants, Ena1p seemed properly localized to the plasma membrane, even during saline growth. However, quantitative differences in plasma membrane localized Ena1p were recorded; e.g. the highly salt sensitive pep12Delta mutant exhibited substantially enhanced Ena1p levels. In addition, the kinetics of Ena1p localization to the plasma membrane was severely delayed in several vps mutants, and this delay correlated to the salt specific growth defect. This paper discusses potential mechanistic hypotheses, like Ena1p transporter activity or localization kinetics, or ESCRT component's influence on signaling, for linking endosomal sorting functions to cellular salt sensitivity.
authors.affiliation: Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
authors.forename: Katarina
authors.initials: K
authors.lastname: Logg
authors.forename: Jonas
authors.initials: J
authors.lastname: Warringer
authors.forename: Sayed Hossein
authors.initials: SH
authors.lastname: Hashemi
authors.forename: Mikael
authors.initials: M
authors.lastname: Käll
authors.forename: Anders
authors.initials: A
authors.lastname: Blomberg
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D014882:Water-Electrolyte Balance
chemical_list: D027682:Cation Transport Proteins; C086375:ENA1 protein, S cerevisiae; D056827:Endosomal Sorting Complexes Required for Transport; D009687:Nuclear Proteins; C083890:SNF7 protein, S cerevisiae; C094045:SNF8 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D012965:Sodium Chloride; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase