Functional study of the Nha1p C-terminus: involvement in cell response to changes in external osmolarity

Curr Genet. 2006 Apr;49(4):229-36. doi: 10.1007/s00294-005-0050-1. Epub 2006 Jan 10.


Saccharomyces cerevisiae uses different mechanisms to adapt to changes in environmental osmolarity. Upon hyperosmotic shock, cells first mobilize a rapid rescue system that prevents excessive loss of ions and water; then in the adaptation period they accumulate a compatible solute (glycerol). When subjected to hypoosmotic shock, they rapidly release intracellular stocks of glycerol to reduce intracellular osmolarity and prevent bursting. The plasma membrane Nha1 alkali metal cation/H+ antiporter is not important in helping the cells to survive a sudden drop in external osmolarity, but is involved in the cell response to hyperosmotic shock. For this role, its long hydrophilic C-terminus is indispensable. The capacity of the Nha1 antiporter to transport potassium is regulated by Hog1 kinase. Upon sorbitol-mediated stress, the Nha1p potassium export activity decreases in order to maintain a higher intracellular concentration of solutes. The C-terminal-less Nha1 version is not inactivated and its potassium efflux activity renders cells very sensitive to hyperosmotic shock. Taken together, our results suggest an important role of Nha1p and its C-terminus in the immediate response to hyperosmotic shock as part of the rapid rescue mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / physiology
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Gene Expression Regulation, Fungal / physiology*
  • Ion Transport / physiology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism
  • Osmotic Pressure
  • Protein Structure, Tertiary / genetics
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*
  • Up-Regulation / physiology*


  • Cation Transport Proteins
  • Membrane Proteins
  • NHA1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sodium-Hydrogen Exchangers
  • HOG1 protein, S cerevisiae
  • Mitogen-Activated Protein Kinases