Subcellular potassium and sodium distribution in Saccharomyces cerevisiae wild type and vacuolar mutants

Living cells accumulate potassium to fulfill multiple functions. It is well documented that the model yeast Saccharomyces cerevisiae grows at very different concentrations of external alkali cations and keeps high and low intracellular concentrations of potassium and sodium respectively. However less attention has been paid to the study of the intracellular distribution of these cations. The most widely used experimental approach, plasma membrane permeabilization, produces incomplete results, since it usually considers only cytoplasm and vacuoles as compartments where the cations are present in significant amounts. By isolating and analyzing the main yeast organelles, we have determined subcellular location of potassium and sodium in S. cerevisiae. We show that while vacuoles accumulate most of the intracellular potassium and sodium, the cytosol contains relatively low amounts, which is especially relevant in the case of sodium. However potassium concentrations in the cytosol are kept rather constant during the potassium starvation process and we conclude that for that purpose, vacuolar potassium has to be rapidly mobilized. We also show that this intracellular distribution is altered in four different mutants with impaired vacuolar physiology. Finally, we show that both in wild type and vacuolar mutants, nuclei contain and keep a relatively constant and important percentage of total intracellular potassium and sodium, which most probably is involved in the neutralization of ...
Source: BJ Cell - Category: Biochemistry Authors: Tags: BJ Cell Source Type: research