Involvement of Nha1 antiporter in regulation of intracellular pH in Saccharomyces cerevisiae

Abstract

The Nha1 antiporter is involved in regulation of intracellular pH in Saccharomyces cerevisiae. We report that deletion of the NHA1 gene resulted in an increase of cytoplasmic pH in cells suspended in water or acidic buffers. Addition of KCl or NaCl to exponentially growing cells lowered the internal pH but the difference between cells with or without NHA1 was maintained. Addition of KCl to starved cells resulted in much higher alkalinization of cytoplasmic pH in a strain lacking Nha1p compared to the wild-type or Nha1p-overexpressing strains. The H /K (Na ) exchange mechanism of Nha1p was confirmed in reconstituted plasma membrane vesicles. z

Role of the Nha1 antiporter in regulating K+ influx in Saccharomyces cerevisiae

“…Deletion of TRK2 in a TRK1 background did not result in a growth defect and electrophysiological studies have shown that the Trk2p-mediated currents are independent of the amount of K + in the solution and are strongly regulated by external pH (Bihler et al, 1999). The potassium content and intracellular pH have a significant effect on alkali cation influx (Rodríguez-Navarro and Ramos, 1984;Ryan et al, 1971).We show in this paper that Nha1p is involved in the regulation of intracellular potassium and it has been reported previously that NHA1 is involved in the regulation of the intracellular pH (deletion of NHA1 results in an increase in cytoplasmic pH) (Sychrová et al, 1999). Therefore, a likely hypothesis is that Nha1p modulates the activity of the major potassium uptake system in S. cerevisiae (Trk1p) by changes in the potassium content and/or internal pH.…”

“…As a result, Nha1p may participate in the regulation of the internal pH, cell volume and osmotic pressure (Csonka, 1989;Csonka and Hansen, 1991;Sychrová et al, 1999). Two genes related to the K + influx process have been identified in S. cerevisiae.…”

Mechanism of liponecrosis, a distinct mode of programmed cell death

“…Thus, the POA-induced alkalinisation of culture medium by yeast cells is not essential for the ability of POA to trigger liponecrosis. Our unpublished data validate this conclusion; as we found, a hypomorphic allele of the gene encoding the PM ATPase Pma1p, 19 a single-gene-deletion mutation eliminating the PM Na 20 and a single-gene-deletion mutation removing the PM K C transporter Trk1p 21 exhibit considerable differential effects on the extent of culture medium alkalinisation by cells exposed to POA but do not alter the susceptibility of yeast to POA-induced liponecrosis (Feldman et al, in preparation).…”

New applications of pHluorin—measuring intracellular pH of prototrophic yeasts and determining changes in the buffering capacity of strains with affected potassium homeostasis

“…For this analysis we chose S. cerevisiae BY4742 and single mutants derived from this strain. The nha1 and nhx1 mutants were selected as reference strains because some changes in their cytosolic pH had been reported previously (Brett et al, 2005;Sychrova et al, 1999). We also included the arl1 and trk1 mutants, because their potassium transport properties are affected (Bertl et al, 2003;Munson et al, 2004) and we expected that potassium homeostasis could influence buffering ability.…”