Characterization of potassium transport in wild‐type and isogenic yeast strains carrying all combinations of trk1, trk2 and tok1 null mutations

Bertl, Adam; Ramos, José; Ludwig, Jost; Lichtenberg‐Fraté, Hella; Reid, John D.; Bihler, Hermann; Calero, Fernando Sánchez; Martínez, Paula; Ljungdahl, Per O.

doi:10.1046/j.1365-2958.2003.03335.x

Cited by 95 publications

(104 citation statements)

References 48 publications

(75 reference statements)

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“…In addition, these experiments under high-affinity conditions clearly confirm the suspected role of Trk1p and Trk2p in Cs þ influx across the plasma membrane 8,24 and, conversely, the impact of Ena1-4p-driven cation transport in Cs þ extrusion from the cells. The Cs þ uptake time courses show an interesting biphasic behaviour with an initial plateau for both wild-type and sec22D mutant cells before further accumulation proceeds.…”

Section: Discussionsupporting

confidence: 64%

“…The time course of Cs þ uptake has been recorded for trk1D, trk2D and trk1D trk2D, as well as for ena1-4D. The high-affinity transporter Trk1p and its homologue Trk2p are involved in potassium uptake at the plasma membrane; the Ena1-4 gene cluster encodes ATPases related to cation efflux 23,24 . In all cases except trk2D, the uptake time courses of these mutants primarily affecting the cation transport at the plasma membrane are considerably different from the respective wild types and, importantly, from sec22D ( Figs 2 and 4).…”

Section: Resultsmentioning

confidence: 99%

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Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Dräxl

Müller

et al. 2013

Nat Commun

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The non-essential cation caesium (Cs þ ) is assimilated by all organisms. Thus, anthropogenically released radiocaesium is of concern to agriculture. Cs þ accumulates owing to its chemical similarity to the potassium ion (K þ ). The apparent lack of a Cs þ -specific uptake mechanism has obstructed attempts to manipulate Cs þ accumulation without causing pleiotropic effects. Here we show that the SNARE protein Sec22p/SEC22 specifically impacts Cs þ accumulation in yeast and in plants. Loss of Saccharomyces cerevisiae Sec22p does not affect K þ homeostasis, yet halves Cs þ concentration compared with the wild type. Mathematical modelling of the uptake time course predicts a compromised vacuolar Cs þ deposition in sec22D. Biochemical fractionation confirms this and indicates a new feature of Sec22p in enhancing non-selective cation deposition. A developmentally controlled loss-of-function mutant of the orthologous Arabidopsis thaliana SEC22 phenocopies the reduced Cs þ uptake without affecting plant growth. This finding provides a new strategy to reduce radiocaesium entry into the food chain.

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Section: Discussionsupporting

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Dräxl

Müller

et al. 2013

Nat Commun

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“…It is usually accepted that several nonspecific transporters may be involved in the low-affinity transport of K ϩ observed in the ⌬trk1 ⌬trk2 mutant (22). The existence of a yeast nonselective cation channel responsible for the low-affinity K ϩ uptake was postulated before, although the identity of the protein(s) responsible for this inwardly rectifying pathway is not known (2,3). Amino acid or sugar transporters could be involved in this process (22,50) together with Qdr2p and, eventually, other plasma membrane multidrug resistance transporters.…”

Section: Discussionmentioning

confidence: 99%

Saccharomyces cerevisiae Multidrug Resistance Transporter Qdr2 Is Implicated in Potassium Uptake, Providing a Physiological Advantage to Quinidine-Stressed Cells

et al. 2007

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The QDR2 gene of Saccharomyces cerevisiae encodes a putative plasma membrane drug:H ؉ antiporter that confers resistance against quinidine, barban, bleomycin, and cisplatin. This work provides experimental evidence of defective K ؉ (Rb ؉ ) uptake in the absence of QDR2. The direct involvement of Qdr2p in K ؉ uptake is reinforced by the fact that increased K ؉ (Rb ؉ ) uptake due to QDR2 expression is independent of the Trk1p/Trk2p system. QDR2 expression confers a physiological advantage for the yeast cell during the onset of K ؉ limited growth, due either to a limiting level of K ؉ in the growth medium or to the presence of quinidine. This drug decreases the K ؉ uptake rate and K ؉ accumulation in the yeast cell, especially in the ⌬qdr2 mutant. Qdr2p also helps to sustain the decrease of intracellular pH in quinidine-stressed cells in growth medium at pH 5.5 by indirectly promoting H ؉ extrusion affected by the drug. The results are consistent with the hypothesis that Qdr2p may also couple K ؉ movement with substrate export, presumably with quinidine. Other clues to the biological role of QDR2 in the yeast cell come from two additional lines of experimental evidence. First, QDR2 transcription is activated under nitrogen (NH 4 ؉ ) limitation or when the auxotrophic strain examined enters stationary phase due to leucine limitation, this regulation being dependent on general amino acid control by Gcn4p. Second, the amino acid pool is higher in ⌬qdr2 cells than in wild-type cells, indicating that QDR2 expression is, directly or indirectly, involved in amino acid homeostasis.

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“…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. Since these strains are resistant to G418 and contain the ura3 mutation, we performed the experiments with the pHl-U plasmid.…”

Section: Buffering Capacity Estimationmentioning

confidence: 99%

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

Marešová

Hošková

Urbánková

et al. 2010

Yeast

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AbstractpHluorin is a pH-sensitive variant of green fluorescent protein for measuring intracellular pH (pH in ) in living cells. We constructed a new pHluorin plasmid with the dominant selection marker KanMX. This plasmid allows pH measurements in cells without auxotrophic mutations and/or grown in chemically indefinite media. We observed differing values of pH in for three prototrophic wild-types. The new construct was also used to determine the pH in in strains differing in the activity of the plasma membrane Pma1 H + -ATPase and the influence of glucose on pH in . We describe in detail pHluorin measurements performed in a microplate reader, which require much less hands-on time and much lower cell culture volumes compared to standard cuvettes measurements. We also utilized pHluorin in a new method of measuring the buffering capacity of yeast cell cytosol in vivo, shown to be ca. 52 mM/pH for wild-type yeast and moderately decreased in mutants with affected potassium transport.

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Characterization of potassium transport in wild‐type and isogenic yeast strains carrying all combinations of trk1, trk2 and tok1 null mutations

Cited by 95 publications

References 48 publications

Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Saccharomyces cerevisiae Multidrug Resistance Transporter Qdr2 Is Implicated in Potassium Uptake, Providing a Physiological Advantage to Quinidine-Stressed Cells

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

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