On the coupling of intracellular K + ${{\rm{K}}}^{+}$ to glycolytic oscillations in yeast.

We have investigated the interplay between glycolytic oscillations and intracellular K + ${{\rm{K}}}^{+}$ concentration in the yeast Saccharomyces cerevisiae. Intracellular K + ${{\rm{K}}}^{+}$ concentration was measured using the fluorophore potassium-binding benzofuranisophthalate (PBFI). We found that K + ${{\rm{K}}}^{+}$ is an essential ion for the occurrence of glycolytic oscillations and that intracellular K + ${{\rm{K}}}^{+}$ concentration oscillates synchronously with other variables such as nicotinamide adenine dinucleotide hydride (NADH), intracellular adenosine triphosphate (ATP), and mitochondrial membrane potential. We also investigated if glycolysis and intracellular K + ${{\rm{K}}}^{+}$ concentration oscillate in a number of yeast strains with mutations in K + ${{\rm{K}}}^{+}$ transporters in the plasma membrane, mitochondrial membrane and in the vacuolar membrane. Most of these strains are still capable of showing glycolytic oscillations, but two strains are not: (i) a strain with a deletion in the mitochondrial Mdm38p K + ∕ H + ${{\rm{K}}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ transporter and (ii) a strain with deletion of the late endosomal Nhx1p K + ∕ H + ${{\rm{K}}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ ( Na + ∕ H + ${\text{Na}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ ) transporter. In these two mutant strains intracellular K + ${{\rm{K}}}^{+}$ concentration seems to be low, indicating that the two transporters may be involved in transport of K + ${{\rm{K}}}^{+}$ into the cytosol. In the strain, Mdm38p Δ ${\rm{\Delta }}$ oscillations in glycolysis could be restored by addition of the K + ∕ H + ${{\rm{K}}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ exchange ionophore nigericin. Furthermore, in two nonoscillating mutant strains with a defective V-ATPase and deletion of the Arp1p protein the intracellular K + ${{\rm{K}}}^{+}$ is relatively high, suggesting that the V-ATPase is essential for transport of K + ${{\rm{K}}}^{+}$ out of the cytosol and that the cytoskeleton may be involved in binding K + ${{\rm{K}}}^{+}$ to reduce the concentration of free ion in the cytosol. Analyses of the time series of oscillations of NADH, ATP, mitochondrial membrane potential, and potassium concentration using data-driven modeling corroborate the conjecture that K + ${{\rm{K}}}^{+}$ ion is essential for the emergence of oscillations and support the experimental findings using mutant strains.