On the Coupling of Intracellular K + to Glycolytic Oscillations in Yeast

We have investigated the interplay between glycolytic oscillations and intracellular K concentration in the yeast S. cerevisiae . Intracellular K concentration was measured using the fluorophore PBFI. We found that K is an essential ion for the occurrence of glycolytic oscillations and that intracellular K concentration oscillates synchronously with other variables such as NADH, intracellular ATP and mitochondrial membrane potential. We also investigated if glycolysis and intracellular K concentration oscillate in a number of yeast strains with mutations in 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 transporter and (ii) a strain with deletion of the late endosomal Nhx1p K /H (Na /H ) transporter. In these two mutant strains intracellular K concentration seems to be low, indicating that the two transporters may be involved in transport of K into the cytosol. In the strain Mdm38p Δ oscillations in glycolysis could be restored by addition of the K /H exchange ionophore nigericin. Furthermore, in two non-oscillating mutant strain with a defective V-ATPase and deletion of the Arp1p protein the intracellular K is relatively high, suggesting that the V-ATPase is essential for transport of K out of the cytosol and that the cytoskeleton may be involved in binding 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 ion is essential for the emergence of oscillations and support the experimental findings using mutant strains.