The Mechanism of Intracellular Acidification Induced by Glucose in Saccharomyces cerevisiae

Abstract

Addition of glucose or fructose to cells of Saccharomyces cerevisiae adapted to grow in the absence of glucose induced an acidification of the intracellular medium. This acidification appeared to be due to the phosphorylation of the sugar since : (i) glucose analogues which are not efficiently phosphorylated did not induce internal acidification; (ii) glucose addition did not cause internal acidification in a mutant deficient in all the three sugar-phosphorylating enzymes; (iii) fructose did not affect the intracellular pH in a double mutant having only glucokinase activity; (iv) glucose was as effective as fructose in inducing the internal pH drop in a mutant deficient in phosphoglucose isomerase activity; and (v) in strains deficient in two of the three sugar-phosphorylating activities, there was a good correlation between the specific glucose-or fructose-phosphorylating activity of cell extracts and the sugar-induced internal acidification. In addition, in whole cells any of the three yeast sugar kinases were capable of mediating the internal acidification described. Glucose-induced internal acidification was observed even when yeast cells were suspended in growth medium and in cells suspended in buffer containing K+, which supports the possible signalling function of the glucose-induced internal acidification. Evaluation of internal pH by following fluorescence changes of fluorescein-loaded cells indicated that the change in intracellular pH occurred immediately after addition of sugar. The apparent K , for glucose in this process was 2 mM. Changes in both the internal and external pH were determined and it was found that the internal acidification induced by glucose was followed by a partial alkalinization coincident with the initiation of H+ efflux. This reversal of acidification could be due to the activity of the H+-ATPase, since it was inhibited by diethylstilboestrol. Coincidence between internal alkalinization and the H+ efflux was also observed after addition of ethanol.

Consequences of Loss of Vph1 Protein-containing Vacuolar ATPases (V-ATPases) for Overall Cellular pH Homeostasis

“…Cells grown in selective medium to retain the pHluorin plasmid were deprived of glucose for ϳ30 min and then monitored before and after the addition of glucose to 50 mM final concentration. As shown by others using pHluorinbased and other methods (22,23), Fig. 2A illustrates that the addition of glucose to glucose-deprived wild-type cells results in a transient cytosolic acidification within a minute of glucose addition followed by a rapid rise in cytosolic pH that is complete within 3 min of glucose addition.…”

Effect of Polygodial on the Mitochondrial ATPase of Saccharomyces cerevisiae

“…The regulation of Pma1 ATPase by glucose at the molecular level is not yet fully understood, but the maintenance of proper internal pH is essential for enzyme activity and allows the cell to survive at a low environmental pH (33,41). Acidification of the external medium is a complex process involving many cellular components.…”

ATP requirements for benzoic acid tolerance in Zygosaccharomyces bailii

“…Studies with S. cerevisiae have shown that, in response to that acidification, the plasma membrane H + -ATPase pumps protons out of the cell in a ATPdependent mechanism (Eraso and Gancedo 1987;Ramos et al 1989). Similar mechanisms in S. cerevisiae has been observed with sorbic acid, which induces a stimulation of the plasma membrane H + -ATPase activity and a drastic reduction of cellular ATP level (Holyoak et al 1996).…”