Regulation of the cAMP level in the yeast Saccharomyces cerevisiae: intracellular pH and the effect of membrane depolarizing compounds

• Published in: Journal of general microbiology Vol. 133; no. 8; pp. 2191 - 2196
• Main Authors: Thevelein, J.M, Beullens, M, Honshoven, F, Hoebeeck, G, Detremerie, K, Den Hollander, J.A, Jans, A.W.H
• Format: Journal Article
• Language: English
• Published: London Soc General Microbiol 01-08-1987; New York, NY Cambridge University Press
• Subjects: Azides - pharmacology; Biological and medical sciences; cyclic AMP; Cyclic AMP - metabolism; Dinitrophenols - pharmacology; Drug Synergism; Fundamental and applied biological sciences. Psychology; Glucose - pharmacology; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; Hydrogen-Ion Concentration; Microbiology; Mycology; Onium Compounds - pharmacokinetics; Organophosphorus Compounds - pharmacokinetics; plasma membrane; plasma membranes; Saccharomyces cerevisiae; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - metabolism; Fungi; Depolarization; Yeast; Plasma membrane; Cyclic AMP; PH; Influence; Ascomycetes; Ratio; Intracellular; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0022-1287; 1350-0872; 1465-2080
• DOI: 10.1099/00221287-133-8-2191

1 Laboratorium voor Cellulaire Biochemie, Katholieke Universiteit te Leuven, Kardinaal Mercierlaan 92, B-3030 Leuven — Heverlee, Belgium
2 Philips Medical Systems, PO Box 218, 5600 MD Eindhoven, The Netherlands
3 Max-Planck-Institut für Systemphysiologie, Rheinlanddamm 201, D-4600 Dortmund 1, FRG
ABSTRACT
SUMMARY: Addition of plasma membrane depolarizing agents, such as dinitrophenol (DNP) and azide, to cells of Saccharomyces cerevisiae under aerobic conditions, is known to cause an increase in the cAMP level within 15 s. We found that both compounds lowered the intracellular pH (measured by in vivo 3 P-NMR) drastically within the same time period. Plasma membrane depolarization, however, was much slower: DNP and azide had no effect on the membrane potential during, respectively, the first 2 min and the first 10 min after addition. Apparently, the intracellular pH of yeast is much more sensitive to perturbation than the membrane potential. The effect of both compounds on the cAMP level was highly dependent on the extracellular pH: when the latter was raised, the effect disappeared completely between pH 6 and 7. A similar dependence on the extracellular pH was observed for the lowering of intracellular pH. Addition of organic acids, such as acetate and butyrate, at low pH and under aerobic conditions, also caused an immediate increase in the cAMP level and an immediate drop in the intracellular pH. These results suggest that agents such as DNP and azide do not raise the cAMP level in yeast cells because of their membrane depolarizing properties but because they lower the intracellular pH. Under anaerobic conditions, DNP. azide and organic acids were much less effective in increasing the cAMP level. Addition of a small amount of glucose, however, restored their capacity to enhance the cAMP level. This suggests that under anaerobic conditions and in the absence of glucose the ATP level is a limiting factor for cAMP synthesis.