RT Journal Article SR Electronic(1) A1 Eilam, Y. A1 Othman, M. A1 Halachmi, D.YR 1990 T1 Transient increase in Ca2+ influx in Saccharomyces cerevisiae in response to glucose: effects of intracellular acidification and cAMP levels JF Microbiology, VO 136 IS 12 SP 2537 OP 2543 DO https://doi.org/10.1099/00221287-136-12-2537 PB Microbiology Society, SN 1465-2080, AB Influx of 45Ca2+ into Saccharomyces cerevisiae was measured under experimental conditions which enabled measurements of initial rate of transport across the plasma membrane, without interference by the vacuolar Ca2+ transport system. Addition of glucose or glycerol to the cells, after pre-incubation in glucose-free medium for 5 min, caused a rapid, transient increase in 45Ca2+ influx, reaching a peak at 3–5 min after addition of substrate. Ethanol, or glycerol added with antimycin A, had no effect on 45Ca2+ influx. We have shown previously that this increase is not mediated by an effect of the substrates on intracellular ATP levels. Changes in membrane potential accounted for only a part of the glucose-stimulated 45Ca2+ influx. The roles of intracellular acidification and changes in cellular cAMP in mediating the effects of glucose on 45Ca2+ influx were examined. After a short preincubation in glucose-free medium addition of glucose caused a decrease in the intracellular pH, [pH]i, which reached a minimum value after 3 min. A transient increase in the cellular cAMP level was also observed. Addition of glycerol also caused intracellular acidification, but ethanol or glycerol added with antimycin A had no effect on [pH]i. Artificial intracellular acidification induced by exposure to isobutyric acid or to CCCP caused a transient rise in Ca2+ influx but the extent of the increase was smaller than that caused by glucose, and the time-course was different. We conclude that intracellular acidification may be responsible for part of the glucose stimulation of Ca2+ influx. The role of the increase in cAMP level on Ca2+ influx was examined by measuring the effect of glucose and of artificial intracellular acidification on Ca2+ influx in a cyr1 strain which lacks adenylate cyclase activity. In this strain, addition of glucose or isobutyric acid still led to a transient increase in Ca2+ transport. Therefore, we concluded that at least part of the increase in Ca2+ influx in response to glucose is cAMP-independent., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-136-12-2537