Ethanol induces calcium influx via the Cch1-Mid1 transporter in Saccharomycescerevisiae

摘要

Yeast suffers from a variety of environmental stresses, such as osmotic pressure and ethanol produced during fermentation. Since calcium ions are protective for high concentrations of ethanol, we investigated whether Ca2+ flux occurs in response to ethanol stress. We find that exposure of yeast to ethanol induces a rise in the cytoplasmic concentration of Ca2+. The response is enhanced in cells shifted to high-osmotic media containing proline, galactose, sorbitol, or mannitol. Suspension of cells in proline and galactose-containing media increases the Ca2+ levels in the cytoplasm independent of ethanol exposure. The enhanced ability for ethanol to induce Ca2+ flux after the hypertonic shift is transient, decreasing rapidly over a period of seconds to minutes. There is partial recovery of the response after zymolyase treatment, suggesting that cell wall integrity affects the ethanol-induced Ca2+ flux. Acetate inhibits the Ca2+ accumulation elicited by the ethanol/osmotic stress. The Ca2+ flux is primarily via the Cch1 Ca2+ influx channel because strains carrying deletions of the cch1 and mid1 genes show greater than 90% reduction in Ca2+ flux. Furthermore, a functional Cch1 channel reduced growth inhibition by ethanol.