Activation of divalent cation influx into S. cerevisiae cells by hypotonic downshift

Subjecting Saccharomyces cerevisiae cells to a hypotonic downshift by transferring cells from YPD medium containing 0.8 M sorbitol to YPD medium without sorbitol induces a transient rapid influx of Ca²⁺ and other divalent cations into the cell. For cells grown in YPD at 37°C, this hypotonic downshift increases Ca²⁺ accumulation 6.7-fold. Hypotonic downshift-induced Ca²⁺ accumulation and steady-state Ca²⁺ accumulation in isotonic YPD medium are differentially affected by dodecylamine and Mg²⁺. The Ca²⁺-influx pathway responsible for hypotonic-induced Ca²⁺ influx may account for about 10-35% of Ca²⁺ accumulation by cells growing in YPB. Ca²⁺ influx is not required for cells to survive a hypotonic downshift. Hypotonic downshift greatly reduces the ability of S. cerevisiae cells to survive a 5-min exposure to 10 mM Cd²⁺ suggesting that mutants resistant to acute Cd²⁺ exposure may help identify genes required for hypotonic downshift-induced divalent cation influx.