Matsumoto Tracie K, Ellsmore Amanda J, Cessna Stephen G, Low Philip S, Pardo José M, Bressan Ray A, Hasegawa Paul M
Center for Plant Environmental Stress Physiology, Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907-1165, USA.
J Biol Chem. 2002 Sep 6;277(36):33075-80. doi: 10.1074/jbc.M205037200. Epub 2002 Jun 25.
Hyperosmotic stress caused by NaCl, LiCl, or sorbitol induces an immediate and short duration ( approximately 1 min) transient cytosolic Ca(2+) (Ca(2+)) increase (Ca(2+)-dependent aequorin luminescence) in Saccharomyces cerevisiae cells. The amplitude of the osmotically induced Ca(2+) transient was attenuated by the addition of chelating agents EGTA or BAPTA, cation channel pore blockers, competitive inhibitors of Ca(2+) transport, or mutations (cch1Delta or mid1Delta) that reduce Ca(2+) influx, indicating that Ca(ext)(2+) is a source for the transient. An osmotic pretreatment (30 min) administered by inoculating cells into media supplemented with either NaCl (0.4 or 0.5 m) or sorbitol (0.8 or 1.0 m) enhanced the subsequent growth of these cells in media containing 1 m NaCl or 2 m sorbitol. Inclusion of EGTA in the osmotic pretreatment media or the cch1Delta mutation reduced cellular capacity for NaCl but not hyperosmotic adaptation. The stress-adaptive effect of hyperosmotic pretreatment was mimicked by exposing cells briefly to 20 mm CaCl(2). Thus, NaCl- or sorbitol-induced hyperosmotic shock causes a Ca(2+) transient that is facilitated by Ca(2+) influx, which enhances ionic but not osmotic stress adaptation. NaCl-induced ENA1 expression was inhibited by EGTA, cch1Delta mutation, and FK506, indicating that the Ca(2+) transient activates calcineurin signaling to mediate ion homeostasis and salt tolerance.
由氯化钠、氯化锂或山梨醇引起的高渗胁迫会在酿酒酵母细胞中诱导胞质钙（Ca(2+)）立即出现并持续较短时间（约1分钟）的短暂升高（依赖于钙的水母发光蛋白发光）。通过添加螯合剂乙二醇双四乙酸（EGTA）或1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸（BAPTA）、阳离子通道孔道阻滞剂、钙转运的竞争性抑制剂或减少钙内流的突变（cch1Delta或mid1Delta），可减弱渗透诱导的Ca(2+)瞬变的幅度，这表明细胞外钙（Ca(ext)(2+)）是该瞬变的一个来源。通过将细胞接种到补充有氯化钠（0.4或0.5 m）或山梨醇（0.8或1.0 m）的培养基中进行渗透预处理（30分钟），可增强这些细胞随后在含有1 m氯化钠或2 m山梨醇的培养基中的生长。在渗透预处理培养基中加入EGTA或cch1Delta突变会降低细胞对氯化钠的耐受能力，但不会影响对高渗的适应性。短暂暴露于20 mM氯化钙可模拟高渗预处理的应激适应效应。因此，氯化钠或山梨醇诱导的高渗休克会导致Ca(2+)瞬变，该瞬变由钙内流促进，从而增强离子而非渗透应激适应。EGTA、cch1Delta突变和他克莫司（FK506）可抑制氯化钠诱导的ENA1表达，这表明Ca(2+)瞬变激活钙调神经磷酸酶信号传导以介导离子稳态和耐盐性。
