Intracellular sequestration of sodium by a novel Na+/H+ exchanger in yeast is enhanced by mutations in the plasma membrane H+-ATPase - Insights into mechanisms of sodium tolerance
Intracellular sequestration of sodium by a novel Na+/H+ exchanger in yeast is enhanced by mutations in the plasma membrane H+-ATPase - Insights into mechanisms of sodium tolerance
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DOI：
10.1074/jbc.272.42.26145
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发表时间：
1997-10-17
影响因子：
4.8
通讯作者：
Rao, R
中科院分区：
文献类型：
--
作者：
Nass, R;Cunningham, KW;Rao, R
酵母的钠耐受性被钙调磷酸酶突变破坏，钙调磷酸酶是一种 Ca2+/钙调蛋白依赖性蛋白磷酸酶，它是调节 Na+ 摄取和流出机制所必需的。通过选择钙调神经磷酸酶突变抑制剂，分离出 5 个耐 Na+ 突变体，并定位到编码质膜 H+-ATP 酶的 PMA1 基因，一个 突变体 pma1-alpha 4 在 ATP 酶催化域内的高度保守位点具有单一氨基酸变化 Glu(367) --> Lys，对其进行了详细分析，以确定 Na+ 耐受的机制。暴露于培养基中的 Na+ 后，pma1 突变体中的 Na-22 流入量相对于对照减少了 2 倍，与 ATP 酶活性的类似下降一致，pma1 突变体中完整细胞的 Na-22 流出量相对不变。然而，质膜的选择性透化显示突变细胞在缓慢交换池中保留高达 80% 的细胞内 Na+，我们显示 NHX1 是一种与哺乳动物 Na+/H+ 交换器 NHE 家族同源的新基因，是酵母中 Na+ 隔离所必需的，并有助于 pma1-α 4 的 Na+ 耐受表型。
Sodium tolerance in yeast is disrupted by mutations in calcineurin, a Ca2+/calmodulin dependent protein phosphatase, which is required for modulation of Na+ uptake and efflux mechanisms, Five Na+-tolerant mutants were isolated by selecting for suppressors of calcineurin mutations, and mapped to the PMA1 gene, encoding the plasma membrane H+-ATPase, One mutant, pma1-alpha 4, which has the single amino acid change Glu(367) --> Lys at a highly conserved site within the catalytic domain of the ATPase, was analyzed in detail to determine the mechanism of Na+ tolerance. After exposure to Na+ in the culture medium, Na-22 influx in the pma1 mutant was reduced 2-fold relative to control, consistent with a similar decrease in ATPase activity, Efflux of Na-22 from intact cells was relatively unchanged in the pma1 mutant, However, selective permeabilization of the plasma membrane revealed that mutant cells retained up to 80% of intracellular Na+ within a slowly exchanging pool, We show that NHX1, a novel gene homologous to the mammalian NHE family of Na+/H+ exchangers, is required for Na+ sequestration in yeast and contributes to the Na+-tolerant phenotype of pma1-alpha 4.