Integration of stress responses:: Modulation of calcineurin signaling in Saccharomyces cerevisiae by protein kinase A
Integration of stress responses:: Modulation of calcineurin signaling in Saccharomyces cerevisiae by protein kinase A
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DOI：
10.1128/ec.3.5.1147-1153.2004
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发表时间：
2004-10-01
期刊：
影响因子：
--
通讯作者：
Cyert, MS
中科院分区：
文献类型：
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作者：
Kafadar, KA;Cyert, MS
钙调磷酸酶是酿酒酵母适应各种环境胁迫所必需的一种钙/钙调素依赖性蛋白磷酸酶。一旦被激活，钙调磷酸酶使锌指转录因子Crz 1 p/Tcn 1 p去磷酸化，使其在细胞核中积累，并激活基因表达。在这里，我们表明，环AMP依赖性蛋白激酶A（PKA）磷酸化和负调控Crz 1 p活性抑制其核进口。PKA在体内的激活降低了Crz 1 p依赖的转录。PKA在体外磷酸化Crz 1 p，我们确定了这种磷酸化所需的特定残基，所有这些残基都位于或邻近核定位信号。这些残基突变为丙氨酸导致Crz 1 p的核输入增加，并导致更高水平的基础和Ca 2+诱导的Crz 1 p转录活性。PKA调节酵母的一般应激反应，并协调这种反应与营养的可用性。相反，钙调神经磷酸酶调节细胞对一组有限的环境损伤的反应。因此，这些研究确定了一种特定的生化机制，通过该机制，多种应激激活的信号通路的活性在体内被整合。
Calcineurin is a Ca2+/calmodulin-dependent protein phosphatase required for Saccharomyces cerevisiae to adapt to a variety of environmental stresses. Once activated, calcineurin dephosphorylates the Zn-finger transcription factor Crz1p/Tcn1p, causing it to accumulate in the nucleus where it activates gene expression. Here we show that cyclic AMP-dependent protein kinase A (PKA) phosphorylates and negatively regulates Crz1p activity by inhibiting its nuclear import. Activation of PKA in vivo decreases Crz1p-dependent transcription. PKA phosphorylates Crz1p in vitro, and we identify specific residues required for this phosphorylation, all of which reside in or adjacent to the nuclear localization signal. Mutation of these residues to alanine results in increased nuclear import of Crz1p and results in higher levels of both basal and Ca2+-induced Crz1p transcriptional activity. PKA regulates the general stress response in yeast and coordinates this response with nutrient availability. In contrast, calcineurin regulates the cellular response to a restricted set of environmental insults. Thus, these studies identify a specific biochemical mechanism through which the activities of multiple stress-activated signaling pathways are integrated in vivo.