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首页> 外文期刊>Molecular and Cellular Biology >Regulation of the Saccharomyces cerevisiae HOG1 mitogen-activated protein kinase by the PTP2 and PTP3 protein tyrosine phosphatases.
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Regulation of the Saccharomyces cerevisiae HOG1 mitogen-activated protein kinase by the PTP2 and PTP3 protein tyrosine phosphatases.

机译：PTP2和PTP3蛋白酪氨酸磷酸酶对酿酒酵母HOG1丝裂原活化蛋白激酶的调节。

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In response to increases in extracellular osmolarity, Saccharomyces cerevisiae activates the HOG1 mitogen-activated protein kinase (MAPK) cascade, which is composed of a pair of redundant MAPK kinase kinases, namely, Ssk2p and Ssk22p, the MAPK kinase Pbs2p, and the MAPK Hog1p. Hog1p is activated by Pbs2p through phosphorylation of specific threonine and tyrosine residues. Activated Hog1p is essential for survival of yeast cells at high osmolarity. However, expression of constitutively active mutant kinases, such as those encoded by SSK2deltaN and PBS2(DD), is toxic and results in a lethal level of Hog1p activation. Overexpression of the protein tyrosine phosphatase Ptp2p suppresses the lethality of these mutations by dephosphorylating Hog1p. A catalytically inactive Cys-to-Ser Ptp2p mutant (Ptp2(C/S)p) is tightly bound to tyrosine-phosphorylated Hog1p in vivo. Disruption of PTP2 leads to elevated levels of tyrosine-phosphorylated Hog1p following exposure of cells to high osmolarity. Disruption of both PTP2 and another protein tyrosine phosphatase gene, PTP3, results in constitutive Hog1p tyrosine phosphorylation even in the absence of increased osmolarity. Thus, Ptp2p and Ptp3p are the major phosphatases responsible for the tyrosine dephosphorylation of Hog1p. When catalytically inactive Hog1(K/N)p is expressed in hog1delta cells, it is constitutively tyrosine phosphorylated. In contrast, Hog1(K/N)p, expressed together with wild-type Hog1p, is tyrosine phosphorylated only when cells are exposed to high osmolarity. Thus, the kinase activity of Hog1p is required for its own tyrosine dephosphorylation. Northern blot analyses suggest that Hog1p regulates Ptp2p and/or Ptp3p activity at the posttranscriptional level.
机译：响应于细胞外渗透压的增加，酿酒酵母激活HOG1丝裂原激活的蛋白激酶（MAPK）级联，该级联由一对冗余的MAPK激酶激酶，即Ssk2p和Ssk22p，MAPK激酶Pbs2p和MAPK Hog1p组成。 。通过特定的苏氨酸和酪氨酸残基的磷酸化，Pbs2p激活了Hog1p。活化的Hog1p对于高渗透压下的酵母细胞生存至关重要。但是，组成性活性突变型激酶（例如由SSK2deltaN和PBS2（DD）编码的激酶）的表达具有毒性，并导致致命的Hog1p激活水平。蛋白酪氨酸磷酸酶Ptp2p的过表达通过使Hog1p去磷酸化来抑制这些突变的致死性。催化无活性的Cys-to-Ser Ptp2p突变体（Ptp2（C / S）p）在体内与酪氨酸磷酸化的Hog1p紧密结合。细胞暴露于高渗透压后，PTP2的破坏导致酪氨酸磷酸化的Hog1p水平升高。 PTP2和另一个蛋白酪氨酸磷酸酶基因PTP3的破坏，即使没有增加的摩尔渗透压浓度，也会导致组成型Hog1p酪氨酸磷酸化。因此，Ptp2p和Ptp3p是负责Hog1p酪氨酸脱磷酸作用的主要磷酸酶。当在hog1delta细胞中表达无催化活性的Hog1（K / N）p时，它被组成型酪氨酸磷酸化。相反，仅当细胞暴露于高渗透压下时，与野生型Hog1p一起表达的Hog1（K / N）p才被酪氨酸磷酸化。因此，Hog1p的激酶活性需要自身的酪氨酸去磷酸化。 Northern印迹分析表明，Hog1p在转录后水平上调节Ptp2p和/或Ptp3p活性。

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