Involvement of 3-phosphoinositide-dependent protein kinase-1 in the MEK/MAPK signal transduction pathway
Involvement of 3-phosphoinositide-dependent protein kinase-1 in the MEK/MAPK signal transduction pathway
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DOI：
10.1074/jbc.m402055200
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发表时间：
2004-08-06
影响因子：
4.8
通讯作者：
Tsuruo, T
中科院分区：
文献类型：
--
作者：
Sato, S;Fujita, N;Tsuruo, T
磷脂酰肌醇-3-OH激酶/3-磷酸肌醇依赖性蛋白激酶-1（PDK 1）/Akt和Raf/丝裂原活化蛋白激酶（MAPK/ERK）激酶（MEK）/丝裂原活化蛋白激酶（MAPK）途径在细胞存活和增殖的调节中具有中心作用。尽管它们的重要性，但是，这两种途径之间的串扰尚未得到充分理解。在这里，我们报告说，PDK 1促进MAPK激活的MEK依赖性的方式。体外激酶活性测定表明，MAPK通路中PDK 1的直接靶点是上游MAPK激酶MEK 1和MEK 2。在MEK 1和MEK 2中鉴定的PDK 1磷酸化位点分别为Ser（222）和Ser（226），并且已知对于完全活化是必需的。迄今为止，这些位点被认为是由Raf激酶磷酸化的。然而，使用小干扰RNA的PDK 1基因沉默表明，PDK 1与维持稳态磷酸化MEK水平和细胞生长相关。小干扰RNA介导的PDK 1下调减弱了MEK和MAPK的最大活性，但不能延长MAPK信号转导持续时间。组成型活性MEK 1的稳定和瞬时表达克服了这些影响。我们的研究结果表明磷脂酰肌醇-3-OH激酶/PDK 1/Akt通路和Raf/MEK/MAPK通路之间存在一种新的串扰。
The phosphatidylinositide-3-OH kinase/3-phosphoinositide-dependent protein kinase-1 (PDK1)/Akt and the Raf/mitogen-activated protein kinase (MAPK/ERK) kinase (MEK)/mitogen-activated protein kinase ( MAPK) pathways have central roles in the regulation of cell survival and proliferation. Despite their importance, however, the cross-talk between these two pathways has not been fully understood. Here we report that PDK1 promotes MAPK activation in a MEK-dependent manner. In vitro kinase assay revealed that the direct targets of PDK1 in the MAPK pathway were the upstream MAPK kinases MEK1 and MEK2. The identified PDK1 phosphorylation sites in MEK1 and MEK2 are Ser(222) and Ser(226), respectively, and are known to be essential for full activation. To date, these sites are thought to be phosphorylated by Raf kinases. However, PDK1 gene silencing using small interference RNA demonstrates that PDK1 is associated with maintaining the steady-state phosphorylated MEK level and cell growth. The small interference RNA-mediated down-regulation of PDK1 attenuated maximum MEK and MAPK activities but could not prolong MAPK signaling duration. Stable and transient expression of constitutively active MEK1 overcame these effects. Our results suggest a novel cross-talk between the phosphatidylinositide-3-OH kinase/PDK1/Akt pathway and the Raf/MEK/MAPK pathway.