Phosphorylation of the transcription factor forkhead family member FKHR by protein kinase B
Phosphorylation of the transcription factor forkhead family member FKHR by protein kinase B
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DOI：
10.1074/jbc.274.24.17179
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发表时间：
1999-06-11
影响因子：
4.8
通讯作者：
Cohen, P
中科院分区：
文献类型：
--
作者：
Rena, G;Guo, SD;Cohen, P
蛋白激酶 B 位于磷脂酰肌醇 (PtdIns) 3-激酶的“下游”，被认为介导胰岛素和其他生长因子的许多细胞内作用。在这里，我们表明，FKHR（秀丽隐杆线虫中 DAF16 转录因子的人类同源物）在体外被人蛋白激酶 B α (PKB α) 在 Thr-24、Ser-256 和 Ser-319 处快速磷酸化，且比 BAD 快得多，BAD 被认为是 PKB 的生理底物。相同的三个位点均位于规范的 PKB 共有序列中(Arg-Xaa-Arg-Xaa-Xaa-(Ser/Thr))，当 FKHR 与 PKB 或 PDK1（PKB 的上游激活剂）共转染时被磷酸化，当用胰岛素样生长因子 1 (IGF-1) 刺激 293 细胞时，所有三个残基被磷酸化，IGF-1 诱导的磷酸化被 PtdIns 3 激酶消除渥曼青霉素抑制剂，但不是 PD 98059（丝裂原激活蛋白激酶级联的抑制剂）或雷帕霉素。这些结果表明 FKHR 是 PKB 的生理底物，并且它可能介导 PKB 对基因表达的一些生理作用。已知 DAF16 是信号传导途径的一个组成部分，该信号传导途径已被部分基因剖析，包括胰岛素/IGF-1 受体的同源物、PtdIns 8-激酶和 PKB。DAF16 中 Thr-24、Ser-256 和 Ser-319 及其周围序列的保守性因此表明 DAF16 也是线虫中 PKB 的直接底物。
Protein kinase B lies "downstream" of phosphatidylinositide (PtdIns) 3-kinase and is thought to mediate many of the intracellular actions of insulin and other growth factors. Here we show that FKHR, a human homologue of the DAF16 transcription factor in Caenorhabditis elegans, is rapidly phosphorylated by human protein kinase B alpha (PKB alpha) at Thr-24, Ser-256, and Ser-319 in vitro and at a much faster rate than BAD, which is thought to be a physiological substrate for PKB, The same three sites, which all lie in the canonical PKB consensus sequences (Arg-Xaa-Arg-Xaa-Xaa-(Ser/Thr)), became phosphorylated when FKHR was cotransfected with either PKB or PDK1 (an upstream activator of PKB), All three residues became phosphorylated when 293 cells were stimulated with insulin-like growth factor 1 (IGF-1), The IGF-1-induced phosphorylation was abolished by the PtdIns 3-kinase inhibitor wortmannin but not by PD 98059 (an inhibitor of the mitogen-activated protein kinase cascade) or by rapamycin, These results indicate that FKHR is a physiological substrate of PKB and that it may mediate some of the physiological effects of PKB on gene expression. DAF16 is known to be a component of a signaling pathway that has been partially dissected genetically and includes homologues of the insulin/IGF-1 receptor, PtdIns 8-kinase and PKB, The conservation of Thr-24, Ser-256, and Ser-319 and the sequences surrounding them in DAF16 therefore suggests that DAF16 is also a direct substrate for PKB in C, elegans.