Two novel phosphorylation sites on FKHR that are critical for its nuclear exclusion
Two novel phosphorylation sites on FKHR that are critical for its nuclear exclusion
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DOI：
10.1093/emboj/21.9.2263
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发表时间：
2002-05-01
期刊：
影响因子：
11.4
通讯作者：
Cohen, P
中科院分区：
文献类型：
--
作者：
Rena, G;Woods, YL;Cohen, P
FKHR在Thr24， Ser256和Ser319位点被蛋白激酶B （PKB）磷酸化，以响应生长因子，刺激该转录因子的核退出和失活。在这里，我们确定了另外两个残基，Ser322和Ser325，它们在胰岛素样生长因子-1 （IGF-1）刺激的细胞中被磷酸化，并由磷脂酰肌醇3激酶依赖性pkb催化的Ser319磷酸化介导。Ser319的磷酸化形成了CK1磷酸化的一致序列，使其能够磷酸化Ser322，进而启动CK1催化的Ser325的磷酸化。IGF-1在胚胎干细胞（ES）中刺激Thr24、Ser256、Ser319、Ser322和Ser325的磷酸化，但在PDK1-/- ES细胞中没有，这提供了PDK1 （PKB的上游激活因子）是哺乳动物细胞中FKHR磷酸化所必需的遗传学证据。相反，Ser329的磷酸化不受IGF-1的影响，并且在PDK1-/- ES细胞中该位点的磷酸化不降低。Ser319, Ser322， Ser325和Ser329的磷酸化位点簇似乎通过控制FKHR与介导这一过程的含ran蛋白复合物的相互作用来加速核输出。
FKHR is phosphorylated by protein kinase B (PKB) at Thr24, Ser256 and Ser319 in response to growth factors, stimulating the nuclear exit and inactivation of this transcription factor. Here we identify two further residues, Ser322 and Ser325, that become phosphorylated in insulin-like growth factor-1 (IGF-1)-stimulated cells and which are mediated by the phosphatidylinositol 3-kinase-dependent PKB-catalysed phosphorylation of Ser319. Phosphorylation of Ser319 forms a consensus sequence for phosphorylation by CK1, allowing it to phosphorylate Ser322, which in turn primes the CK1-catalysed phosphorylation of Ser325. IGF-1 stimulates the phosphorylation of Thr24, Ser256, Ser319, Ser322 and Ser325 in embryonic stem (ES) cells, but not in PDK1-/- ES cells, providing genetic evidence that PDK1 (the upstream activator of PKB) is required for the phosphorylation of FKHR in mammalian cells. In contrast, the phosphorylation of Ser329 is unaffected by IGF-1 and the phosphorylation of this site is not decreased in PDK1-/- ES cells. The cluster of phosphorylation sites at Ser319, Ser322, Ser325 and Ser329 appears to accelerate nuclear export by controlling the interaction of FKHR with the Ran-containing protein complex that mediates this process.