Constitutive activation of Stat5 promotes its cytoplasmic localization and association with PI3-kinase in myeloid leukemias
Constitutive activation of Stat5 promotes its cytoplasmic localization and association with PI3-kinase in myeloid leukemias
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DOI：
10.1182/blood-2006-01-029918
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发表时间：
2007-02-15
期刊：
影响因子：
20.3
通讯作者：
Gouilleux, Fabrice
中科院分区：
文献类型：
--
作者：
Harir, Noria;Pecquet, Christian;Gouilleux, Fabrice
STAT5的持续激活常见于血液肿瘤。对构成活性的Stat5突变体(Stat51*6和CS5(F))进行的研究表明，解除调控的Stat5活性促进了白血病的发生。为了研究这些突变体的致癌特性，我们使用了表达CS5(F)的骨髓细胞，当移植到受体小鼠中时，这些细胞诱导了多系白血病。在这里，我们通过免疫细胞化学显示，CS5(F)主要定位于白血病细胞的细胞质中，提示cS5F的转化性质可能与细胞质功能有关。为了支持这一假说，我们发现在白血病骨髓细胞中，cS5F与磷脂酰肌醇3-激酶(P13-K)的P85亚单位和支架接头Gab2形成一个复合体，导致P13-K的关键下游靶点Akt/PKB的激活。通过使用可转导的TAT-Gab2或TAT-Akt重组蛋白，我们能够证明CS5(F)分子通过Gab2激活P13-Kinase/Akt通路是诱导细胞生长所必需的。我们还发现，髓系白血病患者原代细胞中持续磷酸化的Stat5具有细胞质定位。这些数据表明，致癌的Stat5蛋白不仅作为转录激活因子，而且作为细胞质信号效应因子，具有双重转化能力。
Persistent activation of Stat5 is frequently found in hematologic neoplasms. Studies conducted with constitutively active Stat5 mutants (Stat51*6 and cS5(F)) have shown that deregulated Stat5 activity promotes leukemogenesis. To investigate the oncogenic properties of these mutants, we used cS5(F)-expressing bone marrow cells which induce a multilineage leukemia when transplanted into recipient mice. Here, we show by immunocytochemistry that cS5(F) is localized mainly in the cytoplasmic compartment of leukemic cells, suggesting that the transforming nature of cS5F may be associated with a cytoplasmic function. In support of this hypothesis, we found that cS5F forms a complex with the p85 subunit of the phosphatidylinositol 3-kinase (P13-K) and the scaffolding adapter Gab2 in leukemic bone marrow cells, resulting in the activation of Akt/PKB, a crucial downstream target of P13-K. By using transducible TAT-Gab2 or TAT-Akt recombinant proteins, we were able to demonstrate that activation of the P13-kinase/Akt pathway by cS5(F) mol- ecules through Gab2 is essential for induction of cell growth. We also found that persistently phosphorylated Stat5 in primary cells from patients with myeloid leukemias has a cytoplasmic localization. These data suggest that oncogenic Stat5 proteins exert dual transforming capabilities not only as transcriptional activators but also as cytoplasmic signaling effectors.