Mechanisms of STAT Protein Activation by Oncogenic KIT Mutants in Neoplastic Mast Cells
Mechanisms of STAT Protein Activation by Oncogenic KIT Mutants in Neoplastic Mast Cells
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DOI：
10.1074/jbc.m110.182642
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发表时间：
2011-02-25
影响因子：
4.8
通讯作者：
De Sepulveda, Paulo
中科院分区：
文献类型：
--
作者：
Chaix, Amandine;Lopez, Sophie;De Sepulveda, Paulo
c-kit基因突变发生在绝大多数肥大细胞增多症中。在成年患者以及肥大细胞肿瘤细胞系中，突变几乎只发生在KIT激酶结构域内的氨基酸816上。在KIT信号传导的下游效应物中，STAT3和STAT5已被证明对KIT- asp（816）突变蛋白引发的细胞增殖至关重要。然而，对STAT蛋白的激活机制知之甚少。在这项研究中，我们确定并阐明了各种STAT激酶在两种广泛使用的肿瘤肥大细胞系P815和hcc -1中的作用。我们发现STAT1、-3和-5蛋白在KIT-Asp（816）突变体的下游被激活。所有三种STAT蛋白都位于细胞核中，并在丝氨酸残基上磷酸化。KIT-Asp（816）突变体可以直接磷酸化体外激活特异性酪氨酸残基上的STATs。然而，在细胞内，SRC家族激酶和jak不同地促进KIT突变体下游STAT蛋白的酪氨酸磷酸化。使用一组抑制剂，我们提供了丝氨酸/苏氨酸激酶暗示或排除在两种细胞系中负责STAT1， -3和-5的丝氨酸磷酸化的证据。最后，我们发现只有STAT5在这些细胞中具有转录活性。这表明KIT突变体下游的STAT1和STAT3的贡献与它们的转录因子功能无关。
Mutations in the c-kit gene occur in the vast majority of mastocytosis. In adult patients as well as in the cell line derived from mast cell neoplasms, the mutations occur almost exclusively at amino acid 816 within the kinase domain of KIT. Among the downstream effectors of KIT signaling, STAT3 and STAT5 have been shown to be critical for cell proliferation elicited by the KIT-Asp(816) mutant protein. However, little is known about the mechanisms of activation of STAT proteins. In this study, we identify and clarify the contribution of various STAT kinases in two widely used neoplastic mast cell lines, P815 and HMC-1. We show that STAT1, -3, and -5 proteins are activated downstream of the KIT-Asp(816) mutant. All three STAT proteins are located in the nucleus and are phosphorylated on serine residues. KIT-Asp(816) mutant can directly phosphorylate STATs on the activation-specific tyrosine residues in vitro. However, within cells, SRC family kinases and JAKs diversely contribute to tyrosine phosphorylation of STAT proteins downstream of the KIT mutant. Using a panel of inhibitors, we provide evidence for the implication or exclusion of serine/threonine kinases as responsible for serine phosphorylation of STAT1, -3, and -5 in the two cell lines. Finally, we show that only STAT5 is transcriptionally active in these cells. This suggests that the contribution of STAT1 and STAT3 downstream of KIT mutant is independent of their transcription factor function.