Mechanism of constitutive activation of FLT3 with internal tandem duplication in the juxtamembrane domain
Mechanism of constitutive activation of FLT3 with internal tandem duplication in the juxtamembrane domain
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DOI：
10.1038/sj.onc.1205332
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发表时间：
2002-04-11
期刊：
影响因子：
8
通讯作者：
Naoe, T
中科院分区：
文献类型：
--
作者：
Kiyoi, H;Ohno, R;Naoe, T
Flt3膜旁(JM)结构域的内部串联重复(ITD)是人类急性髓系白血病中最常见的突变，与白细胞增多和预后不良密切相关。先前我们报道了Flt3与ITD(Flt3/ITD)形成同源二聚体，并在酪氨酸残基上自动磷酸化，但其机制尚不清楚。在这项研究中，我们阐明了JM结构域在Flt3激活中的作用。突变的Flt3不仅含有ITD，而且含有延长或缩短的JM结构域，转化了依赖IL-3的小鼠髓系祖细胞系32D，而与JM结构域中的酪氨酸残基无关。这些突变的Flt3是结构性酪氨酸磷酸化和激活的信号转导分子，如SHC、MAP激酶和Stat5a。值得注意的是，缺失激酶和C-末端结构域的截短的Flt3/ITD与野生型(Wt)-flt3共转染32D细胞，导致了细胞的自主增殖。在这些细胞中，截短的Flt3/ITD与Wt-Flt3形成异源复合体，Wt-Flt3被结构性酪氨酸磷酸化。这些发现表明，Flt3JM结构域在受体激活中起重要作用，长度突变的JM结构域诱导非配体依赖的受体激活，但也以反式方式激活Wt-Flt3。
Internal tandem duplication (ITD) of the juxtamembrane (JM) domain of FLT3 is the most frequent mutation in human acute myeloid leukemia, and is significantly associated with leukocytosis and a poor prognosis. Previously we reported that FLT3 with ITD (FLT3/ ITD) formed a homodimer and was autophosphorylated on tyrosine residues, while the mechanism remains unclear. In this study, we elucidated the role of the JM domain in FLT3 activation. Mutant FLT3 with not only ITD but also an elongating or shortening JM domain transformed murine IL-3-dependent myeloid progenitor cell line 32D regardless of the tyrosine residues in the JM domain. These mutant FLT3s were constitutively tyrosine phosphorylated and activated signal-transduction molecules such as SHC, MAP kinase and STAT5a. Notably, co-transfection of the truncated FLT3/ITD lacking kinase and C-terminal domains with the wild type (Wt)-FLT3 into 32D cells resulted in the autonomous proliferation. In these cells, truncated FLT3/ITD generated a hetero-complex with Wt-FLT3 and Wt-FLT3 was constitutively tyrosine phosphorylated. These findings indicate that the FLT3 JM domain plays an important role in receptor activation, and that the length-mutated JM domain induces ligand-independent receptor activation but also activates Wt-FLT3 in a trans-manner.