Abnormal localization and accumulation of FLT3-ITD, a mutant receptor tyrosine kinase involved in leukemogenesis
Abnormal localization and accumulation of FLT3-ITD, a mutant receptor tyrosine kinase involved in leukemogenesis
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DOI：
10.1159/000118788
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发表时间：
2008-01-01
影响因子：
2.7
通讯作者：
Thiede, Christian
中科院分区：
文献类型：
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作者：
Koch, Sina;Jacobi, Angela;Thiede, Christian
突变型跨膜受体的异常亚细胞定位越来越被认为是导致转化的信号质量改变的可能机制。有证据表明，突变的III亚类受体酪氨酸激酶，例如血小板衍生生长因子受体（PDGFR）和KIT蛋白，异常地定位于人类癌症中。为了进一步分析这一现象，我们研究了FLT 3的定位，FLT 3是一种在白血病中经常突变的III类受体酪氨酸激酶。通过免疫荧光染色和共聚焦激光扫描显微镜，我们发现，在逆转录病毒转导的COS 7细胞，野生型FLT 3受体蛋白主要定位于细胞表面。相反，具有内部串联重复（ITD）的突变型FLT 3受体蛋白在核周区域中积累，并且在质膜处不可检测。令人惊讶的是，与先前发表的数据相反，细胞内FLT 3-ITD积累既不能在内质网（ER）中检测到，也不能在高尔基体。此外，瞬时过表达本身导致野生型FLT 3受体蛋白在ER中的积累以及表面定位，这可能是由于分泌途径的过载分选机制导致的低效细胞内转运。基于我们的数据和FLT 3-ITD的未成熟糖基化模式，我们推测突变蛋白最有可能存在于ER和高尔基体之间的分泌途径的一个未鉴定的隔室中。版权所有（c）2008 S. Karger AG，巴塞尔。
Aberrant subcellular localization of mutant transmembrane receptors is increasingly acknowledged as a possible mechanism for an altered signaling quality leading to transformation. There is evidence that mutated receptor tyrosine kinases of subclass III, for example the platelet-derived growth factor receptor (PDGFR) and KIT-protein, are aberrantly localized in human cancers. In order to further analyze this phenomenon, we investigated the localization of FLT3, a subclass III receptor tyrosine kinase frequently mutated in leukemia. By immunofluorescence staining and confocal laser scanning microscopy we found that in retrovirally transduced COS7 cells, wild type FLT3 receptor protein is localized primarily at the cell surface. In contrast, a mutant FLT3 receptor protein with an internal tandem duplication (ITD) accumulates in a perinuclear region and is not detectable at the plasma membrane. Surprisingly, and in contrast to previously published data, intracellular FLT3-ITD accumulation could neither be detected in the endoplasmic reticulum (ER) nor in the Golgi apparatus. Furthermore, transient overexpression per se leads to accumulation of wild type FLT3 receptor protein in the ER in addition to surface localization, probably due to inefficient intracellular transport by the overloaded sorting machinery of the secretory pathway. Based on our data and the immature glycosylation pattern of FLT3-ITD, we speculate that the mutant protein resides most probably in an unidentified compartment of the secretory pathway between the ER and the Golgi apparatus. Copyright (c) 2008 S. Karger AG, Basel.