Transmembrane Helix of Novel Oncogene with Kinase-Domain (NOK) Influences Its Oligomerization and Limits the Activation of RAS/MAPK Signaling
Transmembrane Helix of Novel Oncogene with Kinase-Domain (NOK) Influences Its Oligomerization and Limits the Activation of RAS/MAPK Signaling
复制标题
具有激酶结构域 (NOK) 的新型癌基因的跨膜螺旋影响其寡聚化并限制 RAS/MAPK 信号传导的激活
DOI：
10.1007/s10059-009-0003-5
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发表时间：
2009-01-01
影响因子：
3.8
通讯作者：
Liu, Li
中科院分区：
文献类型：
--
作者：
Li, Ying-Hua;Wang, Yin-Yin;Liu, Li
受体蛋白酪氨酸激酶（RPTK）的配体依赖性或独立寡聚化通常是受体激活和细胞内信号传导的重要步骤。具有激酶结构域（NOK）的新型癌基因是一种独特的RPTK，几乎完全缺乏外结构域，在细胞内表达并组成性激活。然而，NOK是否能形成低聚物，低聚化有什么功能，都是未知的。在这项研究中，通过去除外域（NOK Delta ECD）或包含内域（NOK- icd）产生了两个NOK缺失突变体。共免疫沉淀表明，NOK的跨膜（TM）结构域对其分子间相互作用至关重要。结果进一步表明，NOK作为低阶低聚物（二聚体和三聚体大小）的聚集比两个缺失突变体更紧密，因为NOK可以被Sulfo-EGS和甲醛交联，而两个缺失突变体只对Sulfo-EGS敏感。去除NOK TM结构域（NOK- icd）不仅显著促进了NOK的高阶寡聚化，还改变了NOK的亚细胞定位，并显著提高了NOK介导的细胞外信号调节激酶（ERK）的组成性激活。此外，NOK- icd与细胞膜上游信号分子RAS共定位，而NOK和NOK Delta ECD与细胞膜上游信号分子RAS共定位。因此，tm介导的分子间接触可能主要负责NOK的组成性激活，并有助于对RAS/MAPK信号的自抑制作用。
Ligand-dependent or independent oligomerization of receptor protein tyrosine kinase (RPTK) is often an essential step for receptor activation and intracellular signaling. The novel oncogene with kinase-domain (NOK) is a unique RPTK that almost completely lacks an ectodomain, expresses intracellularly and activates constitutively. However, it is unknown whether NOK can form oligomer or what function oligomerization would have. In this study, two NOK deletion mutants were generated by either removing the ectodomain (NOK Delta ECD) or including the endodomain (NOK-ICD). Co-immunoprecipitation demonstrated that the transmembrane (TM) domain of NOK was essential for its intermolecular interaction. The results further showed that NOK aggregated more closely as lower order oligomers (the dimer- and trimer-sized) than either deletion mutant did since NOK could be crosslinked by both Sulfo-EGS and formaldehyde, whereas either deletion mutant was only sensitive to Sulfo-EGS. Removing the NOK TM domain (NOK-ICD) not only markedly promoted higher order oligomerization, but also altered the subcellular localization of NOK and dramatically elevated the NOK-mediated constitutive activation of extracellular signal-regulated kinase (ERK). Moreover, NOK-ICD but not NOK or NOK Delta ECD was co-localized with the upstream signaling molecule RAS on cell membrane. Thus, TM-mediated intermolecular contacting may be mainly responsible for the constitutive activation of NOK and contribute to the autoinhibitory effect on RAS/MAPK signaling.