State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Biochem Biophys Res Commun. 2012 May 11;421(3):468-73. doi: 10.1016/j.bbrc.2012.04.016. Epub 2012 Apr 9.
Our previous studies showed that the overexpression of Novel Oncogene with Kinase-domain (NOK)/STYK1 led to cellular transformation, tumorigenesis and metastasis. This report characterises the subcellular distribution of NOK in HeLa cells and its localisation in early endosomes. Confocal immunolocalisation studies indicated that NOK had structural subtypes and was distributed into two distinct expression patterns: a dot pattern (DP) and an aggregation pattern (AP). The results of an immunohistochemistry (IHC) analysis of pathological tissues also showed that high expression level of endogenous NOK was expressed in an aggregate-like structure in vivo. Importantly, we found that NOK was localised in endosomes and colocalised with epidermal growth factor receptor (EGFR) in activated endosomal vesicles. However, as the stimulation time increased, NOK and EGFR began to progress through different pathways. EGFR was gradually degraded after treatment with EGF for approximately 20 min, whereas NOK levels were not reduced. This result suggests that NOK mainly plays a role in facilitating the trafficking of EGFR from early endosomes to later endosomes/lysosomes. Taken together, NOK has a strong tendency towards forming aggregates, which may have physiological implications and provide the first evidence that this novel receptor kinase is colocalised with EGFR in endosomes to participate in a post-internalisation step of EGFR.
我们之前的研究表明，Novel Oncogene with Kinase-domain（NOK）/STYK1 的过表达导致了细胞转化、肿瘤发生和转移。本报告描述了 NOK 在 HeLa 细胞中的亚细胞分布及其在早期内体中的定位。共聚焦免疫荧光定位研究表明，NOK 具有结构亚型，并分布为两种不同的表达模式：点状模式（DP）和聚集模式（AP）。对病理组织进行免疫组织化学（IHC）分析的结果也表明，内源性 NOK 的高表达水平在体内以聚集样结构表达。重要的是，我们发现 NOK 位于内体中，并与表皮生长因子受体（EGFR）在活化的内体小泡中共定位。然而，随着刺激时间的增加，NOK 和 EGFR 开始通过不同的途径前进。用 EGF 处理约 20 分钟后，EGFR 逐渐降解，而 NOK 水平没有降低。这一结果表明，NOK 主要在促进 EGFR 从早期内体向晚期内体/溶酶体的运输中发挥作用。综上所述，NOK 具有强烈的聚集倾向，这可能具有生理意义，并提供了第一个证据表明这种新型受体激酶与 EGFR 在内体中共定位，参与 EGFR 的内化后步骤。
