Department of Molecular and Cellular Oncology, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Biochem Biophys Res Commun. 2010 Sep 3;399(4):498-504. doi: 10.1016/j.bbrc.2010.07.096. Epub 2010 Jul 30.
Emerging evidence indicates that cell surface receptors, such as the entire epidermal growth factor receptor (EGFR) family, have been shown to localize in the nucleus. A retrograde route from the Golgi to the endoplasmic reticulum (ER) is postulated to be involved in the EGFR trafficking to the nucleus; however, the molecular mechanism in this proposed model remains unexplored. Here, we demonstrate that membrane-embedded vesicular trafficking is involved in the nuclear transport of EGFR. Confocal immunofluorescence reveals that in response to EGF, a portion of EGFR redistributes to the Golgi and the ER, where its NH(2)-terminus resides within the lumen of Golgi/ER and COOH-terminus is exposed to the cytoplasm. Blockage of the Golgi-to-ER retrograde trafficking by brefeldin A or dominant mutants of the small GTPase ADP-ribosylation factor, which both resulted in the disassembly of the coat protein complex I (COPI) coat to the Golgi, inhibit EGFR transport to the ER and the nucleus. We further find that EGF-dependent nuclear transport of EGFR is regulated by retrograde trafficking from the Golgi to the ER involving an association of EGFR with gamma-COP, one of the subunits of the COPI coatomer. Our findings experimentally provide a comprehensive pathway that nuclear transport of EGFR is regulated by COPI-mediated vesicular trafficking from the Golgi to the ER, and may serve as a general mechanism in regulating the nuclear transport of other cell surface receptors.
新出现的证据表明，细胞表面受体，如整个表皮生长因子受体（EGFR）家族，已经被证明定位于细胞核中。从高尔基体到内质网（ER）的逆行途径被认为参与了 EGFR 向核内的运输；然而，该模型中的分子机制仍未被探索。在这里，我们证明了膜嵌入式囊泡运输参与了 EGFR 的核内运输。共聚焦免疫荧光显示，在 EGF 的作用下，一部分 EGFR 重新分布到高尔基体和内质网，其 NH2 端位于高尔基体/内质网的腔室内，COOH 端暴露在细胞质中。布雷菲德菌素 A 或小 GTP 酶 ADP-核糖基化因子的显性突变体阻断高尔基体到内质网的逆行运输，这两种方法都导致衣壳蛋白复合物 I（COP I）衣壳在高尔基体上解体，从而抑制 EGFR 向内质网和细胞核的运输。我们进一步发现，EGF 依赖性 EGFR 的核内运输受从高尔基体到内质网的逆行运输调节，涉及 EGFR 与 COPI 衣壳蛋白复合物的一个亚基γ-COP 的结合。我们的研究结果从实验上提供了一个全面的途径，即 EGFR 的核内运输是由 COPI 介导的从高尔基体到内质网的囊泡运输调节的，这可能是调节其他细胞表面受体核内运输的一般机制。
