基于相互作用组学探讨EpCAM核移位的转运机制及其调控肿瘤进展的新功能

EpCAM在恶性肿瘤进展中具有重要调控作用，在肿瘤诊断及靶向药物开发等方面受到诸多关注。然而，EpCAM复杂的调控机制及未知的生物学功能需进一步阐明。蛋白质的相互作用组学研究是了解目标分子新功能以及空间动态修饰的可靠手段。因此，本项目基于前期SILAC-AP/MS鉴定了EpCAM互作分子网络，并结合细胞器分级提取及蛋白定位的成像数据，探索EpCAM的亚细胞定位及进入细胞核的穿梭机制及功能意义。本项目将首次揭示细胞膜蛋白EpCAM转运入细胞核的现象，重点阐明EpCAM细胞核移位的运输机制及转运入细胞核的EpCAM的全新生物学功能。通过本项目研究，将有望揭示EpCAM新的亚细胞定位、空间动态调节以及全新的生物学功能，丰富EpCAM的理论基础研究，为基于EpCAM分子功能的肿瘤诊断及靶向治疗提供新的思路。

EpCAM is reckoned as a multi-functional tumor antigen involved in the regulation of malignant behavior of carcinoma cells, receiving considerable attention as a prognostic marker and a therapeutic target. However, there is unsolved discrepancy in the regulatory role and the prognostic value of EpCAM, which is remained unclear and requires further investigation. Herein we identified by SILAC-AP/MS a high-confidence EpCAM interactome consisting 77 novel interactors. We aim to integrate fractionated organelles analysis, protein-protein interaction network analysis and imaging of protein localization to uncover EpCAM subcellular localization and novel functions. Based on EpCAM interactome and previous investigation, we propose that the cell membrane-embedded EpCAM, through internalization utilizing endosome transport system as vehicle, transportin-1 as driver, translocates to the nucleus, where it binds to CCR4-NOT complex subunit CNOT1, leading to SLUG change through transcriptional reprogramming. This study focuses on 3 parts: The novel subcellular localization of EpCAM in endosome transport system and nucleus; The mechanism for nuclear entry of EpCAM; And the functional consequences of EpCAM nuclear translocation. This study will describe a novel function for EpCAM in transcriptional modulation through nuclear translocation of the internalized EpCAM and complex formation with CCR4-NOT transcription modulators. Given the importance of EpCAM in tumor development, this work will contribute to our understanding of molecular mechanism of EpCAM in cancer, and provide comprehensive insight into the future application in EpCAM-based translational medicine.