TGF-regulated EMT

描述（由申请人提供）：上皮-间充质转化（EMT），细胞经历从极化上皮表型到高度运动的成纤维细胞或间充质表型的转换，是胚胎发育的基础，可以在包括纤维化和癌症在内的多种疾病中被重新激活。EMT与细胞间粘附的改变、细胞外基质的重塑和迁移活性的增强有关，所有这些特性都使肿瘤细胞能够转移。多种细胞因子和自分泌生长因子，包括TGF？，都与急诊医疗有牵连。尽管对人类肿瘤进行了密集的转录阵列分析，但“EMT特征基因”的身份和验证仍然难以捉摸。我们已经阐明了一种新的转录后途径，TGF？调节EMT诱导蛋白和EMT本身的表达。我们发现，异质核核糖核蛋白E1 （hnRNP E1）与两种EMT诱导剂的3'-UTR中的一个结构的、33个核苷酸的tgf β激活翻译（BAT）元件结合，即disable2 （Dab2）和白细胞介素样EMT诱导剂（ILEI），从而抑制它们在NMuMG和EpRas细胞（两种体外EMT模型）中的翻译。在这个通路中，TGF？通过异构体特异性刺激蛋白激酶B¿/Akt2激活终止于hnRNP E1 Ser43磷酸化的激酶级联，诱导其从BAT元件释放并引起Dab2和ILEI mrna的翻译激活。hnRNP E1表达的调节，或其翻译后修饰，不仅改变TGF介导的靶转录物的翻译激活，也改变EMT。最近，我们纯化了与BAT元件结合的核糖核蛋白（mRNP）复合物，并鉴定了延伸因子1A1 （EF1A1）作为这种翻译沉默途径的第二个功能成分。我们假设Dab2和ILEI以及其他EMT诱导剂转录物的翻译调控构成了由hnRNP E1和EF1A1介导的TGF诱导的转录后调控，在肿瘤发生过程中对EMT进行功能调控。本研究的目的是利用该mRNP复合物作为TGF¿信号传导的模型靶点，描述其在TGF¿响应下对蛋白质合成的调节，并确定其在介导肿瘤发生和转移进展中的功能意义。

DESCRIPTION (provided by applicant): The epithelial-mesenchymal transition (EMT), in which cells undergo a switch from a polarized, epithelial phenotype to a highly motile fibroblastic or mesenchymal phenotype is fundamental during embryonic development and can be reactivated in a variety of diseases including fibrosis and cancer. EMT is associated with changes in cell-cell adhesion, remodeling of extracellular matrix, and enhanced migratory activity, all properties that enable tumor cells to metastasize. Numerous cytokines and autocrine growth factors, including TGF?, have been implicated in EMT. Despite intensive transcriptional array analysis of human tumors, the identity and validation of 'EMT signature genes' remains elusive. We have elucidated a novel, post-transcriptional pathway by which TGF? modulates expression of EMT-inducer proteins and EMT itself. We identified that heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1) binds to a structural, 33-nucleotide TGFbeta-activated translation (BAT) element in the 3'-UTR of two bona fide EMT-inducer transcripts, disabled-2 (Dab2) and interleukin-like EMT inducer (ILEI), thereby repressing their translation in NMuMG and EpRas cells, two established in vitro models of EMT. In this pathway, TGF? activates a kinase cascade terminating in phosphorylation of Ser43 of hnRNP E1 by isoform-specific stimulation of protein kinase B¿/Akt2, inducing its release from the BAT element and causing translational activation of Dab2 and ILEI mRNAs. Modulation of hnRNP E1 expression, or its post-translational modification, alters not only TGF¿-mediated translational activation of the target transcripts, but also EMT. Recently, we have purified the ribonucleoprotein (mRNP) complex binding to the BAT element and have identified elongation factor 1A1 (EF1A1) as a second, functional component of this translational silencing pathway. We hypothesize that translational regulation of Dab2 and ILEI, as well as other EMT-inducer transcripts, constitutes a TGF¿-inducible post-transcriptional regulon mediated by hnRNP E1 and EF1A1, which functionally regulates EMT during tumorigenesis. The goal of this proposal is to use this mRNP complex as a model target of TGF¿ signaling, to delineate its regulation of protein synthesis in response to TGF¿ and to determine its functional significance in mediating tumorigenesis and metastatic progression. PUBLIC HEALTH RELEVANCE: The epithelial-mesenchymal transition (EMT) is a fundamental process during normal embryonic development but it can also be aberrantly re-activated in a variety of diseases including fibrosis and cancer. TGF¿ is one of the growth factors implicated in EMT. The successful pursuit of the studies proposed herein will elucidate the molecular mechanism through which TGF¿ mediates EMT and will provide insight into the design of strategies and therapeutics aimed at its prevention in pathological situations.