TGF-regulated EMT

描述(申请人提供)：上皮-间充质转化(EMT)，即细胞从极化的上皮表型转变为高运动性的成纤维细胞或间充质表型，是胚胎发育的基础，可在包括纤维化和癌症在内的各种疾病中重新激活。EMT与细胞间黏附的改变、细胞外基质的重塑和增强的迁移活性有关，所有这些特性都能使肿瘤细胞转移。许多细胞因子和自分泌生长因子，包括转化生长因子？，已被认为与子宫内膜异位症有关。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”的识别和验证仍然难以捉摸。我们阐明了一种新的转录后途径，通过这种途径，转化生长因子？调节EMT诱导蛋白和EMT本身的表达。我们发现，异质性核糖核蛋白E1(HnRNP E1)与两个真正的EMT诱导转录本-2(DAB2)和白介素样EMT诱导物(ILEI)的3‘-UTR3’-UTR中的一个结构33核苷酸的TGFbeta激活翻译(BAT)元件结合，从而抑制了它们在NMuMG和EpRas细胞中的翻译，这两个细胞是建立的EMT的体外模型。在此途径中，转化生长因子？通过蛋白激酶B/Akt2的异构体特异性刺激，激活终止于hnRNP E1的Ser43磷酸化的激酶级联，诱导其从BAT元件释放，并导致DAB2和ILEI mRNAs的翻译激活。HnRNP E1表达的调节或其翻译后修饰，不仅改变了转化生长因子β介导的目标转录本的翻译激活，也改变了EMT。最近，我们已经纯化了与BAT元件结合的核糖核蛋白(MRNP)复合体，并确定延伸因子1A1(EF1A1)是这一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诱导的转录本的翻译调控构成了由hnRNP E1和EF1A1介导的转化生长因子β诱导的转录后调控子，在肿瘤发生过程中对EMT进行功能调节。本研究的目的是利用这一mRNP复合体作为转化生长因子信号转导的模型靶点，描述其对转化生长因子β蛋白合成的调控，并确定其在介导肿瘤发生和转移过程中的功能意义。

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.