TRAF6 promotes TGFβ-induced invasion and cell-cycle regulation via Lys63-linked polyubiquitination of Lys178 in TGFβ type I receptor

Transforming growth factor β (TGFβ) can act either as a tumor promoter or a tumor suppressor in a context-dependent manner. High levels of TGFβ are found in prostate cancer tissues and correlate with poor patient prognosis. We recently identified a novel TGFβ-regulated signaling cascade in which TGFβ type I receptor (TβRI) is activated by the E3 ligase TNF-receptor-associated factor 6 (TRAF6) via the Lys63-linked polyubiquitination of TβRI. TRAF6 also contributes to activation of TNF-α-converting enzyme and presenilin-1, resulting in the proteolytic cleavage of TβRI and releasing the intracellular domain of TβRI, which is translocated to the nucleus to promote tumor invasiveness. In this report, we provide evidence that Lys178 of TβRI is polyubiquitinated by TRAF6. Moreover, our data suggest that TRAF6-mediated Lys63-linked ubiquitination of the TβRI intracellular domain is a prerequisite for TGFβ regulation of mRNA for cyclin D1 (CCND1), expression, as well as for the regulation of other genes controlling the cell cycle, differentiation, and invasiveness of prostate cancer cells.     

TGF—β与细胞周期调节

作为一类重要的生长负调节因子;TGF－β能够抑制多种类型细胞的生长,并将其阻断在GI期。TGF－β对细胞周期的调节作用是通过：（1）下调细胞周期驱动器如cyclin、cdk等的表达水平;（2）降低G1期cyclin／cdk复合物的活性;（3）调节p27、p21和p15等cdk抑制因子的表达及活性等。此外,一些原癌基因和肿瘤抑制基因的产物如c－myc、RB等也在这一过程中起着重要作用。     

TGFβ信号通路与肿瘤

TGFβ影响细胞的增殖和分化,在肿瘤发生与进展、细胞外基质形成和免疫调节等过程中发挥重要作用。TGFβ通过脑膜上的受体和胞内Smads家族向核内传递信号,调控靶基因。肿瘤中的TGFβ信号通路异常有其多样性和复杂性。近年来,TGFβ信号通路的研究取得了突破性进展,本文综述了恶性肿瘤中的TGFβ信号通路的异常。     

TGF—β与移植免疫

转化生长因子－β(transforming growth facter-β,TGF－β）是一种对细胞的生长、分化和免疫功能都有重要调节作用的多肽。在器官移植中TGF－β主要是一种负的免疫调节剂。本综述简要介绍了TGF－β与器官移植免疫排斥反应的关系。     

TGFβ signaling and cardiovascular diseases

Transforming growth factor β (TGFβ) family members are involved in a wide range of diverse functions and play key roles in embryogenesis, development and tissue homeostasis. Perturbation of TGFβ signaling may lead to vascular and other diseases. In vitro studies have provided evidence that TGFβ family members have a wide range of diverse effects on vascular cells, which are highly dependent on cellular context. Consistent with these observations genetic studies in mice and humans showed that TGFβ family members have ambiguous effects on the function of the cardiovascular system. In this review we discuss the recent advances on TGFβ signaling in (cardio)vascular diseases, and describe the value of TGFβ signaling as both a disease marker and therapeutic target for (cardio)vascular diseases.     

How Soluble GARP Enhances TGFβ Activation

GARP (glycoprotein A repetitions predominant) is a cell surface receptor on regulatory T-lymphocytes, platelets, hepatic stellate cells and certain cancer cells. Its described function is the binding and accommodation of latent TGFβ (transforming growth factor), before the activation and release of the mature cytokine. For regulatory T cells it was shown that a knockdown of GARP or a treatment with blocking antibodies dramatically decreases their immune suppressive capacity. This confirms a fundamental role of GARP in the basic function of regulatory T cells. Prerequisites postulated for physiological GARP function include membrane anchorage of GARP, disulfide bridges between the propeptide of TGFβ and GARP and connection of this propeptide to α_vβ₆ or α_vβ₈ integrins of target cells during mechanical TGFβ release. Other studies indicate the existence of soluble GARP complexes and a functionality of soluble GARP alone. In order to clarify the underlying molecular mechanism, we expressed and purified recombinant TGFβ and a soluble variant of GARP. Surprisingly, soluble GARP and TGFβ formed stable non-covalent complexes in addition to disulfide-coupled complexes, depending on the redox conditions of the microenvironment. We also show that soluble GARP alone and the two variants of complexes mediate different levels of TGFβ activity. TGFβ activation is enhanced by the non-covalent GARP-TGFβ complex already at low (nanomolar) concentrations, at which GARP alone does not show any effect. This supports the idea of soluble GARP acting as immune modulator in vivo.     

TGF—β的信号转导的调控

TGF－β家族通过调节靶基因的表达发挥作用,其细胞内信号转导通路是TGF－β的膜受体与靶基因之间的桥梁。TGF－β信号转导的调控是多层次、多水平的。凡能够调控以上信号转导过程中蛋白质－蛋白质和蛋白质－DNA相互作用的因子就能在各个环节上影响TGF－β家族的信号转导,从而产生多种多样的生物学效应。     

A taste of TGFβ in Tuscany

The recent FASEB Summer Research Conference entitled 'The TGFβ Superfamily: Signaling in Development and Disease' was held in August, 2011 in the spectacular setting of Il Ciocco, Lucca, amidst the olive trees in Tuscany, Italy. The organizers assembled an amazing forum, which included 53 speakers and 67 poster presentations from laboratories around the world, to showcase recent advances made in our understanding of the transforming growth factor-β (TGFβ) signaling pathway.     

TGF－β家族及其受体组成

ＴＧＦ－β家族及其受体组成ＴｈｅＴＧＦ－βｆａｍｉｌｙａｎｄｉｔｓｃｏｍｐｏｓｉｔｅｒｅｃｅｐｔｏｒｓＪｏａｎ　Ｍａｓｓａｇｕｅ,ＬｉｌｉａｎａＡｔｔｉｓａｎｏａｎｄＪｅｆｆｒｅｙＬＷｒａｎａ￥／／张德胜译,曹惠婷校阅（中国科学院上海生物化学研究所２...     

TGF—β家族的细胞信号转导

转化生长因子β（ＴＧＦ－β）家族成员与各自的膜受体结合后,使通路限制性（ｐａｔｈｗａｙ－ｒｅｓｔｒｉｃｔｅｄ）ＳＭＡＤｓ磷酸化,后者再与Ｓｍａｄ４形成杂聚体并转位至细胞核,调节一些基因的转录而产生生物学效应。抑制性ＳＭＡＤｓ可阻断通路限制性ＳＭＡＤｓ的磷酸化。     

Maize Ribosome-Inactivating Protein Uses Lys158–Lys161 to Interact with Ribosomal Protein P2 and the Strength of Interaction Is Correlated to the Biological Activities

Ribosome-inactivating proteins (RIPs) inactivate prokaryotic or eukaryotic ribosomes by removing a single adenine in the large ribosomal RNA. Here we show maize RIP (MOD), an atypical RIP with an internal inactivation loop, interacts with the ribosomal stalk protein P2 via Lys158–Lys161, which is located in the N-terminal domain and at the base of its internal loop. Due to subtle differences in the structure of maize RIP, hydrophobic interaction with the ‘FGLFD’ motif of P2 is not as evidenced in MOD-P2 interaction. As a result, interaction of P2 with MOD was weaker than those with trichosanthin and shiga toxin A as reflected by the dissociation constants (K_D) of their interaction, which are 1037.50±65.75 µM, 611.70±28.13 µM and 194.84±9.47 µM respectively.Despite MOD and TCS target at the same ribosomal protein P2, MOD was found 48 and 10 folds less potent than trichosanthin in ribosome depurination and cytotoxicity to 293T cells respectively, implicating the strength of interaction between RIPs and ribosomal proteins is important for the biological activity of RIPs. Our work illustrates the flexibility on the docking of RIPs on ribosomal proteins for targeting the sarcin-ricin loop and the importance of protein-protein interaction for ribosome-inactivating activity.     

Novel Lys63-linked ubiquitination of IKKβ induces STAT3 signaling

NFκB signaling plays a significant role in human disease, including breast and ovarian carcinoma, insulin resistance, embryonic lethality and liver degeneration, rheumatoid arthritis, aging and Multiple Myeloma (MM). Inhibitor of κB (IκB) kinase β (IKKβ) regulates canonical Nuclear Factor κB (NFκB) signaling in response to inflammation and cellular stresses. NFκB activation requires Lys63-linked (K63-linked) ubiquitination of upstream proteins such as NEMO or TAK1, forming molecular complexes with membrane-bound receptors. We demonstrate that IKKβ itself undergoes K63-linked ubiquitination. Mutations in IKKβ at Lys171, identified in Multiple Myeloma and other cancers, lead to a dramatic increase in kinase activation and K63-linked ubiquitination. These mutations also result in persistent activation of STAT3 signaling. Liquid chromatography (LC)-high mass accuracy tandem mass spectrometry (MS/MS) analysis identified Lys147, Lys418, Lys555 and Lys703 as predominant ubiquitination sites in IKKβ. Specific inhibition of the UBC13-UEV1A complex responsible for K63-linked ubiquitination establishes Lys147 as the predominant site of K63-ubiquitin conjugation and responsible for STAT3 activation. Thus, IKKβ activation leads to ubiquitination within the kinase domain and assemblage of a K63-ubiquitin conjugated signaling platform. These results are discussed with respect to the importance of upregulated NFκB signaling known to occur frequently in MM and other cancers.     

雌激素诱发大鼠原位与移植垂体催乳素瘤中催乳素基因与TGFα和TGF …

利用本实验室建立的１７β－雌二醇诱致Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ（ＳＤ）大鼠原位垂体和异体移植于肾囊的垂体同时形成催乳素瘤的动物模型,采用Ｎｏｒｔｈｅｍ印迹杂交方法,我们观察了Ｅ２长期作用（１２０ｄ）后诱发的原位与移植垂体ＰＲＬ瘤中ＰＲＬ基因和两种转化生长因子ＴＧＦα和ＴＧＦβ１基因表达水平的改变。结果表明：在Ｅ２长期作用后,原位垂体与异体移植于肾囊,从而远离下丘脑的垂体均可形成垂体ＰＲＬ瘤;原位     

Overexpression of Latent TGFβ Binding Protein 4 in Muscle Ameliorates Muscular Dystrophy through Myostatin and TGFβ

Latent TGFβ binding proteins (LTBPs) regulate the extracellular availability of latent TGFβ. LTBP4 was identified as a genetic modifier of muscular dystrophy in mice and humans. An in-frame insertion polymorphism in the murine Ltbp4 gene associates with partial protection against muscular dystrophy. In humans, nonsynonymous single nucleotide polymorphisms in LTBP4 associate with prolonged ambulation in Duchenne muscular dystrophy. To better understand LTBP4 and its role in modifying muscular dystrophy, we created transgenic mice overexpressing the protective murine allele of LTBP4 specifically in mature myofibers using the human skeletal actin promoter. Overexpression of LTBP4 protein was associated with increased muscle mass and proportionally increased strength compared to age-matched controls. In order to assess the effects of LTBP4 in muscular dystrophy, LTBP4 overexpressing mice were bred to mdx mice, a model of Duchenne muscular dystrophy. In this model, increased LTBP4 led to greater muscle mass with proportionally increased strength, and decreased fibrosis. The increase in muscle mass and reduction in fibrosis were similar to what occurs when myostatin, a related TGFβ family member and negative regulator of muscle mass, was deleted in mdx mice. Supporting this, we found that myostatin forms a complex with LTBP4 and that overexpression of LTBP4 led to a decrease in myostatin levels. LTBP4 also interacted with TGFβ and GDF11, a protein highly related to myostatin. These data identify LTBP4 as a multi-TGFβ family ligand binding protein with the capacity to modify muscle disease through overexpression.     

TGFβ and matrix-regulated epithelial to mesenchymal transition

Background

The progression of cancer through stages that guide a benign hyperplastic epithelial tissue towards a fully malignant and metastatic carcinoma, is driven by genetic and microenvironmental factors that remodel the tissue architecture. The concept of epithelial–mesenchymal transition (EMT) has evolved to emphasize the importance of plastic changes in tissue architecture, and the cross-communication of tumor cells with various cells in the stroma and with specific molecules in the extracellular matrix (ECM).

Scope of the review

Among the multitude of ECM-embedded cytokines and the regulatory potential of ECM molecules, this article focuses on the cytokine transforming growth factor β (TGFβ) and the glycosaminoglycan hyaluronan, and their roles in cancer biology and EMT. For brevity, we concentrate our effort on breast cancer.

Major conclusions

Both normal and abnormal TGFβ signaling can be detected in carcinoma and stromal cells, and TGFβ-induced EMT requires the expression of hyaluronan synthase 2 (HAS2). Correspondingly, hyaluronan is a major constituent of tumor ECM and aberrant levels of both hyaluronan and TGFβ are thought to promote a wounding reaction to the local tissue homeostasis. The link between EMT and metastasis also involves the mesenchymal–epithelial transition (MET). ECM components, signaling networks, regulatory non-coding RNAs and epigenetic mechanisms form the network of regulation during EMT-MET.

General significance

Understanding the mechanism that controls epithelial plasticity in the mammary gland promises the development of valuable biomarkers for the prognosis of breast cancer progression and even provides new ideas for a more integrative therapeutic approach against disease. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.     

TGF—β超家族信号传导机制研究进展

ＴＧＦ－β超家族由一大类具有共同生物学特性的细胞因子所组成,在生长控制、物质代谢等方面均有极其重要的作用。它们与Ⅱ型受体和Ⅰ型受体形成异在聚体复合物后激活Ⅰ型受体,然后通过被称为ＳＭＡＤ蛋白的信号蛋白,将信号从细胞浆转导到细胞核中。