Molecular Mechanisms of TGF-beta Signaling Pathway

TGF-β信号通路的分子机制

• 批准号: 8763099
• 负责人: YING E Zhang
• 金额: $ 70.04万
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8763099
• 关键词: Accounting; Activins; Apoptosis; Binding; Biological; Bone Morphogenetic Proteins; C-terminal; Cell Differentiation process; Cell Proliferation; Cell physiology; Cell surface; Complement; Complex; Development; Disease; Epigenetic Process; Family; Family member; Genetic; Goals; Growth Factor; Human; Lead; MAP Kinase Gene; MAPK14 gene; MAPK8 gene; Malignant Neoplasms; Mediating; Membrane; Mitogen-Activated Protein Kinases; Molecular; Mono-S; Neoplasm Metastasis; Oncogenic; Outcome; Pathway interactions; Peptides; Phosphorylation; Proteins; Proteomics; Receptor Serine/Threonine Kinase; Receptor Signaling; Regulation; Reporting; Research; Role; Serine; Signal Pathway; Signal Transduction; Site; Smad Proteins; Smad protein; Staging; TGF-beta type I receptor; TRAF6 gene; Transforming Growth Factor beta; Transforming Growth Factor beta Receptors; Tumor Suppressor Proteins; Ubiquitination; cancer cell; cell growth; member; novel; promoter; response; tumorigenesis

Through the action of its membrane bound type I receptor, TGF-beta elicits a wide range of cellular responses that regulate cell proliferation, differentiation and apoptosis in the context-dependent manner. Many of these signaling responses are mediated by Smad proteins. As such, controlling Smad activity is crucial for proper signaling by TGF-beta and its related factors. We found that TGF-beta induces phosphorylation at three sites in the linker region of Smad3 in addition to the two C-terminal serine residues. These linker sites can also be phosphorylated by MAPK and CDKs in response to growth factor stimulation or oncogenic Ras activation. In addition, Smad3 is also subjected to Smurf2-mediated mono-ubiquitination that inhibits its activity through blocking complex formation with Smad4. We found that phosphorylation of the linker T179 is required for Smad3 to interact with Smurf2 and undergo Smurf2-mediated ubiquitination. Therefore, Smad3 linker phosphorylation decreases Smad complex formation and transcriptional activity. In many types of cancer cells, the Smad3 linker sites are constitutively phosphorylated. We are currently investigating if changes in the linker phosphorylation of Smad3 contribute to TGF-beta switching from a tumor suppressor to a metastasis promoter. Although Smads are involved in the most actions of the TGF-beta, activated TGF-beta receptors also transduce signals through other intracellular signaling pathways. For the past several years, my group has devoted considerable effort in deciphering the specific mechanism by which TGF-beta receptors activate MAP kinases independent of Smads, and elucidating the biological significance of this Smad-independent TGF-beta signaling. Toward these goals, we found that TRAF6 is specifically required for the Smad-independent activation of JNK and p38. Currently, we are in the midst of expanding this finding to uncover additional mechanisms and pathways that function in TGF-beta signaling. We have taken a targeted proteomics approach to identify additional associated proteins of the TGF-beta type I receptor complex. We have also taken a global phosphoproteomics approach to identify differentially phosphorylated proteins associated with TGF-beta signaling using SILAC. These two approaches complement each other, and the outcome of these efforts will generate a quantitative phosphoproteomic profile of TGF-beta signaling network. We hope to uncover novel proteins that interact and/or are phosphorylated at the early stages of TGF-beta signaling. Further characterization of the candidate proteins should lead to elucidation of additional mechanisms that may account for Smad-independent TGF-beta signaling responses and advance our understanding of the ability of TGF-beta to induce a plethora of diverse biological responses.

通过其膜结合 I 型受体的作用，TGF-β 引发广泛的细胞反应，以环境依赖性方式调节细胞增殖、分化和凋亡。许多这些信号反应是由 Smad 蛋白介导的。因此，控制 Smad 活性对于 TGF-β 及其相关因子的正确信号传导至关重要。我们发现，除了两个 C 端丝氨酸残基外，TGF-β 还在 Smad3 连接区的三个位点诱导磷酸化。这些连接位点还可以响应生长因子刺激或致癌 Ras 激活而被 MAPK 和 CDK 磷酸化。此外，Smad3 还受到 Smurf2 介导的单泛素化作用，通过阻断与 Smad4 形成复合物来抑制其活性。我们发现，Smad3 与 Smurf2 相互作用并经历 Smurf2 介导的泛素化需要连接子 T179 的磷酸化。因此，Smad3 连接子磷酸化会降低 Smad 复合物的形成和转录活性。在许多类型的癌细胞中，Smad3 连接位点被组成型磷酸化。我们目前正在研究 Smad3 连接体磷酸化的变化是否有助于 TGF-β 从肿瘤抑制因子转变为转移促进因子。尽管 Smad 参与 TGF-β 的大部分作用，但激活的 TGF-β 受体也通过其他细胞内信号传导途径转导信号。在过去的几年里，我的团队投入了大量的精力来破译TGF-β受体独立于Smads激活MAP激酶的具体机制，并阐明这种不依赖于Smad的TGF-β信号传导的生物学意义。为了实现这些目标，我们发现 TRAF6 对于 JNK 和 p38 的 Smad 独立激活是特别需要的。目前，我们正在扩展这一发现，以揭示在 TGF-β 信号传导中发挥作用的其他机制和途径。我们采用靶向蛋白质组学方法来鉴定 TGF-β I 型受体复合物的其他相关蛋白。我们还采用全局磷酸化蛋白质组学方法，使用 SILAC 鉴定与 TGF-β 信号转导相关的差异磷酸化蛋白质。这两种方法相辅相成，这些努力的结果将产生 TGF-β 信号网络的定量磷酸化蛋白质组学特征。我们希望发现在 TGF-β 信号传导早期相互作用和/或磷酸化的新蛋白质。对候选蛋白的进一步表征应该能够阐明其他机制，这些机制可能解释不依赖于 Smad 的 TGF-β 信号传导反应，并加深我们对 TGF-β 诱导多种生物反应能力的理解。