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以环境依赖性方式引发广泛的细胞应答，所述细胞应答调节细胞增殖、分化和凋亡。这些信号反应中的许多是由Smad蛋白介导的。因此，控制Smad活性对于TGF-β及其相关因子的适当信号传导至关重要。我们发现，TGF-β诱导磷酸化在三个网站的连接区的Smad 3除了两个C-末端丝氨酸残基。这些连接位点也可以被MAPK和CDK磷酸化，以响应生长因子刺激或致癌Ras激活。此外，Smad 3也受到Smurf 2介导的单泛素化，通过阻断与Smad 4形成复合物来抑制其活性。我们发现Smad 3与Smurf 2相互作用并经历Smurf 2介导的泛素化需要连接子T179的磷酸化。因此，Smad 3接头磷酸化降低了Smad复合物的形成和转录活性。在许多类型的癌细胞中，Smad 3连接位点是组成性磷酸化的。我们目前正在研究Smad 3的连接磷酸化的变化是否有助于TGF-β从肿瘤抑制因子转换为转移促进因子。虽然Smads参与TGF-β的大多数作用，但活化的TGF-β受体也通过其他细胞内信号传导途径抑制信号。在过去的几年里，我的团队投入了大量的精力来破译TGF-β受体激活MAP激酶的特定机制，并阐明这种Smad非依赖性TGF-β信号传导的生物学意义。为了实现这些目标，我们发现TRAF 6对于JNK和p38的Smad非依赖性激活是特别需要的。目前，我们正在扩大这一发现，以发现在TGF-β信号传导中发挥作用的其他机制和途径。我们已经采取了有针对性的蛋白质组学方法，以确定其他相关的蛋白质的TGF-β I型受体复合物。我们还采用了一种全球磷酸化蛋白质组学方法，使用SILAC鉴定与TGF-β信号相关的差异磷酸化蛋白质。这两种方法相互补充，这些努力的结果将产生TGF-β信号网络的定量磷酸蛋白质组学图谱。我们希望发现在TGF-β信号传导的早期阶段相互作用和/或磷酸化的新蛋白质。候选蛋白质的进一步表征将导致阐明可能解释Smad非依赖性TGF-β信号传导反应的其他机制，并促进我们对TGF-β诱导过多不同生物反应的能力的理解。