Mechanisms of TGF-B/Smad Signaling

描述（由申请人提供）：本提案的主要目的有两个方面：验证多功能细胞因子TGF-（）引发的多种生物反应是由T(RI(Alk5)- smad2 /3的典型途径和涉及Alk1- Smad1/5的其他途径联合介导的；并验证了在不同细胞环境下TGF-信号的特异性和强度也由Smad3的基础水平决定的假设，这是因为在TGF-信号缺失的情况下，由Axin-GSK3组成的调节装置介导Smad3的周转。如前期研究一节所示，我们已经产生了大量的前期数据来支持课题的生理意义和研究计划的可行性。因此，Aim 1将确定TGF-(通过非规范骨形态发生因子相关受体I/Smad1/5信号通路引发特异性生物学反应的功能和机制，如抑制B淋巴细胞增殖和刺激细胞迁移。这一假设的验证将挑战目前该领域的范式，即Smad1/5主要作为BMP信号通路的效应器发挥作用，很少介导TGF-（信号，如内皮细胞）。目的2将确定Axin-GSK3复合物转换基础水平Smad3的功能意义和机制。我们将研究GSK3激酶磷酸化Smad3上特定残基的生化和生物学性质。由于APC和CKI被定义为(-catenin破坏复合体的组成部分，我们还将研究这两种蛋白质是否参与Smad3的周转。虽然主要TGF-信号通路的模式已经建立，但在特定细胞环境下，非规范通路在介导多种生物反应中的作用还需要了解更多。实现这些特定目标将有助于更好地理解这一重要因子在细胞稳态、发育和疾病过程中的作用和机制。TGF-（）作为一种多功能细胞因子，参与许多生理病理过程的调控。更好地了解TGF-（）的作用机制可能有助于开发治疗许多人类疾病的新疗法，包括癌症和纤维化。

DESCRIPTION (provided by applicant): The primary objectives of this proposal are two folds: test the hypothesis that the diverse biological responses elicited by the multifunctional cytokine TGF-( are mediated by a combination of the canonical pathway of T(RI(Alk5)-Smad2/3 and other pathways such as those involving Alk1- Smad1/5; and test the hypothesis that the specificity and intensity of TGF-( signaling in different cellular context are also predetermined by the basal level of Smad3 due to the presence of a regulatory apparatus consisting of Axin-GSK3( that mediates the turnover of Smad3 in the absence of TGF-( signal. As shown in the section of Preliminary Studies, we have generated substantial amount of preliminary data to support the physiological significance of the topics and the feasibility of the research plan. Thus, Aim 1 will determine the function and mechanism by which TGF-( elicits specific biological responses, such as inhibition of B lymphocyte proliferation and stimulation of cell migration, via the non-canonical bone morphogenetic factor associated receptor I/Smad1/5 signaling pathway. Validation of this hypothesis would challenge the current paradigm in the field that Smad1/5 function primarily as effectors for the BMP signaling pathway and only very rarely mediate TGF-( signal as in endothelial cells. Aim 2 will determine the functional significance of and mechanism underlying the turnover of basal level of Smad3 by the Axin-GSK3( complex. We will study the biochemical and biological nature of phosphorylation of specific residues on Smad3 by the GSK3( kinase. Since APC and CKI have been defined as integral parts of the (-catenin destruction complex, we will also investigate whether these two proteins are involved in Smad3 turnover. While the paradigm for the primary TGF-( signaling pathway has been well established, much more needs to be learned on the contributions of non-canonical pathways to the mediation of diverse biological responses in specific cellular contexts. Accomplishment of these specific aims will lead to a better understanding on the actions and mechanisms of this important factor in cell homeostasis, development, and disease processes. As a multifunctional cytokine, TGF-( is involved in the regulation of many physiological and pathological processes. A better understanding of the mechanisms underlying the actions of TGF-( could help the development of novel therapeutics for many human diseases, including cancer and fibrosis.