Regulation of TGF-beta Signaling and Embryonic Development by GTPases

描述(申请人提供)：GTP酶通过作为分子开关来调节蛋白质伙伴的活动，从而控制关键的细胞过程，如信号转导、转录、有丝分裂、细胞形状和细胞运动。对Ras和RhoA等小分子GTP酶的功能了解较多，但存在多种大分子量GTP酶，但对其功能的研究较少。GTPBP1和GTPBP2是唯一的、大的GTP酶，与翻译延伸因子EF1-α有较远的亲缘关系。然而，它们的生化和生物学功能是完全未知的。我们取得了突破性进展，发现GTPBP1和GTPBP2与Smad蛋白相互作用，Smad蛋白是转化生长因子超家族的主要信号转导因子。在胚胎和培养细胞检测中，GTPBP2尤其通过BMP和转化生长因子的结节/激活素分支增强信号传递。GTPBP基因在非洲爪哇早期胚胎发育以及随后的体节、血液、心脏和神经系统器官发生过程中表达。在发育中的胚胎中，用反义寡核苷酸阻断内源性GTPBP 1或2会扰乱中胚层分化、体型和器官发生。在这项资助中，我们建议研究GTPBP 1和2如何调节转化生长因子信号和脊椎动物的早期发育。目标1将确定GTPBPs和Smads之间相互作用的特异性和分子基础。目的2利用分化和报告基因分析，研究GTPBPs如何影响BMP和结节/激活素信号传导。目的3从功能的获得和丧失来研究GTPBPs在非洲爪哇胚胎中的发育作用，并开始寻找GTPBPs与上游途径之间的联系。转化生长因子超家族控制细胞生长、细胞死亡、分化和发育，转化生长因子信号异常会导致癌症、高血压、纤维化和其他疾病和出生缺陷。同样，GTP酶的异常也会导致癌症、多种疾病和出生缺陷。因此，转化生长因子信号蛋白和GTP酶是广受欢迎的药物靶点。GTPBP1/2功能障碍是否影响疾病尚不清楚，但最近在胶质母细胞瘤中发现了GTPBP2的染色体易位，胶质母细胞瘤是一种几乎无法治愈的脑癌。我们的研究将提供有关GTPBPs的关键信息，这些信息最终可能转化为临床治疗由转化生长因子或GTPBP信号异常引起的疾病。

DESCRIPTION (provided by applicant): GTPases govern critical cellular processes such as signal transduction, transcription, mitosis, cell shape and cell movement by acting as molecular switches that regulate activity of protein partners. The functions of small GTPases such as Ras and RhoA are relatively well understood, but there exists a variety of large molecular weight GTPases whose functions are poorly characterized. GTPBP1 and GTPBP2 are unique, large GTPases, distantly related to translation elongation factor EF1-alpha. Their biochemical and biological functions, however, are completely unknown. We have made a breakthrough by discovering that GTPBP1 and GTPBP2 interact with Smad proteins, the principal signal transducers for the Transforming Growth Factor-¿, (TGF¿) superfamily. GTPBP2 in particular enhances signaling by the BMP and nodal/activin branches of TGF¿ signaling in embryo and cultured cell assays. The GTPBP genes are expressed during early Xenopus embryogenesis and during subsequent organogenesis of somites, blood, heart and nervous system. Blocking endogenous GTPBP 1 or 2 in developing embryos with antisense oligonucleotides disrupts mesoderm differentiation, body patterning and organogenesis. In this grant, we propose to investigate how GTPBP 1 and 2 regulate TGF¿ signaling and early vertebrate development. Aim 1 will define the specificity and molecular basis of interaction between GTPBPs and Smads. Aim 2 will investigate how GTPBPs influence BMP and nodal/activin signaling, using differentiation and reporter gene assays. Aim 3 will investigate the developmental roles of the GTPBPs in Xenopus embryos by gain and loss of function, and we will begin a search for links between GTPBPs and upstream pathways. The TGF¿ superfamily controls cell growth, cell death, differentiation and development, and abnormal TGF¿ signaling causes cancer, hypertension, fibroses and other diseases and birth defects. Likewise, abnormalities in GTPases cause cancer, a wide range of diseases, and birth defects. Thus, TGF¿ signaling proteins and GTPases are popular drug targets. Whether dysfunctional GTPBP1/2 affect disease is not known, but a chromosomal translocation of GTPBP2 has recently been identified in glioblastoma, a nearly incurable brain cancer. Our studies will provide crucial information about GTPBPs which may eventually translate into clinical treatments for diseases caused by abnormal TGF¿ or GTPBP signaling.