Smurf Ubiquitin Ligases in Xenopus Development

TGF β超家族调节细胞生长和分化。 在非洲爪蟾发育过程中，Nodal，Vg 1和激活素相关信号诱导内胚层和中胚层，BMP信号模式这些组织和调节外胚层细胞的命运。TGF β/激活素和BMP途径分别通过Smads 2和3或Smads 1、5和8来调节信号。 对TGF β信号下调知之甚少。 我们已经发现了两种E3泛素连接酶，Smurf 1和Smurf 2，它们分别抑制BMP和TGF β/激活素途径（Zhu et al.，1999年，Kavsak等人，2000年）。 蓝精灵靶向Smads和受体，用于泛素化和蛋白酶体降解。 虽然Smurf 1支持胚胎细胞的命运，但Smurf 2在胚胎中的作用尚不清楚。我们推测，蓝精灵调节组织诱导和图案形成在胚胎发生的区域特异性拮抗TGF β信号成分。 我们将研究Smurf 1和Smurf 2在胚胎发生过程中的作用，并研究Smurf调节发育所需的生化机制。 对Smurf功能的深入了解将产生有关TGF β信号传导和早期发育的重要信息，并将解决因TGF β信号或泛素连接酶功能调节缺陷而导致的出生缺陷、组织变性和癌症等病理学问题。目标1.蓝精灵在非洲爪蟾胚胎发育中起作用吗？我们将建立在胚胎发育过程中的空间分布的Smurf蛋白，并确定扰动Smurf蛋白水平或活性的发育影响。目标2.蓝精灵和TGF β信号是如何相互调节的？ 为了了解蓝精灵在胚胎中调节哪些信号通路，我们将使用生物学（表型）和生物化学（相互作用，泛素化）测定来测试蓝精灵对BMP和激活素信号通路组分的影响。 我们将确定蓝精灵在发育过程中是否受到TGF β或其他诱导信号的调节。目标3。新的Smurf相互作用蛋白的鉴定和功能。 为了全面了解Smurf底物并找到潜在的Smurf调节剂，我们将筛选并表征Smurf相互作用蛋白。 我们已经分离出89个与Smurf 1相互作用的克隆，包括Smad 1，一个已知的Smurf 1靶点。

The TGFbeta superfamily regulates cell growth and differentiation. During Xenopus development, Nodal, Vg1 and activin-related signals induce endoderm and mesoderm, and BMP signals pattern these tissues and regulate ectodermal cell fate. The TGFbeta/activin and BMP pathways respectively transduce signals via Smads 2 and 3, or Smads1, 5 and 8. Little is known about TGFbeta signal downregulation. We have discovered two E3 ubiquitin ligases, Smurf1 and Smurf2, that inhibit BMP and TGFbeta/activin pathways, respectively (Zhu et al., 1999, Kavsak et al., 2000). Smurfs target Smads and receptors for ubiquitination and proteasomal degradation. While Smurf1 dorsalizes embryonic cell fates, the action of Smurf2 in embryos is unknown. We hypothesize that the Smurfs regulate tissue induction and pattern formation in embryogenesis by region-specific antagonism of TGFbeta signaling components. We will examine the role of Smurf1 and Smurf2 during embryogenesis and investigate the biochemical mechanisms necessary for Smurf regulation of development. Insight into Smurf functions will yield vital information about TGFbeta signaling and early development and will address pathologies such as birth defects, tissue degeneration and cancer, that result from defective regulation of TGFbeta signals or ubiquitin ligase functioning. Aim 1. Do the Smurfs function in Xenopus embryonic development? We will establish the spatial distribution of Smurf proteins during embryogenesis, and determine the developmental effects of perturbing Smurf protein levels or activity. Aim 2. How do Smurfs and TGFbeta signals regulate each other? To understand which signaling pathways Smurfs regulate in embryos, we will test the effects of Smurfs on components of BMP and activin signaling pathways, using biological (phenotype) and biochemical (interaction, ubiquitination) assays. We will determine whether Smurfs are regulated by TGFbeta, or other inductive signals, during development. Aim 3. Identification and function of new Smurf interacting proteins. To obtain a comprehensive view of Smurf substrates and to find potential Smurf regulators, we will screen for and characterize Smurf-interacting proteins. We have already isolated 89 Smurf1-interacting clones, including Smad1, a known Smurf1 target.