Xom Proteolysis During Early Vertebrate Embryogenesis

早期脊椎动物胚胎发生过程中的 Xom 蛋白水解

• 批准号: 7093110
• 负责人: ZHENGLUN ZHU
• 金额: $ 8.54万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7093110
• 关键词: DNA binding protein; Xenopus; Xenopus oocyte; active sites; biological signal transduction; bone morphogenetic proteins; early embryonic stage; embryogenic cleavage; enzyme activity; ligase; mass spectrometry; nonmammalian vertebrate embryology; phosphorylation; protein protein interaction; proteolysis; serine threonine protein kinase; transcription factor

DESCRIPTION (provided by applicant): Ubiquitin-mediated proteolysis plays important roles in governing signaling during early embryogenesis. Dysregulation of proteolysis of early developmental pathways often results in tumor formation in adult life. Exploring proteolysis during early embryogenesis, therefore, offers a unique opportunity to unveil mechanisms pertinent to tumorigenesis. During the investigation covered by my K08 award, we found that Xom, a homeobox transcriptional factor of the BMP4 signaling pathway, was degraded in a stage-specific manner at the onset of gastrulation. We have identified the destruction motif of Xom and the critical potential phosphorylation sites (Ser140 and Ser144) of the destruction motif that are important for Xom stability. We have further shown that the SCF-beta-TRCP is most likely the cellular E3 ubiquitin ligase involved in Xom degradation. Expression of non-degradable Xom disrupts dorsoventral pattern formation during early Xenopus embryogenesis, indicating the importance of regulated proteolysis during early embryogenesis. Two important questions remains: 1) how is Xom stabilized during pre-gastrulation phase and 2) what turns on Xom proteolysis at the onset of gastrulation. Based on our preliminary studies, we hypothesized that phosphorylation of the Xom destruction motif plays a regulatory role in determining Xom stability during early development, and a serine/threonine kinase phosphorylates Xom at the onset of gastrulation and triggers Xom degradation. We propose to address the following specific aims to test this hypothesis: 1) Define the function of (Ser140/144) phosphorylation in Xom degradation in vitro; 2) Determine a potential regulatory role of (Ser140/144) phosphorylation in Xom degradation in vivo; 3) Identify the kinase that phosphorylates Ser140/144 of Xom during early embryogenesis. Answers to these questions will present the evidence of how stability of homeobox function is regulated developmentally, which will bear great implications for understanding not only the basic mechanism of embryogenesis but also a broad spectrum of diseases, such as pathogenesis of neoplasm.

描述（由申请人提供）： 泛素介导的蛋白水解在早期胚胎发生过程中的信号传导控制中发挥着重要作用。早期发育途径的蛋白水解失调常常导致成年后肿瘤的形成。因此，探索早期胚胎发生过程中的蛋白水解作用为揭示与肿瘤发生相关的机制提供了独特的机会。在我的 K08 奖所涵盖的调查过程中，我们发现 Xom（BMP4 信号通路的同源框转录因子）在原肠胚形成开始时以特定阶段的方式降解。我们已经确定了 Xom 的破坏基序以及破坏基序的关键潜在磷酸化位点（Ser140 和 Ser144），这些位点对 Xom 稳定性很重要。我们进一步表明，SCF-β-TRCP 最有可能是参与 Xom 降解的细胞 E3 泛素连接酶。不可降解的 Xom 的表达破坏了爪蟾早期胚胎发生过程中背腹模式的形成，表明了早期胚胎发生过程中受调节的蛋白水解的重要性。仍然存在两个重要问题：1）Xom 在原肠胚形成前阶段如何稳定；2）在原肠胚形成开始时什么开启 Xom 蛋白水解。根据我们的初步研究，我们假设 Xom 破坏基序的磷酸化在确定早期发育过程中 Xom 稳定性方面发挥调节作用，丝氨酸/苏氨酸激酶在原肠胚形成开始时磷酸化 Xom 并触发 Xom 降解。我们建议解决以下具体目标来检验这一假设： 1) 定义(Ser140/144)磷酸化在Xom体外降解中的功能； 2) 确定(Ser140/144)磷酸化在Xom体内降解中的潜在调节作用； 3) 鉴定早期胚胎发生过程中磷酸化 Xom Ser140/144 的激酶。 这些问题的答案将提供同源框功能的稳定性如何在发育过程中受到调节的证据，这不仅对理解胚胎发生的基本机制，而且对理解广泛的疾病（例如肿瘤的发病机制）具有重要意义。