Studies of Wnt Receptor interaction with agonists and antagonists

描述(申请人提供)：WNT蛋白是分泌的信号分子，在胚胎发育和组织内稳态中调节细胞功能的许多基本方面。去调控的Wnt信号与许多人类疾病有关，如癌症、骨质疏松症和退行性疾病。Wnt信号转导机制的研究对于了解基础生物学和人类健康具有重要意义。WNT信号是由两种类型的跨膜受体启动的，它们构成了WNT受体复合体。一个是蛇纹石受体FrizzledFZ家族的成员，另一个是属于低密度脂蛋白受体相关蛋白(LRP)家族的单一跨膜受体，LRP5或LRP6。除了Wnt蛋白，许多不同的细胞外配体似乎与FZ和/或LRP5/6受体结合，并在胚胎发育和病理条件下激活或抑制Wnt信号。这些Wnt激动剂/拮抗剂与FZ和LRP5/6受体之间的关系仍然知之甚少，这是本应用的重点。制定了三个相关的目标。目的研究R-Respondin蛋白，这是一类激活Wnt信号的新型激动剂。R-Respondin蛋白在脊椎动物胚胎发育中发挥作用，并在遗传性疾病中发生突变。R-Respondin蛋白也被开发为癌症治疗药物。但R-Respondin、Wnt和Fz-LRP5/6受体之间的关系一直存在争议和悬而未决。建议进行实验来解决这些问题，并确定更多的RSPO结合因子/受体。目的2研究一种新的跨膜蛋白M15抑制Wnt/2-catenin信号转导的机制和功能。我们已经在非洲爪哇胚胎中进行了促进前形成的基因的功能cDNA表达筛选。我们鉴定了一种新的跨膜蛋白，称为M15，它具有强大的Wnt拮抗剂的功能。M15在Spemann‘s组织器和体细胞发生过程中均有特异表达。我们建议通过实验来研究M15抑制Wnt信号的分子机制，以及在头/前发育和体节形成中的生物学功能。目的3是研究M15L的功能，并发现更多与前后方模式有关的新的cDNA。M15-Like(M15L)是我们在非洲爪哇和人类中发现的M15家族的另一个成员。它是一种Wnt拮抗剂，在非洲爪哇胚胎中具有头部诱导活性，但在Wnt抑制特异性方面与M15有显著差异。我们计划研究M15L的表达和功能，并揭示M15和M15L在非洲爪哇发育过程中相似和/或不同的作用。此外，在我们成功分离M15的基础上，我们计划继续对其他参与前后方模式的新基因进行更全面的功能cDNA表达筛选。这些分子和胚胎学实验可能会促进我们对Wnt受体复合体在脊椎动物发育和人类疾病中由新的激动剂和拮抗剂调节的理解。与公共健康相关：细胞生长和分化由细胞外信号分子及其细胞表面受体之间的相互作用调节。这种相互作用的缺陷经常会导致人类癌症和疾病。这项提议旨在了解一个关键的信号分子家族及其受体之间相互作用的分子本质，这些受体与许多疾病有关。

DESCRIPTION (provided by applicant): Wnt proteins are secreted signaling molecules that regulate many fundamental aspects of cellular functions in embryogenesis and tissue homeostasis. Deregulated Wnt signaling has been implicated in many human diseases such as cancer, osteoporosis and degenerative disorders. The study of the mechanisms of Wnt signaling has critical importance for understanding basic biology and human health. Wnt signaling is initiated by two types of transmembrane receptors that constitute the Wnt receptor complex. One is a member of the Frizzled (Fz) family of serpentine receptors, while the other is a single transmembrane receptor belonging to the LDL receptor related protein (LRP) family, LRP5 or LRP6. In addition to Wnt proteins, many distinct extracellular ligands appear to engage the Fz and/or LRP5/6 receptors and activate or inhibit Wnt signaling during embryonic development and under pathological conditions. The relationships between these Wnt agonists/antagonists with Fz and LRP5/6 receptors remain poorly understood, and are the focus of this application. Three related aims for formulated. Aim1 is to study R-spondin proteins, a novel family of agonists that activate Wnt signaling. R-spondin proteins have roles in vertebrate embryogenesis and are mutated in hereditary diseases. R-spondin proteins are also being developed as cancer therapeutic agents. But the relationships among R-spondin, Wnt and Fz-LRP5/6 receptors are debated and unresolved. Experiments are proposed to address these issues and to identify additional Rspo-binding factors/receptors. Aim 2 is to study the mechanism and function of a novel transmembrane protein, M15, that inhibits Wnt/2-catenin signaling. We have performed a functional cDNA expression screen in Xenopus embryos for genes that promote anterior formation. We identified a novel transmembrane protein, termed M15, that functions as a potent Wnt antagonist. M15 exhibits specific expression in the Spemann's organizer and also during somitogenesis. We propose experiments to study the molecular mechanism of M15 in inhibition of Wnt signaling and the biological function of in head/anterior development and somite formation. Aim 3 is to study M15L function and to identify additional novel cDNAs involved in anterior-posterior patterning. M15- like (M15L) is the other member of the M15 family we identified in Xenopus and human. It is a Wnt antagonist and has head-inducing activity in Xenopus embryos, but exhibits noticeable difference in Wnt inhibition specificity compared to M15. We plan to study the expression and function of M15L and uncover similar and/or distinct roles of M15 and M15L during Xenopus development. Additionally, based on our success with the isolation of M15, we plan to continue a more comprehensive functional cDNA expression screen for other novel genes that are involved in anterior-posterior patterning. These molecular and embryological experiments together will likely advance our understanding of the regulation of the Wnt receptor complex by novel agonists and antagonists in vertebrate development and human diseases. PUBLIC HEALTH RELEVANCE: Cell growth and differentiation are regulated by the interaction between extracellular signaling molecules and their receptors on the cell surface. Defects in this interaction often cause human cancers and diseases. This proposal aims to understand the molecular nature of the interaction between a key family of signaling molecules and their receptors that have been associated with many diseases.