Studies of Wnt Receptor interaction with agonists and antagonists

描述（由申请人提供）：Wnt蛋白是一种分泌的信号分子，在胚胎发生和组织稳态中调节细胞功能的许多基本方面。失调的Wnt信号与许多人类疾病，如癌症、骨质疏松症和退行性疾病有关。Wnt信号传导机制的研究对于理解基础生物学和人类健康具有至关重要的意义。Wnt信号是由两种跨膜受体启动的，这两种跨膜受体构成了Wnt受体复合物。一个是卷曲（Fz）蛇形受体家族的成员，另一个是单一的跨膜受体，属于低密度脂蛋白受体相关蛋白（LRP）家族，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信号传导。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1是研究R-spondin蛋白，这是一个激活Wnt信号的新激动剂家族。R-spondin蛋白在脊椎动物胚胎发生中起作用，并在遗传性疾病中发生突变。R-spondin蛋白也被开发为癌症治疗剂。但R-spondin、Wnt和Fz-LRP5/6受体之间的关系仍有争议和未解决。提出了实验来解决这些问题，并确定额外的rspo结合因子/受体。目的2是研究一种新型跨膜蛋白M15抑制Wnt/2-catenin信号传导的机制和功能。我们在爪蟾胚胎中进行了功能性cDNA表达筛选，以寻找促进前体形成的基因。我们发现了一种新的跨膜蛋白，称为M15，其功能是一种有效的Wnt拮抗剂。M15在Spemann的组织者和体细胞发生过程中表现出特异性表达。我们拟通过实验研究M15抑制Wnt信号通路的分子机制，以及M15在头/前发育和体形成中的生物学功能。目的3是研究M15L的功能，并鉴定参与前后模式的其他新cdna。M15- like （M15L）是我们在非洲爪蟾和人类中发现的M15家族的另一个成员。它是一种Wnt拮抗剂，在爪蟾胚胎中具有诱导头的活性，但与M15相比，Wnt抑制特异性有显著差异。我们计划研究M15L的表达和功能，揭示M15和M15L在爪蟾发育过程中相似或不同的作用。此外，基于M15的成功分离，我们计划继续对参与前后模式的其他新基因进行更全面的功能性cDNA表达筛选。这些分子和胚胎学实验可能会促进我们对新型激动剂和拮抗剂在脊椎动物发育和人类疾病中对Wnt受体复合物调控的理解。公共卫生相关性：细胞生长和分化受细胞外信号分子及其在细胞表面的受体之间的相互作用调节。这种相互作用的缺陷常常导致人类癌症和疾病。这一提议旨在了解与许多疾病相关的关键信号分子家族及其受体之间相互作用的分子性质。

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.