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Molecular Mechanisms of Wnt Signal Transduction

Wnt信号转导的分子机制

基本信息

批准号：
9269721
负责人：
William I Weis
金额：
$ 7.98万
依托单位：
STANFORD UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2011
资助国家：
美国
起止时间：
2011-04-01 至 2020-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9269721
关键词：
Address Adenomatous Polyposis Coli Protein Adult Affect Affinity Agonist Binding Biochemical Biological Assay CSNK1A1 gene Cell Proliferation Cell membrane Cell surface Cells Complex Coupling Cytoplasmic Protein Cytoplasmic Tail Development Disease Embryonic Development Family member Foundations G-Protein-Coupled Receptors Gene Targeting Glycogen Synthase Kinase 3 Goals Growth Health Ligand Binding Ligands Lipids Malignant Neoplasms Measurement Measures Mediating Modeling Molecular Molecular Conformation Mutate Organism Outcome Pathway interactions Peptides Phosphorylation Phosphotransferases Process Proteins Recruitment Activity Retinal Role Scaffolding Protein Signal Pathway Signal Transduction Specific qualifier value Tail Testing Therapeutic Agents Tissues Transcription Coactivator Wnt proteins beta catenin biophysical techniques inhibitor/antagonist insight member multicatalytic endopeptidase complex prevent programs receptor research study seven-transmembrane G-protein-coupled receptor therapeutic development

项目摘要

DESCRIPTION (provided by applicant): Wnt growth factors are lipid-modified, secreted proteins that are essential for the development of multicellular organisms by specifying cell fate during embryogenesis and the renewal of tissues in the adult. In the "canonical" pathway, Wnts activate target genes that control cellular proliferation through the transcriptional co-activator�-catenin. Our goal is to define the molecular mechanisms that transduce the binding of a Wnt to its cell surface co-receptors Frizzled (Fzd) and LRP5/6 into stabilization of β-catenin. Rationale In the absence of Wnts, β-catenin is bound in a "destruction complex" that includes the scaffolding protein Axin and the kinases GSK-3 and CK1; phosphorylation of β-catenin by CK1 and GSK-3 leads to its ubiquitylation and destruction by the proteasome. Wnt binding to Fzd and LRP5/6 enables Fzd to recruit the cytoplasmic protein Dishevelled (Dvl), which in turn binds to Axin and thereby recruits the destruction complex to the activated receptor complex. This leads to phosphorylation of the LRP5/6 intracellular domain (ICD), which inhibits β-catenin destruction. Understanding this process is an important biomedical problem, as components of this pathway are mutated in a large number of cancers, which leads to inappropriately stabilized β-catenin and uncontrolled cellular proliferation. Strategy. We address two unsolved, fundamental mechanistic questions, using biochemical and biophysical assays with purified pathway components: 1) How do Wnts promote the Fzd-Dvl interaction? 2) How does phosphorylation of the LRP6 tail inhibit β-catenin destruction? Aim 1 examines the coupling of ligand and Dvl binding to Fzd, using Norrin, a Fzd4 ligand specific to a β-catenin-mediated signaling pathway. Quantitative affinity measurements will be used to test whether there is allosteric coupling between ligand and Dvl binding to Fzd (Aim 1a), whether LRP6 (Aim 1b) or Dvl phosphorylation (Aim 1c) promotes this coupling, and whether Dvl phosphorylation promotes its interactions with Axin (Aim 1c). Aim 2 tests proposed mechanisms of LRP6 ICD phosphorylation and how it inhibits β-catenin phosphorylation. Aim 2a defines the mechanism of LRP6 ICD phosphorylation by GSK-3 and CK1, and how phosphorylation affects the affinity of the LRP6 ICD for Axin. Aim 2b tests recently described models of Axin autoinhibition, in which intramolecular interactions inhibit binding of Axin to LRP6 and to β-catenin, and are relieved by GSK-3 phosphoryation. This sub-Aim also tests whether Axin and β-catenin compete for phosphorylated Axin. Aim 2c tests whether LRP6 inhibition of GSK-3 is kinetically sufficient to allow β-catenin to escape from the destruction complex. Outcomes. The mechanistic insights derived from these studies promise to inform development of therapeutics needed to control the pathway in cancers and other diseases.