title: In vivo analysis of formation and endocytosis of the Wnt/β-catenin signaling complex in zebrafish embryos.
abstract: After activation by Wnt/β-Catenin ligands, a multi-protein complex assembles at the plasma membrane as membrane-bound receptors and intracellular signal transducers are clustered into the so-called Lrp6-signalosome [Corrected]. However, the mechanism of signalosome formation and dissolution is yet not clear. Our imaging studies of live zebrafish embryos show that the signalosome is a highly dynamic structure. It is continuously assembled by Dvl2-mediated recruitment of the transducer complex to the activated receptors and partially disassembled by endocytosis. We find that, after internalization, the ligand-receptor complex and the transducer complex take separate routes. The Wnt-Fz-Lrp6 complex follows a Rab-positive endocytic path. However, when still bound to the transducer complex, Dvl2 forms intracellular aggregates. We show that this endocytic process is not only essential for ligand-receptor internalization but also for signaling. The μ2-subunit of the endocytic Clathrin adaptor Ap2 interacts with Dvl2 to maintain its stability during endocytosis. Blockage of Ap2μ2 function leads to Dvl2 degradation, inhibiton of signalosome formation at the plasma membrane and, consequently, reduction of signaling. We conclude that Ap2μ2-mediated endocytosis is important to maintain Wnt/β-catenin signaling in vertebrates.
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Anja I H
authors: AI
authors: Hagemann
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Jennifer
authors: J
authors: Kurz
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Silke
authors: S
authors: Kauffeld
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Qing
authors: Q
authors: Chen
authors: Departments of Cell Biology and Pediatrics, Harvard Medical School and Program in Cellular and Molecular Medicine at Boston Children's Hospital, Boston, 02115 MA, USA.
authors: Patrick M
authors: PM
authors: Reeves
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Sabrina
authors: S
authors: Weber
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Simone
authors: S
authors: Schindler
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany.
authors: Gary
authors: G
authors: Davidson
authors: Departments of Cell Biology and Pediatrics, Harvard Medical School and Program in Cellular and Molecular Medicine at Boston Children's Hospital, Boston, 02115 MA, USA.
authors: Tomas
authors: T
authors: Kirchhausen
authors: Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany steffen.scholpp@kit.edu.
authors: Steffen
authors: S
authors: Scholpp
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000235:genetics / Q000378:metabolism; D033983:Adaptor Protein Complex mu Subunits / Q000235:genetics / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000072261:Dishevelled Proteins; D004705:Endocytosis; D005260:Female; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D060449:Wnt Signaling Pathway; D014981:Xenopus / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D033962:Adaptor Protein Complex 2; D033983:Adaptor Protein Complex mu Subunits; D048868:Adaptor Proteins, Signal Transducing; D000072261:Dishevelled Proteins; C000588952:LRP6 protein, Xenopus; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D046912:Multiprotein Complexes; D010750:Phosphoproteins; C438886:adaptor protein complex 2, mu 2 subunit; D051176:beta Catenin
keywords: Development; Endocytosis; Signalosome; Wnt signaling; Zebrafish