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Nguyen N, Carpenter KA, Ensing J, Gilliland C, Rudisel EJ, Mu EM, Thurlow KE, Triche TJ, Grainger S. EGFR-dependent endocytosis of Wnt9a and Fzd9b promotes β-catenin signaling during hematopoietic stem cell development in zebrafish. Sci Signal 2024; 17:eadf4299. [PMID: 38626007 DOI: 10.1126/scisignal.adf4299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 03/28/2024] [Indexed: 04/18/2024]
Abstract
Cell-to-cell communication through secreted Wnt ligands that bind to members of the Frizzled (Fzd) family of transmembrane receptors is critical for development and homeostasis. Wnt9a signals through Fzd9b, the co-receptor LRP5 or LRP6 (LRP5/6), and the epidermal growth factor receptor (EGFR) to promote early proliferation of zebrafish and human hematopoietic stem cells during development. Here, we developed fluorescently labeled, biologically active Wnt9a and Fzd9b fusion proteins to demonstrate that EGFR-dependent endocytosis of the ligand-receptor complex was required for signaling. In human cells, the Wnt9a-Fzd9b complex was rapidly endocytosed and trafficked through early and late endosomes, lysosomes, and the endoplasmic reticulum. Using small-molecule inhibitors and genetic and knockdown approaches, we found that Wnt9a-Fzd9b endocytosis required EGFR-mediated phosphorylation of the Fzd9b tail, caveolin, and the scaffolding protein EGFR protein substrate 15 (EPS15). LRP5/6 and the downstream signaling component AXIN were required for Wnt9a-Fzd9b signaling but not for endocytosis. Knockdown or loss of EPS15 impaired hematopoietic stem cell development in zebrafish. Other Wnt ligands do not require endocytosis for signaling activity, implying that specific modes of endocytosis and trafficking may represent a method by which Wnt-Fzd specificity is established.
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Affiliation(s)
- Nicole Nguyen
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Kelsey A Carpenter
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Jessica Ensing
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Carla Gilliland
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Emma J Rudisel
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Emily M Mu
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Kate E Thurlow
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
- Van Andel Institute Graduate School, Grand Rapids, MI 49503, USA
| | - Timothy J Triche
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49503, USA
| | - Stephanie Grainger
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA
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