Reck and Gpr124 Are Essential Receptor Cofactors for Wnt7a/Wnt7b-Specific Signaling in Mammalian CNS Angiogenesis and Blood-Brain Barrier Regulation

• Published in: Neuron (Cambridge, Mass.) Vol. 95; no. 5; pp. 1056 - 1073.e5
• Main Authors: Cho, Chris, Smallwood, Philip M., Nathans, Jeremy
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.08.2017; Elsevier Limited
• Subjects: Angiogenesis; Animals; Blood-brain barrier; Blood-Brain Barrier - physiology; canonical Wnt signaling; Cell culture; Cell surface; Cells, Cultured; Central nervous system; CNS angiogenesis; Cofactors; Endothelial Cells - metabolism; Eye Proteins - metabolism; Eye Proteins - physiology; Frizzled protein; Frizzled Receptors - physiology; G protein-coupled receptors; GPI-Linked Proteins - genetics; GPI-Linked Proteins - physiology; Heparan sulfate; Immunoglobulins; Leucine; Ligands; Membrane proteins; Mice; Mice, Transgenic; mouse genetics; Mutation; Neovascularization, Physiologic - physiology; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - physiology; Peptide Fragments - metabolism; Protein Binding - physiology; Proteins; Proto-Oncogene Proteins - physiology; Receptors, G-Protein-Coupled - physiology; Site-directed mutagenesis; Stimulation; vascular endothelial cells; Wnt Proteins - physiology; Wnt reporter; Wnt Signaling Pathway; blood-brain barrier; Wnt reporter; mouse genetics; vascular endothelial cells; canonical Wnt signaling; CNS angiogenesis
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2017.07.031

Reck, a GPI-anchored membrane protein, and Gpr124, an orphan GPCR, have been implicated in Wnt7a/Wnt7b signaling in the CNS vasculature. We show here that vascular endothelial cell (EC)-specific reduction in Reck impairs CNS angiogenesis and that EC-specific postnatal loss of Reck, combined with loss of Norrin, impairs blood-brain barrier (BBB) maintenance. The most N-terminal domain of Reck binds to the leucine-rich repeat (LRR) and immunoglobulin (Ig) domains of Gpr124, and weakening this interaction by targeted mutagenesis reduces Reck/Gpr124 stimulation of Wnt7a signaling in cell culture and impairs CNS angiogenesis. Finally, a soluble Gpr124(LRR-Ig) probe binds to cells expressing Frizzled, Wnt7a or Wnt7b, and Reck, and a soluble Reck(CC1-5) probe binds to cells expressing Frizzled, Wnt7a or Wnt7b, and Gpr124. These experiments indicate that Reck and Gpr124 are part of the cell surface protein complex that transduces Wnt7a- and Wnt7b-specific signals in mammalian CNS ECs to promote angiogenesis and regulate the BBB. •Reck promotes mammalian CNS angiogenesis by activating the canonical Wnt pathway•Endothelial Reck regulates blood-brain barrier (BBB) development and maintenance•Reck and Gpr124 genetically and directly interact to stimulate Wnt7a/7b signaling•Reck and Gpr124 form a multi-protein complex with Wnt7a/7b and Frizzled Cho et al. uncover an essential role for Reck in mammalian CNS angiogenesis and BBB regulation by activating the canonical Wnt pathway. They demonstrate that Reck and Gpr124 are receptor co-factors that assemble into a larger complex with Wnt7a/7b and Frizzled.