The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling
Wnt/β-catenin signaling directs animal development and tissue renewal in a tightly controlled, cell- and tissue-specific manner. In the mammalian central nervous system, the atypical ligand Norrin controls angiogenesis and maintenance of the blood-brain barrier and blood-retina barrier through the W...
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eLife Sciences Publications Ltd
2025-01-01
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| Online Access: | https://elifesciences.org/articles/96743 |
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| author | Elise S Bruguera Jacob P Mahoney William I Weis |
| author_facet | Elise S Bruguera Jacob P Mahoney William I Weis |
| author_sort | Elise S Bruguera |
| collection | DOAJ |
| description | Wnt/β-catenin signaling directs animal development and tissue renewal in a tightly controlled, cell- and tissue-specific manner. In the mammalian central nervous system, the atypical ligand Norrin controls angiogenesis and maintenance of the blood-brain barrier and blood-retina barrier through the Wnt/β-catenin pathway. Like Wnt, Norrin activates signaling by binding and heterodimerizing the receptors Frizzled (Fzd) and low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6), leading to membrane recruitment of the intracellular transducer Dishevelled (Dvl) and ultimately stabilizing the transcriptional coactivator β-catenin. Unlike Wnt, the cystine knot ligand Norrin only signals through Fzd4 and additionally requires the co-receptor Tetraspanin12 (Tspan12); however, the mechanism underlying Tspan12-mediated signal enhancement is unclear. It has been proposed that Tspan12 integrates into the Norrin-Fzd4 complex to enhance Norrin-Fzd4 affinity or otherwise allosterically modulate Fzd4 signaling. Here, we measure direct, high-affinity binding between purified Norrin and Tspan12 in a lipid environment and use AlphaFold models to interrogate this interaction interface. We find that Tspan12 and Fzd4 can simultaneously bind Norrin and that a pre-formed Tspan12/Fzd4 heterodimer, as well as cells co-expressing Tspan12 and Fzd4, more efficiently capture low concentrations of Norrin than Fzd4 alone. We also show that Tspan12 competes with both heparan sulfate proteoglycans and LRP6 for Norrin binding and that Tspan12 does not impact Fzd4-Dvl affinity in the presence or absence of Norrin. Our findings suggest that Tspan12 does not allosterically enhance Fzd4 binding to Norrin or Dvl, but instead functions to directly capture Norrin upstream of signaling. |
| format | Article |
| id | doaj-art-abde58c59b6b4c65a9fb4a9cadf5eb2f |
| institution | DOAJ |
| issn | 2050-084X |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-abde58c59b6b4c65a9fb4a9cadf5eb2f2025-08-20T02:51:23ZengeLife Sciences Publications LtdeLife2050-084X2025-01-011310.7554/eLife.96743The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signalingElise S Bruguera0https://orcid.org/0000-0003-1983-3013Jacob P Mahoney1William I Weis2https://orcid.org/0000-0002-5583-6150Departments of Molecular & Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, United StatesDepartments of Molecular & Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, United StatesDepartments of Molecular & Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, United StatesWnt/β-catenin signaling directs animal development and tissue renewal in a tightly controlled, cell- and tissue-specific manner. In the mammalian central nervous system, the atypical ligand Norrin controls angiogenesis and maintenance of the blood-brain barrier and blood-retina barrier through the Wnt/β-catenin pathway. Like Wnt, Norrin activates signaling by binding and heterodimerizing the receptors Frizzled (Fzd) and low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6), leading to membrane recruitment of the intracellular transducer Dishevelled (Dvl) and ultimately stabilizing the transcriptional coactivator β-catenin. Unlike Wnt, the cystine knot ligand Norrin only signals through Fzd4 and additionally requires the co-receptor Tetraspanin12 (Tspan12); however, the mechanism underlying Tspan12-mediated signal enhancement is unclear. It has been proposed that Tspan12 integrates into the Norrin-Fzd4 complex to enhance Norrin-Fzd4 affinity or otherwise allosterically modulate Fzd4 signaling. Here, we measure direct, high-affinity binding between purified Norrin and Tspan12 in a lipid environment and use AlphaFold models to interrogate this interaction interface. We find that Tspan12 and Fzd4 can simultaneously bind Norrin and that a pre-formed Tspan12/Fzd4 heterodimer, as well as cells co-expressing Tspan12 and Fzd4, more efficiently capture low concentrations of Norrin than Fzd4 alone. We also show that Tspan12 competes with both heparan sulfate proteoglycans and LRP6 for Norrin binding and that Tspan12 does not impact Fzd4-Dvl affinity in the presence or absence of Norrin. Our findings suggest that Tspan12 does not allosterically enhance Fzd4 binding to Norrin or Dvl, but instead functions to directly capture Norrin upstream of signaling.https://elifesciences.org/articles/96743Wntcell signalingspecificityco-receptornanodiscs |
| spellingShingle | Elise S Bruguera Jacob P Mahoney William I Weis The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling eLife Wnt cell signaling specificity co-receptor nanodiscs |
| title | The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling |
| title_full | The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling |
| title_fullStr | The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling |
| title_full_unstemmed | The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling |
| title_short | The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling |
| title_sort | co receptor tetraspanin12 directly captures norrin to promote ligand specific β catenin signaling |
| topic | Wnt cell signaling specificity co-receptor nanodiscs |
| url | https://elifesciences.org/articles/96743 |
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