Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy
Abstract α-Klotho (KLA) is a type-1 membranous protein that can associate with fibroblast growth factor receptor (FGFR) to form co-receptor for FGF23. The ectodomain of unassociated KLA is shed as soluble KLA (sKLA) to exert FGFR/FGF23-independent pleiotropic functions. The previously determined X-r...
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2025-01-01
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| author | Nicholas J. Schnicker Zhen Xu Mohammad Amir Lokesh Gakhar Chou-Long Huang |
| author_facet | Nicholas J. Schnicker Zhen Xu Mohammad Amir Lokesh Gakhar Chou-Long Huang |
| author_sort | Nicholas J. Schnicker |
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| description | Abstract α-Klotho (KLA) is a type-1 membranous protein that can associate with fibroblast growth factor receptor (FGFR) to form co-receptor for FGF23. The ectodomain of unassociated KLA is shed as soluble KLA (sKLA) to exert FGFR/FGF23-independent pleiotropic functions. The previously determined X-ray crystal structure of the extracellular region of sKLA in complex with FGF23 and FGFR1c suggests that sKLA functions solely as an on-demand coreceptor for FGF23. To understand the FGFR/FGF23-independent pleiotropic functions of sKLA, we investigated biophysical properties and structure of apo-sKLA. Single particle cryogenic electron microscopy (cryo-EM) revealed a 3.3 Å resolution structure of apo-sKLA that overlays well with its counterpart in the ternary complex with several distinct features. Compared to the ternary complex, the KL2 domain of apo-sKLA is more flexible. Three-dimensional variability analysis revealed that apo-sKLA adopts conformations with different KL1-KL2 interdomain bending and rotational angles. Mass photometry revealed that sKLA can form a stable structure with FGFR and/or FGF23 as well as sKLA dimer in solution. Cryo-EM supported the dimeric structure of sKLA. Recent studies revealed that FGF23 contains two KLA-binding sites. Our computational studies revealed that each site binds separate KLA in the dimer. The potential multiple forms and shapes of sKLA support its role as FGFR-independent hormone with pleiotropic functions. The ability of FGF23 to engage two KLA’s simultaneously raises a potential new mechanism of action for FGF23-mediated signaling by the membranous klotho. |
| format | Article |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-8c943d44522447388cda8f8e1fa29b952025-01-05T12:21:32ZengNature PortfolioScientific Reports2045-23222025-01-0115111510.1038/s41598-024-84246-xConformational landscape of soluble α-klotho revealed by cryogenic electron microscopyNicholas J. Schnicker0Zhen Xu1Mohammad Amir2Lokesh Gakhar3Chou-Long Huang4Protein and Crystallography Facility, University of Iowa Carver College of MedicineProtein and Crystallography Facility, University of Iowa Carver College of MedicineDepartment of Internal Medicine, University of Iowa Carver College of MedicineProtein and Crystallography Facility, University of Iowa Carver College of MedicineDepartment of Internal Medicine, University of Iowa Carver College of MedicineAbstract α-Klotho (KLA) is a type-1 membranous protein that can associate with fibroblast growth factor receptor (FGFR) to form co-receptor for FGF23. The ectodomain of unassociated KLA is shed as soluble KLA (sKLA) to exert FGFR/FGF23-independent pleiotropic functions. The previously determined X-ray crystal structure of the extracellular region of sKLA in complex with FGF23 and FGFR1c suggests that sKLA functions solely as an on-demand coreceptor for FGF23. To understand the FGFR/FGF23-independent pleiotropic functions of sKLA, we investigated biophysical properties and structure of apo-sKLA. Single particle cryogenic electron microscopy (cryo-EM) revealed a 3.3 Å resolution structure of apo-sKLA that overlays well with its counterpart in the ternary complex with several distinct features. Compared to the ternary complex, the KL2 domain of apo-sKLA is more flexible. Three-dimensional variability analysis revealed that apo-sKLA adopts conformations with different KL1-KL2 interdomain bending and rotational angles. Mass photometry revealed that sKLA can form a stable structure with FGFR and/or FGF23 as well as sKLA dimer in solution. Cryo-EM supported the dimeric structure of sKLA. Recent studies revealed that FGF23 contains two KLA-binding sites. Our computational studies revealed that each site binds separate KLA in the dimer. The potential multiple forms and shapes of sKLA support its role as FGFR-independent hormone with pleiotropic functions. The ability of FGF23 to engage two KLA’s simultaneously raises a potential new mechanism of action for FGF23-mediated signaling by the membranous klotho.https://doi.org/10.1038/s41598-024-84246-xSoluble alpha-klotho (sKLA)Fibroblast growth factor (FGF)Cryogenic electron microscopy (cryo-EM)Ternary complexMonomerDimer |
| spellingShingle | Nicholas J. Schnicker Zhen Xu Mohammad Amir Lokesh Gakhar Chou-Long Huang Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy Scientific Reports Soluble alpha-klotho (sKLA) Fibroblast growth factor (FGF) Cryogenic electron microscopy (cryo-EM) Ternary complex Monomer Dimer |
| title | Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy |
| title_full | Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy |
| title_fullStr | Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy |
| title_full_unstemmed | Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy |
| title_short | Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy |
| title_sort | conformational landscape of soluble α klotho revealed by cryogenic electron microscopy |
| topic | Soluble alpha-klotho (sKLA) Fibroblast growth factor (FGF) Cryogenic electron microscopy (cryo-EM) Ternary complex Monomer Dimer |
| url | https://doi.org/10.1038/s41598-024-84246-x |
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