The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23
Abstract Fibroblast growth factor 23 (FGF23) plays an important role in phosphate homeostasis, and increased FGF23 levels result in hypophosphatemia; however, the molecular mechanism underlying increased FGF23 expression has not been fully elucidated. In this study, we found that mice lacking the bo...
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Nature Publishing Group
2024-11-01
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| Series: | Experimental and Molecular Medicine |
| Online Access: | https://doi.org/10.1038/s12276-024-01341-9 |
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| author | Su Jeong Lee Ju Ang Kim Hye Jung Ihn Je-Yong Choi Tae-Yub Kwon Hong-In Shin Eui-Sic Cho Yong Chul Bae Rulang Jiang Jung-Eun Kim Eui Kyun Park |
| author_facet | Su Jeong Lee Ju Ang Kim Hye Jung Ihn Je-Yong Choi Tae-Yub Kwon Hong-In Shin Eui-Sic Cho Yong Chul Bae Rulang Jiang Jung-Eun Kim Eui Kyun Park |
| author_sort | Su Jeong Lee |
| collection | DOAJ |
| description | Abstract Fibroblast growth factor 23 (FGF23) plays an important role in phosphate homeostasis, and increased FGF23 levels result in hypophosphatemia; however, the molecular mechanism underlying increased FGF23 expression has not been fully elucidated. In this study, we found that mice lacking the bobby sox homolog (Bbx −/− ) presented increased FGF23 expression and low phosphate levels in the serum and skeletal abnormalities such as a low bone mineral density (BMD) and bone volume (BV), as well as short and weak bones associated with low bone formation. Osteocyte-specific deletion of Bbx using Dmp-1-Cre resulted in similar skeletal abnormalities, elevated serum FGF23 levels, and reduced serum phosphate levels. In Bbx −/− mice, the expression of sodium phosphate cotransporter 2a (Npt2a) and Npt2c in the kidney and Npt2b in the small intestine, which are negatively regulated by FGF23, was downregulated, leading to phosphate excretion/wasting and malabsorption. An in vitro Fgf23 promoter analysis revealed that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-induced transactivation of the Fgf23 promoter was significantly inhibited by BBX overexpression, whereas it was increased following Bbx knockdown. Interestingly, 1,25(OH)2D3 induced an interaction of the 1,25(OH)2D3 receptor (VDR) with BBX and downregulated BBX protein levels. Cycloheximide (CHX) only partially downregulated BBX protein levels, indicating that 1,25(OH)2D3 regulates BBX protein stability. Furthermore, the ubiquitination of BBX followed by proteasomal degradation was required for the increase in Fgf23 expression induced by 1,25(OH)2D3. Collectively, our data demonstrate that BBX negatively regulates Fgf23 expression, and consequently, the ubiquitin-dependent proteasomal degradation of BBX is required for FGF23 expression, thereby regulating phosphate homeostasis and bone development in mice. |
| format | Article |
| id | doaj-art-cb3bee88a7984ca0b1b707ff9d120d35 |
| institution | OA Journals |
| issn | 2092-6413 |
| language | English |
| publishDate | 2024-11-01 |
| publisher | Nature Publishing Group |
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| series | Experimental and Molecular Medicine |
| spelling | doaj-art-cb3bee88a7984ca0b1b707ff9d120d352025-08-20T02:20:38ZengNature Publishing GroupExperimental and Molecular Medicine2092-64132024-11-0156112436244810.1038/s12276-024-01341-9The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23Su Jeong Lee0Ju Ang Kim1Hye Jung Ihn2Je-Yong Choi3Tae-Yub Kwon4Hong-In Shin5Eui-Sic Cho6Yong Chul Bae7Rulang Jiang8Jung-Eun Kim9Eui Kyun Park10Department of Oral Pathology and Regenerative Medicine, School of Dentistry, Institute for Hard Tissue and Bio‑tooth Regeneration (IHBR), Kyungpook National UniversityDepartment of Oral Pathology and Regenerative Medicine, School of Dentistry, Institute for Hard Tissue and Bio‑tooth Regeneration (IHBR), Kyungpook National UniversityCell and Matrix Research Institute, Kyungpook National UniversityDepartment of Biochemistry and Cell Biology, School of Medicine, Kyungpook National UniversityDepartment of Dental Biomaterials, School of Dentistry, Kyungpook National UniversityDepartment of Oral Pathology and Regenerative Medicine, School of Dentistry, Institute for Hard Tissue and Bio‑tooth Regeneration (IHBR), Kyungpook National UniversityCluster for Craniofacial Development and Regeneration Research, Institute of Oral Biosciences, School of Dentistry, Jeonbuk National UniversityDepartment of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National UniversityDivision of Developmental Biology, Cincinnati Children’s Hospital Medical CenterCell and Matrix Research Institute, Kyungpook National UniversityDepartment of Oral Pathology and Regenerative Medicine, School of Dentistry, Institute for Hard Tissue and Bio‑tooth Regeneration (IHBR), Kyungpook National UniversityAbstract Fibroblast growth factor 23 (FGF23) plays an important role in phosphate homeostasis, and increased FGF23 levels result in hypophosphatemia; however, the molecular mechanism underlying increased FGF23 expression has not been fully elucidated. In this study, we found that mice lacking the bobby sox homolog (Bbx −/− ) presented increased FGF23 expression and low phosphate levels in the serum and skeletal abnormalities such as a low bone mineral density (BMD) and bone volume (BV), as well as short and weak bones associated with low bone formation. Osteocyte-specific deletion of Bbx using Dmp-1-Cre resulted in similar skeletal abnormalities, elevated serum FGF23 levels, and reduced serum phosphate levels. In Bbx −/− mice, the expression of sodium phosphate cotransporter 2a (Npt2a) and Npt2c in the kidney and Npt2b in the small intestine, which are negatively regulated by FGF23, was downregulated, leading to phosphate excretion/wasting and malabsorption. An in vitro Fgf23 promoter analysis revealed that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-induced transactivation of the Fgf23 promoter was significantly inhibited by BBX overexpression, whereas it was increased following Bbx knockdown. Interestingly, 1,25(OH)2D3 induced an interaction of the 1,25(OH)2D3 receptor (VDR) with BBX and downregulated BBX protein levels. Cycloheximide (CHX) only partially downregulated BBX protein levels, indicating that 1,25(OH)2D3 regulates BBX protein stability. Furthermore, the ubiquitination of BBX followed by proteasomal degradation was required for the increase in Fgf23 expression induced by 1,25(OH)2D3. Collectively, our data demonstrate that BBX negatively regulates Fgf23 expression, and consequently, the ubiquitin-dependent proteasomal degradation of BBX is required for FGF23 expression, thereby regulating phosphate homeostasis and bone development in mice.https://doi.org/10.1038/s12276-024-01341-9 |
| spellingShingle | Su Jeong Lee Ju Ang Kim Hye Jung Ihn Je-Yong Choi Tae-Yub Kwon Hong-In Shin Eui-Sic Cho Yong Chul Bae Rulang Jiang Jung-Eun Kim Eui Kyun Park The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23 Experimental and Molecular Medicine |
| title | The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23 |
| title_full | The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23 |
| title_fullStr | The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23 |
| title_full_unstemmed | The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23 |
| title_short | The transcription factor BBX regulates phosphate homeostasis through the modulation of FGF23 |
| title_sort | transcription factor bbx regulates phosphate homeostasis through the modulation of fgf23 |
| url | https://doi.org/10.1038/s12276-024-01341-9 |
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