Tryptophan Missense Mutation in the Ligand-Binding Domain of the Vitamin D Receptor Causes Severe Resistance to 1,25-Dihydroxyvitamin D
作者:T. M. Nguyen、P. Adiceam、M. L. Kottler、H. Guillozo、M. Rizk-Rabin、F. Brouillard、P. Lagier、C. Palix、J. M. Garnier、M. Garabedian
DOI:10.1359/jbmr.2002.17.9.1728
日期:——
In this study, two related young children, brother and sister, exhibited severe vitamin D‐resistant rickets without alopecia. Sequence analysis of the total vitamin D receptor (VDR) cDNA from skin fibroblasts revealed a substitution of the unique tryptophan of the VDR by arginine at amino acid 286 (W286R). Cultured skin fibroblasts of the two patients expressed normal‐size VDR protein (immunocytochemistry and Western blotting) and normal length VDR mRNA (Northern blotting). But, these fibroblasts, as well as COS‐7 cells transfected with the W286R mutant, failed to bind 3H 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3]. The tryptophan substitution did not affect VDR trafficking toward the nucleus but abolished the 24‐hydroxylase gene response to 1,25(OH)2D3, even at 10−6 M concentrations. In conclusion, this case report of a new family with hereditary vitamin D‐ resistant rickets (HVDRR) emphasizes the crucial role of the VDR tryptophan for ligand binding and for transactivation of 1,25(OH)2D3 target genes. It clearly shows the clinical significance of this VDR amino acid for calcium homeostasis and bone mineralization. This observation suggests further that the presence of a stable VDR‐bound ligand may not be obligatory for normal hair follicle development.
在这项研究中,两个有亲缘关系的幼儿(兄妹)表现出严重的维生素 D 抗性佝偻病,但没有脱发。对来自皮肤成纤维细胞的总维生素 D 受体(VDR)cDNA 的序列分析表明,VDR 独特的色氨酸在 286 氨基酸处被精氨酸取代(W286R)。两名患者培养的皮肤成纤维细胞表达正常大小的 VDR 蛋白(免疫细胞化学和 Western 印迹)和正常长度的 VDR mRNA(Northern 印迹)。但是,这些成纤维细胞以及转染了 W286R 突变体的 COS-7 细胞无法结合 3H 1,25-二羟维生素 D3 [1,25(OH)2D3]。色氨酸置换并不影响 VDR 向细胞核的迁移,但却取消了 24- 羟化酶基因对 1,25(OH)2D3 的反应,即使在 10-6 M 浓度下也是如此。总之,这个新的遗传性维生素 D 抗性佝偻病(HVDRR)家族的病例报告强调了 VDR 色氨酸在配体结合和 1,25(OH)2D3 靶基因的转录激活中的关键作用。它清楚地表明了这种 VDR 氨基酸对钙平衡和骨矿化的临床意义。这一观察结果进一步表明,稳定的 VDR 结合配体的存在可能不是毛囊正常发育的必要条件。