A novel mutation in helix 12 of the vitamin D receptor impairs coactivator interaction and causes hereditary 1,25-dihydroxyvitamin D-resistant rickets without alopecia
A novel mutation in helix 12 of the vitamin D receptor impairs coactivator interaction and causes hereditary 1,25-dihydroxyvitamin D-resistant rickets without alopecia
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DOI：
10.1210/me.2002-0152
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发表时间：
2002-11-01
影响因子：
--
通讯作者：
Feldman, D
中科院分区：
文献类型：
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作者：
Malloy, PJ;Xu, R;Feldman, D
遗传性维生素D抵抗性佝偻病（HVDRR）是一种遗传性疾病，最常见的是由维生素D受体（VDR）突变引起的。本研究中的患者表现出典型的HVDRR临床特征，包括早发性佝偻病、低钙血症、继发性甲状旁腺功能亢进以及血清碱性磷酸酶和1，25-二羟维生素D [1，25-（OH）（2）D-3]浓度升高。患者无脱发。VDR检测显示患者成纤维细胞提取物中[H-3] 1，25-（OH）（2）D-3的正常高亲和力低容量结合位点。然而，当用高剂量的1，25（OH）（2）D-3或维生素D类似物处理时，患者培养的成纤维细胞未能诱导24-羟化酶基因，这表明细胞对1，25-二羟维生素D的作用具有抗性。在VDR的配体结合结构域中的螺旋H12中鉴定了一种新的点突变，其将氨基酸420处的高度保守的谷氨酸改变为赖氨酸（E420 K）。该患者的突变是纯合子。通过定点诱变重建的E420 K突变体受体表现出许多正常的特性，包括配体结合，与类维生素A X受体的异二聚化，以及与维生素D反应元件的结合。然而，突变的VDR不能引起1，25-（OH）（2）D-3依赖的反式激活。随后的研究表明，突变VDR在结合类固醇受体辅激活因子1（SRC-1）和DRIP 205（维生素D受体相互作用蛋白（DRIP）辅激活因子复合物的亚基）方面有明显的损伤。总之，我们的数据表明，螺旋H12中的突变改变了共激活因子结合位点，阻止了共激活因子结合和反式激活。总之，我们已经确定了第一例天然存在的VDR突变（E420 K），该突变破坏了与VDR结合的辅激活因子并导致HVDRR。
Hereditary vitamin D-resistant rickets (HVDRR) is a genetic disorder most often caused by mutations in the vitamin D receptor (VDR). The patient in this study exhibited the typical clinical features of HVDRR with early onset rickets, hypocalcemia, secondary hyperparathyroidism, and elevated serum concentrations of alkaline phosphatase and 1,25-dihydroxyvitamin D [1,25-(OH)(2)D-3]. The patient did not have alopecia. Assays of the VDR showed a normal high affinity low capacity binding site for [H-3]1,25-(OH)(2)D-3 in extracts from the patient's fibroblasts. However, the cells were resistant to 1,25-dihydroxyvitamin D action as demonstrated by the failure of the patient's cultured fibroblasts to induce the 24-hydroxylase gene when treated with either high doses of 1,25(OH)(2)D-3 or vitamin D analogs. A novel point mutation was identified in helix H12 in the ligand-binding domain of the VDR that changed a highly conserved glutamic acid at amino acid 420 to lysine (E420K). The patient was homozygous for the mutation. The E420K mutant receptor recreated by site-directed mutagenesis exhibited many normal properties including ligand binding, heterodimerization with the retinoid X receptor, and binding to vitamin D response elements. However, the mutant VDR was unable to elicit 1,25-(OH)(2)D-3-dependent transactivation. Subsequent studies demonstrated that the mutant VDR had a marked impairment in binding steroid receptor coactivator 1 (SRC-1) and DRIP205, a subunit of the vitamin D receptor-interacting protein (DRIP) coactivator complex. Taken together, our data indicate that the mutation in helix H12 alters the coactivator binding site preventing coactivator binding and transactivation. In conclusion, we have identified the first case of a naturally occurring mutation in the VDR (E420K) that disrupts coactivator binding to the VDR and causes HVDRR.