Molecular genetic and biochemical analyses of FGF23 mutations in familial tumoral calcinosis
Molecular genetic and biochemical analyses of FGF23 mutations in familial tumoral calcinosis
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DOI：
10.1152/ajpendo.90456.2008
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发表时间：
2008-10-01
影响因子：
5.1
通讯作者：
White, Kenneth E.
中科院分区：
文献类型：
--
作者：
Garringer, Holly J.;Malekpour, Mahdi;White, Kenneth E.
成纤维细胞生长因子23（FGF 23）是正常肾磷酸盐重吸收所需的激素。FGF 23功能获得性突变导致常染色体显性低磷血症性佝偻病（ADHR），FGF 23功能丧失性突变导致家族性高磷血症性肿瘤性钙质沉着症（TC）。在这项研究中，我们鉴定了一种新的隐性FGF 23 TC突变，在残基54（Q54 K）处赖氨酸（K）取代谷氨酰胺（Q）（160 C > A）。为了理解所有已知的FGF 23-TC突变体（H41 Q、S71 G、M96 T、S129 F和Q54 K）的分子结果，这些蛋白质在体外稳定表达。Western分析揭示了所有突变体的最少量的分泌的完整蛋白质，并且ELISA分析证明了高水平的分泌的COOH末端FGF 23片段，但低量的完整蛋白质，与TC患者的FGF 23血清谱一致。突变蛋白功能进行了测试，并显示残留，但降低，与野生型蛋白质的生物活性。在检查FGF 23 COOH-末端尾（残基180-251）在蛋白质加工和活性中的作用时，截短的突变体揭示了已知FGF 23 SPC蛋白酶位点（176 RXXR 179/S180）下游的大多数残基对于蛋白质分泌是不需要的。然而，RXXR位点附近的残基（残基188和202之间）是完全生物活性所必需的。总之，我们报告了一种新的TC突变，并证明了所有已知的FGF 23-TC突变体的共同缺陷，即FGF 23稳定性降低。最后，FGF 23的大部分COOH末端尾不是蛋白分泌所需的，而是完全生物活性所需的。
Fibroblast growth factor 23 (FGF23) is a hormone required for normal renal phosphate reabsorption. FGF23 gain-of-function mutations result in autosomal dominant hypophosphatemic rickets (ADHR), and FGF23 loss-of-function mutations cause familial hyperphosphatemic tumoral calcinosis (TC). In this study, we identified a novel recessive FGF23 TC mutation, a lysine (K) substitution for glutamine (Q) (160 C > A) at residue 54 (Q54K). To understand the molecular consequences of all known FGF23-TC mutants (H41Q, S71G, M96T, S129F, and Q54K), these proteins were stably expressed in vitro. Western analyses revealed minimal amounts of secreted intact protein for all mutants, and ELISA analyses demonstrated high levels of secreted COOH-terminal FGF23 fragments but low amounts of intact protein, consistent with TC patients' FGF23 serum profiles. Mutant protein function was tested and showed residual, yet decreased, bioactivity compared with wildtype protein. In examining the role of the FGF23 COOH-terminal tail (residues 180-251) in protein processing and activity, truncated mutants revealed that the majority of the residues downstream from the known FGF23 SPC protease site (176RXXR179/S180) were not required for protein secretion. However, residues adjacent to the RXXR site (between residues 188 and 202) were required for full bioactivity. In summary, we report a novel TC mutation and demonstrate a common defect of reduced FGF23 stability for all known FGF23-TC mutants. Finally, the majority of the COOH-terminal tail of FGF23 is not required for protein secretion but is required for full bioactivity.