Cinacalcet Rectifies Hypercalcemia in a Patient With Familial Hypocalciuric Hypercalcemia Type 2 (FHH2) Caused by a Germline Loss‐of‐Function Gα11 Mutation
Cinacalcet Rectifies Hypercalcemia in a Patient With Familial Hypocalciuric Hypercalcemia Type 2 (FHH2) Caused by a Germline Loss‐of‐Function Gα11 Mutation
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西那卡塞可纠正由种系功能丧失 Gα11 突变引起的 2 型家族性低钙尿性高钙血症 (FHH2) 患者的高钙血症
DOI：
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发表时间：
2017
影响因子：
6.2
通讯作者：
R. Thakker
中科院分区：
文献类型：
--
作者：
C. Gorvin;F. Hannan;T. Cranston;H. Valta;O. Makitie;Camilla Schalin;R. Thakker
G蛋白亚基α-11(G-α11)将钙敏感受体与磷脂酶C(PLC)介导的细胞内钙(Ca~(2+))和丝裂原活化蛋白激酶(MAPK)信号偶联，分别在甲状旁腺和肾脏调节甲状旁腺激素的释放和尿钙的排泄。杂合性生殖系功能丧失Gα11突变导致家族性低钙尿性高钙血症2型(FHH2)，目前尚无有效的治疗方法。在这里，我们报告了一个新的杂合子Gα11胚系突变，Phe220Ser，它与一个FHH2家系的高钙血症相关。同源模拟表明，野生型(WT)Phe220非极性残基在Gα11高度保守的裂解区形成一簇疏水残基的一部分，与PLC结合并激活PLC；并预测突变的Ser220极性亲水残基替换Phe220将扰乱PLC介导的信号转导。将WT和突变型Gα11蛋白瞬时导入HEK293细胞的体外研究表明，突变型Ser220Gα11蛋白可抑制CaSR介导的钙离子i和细胞外信号调节蛋白1/2(ERKMAPK)信号转导，这与细胞外信号调节激酶1/2(ERKMAPK)活化减弱一致。此外，工程诱变研究表明，Gα11裂解区疏水性的丧失也损害了PLC的信号转导。与Ser220Gα11突变体相关的功能丧失可以通过Cinacalcet处理细胞来纠正，Cinacalcet是一种CaSR阳性变构调节剂。此外，体内给携带Phe220SerGα11突变的先证者应用Cinacalcet，使血清离子钙浓度正常化。因此，我们的研究报告了一个新的Gα11胚系突变(Phe220Ser)，揭示了Gα11疏水裂解区对于CaSR介导的PLC激活的重要性，并表明变构CaSR调节可以纠正功能丧失的Phe220Ser突变，改善与FHH2相关的高钙血症。©2017作者。《骨与矿物研究杂志》，由威利期刊公司出版。
G‐protein subunit α‐11 (Gα11) couples the calcium‐sensing receptor (CaSR) to phospholipase C (PLC)‐mediated intracellular calcium (Ca2+i) and mitogen‐activated protein kinase (MAPK) signaling, which in the parathyroid glands and kidneys regulates parathyroid hormone release and urinary calcium excretion, respectively. Heterozygous germline loss‐of‐function Gα11 mutations cause familial hypocalciuric hypercalcemia type 2 (FHH2), for which effective therapies are currently not available. Here, we report a novel heterozygous Gα11 germline mutation, Phe220Ser, which was associated with hypercalcemia in a family with FHH2. Homology modeling showed the wild‐type (WT) Phe220 nonpolar residue to form part of a cluster of hydrophobic residues within a highly conserved cleft region of Gα11, which binds to and activates PLC; and predicted that substitution of Phe220 with the mutant Ser220 polar hydrophilic residue would disrupt PLC‐mediated signaling. In vitro studies involving transient transfection of WT and mutant Gα11 proteins into HEK293 cells, which express the CaSR, showed the mutant Ser220 Gα11 protein to impair CaSR‐mediated Ca2+i and extracellular signal‐regulated kinase 1/2 (ERK) MAPK signaling, consistent with diminished activation of PLC. Furthermore, engineered mutagenesis studies demonstrated that loss of hydrophobicity within the Gα11 cleft region also impaired signaling by PLC. The loss‐of‐function associated with the Ser220 Gα11 mutant was rectified by treatment of cells with cinacalcet, which is a CaSR‐positive allosteric modulator. Furthermore, in vivo administration of cinacalcet to the proband harboring the Phe220Ser Gα11 mutation, normalized serum ionized calcium concentrations. Thus, our studies, which report a novel Gα11 germline mutation (Phe220Ser) in a family with FHH2, reveal the importance of the Gα11 hydrophobic cleft region for CaSR‐mediated activation of PLC, and show that allosteric CaSR modulation can rectify the loss‐of‐function Phe220Ser mutation and ameliorate the hypercalcemia associated with FHH2. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.
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