Hypomagnesemia with secondary hypocalcemia due to a missense mutation in the putative pore-forming region of TRPM6
Hypomagnesemia with secondary hypocalcemia due to a missense mutation in the putative pore-forming region of TRPM6
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DOI：
10.1074/jbc.m611117200
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发表时间：
2007-03-09
影响因子：
4.8
通讯作者：
Gudermann, Thomas
中科院分区：
文献类型：
--
作者：
Chubanov, Vladimir;Schlingmann, Karl P.;Gudermann, Thomas
低镁血症伴继发性低钙血症是由TRPM6基因突变引起的常染色体隐性遗传病。目前的实验证据表明，TRPM6可能通过异聚通道复合物的形成与TRPM7特异性结合起作用。在这里，我们报告了TRPM6中继发性低钙血症错义突变的新低镁血症的鉴定和功能特征。受影响的受试者表现出严重的低镁血症和低钙血症，这是由TRPM6基因的复合杂合突变引起的：1208(-1)G > A影响外显子11之前的受体剪接位点，3050C > G导致TRPM6推定成孔区域的氨基酸改变（P1017R）。为了评估P1017R突变对功能的影响，我们将TRPM6（P1017R）和野生型TRPM6与TRPM7在爪蟾卵母细胞和HEK 293细胞中共表达，并分别通过双电极电压钳和全细胞膜片钳测量电流。野生型TRPM6和TRPM7的共表达导致TRPM7样电流的振幅显著增加。相反，TRPM6（P1017R）抑制TRPM7通道活性。与这些观察结果一致，含有相应突变P1040R的TRPM7在与野生型TRPM7共表达时表现出显性负向效应。共聚焦显微镜和荧光共振能量转移记录表明，P1017R突变既不影响TRPM6与TRPM7的组装，也不影响异质通道复合物在细胞表面的共同运输。我们得出结论，TRPM6/7通道复合物的假设孔隙中的功能缺陷足以损害体内镁的稳态。
Hypomagnesemia with secondary hypocalcemia is an autosomal recessive disorder caused by mutations in the TRPM6 gene. Current experimental evidence suggests that TRPM6 may function in a specific association with TRPM7 by means of heterooligomeric channel complex formation. Here, we report the identification and functional characterization of a new hypomagnesemia with secondary hypocalcemia missense mutation in TRPM6. The affected subject presented with profound hypomagnesemia and hypocalcemia caused by compound heterozygous mutation in the TRPM6 gene: 1208(-1)G > A affecting the acceptor splice site preceding exon 11, and 3050C > G resulting in the amino acid change (P1017R) in the putative pore-forming region of TRPM6. To assess the functional consequences of the P1017R mutation, TRPM6(P1017R) and wild-type TRPM6 were co-expressed with TRPM7 in Xenopus oocytes and HEK 293 cells, and currents were assessed by two-electrode voltage clamp and whole cell patch clamp measurements, respectively. Co-expression of wild-type TRPM6 and TRPM7 resulted in a significant increase in the amplitude of TRPM7-like currents. In contrast, TRPM6(P1017R) suppressed TRPM7 channel activity. In line with these observations, TRPM7, containing the corresponding mutation P1040R, displayed a dominant-negative effect upon co-expression with wild-type TRPM7. Confocal microscopy and fluorescence resonance energy transfer recordings demonstrated that the P1017R mutation neither affects assembly of TRPM6 with TRPM7, nor co-trafficking of heteromultimeric channel complexes to the cell surface. We conclude that a functional defect in the putative pore of TRPM6/7 channel complexes is sufficient to impair body magnesium homeostasis.