Molecular determinants of Mg2+ and Ca2+ permeability and pH sensitivity in TRPM6 and TRPM7
Molecular determinants of Mg2+ and Ca2+ permeability and pH sensitivity in TRPM6 and TRPM7
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DOI：
10.1074/jbc.m608972200
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发表时间：
2007-08-31
影响因子：
4.8
通讯作者：
Yue, Lixia
中科院分区：
文献类型：
--
作者：
Li, Mingjiang;Du, Jianyang;Yue, Lixia
通道激酶TRPM6和TRPM7最近被发现在Mg2+和Ca2+稳态中起重要作用，这对人类健康和细胞活力都至关重要。然而，这些通道独特的Mg2+和Ca2+渗透性和pH敏感性的分子基础仍然未知。在这里，我们在TRPM7的假设孔中创建了一系列氨基酸取代，以评估通道通透性的起源及其受ph的调节。TRPM7的两个突变体E1047Q和E1052Q在通道性质上产生了巨大的变化。E1052Q和E1047Q的I-V关系与WT TRPM7有显著差异，向内电流分别比TRPM7大8倍和12倍。在E1052Q和E1047Q中，Ca2+和Mg2+的结合亲和力分别降低了50 ~ 140倍。E1052Q的Ca2+和Mg2+电流比TRPM7小70%。引人注目的是，E1047Q在很大程度上消除了Ca2+和Mg2+的渗透，使TRPM7成为一个单价选择通道。此外，质子增强内向电流的能力在E1047Q中丢失，这表明E1047对TRPM7的Ca2+和Mg2+通透性及其pH敏感性至关重要。TRPM6孔隙中相应残基E1024Q和E1029Q的突变对TRPM6的通道性质产生了几乎相同的变化。我们的研究结果表明，这两种谷氨酸是两种通道二价选择性和pH敏感性的关键决定因素。这些发现揭示了TRPM6和TRPM7生理/病理功能的分子机制，并将扩展我们对TRPM通道孔隙结构的理解。
The channel kinases TRPM6 and TRPM7 have recently been discovered to play important roles in Mg2+ and Ca2+ homeostasis, which is critical to both human health and cell viability. However, the molecular basis underlying these channels' unique Mg2+ and Ca2+ permeability and pH sensitivity remains unknown. Here we have created a series of amino acid substitutions in the putative pore of TRPM7 to evaluate the origin of the permeability of the channel and its regulation by pH. Two mutants of TRPM7, E1047Q and E1052Q, produced dramatic changes in channel properties. The I-V relations of E1052Q and E1047Q were significantly different from WT TRPM7, with the inward currents of 8- and 12-fold larger than TRPM7, respectively. The binding affinity of Ca2+ and Mg2+ was decreased by 50- to 140-fold in E1052Q and E1047Q, respectively. Ca2+ and Mg2+ currents in E1052Q were 70% smaller than those of TRPM7. Strikingly, E1047Q largely abolished Ca2+ and Mg2+ permeation, rendering TRPM7 a monovalent selective channel. In addition, the ability of protons to potentiate inward currents was lost in E1047Q, indicating that E1047 is critical to Ca2+ and Mg2+ permeability of TRPM7, and its pH sensitivity. Mutation of the corresponding residues in the pore of TRPM6, E1024Q and E1029Q, produced nearly identical changes to the channel properties of TRPM6. Our results indicate that these two glutamates are key determinants of both channels' divalent selectivity and pH sensitivity. These findings reveal the molecular mechanisms underpinning physiological/pathological functions of TRPM6 and TRPM7, and will extend our understanding of the pore structures of TRPM channels.