The kinase activity of the channel-kinase protein TRPM7 regulates stability and localization of the TRPM7 channel in polarized epithelial cells
The kinase activity of the channel-kinase protein TRPM7 regulates stability and localization of the TRPM7 channel in polarized epithelial cells
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DOI：
10.1074/jbc.ra118.001925
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发表时间：
2018-07-20
影响因子：
4.8
通讯作者：
Runnels, Loren W.
中科院分区：
文献类型：
--
作者：
Cai, Na;Lou, Liping;Runnels, Loren W.
通道激酶瞬时受体电位melastatin 7（TRPM 7）是一种具有离子通道和激酶结构域的双功能蛋白。TRPM 7的激酶活性与广泛的细胞活性的调节有关，但很少了解通道本身如何通过其自身的激酶活性进行调节。在此，使用表达WT TRPM 7或激酶失活变体的几种哺乳动物细胞系，我们发现与表达WT TRPM 7的细胞相比，TRPM 7激酶活性失活的细胞具有更快的降解，提高的泛素化，以及增加的通道细胞内滞留。TRPM 7自磷酸化位点的突变分析进一步揭示了TRPM 7的Ser-1360作为介导TRPM 7稳定性和细胞内运输的关键残基的作用。发现了Ser-1403和Ser-1567的其他运输作用，其通过TRPM 7的激酶活性的磷酸化介导了通道与信号蛋白14-3-3的相互作用。总之，我们的研究结果表明TRPM 7的激酶活性在调节蛋白酶体介导的TRPM 7通道的周转和控制其在极化上皮细胞中的细胞定位中起关键作用。总的来说，这些发现提高了我们对TRPM 7激酶活性对其通道活性的功能调节的重要性的理解。
The channel-kinase transient receptor potential melastatin 7 (TRPM7) is a bifunctional protein with ion channel and kinase domains. The kinase activity of TRPM7 has been linked to the regulation of a broad range of cellular activities, but little is understood as to how the channel itself is regulated by its own kinase activity. Here, using several mammalian cell lines expressing WT TRPM7 or kinase-inactive variants, we discovered that compared with the cells expressing WT TRPM7, cells in which TRPM7's kinase activity was inactivated had faster degradation, elevated ubiquitination, and increased intracellular retention of the channel. Mutational analysis of TRPM7 autophosphorylation sites further revealed a role for Ser-1360 of TRPM7 as a key residue mediating both TRPM7 stability and intracellular trafficking. Additional trafficking roles were uncovered for Ser-1403 and Ser-1567, whose phosphorylation by TRPM7's kinase activity mediated the interaction of the channel with the signaling protein 14-3-3. In summary, our results point to a critical role for TRPM7's kinase activity in regulating proteasome-mediated turnover of the TRPM7 channel and controlling its cellular localization in polarized epithelial cells. Overall, these findings improve our understanding of the significance of TRPM7's kinase activity for functional regulation of its channel activity.