TRPM7 channel is sensitive to osmotic gradients in human kidney cells
TRPM7 channel is sensitive to osmotic gradients in human kidney cells
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DOI：
10.1113/jphysiol.2007.130534
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发表时间：
2007-08-01
影响因子：
5.5
通讯作者：
Fleig, Andrea
中科院分区：
文献类型：
--
作者：
Bessac, Bret F.;Fleig, Andrea
TRPM7（瞬时受体电位melastatin 7）是一个具有a激酶功能的离子通道。TRPM7具有二价选择性，并受一系列受体刺激的第二信使通路、细胞内mg -核苷酸、二价和多价阳离子以及ph的调节。TRPM7在哺乳动物细胞中普遍存在，包括负责渗透调节的器官肾脏，这就提出了该通道是否具有渗透敏感性的问题。最近的报道调查了天然trpm7样电流对细胞肿胀的敏感性，结果相互矛盾。在这里，我们评估了TRPM7对低渗和高渗条件的敏感性，并探讨了该通道激酶结构域的参与。我们发现低渗性在细胞内镁和Mg-ATP升高（3-4 mM）时促进TRPM7，但在没有这些溶质的情况下没有影响。相反，高渗条件抑制TRPM7的IC50为430 mosmol（-1）。这种抑制作用在完全没有细胞内和细胞外二价离子的情况下保持，尽管在更高的渗透压下（IC50 = 510 mosmol(-1)）。TRPM7感知渗透梯度而不是离子强度，这与cAMP无关或不受细胞松弛素D处理的影响。此外，TRPM7激酶结构域缺失突变体在存在和不存在二价离子的情况下都表现出与野生型蛋白相似的渗透压行为。这表明至少部分渗透敏感性存在于通道域。在生理上，TRPM7通道似乎在调节体积变化中没有发挥积极作用，而是这些体积变化通过改变胞质中游离Mg、Mg核苷酸和另一个未知因素的浓度来调节TRPM7的活性。我们得出结论，TRPM7主要通过影响通道活性的溶质分子拥挤来感知渗透诱导的变化。
TRPM7 (transient-receptor-potential melastatin 7) is an ion channel with a-kinase function. TRPM7 is divalent-selective and regulated by a range of receptor-stimulated second messenger pathways, intracellular Mg-nucleotides, divalent and polyvalent cations and pH. TRPM7 is ubiquitously found in mammalian cells, including kidney, the responsible organ for osmolyte regulation, posing the question whether the channel is osmosensitive. Recent reports investigated the sensitivity of native TRPM7-like currents to cell swelling with contradictory results. Here, we assess the sensitivity of TRPM7 to both hypo- and hyperosmotic conditions and explored the involvement of the channel's kinase domain. We find that hypotonicity facilitates TRPM7 at elevated intracellular magnesium and Mg-ATP (3-4 mM), but has no effect in the absence of these solutes. Hypertonic conditions, in contrast, inhibit TRPM7 with an IC50 of 430 mosmol l(-1). This inhibitory effect is maintained in the complete absence of intra- and extracellular divalent ions, although shifted to higher osmolarities (IC50 = 510 mosmol l(-1)). TRPM7 senses osmotic gradients rather than ionic strength and this is independent of cAMP or not affected by cytochalasin D treatment. Furthermore, the kinase-domain deletion mutant of TRPM7 shows a similar behaviour to osmolarity as the wild-type protein, both in the presence and absence of divalent ions. This indicates that at least part of the osmosensitivity resides in the channel domain. Physiologically, TRPM7 channels do not seem to play an active role in regulatory volume changes, but rather those volume changes modulate TRPM7 activity through changes in the cytosolic concentrations of free Mg, Mg-nucleotides and a further unidentified factor. We conclude that TRPM7 senses osmotically induced changes primarily through molecular crowding of solutes that affect channel activity.