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TRPM7 silencing attenuates Mg2+ influx in cardiac myoblasts, H9c2 cells
Michiko Tashiro1, Masato Konishi2, Ryo Kobayashi3
1Department of Physiology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo, 160-8402, Japan. tashiro@tokyo-med.ac.jp.
Abstract:
TRPM7, a member of the melastatin subfamily of transient receptor potential channels, is suggested to be a potential candidate for a physiological Mg2+ channel. However, there is no direct evidence of Mg2+ permeation through endogenous TRPM7. To determine the physiological roles of TRPM7 in intracellular Mg2+ homeostasis, we measured the cytoplasmic free Mg2+ concentration ([Mg2+]i) in TRPM7-silenced H9c2 cells. [Mg2+]i was measured in a cluster of 8-10 cells using the fluorescent indicator, furaptra. TRPM7 silencing did not change [Mg2+]i in Ca2+-free Tyrode's solution containing 1 mM Mg2+. Increasing the extracellular Mg2+ to 92.5 mM raised [Mg2+]i in control cells (1.56 ± 0.19 mM) at 30 min, while this effect was significantly attenuated in TRPM7-silenced cells (1.12 ± 0.07 mM). The Mg2+ efflux driven by Na+ gradient was unaffected by TRPM7 silencing. These results suggest that TRPM7 regulates the rate of Mg2+ influx in H9c2 cells, although cytoplasmic Mg2+ homeostasis at basal conditions is unaffected by TRPM7 silencing.
Insights
Transient Receptor Potential Melastatin 7 (TRPM7) channels regulate magnesium (Mg2+) influx. Silencing TRPM7 reduced Mg2+ uptake but did not affect basal intracellular Mg2+ levels.
Area of Science:
- Cell Biology
- Ion Channels
- Physiology
Background:
- Transient Receptor Potential Melastatin 7 (TRPM7) is a channel protein implicated in magnesium (Mg2+) transport.
- Direct evidence for Mg2+ permeation through endogenous TRPM7 is lacking.
- Understanding TRPM7's role in Mg2+ homeostasis is crucial.
Purpose of the Study:
- To investigate the physiological role of TRPM7 in regulating intracellular Mg2+ concentration ([Mg2+]i).
- To determine if TRPM7 directly influences Mg2+ homeostasis in H9c2 cells.
Main Methods:
- TRPM7 was silenced in H9c2 cells using gene silencing techniques.
- [Mg2+]i was measured using the fluorescent indicator furaptra in a cluster of 8-10 cells.
- Cells were exposed to varying extracellular Mg2+ concentrations and Na+ gradients.
Main Results:
- TRPM7 silencing did not alter basal [Mg2+]i in standard conditions.
- Elevated extracellular Mg2+ increased [Mg2+]i in control cells, but this effect was significantly reduced in TRPM7-silenced cells.
- TRPM7 silencing did not affect Na+-driven Mg2+ efflux.
Conclusions:
- TRPM7 plays a significant role in regulating the rate of Mg2+ influx into H9c2 cells.
- While TRPM7 influences Mg2+ uptake, basal intracellular Mg2+ homeostasis is maintained independently of TRPM7 under the studied conditions.
