TRPM7 silencing attenuates Mg2+ influx in cardiac myoblasts, H9c2 cells

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.

Keywords: Cardiac myoblast; H9c2; Mag-fura-2; Magnesium; TRPM7.