Natural and synthetic modulators of SK (K_ca2) potassium channels inhibit magnesium‐dependent activity of the kinase‐coupled cation channel TRPM7

Abstract

BACKGROUND AND PURPOSETransient receptor potential cation channel subfamily M member 7 (TRPM7) is a bifunctional protein comprising a TRP ion channel segment linked to an a-type protein kinase domain. TRPM7 is essential for proliferation and cell growth. Up-regulation of TRPM7 function is involved in anoxic neuronal death, cardiac fibrosis and tumour cell proliferation. The goal of this work was to identify non-toxic inhibitors of the TRPM7 channel and to assess the effect of blocking endogenous TRPM7 currents on the phenotype of living cells. EXPERIMENTAL APPROACHWe developed an aequorin bioluminescence-based assay of TRPM7 channel activity and performed a hypothesis-driven screen for inhibitors of the channel. The candidates identified were further assessed electrophysiologically and in cell biological experiments. KEY RESULTSTRPM7 currents were inhibited by modulators of small conductance Ca 2+ -activated K + channels (KCa2.1-2.3; SK) channels, including the antimalarial plant alkaloid quinine, CyPPA, dequalinium, NS8593, SKA31 and UCL 1684. The most potent compound NS8593 (IC50 1.6 mM) specifically targeted TRPM7 as compared with other TRP channels, interfered with Mg 2+ -dependent regulation of TRPM7 channel and inhibited the motility of cultured cells. NS8593 exhibited full and reversible block of native TRPM7-like currents in HEK 293 cells, freshly isolated smooth muscle cells, primary podocytes and ventricular myocytes. CONCLUSIONS AND IMPLICATIONSThis study reveals a tight overlap in the pharmacological profiles of TRPM7 and KCa2.1-2.3 channels. NS8593 acts as a negative gating modulator of TRPM7 and is well-suited to study functional features and cellular roles of endogenous TRPM7. Abbreviations

Expression and Contributions of TRPM7 and KCa2.3/SK3 Channels to the Increased Migration and Invasion of Microglia in Anti-Inflammatory Activation States

“…The previously reported TRPM7 block by NS8593 exhibited a mild dependence on intracellular Mg 2+ (IC 50  = 1.6 µM without Mg 2+ ; 5.9 µM at 300 µM Mg 2+ ) [18]. In addition, high intracellular Mg 2+ inhibits the TRPM7 current in microglia [19] and other cells [48], [49].…”

Active Caspase-1 Induces Plasma Membrane Pores That Precede Pyroptotic Lysis and Are Blocked by Lanthanides

“…In particular, mitochondrial ROS dependent-TRPM2 activation was shown to mediate liposome/particulate induced NLRP3 inflammasome activation (65). We observed that neither the broad TRP channel inhibitor ruthenium red nor the selective TRPM7 inhibitor NS8593 (66, 67) suppressed NG- or TcdB-induced pyroptotic propidium 2+ uptake (Fig 7F,G). In another recent study (68), we reported that Trpm2 −/− BMDC stimulated with NG did not exhibit reduced propidium 2+ influx compared to that in WT cells.…”

Flavanones That Selectively Inhibit TRPM3 Attenuate Thermal Nociception In Vivo

“…TRPM7 is permanently blocked by divalent cations, but when patched with Mg 21 -free pipette solution, switching to a bath solution lacking Ca 21 and Mg 21 ions gives rise to large inward and outward currents (Nadler et al, 2001). Because TRPM7-like currents exhibit a fast rundown when using a Na 1 -based bath solution, we used a Cs 1 -based bath solution, as described elsewhere (Chubanov et al, 2012). Neither isosakuranetin nor liquiritigenin (20 mM each) affected TRPM7-dependent inward or outward currents in HEK293 cells (Fig.…”