ARTICLES

Cell Research (2006)16: 723-730
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Magnesium permeation through mechanosensitive channels: single-current measurements

Alexander V Staruschenko, Anastasiya V Sudarikova, Yuri A Negulyaev, Elena A Morachevskaya

Correspondence: Yuri A Negulyaev Tel: +812+2971497; E-mail: yurineg@mail.cytspb.rssi.ru Received, 15 Jun 2005; revised, 6 May 2006; accepted, 5 Jun 2006; published online 25 Jul 2006

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Compelling evidence shows that intracellular free magnesium [Mg²⁺]i may be a critical regulator of cell activity in eukaryotes. However, membrane transport mechanisms mediating [Mg²⁺] influx in mammalian cells are poorly understood. Here, we show that mechanosensitive (MS) cationic channels activated by stretch are permeable for [Mg²⁺] ions at different extracellular concentrations including physiological ones. Single-channel currents were recorded from cell-attached and inside-out patches on K562 leukaemia cells at various concentrations of MgCl2 when [Mg²⁺] was the only available carrier of inward currents. At 2 mM [Mg²⁺], inward mechanogated currents representing [Mg²⁺] influx through MS channels corresponded to the unitary conductance of about 5 pS. At higher [Mg²⁺] levels, only slight increase of single-channel currents and conductance occurred, implying that [Mg²⁺] permeation through MS channels is characterized by strong saturation. At 20 and 90 mM [Mg²⁺], mean conductance values for inward currents carried by [Mg²⁺] were rather similar, being equal to 6.8 ¡À 0.5 and 6.4 ¡À 0.5 pS, respectively. The estimation of the channel-selective permeability according to constant field equation is obviously limited due to saturation effects. We conclude that the detection of single currents is the main evidence for [Mg²⁺] permeation through membrane channels activated by stretch. Our single-current measurements document [Mg²⁺] influx through MS channels in the plasma membrane of leukaemia cells.

Cell Research (2006) 16:723-730. doi:10.1038/sj.cr.7310084; published online 25 July 2006

Keywords: magnesium, single currents, mechanosensitive channel, human leukaemia cell