Magnesium permeation through mechanosensitive channels: single-current measurementsстатья
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Дата последнего поиска статьи во внешних источниках: 4 апреля 2017 г.
Аннотация: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 ± 0.5 and 6.4 ± 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.