Block by extracellular Mg2+ of single human purinergic P2X4 receptor channels expressed in human embryonic kidney cells.
Single channel properties of human P2X4 receptors expressed in human embryonic kidney cells have been investigated by outside-out mode patch clamp recordings. P2X4 channel activity was characterized by very fast kinetics. The current-voltage relationship was strongly non-linear at potentials <-100 mV. A slope conductance of approximately 9 pS was estimated at the approximately linear part of the current-voltage relation (>-100 mV). External Mg2+ reversibly decreased the amplitude of ATP-evoked single channel currents in a concentration-dependent manner but independent of the membrane potential. Additionally, extracellular Mg2+ shortened the mean open time whereas the mean closed time was not affected. Thus, Mg2+ ions are proposed to inhibit the function of human P2X4 receptors by means of an open-channel block with a Mg2+ binding site at the exterior surface of the pore.
Negulyaev
Y A
YA
Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russian Federation.
Markwardt
F
F
D000255:Adenosine Triphosphate / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects / Q000502:physiology; D004622:Embryo, Mammalian; D006801:Humans; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology*; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology*; D018048:Receptors, Purinergic P2 / Q000187:drug effects* / Q000502:physiology*; D058848:Receptors, Purinergic P2X4
D007473:Ion Channels; C548226:P2RX4 protein, human; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; D000255:Adenosine Triphosphate; D008274:Magnesium