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キーワード:
Animals
CHO Cells
Cell Cycle/*physiology
Cell Membrane Permeability
Cesium/metabolism
Cricetinae
Enzyme Activation
Ether-A-Go-Go Potassium Channels
Intracellular Fluid/physiology
Ions
Maturation-Promoting Factor/metabolism
Potassium Channels/*physiology
Sodium/metabolism
要旨:
Release from arrest in G2 phase of the cell cycle causes profound changes in rat ether-a-go-go (r-eag) K+ channels heterologously expressed in Xenopus oocytes. The most evident consequence of the onset of maturation is the appearance of rectification in the r-eag current. The trigger for these changes is located downstream of the activation of mitosis-promoting factor (MPF). We demonstrate here that the rectification is due to a voltage-dependent block by intracellular Na+ ions. Manipulation of the intracellular Na+ concentration indicates that the site of Na+ block is located approximately 45% into the electrical distance of the pore and is only present in oocytes undergoing maturation. Since the currents through excised patches from immature oocytes exhibited a fast rundown, we studied CHO-K1 cells permanently transfected with r-eag. These cells displayed currents with a variable degree of block by Na+ and variable permeability to Cs+. Partial synchronization of the cultures in G0/G1 or M phases of the cell cycle greatly reduced the variability. The combined data obtained from mammalian cells and oocytes strongly suggest that the permeability properties of r-eag K+ channels are modulated during cell cycle-related processes.
