Cell cycle-related changes in the conducting properties of r-eag K+ channels.
Release from arrest in G2 phase of the cell cycle causes profound changes in rat ether-à-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.
Pardo
L A
LA
Max-Planck-Institut für experimentelle Medizin, D-37075 Göttingen, Germany. pardo@mail.mpiem.gwdg.de
Brüggemann
A
A
Camacho
J
J
Stühmer
W
W
D000818:Animals; D016466:CHO Cells; D002453:Cell Cycle / Q000502:physiology*; D002463:Cell Membrane Permeability; D002586:Cesium / Q000378:metabolism; D006224:Cricetinae; D004789:Enzyme Activation; D051638:Ether-A-Go-Go Potassium Channels; D007424:Intracellular Fluid / Q000502:physiology; D007477:Ions; D016200:Maturation-Promoting Factor / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology*; D012964:Sodium / Q000378:metabolism
D051638:Ether-A-Go-Go Potassium Channels; D007477:Ions; D015221:Potassium Channels; D002586:Cesium; D012964:Sodium; D016200:Maturation-Promoting Factor