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© The Rockefeller University Press, 0021-9525/1998//767 $5.00
The Journal of Cell Biology, Volume 143, Number 3, , 1998 767-775


Regular Articles

Cell Cycle–related Changes in the Conducting Properties of r-eag K+ Channels



Luis A. Pardo, Andrea Brüggemann, Javier Camacho, and Walter Stühmer

Max-Planck-Institut für experimentelle Medizin, D-37075 Göttingen, Germany

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 ~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.

Key Words: cell cycle • CHO cells • electrophysiology • potassium channels • Xenopus laevis



Abbreviations used in this paper: BAPTA, 1,2-bis(2-aminophenoxy)ethaneN,N,N'N'-tetraacetic acid; HO, Hoechst 33342; IC50, concentration required for 50% inhibition; I-V, current–voltage; MPF, mitosis-promoting factor; NFR, normal frog Ringer; r-eag, rat ether-à-go-go K+ channel.

Andrea Brüggemann's present address is Hoechst Marion Roussel, DG Cardiovascular, H 821, D-65926 Frankfurt, Germany. Tel.: 49-69-305-13547. Fax: 49-69-305-16393.

Address all correspondence to Luis A. Pardo, Max-Planck-Institut für experimentelle Medizin, Hermann-Rein-Str. 3, D-37075 Göttingen, Germany. Tel.: 49-551-3899-643. Fax: 49-551-389-9644. E-mail: pardo{at}mail.mpiem.gwdg.de



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