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J. Cell Biol.,
Volume 143, Number 3, November 2, 1998 767-775
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.
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