Influence of cloned voltage-gated K+ channel expression on alanine transport, Rb+ uptake, and cell volume.
Voltage-gated K+ channels are involved in regulation of action potential duration and in setting the resting membrane potential in nerve and muscle. To determine the effects of voltage-gated K+ channel expression on processes not associated with electrically excitable cells, we studied cell volume, membrane potential, Na(+)-K(+)-ATPase activity, and alanine transport after the stable expression of the Kv1.4 and Kv1.5 human K+ channels in Ltk- mouse fibroblasts (L-cells). The fast-activating noninactivating Kv1.5 channel, but not the rapidly inactivating Kv1.4 channel, prevented dexamethasone-induced increases in intracellular volume and inhibited Na(+)-K(+)-ATPase activity by 25%, as measured by 86Rb+ uptake. Alanine transport, measured separately by systems A and ASC, was lower in Kv1.5-expressing cells, indicating that the expression of this channel modified the Na(+)-dependent amino acid transport of both systems. Expression of the Kv1.4 channel did not alter alanine transport relative to wild-type or sham-transfected cells. The changes specific to Kv1.5 expression may be related to the resting membrane potential induced by this channel (-30 mV) in contrast to that measured in wild-type sham-transfected, or Kv1.4-transfected cells (-2 to 0 mV). Blocking of the Kv1.5 channel by 60 microM quinidine negated the effects of Kv1.5 expression on intracellular volume, Na(+)-K(+)-ATPase, and Na(+)-dependent alanine transport. These results indicate that delayed rectifier channels such as Kv1.5 can play a key role in the control of cell membrane potential, cell volume, Na(+)-K(+)-ATPase activity, and electrogenic alanine transport across the plasma membrane of electrically unexcitable cells.
Felipe
A
A
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232.
Snyders
D J
DJ
Deal
K K
KK
Tamkun
M M
MM
D000409:Alanine / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D005347:Fibroblasts / Q000502:physiology; D007700:Kinetics; D007739:L Cells; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D015221:Potassium Channels / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D012413:Rubidium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000378:metabolism
D018076:DNA, Complementary; D015221:Potassium Channels; D011994:Recombinant Proteins; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D000409:Alanine