Cell swelling activates cloned Ca(2+)-activated K(+) channels: a role for the F-actin cytoskeleton.
Cloned Ca(2+)-activated K(+) channels of intermediate (hIK) or small (rSK3) conductance were expressed in HEK 293 cells, and channel activity was monitored using whole-cell patch clamp. hIK and rSK3 currents already activated by intracellular calcium were further increased by 95% and 125%, respectively, upon exposure of the cells to a 33% decrease in extracellular osmolarity. hIK and rSK3 currents were inhibited by 46% and 32%, respectively, by a 50% increase in extracellular osmolarity. Cell swelling and channel activation were not associated with detectable increases in [Ca(2+)](i), evidenced by population and single-cell measurements. In addition, inhibitors of IK and SK channels significantly reduced the rate of regulatory volume decrease (RVD) in cells expressing these channels. Cell swelling induced a decrease, and cell shrinkage an increase, in net cellular F-actin content. The swelling-induced activation of hIK channels was strongly inhibited by cytochalasin D (CD), in concentrations that caused depolymerization of F-actin filaments, indicating a role for the F-actin cytoskeleton in modulation of hIK by changes in cell volume. In conclusion, hIK and rSK3 channels are activated by cell swelling and inhibited by shrinkage. A role for the F-actin cytoskeleton in the swelling-induced activation of hIK channels is suggested.
Jorgensen
Nanna K
NK
Department of Medical Physiology, and the Copenhagen Heart Arrythmia Research Center, The Panum Institute, Denmark. nkjorgensen@yahoo.com
Pedersen
Stine F
SF
Rasmussen
Hanne B
HB
Grunnet
Morten
M
Klaerke
Dan A
DA
Olesen
Søren-Peter
SP
D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D048429:Cell Size / Q000502:physiology; D003001:Cloning, Molecular; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D019384:Nucleic Acid Synthesis Inhibitors; D024681:Potassium Channels, Calcium-Activated; D015638:Cytochalasin D; D002118:Calcium