Jorgensen Nanna K, Pedersen Stine F, Rasmussen Hanne B, Grunnet Morten, Klaerke Dan A, Olesen Søren-Peter
Department of Medical Physiology, and the Copenhagen Heart Arrythmia Research Center, The Panum Institute, Denmark.
Biochim Biophys Acta. 2003 Sep 2;1615(1-2):115-25. doi: 10.1016/s0005-2736(03)00237-2.
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+), 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.
中间电导（hIK）或小电导（rSK3）的克隆钙激活钾通道在HEK 293细胞中表达，并使用全细胞膜片钳监测通道活性。当细胞暴露于细胞外渗透压降低33%时，已经被细胞内钙激活的hIK和rSK3电流分别进一步增加了95%和125%。细胞外渗透压增加50%时，hIK和rSK3电流分别被抑制了46%和32%。群体和单细胞测量表明，细胞肿胀和通道激活与可检测到的细胞内钙离子浓度升高无关。此外，IK和SK通道抑制剂显著降低了表达这些通道的细胞中的调节性容积减小（RVD）速率。细胞肿胀导致细胞内净F-肌动蛋白含量减少，细胞收缩则导致其增加。细胞松弛素D（CD）以引起F-肌动蛋白丝解聚的浓度强烈抑制了肿胀诱导的hIK通道激活，表明F-肌动蛋白细胞骨架在细胞体积变化对hIK的调节中起作用。总之，hIK和rSK3通道被细胞肿胀激活，被细胞收缩抑制。提示F-肌动蛋白细胞骨架在肿胀诱导的hIK通道激活中起作用。
