Schubert T, Akopian A
Department of Neurobiology, University of Oldenburg, Oldenburg, Germany.
Neuroscience. 2004;125(3):583-90. doi: 10.1016/j.neuroscience.2004.02.009.
The regulation of voltage-activated K(+), and Ca(2+) currents by actin filaments was studied in salamander retinal ganglion cells, using the whole-cell patch clamp technique and Ca(2+) imaging. Disruption of F-actin by cytochalasin B or latrunculin B resulted in a reduction of L-type Ca(2+) current by 55+/-4%, and a sustained outward K(+) current (I(k)) by 41+/-3%. The effect was diminished when the F-actin stabilizing agent phalloidin was present in the patch pipette. In a group of cells where I(K) exhibited a small degree of inactivation, the effect of F-actin disruption on current was dual; it increased it by 89+/-16%, at -10 mV, and reduced it by 37+/-5% at +50 mV voltage step from the same holding potential of -70 mV. This was accompanied by a shift in a voltage of half-maximal activation toward negative potentials by approximately 20 mV. In Ca(2+) imaging experiments, 30 min incubation of isolated neurons with latrunculin A reduced a depolarization-induced Ca(2+) accumulation by 45+/-5%. These results suggest a role for the actin cytoskeleton in regulating voltage-gated ion channels in retinal ganglion cells.
利用全细胞膜片钳技术和钙离子成像技术，研究了蝾螈视网膜神经节细胞中肌动蛋白丝对电压激活的钾离子电流和钙离子电流的调节作用。用细胞松弛素B或拉特罗毒素B破坏F-肌动蛋白，导致L型钙离子电流降低55±4%，持续性外向钾离子电流（I(k)）降低41±3%。当膜片钳微管中存在F-肌动蛋白稳定剂鬼笔环肽时，这种效应减弱。在一组I(K)表现出较小程度失活的细胞中，F-肌动蛋白破坏对电流的影响是双重的；在-10 mV时，电流增加89±16%，在从相同的-70 mV保持电位到+50 mV电压阶跃时，电流降低37±5%。这伴随着半数最大激活电压向负电位偏移约20 mV。在钙离子成像实验中，用拉特罗毒素A孵育分离的神经元30分钟，可使去极化诱导的钙离子积累减少45±5%。这些结果表明肌动蛋白细胞骨架在调节视网膜神经节细胞中的电压门控离子通道方面发挥作用。
