肌动蛋白对结肠平滑肌大电导钙激活钾通道机械敏感性的影响

Effects of actin on mechanosensitivity of large conductance calcium-activated potassium channels in colonic smooth muscle cells

目的探讨大电导钙激活钾通道(large conductance calcium-activated potassium channels,BK)机械敏感性与肌动蛋白的关系。方法采用反转录聚合酶链反应(reverse transcription-polymerase chain reaction,RTPCR)技术检测BK各亚基信使核糖核酸(messenger ribonucleic acid,mRNA)水平;应用膜片钳技术记录小鼠结肠平滑肌细胞BK的单通道活动,确定其机械敏感性;应用细胞松弛素B(cytochalasin B,Cyto B)破坏肌动蛋白,探讨肌动蛋白对BK机械敏感性的影响。结果小鼠结肠平滑肌细胞BK由α和β1亚基构成;BK的开放概率随施加在膜片上的负压刺激的增加而强度依赖性增加;破坏细胞骨架不影响通道的机械敏感性。结论小鼠结肠平滑肌细胞BK对机械刺激敏感,且具有强度依赖性;BK机械敏感性不依赖于肌动蛋白的完整性,内衬于细胞膜下的皮质肌动蛋白可能分担膜张力,从而保护BK免受过度的牵张刺激。

Objective To study the relationship between the mechanosensitivity of large conductance calcium-activated potassium channels（BK）and actin.Methods The messenger ribonucleic acid（mRNA）of BK α-andβ-subunits were detected by reverse transcriptionpolymerase chain reaction（RT-PCR）technique.BK single channel activities in mice colonic smooth muscle cells were recorded with patch-clamp technique and the mechanosensitivity was characterized.Then,cytochalasin B was used to break down actin to determine effects of actin on mechanosensitivity of BK.Results The BK in mice colonic smooth muscle cells was composed ofα-and β1-subunits.The open probability of BK in colonic smooth muscle cells increased significantly and pressure-dependently under the stimulation of negative pressure.Breaking down actin did not affect BK mechanosensitivity.Conclusion BK in mice colonic smooth muscle cells was sensitive to mechanical stimuli and its activity was intensity-dependent.It was proven that mechanosensitivity of BK did not depend on the integrity of actin.The cortical actin,which lines parallel to bilayer,shares a proportion of membranous tension and protects BK from excess stretching.