Khodaee Naser, Ghasemi Maedeh, Saghiri Reza, Eliassi Afsaneh
Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Evin, Tehran 19857, Iran ; Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Evin, Tehran 19857, Iran.
Department of Biochemistry, Pasteur Institute of Iran, Tehran, Iran.
EXCLI J. 2014 Sep 9;13:1075-87. eCollection 2014.
In a previous study we reported the presence of a large conductance K(+) channel in the membrane of endoplasmic reticulum (ER) from rat hepatocytes. The channel open probability (Po) appeared voltage dependent and reached to a minimum 0.2 at +50 mV. Channel activity in this case was found to be totally inhibited at ATP concentration 2.5 mM, glibenclamide 100 µM and tolbutamide 400 µM. Existing evidence indicates an impairment of endoplasmic reticulum functions in ER stress condition. Because ER potassium channels have been involved in several ER functions including cytoprotection, apoptosis and calcium homeostasis, a study was carried out to consider whether the ER potassium channel function is altered in a high fat diet model of ER stress. Male Wistar rats were made ER stress for 2 weeks with a high fat diet. Ion channel incorporation of ER stress model into the bilayer lipid membrane allowed the characterization of K(+) channel. Our results indicate that the channel Po was significantly increased at voltages above +30 mV. Interestingly, addition of ATP 7.5 mM, glibenclamide 400 µM and tolbutamide 2400 µM totally inhibited the channel activities, 3-fold, 4-fold and 6-fold higher than that in the control groups, respectively. Our results thus demonstrate a modification in the ER K(+) channel gating properties and decreased sensitivity to drugs in membrane preparations coming from ER high fat model of ER stress, an effect potentially linked to a change in ER K(+) channel subunits in ER stress condition. Our results may provide new insights into the cellular mechanisms underlying ER dysfunctions in ER stress.
在之前的一项研究中，我们报道了大鼠肝细胞内质网（ER）膜中存在一种大电导钾通道。该通道的开放概率（Po）呈现电压依赖性，在+50 mV时达到最小值0.2。在这种情况下，当ATP浓度为2.5 mM、格列本脲为100 µM和甲苯磺丁脲为400 µM时，通道活性被完全抑制。现有证据表明内质网应激条件下内质网功能受损。由于内质网钾通道参与了包括细胞保护、细胞凋亡和钙稳态在内的多种内质网功能，因此开展了一项研究，以探讨在高脂肪饮食诱导的内质网应激模型中内质网钾通道功能是否发生改变。雄性Wistar大鼠通过高脂肪饮食诱导内质网应激2周。将内质网应激模型的离子通道整合到双层脂质膜中，从而对钾通道进行特性描述。我们的结果表明，在电压高于+30 mV时，通道Po显著增加。有趣的是，添加7.5 mM ATP、400 µM格列本脲和24, uM甲苯磺丁脲可完全抑制通道活性，其抑制程度分别比对照组高3倍、4倍和6倍。因此，我们的结果证明了内质网高脂肪应激模型的膜制剂中内质网钾通道门控特性发生改变，且对药物的敏感性降低，这种效应可能与内质网应激条件下内质网钾通道亚基的变化有关。我们的结果可能为内质网应激时内质网功能障碍的细胞机制提供新的见解。
