Civan M M, Robbins J, Broad S, Rozengurt E, Brown D A
Growth Regulation Lab, Imperical Cancer Research Fund, London, UK.
J Membr Biol. 1993 Apr;133(1):51-9. doi: 10.1007/BF00231877.
Differentiated neuroblastoma cells exhibit both the delayed rectifier potassium current (IK) and the M-current (IM). The present study was designed to determine the roles of protein kinase C (PKC) and of the calmodulin-binding protein 80K/MARCKS, a prominent substrate for PKC and possible regulator of these currents. Neuroblastoma x glioma (NG108-15) hybrid cells transfected with m1 muscarinic receptors were grown with 1% fetal bovine serum (FBS) without the prostaglandin E1 (PGE1) and isobutylmethylxanthine (IBMX) usually added in preparation for electrophysiological studies. Under these conditions, the usual pleomorphism was largely abolished, leaving two populations of small cells with stellate and spherically symmetrical geometries. Whole-cell patch clamping indicated that the two cell types had identical electrophysiological properties, displaying: IK, a small current through a "T-like" Ca2+ channel, and no M-current. Stimulation with carbachol shifted the distribution of cells to a more stellate morphology within 24 hr and later (after 48 hr) reduced the PKC substrate 80K/MARCKS by 22 +/- 7%. In contrast to the stimulation of IK observed with cardiac cells, PKC activation produced only a small inhibition of IK, which was independent of carbachol pretreatment. Thus, PKC and 80K/MARCKS can be dissociated from the regulation of IK in neuroblastoma cells.
分化的神经母细胞瘤细胞同时表现出延迟整流钾电流（IK）和M电流（IM）。本研究旨在确定蛋白激酶C（PKC）以及钙调蛋白结合蛋白80K/MARCKS（PKC的主要底物和这些电流的可能调节因子）的作用。转染了m1毒蕈碱受体的神经母细胞瘤x胶质瘤（NG108 - 15）杂交细胞在不含通常用于电生理研究准备时添加的前列腺素E1（PGE1）和异丁基甲基黄嘌呤（IBMX）的1%胎牛血清（FBS）中培养。在这些条件下，通常的多形性在很大程度上被消除，只剩下具有星状和球形对称几何形状的两类小细胞群体。全细胞膜片钳记录表明，这两种细胞类型具有相同的电生理特性，表现为：IK、通过“T样”Ca2+通道的小电流，且无M电流。用卡巴胆碱刺激在24小时内使细胞分布转变为更具星状的形态，并且在之后（48小时后）使PKC底物80K/MARCKS减少了22±7%。与在心肌细胞中观察到的对IK的刺激相反，PKC激活仅对IK产生了小的抑制作用，这与卡巴胆碱预处理无关。因此，PKC和80K/MARCKS与神经母细胞瘤细胞中IK的调节可以分离。
