Wonderlin W F, French R J
Department of Medical Physiology, University of Calgary, AB, Canada.
Proc Natl Acad Sci U S A. 1991 May 15;88(10):4391-5. doi: 10.1073/pnas.88.10.4391.
Ion channels that give rise to the excitable properties of the neuronal plasma membrane are synthesized, transported, and degraded in cytoplasmic organelles. To determine whether plasma membrane ion channels from these organelles could be physiologically activated, we extruded axoplasm from squid giant axons, dissociated organelles from the cytoskeletal matrix, and fused the free organelles with planar lipid bilayers. Three classes of ion channels normally associated with the plasma membrane were identified based on conductance, selectivity, and gating properties determined from steady-state single-channel recordings: (i) voltage-dependent Na channels, (ii) voltage-dependent delayed rectifier K channels, and (iii) large, voltage-independent K channels. The identity of the delayed rectifier channels was confirmed by reconstructing the time course of activation from single-channel responses to depolarizing voltage steps applied across the bilayer. These observations suggest that several classes of plasma membrane ion channels are transported in cytoplasmic organelles in physiologically active forms.
产生神经元质膜兴奋性特性的离子通道在细胞质细胞器中合成、运输和降解。为了确定来自这些细胞器的质膜离子通道是否能被生理激活，我们从鱿鱼巨大轴突中挤出轴浆，从细胞骨架基质中分离出细胞器，并将游离的细胞器与平面脂质双层融合。根据稳态单通道记录确定的电导、选择性和门控特性，鉴定出三类通常与质膜相关的离子通道：（i）电压依赖性钠通道，（ii）电压依赖性延迟整流钾通道，以及（iii）大的、电压非依赖性钾通道。通过从施加在双层上的去极化电压阶跃的单通道响应重建激活的时间进程，证实了延迟整流通道的身份。这些观察结果表明，几类质膜离子通道以生理活性形式在细胞质细胞器中运输。
