Large-Conductance Calcium-Activated Potassium Channels in Purkinje Cell Plasma Membranes Are Clustered at Sites of Hypolemmal Microdomains
Large-Conductance Calcium-Activated Potassium Channels in Purkinje Cell Plasma Membranes Are Clustered at Sites of Hypolemmal Microdomains
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DOI：
10.1002/cne.22066
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发表时间：
2009-07-10
影响因子：
2.5
通讯作者：
Ottersen, Ole Petter
中科院分区：
文献类型：
--
作者：
Kaufmann, Walter A.;Ferraguti, Francesco;Ottersen, Ole Petter
钙激活钾通道已被证明是至关重要的参与神经元功能，但其详细的作用有待于确定的微域，他们所在的阐明。本研究通过植入后免疫金细胞化学和SDS-消化冷冻断裂复制标记（SDS-FRL）方法，揭示了大电导钙激活钾通道（BK，KCa1.1，或Slo 1）在小脑浦肯野细胞体树突区室的精确亚细胞分布。我们发现BK通道是不均匀分布在浦肯野细胞质膜。在远端树突状室，BK通道分散在树突轴和棘的质膜上，但不存在突触后密度。在索马和近端树突，BK通道形成两个不同的池。一个池分散在质膜上，而另一个池聚集在质膜域覆盖地下cispellant。在SDS-FRL中建立的聚集通道与分散通道的标记密度比约为60：1。亚表面池，也称为膜下池，是内质网的亚区室，可能代表钙体，其独立地卸载和再填充Ca（2+）。浦肯野细胞亚表面脑池富含肌醇1，4，5-三磷酸受体，其通过将Ca（2+）释放到胞质溶胶中，产生局部Ca（2+）火花来介导几种神经递质、激素和生长因子的作用。胞浆[Ca（2+）]的这种增加可能足以激活BK通道。因此，质膜中的收缩的BK通道可能参与构建具有潜在钙体的功能单元（浆体），其对浦肯野细胞中的局部信号传导有显著贡献。神经学比较杂志515：215-230，2009. (C)2009 Wiley-Liss，Inc.
Calcium-activated potassium channels have been shown to be critically involved in neuronal function, but an elucidation of their detailed roles awaits identification of the microdomains where they are located. This study was undertaken to unravel the precise subcellular distribution of the large-conductance calcium-activated potassium channels (called BK, KCa1.1, or Slo1) in the somatodendritic compartment of cerebellar Purkinje cells by means of postembedding immunogold cytochemistry and SDS-digested freeze-fracture replica labeling (SDS-FRL). We found BK channels to be unevenly distributed over the Purkinje cell plasma membrane. At distal dendritic compartments, BK channels were scattered over the plasma membrane of dendritic shafts and spines but absent from postsynaptic densities. At the soma and proximal dendrites, BK channels formed two distinct pools. One pool was scattered over the plasma membrane, whereas the other pool was clustered in plasma membrane domains overlying subsurface cisterns. The labeling density ratio of clustered to scattered channels was about 60:1, established in SDS-FRL. Subsurface cisterns, also called hypolemmal cisterns, are subcompartments of the endoplasmic reticulum likely representing calciosomes that unload and refill Ca(2+) independently. Purkinje cell subsurface cisterns are enriched in inositol 1,4,5-triphosphate receptors that mediate the effects of several neurotransmitters, hormones, and growth factors by releasing Ca(2+) into the cytosol, generating local Ca(2+) sparks. Such increases in cytosolic [Ca(2+)] may be sufficient for BK channel activation. Clustered BK channels in the plasma membrane may thus participate in building a functional unit (plasmerosome) with the underlying calciosome that contributes significantly to local signaling in Purkinje cells. J. Comp. Neurol. 515:215-230, 2009. (C) 2009 Wiley-Liss, Inc.