Thurneysen Thomas, Nicoll Debora A, Philipson Kenneth D, Porzig Hartmut
Pharmakologisches Institut der Universität Bern, Friedbühlstrasse 49, CH 3010, Bern, Switzerland.
Brain Res Mol Brain Res. 2002 Nov 15;107(2):145-56. doi: 10.1016/s0169-328x(02)00461-8.
Na(+)/Ca(2+) exchange activity is known to be expressed throughout the brain in both glial and neuronal tissue. mRNA of all three major subtypes of the mammalian Na(+)/Ca(2+) exchanger protein (NCX1, NCX2, NCX3) has been detected in most brain areas, albeit at varying densities. [The term 'subtype' is used for exchangers that are products of different genes (NCX1, NCX2, NCX3); 'isoform' is used for splice variants of a single gene product]. However, for lack of subtype specific labels, the cellular expression pattern of this transport protein has remained largely unknown. We have now used three subtype-specific antibodies, two monoclonal and one polyclonal, to identify the cellular distribution of the exchanger subtypes in rat hippocampus cell cultures. Surprisingly, we found little overlap for the expression of this membrane protein in different cell types. NCX1 labeled mainly the membranes of neuronal cells and their associated dendritic network. It was found in nearly all neuronal cells of the population growing in culture. In cultures maintained for more than 3 weeks, NCX1 was increasingly detected in the membrane of glia cells. NCX2 immunoreactivity was predominantly localized in various types of glia cells. It was also detected in the membranes of a few neuronal cell bodies but never in the dendritic network. In addition to labeling membranes, the NCX2 antibody strongly cross-reacted with an unidentified glial fibrillar protein. NCX3 expression appeared very low in hippocampus cultures and was restricted to a small subpopulation of neuronal cells. It was never detected in glia cells. Our results provide novel information on the cell-specific expression of the three Na(+)/Ca(2+) exchanger subtypes (NCX1, NCX2 and NCX3) in mammalian brain. These data may reflect functional differences among the subtypes that are not obvious from studies in recombinant cell lines and hence, may help to understand the functional role of specific glia- or neuron-associated Ca(2+) transport systems.
已知钠/钙交换活性在整个大脑的神经胶质组织和神经元组织中均有表达。在大多数脑区均检测到了哺乳动物钠/钙交换蛋白（NCX1、NCX2、NCX3）的所有三种主要亚型的mRNA，尽管其密度各不相同。[术语“亚型”用于指不同基因（NCX1、NCX2、NCX3）的产物；“同工型”用于指单个基因产物的剪接变体]。然而，由于缺乏亚型特异性标记，这种转运蛋白的细胞表达模式在很大程度上仍不清楚。我们现在使用三种亚型特异性抗体，两种单克隆抗体和一种多克隆抗体，来鉴定大鼠海马细胞培养物中交换蛋白亚型的细胞分布。令人惊讶的是，我们发现这种膜蛋白在不同细胞类型中的表达几乎没有重叠。NCX1主要标记神经元细胞的膜及其相关的树突网络。在培养中生长的几乎所有神经元细胞中都能发现它。在培养超过3周的培养物中，在神经胶质细胞的膜中越来越多地检测到NCX1。NCX2免疫反应主要定位于各种类型的神经胶质细胞中。在少数神经元细胞体的膜中也检测到了它，但从未在树突网络中检测到。除了标记膜外，NCX2抗体还与一种未鉴定的神经胶质纤维蛋白发生强烈交叉反应。NCX3在海马培养物中的表达似乎非常低，并且仅限于一小部分神经元细胞。在神经胶质细胞中从未检测到它。我们的结果提供了关于三种钠/钙交换蛋白亚型（NCX1、NCX2和NCX3）在哺乳动物大脑中细胞特异性表达的新信息。这些数据可能反映了亚型之间的功能差异，而这些差异在重组细胞系研究中并不明显，因此可能有助于理解特定的神经胶质或神经元相关钙转运系统的功能作用。
