Nagy J I, Li X, Rempel J, Stelmack G, Patel D, Staines W A, Yasumura T, Rash J E
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3J7.
J Comp Neurol. 2001 Dec 24;441(4):302-23. doi: 10.1002/cne.1414.
The connexin family of proteins (Cx) that form intercellular gap junctions in vertebrates is well represented in the mammalian central nervous system. Among these, Cx30 and Cx43 are present in gap junctions of astrocytes. Cx32 is expressed by oligodendrocytes and is present in heterologous gap junctions between oligodendrocytes and astrocytes as well as at autologous gap junctions between successive myelin layers. Cx36 mRNA has been identified in neurons, and Cx36 protein has been localized at ultrastructurally defined interneuronal gap junctions. Cx26 is also expressed in the CNS, primarily in the leptomeningeal linings, but is also reported in astrocytes and in neurons of developing brain and spinal cord. To establish further the regional, cellular, and subcellular localization of Cx26 in neural tissue, we investigated this connexin in adult mouse brain and in rat brain and spinal cord using biochemical and immunocytochemical methods. Northern blotting, western blotting, and immunofluorescence studies indicated widespread and heterogeneous Cx26 expression in numerous subcortical areas of both species. By confocal microscopy, Cx26 was colocalized with both Cx30 and Cx43 in leptomeninges as well as along blood vessels in cortical and subcortical structures. It was also localized at the surface of oligodendrocyte cell bodies, where it was coassociated with Cx32. Freeze-fracture replica immunogold labeling (FRIL) demonstrated Cx26 in most gap junctions between cells of the pia mater by postnatal day 4. By postnatal day 18 and thereafter, Cx26 was present at gap junctions between astrocytes and in the astrocyte side of most gap junctions between astrocytes and oligodendrocytes. In perinatal spinal cord and in five regions of adult brain and spinal cord examined by FRIL, no evidence was obtained for the presence of Cx26 in neuronal gap junctions. In addition to its established localization in leptomeningeal gap junctions, these results identify Cx26 as a third connexin (together with Cx30 and Cx43) within astrocytic gap junctions and suggest a further level of complexity to the heterotypic connexin channel combinations formed at these junctions.
在脊椎动物中形成细胞间缝隙连接的连接蛋白家族（Cx）在哺乳动物中枢神经系统中有很好的体现。其中，Cx30和Cx43存在于星形胶质细胞的缝隙连接中。Cx32由少突胶质细胞表达，存在于少突胶质细胞与星形胶质细胞之间的异源缝隙连接以及连续髓鞘层之间的同源缝隙连接中。Cx36 mRNA已在神经元中被鉴定出来，Cx36蛋白已定位在超微结构确定的神经元间缝隙连接处。Cx26也在中枢神经系统中表达，主要在软脑膜内衬中，但也在发育中的脑和脊髓的星形胶质细胞和神经元中被报道。为了进一步确定Cx26在神经组织中的区域、细胞和亚细胞定位，我们使用生化和免疫细胞化学方法在成年小鼠脑以及大鼠脑和脊髓中研究了这种连接蛋白。Northern印迹、Western印迹和免疫荧光研究表明，在这两个物种的许多皮质下区域中，Cx26表达广泛且不均一。通过共聚焦显微镜观察，Cx26在软脑膜以及皮质和皮质下结构的血管周围与Cx30和Cx43共定位。它也定位在少突胶质细胞胞体表面，在那里它与Cx32共同存在。冷冻断裂复制品免疫金标记（FRIL）显示，到出生后第4天，软脑膜细胞间的大多数缝隙连接中有Cx26。到出生后第18天及以后，Cx26存在于星形胶质细胞之间的缝隙连接以及星形胶质细胞与少突胶质细胞之间大多数缝隙连接的星形胶质细胞一侧。在围产期脊髓以及通过FRIL检查的成年脑和脊髓的五个区域中，未获得Cx26存在于神经元缝隙连接中的证据。除了其在软脑膜缝隙连接中已确定的定位外，这些结果将Cx26确定为星形胶质细胞缝隙连接中的第三种连接蛋白（与Cx30和Cx43一起），并表明在这些连接处形成的异型连接蛋白通道组合具有更高的复杂性。
