Kamasawa N, Sik A, Morita M, Yasumura T, Davidson K G V, Nagy J I, Rash J E
Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1617, USA.
Neuroscience. 2005;136(1):65-86. doi: 10.1016/j.neuroscience.2005.08.027. Epub 2005 Oct 3.
The subcellular distributions and co-associations of the gap junction-forming proteins connexin 47 and connexin 32 were investigated in oligodendrocytes of adult mouse and rat CNS. By confocal immunofluorescence light microscopy, abundant connexin 47 was co-localized with astrocytic connexin 43 on oligodendrocyte somata, and along myelinated fibers, whereas connexin 32 without connexin 47 was co-localized with contactin-associated protein (caspr) in paranodes. By thin-section transmission electron microscopy, connexin 47 immunolabeling was on the oligodendrocyte side of gap junctions between oligodendrocyte somata and astrocytes. By freeze-fracture replica immunogold labeling, large gap junctions between oligodendrocyte somata and astrocyte processes contained much more connexin 47 than connexin 32. Along surfaces of internodal myelin, connexin 47 was several times as abundant as connexin 32, and in the smallest gap junctions, often occurred without connexin 32. In contrast, connexin 32 was localized without connexin 47 in newly-described autologous gap junctions in Schmidt-Lanterman incisures and between paranodal loops bordering nodes of Ranvier. Thus, connexin 47 in adult rodent CNS is the most abundant connexin in most heterologous oligodendrocyte-to-astrocyte gap junctions, whereas connexin 32 is the predominant if not sole connexin in autologous ("reflexive") oligodendrocyte gap junctions. These results clarify the locations and connexin compositions of heterologous and autologous oligodendrocyte gap junctions, identify autologous gap junctions at paranodes as potential sites for modulating paranodal electrical properties, and reveal connexin 47-containing and connexin 32-containing gap junctions as conduits for long-distance intracellular and intercellular movement of ions and associated osmotic water. The autologous gap junctions may regulate paranodal electrical properties during saltatory conduction. Acting in series and in parallel, autologous and heterologous oligodendrocyte gap junctions provide essential pathways for intra- and intercellular ionic homeostasis.
在成年小鼠和大鼠中枢神经系统的少突胶质细胞中，研究了形成缝隙连接的蛋白连接蛋白47和连接蛋白32的亚细胞分布及共关联情况。通过共聚焦免疫荧光显微镜观察，丰富的连接蛋白47在少突胶质细胞胞体以及有髓纤维上与星形胶质细胞的连接蛋白43共定位，而无连接蛋白47的连接蛋白32在结旁区与接触蛋白相关蛋白（caspr）共定位。通过超薄切片透射电子显微镜观察，连接蛋白47免疫标记位于少突胶质细胞胞体与星形胶质细胞之间缝隙连接的少突胶质细胞一侧。通过冷冻断裂复型免疫金标记观察，少突胶质细胞胞体与星形胶质细胞突起之间的大缝隙连接所含连接蛋白47比连接蛋白32多得多。在节间髓鞘表面，连接蛋白47的含量是连接蛋白32的几倍，并且在最小的缝隙连接中，常常没有连接蛋白32。相反，在新描述的施密特-兰特尔曼切迹以及靠近郎飞结的结旁环之间的自体缝隙连接中，连接蛋白32在没有连接蛋白47的情况下定位。因此，成年啮齿动物中枢神经系统中的连接蛋白47是大多数异源性少突胶质细胞与星形胶质细胞缝隙连接中含量最丰富的连接蛋白，而连接蛋白32是自体（“反射性”）少突胶质细胞缝隙连接中主要的甚至可能是唯一的连接蛋白。这些结果阐明了异源性和自体少突胶质细胞缝隙连接的位置及连接蛋白组成，确定结旁区的自体缝隙连接是调节结旁电特性的潜在位点，并揭示含连接蛋白47和含连接蛋白32的缝隙连接是离子及相关渗透水进行长距离细胞内和细胞间移动的通道。自体缝隙连接可能在跳跃传导过程中调节结旁电特性。自体和异源性少突胶质细胞缝隙连接串联和平行作用，为细胞内和细胞间离子稳态提供了重要途径。
