Hayashi Akiko, Nakashima Keiko, Yamagishi Katsumasa, Hoshi Tomiko, Suzuki Ayaka, Baba Hiroko
Department of Molecular Neurobiology, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji 192-0392, Japan.
Glia. 2007 Aug 1;55(10):1044-52. doi: 10.1002/glia.20529.
Annexin II (AX II) is a member of the family of calcium-dependent actin- and phospholipid-binding proteins implicated in numerous intracellular functions such as signal transduction, membrane trafficking, and mRNA transport, as well as in the regulation of membrane/cytoskeleton contacts and extracellular functions. AX II is expressed in the central nervous system (CNS) and is upregulated in some pathological conditions. However, expression and localization of this protein in the peripheral nervous system (PNS) is still uncertain. In the present study, we examined the expression and distribution of AX II in the PNS. By western blot analysis, we found that a higher level of AX II was present in sciatic nerve homogenates than in brain homogenates. RT-PCR of total RNA from rat sciatic nerves revealed that AX II was synthesized within the nerves. Immunohistological analysis showed the characteristic distribution of AX II in Schmidt-Lanterman incisures (SLI) as well as in the paranodal regions. Localization of AX II in the PNS was examined in two mutant mouse models, shiverer and cerebroside sulfotransferase knockout mice, both of which show increased numbers of SLI. The paranodal axo-glial junction is also disrupted in the latter. Interestingly, the staining intensities of AX II in these regions were increased markedly in both mutants, suggesting that not only the numbers but also AX II content in each incisure and paranodal loop were affected. From its characteristic distribution and molecular features, AX II may be important for myelin function in the PNS.
膜联蛋白II（AX II）是钙依赖性肌动蛋白和磷脂结合蛋白家族的成员，参与多种细胞内功能，如信号转导、膜运输和mRNA转运，以及膜/细胞骨架接触的调节和细胞外功能。AX II在中枢神经系统（CNS）中表达，并在某些病理条件下上调。然而，这种蛋白在周围神经系统（PNS）中的表达和定位仍不确定。在本研究中，我们检测了AX II在PNS中的表达和分布。通过蛋白质印迹分析，我们发现坐骨神经匀浆中AX II的水平高于脑匀浆。对大鼠坐骨神经总RNA进行逆转录聚合酶链反应（RT-PCR）显示AX II在神经内合成。免疫组织学分析显示AX II在施密特-兰特尔曼切迹（SLI）以及结旁区域有特征性分布。在两种突变小鼠模型，即颤抖小鼠和脑苷脂硫酸转移酶基因敲除小鼠中检测了AX II在PNS中的定位，这两种模型均显示SLI数量增加。在后者中，结旁轴突-胶质连接也受到破坏。有趣的是，在这两种突变体中，这些区域的AX II染色强度均显著增加，这表明不仅每个切迹和结旁环中AX II的数量，而且其含量都受到了影响。从其特征性分布和分子特征来看，AX II可能对PNS中的髓鞘功能很重要。
