Kidd Grahame J, Yadav Vijay K, Huang Ping, Brand Stacey L, Low Seng Hui, Weimbs Thomas, Trapp Bruce D
Department of Neurosciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Glia. 2006 Aug 1;54(2):135-45. doi: 10.1002/glia.20366.
Differential targeting of myelin proteins to multiple, biochemically and functionally distinct Schwann cell plasma membrane domains is essential for myelin formation. In this study, we investigated whether the myelin protein P0 contains targeting signals using Madin-Darby canine kidney (MDCK) cells. By confocal microscopy, P0 was localized to MDCK cell basolateral membranes. C-terminal deletion resulted in apical accumulation, and stepwise deletions defined a 15-mer region that was required for basolateral targeting. Alanine substitutions within this region identified the YAML sequence as a functional tyrosine-based targeting signal, with the ML sequence serving as a secondary leucine-based signal. Replacement of the P0 ectodomain with green fluorescent protein altered the distribution of constructs lacking the YAML signal. Coexpression of the myelin-associated glycoprotein did not alter P0 distribution in MDCK cells. The results indicate that P0 contains a hierarchy of targeting signals, which may contribute to P0 localization in myelinating Schwann cells and the pathogenesis in human disease.
髓鞘蛋白靶向多个生化和功能不同的施万细胞质膜结构域对于髓鞘形成至关重要。在本研究中，我们使用犬肾上皮细胞（MDCK）研究髓鞘蛋白P0是否含有靶向信号。通过共聚焦显微镜观察，P0定位于MDCK细胞的基底外侧膜。C末端缺失导致顶端积累，逐步缺失确定了一个15聚体区域，该区域是基底外侧靶向所必需的。该区域内的丙氨酸替代将YAML序列鉴定为基于酪氨酸的功能性靶向信号，而ML序列作为基于亮氨酸的二级信号。用绿色荧光蛋白替换P0胞外结构域改变了缺乏YAML信号的构建体的分布。髓鞘相关糖蛋白的共表达并未改变P0在MDCK细胞中的分布。结果表明，P0含有一系列靶向信号，这可能有助于P0在髓鞘形成施万细胞中的定位以及人类疾病的发病机制。
