Localization of brain endothelial luminal and abluminal transporters with immunogold electron microscopy.
Localization of brain endothelial luminal and abluminal transporters with immunogold electron microscopy.
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DOI：
10.1602/neurorx.2.1.27
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发表时间：
2005-01-01
期刊：
影响因子：
--
通讯作者：
Hyman, Shigeyo
中科院分区：
文献类型：
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作者：
Cornford, Eain M;Hyman, Shigeyo
免疫金电子显微镜已经鉴定出多种具有转运和调节功能的血脑屏障（BBB）蛋白。例如，葡萄糖转运蛋白、蛋白激酶C （PKC）和小窝蛋白-1的同工型是血脑屏障特异性的。促性葡萄糖转运蛋白家族（GLUT1）的异构体1仅在内皮（和周细胞）结构域表达，大约75%的蛋白质在人类中是膜定位的。证据表明血脑屏障GLUT1具有水共转运功能。当血脑屏障葡萄糖转运上调时，转运体极性的转变以管腔膜GLUT1增加为特征；但当GLUT1下调时，人血脑屏障的腔膜密度更大。在上调和下调过程中，PKC与这些内皮结构域内的GLUT1共定位，表明PKC介导的机制调节了人类血脑屏障葡萄糖转运蛋白的表达。Occludin和claudin-5（与其他紧密连接蛋白一样）分布受限，仅在血脑屏障的内皮间隙内表达。GFAP（胶质原纤维酸性蛋白）在足突和整个星形胶质细胞中均匀表达。但与基底膜接触的胶质突面向微血管的膜也发生极化，其转运蛋白也可能在星形胶质细胞内重新分布。单羧酸转运体和水通道（Aquaporin-4）的表达在胶质足突富集，并均受到生理调节。我们认为，随着胞吞作用和外排机制作为潜在的神经治疗靶点产生兴趣，电子显微镜对其位点特异性表达模式的确认将继续支持中枢神经系统药物发现过程。
Immunogold electron microscopy has identified a variety of blood-brain barrier (BBB) proteins with transporter and regulatory functions. For example, isoforms of the glucose transporter, protein kinase C (PKC), and caveolin-1 are BBB specific. Isoform 1 of the facilitative glucose transporter family (GLUT1) is expressed solely in endothelial (and pericyte) domains, and approximately 75% of the protein is membrane-localized in humans. Evidence is presented for a water cotransport function of BBB GLUT1. A shift in transporter polarity characterized by increased luminal membrane GLUT1 is seen when BBB glucose transport is upregulated; but a greater abluminal membrane density is seen in the human BBB when GLUT1 is downregulated. PKC colocalizes with GLUT1 within these endothelial domains during up- and downregulation, suggesting that a PKC-mediated mechanism regulates human BBB glucose transporter expression. Occludin and claudin-5 (like other tight-junctional proteins) exhibit a restricted distribution, and are expressed solely within interendothelial clefts of the BBB. GFAP (glial fibrillary acidic protein) is uniformly expressed throughout the foot-processes and the entire astrocyte. But the microvascular-facing membranes of the glial processes that contact the basal laminae are also polarized, and their transporters may also redistribute within the astrocyte. Monocarboxylic acid transporter and water channel (Aquaporin-4) expression are enriched at the glial foot-process, and both undergo physiological modulation. We suggest that as transcytosis and efflux mechanisms generate interest as potential neurotherapeutic targets, electron microscopic confirmation of their site-specific expression patterns will continue to support the CNS drug discovery process.