Function of subendothelial basement membranes in Blood-Brain Barrier

我们报告的分子克隆的跨膜型免疫球蛋白超家族的一个新成员，并指定为限制蛋白的编码蛋白，因为它选择性地定位于胶质细胞限制在小鼠大脑。限制蛋白cDNA获得使用消减杂交程序，旨在确定负责血脑屏障功能的分子。使用限制蛋白特异性抗体进行的蛋白质印迹表明，该基因产物在小鼠脑和原代小鼠星形胶质细胞中显着表达，并分布在质膜上。免疫组织化学研究，共聚焦和电子显微镜清楚地表明高度极化定位在血管周围区域和软脑膜下的星形胶质细胞的终足在体内。Limitrin在脊髓和大脑的许多区域中表达，但在缺乏血脑屏障的正中隆起或穹窿下器官（脑室周围器官）中不表达。冷损伤对血脑屏障的破坏导致限制蛋白表达的急剧减少。此外，在从冷损伤中恢复的过程中，血管周围终足中limitrin表达的增加与损伤边缘内毛细血管的血管生成的恢复相关。我们的研究结果表明，limitrin是物理和功能相关的血脑屏障，这意味着这种蛋白质可能是有用的屏障完整性的诊断决定因素。

We report the molecular cloning of a new member of the transmembrane-type immunoglobulin superfamily and designate the encoded protein as limitrin since it selectively localized to glia limitans in mouse brain. Limitrin cDNA was obtained using a subtractive hybridization procedure designed to identify molecules responsible for blood-brain barrier function. Western blots using a limitrin-specific antibody demonstrated that the gene product is expressed significantly in mouse brain and primary murine astrocytes, and is distributed in the plasma membrane. Immunohistochemical studies using confocal and electron microscopy clearly demonstrated highly polarized localization in astroglial endfeet in the perivascular region and under the pia mater in vivo. Limitrin is expressed in spinal cord and many areas of the brain but not in the median eminence or subfornical organ (the circumventricular organs) where the blood-brain barrier is lacking. Disruption of the blood-brain barrier by cold injury resulted in a drastic reduction in limitrin expression. Furthermore, during retrieval from cold injury the increased expression of limitrin in perivascular endfeet correlated with the recovery of angiogenesis in capillaries within the lesion margins. Our results suggest that limitrin is physically and functionally associated with the blood-brain barrier, implying that this protein may be useful as a diagnostic determinant of barrier integrity.