Insulin degrading enzyme is localized predominantly at the cell surface of polarized and unpolarized human cerebrovascular endothelial cell cultures
Insulin degrading enzyme is localized predominantly at the cell surface of polarized and unpolarized human cerebrovascular endothelial cell cultures
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DOI：
10.1002/jnr.20809
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发表时间：
2006-05-15
影响因子：
4.2
通讯作者：
Fine, Richard E.
中科院分区：
文献类型：
--
作者：
Lynch, John A.;George, Ana M.;Fine, Richard E.
胰岛素降解酶（IDE）在脑中表达，并且可能在淀粉样β肽（A β）的降解中发挥重要作用。我们的研究结果表明，培养的人脑血管内皮细胞（HCECs），血脑屏障的主要组成部分，表达IDE，并可能通过上调其表达对暴露于低水平的A β作出反应。当放射性标记的A β被引入培养的HCEC的培养基中时，它迅速降解为较小的片段。我们认为这种降解主要是IDES作用的结果，因为它可以被培养基中胰岛素（IDE的竞争性底物）的存在基本上阻断。当培养基中存在脑啡肽酶（另一种可降解A β的蛋白酶）的抑制剂时，未观察到抑制作用。我们的证据表明IDE的作用发生在细胞外，因为内化抑制剂无法影响观察到的降解速率。此外，我们的证据表明IDE的降解发生在质膜上，因为HCEC中存在的大部分IDE是由质膜不可渗透试剂标记的生物素。这种活性似乎是极性依赖性的，因为通过分化的HCEC的每个表面测量A β降解显示基底外侧（面向脑）表面上的更大降解。因此，IDE可能是一个重要的治疗靶点，以减少血管系统中A β的量。(c)2006 Wiley-Liss，Inc.
Insulin degrading enzyme (IDE) is expressed in the brain and may play an important role there in the degradation of the amyloid beta peptide (A beta). Our results show that cultured human cerebrovascular endothelial cells (HCECs), a primary component of the blood-brain barrier, express IDE and may respond to exposure to low levels of A beta by upregulating its expression. When radiolabeled A beta is introduced to the medium of cultured HCECs, it is rapidly degraded to smaller fragments. We believe that this degradation is largely the result of the action of IDES as it can be substantially blocked by the presence of insulin in the medium, a competitive substrate of IDE. No inhibition is seen when an inhibitor of neprilysin, another protease that may degrade A beta, is present in the medium. Our evidence suggests that the action of IDE occurs outside the cell, as inhibitors of internalization fail to affect the rate of the observed degradation. Further, our evidence suggests that degradation by IDE occurs on the plasma membrane, as much of the IDE present in HCECs was biotin-labeled by a plasma membrane impermeable reagent. This activity seems to be polarity dependent, as measurement of A beta degradation by each surface of differentiated HCECs shows greater degradation on the basolateral (brain-facing) surface. Thus, IDE could be an important therapeutic target to decrease the amount of A beta in the cerebrovasculature. (c) 2006 Wiley-Liss, Inc.