Megalin binds and internalizes angiotensin II
Megalin binds and internalizes angiotensin II
复制标题
DOI：
10.1152/ajprenal.00243.2004
复制
发表时间：
2005-02-01
影响因子：
4.2
通讯作者：
Hammond, TG
中科院分区：
文献类型：
--
作者：
Gonzalez-Villalobos, R;Klassen, RB;Hammond, TG
巨蛋白是一种丰富的膜蛋白，与受体介导的内吞作用密切相关。巨蛋白在体内的主要功能仍未完全确定，因为巨蛋白通常面临特殊的环境，如肾小球滤液、气道、附睾液、甲状腺胶体和卵黄囊液，这些环境缺乏许多已知的配体。在 ANG II 内化的研究过程中，我们惊讶地发现，永生化卵黄囊细胞（BN-16 细胞）仅部分吸收标记的 ANG II 被特定的肽抑制剂和血管紧张素 1 型受体的直接竞争者阻断。这促使我们测试巨蛋白是否是 ANG II 的受体。四行直接证据表明巨蛋白及其伴侣蛋白 cubilin（在较小程度上）是 ANG II 的受体。首先，在 BN-16 细胞中，抗巨蛋白和抗 cubilin 抗血清干扰 ANG II 摄取。其次，同样在 BN-16 细胞中，纯 ANG II 竞争对已知巨蛋白配体的摄取。第三，在从小鼠中提取的近端小管细胞刷状缘膜囊泡中，抗巨蛋白抗血清干扰ANG II结合。第四，在表面等离子共振实验中，纯化的巨蛋白直接结合 ANG II。巨蛋白是 ANG II 受体的发现表明巨蛋白通路在体内具有重要的新功能。这些结果还表明，某些组织中的 ANG II 内化是巨蛋白依赖性的，并且巨蛋白可能在调节近端小管 ANG II 水平中发挥作用。
Megalin is an abundant membrane protein heavily involved in receptor-mediated endocytosis. The major functions of megalin in vivo remain incompletely defined as megalin typically faces specialized milieus such as glomerular filtrate, airways, epididymal fluid, thyroid colloid, and yolk sac fluid, which lack many of its known ligands. In the course of studies on ANG II internalization, we were surprised when only part of the uptake of labeled ANG II into immortalized yolk sac cells (BN-16 cells) was blocked by specific peptide inhibitors and direct competitors of the angiotensin type 1 receptor. This led us to test if megalin was a receptor for ANG II. Four lines of direct evidence demonstrate that megalin and, to a lesser extent, its chaperone protein cubilin are receptors for ANG II. First, in BN-16 cells anti-megalin and anti-cubilin antisera interfere with ANG II uptake. Second, also in BN-16 cells, pure ANG II competes for uptake of a known megalin ligand. Third, in proximal tubule cell brush-border membrane vesicles extracted from mice, anti-megalin antisera interfere with ANG II binding. Fourth, purified megalin binds ANG II directly in surface plasmon resonance experiments. The finding that megalin is a receptor for ANG II suggests a major new function for the megalin pathway in vivo. These results also indicate that ANG II internalization in some tissues is megalin dependent and that megalin may play a role in regulating proximal tubule ANG II levels.