Megalin functions as an endocytic sonic hedgehog receptor
Megalin functions as an endocytic sonic hedgehog receptor
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DOI：
10.1074/jbc.m201933200
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发表时间：
2002-07-12
影响因子：
4.8
通讯作者：
Argraves, WS
中科院分区：
文献类型：
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作者：
McCarthy, RA;Barth, JL;Argraves, WS
缺乏形态发生素Sonic hedgehog（Shh）或内吞受体megalin的胚胎表现出常见的神经发育异常。因此，我们研究了这两种蛋白质之间存在功能关系的可能性。在胚胎发育过程中，发现megalin表达沿着神经上皮细胞的顶面，并与Shh共同表达在神经管的腹底板。利用酶联免疫吸附试验、同源配体置换和表面等离子体共振技术，发现Shh的氨基端片段（N-Shh）与megalin具有高亲和力结合。表达巨蛋白的细胞通过巨蛋白拮抗剂（即抗受体相关蛋白和抗巨蛋白抗体）抑制的机制内化NShh。肝素还抑制NShh内吞作用，暗示蛋白聚糖在内化过程中，如已描述的其他巨蛋白配体。使用氯喹抑制溶酶体蛋白酶活性表明，N-Shh通过巨蛋白内吞不能有效地靶向溶酶体降解。巨蛋白内化的N-Shh绕过溶酶体的能力可能与发现N-Shh和巨蛋白之间的相互作用在低pH下抵抗解离有关。总之，这些发现表明巨蛋白是NShh的有效内吞受体。此外，他们牵连megalin作为一个新的调节成分的Shh信号通路。
Embryos deficient in the morphogen Sonic hedgehog (Shh) or the endocytic receptor megalin exhibit common neurodevelopmental abnormalities. Therefore, we have investigated the possibility that a functional relationship exists between the two proteins. During embryonic development, megalin was found to be expressed along the apical surfaces of neuroepithelial cells and was co-expressed with Shh in the ventral floor plate of the neural tube. Using enzyme-linked immunosorbent assay, homologous ligand displacement, and surface plasmon resonance techniques, it was found that the amino-terminal fragment of Shh (N-Shh) bound to megalin with high affinity. Megalin-expressing cells internalized NShh through a mechanism that was inhibited by antagonists of megalin, viz. anti-receptor-associated protein and anti-megalin antibodies. Heparin also inhibited NShh endocytosis, implicating proteoglyeans in the internalization process, as has been described for other megalin ligands. Use of chloroquine to inhibit lysosomal proteinase activity showed that N-Shh endocytosed via megalin was not efficiently targeted to the lysosomes for degradation. The ability of megalin-internalized N-Shh to bypass lysosomes may relate to the finding that the interaction between N-Shh and megalin was resistant to dissociation with low pH. Together, these findings show that megalin is an efficient endocytic receptor for NShh. Furthermore, they implicate megalin as a new regulatory component of the Shh signaling pathway.