Megalin(低密度脂蛋白受体相关蛋白2)是一种约600kDa的巨型糖蛋白,介导60多个配体的内吞作用,包括蛋白质,肽,和药物化合物[S.转到,M.Hosojima,H.Kabasawa,A.Saito,Int.J、生化。细胞生物。157,106393(2023)]。它主要在肾近曲小管上皮细胞中表达,以及在大脑中,肺,眼睛,内耳,甲状腺,和胎盘。也已知巨蛋白可介导毒性化合物的内吞作用,尤其是那些导致肾脏和听力障碍的患者[Y.Hori等人。,J.Am.Soc.Nephrol.28,1783-1791(2017)]。遗传性巨蛋白缺乏症导致人类Donnai-Barrow综合征/面眼声肾综合征。然而,目前尚不清楚megalin如何与如此广泛的配体相互作用,并在各种器官中发挥病理作用。在这项研究中,我们阐明了megalin的二聚体结构,从大鼠肾脏中纯化,使用低温电子显微镜。该图谱揭示了内源性配体与整个二聚体的各个区域结合的密度,阐明megalin的多配体受体性质。我们还确定了与受体相关蛋白复合的megalin的结构,megalin的分子伴侣.该结果将有助于进一步研究多个器官中megalin依赖性多配体内吞途径的病理生理学,也将有助于开发针对肾脏和听力障碍的megalin靶向药物,阿尔茨海默病[B.V.Zlokovic等人。,Proc.纳特.Acad.Sci.U.S.A.93,4229-4234(1996)],和其他疾病。
Megalin (low-density lipoprotein receptor-related protein 2) is a giant glycoprotein of about 600 kDa, mediating the endocytosis of more than 60 ligands, including those of proteins, peptides, and drug compounds [S. Goto, M. Hosojima, H. Kabasawa, A. Saito, Int. J. Biochem. Cell Biol. 157, 106393 (2023)]. It is expressed predominantly in renal proximal tubule epithelial cells, as well as in the brain, lungs, eyes, inner ear, thyroid gland, and placenta. Megalin is also known to mediate the endocytosis of toxic compounds, particularly those that cause renal and hearing disorders [Y. Hori et al., J. Am. Soc. Nephrol. 28, 1783-1791 (2017)]. Genetic megalin deficiency causes Donnai-Barrow syndrome/facio-oculo-acoustico-renal syndrome in humans. However, it is not known how megalin interacts with such a wide variety of ligands and plays pathological roles in various organs. In this study, we elucidated the dimeric architecture of megalin, purified from rat kidneys, using cryoelectron microscopy. The maps revealed the densities of endogenous ligands bound to various regions throughout the dimer, elucidating the multiligand receptor nature of megalin. We also determined the structure of megalin in complex with receptor-associated protein, a molecular chaperone for megalin. The results will facilitate further studies on the pathophysiology of megalin-dependent multiligand endocytic pathways in multiple organs and will also be useful for the development of megalin-targeted drugs for renal and hearing disorders, Alzheimer\'s disease [B. V. Zlokovic et al., Proc. Natl. Acad. Sci. U.S.A. 93, 4229-4234 (1996)], and other illnesses.