Analysis of physiological and pathophysiological functions of megalin in the proximal tubules and clinical application of its molecular features

meggalin是一种大糖蛋白，属于低密度脂蛋白受体基因家族。它在近端小管细胞的顶膜上大量表达，作为一种内吞清除受体，对肾小球滤过的各种配体蛋白进行再吸收和代谢。利用大量表达meggalin的卵黄囊肿瘤来源的L2细胞，我们发现meggalin是一种介导细胞摄取和代谢β_2-微球蛋白（一种尿毒症毒素蛋白）的内吞受体。在终末期肾病患者中，β_2-m在血清中积累并引起透析相关淀粉样变性（DRA）。为了将分子功能应用于临床实践，我们开发了一种用于肾衰竭动物的megalin表达细胞皮下植入系统。该系统将是一种新的组织工程策略，以弥补当前透析治疗的局限性，提高透析患者的生存和生活质量。我们还研究了meggalin在晚期糖基化终产物（AGEs）的细胞摄取和代谢中的作用。糖尿病患者会产生过多的AGEs。低分子量形式由肾小球过滤，并由近端小管细胞重吸收和代谢；这些过程可能与糖尿病肾病的发病机制有关，特别是与小管间质损伤有关。此外，AGEs在尿毒症患者的血清中积累，并参与DRA和动脉粥样硬化的发病机制。利用L2细胞系统，我们发现meggalin介导了AGEs的细胞摄取和代谢。我们还在细胞中发现了一种新的与巨galin相互作用的AGE结合蛋白。在上述研究的基础上，我们还研究了肾脏疾病进展的其他分子机制。

Megalin is a large glycoprotein belonging to the LDL receptor gene family. It is abundantly expressed at the apical membrane of proximal tubule cells and functions as an endocytic scavenger receptor for reabsorbing and metabolizing various ligand proteins filtered by glomeruli.Using yolk sac tumor-derived L2 cells that express megalin abundantly, we identified megalin as being an endocytic receptor mediating cellular uptake and metabolism of β_2-microglobulin, a uremic toxin protein. In patients with endstage renal disease β_2-m accumulates in serum and causes dialysis-related amyloidosis(DRA). To apply the molecular function to clinical practice for β_2-m removal We developed a system for subcutaneous implantation of megalin-expressing cells in renal failure animals. This system would be a novel tissue engineering strategy to compensate for the limitations of current dialysis therapy and improve the survival and quality of life of dialysis patients.We also investigated the role of megalin in cellular uptake and metabolism of advanced glycation endproducts (AGEs). AGEs are generated excessively in diabetes. The low-molecular-weight forms are filtered by glomeruli and reabsorbed and metabolized by proximal tubule cells ; the processes are likely associated with the pathogenesis of diabetic nephropathy, especially of the tubulointerstitial injury. Also, AGEs accumulate in serum of uremic patients and are involved in the pathogenesis of DRA and athelosclerosis in those. Using the L2 cell system, we found that megalin mediates cellular uptake and metabolism of AGEs. We also identified a novel AGE binding protein in the cells which interacts with megalin.In association with the researches described above, we also investigated the other molecular mechanisms of progression of renal diseases.