Exocytosis-Mediated Urinary Full-Length Megalin Excretion Is Linked With the Pathogenesis of Diabetic Nephropathy
Exocytosis-Mediated Urinary Full-Length Megalin Excretion Is Linked With the Pathogenesis of Diabetic Nephropathy
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DOI：
10.2337/db16-1031
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发表时间：
2017-05-01
期刊：
影响因子：
7.7
通讯作者：
Saito, Akihiko
中科院分区：
文献类型：
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作者：
De, Shankhajit;Kuwahara, Shoji;Saito, Akihiko
糖尿病肾病(DN)的有效生物标志物尚未建立。我们先前利用ELISA法发现，在2型糖尿病(T2 DM)患者中，尿全长巨蛋白(C-megalin)水平与糖尿病肾病的进展呈正相关。在此，我们发现T2 DM患者尿胞外小泡(UEV)排泄量和UEV或其胞外部分的C-megalin含量随着蛋白尿期的进展而增加。培养的永生化大鼠近端小管细胞(IRPTCs)经无脂肪酸BSA或糖基化终末产物修饰的BSA(AGE-BSA)、巨蛋白内吞配体、EV排泄增加及其C-巨蛋白含量处理。胞外体特异性抑制剂GW4869可显著抑制IRPTCs通过胞外小泡分泌C-megalin，表明这种排泄主要是由胞吐作用介导的。AGE-BSA治疗IRPTCs引起明显的溶酶体功能障碍，从而刺激多囊泡体的形成，导致胞外体C-megalin排泄增加。在高脂饮食诱导、巨蛋白介导的小鼠肾损伤模型中，尿C-巨蛋白的排泄也通过UEVS增加。总之，胞吐作用介导的尿C-巨蛋白排泄与T2 DM患者糖尿病肾病的发生发展有关，特别是由于巨蛋白介导的近端小管溶酶体功能障碍，因此它可能是与糖尿病肾病发病相关的候选生物标志物。
Efficient biomarkers for diabetic nephropathy (DN) have not been established. Using ELISA, we found previously that urinary levels of full-length megalin (C-megalin), a multiligand endocytic receptor in proximal tubules, was positively correlated with DN progression in patients with type 2 diabetes mellitus (T2DM). Here, we found that urinary extracellular vesicle (UEV) excretion and C-megalin content in UEVs or in their exosomal fraction increased along with the progression of the albuminuric stages in patients with T2DM. Cultured immortalized rat proximal tubule cells (IRPTCs) treated with fatty acid-free BSA or advanced glycation end product-modified BSA (AGE-BSA), endocytic ligands of megalin, increased EV excretion, and their C-megalin content. C-megalin excretion from IRPTCs via extracellular vesicles was significantly blocked by an exosome-specific inhibitor, GW4869, indicating that this excretion is mainly exocytosis-mediated. AGE-BSA treatment of IRPTCs caused apparent lysosomal dysfunction, which stimulated multivesicular body formation, resulting in increased exosomal C-megalin excretion. In a high-fat diet-induced, megalin-mediated kidney injury model in mice, urinary C-megalin excretion also increased via UEVs. Collectively, exocytosis-mediated urinary C-megalin excretion is associated with the development and progression of DN in patients with T2DM, particularly due to megalin-mediated lysosomal dysfunction in proximal tubules, and hence it could be a candidate biomarker linked with DN pathogenesis.