Molecular basis of the functional podocin-nephrin complex:: mutations in the NPHS2 gene disrupt nephrin targeting to lipid raft microdomains
Molecular basis of the functional podocin-nephrin complex:: mutations in the NPHS2 gene disrupt nephrin targeting to lipid raft microdomains
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DOI：
10.1093/hmg/ddg360
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发表时间：
2003-12-15
影响因子：
3.5
通讯作者：
Benzing, T
中科院分区：
文献类型：
--
作者：
Huber, TB;Simons, M;Benzing, T
遗传性肾病综合征是一种异质性疾病，以大量蛋白尿和肾功能衰竭为特征。编码nephrin和podocin的基因NPHS1或NPHS2的突变导致早期重度蛋白尿发作，并迅速进展为终末期肾病，这表明这两种蛋白质对肾小球滤过器的完整性至关重要。Podocin是一种气孔蛋白家族成员，具有预测的发夹样结构，定位于足细胞（肾脏的内脏肾小球上皮细胞）的狭缝隔膜的插入位点。在这里，我们调查不同的致病podocin突变的病理机制。我们发现野生型podocin靶向质膜，并形成涉及羧基和氨基末端胞质结构域的同源寡聚体。podocin与质膜的专门脂筏微区的关联是将nephrin募集到脂筏中的先决条件。相反，致病突变podocin（R138Q和R138X）未能招募nephrin进入筏，因为这些突变体被保留在内质网（R138Q），或因为他们未能与筏（R138X），尽管他们存在于质膜。没有一个突变体增加nephrin信号传导，表明脂筏靶向促进nephrin信号传导。我们的研究结果表明，突变podocin招募nephrin进入脂筏的失败可能是NPHS2的发病机制所必需的。
Hereditary nephrotic syndrome is a heterogeneous disease, characterized by heavy proteinuria and renal failure. Mutations of NPHS1 or NPHS2, the genes encoding for nephrin and podocin, lead to early onset of heavy proteinuria, and rapid progression to end-stage renal disease, suggesting that both proteins are essential for the integrity of the glomerular filter. Podocin is a stomatin protein family member with a predicted hairpin-like structure localizing to the insertion site of the slit diaphragm of podocytes, the visceral glomerular epithelial cells of the kidney. Here we investigate the pathomechanisms of different disease-causing podocin mutations. We show that wild-type podocin is targeted to the plasma membrane, and forms homo-oligomers involving the carboxy and amino terminal cytoplasmic domains. The association of podocin with specialized lipid raft microdomains of the plasma membrane was a prerequisite for recruitment of nephrin into rafts. In contrast, disease-causing mutations of podocin (R138Q and R138X) failed to recruit nephrin into rafts either because these mutants were retained in the endoplasmic reticulum (R138Q), or because they failed to associate with rafts (R138X) despite their presence in the plasma membrane. None of the mutants did augment nephrin signaling, suggesting that lipid raft targeting facilitates nephrin signaling. Our findings demonstrate that the failure of mutant podocin to recruit nephrin into lipid rafts may be essential for the pathogenesis of NPHS2.