Division of Matrix Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Division of Vascular Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden ; Department of Immunology, Genetic and Pathology, Uppsala University, Uppsala, Sweden.
PLoS One. 2013 Dec 20;8(12):e83133. doi: 10.1371/journal.pone.0083133. eCollection 2013.
Glomerular podocyte cells are critical for the function of the renal ultrafiltration barrier. Especially, the highly specialized cell-cell junction of podocytes, the slit diaphragm, has a central role in the filtration barrier. This is highlighted by the fact that mutations in molecular components of the slit diaphragm, including nephrin and Cd2-associated protein (Cd2ap), result in proteinuric diseases in man. Dendrin is a poorly characterized cytosolic component of the slit diaphragm in where it interacts with nephrin and Cd2ap. Dendrin is highly specific for the podocyte slit diaphragm, suggesting that it has a dedicated role in the glomerular filtration barrier. In this study, we have generated a dendrin knockout mouse line and explored the molecular interactions of dendrin. Dendrin-deficient mice were viable, fertile, and had a normal life span. Morphologically, the glomerulogenesis proceeded normally and adult dendrin-deficient mice showed normal glomerular histology. No significant proteinuria was observed. Following glomerular injury, lack of dendrin did not affect the severity of the damage or the recovery process. Yeast two-hybrid screen and co-immunoprecipitation experiments showed that dendrin binds to Wt1-interacting protein (Wtip) and growth arrest and DNA-damage-inducible 45 alpha (Gadd45a). Wtip and Gadd45a mediate gene transcription in the nucleus, suggesting that dendrin may have similar functions in podocytes. In line with this, we observed the relocation of dendrin to nucleus in adriamycin nephropathy model. Our results indicate that dendrin is dispensable for the function of the normal glomerular filtration barrier and that dendrin interacts with Wtip and Gadd45a.
肾小球足细胞对于肾脏超滤屏障的功能至关重要。特别是足细胞的高度特化的细胞-细胞连接，即裂孔隔膜，在滤过屏障中起着核心作用。这一点从裂孔隔膜分子成分的突变，包括nephrin 和 Cd2 相关蛋白 (Cd2ap)，导致人类蛋白尿疾病的事实得到了强调。Dendrin 是裂孔隔膜中一种特征不明显的细胞质成分，它与 nephrin 和 Cd2ap 相互作用。Dendrin 特异性地存在于足细胞裂孔隔膜中，这表明它在肾小球滤过屏障中具有专门的作用。在本研究中，我们生成了 dendrin 敲除小鼠系，并探索了 dendrin 的分子相互作用。dendrin 缺陷型小鼠是有活力的、可育的，并且具有正常的寿命。形态学上，肾小球发生正常，成年 dendrin 缺陷型小鼠表现出正常的肾小球组织学。未观察到明显的蛋白尿。在肾小球损伤后，缺乏 dendrin 并不影响损伤的严重程度或恢复过程。酵母双杂交筛选和共免疫沉淀实验表明，dendrin 与 Wt1 相互作用蛋白 (Wtip) 和生长停滞和 DNA 损伤诱导 45α (Gadd45a) 结合。Wtip 和 Gadd45a 在核内介导基因转录，表明 dendrin 在足细胞中可能具有类似的功能。与此一致，我们在阿霉素肾病模型中观察到 dendrin 向核内的重新定位。我们的结果表明，dendrin 对于正常肾小球滤过屏障的功能是可有可无的，并且 dendrin 与 Wtip 和 Gadd45a 相互作用。
