Statin-sensitive endocytosis of albumin by glomerular podocytes
Statin-sensitive endocytosis of albumin by glomerular podocytes
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DOI：
10.1152/ajprenal.00272.2006
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发表时间：
2007-02-01
影响因子：
4.2
通讯作者：
Topham, Peter S.
中科院分区：
文献类型：
--
作者：
Eyre, Jeanette;Ioannou, Kyriakos;Topham, Peter S.
肾小球足细胞是通过狭缝隔膜的肾小球渗透性的关键调节剂，并且可能在清洁肾小球滤器中起作用。足细胞是否能够内吞蛋白质还不确定。我们研究了蛋白质内吞在条件永生化小鼠和人类足细胞使用FITC-白蛋白直接定量测定和荧光显微镜和电子显微镜在小鼠足细胞。此外，在人、大鼠和小鼠足细胞中研究了体内摄取。小鼠和人足细胞均显示特异性单位点结合FITC-白蛋白，Kd分别为0.91或0.44 mg/ml，B-max分别为3.15或0.81 μ g/mg细胞蛋白。此外，它们还显示出对FITC-白蛋白的强烈内吞作用，Km为9.48或4.5 mg/ml，V-max为474.3或97.4 μ g（.）mg细胞蛋白（-1）（.）h（-1）。免疫球蛋白和转铁蛋白是这一过程的无效竞争者，表明白蛋白具有一定的特异性。通过荧光共聚焦显微镜和电子显微镜可以证明内吞的白蛋白在细胞内囊泡中的积聚。内吞作用对辛伐他汀预处理敏感。在所有三个种属中均发现白蛋白的体内蓄积，但在大鼠中最为明显。我们的结论是足细胞能够内吞蛋白质在他汀类药物敏感的方式。这种功能在健康和疾病中可能非常重要。此外，足细胞的蛋白质内吞作用可能代表了一种有用的、可测量的表型特征，可以针对该表型特征评估潜在有害或有益的干预。
Glomerular podocytes are critical regulators of glomerular permeability via the slit diaphragm and may play a role in cleaning the glomerular filter. Whether podocytes are able to endocytose proteins is uncertain. We studied protein endocytosis in conditionally immortalized mouse and human podocytes using FITC-albumin by direct quantitative assay and by fluorescence microscopy and electron microscopy in mouse podocytes. Furthermore, in vivo uptake was studied in human, rat, and mouse podocytes. Both mouse and human podocytes displayed specific one-site binding for FITC-albumin with K-d of 0.91 or 0.44 mg/ml and B-max of 3.15 or 0.81 mu g/mg cell protein, respectively. In addition, they showed avid endocytosis of FITC-albumin with Km of 9.48 or 4.5 mg/ml and V-max of 474.3 or 97.4 mu g(.)mg cell protein(-1) (.)h(-1), respectively. Immunoglobulin and transferrin were inefficient competitors of this process, indicating some specificity for albumin. Accumulation of endocytosed albumin could be demonstrated in intracellular vesicles by fluorescence confocal microscopy and electron microscopy. Endocytosis was sensitive to pretreatment with simvastatin. In vivo accumulation of albumin was found in all three species but was most pronounced in the rat. We conclude that podocytes are able to endocytose protein in a statin-sensitive manner. This function is likely to be highly significant in health and disease. In addition, protein endocytosis by podocytes may represent a useful, measurable phenotypic characteristic against which potentially injurious or beneficial interventions can be assessed.