Intracellular transcytosis of albumin in glomerular endothelial cells after endocytosis through caveolae
Intracellular transcytosis of albumin in glomerular endothelial cells after endocytosis through caveolae
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DOI：
10.1002/jcp.25817
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发表时间：
2017-12-01
影响因子：
5.6
通讯作者：
Nitta, Kosaku
中科院分区：
文献类型：
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作者：
Moriyama, Takahito;Sasaki, Kayo;Nitta, Kosaku
我们先前描述了人肾小球内皮细胞（HRGECs）通过小窝的白蛋白内吞作用。这表明除了窗孔途径之外，还有一种新的白蛋白转胞吞途径。作为下一步，我们研究了小窝内吞作用后HRGECs中的白蛋白转胞吞作用。HRGEC与Alexa Fluor 488标记的牛血清白蛋白孵育0至360分钟。接下来，通过免疫荧光监测核内体、内质网（ER）、高尔基体（GA）、溶酶体和蛋白酶体以及Fc受体、微管和肌动蛋白的标记物。标记的白蛋白与内体的共定位逐渐显著增加，并且在任何时间点均显著高于其他标志物。将白蛋白置于Transwell膜内，在360 min孵育期间扩散通过HRGEC单层。这种通过HRGECs的白蛋白运输被甲基β环糊精（MBCD）（一种小窝破坏剂）抑制。MBCD还减少蛋白尿，导致嘌呤霉素氨基糖苷诱导的肾病小鼠肾小球毛细血管上小窝蛋白-1（Cav-1）表达减少。白蛋白转胞吞作用依赖于早期内体，但不依赖于其他细胞器、Fc受体或细胞骨架组分。小窝破坏阻止了白蛋白通过HRGECs的转运，并减少了肾病小鼠的白蛋白尿。这种新描述的小窝依赖性白蛋白途径通过肾小球内皮细胞是一个潜在的致病机制，白蛋白尿，独立的窗。
We previously described albumin endocytosis through caveolae in human renal glomerular endothelial cells (HRGECs). This suggested a new albumin transcytosis pathway, in addition to the fenestral pathway. As a next step, we investigated albumin transcytosis in HRGECs after caveolar endocytosis. HRGECs were incubated with Alexa Fluor 488-labeled bovine serum albumin from 0 to 360min. Next, markers for endosomes, endoplasmic reticulum (ER), golgi apparatus (GA), lysosomes, and proteasomes and Fc receptors, microtubules, and actin were monitored by immunofluorescence. Labeled albumin co-localization with endosomes was gradually and significantly increased and it was significantly higher than with the other markers at any timepoint. Albumin, placed on inside of the Transwell membrane, diffused through HRGEC monolayers during a 360min incubation period. This transportation of albumin through HRGECs was inhibited by methyl beta cyclodextrin (MBCD), a caveolae disrupting agent. MBCD also decreased albuminuria, causing decreased caveolin-1 (Cav-1) expression on glomerular capillaries, in puromycin aminonucleoside induced nephrotic mice. Albumin transcytosis depends on early endosomes, but not on other organelles, Fc receptors, or cytoskeletal components. Caveolae disruption prevented albumin transportation through HRGECs and decreased albuminuria in nephrotic mice. This newly described caveolae-dependent albumin pathway through glomerular endothelial cells is a potential pathogenetic mechanism for albuminuria, independent of the fenestrae.