Department of Microbiology and Immunology, The Geisel School of Medicine at Dartmouth, 604 Remsen, Hanover, NH 03755, USA.
Am J Physiol Lung Cell Mol Physiol. 2012 Oct 15;303(8):L720-7. doi: 10.1152/ajplung.00409.2011. Epub 2012 Aug 17.
The cystic fibrosis transmembrane conductance regulator (CFTR), a Cl(-) channel in airway epithelial cells, plays an important role in maintaining the volume of the airway surface liquid and therefore mucociliary clearance of respiratory pathogens. A recent study has shown that the E3 ubiquitin ligase Neural precursor cells expressed developmentally downregulated (Nedd4-2) ubiquitinates ΔF508-CFTR in pancreatic epithelial cells and that siRNA-mediated silencing of Nedd4-2 increases plasma membrane ΔF508-CFTR. Because the role of Nedd4-2 in regulating wild-type (wt)-CFTR in airway epithelial cells is unknown, studies were conducted to test the hypothesis that Nedd4-2 also ubiquitinates wt-CFTR and regulates its plasma membrane abundance. We found that Nedd4-2 did not affect wt-CFTR Cl(-) currents in Xenopus oocytes. Likewise, overexpression of Nedd4-2 in human airway epithelial cells did not alter the amount of ubiquitinated wt-CFTR. siRNA knockdown of Nedd4-2 in human airway epithelial cells had no effect on ubiquitination or apical plasma membrane abundance of wt-CFTR. Thus Nedd4-2 does not ubiquitinate and thereby regulate wt-CFTR in human airway epithelial cells.
囊性纤维化跨膜电导调节因子（CFTR）是气道上皮细胞中的 Cl(-)通道，在维持气道表面液体体积方面起着重要作用，因此有助于清除呼吸道病原体。最近的一项研究表明，E3 泛素连接酶 Neural precursor cells expressed developmentally downregulated（Nedd4-2）在胰腺上皮细胞中泛素化 ΔF508-CFTR，而 siRNA 介导的 Nedd4-2 沉默增加了质膜 ΔF508-CFTR。由于 Nedd4-2 在调节气道上皮细胞中野生型（wt）-CFTR 的作用尚不清楚，因此进行了研究以检验 Nedd4-2 也泛素化 wt-CFTR 并调节其质膜丰度的假设。我们发现 Nedd4-2 不会影响 Xenopus oocytes 中的 wt-CFTR Cl(-)电流。同样，Nedd4-2 在人气道上皮细胞中的过表达也不会改变泛素化的 wt-CFTR 量。Nedd4-2 的 siRNA 敲低在人气道上皮细胞中对 wt-CFTR 的泛素化或顶端质膜丰度没有影响。因此，Nedd4-2 不会泛素化并调节人气道上皮细胞中的 wt-CFTR。
