Calreticulin positively regulates the expression and function of epithelial sodium channel
Calreticulin positively regulates the expression and function of epithelial sodium channel
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DOI：
10.1016/j.yexcr.2009.09.023
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发表时间：
2009-11-15
影响因子：
3.7
通讯作者：
Kai, Hirofumi
中科院分区：
文献类型：
--
作者：
Sugahara, Takuya;Koga, Tomoaki;Kai, Hirofumi
上皮钠离子通道（Epithelial sodium channel, ENaC）是位于肾、结肠和肺根尖膜上的异聚钠离子通道。由于ENaC在调节Na+吸收和细胞外液容量方面起着至关重要的作用，其失调会导致严重的表型，包括高血压、低钾血症和气道阻塞。尽管ENaC具有重要意义，但其蛋白质质量控制机制尚不明确。在这里，我们首先展示了钙网蛋白（CRT），一种内质网（ER）中的凝集素样分子伴侣，在ENaC调节中的作用。过表达和敲低分析清楚地表明，CRT积极影响每个ENaC亚基（α， β和γ）的表达。CRT过表达也上调了细胞表面α -、β -和γ - enac的表达。此外，我们发现CRT直接与每个ENaC亚基相互作用。虽然CRT敲除不影响ENaC亚基的重新合成，但CRT过表达降低了洗涤剂（RIPA）不溶性部分中α -、β -和γ -ENaC的表达，表明CRT增强了ENaC亚基的溶解度。与ENaC亚基在细胞内和细胞表面表达增加一致，过表达CRT后ENaC通道活性也增加。因此，我们的研究确定CRT是调节ENaC表达和功能的ER伴侣。(C) 2009爱思唯尔公司版权所有。
Epithelial sodium channel (ENaC) is a heteromultimeric Na+ channel at the apical membrane in the kidney, colon, and lung. Because ENaC plays a crucial role in regulating Na+ absorption and extracellular fluid volume, its dysregulation Causes severe phenotypes including hypertension, hypokalemia, and airway obstruction. Despite the importance of ENaC, its protein quality control mechanism remains less established. Here we firstly show the role of calreticulin (CRT), a lectin-like molecular chaperone in the endoplasmic reticulum (ER), on the regulation of ENaC. Overexpression and knockdown analyses clearly indicated that CRT positively affects the expression of each ENaC Subunit (alpha, beta and gamma). CRT overexpression also up-regulated the cell surface expression of alpha-, beta- and gamma-ENaC. Moreover, we found that CRT directly interacts with each ENaC subunit. Although CRT knockdown did not affect the de novo synthesis of ENaC subunits, CRT overexpression decreased alpha-, beta- and gamma-ENaC expression in the detergent (RIPA)-insoluble fraction, Suggesting that CRT enhanced the solubility of ENaC subunits. Consistent with the increased intracellular and cell surface expression of ENaC subunits, increased channel activity of ENaC was also observed upon overexpression of CRT. Our study thus identifies CRT as an ER chaperone that regulates ENaC expression and function. (C) 2009 Elsevier Inc. All rights reserved.