Calreticulin negatively regulates the cell surface expression of cystic fibrosis transmembrane conductance regulator
Calreticulin negatively regulates the cell surface expression of cystic fibrosis transmembrane conductance regulator
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DOI：
10.1074/jbc.m512975200
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发表时间：
2006-05-05
影响因子：
4.8
通讯作者：
Kai, H
中科院分区：
文献类型：
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作者：
Harada, K;Okiyoneda, T;Kai, H
囊性纤维化跨膜传导调节因子(CFTR)是细胞膜上依赖cAMP的氯离子通道，其功能障碍导致囊性纤维化，这是高加索人最常见的致死性遗传病。CFTR的质量控制受到多个分子伴侣的严格控制。在这里，我们发现钙网蛋白(CRT)是内质网(ER)中的一种凝集素样伴侣蛋白，它负向调节细胞表面的CFTR。基于RNA干扰的CRT基因敲除可诱导CFTR的表达增加。一直以来，这种效应都是在活体内观察到的。CRT杂合子(CRT+/-)小鼠较野生型小鼠有更高的CFTR内源性表达。此外，CRT过表达诱导了细胞表面CRT的表达，并显著降低了CFTR的细胞表面表达和功能。CRT的过表达通过增强细胞内吞作用，导致蛋白酶体降解，破坏了细胞表面CFTR的稳定性。CRT羧基结构域的缺失导致其内质网输出，增加了负效应，并增强了与CFTR的相互作用。因此，内质网后隔室中的CRT可能作为细胞表面CFTR的负调节因子。
Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent Cl- channel at the plasma membrane, and its malfunction results in cystic fibrosis, the most common lethal genetic disease in Caucasians. Quality control of CFTR is strictly regulated by several molecular chaperones. Here we show that calreticulin (CRT), which is a lectin-like chaperone in the endoplasmic reticulum (ER), negatively regulates the cell surface CFTR. RNA interference- based CRT knockdown induced the increase of CFTR expression. Consistently, this effect was observed in vivo. CRT heterozygous (CRT+/-) mice had a higher endogenous expression of CFTR than the wild-type mice. Moreover, CRT overexpression induced cell surface expression of CRT, and it significantly decreased the cell surface expression and function of CFTR. CRT overexpression destabilized the cell surface CFTR by enhancing endocytosis, leading to proteasomal degradation. Deletion of the carboxyl domain of CRT, which results in its ER export, increased the negative effect and enhanced the interaction with CFTR. Thus, CRT in the post-ER compartments may act as a negative regulator of the cell surface CFTR.