Du Kai, Karp Philip H, Ackerley Cameron, Zabner Joseph, Keshavjee Shaf, Cutz Ernest, Yeger Herman
Program in Developmental & Stem Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Department of Medicine, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA; Department of Molecular Physiology and Biophysics, Howard Hughes Medical Institute, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
J Cyst Fibros. 2015 Mar;14(2):182-93. doi: 10.1016/j.jcf.2014.09.012. Epub 2014 Oct 28.
Cystic fibrosis (CF) is caused by a mutation in the CF transmembrane conductance regulator (CFTR) gene resulting in a loss of Cl(-) channel function, disrupting ion and fluid homeostasis, leading to severe lung disease with airway obstruction due to mucus plugging and inflammation. The most common CFTR mutation, F508del, occurs in 90% of patients causing the mutant CFTR protein to misfold and trigger an endoplasmic reticulum based recycling response. Despite extensive research into the pathobiology of CF lung disease, little attention has been paid to the cellular changes accounting for the pathogenesis of CF lung disease. Here we report a novel finding of intracellular retention and accumulation of a cleaved fragment of F508del CFTR in concert with autophagic like phagolysosomes in the airway epithelium of patients with F508del CFTR. Aggregates consisting of poly-ubiquitinylated fragments of only the N-terminal domain of F508del CFTR but not the full-length molecule accumulate to appreciable levels. Importantly, these undegraded intracytoplasmic aggregates representing the NT-NBD1 domain of F508del CFTR were found in ciliated, in basal, and in pulmonary neuroendocrine cells. Aggregates were found in both native lung tissues and ex-vivo primary cultures of bronchial epithelial cells from CF donors, but not in normal control lungs. Our findings present a new, heretofore, unrecognized innate CF gene related cell defect and a potential contributing factor to the pathogenesis of CF lung disease. Mutant CFTR intracytoplasmic aggregates could be analogous to the accumulation of misfolded proteins in other degenerative disorders and in pulmonary "conformational protein-associated" diseases. Consequently, potential alterations to the functional integrity of airway epithelium and regenerative capacity may represent a critical new element in the pathogenesis of CF lung disease.
囊性纤维化（CF）由囊性纤维化跨膜传导调节因子（CFTR）基因突变引起，导致氯离子通道功能丧失，扰乱离子和液体稳态，进而引发严重的肺部疾病，因黏液阻塞和炎症导致气道阻塞。最常见的CFTR突变F508del见于90%的患者，导致突变的CFTR蛋白错误折叠并引发基于内质网的再循环反应。尽管对CF肺部疾病的病理生物学进行了广泛研究，但对导致CF肺部疾病发病机制的细胞变化关注甚少。在此，我们报告一项新发现，即F508del CFTR裂解片段在F508del CFTR患者气道上皮细胞中与自噬样吞噬溶酶体共同发生细胞内滞留和积累。仅由F508del CFTR N端结构域的多聚泛素化片段而非全长分子组成的聚集体积累到可观水平。重要的是，在纤毛细胞、基底细胞和肺神经内分泌细胞中均发现了代表F508del CFTR NT-NBD1结构域的这些未降解的胞质聚集体。在CF供体的天然肺组织和支气管上皮细胞的体外原代培养物中均发现了聚集体，但在正常对照肺中未发现。我们的研究结果揭示了一种新的、迄今未被认识的先天性CF基因相关细胞缺陷，以及CF肺部疾病发病机制中的一个潜在促成因素。突变的CFTR胞质聚集体可能类似于其他退行性疾病和肺部“构象蛋白相关”疾病中错误折叠蛋白的积累。因此，气道上皮功能完整性和再生能力的潜在改变可能是CF肺部疾病发病机制中的一个关键新因素。
