Correcting Pathogenic TGF beta Activity in the Airway

摘要 肺内气道表面液体（ASL）的稳态主要依赖于氯离子（Cl-）的转运， 由顶端通道CFTR（囊性纤维化跨膜传导调节因子）介导。CFTR基因 与高加索人中最常见的常染色体隐性遗传病囊性纤维化（CF）相关的突变 导致CFTR功能丧失和ASL容量调节严重受损。删除F508 CFTR基因中的F508 del存在于90%的CF患者中;它阻断CFTR生物合成过程，减少CFTR的表达， CFTR Cl-通道功能，并降低CFTR mRNA的稳定性和翻译。据估计， 当CFTR通道功能低于正常值的1%且至少为正常值的10%时， 需要功能来减轻严重的表型。针对CF中基本分子缺陷的治疗 显示出潜力，但对大多数患者来说是不够的。虽然FDA批准的药物VX-770 CFTR通道“开放”概率和改善肺功能的患者不到10%的罕见 突变G551 D，VX-770和校正剂VX-809的组合使用，其拯救了折叠和加工， 缺陷仅对F508 del患者略微有效。患有更严重肺部疾病的CF患者 对这种疗法完全抗拒。转化生长因子-β1参与纠正剂耐药 通过阻断CFTR翻译和抑制对残留ASL稳态至关重要的辅助离子通道进行治疗 在CF中，即BK（Ca+2激活的K+通道）和ANO 1（Ca+2激活的Cl-通道）。高TGF-β1水平 由于TGF-β1基因多态性，在40%的F508 del纯合子患者中可见。空气污染物， 包括香烟烟雾也会增加TGF-β1水平。伴随的TGF-β1的上调， 增加了F508 del纯合子患者CF肺病的严重程度， 针对F508 del-CFTR拯救的治疗。我们认为，针对致病性TGF-β1活性， 通过恢复BK和ANO 1通道的功能，改善CF中残留ASL体积的稳态。它 还将通过恢复减少的508 del-CFTR来增加F508 del-CF患者的治疗功效 翻译并允许增加突变CFTR通道功能的活性。因此，定义TGF-β1 肺组织中的介质提供了设计消除致病性TGF-β1的新型药物的机会 CF患者的活动。我们的中心假设是，有针对性地降低TGF-β1活性将改善 对CFTR、BK和ANO 1通道和ASL稳态的负面影响，并提供了一种新的方法， 治疗F508 del CF患者。我们的具体目标是检验以下假设：（1）Dab 2是TGF-β1的接头， 通过引导Smad 3的核转运，抑制CF支气管上皮中残留的ASL稳态， 抑制辅助通道BK和ANO 1;（2）Dab 2-Smad 3相互作用上调microRNA 抑制辅助通道并阻断校正因子介导的F508 del-CFTR拯救;和（3） TGF-β1在CF支气管上皮中的致病活性需要Dab 2-Smad 3相互作用。

ABSTRACT Homeostasis of the airway surface liquid (ASL) in lung is critically dependent on chloride ion (Cl-) transport, mediated by the apical channel, CFTR (cystic fibrosis transmembrane conductance regulator). CFTR gene mutations associated with the most common autosomal recessive disease in Caucasians, cystic fibrosis (CF) result in loss of CFTR function and severe impairment of the ASL volume regulation. Deletion of F508 (F508del) in the CFTR gene is present in 90% of CF patients; it blocks CFTR biosynthetic processing, reduces CFTR Cl- channel function, and decreases CFTR mRNA stability and translation. It is estimated that the classic severe CF phenotype develops when the CFTR channel function is less than 1% of normal and at least 10% function is needed to alleviate the severe phenotype. Therapies targeting the basic molecular defects in CF demonstrate potential but are insufficient for most patients. While the FDA-approved drug VX-770 potentiates CFTR channel “open” probabilities and improves lung function for less than 10% of patients with the rare mutation G551D, the combined use of VX-770 and a corrector VX-809 that rescues the folding and processing defect was only marginally effective for F508del patients. CF patients with more severe lung disease were entirely resistant to such therapy. Transforming growth factor (TGF)-β1 contributes to resistance of corrector therapy by blocking CFTR translation and represses ancillary ion channels critical to residual ASL homeostasis in CF, namely BK (a Ca+2-activated K+ channel) and ANO1 (a Ca+2-activated Cl- channel). High TGF-β1 levels are seen in 40% of F508del homozygous patients due to polymorphisms in the TGF-β1 gene. Air pollutants, including cigarette smoke also increase TGF-β1 levels. The concomitant upregulation of TGF-β1 in turn increases the severity of CF lung disease in F508del homozygous patients and presents a major block to therapies aimed at F508del-CFTR rescue. We propose that targeting the pathogenic TGF-β1 activity would improve the residual ASL volume homeostasis in CF by restoring the function of BK and ANO1 channels. It would also increase the efficacy of therapy for F508del CF patients by restoring the diminished 508del-CFTR translation and allowing increased activity of the mutant CFTR channel function. Thus, defining TGF-β1 mediators in lung tissue presents an opportunity to design novel drugs eliminating the pathogenic TGF-β1 activity in CF patients. Our central hypothesis is that the targeted reduction of TGF-β1 activity will ameliorate negative effects on CFTR, BK, and ANO1 channels and ASL homeostasis, and provide a novel approach to treat F508del CF patients. Our specific aims are to test the hypothesis: (1) that Dab2 is a TGF-β1 adaptor that inhibits the residual ASL homeostasis in CF bronchial epithelium by directing nuclear transport of Smad3 to repress the ancillary channels, BK and ANO1; (2) that the Dab2-Smad3 interactions upregulates microRNAs that repress the ancillary channels and block corrector-mediated rescue of F508del-CFTR; and (3) that a Dab2-Smad3 interaction is required for the pathogenic activity of TGF-β1 in CF bronchial epithelium.