Deep mutational scan to compare the effects of two FDA-approved correctors on the plasma membrane expression of 129 known cystic fibrosis variants

Cystic fibrosis (CF) is a chronic genetic disease caused by mutations that compromise the expression and/ or function of the cystic fibrosis transmembrane conductance regulator chloride channel (CFTR). Most people with CF harbor a common misfolded CFTR variant (delta F508), which can be rescued by combination therapies containing "corrector" compounds that restore its expression. Nevertheless, there are over 400 other CF variants that differ in their sensitivity to correctors for reasons that remain unclear. In this work, we utilize deep mutational scanning to quantitatively compare the effects of two FDA-approved correctors on the plasma membrane expression of 129 known CF variants, including 45 that are currently unclassified. Across 67 variants with attenuated expression, we find that VX-661-sensitive variants generally exhibit intermediate expression and feature mutations near its binding pocket in transmembrane domains (TMDs) 1, 2, 3, and 6. VX-445 also primarily rescues variants with intermediate expression but is instead uniquely effective towards mutations near its binding pocket in TMDs 10 & 11.

囊性纤维化（Cystic fibrosis, CF）是一类由突变引发的慢性遗传性疾病，此类突变会损害囊性纤维化跨膜传导调节因子氯离子通道（cystic fibrosis transmembrane conductance regulator chloride channel, CFTR）的表达和/或功能。大部分CF患者携带一种常见的错误折叠CFTR变异体（delta F508），该变异体可通过含有“矫正剂”类化合物的联合疗法实现挽救，这类化合物可恢复其表达水平。然而，尚有超过400种其他CF变异体，它们对矫正剂的敏感性存在差异，具体机制目前仍未阐明。本研究采用深度突变扫描技术，定量对比了两种FDA批准的矫正剂对129种已知CF变异体细胞膜表达水平的影响，其中包含45种目前尚未分类的变异体。在67种表达减弱的CF变异体中，我们发现对VX-661敏感的变异体通常呈现中等程度的表达水平，且其突变位点位于跨膜结构域（TMDs）1、2、3和6中靠近其结合口袋的区域。VX-445同样主要挽救表达水平中等的变异体，但它对位于跨膜结构域10和11中靠近其结合口袋的突变体具有独特的疗效。