Department of Physiology, McGill University, Montréal, Quebec H3E 1Y6, Canada.
Cell. 2012 Jan 20;148(1-2):150-63. doi: 10.1016/j.cell.2011.11.024.
The folding and misfolding mechanism of multidomain proteins remains poorly understood. Although thermodynamic instability of the first nucleotide-binding domain (NBD1) of ΔF508 CFTR (cystic fibrosis transmembrane conductance regulator) partly accounts for the mutant channel degradation in the endoplasmic reticulum and is considered as a drug target in cystic fibrosis, the link between NBD1 and CFTR misfolding remains unclear. Here, we show that ΔF508 destabilizes NBD1 both thermodynamically and kinetically, but correction of either defect alone is insufficient to restore ΔF508 CFTR biogenesis. Instead, both ΔF508-NBD1 energetic and the NBD1-MSD2 (membrane-spanning domain 2) interface stabilization are required for wild-type-like folding, processing, and transport function, suggesting a synergistic role of NBD1 energetics and topology in CFTR-coupled domain assembly. Identification of distinct structural deficiencies may explain the limited success of ΔF508 CFTR corrector molecules and suggests structure-based combination corrector therapies. These results may serve as a framework for understanding the mechanism of interface mutation in multidomain membrane proteins.
多结构域蛋白的折叠和错误折叠机制仍知之甚少。尽管 ΔF508 CFTR（囊性纤维化跨膜电导调节因子）的第一个核苷酸结合域（NBD1）的热力学不稳定性部分解释了突变通道在内质网中的降解，并被认为是囊性纤维化的药物靶点，但 NBD1 和 CFTR 错误折叠之间的联系仍不清楚。在这里，我们表明 ΔF508 在热力学和动力学上均使 NBD1 不稳定，但仅纠正其中一个缺陷不足以恢复 ΔF508 CFTR 的生物发生。相反，ΔF508-NBD1 能量和 NBD1-MSD2（跨膜结构域 2）界面稳定性对于类似于野生型的折叠、加工和转运功能都是必需的，这表明 NBD1 能量和拓扑结构在 CFTR 偶联结构域组装中具有协同作用。鉴定出不同的结构缺陷可能解释了 ΔF508 CFTR 校正分子的有限成功，并提示了基于结构的组合校正治疗方法。这些结果可以作为理解多结构域膜蛋白界面突变机制的框架。
