Istituto di Biofisica, CNR, Via De Marini, 6, 16149 Genova, Italy.
Int J Mol Sci. 2023 Aug 16;24(16):12838. doi: 10.3390/ijms241612838.
Cystic fibrosis (CF) is one of the most frequent lethal autosomal recessive diseases affecting the Caucasian population. It is caused by loss of function variants of the cystic fibrosis transmembrane conductance regulator (CFTR), a membrane protein located on the apical side of epithelial cells. The most prevalent CF-causing mutation, the deletion of phenylalanine at position 508 (F508del), is characterized by folding and trafficking defects, resulting in the decreased functional expression of the protein on the plasma membrane. Two classes of small-molecule modulators, termed potentiators and correctors, respectively, have been developed to rescue either the gating or the cellular processing of defective F508del CFTR. Kaftrio, a next-generation triple-combination drug, consisting of the potentiator ivacaftor (VX770) and the two correctors tezacaftor (VX661) and elexacaftor (VX445), has been demonstrated to be a life-changing therapeutic modality for the majority of people with CF worldwide. While the mechanism of action of VX770 and VX661 is almost known, the precise mechanism of action and binding site of VX445 have not been conclusively determined. We investigated the activity of VX445 on mutant F508del to identify the protein domains whose expression is mostly affected by this corrector and to disclose its mechanisms of action. Our biochemical analyses revealed that VX445 specifically improves the expression and the maturation of MSD2, heterologously expressed in HEK 293 cells, and confirmed that its effect on the functional expression of defective F508del CFTR is additive either with type I or type II CFTR correctors. We are confident that our study will help to make a step forward in the comprehension of the etiopathology of the CF disease, as well as to give new information for the development and testing of combinations of even more effective correctors able to target mutation-specific defects of the CFTR protein.
囊性纤维化（CF）是影响白种人群体的最常见致死性常染色体隐性疾病之一。它是由位于上皮细胞顶侧的囊性纤维化跨膜电导调节因子（CFTR）的功能丧失变异引起的，CFTR 是一种膜蛋白。最常见的 CF 致病突变是 508 位苯丙氨酸缺失（F508del），其特征是折叠和运输缺陷，导致蛋白在质膜上的功能表达减少。已经开发出两类小分子调节剂，分别称为增效剂和校正剂，分别用于挽救有缺陷的 F508del CFTR 的门控或细胞处理。Kaftrio 是一种新一代三联组合药物，由增效剂 ivacaftor（VX770）和两种校正剂 tezacaftor（VX661）和 elexacaftor（VX445）组成，已被证明是全球大多数 CF 患者改变生活的治疗方式。虽然 VX770 和 VX661 的作用机制几乎已被了解，但 VX445 的确切作用机制和结合位点尚未被确定。我们研究了 VX445 对突变型 F508del 的活性，以确定受该校正剂影响最大的蛋白结构域，并揭示其作用机制。我们的生化分析表明，VX445 特异性地改善了在 HEK 293 细胞中异源表达的 MSD2 的表达和成熟，并证实其对有缺陷的 F508del CFTR 功能表达的影响与 I 型或 II 型 CFTR 校正剂相加。我们相信我们的研究将有助于在理解 CF 疾病的病因发病机制方面取得进展，并为开发和测试更有效的校正剂组合提供新的信息，这些校正剂组合能够针对 CFTR 蛋白的突变特异性缺陷。
