Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom; Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France.
School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom.
J Cyst Fibros. 2021 Sep;20(5):843-850. doi: 10.1016/j.jcf.2021.04.013. Epub 2021 May 18.
The clinical response to cystic fibrosis transmembrane conductance regulator (CFTR) modulators varies between people with cystic fibrosis (CF) of the same genotype, in part through the action of solute carriers encoded by modifier genes. Here, we investigate whether phosphate transport by SLC34A2 modulates the function of F508del-CFTR after its rescue by CFTR correctors.
With Fischer rat thyroid (FRT) cells heterologously expressing wild-type and F508del-CFTR and fully-differentiated CF and non-CF human airway epithelial cells, we studied SLC34A2 expression and the effects of phosphate on CFTR-mediated transepithelial ion transport. F508del-CFTR was trafficked to the plasma membrane by incubation with different CFTR correctors (alone or in combination) or by low temperature.
Quantitative RT-PCR demonstrated that both FRT and primary airway epithelial cells express SLC34A2 mRNA and no differences were found between cells expressing wild-type and F508del-CFTR. For both heterologously expressed and native F508del-CFTR rescued by either VX-809 or C18, the magnitude of CFTR-mediated Cl currents was dependent on the presence of extracellular phosphate. However, this effect of phosphate was not detected with wild-type and low temperature-rescued F508del-CFTR Cl currents. Importantly, the modulatory effect of phosphate was observed in native CF airway cells exposed to VX-445, VX-661 and VX-770 (Trikafta) and was dependent on the presence of both sodium and phosphate.
Extracellular phosphate modulates the magnitude of CFTR-mediated Cl currents after F508del-CFTR rescue by clinically-approved CFTR correctors. This effect likely involves electrogenic phosphate transport by SLC34A2. It might contribute to inter-individual variability in the clinical response to CFTR correctors.
囊性纤维化跨膜电导调节因子（CFTR）调节剂的临床反应在相同基因型的囊性纤维化（CF）患者之间存在差异，部分原因是通过修饰基因编码的溶质载体的作用。在这里，我们研究了磷酸转运通过 SLC34A2 是否调节 F508del-CFTR 在 CFTR 校正剂挽救后的功能。
我们使用异源表达野生型和 F508del-CFTR 的 Fischer 大鼠甲状腺（FRT）细胞和完全分化的 CF 和非 CF 人气道上皮细胞，研究了 SLC34A2 的表达以及磷酸对 CFTR 介导的跨上皮离子转运的影响。通过用不同的 CFTR 校正剂（单独或组合）孵育或低温处理，将 F508del-CFTR 转运到质膜。
定量 RT-PCR 表明，FRT 和原代气道上皮细胞均表达 SLC34A2 mRNA，并且在表达野生型和 F508del-CFTR 的细胞之间未发现差异。对于用 VX-809 或 C18 挽救的异源表达和天然 F508del-CFTR，CFTR 介导的 Cl 电流的幅度取决于细胞外磷酸盐的存在。然而，在用野生型和低温挽救的 F508del-CFTR Cl 电流中未检测到磷酸盐的这种作用。重要的是，在暴露于 VX-445、VX-661 和 VX-770（Trikafta）的天然 CF 气道细胞中观察到磷酸盐的调节作用，并且该作用依赖于钠和磷酸盐的存在。
在临床上批准的 CFTR 校正剂挽救 F508del-CFTR 后，细胞外磷酸盐调节 CFTR 介导的 Cl 电流的幅度。这种作用可能涉及 SLC34A2 的电致磷酸转运。它可能有助于 CFTR 校正剂临床反应的个体间变异性。
