Abstract
Background: 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.
Methods: 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.
Results: 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 CFTRmediated 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.
Conclusions: 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.
Methods: 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.
Results: 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 CFTRmediated 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.
Conclusions: 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.
| Original language | English |
|---|---|
| Pages (from-to) | 843-850 |
| Number of pages | 8 |
| Journal | Journal of Cystic Fibrosis |
| Volume | 20 |
| Issue number | 5 |
| Early online date | 18 May 2021 |
| DOIs | |
| Publication status | Published - 1 Sept 2021 |
Bibliographical note
Funding Information:This work was supported by a CF Trust Strategic Research Centre award (SRC013) and a Medical Research Council (MRC) Confidence in Concept award (MC_PC_15030) (MAG) and the CF Trust (DNS). Cells from Dr. Randell were supported by Cystic Fibrosis Foundation grant BOUCHE15R0 and NIH grant P30DK065988. Cells from Dr. Pedemonte were supported by the Italian Ministry of Health through Cinque per Mille and Ricerca Corrente (Linea 1).
Funding Information:
We thank R.J. Bridges and Cystic Fibrosis Foundation Therapeutics for compounds P5 and C18, M.L. Fulcher and S.H. Randell for primary cultures of airway epithelial cells, N. Pedemonte and L.J.V. Galietta for FRT cells heterologously expressing CFTR and our laboratory colleagues for valuable discussions and assistance.
Publisher Copyright:
© 2021 The Author(s)
Keywords
- F508del-CFTR
- CFTR correctors
- elexacaftor-tezacaftor-ivacaftor (Trikafta)
- airway epithelia
- phosphate
- SLC34A2