SLC26A9 stimulates CFTR expression and function in human bronchial cell lines.
We investigated the possible functional- and physical protein-interactions between two airway Cl(-) channels, SLC26A9 and CFTR. Bronchial CFBE41o- cell lines expressing CFTR(WT) or CFTR(ΔF508) were transduced with SLC26A9. Immunoblots identified a migrating band corresponding to SLC26A9 present in whole-cell lysates as on apical membrane of cells grown on polarized filters. CFTR levels were increased by the presence of SLC26A9 in both CFTR(WT) and CFTR(ΔF508) cell lines. In CFBE41o- cells and CFBE41o-/CFTR(WT) cells transduced with SLC26A9, currents associated to the protein expression were not detected. However, the forskolin (FK)-stimulated currents were enhanced in SLC26A9-transduced cells compared to control cells. Therefore, the presence of SLC26A9 resulted in an increase in CFTR activity (same % of CFTR((inh)-172) or GlyH-101 inhibition in both groups). In CFBE41o-/CFTR(ΔF508) cells transduced with SLC26A9 (at 27°C), a current associated to the protein expression was also lacking. FK-stimulated currents and level of CFTR((inh)-172) inhibition were not different in both groups. The presence of SLC26A9 in Xenopus oocytes expressing CFTR also enhanced the FK-stimulated currents as compared to oocytes expressing CFTR alone. This stimulation was mostly linked to CFTR. An enhancement of FK-stimulated currents was not found in oocytes co-expressing SLC26A9 and CFTR(ΔF508). In conclusion, in both protein expression systems used, SLC26A9 stimulates CFTR activity but not that of CFTR(ΔF508). Our co-immunoprecipitation studies demonstrate a physical interaction between both anion channels. We propose as an alternative hypothesis (not exclusive) to the known SLC26A9-STAS domain/CFTR interaction, that SLC26A9 favors the biogenesis and/or stabilization of CFTR, leading to stimulated currents.
Avella
Martine
M
Laboratoire de Biologie et Physiopathologie des Systèmes Intégrés, Université de Nice-Sophia Antipolis, Nice, France.
Loriol
Céline
C
Boulukos
Kim
K
Borgese
Franck
F
Ehrenfeld
Jordi
J
D000818:Animals; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001980:Bronchi / Q000166:cytology*; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D018408:Patch-Clamp Techniques; D000076988:Sulfate Transporters; D014982:Xenopus laevis
D017920:Antiporters; D002712:Chlorides; C455628:SLC26A9 protein, human; D000076988:Sulfate Transporters; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin