RDR01752 rescues F508del-CFTR processing, PM traffic and channel
function
Incubation of CFBE cells expressing F508del-CFTR with the RDR01752
compound rescued F508del-CFTR processing, resulting in the appearance of
the fully-glycosylated form of CFTR (~180 kDa, band C)
in a dose-dependent manner with the maximal correction achieved at 10 µM
(Fig. 1A,B). This effect was comparable to that obtained for VX-809 or
VX-661, and in contrast to that obtained for DMSO (vehicle), which only
led to the appearance of the core-glycosylated form of CFTR
(~140 kDa, band B). This result was also confirmed by
the immunofluorescence detection of the Flag-tag of
mCherry-Flag-F508del-CFTR expressed in CFBE cells without cell
permeabilization, only in cells treated with RDR01752 or VX-809, but not
DMSO (Fig. 1C,D).
To assess the ability of RDR01752 to restore F508del-CFTR function, we
first measured the rate of HS-YFP quenching induced by iodide influx
into cells in CFBE cells stably co-expressing F508del-CFTR and the
HS-YFP (Fig. 2A,B). Both RDR01752 (10 µM) and VX-809 demonstrated rescue
of F508del-CFTR function, although the efficacy of RDR01752 was lower
than that of VX-809. In order to confirm these findings, we then
investigated rescue of F508del-CFTR function by RDR01752 in polarized
CFBE cells in the Ussing chamber (Fig. 2C-F). A significant increase in
equivalent short-circuit current (ΔIsceq) was observed
upon Fsk/IBMX stimulation in cells incubated with either RDR01752 or
VX-809 and stimulated with potentiator genistein (Gen) versusthose incubated with DMSO alone. These data are consistent with the rate
of HS-YFP quenching.