FIGURE 1:

PIAS4 increases CFTR expression in CFBE airway cells. (A) Overexpression of PIAS4 increases the steady-state expression of WT and F508del CFTR. Stable CFBE-WT and -F508del cells were transiently transfected with or without Flag-PIAS4 as described under Materials and Methods. Whole cell lysates were extracted 48 h after transfection and protein expression detected by IB using the indicated antibodies. CFTR protein levels were quantified and normalized to control from three independent experiments. (*p < 0.05; **p < 0.01). (B) PIAS4 enhances the efficacy of CFTR correctors in CFBE cells stably expressing F508del CFTR. Flag-PIAS4 was expressed in CFBE-F508del cells as described in A. After 24 h, the transfected cells were treated with dimethyl sulfoxide (DMSO), 10 μM C18, or 10 μM VX-809 for 24 h, and then cells were lysed and analyzed by IB. The numbers below the CFTR blots give the band C densities relative to control (DMSO). (C) The impact of PIAS4 on CFTR expression depends on its SUMO E3 ligase activity. Flag-PIAS4 and its catalytic mutant, Flag-PIAS4-CA, were transiently transfected into CFBE-F508del cells. Whole cell lysates were examined by IB using the indicated antibodies. CFTR signals were normalized to control values in seven independent experiments (***p < 0.001).