FIG. 4.

Turnover and processing of wt and F508del-CFTR under calnexin down-regulation by RNAi. CHO cells stably expressing (A) wt or (B) F508del-CFTR were transfected with 60 pmol of RNAi primers specific for calnexin (lanes 6 to 10) or green fluorescent protein RNAi primers as a negative control (lanes 1 to 5). Twenty-four hours posttransfection, the cells were pulse-labeled and chased as before (Fig. 2) for 0 h (lanes 1 and 6), 0.5 h (lanes 2 and 7), 1 h (lanes 3 and 8), 2 h (lanes 4 and 9), and 3 h (lanes 5 and 10). The cells were then lysed, immunoprecipitated with an anti-CFTR Ab, and analyzed as before (see the legend to Fig. 2) to determine the turnover of immature wt CFTR (C) and F508del-CFTR (D) and the processing efficiency of wt CFTR (E). The number of experiments and statistically significant differences are indicated as in Fig. 2.