FIGURE 4.

Arsenic (10 ppb) increases multiubiquitinylation and degradation of CFTR in a time-dependent manner. A, cells were treated with arsenic for the times indicated, CFTR was immunoprecipitated using a monoclonal antibody (clone M3A7, Upstate Biotech Millipore), and ubiquitinylated CFTR was detected via Western blot analysis using an anti-ubiquitin antibody (FK2, BioMol). Cells were treated with chloroquine (200 μm) to allow the accumulation of ubiquitinylated CFTR (Ub-CFTR) in quantities that could be detected by Western blot analysis. Similar amounts of CFTR were immunoprecipitated in all cases (data not shown); thus, differences in the amount of ubiquitinylated CFTR detected were not due to differences in the efficiency of the immunoprecipitation step for CFTR. Representative blots are shown. B, cells were treated with arsenic for the times indicated in the absence of chloroquine, and Western blot analysis was performed to examine the time-dependent effect of arsenic on CFTR abundance. Data were normalized for ezrin abundance. n = 4/group. *, p < 0.05 versus control.