Figure 1.

ΔFRD expression promotes ΔF508 CFTR maturation. A) CHO cells were transfected with wt CFTR; ΔF508 CFTR; or ΔF508 CFTR plus ΔFRD, NBD1, or NBD1-RD. Equal amounts of total proteins (∼500 μg) were immunoprecipitated with anti-CFTR and phosphorylated using [γ-³²P]ATP and PKA as described in Materials and Methods. The phosphorylated proteins, except as indicated, were fractionated on SDS-PAGE and detected by autoradiography. Arrows indicate mature CFTR band C or immature CFTR band B. B) Pulse-chase experiments in CHO cells transfected with wt CFTR and the kinetics of nascent CFTR degradation and conversion to mature CFTR were assayed as described in Materials and Methods. C) Identical to panel B, except cells were transfected with ΔF508 CFTR (ΔF508) or ΔF508 plus ΔFRD. D) Same as in panel C, except cells were transfected with ΔF508 CFTR or ΔF508 plus ΔFNBD1. E) Quantitation of the intensities of CFTR bands B and C at the indicated times from all experiments of the type shown in panels B–D. Band intensities at later times are expressed as a percentage of the CFTR band B density at t = 0 (100%). Data presented as mean ± se (n=3).