CFTR and cystic fibrosis: We thank H. Cuppens, P. Martin, and P. Thomas for fruitful discussions; M. Welsh for enthusiastic support; D. Gruenert, K. Kunzelmann, and E. Sorscher for the CFBE41o- cells; R. Frizzell and M. Glover for primary HBE cells; J. Riordan, T. Jensen, and CF Foundation Therapeutics for anti-CFTR antibodies; E. Krüger for the HA-Ub-GFP plasmid; and the Viral Vector Core Facility at the University of Iowa for recombinant adenoviruses.