CFTR and cystic fibrosis: Additional experiments including a more detailed analysis of PI effects on the peripheral quality control system for mutant-CFTR in native mouse epithelium, and studies of F508del-CFTR rescue by PIs in native human intestinal epithelium (e.g. rectal biopsies or organoids) are needed to confirm our concept and to explore the applicability of PIs for the rescue of F508del-CFTR processing and function in CF patients.