Ribosomal Stalk Protein Silencing Partially Corrects the [DELTA]F508-CFTR Functional Expression Defect

• Published in: PLoS biology 2016-05, Vol.14 (5)
• Main Authors: Veit, Guido, Oliver, Kathryn, Apaja, Pirjo M, Perdomo, Doranda, Bidaud-Meynard, Aurélien, Lin, Sheng-Ting, Guo, Jingyu, Icyuz, Mert, Sorscher, Eric J, Hartman IV, John L, Lukacs, Gergely L
• Format: Article
• Language: English
• Subjects: Cystic fibrosis; Gene expression; Genes; Genetic aspects; Health aspects; Kinases; Mutation; Ribosomal proteins; Saccharomyces cerevisiae
• ISSN: 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.1002462

The most common cystic fibrosis (CF) causing mutation, deletion of phenylalanine 508 ([delta]F508 or Phe508del), results in functional expression defect of the CF transmembrane conductance regulator (CFTR) at the apical plasma membrane (PM) of secretory epithelia, which is attributed to the degradation of the misfolded channel at the endoplasmic reticulum (ER). Deletion of phenylalanine 670 ([delta]F670) in the yeast oligomycin resistance 1 gene (YOR1, an ABC transporter) of Saccharomyces cerevisiae phenocopies the [delta]F508-CFTR folding and trafficking defects. Genome-wide phenotypic (phenomic) analysis of the Yor1-[delta]F670 biogenesis identified several modifier genes of mRNA processing and translation, which conferred oligomycin resistance to yeast. Silencing of orthologues of these candidate genes enhanced the [delta]F508-CFTR functional expression at the apical PM in human CF bronchial epithelia. Although knockdown of RPL12, a component of the ribosomal stalk, attenuated the translational elongation rate, it increased the folding efficiency as well as the conformational stability of the [delta]F508-CFTR, manifesting in 3-fold augmented PM density and function of the mutant. Combination of RPL12 knockdown with the corrector drug, VX-809 (lumacaftor) restored the mutant function to ~50% of the wild-type channel in primary CFTR[delta]F508/[delta]F508 human bronchial epithelia. These results and the observation that silencing of other ribosomal stalk proteins partially rescue the loss-of-function phenotype of [delta]F508-CFTR suggest that the ribosomal stalk modulates the folding efficiency of the mutant and is a potential therapeutic target for correction of the [delta]F508-CFTR folding defect.