Ribosomal Stalk Protein Silencing Partially Corrects the Delta F508-CFTR Functional Expression Defect

• Authors: Guido Veit, McGill University; Kathryn Oliver, University of Alabama at Birmingham; Pirjo Apaja, McGill University; Doranda Perdomo, McGill University; Aurélien Bidaud-Meynard, McGill University; Sheng-Ting Lin, McGill University; Jingyu Guo, University of Alabama at Birmingham; Mert Icyuz, University of Alabama at Birmingham; Eric Sorscher, Emory University; John L. Hartman IV, University of Alabama at Birmingham; Gergely L. Lukacs, McGill University
• Journal Title: PLoS Biology
• Volume: Volume 14, Number 5
• Publisher: Public Library of Science | 2016-05-01, Pages e1002462-e1002462
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pbio.1002462
• Keywords: Life Sciences & Biomedicine; Biochemistry & Molecular Biology; Biology; TRANSMEMBRANE CONDUCTANCE REGULATOR; NONOPTIMAL-CODON USAGE; CYSTIC-FIBROSIS; SACCHAROMYCES-CEREVISIAE; PLASMA-MEMBRANE; QUALITY-CONTROL; IN-VITRO; TRANSLATION ELONGATION; ENDOPLASMIC-RETICULUM; Small interfering RNAs; HeLa cells; Biosynthesis; Transfectin; Immunoblotting; Elongation factors; Membrane proteins; Yellow fluorescent protein

Abstract

The most common cystic fibrosis (CF) causing mutation, deletion of phenylalanine 508 (ΔF508 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 (ΔF670) in the yeast oligomycin resistance 1 gene (YOR1, an ABC transporter) of Saccharomyces cerevisiae phenocopies the ΔF508-CFTR folding and trafficking defects. Genome-wide phenotypic (phenomic) analysis of the Yor1-ΔF670 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 ΔF508-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 ΔF508-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 CFTRΔF508/ΔF508 human bronchial epithelia. These results and the observation that silencing of other ribosomal stalk proteins partially rescue the loss-of-function phenotype of ΔF508-CFTR suggest that the ribosomal stalk modulates the folding efficiency of the mutant and is a potential therapeutic target for correction of the ΔF508-CFTR folding defect.