lumacaftor and benzyloxycarbonylleucyl-leucyl-leucine-aldehyde

Mutations in ABCA4 cause Stargardt macular degeneration, which invariably ends in legal blindness. We studied two common mutants, A1038V (in NBD1) and G1961E (in NBD2), with the purpose of exploring how they interact with the cell's quality control mechanism. The study was designed to determine how these mutants can be rescued.. We expressed wt and mutant ABCA4 in HEK293 cells and studied the effect of the mutations on trafficking and processing and the ability of correctors to rescue them. We used a combination of western blotting, confocal microscopy and surface biotinylation coupled with pulldown of plasma membrane proteins.. G1961E is sensitive to inhibitors of the aggresome, tubacin and the lysosome, bafilomycin A. Both mutants cause a reduction in heat shock protein, Hsp27. Incubation of HEK293 cells expressing the mutants with VX-809, an FDA approved drug for the treatment of cystic fibrosis, increased the levels of A1038V and G1961E by 2- to 3-fold. Importantly, VX-809 increased the levels of both mutants at the plasma membrane suggesting that trafficking had been restored. Transfecting additional Hsp27 to the cells also increased the steady state levels of both mutants. However, in combination with VX-809 the addition of Hsp27 caused a dramatic increase in the protein expression particularly in the G1961 mutant which increased approximately 5-fold.. Our results provide a new mechanism for the rescue of ABCA4 trafficking mutants based on the restoration of Hsp27. Our results provide a pathway for the treatment of Stargardt disease.

Topics: Aminopyridines; Anilides; ATP-Binding Cassette Transporters; Benzodioxoles; Cell Membrane; Cystic Fibrosis Transmembrane Conductance Regulator; Gene Expression Regulation; HEK293 Cells; HSP27 Heat-Shock Proteins; Humans; Hydroxamic Acids; Leupeptins; Lysosomes; Macular Degeneration; Mutation; Protein Transport; Stargardt Disease

Cystic Fibrosis is the most common recessive autosomal rare disease found in Caucasian. It is caused by mutations on the Cystic Fibrosis Transmembrane Conductance Regulator gene (CFTR) that encodes for a protein located on the apical membrane of epithelial cells. c.3909C>G (p.Asn1303Lys) is one of the most common worldwide mutations located in nucleotide binding domain 2. The effect of the p.Asn1303Lys mutation on misprocessing was studied by immunofluorescence and western blotting analysis in presence and absence of treatment. To evaluate the functionality of potentially rescued p.Asn1303Lys-CFTR, we assessed the channel activity by radioactive iodide efflux. No recovery of the activity was observed in transfected cultured cells treated with VX-809. Thus, our results suggest that multiple drugs may be needed for the treatment of c.3909C>G patients in order to correct and activate p.Asn1303Lys-CFTR as it shows folding and functional defects.

Topics: Aminopyridines; Benzodioxoles; Blotting, Western; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Epithelial Cells; HeLa Cells; Humans; Leupeptins; Mutation