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SLAS Discov. 2018 Sep;23(8):823-831. doi: 10.1177/2472555218763310. Epub 2018 Mar 13.

ΔF508-CFTR Modulator Screen Based on Cell Surface Targeting of a Chimeric Nucleotide Binding Domain 1 Reporter.

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1 Department of Medicine, University of California, San Francisco, CA, USA.
2 Department of Physiology and Groupe de Recherche Axe sur la Structure des Proteine (GRASP), McGill University, Montreal, QC, Canada.
3 Department of Pathology, University of California, San Francisco, CA, USA.
4 Department of Biochemistry, McGill University, Montreal, QC, Canada.
5 Department of Physiology, University of California, San Francisco, CA, USA.


The most common cystic fibrosis-causing mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is deletion of phenylalanine at residue 508 (∆F508). The ∆F508 mutation impairs folding of nucleotide binding domain 1 (NBD1) and interfacial interactions of NBD1 and the membrane spanning domains. Here, we report a domain-targeted screen to identify ∆F508-CFTR modulators that act on NBD1. A biochemical screen for ΔF508-NBD1 cell surface expression was done in Madin-Darby canine kidney cells expressing a chimeric reporter consisting of ΔF508-NBD1, the CD4 transmembrane domain, and an extracellular horseradish peroxidase (HRP) reporter. Using a luminescence readout of HRP activity, the screen was robust with a Z' factor of 0.7. The screening of ~20,000 synthetic small molecules allowed the identification of compounds from four chemical classes that increased ∆F508-NBD1 cell surface expression by up to 4-fold; for comparison, a 12-fold increased cell surface expression was found for a wild-type NBD1 chimera. While the compounds were inactive as correctors of full-length ΔF508-CFTR, several carboxamide-benzothiophenes had potentiator activity with low micromolar EC50. Interestingly, the potentiators did not activate G551D or wild-type CFTR. Our results provide a proof of concept for a cell-based NBD1 domain screen to identify ∆F508-CFTR modulators that target the NBD1 domain.


CFTR; cystic fibrosis; high-throughput screen; potentiator

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