Cystic fibrosis drug ivacaftor stimulates CFTR channels at picomolar concentrations

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Abstract

The devastating inherited disease cystic fibrosis (CF) is caused by mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) anion channel. The recent approval of the CFTR potentiator drug ivacaftor (Vx-770) for the treatment of CF patients has marked the advent of causative CF therapy. Currently, thousands of patients are being treated with the drug, and its molecular mechanism of action is under intensive investigation. Here we determine the solubility profile and true stimulatory potency of Vx-770 towards wild-type (WT) and mutant human CFTR channels in cell-free patches of membrane. We find that its aqueous solubility is ~200-fold lower (~60 nanomolar), whereas the potency of its stimulatory effect is >100-fold higher, than reported, and is unexpectedly fully reversible. Strong, but greatly delayed, channel activation by picomolar Vx-770 identifies multiple sequential slow steps in the activation pathway. These findings provide solid guidelines for the design of in vitro studies using Vx-770.

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All data generated or analyzed during this study are included in the manuscript or can be visualized in the figures.

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László Csanády

Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary

For correspondence
csanady.laszlo@med.semmelweis-univ.hu

Competing interests
László Csanády, Reviewing editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0002-6547-5889
Beáta Töröcsik

Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary

Competing interests
No competing interests declared.

Funding

Cystic Fibrosis Foundation (CSANAD17G0)

László Csanády

Magyar Tudományos Akadémia (Lendület grant LP2017-14/2017)

László Csanády

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols of Semmelweis University (last approved 06-30-2016, expiration 06-30-2021).

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.