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Proc Natl Acad Sci U S A. 2019 Dec 17;116(51):26008-26019. doi: 10.1073/pnas.1913929116. Epub 2019 Dec 3.

TRPA1 modulation by piperidine carboxamides suggests an evolutionarily conserved binding site and gating mechanism.

Author information

1
Biochemical and Cellular Pharmacology, Genentech, Inc., South San Francisco, CA 94080.
2
Institute for Computational Molecular Science, Department of Chemistry, Temple University, Philadelphia, PA 19122; egianti@temple.edu vincenzo.carnevale@temple.edu chenj144@gene.com.
3
Discovery Chemistry, Genentech, Inc., South San Francisco, CA 94080.
4
Charles River, CM19 5TR Harlow, Essex, United Kingdom.
5
Ion Channel Group, Evotec AG, 22419 Hamburg, Germany.
6
Neuroscience, Genentech, Inc., South San Francisco, CA 94080.
7
Institute for Computational Molecular Science, Department of Chemistry, Temple University, Philadelphia, PA 19122.
8
Biochemical and Cellular Pharmacology, Genentech, Inc., South San Francisco, CA 94080; egianti@temple.edu vincenzo.carnevale@temple.edu chenj144@gene.com.

Abstract

The transient receptor potential ankyrin 1 (TRPA1) channel functions as an irritant sensor and is a therapeutic target for treating pain, itch, and respiratory diseases. As a ligand-gated channel, TRPA1 can be activated by electrophilic compounds such as allyl isothiocyanate (AITC) through covalent modification or activated by noncovalent agonists through ligand binding. However, how covalent modification leads to channel opening and, importantly, how noncovalent binding activates TRPA1 are not well-understood. Here we report a class of piperidine carboxamides (PIPCs) as potent, noncovalent agonists of human TRPA1. Based on their species-specific effects on human and rat channels, we identified residues critical for channel activation; we then generated binding modes for TRPA1-PIPC interactions using structural modeling, molecular docking, and mutational analysis. We show that PIPCs bind to a hydrophobic site located at the interface of the pore helix 1 (PH1) and S5 and S6 transmembrane segments. Interestingly, this binding site overlaps with that of known allosteric modulators, such as A-967079 and propofol. Similar binding sites, involving π-helix rearrangements on S6, have been recently reported for other TRP channels, suggesting an evolutionarily conserved mechanism. Finally, we show that for PIPC analogs, predictions from computational modeling are consistent with experimental structure-activity studies, thereby suggesting strategies for rational drug design.

KEYWORDS:

TRPA1; agonist; binding; gating

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