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Unplugging lateral fenestrations of NALCN reveals a hidden drug binding site within the pore region
Schott, Katharina Usher, Samuel George Serra, Oscar Carnevale, Vincenzo Pless, Stephan Alexander Chua, Han Chow
Schott, Katharina
Usher, Samuel George
Serra, Oscar
Carnevale, Vincenzo
Pless, Stephan Alexander
Chua, Han Chow
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Journal article
Date
2024-05-24
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Biology
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https://doi.org/10.1073/pnas.2401591121
Abstract
The sodium (Na+) leak channel (NALCN) is a member of the four-domain voltage-gatedcation channel family that includes the prototypical voltage-gated sodium and calciumchannels (NaVs and CaVs, respectively). Unlike NaVs and CaVs, which have four lateralfenestrations that serve as routes for lipophilic compounds to enter the central cavityto modulate channel function, NALCN has bulky residues (W311, L588, M1145, andY1436) that block these openings. Structural data suggest that occluded fenestrationsunderlie the pharmacological resistance of NALCN, but functional evidence is lack-ing. To test this hypothesis, we unplugged the fenestrations of NALCN by substitut-ing the four aforementioned residues with alanine (AAAA) and compared the effectsof NaV, Ca V, and NALCN blockers on both wild-type (WT) and AAAA channels.Most compounds behaved in a similar manner on both channels, but phenytoin and2-aminoethoxydiphenyl borate (2-APB) elicited additional, distinct responses on AAAAchannels. Further experiments using single alanine mutants revealed that phenytoin and2- APB enter the inner cavity through distinct fenestrations, implying structural spec-ificity to their modes of access. Using a combination of computational and functionalapproaches, we identified amino acid residues critical for 2-APB activity, supportingthe existence of drug binding site(s) within the pore region. Intrigued by the activity of2-APB and its analogues, we tested compounds containing the diphenylmethane/aminemoiety on WT channels. We identified clinically used drugs that exhibited diverse activ-ity, thus expanding the pharmacological toolbox for NALCN. While the low potenciesof active compounds reiterate the pharmacological resistance of NALCN, our findingslay the foundation for rational drug design to develop NALCN modulators with refinedproperties.
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Citation
K. Schott,S.G. Usher,O. Serra,V. Carnevale,S.A. Pless, & H.C. Chua, Unplugging lateral fenestrations of NALCN reveals a hidden drug binding site within the pore region, Proc. Natl. Acad. Sci. U.S.A. 121 (22) e2401591121, https://doi.org/10.1073/pnas.2401591121 (2024). ]
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Proceedings of the National Academy of Sciences
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Proceedings of the National Academy of Sciences of the United States of America, Vol. 121, Iss. 22
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