Structural Basis for the Antiarrhythmic Blockade of a Potassium Channel with a Small Molecule

Authors

Yoshio Takemoto, The University Of Michigan
Diana P. Slough, Tufts University
Gretchen Meinke, Tufts University
Christopher Katnik, University of South Florida
Zachary A. Graziano, Tufts University
Bojjibabu Chidipi, University of South Florida
Michelle Reiser, University of South Florida
Mohammed M. Alhadidy, University of South Florida
Rafael Ramirez, University of Michigan
Oscar Salvador-Montañés, University of Michigan
Steven Ennis, The University Of Michigan
Guadalupe Guerrero-Serna, University of Michigan
Marian Haburcak, Brandeis University
Carl Diehl, Saromics Biostructures
Javier Cuevas, University of South FloridaFollow
Jose Jalife, University of Michigan
Andrew Bohm, Tufts University
Yu-Shan Lin, Tufts University
Sami F. Noujaim, University of South FloridaFollow

Document Type

Article

Publication Date

2018

Keywords

potassium inward rectifier, atrial fibrillation, IKACh

Digital Object Identifier (DOI)

https://doi.org/10.1096/fj.201700349R

Abstract

The acetylcholine-activated inward rectifier potassium current (I_KACh) is constitutively active in persistent atrial fibrillation (AF). We tested the hypothesis that the blocking of I_KACh with the small molecule chloroquine terminates persistent AF. We used a sheep model of tachypacing-induced, persistent AF, molecular modeling, electrophysiology, and structural biology approaches. The 50% inhibition/inhibitory concentration of I_KACh block with chloroquine, measured by patch clamp, was 1 µM. In optical mapping of sheep hearts with persistent AF, 1 µM chloroquine restored sinus rhythm. Molecular modeling suggested that chloroquine blocked the passage of a hydrated potassium ion through the intracellular domain of Kir3.1 (a molecular correlate of I_KACh) by interacting with residues D260 and F255, in proximity to I228, Q227, and L299. ¹H ¹⁵N heteronuclear single-quantum correlation of purified Kir3.1 intracellular domain confirmed the modeling results. F255, I228, Q227, and L299 underwent significant chemical-shift perturbations upon drug binding. We then crystallized and solved a 2.5 Å X-ray structure of Kir3.1 with F255A mutation. Modeling of chloroquine binding to the mutant channel suggested that the drug's binding to the pore becomes off centered, reducing its ability to block a hydrated potassium ion. Patch clamp validated the structural and modeling data, where the F255A and D260A mutations significantly reduced I_KACh block by chloroquine. With the use of numerical and structural biology approaches, we elucidated the details of how a small molecule could block an ion channel and exert antiarrhythmic effects. Chloroquine binds the I_KACh channel at a site formed by specific amino acids in the ion-permeation pathway, leading to decreased I_KACh and the subsequent termination of AF.— Takemoto, Y., Slough, D. P., Meinke, G., Katnik, C., Graziano, Z. A., Chidipi, B., Reiser, M., Alhadidy, M. M., Ramirez, R., Salvador-Montañés, O., Ennis, S., Guerrero-Serna, G., Haburcak, M., Diehl, C., Cuevas, J., Jalife, J., Bohm, A., Lin, Y.-S., Noujaim, S. F. Structural basis for the antiarrhythmic blockade of a potassium channel with a small molecule. FASEB J. 32, 1778–1793 (2018). www.fasebj.org

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

The FASEB Journal, v. 32, issue 4, p. 1778-1793

Scholar Commons Citation

Takemoto, Yoshio; Slough, Diana P.; Meinke, Gretchen; Katnik, Christopher; Graziano, Zachary A.; Chidipi, Bojjibabu; Reiser, Michelle; Alhadidy, Mohammed M.; Ramirez, Rafael; Salvador-Montañés, Oscar; Ennis, Steven; Guerrero-Serna, Guadalupe; Haburcak, Marian; Diehl, Carl; Cuevas, Javier; Jalife, Jose; Bohm, Andrew; Lin, Yu-Shan; and Noujaim, Sami F., "Structural Basis for the Antiarrhythmic Blockade of a Potassium Channel with a Small Molecule" (2018). Molecular Pharmacology & Physiology Faculty Publications. 71.
https://digitalcommons.usf.edu/mpp_facpub/71