Stoichiometry-dependent gating and structural pharmacology of cardiac GIRK1/4 channels
- 1St. Jude Children's Research Hospital
Abstract
Cardiac G protein-gated inwardly rectifying potassium-K+ (GIRK) channels, formed by GIRK1/4 heterotetramers or GIRK4 homotetramers, are crucial regulators of heart rate, and their dysfunction is associated with atrial fibrillation. Despite their therapeutic potential as anti-arrhythmic targets, development of selective GIRK modulators has been limited by an incomplete understanding of their structures, gating mechanisms, and pharmacology. Here, we report high-resolution structures of the GIRK4 homotetramer and of GIRK1/4 heterotetramers, revealing that they form in unexpected 1:3 and 2:2 assembly stoichiometries that we corroborate using cell-based single molecule microscopy. Electrophysiological assays and molecular dynamics simulations further show that incorporation of one or two GIRK1 subunits into GIRK4-containing channels progressively opens the helix bundle crossing (HBC) gate and increases basal channel activity. Additional structures of GIRK1/4 complexes with ML297, a small-molecule ligand selective for GIRK1-containing channels, reveal distinct GIRK1-centered intersubunit binding environments. Remarkably, ML297 inhibits GIRK1/4 channels with a 1:3 stoichiometry but potentiates channels with a 2:2 stoichiometry, establishing a direct link between subunit composition, ligand-binding environment, and pharmacological efficacy. Together, these findings provide a structural and mechanistic framework for the rational design of ligands with enhanced selectivity among cardiac and neuronal GIRK channel heterotetramers.
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BibTeX
@misc{wang2026stoichiometrydependent,
title = {{Stoichiometry-dependent gating and structural pharmacology of cardiac GIRK1/4 channels}},
author = {L. Wang and T. Kawano and A. Santa-Cruz and N. Parvaiz and A. Zorn and Y. Lu and M. Zaka and N. Aly and J. Pentikis and E. Dadiotis and K. W. Chan and M. Cui and L. D. Plant and D. E. Logothetis and G. Skiniotis},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.06.756879},
url = {https://www.biorxiv.org/content/10.64898/2026.10.06.756879v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Stoichiometry-dependent gating and structural pharmacology of cardiac GIRK1/4 channels
AU - L. Wang
AU - T. Kawano
AU - A. Santa-Cruz
AU - N. Parvaiz
AU - A. Zorn
AU - Y. Lu
AU - M. Zaka
AU - N. Aly
AU - J. Pentikis
AU - E. Dadiotis
AU - K. W. Chan
AU - M. Cui
AU - L. D. Plant
AU - D. E. Logothetis
AU - G. Skiniotis
PY - 2026
DA - 2026/10/06
PB - bioRxiv
DO - 10.64898/2026.10.06.756879
UR - https://www.biorxiv.org/content/10.64898/2026.10.06.756879v1
AB - Cardiac G protein-gated inwardly rectifying potassium-K+ (GIRK) channels, formed by GIRK1/4 heterotetramers or GIRK4 homotetramers, are crucial regulators of heart rate, and their dysfunction is associated with atrial fibrillation. Despite their therapeutic potential as anti-arrhythmic targets, development of selective GIRK modulators has been limited by an incomplete understanding of their structures, gating mechanisms, and pharmacology. Here, we report high-resolution structures of the GIRK4 homotetramer and of GIRK1/4 heterotetramers, revealing that they form in unexpected 1:3 and 2:2 assembly stoichiometries that we corroborate using cell-based single molecule microscopy. Electrophysiological assays and molecular dynamics simulations further show that incorporation of one or two GIRK1 subunits into GIRK4-containing channels progressively opens the helix bundle crossing (HBC) gate and increases basal channel activity. Additional structures of GIRK1/4 complexes with ML297, a small-molecule ligand selective for GIRK1-containing channels, reveal distinct GIRK1-centered intersubunit binding environments. Remarkably, ML297 inhibits GIRK1/4 channels with a 1:3 stoichiometry but potentiates channels with a 2:2 stoichiometry, establishing a direct link between subunit composition, ligand-binding environment, and pharmacological efficacy. Together, these findings provide a structural and mechanistic framework for the rational design of ligands with enhanced selectivity among cardiac and neuronal GIRK channel heterotetramers.
ER -