Unveiling G protein-coupled inwardly-rectifying potassium channel 4 (GIRK4) inverse agonists: A novel simulation-driven approach leveraging cellular ion flow coupled with chemometrics and protein conformational dynamics

GIRK channels are crucial in regulating cardiac excitability and present promising therapeutic targets. Notably, the genetic absence of GIRK4 prevents atrial fibrillation (AF) in knockout mice, yet research on specific GIRK4 modulators is limited. Addressing the challenges posed by GIRK4's intrinsic constitutive activity, we hypothesize that a GIRK inverse agonist unlike the traditional antagonist can actively downregulate the channel activity alongside reduction of the aberrant basal signaling which can translate to enhanced therapeutic efficacy. A multilayered computational pipeline involving interpretable QSAR models, molecular docking, ADMET analysis and extensive membrane-bound molecular dynamics simulations [MDS] to screen potential candidates from DrugBank database. Extensive post-MDS analyses coupled with computational electrophysiology, revealed that DB02814 (3'-Deazo-Thiamin Diphosphate) can induce and stabilize a distinct inactive GIRK4 conformation, characterized by specific rearrangements in the inner transmembrane helices and the intracellular gate, which significantly reduces simulated potassium ion flux even under basal conditions. This robust in silico evidence strongly prioritizes DB02814 in pursuit of GIRK4 inverse agonist warranting further in vitro and in vivo validations. These findings provide a compelling foundation for the development of a new class of anti-arrhythmic agents directly targeting constitutive GIRK4 activity in AF.