VU0810464, a non‐urea G protein‐gated inwardly rectifying K⁺ (K_ir3/GIRK) channel activator, exhibits enhanced selectivity for neuronal K_ir3 channels and reduces stress‐induced hyperthermia in mice

Abstract

Background and Purpose G protein‐gated inwardly rectifying K+ (Kir3) channels moderate the activity of excitable cells and have been implicated in neurological disorders and cardiac arrhythmias. Most neuronal Kir3 channels consist of Kir3.1 and Kir3.2 subtypes, while cardiac Kir3 channels consist of Kir3.1 and Kir3.4 subtypes. Previously, we identified a family of urea‐containing Kir3 channel activators, but these molecules exhibit suboptimal pharmacokinetic properties and modest selectivity for Kir3.1/3.2 relative to Kir3.1/3.4 channels. Here, we characterize a non‐urea activator, VU0810464, which displays nanomolar potency as a Kir3.1/3.2 activator, improved selectivity for neuronal Kir3 channels, and improved brain penetration. Experimental Approach We used whole‐cell electrophysiology to measure the efficacy and potency of VU0810464 in neurons and the selectivity of VU0810464 for neuronal and cardiac Kir3 channel subtypes. We tested VU0810464 in vivo in stress‐induced hyperthermia and elevated plus maze paradigms. Parallel studies with ML297, the prototypical activator of Kir3.1‐containing Kir3 channels, were performed to permit direct comparisons. Key Results VU0810464 and ML297 exhibited comparable efficacy and potency as neuronal Kir3 channel activators, but VU0810464 was more selective for neuronal Kir3 channels. VU0810464, like ML297, reduced stress‐induced hyperthermia in a Kir3‐dependent manner in mice. ML297, but not VU0810464, decreased anxiety‐related behaviour as assessed with the elevated plus maze test. Conclusion and Implications VU0810464 represents a new class of Kir3 channel activator with enhanced selectivity for Kir3.1/3.2 channels. VU0810464 may be useful for examining Kir3.1/3.2 channel contributions to complex behaviours and for probing the potential of Kir3 channel‐dependent manipulations to treat neurological disorders.

Next-generation inward rectifier potassium channel modulators: discovery and molecular pharmacology

“…Since its discovery, ML297 and other more recently discovered GIRK activators have been used by a number of groups to probe the function of GIRK channels in isolated cells, tissues, and in vivo. These studies include demonstration that pharmacologically increasing the activity of GIRK channels can produce efficacy rodent models of numerous disorders: anti-seizure (88,94,95), anxiolytic (90,96), anti-nociceptive (97,98), facilitation of conditioned fear extinction (93), promotion of non-REM sleep (99), and rescue of amyloid-b-evoked deficits in hippocampal function (100,101). These tools have also been used extensively to probe GIRK's role in wide variety of systems (102)(103)(104)(105)(106)(107)(108)(109)(110)(111).…”

Characterization of VU0468554, a New Selective Inhibitor of Cardiac G Protein–Gated Inwardly Rectifying K+ Channels

“…Hippocampal neuron culture. Primary cultures of hippocampal neurons were prepared as described (Vo et al, 2019). Briefly, extracted hippocampi from neonatal (P0-4) pups were placed into an ice-cold modified Hank's Balanced Salt Solution (MilliporeSigma) (in mM): 3 HEPES-NaOH (pH 7.1), kynurenic acid/12 Mg 2 SO 4 , and 5.5 D-glucose.…”

“…Electrophysiology. Electrophysiological recordings were performed as described (Vo et al, 2019). In brief, transfected HEK cells, pyramidal-shaped, hippocampal neurons (capacitances between 80 and 200 pF), or thin, striated SAN cells (capacitances between 15 and 40 pF), were transferred to a low-K + bath solution consisting of (in mM): 130 NaCl, 5.4 KCl, 1 CaCl 2 , 1 MgCl 2 , 5.5 D-glucose, and 5 HEPES/NaOH (pH 7.4).…”

Screening Technologies for Inward Rectifier Potassium Channels: Discovery of New Blockers and Activators

“…50,51 Recently, nonurea GIRK channel openers, including VU0810464, have been developed that show greater Kir3.1/3.2 channel selectivity. 52 Accordingly, VU0810464 is selective in activating GIRK channels in neurons but not cardiomyocytes. 52…”

“…52 Accordingly, VU0810464 is selective in activating GIRK channels in neurons but not cardiomyocytes. 52…”