Site and Mechanism of ML252 Inhibition of Kv7 Voltage-Gated Potassium Channels

A novel role of the antidepressant paroxetine in inhibiting neuronal Kv7/M channels to enhance neuronal excitability

The voltage-gated Kv7/KCNQ/M potassium channels exert inhibitory control over neuronal membrane excitability. The reduction of Kv7 channel function can improve neuronal excitability that defines the fundamental mechanism of learning and memory. This suggests that pharmacological inhibition of Kv7 channels may present a therapeutic strategy for cognitive improvement. Paroxetine, a selective serotonin reuptake inhibitor, is widely used in the treatment of various types of depression with reported improvements in memory and attention. However, the exact mechanism underlying cognitive improvement by paroxetine remains poorly understood. In this study, we demonstrate that paroxetine inhibits whole-cell Kv7.2/Kv7.3 channel currents in a concentration-dependent manner with an IC50 of 3.6 ± 0.2 μΜ. In single-channel recording assay, paroxetine significantly reduces the open probability of Kv7.2/Kv7.3 channels. Moreover, paroxetine exhibits an inhibition of the native M-current and an increase in the firing of action potentials in hippocampal neurons. Taken together, our findings unveil a novel role of the antidepressant paroxetine in inhibiting M-current, providing insights into its pharmacological effects on cognition enhancement.

Genetic features and pharmacological rescue of novel Kv7.2 variants in patients with epilepsy

BACKGROUND

Increasing evidence indicates a robust correlation between epilepsy and variants of the Kv7.2 (KCNQ2) channel, which is critically involved in directing M-currents and regulating neuronal excitability within the nervous system. With the advancement of next-generation sequencing, the identification of KCNQ2 variants has surged. Nonetheless, their functional impacts are still being determined, introducing uncertainty into the diagnostic process for affected families and potentially hindering their ability to participate in targeted precision medicine trials. This study aims to elucidate the pathogenicity of these novel variants and explore potential therapeutic interventions.

METHODS

Whole-cell patch-clamp recordings, western blotting, and immunofluorescent staining were performed to elucidate the functional consequences of the identified variants. Moreover, coimmunoprecipitation techniques were conducted to explore protein interactions, thus facilitating a deeper understanding of the underlying pathogenetic mechanisms contributing to the disease. Ultimately, the effects of pharmacological interventions were evaluated in vitro using the patch-clamp technique.

RESULTS

Herein, we identified 12 novel KCNQ2 variants, further expanding the mutational spectrum of KCNQ2. Our investigation revealed that one gain-of-function variant (p.L102V (c.304C>G)) and three loss-of-function variants (p.H328Q (c.984C>G), p.A336V (c.1007C>T) and p.D563Efs*22 (c.1688_1689insACTT)) had different impacts on the binding of calmodulin and phosphati-dylinositol-4,5-bisphosphate, potentially altering their localisation and protein stability. Furthermore, the application of ML213, unlike Retigabine and ICA-069673, led to a significant increase in the current of p.H328Q.

CONCLUSION

This study expanded the mutational spectrum of KCNQ2 and analysed the genetic and functional consequences, as well as the pharmacological rescue, of four de novo KCNQ2 variants. These findings offer valuable insights into the precise medicine of KCNQ2-related epilepsy.

The conductance of KCNQ2 and its pathogenic variants is determined by individual subunit gating

KCNQ2 channel subunits form part of the M-current and underlie one of the major potassium currents throughout the human nervous system, regulating resting membrane potentials, shaping action potentials, and impeding repetitive neuronal firing. However, how individual subunits within tetramers control channel functionality remains unresolved. Here, we investigate (i) whether opening of KCNQ2 channels requires a concerted step or can result from independent subunit activation and (ii) how individual subunits regulate gate opening and conductance. The E140R mutation in the S2 segment prevents activated voltage sensor conformations, but concatemeric constructs containing up to three E140R subunits retain KCNQ2-like currents. The underlying single-channel currents show subconductance levels resulting from limitations in inner gate dimensions, determined by the number of activated subunits and their spatial arrangement. Channel opening is allosteric and requires activation of only a single subunit, which can accentuate the influence of clinically relevant heterozygous mutations at threshold voltages.

Diving into the zebrafish brain: exploring neuroscience frontiers with genetic tools, imaging techniques, and behavioral insights

The zebrafish (Danio rerio) is increasingly used in neuroscience research. Zebrafish are relatively easy to maintain, and their high fecundity makes them suitable for high-throughput experiments. Their small, transparent embryos and larvae allow for easy microscopic imaging of the developing brain. Zebrafish also share a high degree of genetic similarity with humans, and are amenable to genetic manipulation techniques, such as gene knockdown, knockout, or knock-in, which allows researchers to study the role of specific genes relevant to human brain development, function, and disease. Zebrafish can also serve as a model for behavioral studies, including locomotion, learning, and social interactions. In this review, we present state-of-the-art methods to study the brain function in zebrafish, including genetic tools for labeling single neurons and neuronal circuits, live imaging of neural activity, synaptic dynamics and protein interactions in the zebrafish brain, optogenetic manipulation, and the use of virtual reality technology for behavioral testing. We highlight the potential of zebrafish for neuroscience research, especially regarding brain development, neuronal circuits, and genetic-based disorders and discuss its certain limitations as a model.