Defining the Kv2.1-syntaxin molecular interaction identifies a first-in-class small molecule neuroprotectant

Disrupting stroke-induced GAT-1-syntaxin1A interaction promotes functional recovery after stroke

Although stroke is a frequent cause of permanent disability, our ability to promote stroke recovery is limited. Here, we design a small-molecule stroke recovery promoting agent that works by dissociating γ-aminobutyric acid (GABA) transporter 1 (GAT-1) from syntaxin1A (Synt1A), a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein. Stroke induces an increase in GAT-1-Synt1A interaction in the subacute phase, a critical period for functional recovery. Uncoupling GAT-1-Synt1A reverses stroke-induced GAT-1 dysfunction and cortical excitability decline and enhances synaptic GABAergic inhibition and consequently cortical oscillations and network plasticity by facilitating the assembly of the SNARE complex at the synapse. Based on the molecular mechanism of GAT-1 binding to Synt1A, we design GAT-1-Synt1A blockers. Among them, ZLQ-3 exhibits the greatest potency. Intranasal use of ZLQ-3-1, a glycosylation product of ZLQ-3, substantially lessens impairments of sensorimotor and cognitive functions in rodent models. This compound, or its analogs, may serve as a promoting agent for stroke recovery.

Discovery of 2-Ethoxy-5-isobutyramido-N-1-substituted Benzamide Derivatives as Selective Kv2.1 Inhibitors with In Vivo Neuroprotective Effects

Kv2.1 is involved in regulating neuronal excitability and neuronal cell apoptosis, and inhibiting Kv2.1 is a potential strategy to prevent cell death and achieve neuroprotection in ischemic stroke. In this work, a series of novel benzamide derivatives were designed and synthesized as Kv2.1 inhibitors, and extensive structure-activity relationships led to highly potent and selective Kv2.1 inhibitors having IC50 values of 10-8 M. Among them, compound 80 (IC50 = 0.07 μM, selectivity >130 fold over other K+, Na+, and Ca2+ ion channels) was able to decrease the apoptosis of HEK293/Kv2.1 cells induced by H2O2. Furthermore, its anti-ischemic efficacy was demonstrated as it markedly reduced the infarct volume in MCAO rat model. Additionally, compound 80 possessed appropriate plasma PK parameters. It could serve as a probe to investigate Kv2.1 pathological functions and deserved to be further explored.

A peptidomimetic modulator of the CaV2.2 N-type calcium channel for chronic pain

Transmembrane Cav2.2 (N-type) voltage-gated calcium channels are genetically and pharmacologically validated, clinically relevant pain targets. Clinical block of Cav2.2 (e.g., with Prialt/Ziconotide) or indirect modulation [e.g., with gabapentinoids such as Gabapentin (GBP)] mitigates chronic pain but is encumbered by side effects and abuse liability. The cytosolic auxiliary subunit collapsin response mediator protein 2 (CRMP2) targets Cav2.2 to the sensory neuron membrane and regulates their function via an intrinsically disordered motif. A CRMP2-derived peptide (CBD3) uncouples the Cav2.2-CRMP2 interaction to inhibit calcium influx, transmitter release, and pain. We developed and applied a molecular dynamics approach to identify the A1R2 dipeptide in CBD3 as the anchoring Cav2.2 motif and designed pharmacophore models to screen 27 million compounds on the open-access server ZincPharmer. Of 200 curated hits, 77 compounds were assessed using depolarization-evoked calcium influx in rat dorsal root ganglion neurons. Nine small molecules were tested electrophysiologically, while one (CBD3063) was also evaluated biochemically and behaviorally. CBD3063 uncoupled Cav2.2 from CRMP2, reduced membrane Cav2.2 expression and Ca2+ currents, decreased neurotransmission, reduced fiber photometry-based calcium responses in response to mechanical stimulation, and reversed neuropathic and inflammatory pain across sexes in two different species without changes in sensory, sedative, depressive, and cognitive behaviors. CBD3063 is a selective, first-in-class, CRMP2-based peptidomimetic small molecule, which allosterically regulates Cav2.2 to achieve analgesia and pain relief without negative side effect profiles. In summary, CBD3063 could potentially be a more effective alternative to GBP for pain relief.

Regulation of neuronal excitation-transcription coupling by Kv2.1-induced clustering of somatic L-type Ca2+ channels at ER-PM junctions

In hippocampal neurons, gene expression is triggered by electrical activity and Ca²⁺ entry via L-type Cav1.2 channels in a process called excitation–transcription coupling. We identified a domain on the voltage-gated K⁺ channel Kv2.1 that promotes the clustering of L-type Cav1.2 channels at endoplasmic reticulum–plasma membrane junctions in the soma of neurons. Importantly, we discovered by disrupting this domain that the Kv2.1-mediated clustering of Cav1.2 at this somatic microdomain is critical for depolarization-induced excitation–transcription coupling.

In mammalian brain neurons, membrane depolarization leads to voltage-gated Ca²⁺ channel-mediated Ca²⁺ influx that triggers diverse cellular responses, including gene expression, in a process termed excitation–transcription coupling. Neuronal L-type Ca²⁺ channels, which have prominent populations on the soma and distal dendrites of hippocampal neurons, play a privileged role in excitation–transcription coupling. The voltage-gated K⁺ channel Kv2.1 organizes signaling complexes containing the L-type Ca²⁺ channel Cav1.2 at somatic endoplasmic reticulum–plasma membrane junctions. This leads to enhanced clustering of Cav1.2 channels, increasing their activity. However, the downstream consequences of the Kv2.1-mediated regulation of Cav1.2 localization and function on excitation–transcription coupling are not known. Here, we have identified a region between residues 478 to 486 of Kv2.1’s C terminus that mediates the Kv2.1-dependent clustering of Cav1.2. By disrupting this Ca²⁺ channel association domain with either mutations or with a cell-penetrating interfering peptide, we blocked the Kv2.1-mediated clustering of Cav1.2 at endoplasmic reticulum–plasma membrane junctions and the subsequent enhancement of its channel activity and somatic Ca²⁺ signals without affecting the clustering of Kv2.1. These interventions abolished the depolarization-induced and L-type Ca²⁺ channel-dependent phosphorylation of the transcription factor CREB and the subsequent expression of c-Fos in hippocampal neurons. Our findings support a model whereby the Kv2.1-Ca²⁺ channel association domain-mediated clustering of Cav1.2 channels imparts a mechanism to control somatic Ca²⁺ signals that couple neuronal excitation to gene expression.

Clenbuterol-sensitive delayed outward potassium currents in a cell model of spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by polyglutamine (polyQ) expansions in the androgen receptor (AR) gene. SBMA is characterized by selective dysfunction and degeneration of motor neurons in the brainstem and spinal cord through still unclear mechanisms in which ion channel modulation might play a central role as for other neurodegenerative diseases. The beta2-adrenergic agonist clenbuterol was observed to ameliorate the SBMA phenotype in mice and patient-derived myotubes. However, the underlying molecular mechanism has yet to be clarified. Here, we unveil that ionic current alterations induced by the expression of polyQ-expanded AR in motor neuron-derived MN-1 cells are attenuated by the administration of clenbuterol. Our combined electrophysiological and pharmacological approach allowed us to reveal that clenbuterol modifies delayed outward potassium currents. Overall, we demonstrated that the protection provided by clenbuterol restores the normal function through the modulation of K_V2-type outward potassium currents, possibly contributing to the protective effect on motor neuron toxicity in SBMA.

Lessons from Recent Advances in Ischemic Stroke Management and Targeting Kv2.1 for Neuroprotection

Achieving neuroprotection in ischemic stroke patients has been a multidecade medical challenge. Numerous clinical trials were discontinued in futility and many were terminated in response to deleterious treatment effects. Recently, however, several positive reports have generated the much-needed excitement surrounding stroke therapy. In this review, we describe the clinical studies that significantly expanded the time window of eligibility for patients to receive mechanical endovascular thrombectomy. We further summarize the results available thus far for nerinetide, a promising neuroprotective agent for stroke treatment. Lastly, we reflect upon aspects of these impactful trials in our own studies targeting the Kv2.1-mediated cell death pathway in neurons for neuroprotection. We argue that recent changes in the clinical landscape should be adapted by preclinical research in order to continue progressing toward the development of efficacious neuroprotective therapies for ischemic stroke.

The Redox Biology of Excitotoxic Processes: The NMDA Receptor, TOPA Quinone, and the Oxidative Liberation of Intracellular Zinc

This special issue of Frontiers in Neuroscience-Neurodegeneration celebrates the 50th anniversary of John Olney's seminal work introducing the concept of excitotoxicity as a mechanism for neuronal cell death. Since that time, fundamental research on the pathophysiological activation of glutamate receptors has played a central role in our understanding of excitotoxic cellular signaling pathways, leading to the discovery of many potential therapeutic targets in the treatment of acute or chronic/progressive neurodegenerative disorders. Importantly, excitotoxic signaling processes have been found repeatedly to be closely intertwined with oxidative cellular cascades. With this in mind, this review looks back at long-standing collaborative efforts by the authors linking cellular redox status and glutamate neurotoxicity, focusing first on the discovery of the redox modulatory site of the N-methyl-D-aspartate (NMDA) receptor, followed by the study of the oxidative conversion of 3,4-dihydroxyphenylalanine (DOPA) to the non-NMDA receptor agonist and neurotoxin 2,4,5-trihydroxyphenylalanine (TOPA) quinone. Finally, we summarize our work linking oxidative injury to the liberation of zinc from intracellular metal binding proteins, leading to the uncovering of a signaling mechanism connecting excitotoxicity with zinc-activated cell death-signaling cascades.

Targeted disruption of Kv2.1-VAPA association provides neuroprotection against ischemic stroke in mice by declustering Kv2.1 channels

Kv2.1 channels mediate cell death-enabling loss of cytosolic potassium in neurons following plasma membrane insertion at somatodendritic clusters. Overexpression of the carboxyl terminus (CT) of the cognate channel Kv2.2 is neuroprotective by disrupting Kv2.1 surface clusters. Here, we define a seven-amino acid declustering domain within Kv2.2 CT (DP-2) and demonstrate its neuroprotective efficacy in a murine ischemia-reperfusion model. TAT-DP-2, a membrane-permeable derivative, induces Kv2.1 surface cluster dispersal, prevents post-injurious pro-apoptotic potassium current enhancement, and is neuroprotective in vitro by disrupting the association of Kv2.1 with VAPA. TAT-DP-2 also induces Kv2.1 cluster dispersal in vivo in mice, reducing infarct size and improving long-term neurological function following stroke. We suggest that TAT-DP-2 induces Kv2.1 declustering by disrupting Kv2.1-VAPA association and scaffolding sites required for the membrane insertion of Kv2.1 channels following injury. We present the first evidence of targeted disruption of Kv2.1-VAPA association as a neuroprotective strategy following brain ischemia.