Jian Huang

Voltage-gated sodium (Na_v) channels are key targets of various venomous toxins. Deciphering the binding poses and mechanisms of action of representative toxins will help to dissect the functional mechanism of the channels and facilitate therapeutic development targeting Na_v channels^1,2. Here we present cryo-electron microscopy (cryo-EM) structures of distinct binding poses of three agonistic peptide toxins on the human Na_v1.6–β1 channel complex. The globular β-scorpion toxin Cn2 nestles between the extracellular segment of voltage-sensing domain (VSD) in the second repeat of the Na_v1.6 core α-unit (VSD_II) and the pore extracellular loops in the third repeat of the Na_v1.6 core α-unit (ECL_III), where it is stabilized by interactions with both protein regions and the branched N1372-glycan. Cone snail ι-conotoxin RXIA adopts an elongated conformation, spanning VSD_I and VSD_IV to wrap around the shoulder of the pore domain (PD). The bullet ant-derived toxin δ-paraponeritoxin-Pc1a exists as a transmembrane helix that stands between VSD_II and PD_III. Our findings, corroborated by functional characterizations, illustrate the diversity in peptide toxin binding poses and mechanisms of action, link stabilization of the up state of VSD_I or VSD_II to channel activation, and provide clues to the rational design of selective Na_v channel modulators.

Pain is an unpleasant but essential sensory experience that serves as a protective mechanism, yet it can also manifest maladaptively in a wide range of pathological conditions. Current analgesic strategies rely heavily on opioid medications and non-steroidal anti-inflammatory drugs (NSAIDs); however, concerns regarding addiction, tolerance, and dose-limiting adverse effects highlight the urgent need for safer and more effective therapeutics. Voltage-gated sodium (Na_v) channels, which govern the initiation and propagation of action potentials, have emerged as promising targets for mechanism-based analgesic development. In particular, the Na_v1.7–Na_v1.9 subtypes have attracted substantial interest owing to their enrichment in the peripheral nervous system—despite broader expression elsewhere—and their central roles in nociception, offering the potential for non-addictive, subtype-selective pain modulation. This review summarizes the physiological roles of these channels in nociception, examines how disease-associated mutations shape pain phenotypes, and highlights recent advances in drug discovery targeting Na_v1.7 and Na_v1.8. The recent FDA approval of VX-548 (suzetrigine), a first-in-class and highly selective Na_v1.8 inhibitor, marks a major milestone that validates peripheral Na_v channels as clinically actionable targets for analgesia. We also discuss the remaining challenges and emerging opportunities in the pursuit of next-generation, mechanism-informed analgesics.

Strategies to stimulate dendritic cell (DC) activity, such as ex vivo generation and priming of DC vaccines, have been explored as cancer immunotherapies owing to their potential to elicit antitumor T cell responses. Despite decades of research, the success of DC vaccines has been limited, potentially because of unidentified tolerance-enforcing mechanisms. Here we show that GM-CSF–IL-4-induced differentiating DCs express ALDH1A2 and produce retinoic acid, inhibiting DC maturation. Genetic knockout of Aldh1a2 releases this natural brake and enhances DC function. We further develop an ALDH1A2 inhibitor with high potency, favorable drug-like properties and no evidence of off-target effects. Treatment with this inhibitor promotes DC activity, which in turn enhances antigen-specific T cell responses, improving the efficacy of DC vaccines. Our study demonstrates the unique role of the ALDH1A2–retinoic acid axis in regulating DC functions and further presents a new small-molecule inhibitor of ALDH1A2 as a potential immunotherapeutic agent for cancer.

Human M-channels, primarily assembled by heteromeric KCNQ2/KCNQ3 subunits, are critical regulators of neuronal excitability, and loss-of-function mutations in either subunit are linked to epileptic disorders. Yet, the molecular mechanisms underlying heteromeric assembly, gating, and pharmacological modulation have remained largely elusive. Here, we present high-resolution cryo-EM structures of human M-channels in apo and activator-bound states, revealing a dominant asymmetric 3:1 and a minor staggered 2:2 stoichiometry of KCNQ2 to KCNQ3, with consistent ratios across datasets. We further examine the mechanisms of action of two distinct modulators: ICA-110381 selectively engages and stabilizes activated KCNQ2 voltage sensors, whereas XEN1101 occupies pore fenestrations and promotes channel opening through a PIP2-assisted cooperative gating process. Electrophysiological analyses corroborate these observations, establishing the basis for subtype-selective modulation, cooperative gating, and KCNQ3-driven low-voltage activation. Together, our findings provide a foundation for interpreting pathogenic mutations and advancing the rational design of next-generation antiepileptic therapeutics targeting the M-channels.

Almost all the reported cryo-EM structures of eukaryotic voltage-gated sodium (Nav) channels, including those of human Nav1.1-Nav1.8, represent various inactivated states that are characteristic of a non-conductive pore domain (PD) surrounded by voltage-sensing domains (VSDs) in varying up conformations. To capture an open-state Navstructure, we treated purified human Nav1.7 with a natural neurotoxin veratridine (VTD) and solved its cryo-EM structures. Two VTD-bound Nav1.7 complexes were obtained. One, with VTD inserted in the IFM-binding corner (site I), resembles other inactivated structures. The other, wherein VTD traverses the central cavity (site C), represents an activated conformation with the constriction diameter of 8.2 Å at the intracellular gate. Structural analysis reveals the mechanism of action of VTD’s bimodal modulation of Nav channels. More importantly, structural comparison between the open and inactivated states provides advanced molecular insight into the fast inactivation process.

Voltage-gated sodium channels underpin electrical signaling in sensory neurons. Their activity is an essential element in the vast majority of pain conditions, making them significant drug targets. Sensory neuron sodium channels play roles not only in afferent signaling but also in a range of efferent regulatory mechanisms. Side effects through actions on other cell types and efferent signaling are thus important issues to address during analgesic drug development. As an example, the human genetic evidence for Na_V1.7 as an ideal pain target contrasts with the side effects of Na_V1.7 antagonists. In this review, we describe the history and progress toward the development of useful analgesic drugs and the renewed focus on Na_V1.8 as a key target in pain treatment. Na_V1.8 antagonists alone or in combination with other analgesics are likely to provide new opportunities for pain relief for the vast number of people (about 33% of the population) impacted by chronic pain, particularly present in aging populations.

Voltage-gated ion channels (VGICs), including those for Na⁺, Ca²⁺ and K⁺, selectively permeate ions across the cell membrane in response to changes in membrane potential, thus participating in physiological processes involving electrical signalling, such as neurotransmission, muscle contraction and hormone secretion. Aberrant function or dysregulation of VGICs is associated with a diversity of neurological, psychiatric, cardiovascular and muscular disorders, and approximately 10% of FDA-approved drugs directly target VGICs. Understanding the structure–function relationship of VGICs is crucial for our comprehension of their working mechanisms and role in diseases. In this Review, we discuss how advances in single-particle cryo-electron microscopy have afforded unprecedented structural insights into VGICs, especially on their interactions with clinical and investigational drugs. We present a comprehensive overview of the recent advances in the structural biology of VGICs, with a focus on how prototypical drugs and toxins modulate VGIC activities. We explore how these structures elucidate the molecular basis for drug actions, reveal novel pharmacological sites, and provide critical clues to future drug discovery.