Dual receptor-sites reveal the structural basis for hyperactivation of sodium channels by poison-dart toxin batrachotoxin

Structural basis of human Nav1.5 gating mechanisms

Voltage-gated Nav1.5 channels are central to the generation and propagation of cardiac action potentials. Aberrations in their function are associated with a wide spectrum of cardiac diseases including arrhythmias and heart failure. Despite decades of progress in Nav1.5 biology, the lack of structural insights into intracellular regions has hampered our understanding of its gating mechanisms. Here, we present two cryo-EM structures of human Nav1.5 in open states, revealing sequential conformational changes in gating charges of the voltage-sensing domains (VSDs) and several intracellular regions. Despite the channel being in the open state, these structures show repositioning, but no dislodging of the IFM motif in the receptor site. Molecular dynamics analyses show our structures with CTD conduct Na+ ions. Notably, our structural findings highlight a dynamic C-terminal domain (CTD) and III-IV linker interaction, which regulates the conformation of VSDs and pore opening. Electrophysiological studies confirm that disrupting this interaction alters fast inactivation of Nav1.5. Together, our structure-function studies establish a foundation for understanding the gating mechanisms of Nav1.5 and the mechanisms underlying CTD-related channelopathies.

Drugs exhibit diverse binding modes and access routes in the Nav1.5 cardiac sodium channel pore

Small molecule inhibitors of the sodium channel are common pharmacological agents used to treat a variety of cardiac and nervous system pathologies. They act on the channel via binding within the pore to directly block the sodium conduction pathway and/or modulate the channel to favor a non-conductive state. Despite their abundant clinical use, we lack specific knowledge of their protein-drug interactions and the subtle variations between different compound structures. This study investigates the binding and accessibility of nine different compounds in the pore cavity of the Nav1.5 sodium channel using enhanced sampling simulations. We find that most compounds share a common location of pore binding-near the mouth of the DII-III fenestration-associated with the high number of aromatic residues in this region. In contrast, some other compounds prefer binding within the lateral fenestrations where they compete with lipids, rather than binding in the central cavity. Overall, our simulation results suggest that the drug binding within the pore is highly promiscuous, with most drugs having multiple low-affinity binding sites. Access to the pore interior via two out of four of the hydrophobic fenestrations is favorable for the majority of compounds. Our results indicate that the polyspecific and diffuse binding of inhibitors in the pore contributes to the varied nature of their inhibitory effects and can be exploited for future drug discovery and optimization.

Pioneering pain management with botulinum toxin type A: From anti-inflammation to regenerative therapies

In the present paper, a comprehensive review was conducted to evaluate the performance of botulinum toxin type A (BTX-A) in managing various types of pain, including myofascial, muscular temporomandibular joint pain, orofacial pain, chronic migraines, and more. Firstly, the mechanism of action and anti-inflammatory effects of BTX-A was introduced. Following this, recent advancements in BTX-A applications were discussed, with an emphasis on emerging combination therapies, regenerative medicine, and personalized treatment strategies. Unlike previous reviews, this study explored a broader spectrum of pain conditions and highlighted BTX-A's versatility and potential as a long-term, minimally invasive pain management option. Additionally, the importance of tailoring BTX-A treatment was emphasized through the integration of biomarkers, genetic factors, and optimized dosing regimens to enhance efficacy and minimize side effects. Novel combinations with regenerative therapies, such as stem cells and tissue engineering, were identified as promising avenues for joint and nerve repair, providing both symptomatic relief and tissue regeneration. Furthermore, digital health tools and artificial intelligence were suggested as innovative approaches to monitor treatment responses and optimize dosing protocols in real-time, advancing personalized pain management. Overall, this review underscores BTX-A's potential in comprehensive and patient-centered pain management and offers recommendations to guide future studies in optimizing BTX-A therapy.

Harnessing Deep Learning Methods for Voltage-Gated Ion Channel Drug Discovery

Voltage-gated ion channels (VGICs) are pivotal in regulating electrical activity in excitable cells and are critical pharmaceutical targets for treating many diseases including cardiac arrhythmia and neuropathic pain. Despite their significance, challenges such as achieving target selectivity persist in VGIC drug development. Recent progress in deep learning, particularly diffusion models, has enabled the computational design of protein binders for any clinically relevant protein based solely on its structure. These developments coincide with a surge in experimental structural data for VGICs, providing a rich foundation for computational design efforts. This review explores the recent advancements in computational protein design using deep learning and diffusion methods, focusing on their application in designing protein binders to modulate VGIC activity. We discuss the potential use of these methods to computationally design protein binders targeting different regions of VGICs, including the pore domain, voltage-sensing domains, and interface with auxiliary subunits. We provide a comprehensive overview of the different design scenarios, discuss key structural considerations, and address the practical challenges in developing VGIC-targeting protein binders. By exploring these innovative computational methods, we aim to provide a framework for developing novel strategies that could significantly advance VGIC pharmacology and lead to the discovery of effective and safe therapeutics.