Structural And Pharmacological Investigation Of A Human Voltage-gated Sodium Channel

Voltage-gated sodium(Nav)channels are important in the process of initiation and propagation of action potentials.Nav channels are able to selectively permeate sodium ions into cell membranes in response to membrane potential changes,causing depolarization processes,and are therefore the basis of electrical signaling in living organisms.There are nine isoforms of Nav channels in the human body,and their abnormal functions or mutations can lead to a series of serious diseases,such as epilepsy,arrhythmia,and erythromelalgia,etc.Therefore,Nav channels are also important targets for clinical anesthetics and disease treatment.Thus,the research on the structure and working mechanism of Nav channels is of great physiological significance and basic research value,and is also a hot spot and frontier in the field of basic research in life science.The working cycle of Nav channels consists of three main states: resting state,activated state and inactivated state.Due to the limitations of research methods and the characteristics of Nav channels,most of the reported structures of human Nav channels are in the inactivated state,and there is still a gap in the study of resting and open state sodium channels.Structural studies of resting and open sodium channels will help us to explain their complete work cycle at the molecular level and deepen our understanding of human electrical signaling.Nav1.7,encoded by SCN9 A in human,is mainly located in the dorsal root ganglia and plays crucial roles in pain transduction.Due to its physiological importance,Nav1.7 has been widely recognized as a potential target for developing non-addictive analgesics.Although significant advancement has been made in the structural elucidation of Nav1.7 in different conformations,rational design of isoform-selective analgesics targeting Nav1.7 is still hindered by lack of structural insights into the mode of action(MOA)of these Nav antagonists.Here,we reported structure-based engineering of a functional Nav1.7 variant that exhibits an essentially right-shifted voltage dependence of activation curves.Structural comparison of this variant with WT Nav1.7,where VSDI is in a fully downward state,reveals multimodal conformational changes in VSDI and VSDII that propagate to intracellular gating via crosstalk between adjacent segments.A conserved WNФФD motif(Ф for hydrophobic residues)was found on the S3 I segment to stabilize the downward conformation of VSDI.In addition,six representative drugs and lead compounds with different chemical backbones were selected in order to explore potentially druggable sites.We resolved the cryo EM structures of Nav1.7 in complexes with these drugs and proposed a new drug binding site nomenclature.In summary,our project provides a novel structure of partial resting state of Nav1.7,and 3D structural map for known drug-binding sites on Nav channels is summarized from the present and previous structures.