Biology subjects

Ghovanloo, M.-R.

Publications and source records attributed to Ghovanloo, M.-R..

6 recordsLinked to original sources

bioRxiv2026

Combinatorial logic of Nav channels in nociceptor excitability: Different degrees of synergy define distinct neuronal groups

Despite the genetic validation of voltage-gated sodium (Nav) channels as targets for pain therapy, single-channel subtype inhibition in clinical trials has yielded limited efficacy. Because Nav1.7 and Nav1.8 are thought to act in a coupled manner in ignition and subsequent regenerative, overshooting depolarization underlying the action potential of nociceptors, we utilized dynamic clamp, which permits precisely calibrated addition or subtraction of the current from any given channel, to systematically interrogate their combinatorial landscape. We demonstrate that nociceptor excitability is governed by highly non-linear biophysical rules. Partial, simultaneous attenuation of both conductances drives a supralinear collapse of action potential electrogenesis in sensory neurons. Unsupervised clustering reveals that this synergistic vulnerability is not a continuum, but varies in different neuronal subtypes: a population of sensory neurons experiences profound excitability suppression, whereas another population remains relatively resistant. These non-linear boundaries demonstrate that the efficacy of Nav current abrogation is fundamentally restricted by the underlying electrogenic architecture of the neuron, and provide a mechanistic blueprint for subtype-selective silencing.

neuroscience↗

bioRxiv2025

Targeted ubiquitination of NaV1.8 reduces sensory neuronal excitability

Chronic pain and addiction are a significant global health challenge. Voltage-gated sodium channel NaV1.8, a pivotal driver of pain signaling, is a clinically validated target for the development of novel, non-addictive pain therapeutics. Small molecule inhibitors against NaV1.8 have shown promise in acute pain indications, but large clinical effect sizes have not yet been demonstrated and efficacy in chronic pain indications are lacking. An alternative strategy to target NaV1.8 channels for analgesia is to reduce the number of channels that are present on nociceptor membranes. We generated a therapeutic heterobifunctional protein, named UbiquiNaV, that contains a NaV1.8-selective binding module and the catalytic subunit of the NEDD4 E3 Ubiquitin ligase. We show that UbiquiNav significantly reduces channel expression in the plasma membrane and reduces NaV1.8 currents in rodent sensory neurons. We demonstrate that UbiquiNaV is selective for NaV1.8 over other NaV isoforms and other components of the sensory neuronal electrogenisome. We then show that UbiquiNaV normalizes the distribution of NaV1.8 protein to distal axons, and that UbiquiNaV normalizes the neuronal hyperexcitability in in vitro models of inflammatory and chemotherapy-induced neuropathic pain. Our results serve as a blueprint for the design of therapeutics that leverage the selective ubiquitination of NaV1.8 channels for analgesia.

neuroscience↗

bioRxiv2023

Molecular pharmacology of selective NaV1.6 and dual NaV1.6 and NaV1.2 channel inhibitors that suppress excitatory neuronal activity ex vivo

Sodium channel inhibitors are used to treat neurological disorders of hyperexcitability. However, all currently available sodium channel targeting anti-seizure medications are non-selective among the NaV isoforms which potentially limits efficacy and therapeutic safety margins. XPC-7724 and XPC-5462 represent a new class of small molecule compounds. These compounds target inhibition of the NaV1.6 and NaV1.2 channels in excitatory pyramidal neurons and possess a molecular selectivity of >100 fold against NaV1.1 channels that are dominant in inhibitory cells. This profile will enable pharmacological dissection of the physiological roles of NaV1.2 and NaV1.6 and help to define the role of each channel in disease states. These compounds bind to and stabilize the inactivated-state of the channels, demonstrate higher potency with longer residency times, and slower off-rates than carbamazepine and phenytoin. These compounds possess cellular selectivity ex vivo in inhibiting action potential firing in cortical excitatory pyramidal neurons, whilst sparing fast spiking inhibitory interneurons. XPC-5462 also suppresses epileptiform activity in an ex vivo brain slice seizure model. This class of compounds provides a unique approach for treating neuronal excitability disorders by selectively down-regulating excitatory circuits. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=194 HEIGHT=200 SRC="FIGDIR/small/551643v2_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@70750corg.highwire.dtl.DTLVardef@114756aorg.highwire.dtl.DTLVardef@289009org.highwire.dtl.DTLVardef@1086e23_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2021

Inhibition of sodium conductance by cannabigerol contributes to a reduction of neuronal dorsal root ganglion excitability

Cannabigerol (CBG), a non-psychotropic phytocannabinoid, is a precursor for cannabis derivatives, {Delta}9-tetrahydrocannabinol and cannabidiol (CBD). Like CBD, CBG has been suggested as an analgesic. A previous study reported CBG (10 M) blocks voltage-gated sodium (Nav) currents in CNS neurons. However, the manner in which CBG inhibits Nav channels, and whether this effect contributes to CBGs potential analgesic behavior remain unknown. Genetic and functional studies have validated Nav1.7 as an opportune target for analgesic drug development. The efforts to develop therapeutic selective Nav1.7 blockers have been unsuccessful thus far, possibly due to issues in occupancy; drugs have been administered at concentrations many folds above IC50, resulting in loss of isoform-selectivity, and increasing off-target effects. We reasoned that an alternative approach could use compounds possessing 2 important properties: ultra-hydrophobicity and functional selectivity. Hydrophobicity could enhance absorption into neuronal cells especially with local administration. Functional selectivity could reduce likelihood of side-effects. As CBG is ultra-hydrophobic (cLogD=7.04), we sought to determine whether it also possesses functional selectivity against Nav channels that are expressed in dorsal root ganglion (DRG). We found that CBG is a ~10-fold state-dependent Nav inhibitor (KI-KR: ~2-20 M) with an average Hill-slope of ~2. We determined that at lower concentrations, CBG predominantly blocks sodium Gmax and slows recovery from inactivation; however, as concentration is increased, CBG also hyperpolarizes Nav inactivation curves. Our modeling and multielectrode array recordings suggest that CBG attenuates DRG excitability, which is likely linked with Nav inhibition. As most Nav1.7 channels are inactivated at DRG resting membrane potential, they are more likely to be inhibited by lower CBG concentrations, suggesting functional selectivity against Nav1.7 compared to other Navs (via Gmax block).

pharmacology and toxicology↗

bioRxiv2020

Mechanism and effects of the skeletal muscle Nav1.4 inhibition by cannabidiol

ABSTRACTCannabis sativa contains active constituents called phytocannabinoids. Some phytocannabinoids are psychotropic and others are not. The primary non-psychotropic phytocannabinoid is cannabidiol (CBD), which is proposed to be therapeutic against many conditions, including muscle spasms. Mechanisms have been proposed for the action of CBD on different systems, involving multiple targets, including the voltage-gated sodium channel (Nav) family, which are heavily implicated in many of the conditions CBD has been reported to relieve. In this study, we investigated the modulatory mechanism of CBD on Nav1.4. Based on previous results, we tested the hypothesis that CBD mechanism of action involves: 1) modulation of membrane elasticity, which indirectly contributes to Nav inhibition; and 2) physical block of the Nav pore. We first performed molecular dynamic (MD) simulations to visualize CBD effects and localization inside the membrane, and then performed NMR to verify the MD results, showing CBD localizes below membrane headgroups. Then, we performed a gramicidin-based fluorescence (GFA) assay that showed CBD alters membrane elasticity. Next, we used site-directed mutagenesis in (F1586A) and around (WWWW) the Nav1.4 pore. Removing the local anesthetic binding site with F1586A reduced CBD block of INa. Occluding the fenestrations with WWWW blocked CBD access from the membrane into the Nav1.4 pore. However, stabilization of inactivation, via CBD-induced changes in membrane elasticity persisted, in WWWW. To investigate the potential therapeutic value of CBD against some Nav1.4 channelopathies, we used a pathogenic variant of Nav1.4, P1158S, known to cause myotonia and periodic paralysis. We found CBD reduces excitability in both wild-type and the mixed myotonia/periodic paralysis variant. Our in-vitro/in-silico results suggest that CBD may have therapeutic value against myotonia. Because Nav1.4 is crucial to skeletal muscle contraction, we used rat diaphragm myography and found the presence of saturating levels of CBD reduces skeletal muscle contraction.SUMMARY We used multidisciplinary approaches to show the mechanism and pathway by which CBD inhibits the skeletal muscle, Nav1.4. Our results suggest CBD modulates membrane elasticity and directly interacts with Nav1.4 within its pore.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biophysics↗

bioRxiv2017

A Mixed Periodic Paralysis & Myotonia Mutant, P1158S, Imparts pH Sensitivity in Skeletal Muscle Voltage-gated Sodium Channels

Skeletal muscle channelopathies, many of which are inherited as autosomal dominant mutations, include both myotonia and periodic paralysis. Myotonia is defined by a delayed relaxation after muscular contraction, whereas periodic paralysis is defined by episodic attacks of weakness. One sub-type of periodic paralysis, known as hypokalemic periodic paralysis (hypoPP), is associated with low potassium levels. Interestingly, the P1158S missense mutant, located in the third domain S4-S5 linker of the skeletal muscle voltage-gated sodium channel, Nav1.4, has been implicated in causing both myotonia and hypoPP. A common trigger for these conditions is physical activity. We previously reported that Nav1.4 is relatively insensitive to changes in extracellular pH compared to Nav1.2 and Nav1.5. Given that intense exercise is often accompanied by blood acidosis, we decided to test whether changes in pH would push gating in P1158S towards either phenotype. Our results indicate that, unlike in WT Nav1.4, low pH depolarizes the voltage-dependence of activation and steady-state fast inactivation, decreases current density, and increases late currents in P1185S. Thus, P1185S turns the normally pH-insensitive Nav1.4 into a proton-sensitive channel. Using action potential modeling we also predict a pH-to-phenotype correlation in patients with P1158S. We conclude that activities which alter blood pH may trigger myotonia or periodic paralysis in P1158S patients.\n\nSIGNIFICANCE STATEMENTVoltage-gated sodium channels (Nav) contribute to the physiology and pathophysiology of electrical signaling in excitable cells. Nav subtypes are expressed in a tissue-specific manner, thus they respond differently to physiological modulators. For instance, the cardiac subtype, Nav1.5, can be modified by changes in blood pH; however, the skeletal muscle subtype, Nav1.4, is mostly pH-insensitive. Nav1.4 mutants can mostly cause either hyper-or hypo-excitability in skeletal muscles, leading to conditions such as myotonia or periodic paralysis. P1158S uniquely causes both phenotypes. This study investigates pH-sensitivity in P1158S, and describes how physiological pH changes can push P1158S to cause myotonia and periodic paralysis.

biophysics↗