Critical Molecular Determinants of Voltage-Gated Sodium Channel Sensitivity to μ-Conotoxins GIIIA/B

Cummins, Theodore R.; Aglieco, Fabio; Dib‐Hajj, Sulayman D.

doi:10.1124/mol.61.5.1192

Cited by 42 publications

(39 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Energetically dominant interactions seem to occur between basic residues of the CTXs and acidic residues of the outer charged rings within the lining of the Na v channel extracellular vestibule (Choudhary et al, 2007). Other studies show that the Na v channel isoform specificity is, at least partially, dictated by differences in the transmembrane segment 5-6 linker of repeat domain II (Li et al, 2001(Li et al, , 2003Cummins et al, 2002). Here, a novel approach, independent of identified couplings, allows us to deduce the orientation of a bound PIIIA with respect to the Na v channel.…”

Section: Introductionmentioning

confidence: 99%

Orientation of μ-Conotoxin PIIIA in a Sodium Channel Vestibule, Based on Voltage Dependence of Its Binding

McArthur¹,

Singh²,

O’Mara³

et al. 2011

Mol Pharmacol

View full text Add to dashboard Cite

Mutant cycle analysis has been used in previous studies to constrain possible docking orientations for various toxins. As an independent test of the bound orientation of -conotoxin PIIIA, a selectively targeted sodium channel pore blocker, we determined the contributions to binding voltage dependence of specific residues on the surface of the toxin. A change in the "apparent valence" (z␦) of the block, which is associated with a change of a specific toxin charge, reflects a change in the charge movement within the transmembrane electric field as the toxin binds. Toxin derivatives with charge-conserving mutations (R12K, R14K, and K17R) showed z␦ values similar to those of wild type (0.61 Ϯ 0.01, mean Ϯ S.E.M.). Chargechanging mutations produced a range of responses. Neutralizing substitutions for Arg14 and Lys17 showed the largest reductions in z␦ values, to 0.18 Ϯ 0.06 and 0.20 Ϯ 0.06, respectively, whereas unit charge-changing substitutions for Arg12, Ser13, and Arg20 gave intermediate values (0.24 Ϯ 0.07, 0.33 Ϯ 0.04, and 0.32 Ϯ 0.05), which suggests that each of these residues contributes to the dependence of binding on the transmembrane voltage. Two mutations, R2A and G6K, yielded no significant change in z␦. These observations suggest that the toxin binds with Arg2 and Gly6 facing the extracellular solution, and Arg14 and Lys17 positioned most deeply in the pore. In this study, we used molecular dynamics to simulate toxin docking and performed Poisson-Boltzmann calculations to estimate the changes in local electrostatic potential when individual charges were substituted on the toxin's surface. Consideration of two limiting possibilities suggests that most of the charge movement associated with toxin binding reflects sodium redistribution within the narrow part of the pore.

show abstract

Section: Introductionmentioning

confidence: 99%

Orientation of μ-Conotoxin PIIIA in a Sodium Channel Vestibule, Based on Voltage Dependence of Its Binding

McArthur¹,

Singh²,

O’Mara³

et al. 2011

Mol Pharmacol

View full text Add to dashboard Cite

show abstract

“…The discovery that mutations of the Na V 1.7 isoform resulted in human congenital insensitivity to pain, with affected patients being completely insensitive to painful stimuli and exhibiting no physiological abnormalities other than anosmia, was a validation of the indispensable role of Na V channels in pain [127][128][129] . Investigations using channel-selective venoms, bioinformatics methods, and in vitro high-throughput assays have all yielded valuable insight to the characteristics and distribution of Na V isoforms 30,32,130,131 .…”

Section: Potassium Channelsmentioning

confidence: 99%

“…GIIIA also exhibits different effects in different species, with the human Na V 1.4 isoform being resistant to GIIIA-mediated inhibition 130 despite the high potency of the toxin in the rat Na V 1.4 isoform 130 . In order to examine the effect of Na V 1.6, GIIIA is administered together with TIIIA, another conotoxin-derived peptide that inhibits Na V 1.1, 1.2, 1.3, and Na V 1.4 212 , but not Na V 1.6.…”

Section: Introductionmentioning

confidence: 99%

“…GIIIA was initially considered to be ineffective at neuronal Na V isoforms 130 . Further studies then determined GIIIA also inhibits Na V 1.1, Na V 1.2, and Na V 1.6, and is 30-fold more selective for Na V 1.4…”

Section: Introductionmentioning

confidence: 99%

“…GIIIA, a µ-conotoxin extracted from the venom of the cone snail Conus geographus, has known inhibitory effects on the skeletal muscle Na V isoform Na V 1.4 130 . GIIIA was initially considered to be ineffective at neuronal Na V isoforms 130 .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A pharmacological and transcriptomic approach to exploring novel pain targets

Yin¹

View full text Add to dashboard Cite

Ever since the discovery that mutations in the voltage-gated sodium channel 1.7 protein are responsible for human congenital insensitivity to pain, the voltage-gated sodium channel (Na V ) family of ion channels has been the subject of intense research with the hope of discovering novel analgesics. We now know that Na V 1.7 deletion in select neuronal populations yield different phenotypes, with the deletion of Na V 1.7 in all sensory neurons being successful at abolishing mechanical and heat-induced pain. However, it is rapidly becoming apparent that a number of pain syndromes are not modulated by Na V 1.7 at all, such as oxaliplatin-mediated neuropathy. It is particularly interesting to note that the loss of Na V 1.7 function is also associated with the selective inhibition of pain mediated by specific stimuli, such as that observed in burn-induced pain where Na V 1.7 gene knockout abolished thermal allodynia but did not affect mechanical allodynia. Accordingly, significant interests exist in delineating the contribution of other Na V isoforms in modality-specific pain pathways. Two other isoforms, Na V 1.6 and Na V 1.8, are now specifically implicated in some Na V 1.7-independent conditions such as oxaliplatin-induced cold allodynia. Such selective contributions of specific ion channel isoforms to pain highlight the need to discover other putative protein targets involved in mediating nociception.The aim of my work is therefore to discover selective molecular inhibitors of Na V 1.6 and Na V 1.8, to find useful cell models for peripheral nociceptors, to investigate the roles of Na V 1.6 and Na V 1.8 in an animal model of burn-induced pain, and to screen for putative new targets for analgesia in burn-related pain.Chapter 2 of this thesis describes activity-guided discovery of novel Na V 1.6 and Na V 1.8-modulting peptides from crude spider venoms. Crude venom from Poecilotheria metallica successfully reduced Na V 1.8-mediated voltage changes in HEK293-expressing cells. A new Na V 1.8-inhibitory peptide was sequenced from the venom and named Pme1a. However, Pme1a exhibited TRPV1 agonist activity and induced nocifensive behaviours, such as paw licking, after injection into the hind paws of mice, indicating the peptide was not a selective Na V 1.8 modulator and was unsuitable as a tool for Na V 1.8 investigation.iii With the unsuccessful exploration of spider venoms for new specific inhibitors, I then investigated in vitro cell models as tools to research specific nociceptor subtypes that express Na V 1.6 or Na V 1.8. In Chapter 3, I provide the first complete transcriptome of three common in vitro neuronal cell lines (SH-SY5Y, F-11, and ND7/23) to examine whether they were appropriate for investigating the functions of Na V 1.6 and Na V 1.8, and to identify if the cell lines resemble in vivo dorsal root ganglion (DRG) neuronal subclasses. The three cell lines examined all expressed proteins belonging to similar pathways and of similar proportions to native DRG neurons. However, they did not express any ce...

show abstract

Voltage‐Gated Sodium Channels in Peripheral Nociceptive Neurons as Targets for the Treatment of Pain

Cummins

2009

Peripheral Receptor Targets for Analgesia

View full text Add to dashboard Cite

Critical Molecular Determinants of Voltage-Gated Sodium Channel Sensitivity to μ-Conotoxins GIIIA/B

Cited by 42 publications

References 35 publications

Orientation of μ-Conotoxin PIIIA in a Sodium Channel Vestibule, Based on Voltage Dependence of Its Binding

Orientation of μ-Conotoxin PIIIA in a Sodium Channel Vestibule, Based on Voltage Dependence of Its Binding

A pharmacological and transcriptomic approach to exploring novel pain targets

Voltage‐Gated Sodium Channels in Peripheral Nociceptive Neurons as Targets for the Treatment of Pain

Contact Info

Product

Resources

About