Identification of New Batrachotoxin-sensing Residues in Segment IIIS6 of the Sodium Channel

Du, Yuzhe; Garden, Daniel P.; Wang, Lingxin; Zhorov, Boris S.; Dong, Ke

doi:10.1074/jbc.m110.208496

Cited by 55 publications

(58 citation statements)

References 59 publications

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“…However, these toxins do not bind to the outer pore but instead to the inner pore (BTX) (48)(49)(50) or to other transmembrane helices (PTX-B) (47,51). Thus, although overall Na + channel structure in L. epinephelus likely is influenced by multiple prey toxins, we are confident that the P-loop replacements we discuss have been shaped by selection from TTX, because the outer pore is the target of TTX, and these functional mutations are at sites critical to TTX binding but uninvolved in BTX or PTX-B binding (47)(48)(49)(50)(51).…”

Section: Resultsmentioning

confidence: 99%

Constraint shapes convergence in tetrodotoxin-resistant sodium channels of snakes

Feldman

Brodie²,

Pfrender³

2012

Proc. Natl. Acad. Sci. U.S.A.

148

220

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Natural selection often produces convergent changes in unrelated lineages, but the degree to which such adaptations occur via predictable genetic paths is unknown. If only a limited subset of possible mutations is fixed in independent lineages, then it is clear that constraint in the production or function of molecular variants is an important determinant of adaptation. We demonstrate remarkably constrained convergence during the evolution of resistance to the lethal poison, tetrodotoxin, in six snake species representing three distinct lineages from around the globe. Resistance-conferring amino acid substitutions in a voltage-gated sodium channel, Na v 1.4, are clustered in only two regions of the protein, and a majority of the replacements are confined to the same three positions. The observed changes represent only a small fraction of the experimentally validated mutations known to increase Na v 1.4 resistance to tetrodotoxin. These results suggest that constraints resulting from functional tradeoffs between ion channel function and toxin resistance led to predictable patterns of evolutionary convergence at the molecular level. Our data are consistent with theoretical predictions and recent microcosm work that suggest a predictable path is followed during an adaptive walk along a mutational landscape, and that natural selection may be frequently constrained to produce similar genetic outcomes even when operating on independent lineages. coevolution | molecular evolution | pleiotropy

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Section: Resultsmentioning

confidence: 99%

Constraint shapes convergence in tetrodotoxin-resistant sodium channels of snakes

Feldman

Brodie²,

Pfrender³

2012

Proc. Natl. Acad. Sci. U.S.A.

148

220

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“…Mutational studies show that BTX binds in the inner pore, contacts the inner helices from all four repeats (Wang et al, 2006(Wang et al, , 2007a, and may adopt an ion-permeable "horseshoe" conformation within the channel as we recently proposed (Du et al, 2011a). In contrast, pyrethroids including deltamethrin are proposed to bind in the lipid-exposed interface between the linker-helix IIS4-S5, the outer helix IIS5, and the inner helix IIIS6 (O'Reilly et al, 2006;Du et al, 2009).…”

Section: Resultsmentioning

confidence: 80%

“…2A; Supplemental Table S2), that are critical for the action of pyrethroids (Du et al, 2009). In addition, we have shown that Gly 3i14 and Phe 3i16 are also critical for the action of BTX (Du et al, 2011a). To determine whether these residues are also critical for the action of BTG 502, we examined the effect of BTG 502 on these four mutant channels.…”

Section: Resultsmentioning

confidence: 99%

“…However, mutational studies identified BTX-sensing residues in the inner helices of all four domains, suggesting that BTX is directly exposed to the permeation pathway (Tikhonov and Zhorov, 2005b). More recent mutational and modeling studies have confirmed this prediction (Wang et al, 2006(Wang et al, , 2007aDu et al, 2011a). Studies of the mechanisms of insect resistance to pyrethroids led to the identification of pyrethroid-sensing residues in diverse regions of insect sodium channels (Soderlund, 2005;Davies et al, 2007;Dong, 2007).…”

Section: Introductionmentioning

confidence: 85%

“…These data have been used to construct a model of the sodium channel in which pyrethroids bind to a cavity formed by the linker-helix IIS4 -S5, the outer helix IIS5, and the inner helix IIIS6 at the interface between domains II and III (O'Reilly et al, 2006). Systematic site-directed mutagenesis of residues in IIIS6 revealed additional four residues that are important for the action of deltamethrin (Du et al, 2009), and two of them are also critical for the action of BTX (Du et al, 2011a). Despite this apparent overlap, the binding sites for BTX and pyrethroids in IIIS6 are distinct, involving opposite faces of the IIIS6 transmembrane helix (Du et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Batrachotoxin, Pyrethroids, and BTG 502 Share Overlapping Binding Sites on Insect Sodium Channels

Garden

Khambay

et al. 2011

Mol Pharmacol

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Batrachotoxin (BTX), a steroidal alkaloid, and pyrethroid insecticides bind to distinct but allosterically coupled receptor sites on voltage-gated sodium channels and cause persistent channel activation. BTX presumably binds in the inner pore, whereas pyrethroids are predicted to bind at the lipid-exposed cavity formed by the short intracellular linker-helix IIS4-S5 and transmembrane helices IIS5 and IIIS6. The alkylamide insecticide (2E,4E)-N-(1,2-dimethylpropyl)-6-(5-bromo-2-naphthalenyl)-2,4-hexadienamide (BTG 502) reduces sodium currents and antagonizes the action of BTX on cockroach sodium channels, suggesting that it also binds inside the pore. However, a pyrethroid-sensing residue, Phe 3i17 in IIIS6, which does not face the pore, is essential for the activity of BTG 502 but not for BTX. In this study, we found that three additional deltamethrin-sensing residues in IIIS6, Ile 3i12 , Gly 3i14 , and Phe 3i16 (the latter two are also BTX-sensing), and three BTX-sensing residues, Ser 3i15 and Leu 3i19 in IIIS6 and Phe 4i15 in IVS6, are all critical for BTG 502 action on cockroach sodium channels. Using these data as constraints, we constructed a BTG 502 binding model in which BTG 502 wraps around IIIS6, probably making direct contacts with all of the above residues on the opposite faces of the IIIS6 helix, except for the putative gating hinge Gly 3i14 . BTG 502 and its inactive analog DAP 1855 antagonize the action of deltamethrin. The antagonism was eliminated by mutations of Ser 3i15 , Phe 3i17 , Leu 3i19 , and Phe 4i15 but not by mutations of Ile 3i12 , Gly 3i14 , and Phe 3i16 . Our analysis revealed a unique mode of action of BTG 502, its receptor site overlapping with those of both BTX and deltamethrin.

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Advances in Targeting Voltage‐Gated Sodium Channels with Small Molecules

Nardi¹,

Damann²,

Hertrampf³

et al. 2012

ChemMedChem

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Blockade of voltage-gated sodium channels (VGSCs) has been used successfully in the clinic to enable control of pathological firing patterns that occur in conditions as diverse as chronic pain, epilepsy, and arrhythmias. Herein we review the state of the art in marketed sodium channel inhibitors, including a brief compendium of their binding sites and of the cellular and molecular biology of sodium channels. Despite the preferential action of this drug class toward over-excited cells, which significantly limits potential undesired side effects on other cells, the need to develop a second generation of sodium channel inhibitors to overcome their critical clinical shortcomings is apparent. Current approaches in drug discovery to deliver novel and truly innovative sodium channel inhibitors is next presented by surveying the most recent medicinal chemistry breakthroughs in the field of small molecules and developments in automated patch-clamp platforms. Various strategies aimed at identifying small molecules that target either particular isoforms of sodium channels involved in specific diseases or anomalous sodium channel currents, irrespective of the isoform by which they have been generated, are critically discussed and revised.

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Identification of New Batrachotoxin-sensing Residues in Segment IIIS6 of the Sodium Channel

Cited by 55 publications

References 59 publications

Constraint shapes convergence in tetrodotoxin-resistant sodium channels of snakes

Constraint shapes convergence in tetrodotoxin-resistant sodium channels of snakes

Batrachotoxin, Pyrethroids, and BTG 502 Share Overlapping Binding Sites on Insect Sodium Channels

Advances in Targeting Voltage‐Gated Sodium Channels with Small Molecules

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