Positive and Negative Allosteric Modulation of an α1β3γ2 γ-Aminobutyric Acid Type A (GABAA) Receptor by Binding to a Site in the Transmembrane Domain at the γ+-β− Interface

Jayakar, Selwyn S.; Zhou, Xiaojuan; Savechenkov, Pavel Y.; Chiara, David C.; Desai, Rushil; Bruzik, Karol S.; Miller, Keith W.; Cohen, Jonathan B.

doi:10.1074/jbc.m115.672006

Cited by 29 publications

(38 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While α1L232 has not been photolabeled by anesthetic derivatives, β3L231 was photolabeled by a convulsant barbiturate 35 . Our current SCAMP results indicate that α1L232C is protected by etomidate, confirming an earlier study using higher drug concentrations 21 .…”

Section: Discussionmentioning

confidence: 99%

Tryptophan and Cysteine Mutations in M1 Helices of α1β3γ2L γ-Aminobutyric Acid Type A Receptors Indicate Distinct Intersubunit Sites for Four Intravenous Anesthetics and One Orphan Site

Nourmahnad

Stern

Hotta³

et al. 2016

Anesthesiology

View full text Add to dashboard Cite

Background γ-Aminobutyric acid type A (GABAA) receptors mediate important effects of intravenous general anesthetics. Photolabel derivatives of etomidate, propofol, barbiturates, and a neurosteroid get incorporated in GABAA receptor transmembrane helices M1 and M3 adjacent to intersubunit pockets. However, photolabels have not been consistently targeted at heteromeric αβγ receptors and do not form adducts with all contact residues. Complementary approaches may further define anesthetic sites in typical GABAA receptors. Methods Two mutation-based strategies, substituted tryptophan sensitivity and substituted cysteine modification–protection, combined with voltage-clamp electrophysiology in Xenopus oocytes, were used to evaluate interactions between four intravenous anesthetics and six amino acids in M1 helices of α1, β3, and γ2L GABAA receptor subunits: two photolabeled residues, α1M236 and β3M227, and their homologs. Results Tryptophan substitutions at α1M236 and positional homologs β3L231 and γ2L246 all caused spontaneous channel gating and reduced γ-aminobutyric acid EC50. Substituted cysteine modification experiments indicated etomidate protection at α1L232C and α1M236C, R-5-allyl-1-methyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid protection at β3M227C and β3L231C, and propofol protection at α1M236C and β3M227C. No alphaxalone protection was evident at the residues the authors explored, and none of the tested anesthetics protected γ2I242C or γ2L246C. Conclusions All five intersubunit transmembrane pockets of GABAA receptors display similar allosteric linkage to ion channel gating. Substituted cysteine modification and protection results were fully concordant with anesthetic photolabeling at α1M236 and β3M227 and revealed overlapping noncongruent sites for etomidate and propofol in β+–α– interfaces and R-5-allyl-1-methyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid and propofol in α+–β– and γ+–β– interfaces. The authors’ results identify the α+–γ– transmembrane interface as a potentially unique orphan modulator site.

show abstract

Section: Discussionmentioning

confidence: 99%

Tryptophan and Cysteine Mutations in M1 Helices of α1β3γ2L γ-Aminobutyric Acid Type A Receptors Indicate Distinct Intersubunit Sites for Four Intravenous Anesthetics and One Orphan Site

Nourmahnad

Stern

Hotta³

et al. 2016

Anesthesiology

View full text Add to dashboard Cite

show abstract

“…Sites where low affinity anesthetics act in heteromeric GABA A Rs are largely unmapped, but there is evidence that some bind in the inter-subunit pockets where potent IV drugs act (51,71). These approaches are also being applied to map inhibitory (convulsant) sites on GABA A Rs (72). …”

Section: Discussionmentioning

confidence: 99%

Mapping General Anesthetic Sites in Heteromeric γ-Aminobutyric Acid Type A Receptors Reveals a Potential For Targeting Receptor Subtypes

Forman

Miller

2016

Anesthesia &Amp; Analgesia

Self Cite

View full text Add to dashboard Cite

Intravenous general anesthetics including propofol, etomidate, alphaxalone, and barbiturates, produce important actions by enhancing gamma-aminobutyric acid type A (GABA-A) receptor activation. Here we review scientific studies that have located and mapped IV anesthetic sites using photoaffinity labeling and substituted cysteine modification-protection. These anesthetics bind in transmembrane pockets between subunits of typical synaptic GABA-A receptors, and drugs that display stereoselectivity also show remarkably selective interactions with distinct interfacial sites. These results suggest strategies for developing new drugs that selectively modulate distinct GABA-A receptor subtypes.

show abstract

“…The TSI in mammalian GABACls has been extensively studied as a binding site for general anesthetics such as propofol, etomidate, and barbiturates (Forman and Miller, 2016). Interestingly, both convulsive and anesthetic barbiturates modulate GABACls by binding to this region (Jayakar et al, 2015). IVM activates currents and potentiates and antagonizes the agonist-induced currents of LGICs including GABACls and GluCls, with the latter being more sensitive than the former, by possibly binding in the TSI (Hibbs and Gouaux, 2011;Estrada-Mondragon and Lynch, 2015;Fuse et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

A Single Amino Acid Substitution in the Third Transmembrane Region Has Opposite Impacts on the Selectivity of the Parasiticides Fluralaner and Ivermectin for Ligand-Gated Chloride Channels

Nakata¹,

Fuse²,

Yamato³

et al. 2017

Mol Pharmacol

View full text Add to dashboard Cite

Fluralaner (Bravecto) is a recently marketed isoxazoline ectoparasiticide. This compound potently inhibits GABA-gated chloride channels (GABACls) and less potently glutamate-gated chloride channels (GluCls) in insects. The mechanism underlying this selectivity is unknown. Therefore, we sought to identify the amino acid residues causing the low potency of fluralaner toward GluCls. We examined the fluralaner sensitivity of mutant housefly () GluCls in which amino acid residues in the transmembrane subunit interface were replaced with the positionally equivalent amino acids of GABACls. Of these amino acids, substitution of an amino acid (Leu315) in the third transmembrane region (TM3) with an aromatic amino acid dramatically enhanced the potency of fluralaner in the GluCls. In stark contrast to the enhancement of fluralaner potency, this mutation eliminated the activation of currents and the potentiation but not the antagonism of glutamate responses that are otherwise all elicited by the macrolide parasiticide ivermectin (IVM). Our findings indicate that the amino acid Leu315 in GluCls plays significant roles in determining the selectivity of fluralaner and IVM for these channels. Given the high sequence similarity of TM3, this may hold true more widely for the GluCls and GABACls of other insect species.

show abstract

Positive and Negative Allosteric Modulation of an α1β3γ2 γ-Aminobutyric Acid Type A (GABAA) Receptor by Binding to a Site in the Transmembrane Domain at the γ+-β− Interface

Cited by 29 publications

References 48 publications

Tryptophan and Cysteine Mutations in M1 Helices of α1β3γ2L γ-Aminobutyric Acid Type A Receptors Indicate Distinct Intersubunit Sites for Four Intravenous Anesthetics and One Orphan Site

Tryptophan and Cysteine Mutations in M1 Helices of α1β3γ2L γ-Aminobutyric Acid Type A Receptors Indicate Distinct Intersubunit Sites for Four Intravenous Anesthetics and One Orphan Site

Mapping General Anesthetic Sites in Heteromeric γ-Aminobutyric Acid Type A Receptors Reveals a Potential For Targeting Receptor Subtypes

A Single Amino Acid Substitution in the Third Transmembrane Region Has Opposite Impacts on the Selectivity of the Parasiticides Fluralaner and Ivermectin for Ligand-Gated Chloride Channels

Contact Info

Product

Resources

About