title: GABAA receptor target of tetramethylenedisulfotetramine.
abstract: Use of the highly toxic and easily prepared rodenticide tetramethylenedisulfotetramine (TETS) was banned after thousands of accidental or intentional human poisonings, but it is of continued concern as a chemical threat agent. TETS is a noncompetitive blocker of the GABA type A receptor (GABAAR), but its molecular interaction has not been directly established for lack of a suitable radioligand to localize the binding site. We synthesized [(14)C]TETS (14 mCi/mmol, radiochemical purity >99%) by reacting sulfamide with H(14)CHO and s-trioxane then completion of the sequential cyclization with excess HCHO. The outstanding radiocarbon sensitivity of accelerator mass spectrometry (AMS) allowed the use of [(14)C]TETS in neuroreceptor binding studies with rat brain membranes in comparison with the standard GABAAR radioligand 4'-ethynyl-4-n-[(3)H]propylbicycloorthobenzoate ([(3)H]EBOB) (46 Ci/mmol), illustrating the use of AMS for characterizing the binding sites of high-affinity (14)C radioligands. Fourteen noncompetitive antagonists of widely diverse chemotypes assayed at 1 or 10 µM inhibited [(14)C]TETS and [(3)H]EBOB binding to a similar extent (r(2) = 0.71). Molecular dynamics simulations of these 14 toxicants in the pore region of the α1β2γ2 GABAAR predict unique and significant polar interactions for TETS with α1T1' and γ2S2', which are not observed for EBOB or the GABAergic insecticides. Several GABAAR modulators similarly inhibited [(14)C]TETS and [(3)H]EBOB binding, including midazolam, flurazepam, avermectin Ba1, baclofen, isoguvacine, and propofol, at 1 or 10 μM, providing an in vitro system for recognizing candidate antidotes.
authors.affiliation: Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720;
authors.forename: Chunqing
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Department of Entomology, College of Agricultural and Environmental Science, University of California, Davis, CA 95616; and.
authors.forename: Sung Hee
authors.initials: SH
authors.lastname: Hwang
authors.affiliation: Center for Accelerator Mass Spectrometry and buchholz2@llnl.gov lightstone1@llnl.gov bdhammock@ucdavis.edu ectl@berkeley.edu.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Buchholz
authors.affiliation: Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Carpenter
authors.forename: Felice C
authors.initials: FC
authors.lastname: Lightstone
authors.affiliation: Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551 buchholz2@llnl.gov lightstone1@llnl.gov bdhammock@ucdavis.edu ectl@berkeley.edu.
authors.forename: Felice
authors.initials: F
authors.lastname: Lightstone
authors.affiliation: Department of Entomology, College of Agricultural and Environmental Science, University of California, Davis, CA 95616; and.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Entomology, College of Agricultural and Environmental Science, University of California, Davis, CA 95616; and buchholz2@llnl.gov lightstone1@llnl.gov bdhammock@ucdavis.edu ectl@berkeley.edu.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
authors.affiliation: Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; buchholz2@llnl.gov lightstone1@llnl.gov bdhammock@ucdavis.edu ectl@berkeley.edu.
authors.forename: John E
authors.initials: JE
authors.lastname: Casida
mesh_terms: D000577:Amides / Q000737:chemistry; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry / Q000378:metabolism; D001952:Bridged-Ring Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D005557:Formaldehyde / Q000737:chemistry; D018755:GABA Agonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists / Q000737:chemistry / Q000378:metabolism*; D006571:Heterocyclic Compounds / Q000737:chemistry; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007306:Insecticides / Q000737:chemistry / Q000378:metabolism; D007539:Isonicotinic Acids / Q000494:pharmacology; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D015742:Propofol / Q000494:pharmacology; D011736:Pyridoxine / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism*; D013455:Sulfur / Q000737:chemistry; D014803:Vitamin B Complex / Q000494:pharmacology
chemical_list: D000577:Amides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D001952:Bridged-Ring Compounds; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D018755:GABA Agonists; D058787:GABA-A Receptor Antagonists; D006571:Heterocyclic Compounds; D006993:Hypnotics and Sedatives; D007306:Insecticides; D007539:Isonicotinic Acids; D011963:Receptors, GABA-A; C091518:1-(4-ethynylphenyl)-4-propyl-2,6,7-trioxabicyclo(2.2.2)octane; D014803:Vitamin B Complex; D005557:Formaldehyde; C011374:s-trioxane; D013455:Sulfur; C010349:tetramethylenedisulfotetramine; D011736:Pyridoxine; D015742:Propofol; C015300:isoguvacine
keywords: convulsant; molecular modeling; neurotoxicity