Corrections BIOCHEMISTRY NEUROSCIENCE Correction for “Quantitative phosphoproteomic analysis reveals Correction for “GABAA receptor target of tetramethylenedi- system-wide signaling pathways downstream of SDF-1/CXCR4 sulfotetramine,” by Chunqing Zhao, Sung Hee Hwang, Bruce A. in breast cancer stem cells,” by Tingfang Yi, Bo Zhai, Yonghao Buchholz, Timothy S. Carpenter, Felice Lightstone, Jun Yang, Yu, Yoshikawa Kiyotsugu, Thomas Raschle, Manuel Etzkorn, Bruce D. Hammock, and John E. Casida, which appeared in issue Hee-Chan Seo, Michal Nagiec, Rafael E. Luna, Ellis L. Reinherz, 23, June 10, 2014, of Proc Natl Acad Sci USA (111:8607–8612; first John Blenis, Steven P. Gygi, and Gerhard Wagner, which appeared published May 27, 2014; 10.1073/pnas.1407379111). in issue 21, May 27, 2014, of Proc Natl Acad Sci USA (111:E2182– The authors note that the author name Felice Lightstone E2190; first published April 29, 2014; 10.1073/pnas.1404943111). should instead appear as Felice C. Lightstone. The corrected The authors note that all instances of “δ-catenin” should in- author line appears below. The online version has been corrected. stead appear as “p120-catenin.” Chunqing Zhao, Sung Hee Hwang, Bruce A. Buchholz, www.pnas.org/cgi/doi/10.1073/pnas.1411381111 Timothy S. Carpenter, Felice C. Lightstone, Jun Yang, Bruce D. Hammock, and John E. Casida www.pnas.org/cgi/doi/10.1073/pnas.1412593111 GENETICS Correction for “Noninvasive in vivo monitoring of tissue-specific global gene expression in humans,” by Winston Koh, Wenying Pan, Charles Gawad, H. Christina Fan, Geoffrey A. Kerchner, Tony Wyss-Coray, Yair J. Blumenfeld, Yasser Y. El-Sayed, and Stephen R. Quake, which appeared in issue 20, May 20, 2014, of Proc Natl Acad Sci USA (111:7361–7366; first published May 5, 2014; 10.1073/pnas.1405528111). The authors note that the accession number for Bioproject is PRJNA247931 and the accession number for SRA Study is SRP042027. www.pnas.org/cgi/doi/10.1073/pnas.1412162111 CORRECTIONS www.pnas.org PNAS | July 29, 2014 | vol. 111 | no. 30 | 11223 Downloaded by guest on September 24, 2021 GABAA receptor target of tetramethylenedisulfotetramine Chunqing Zhaoa,1, Sung Hee Hwangb, Bruce A. Buchholzc,2, Timothy S. Carpenterd, Felice C. Lightstoned,2, Jun Yangb, Bruce D. Hammockb,2, and John E. Casidaa,2 aEnvironmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; bDepartment of Entomology, College of Agricultural and Environmental Science, University of California, Davis, CA 95616; and cCenter for Accelerator Mass Spectrometry and dBiosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551 Contributed by John E. Casida, April 24, 2014 (sent for review March 22, 2014) Use of the highly toxic and easily prepared rodenticide tetrame- modulating the target site to reduce disruption by the toxicant. thylenedisulfotetramine (TETS) was banned after thousands of TETS toxicity is reported to be alleviated in rodents or humans accidental or intentional human poisonings, but it is of continued by diazepam, barbiturates, allopregnanolone, and sodium 2,3- concern as a chemical threat agent. TETS is a noncompetitive dimercapto-1- propanesulfonate (NaDMPS), some of which are blocker of the GABA type A receptor (GABAAR), but its molecular GABAAR modulators (16–24) (SI Appendix, section S1). TETS is interaction has not been directly established for lack of a suitable one of several small-cage convulsants, a group that also includes 14 radioligand to localize the binding site. We synthesized [ C]TETS bicyclophosphorus compounds, such as the even more toxic t-butyl- (14 mCi/mmol, radiochemical purity >99%) by reacting sulfamide bicyclophosphate (TBPO) and t-butylbicyclophosphorothionate 14 s with H CHO and -trioxane then completion of the sequential cycli- (TBPS) (25) (Fig. 1). zation with excess HCHO. The outstanding radiocarbon sensitivity of TETS is a noncompetitive antagonist of the GABA type A re- accelerator mass spectrometry (AMS) allowed the use of [14C]TETS in ceptor (GABAAR) based on multiple physiological and toxicolog- neuroreceptor binding studies with rat brain membranes in compar- ical criteria* (20, 26–29) (SI Appendix,sectionS1)andGABA R ′ n 3 A ison with the standard GABAAR radioligand 4 -ethynyl-4- -[ H]pro- assays with two trioxabicyclooctane radioligands, [35S]TBPS (30), pylbicycloorthobenzoate ([3H]EBOB) (46 Ci/mmol), illustrating the use and 4-n-[3H]propyl-4′-ethynylbicycloorthobenzoate ([3H]EBOB) of AMS for characterizing the binding sites of high-affinity 14Cradio- (31) (Fig. 1). TETS is a competitive inhibitor of [3H]EBOB ligands. Fourteen noncompetitive antagonists of widely diverse che- binding with a potency in rat brain GABA R consistent with motypes assayed at 1 or 10 μMinhibited[14C]TETS and [3H]EBOB A r2 = its toxicity in mice (4, 32). However, it does not inhibit human binding to a similar extent ( 0.71). Molecular dynamics simula- β 3 tions of these 14 toxicants in the pore region of the α1β2γ2 GABA R GABAAR recombinant 3 homopentamer assayed with [ H]EBOB A (33), which has a structure–activity relationship for inhibitors predict unique and significant polar interactions for TETS with α1T1′ γ ′ similar to that for the housefly GABAR (34). These deductions and 2S2 , which are not observed for EBOB or the GABAergic insec- 35 3 14 are based on the use of [ S]TBPS and [ H]EBOB to assay the ticides. Several GABAAR modulators similarly inhibited [ C]TETS and [3H]EBOB binding, including midazolam, flurazepam, avermectin Ba1, action of TETS. NEUROSCIENCE baclofen, isoguvacine, and propofol, at 1 or 10 μM, providing an in Direct observation of the TETS binding site requires the use of vitro system for recognizing candidate antidotes. TETS as the radioligand. Radioligand binding studies for neu- roreceptors as toxicant targets normally require high specific ac- 3 neurotoxicity | convulsant | molecular modeling tivities (>10 Ci/mmol) such as H labeling, which is not available to date for TETS. [14C]TETS reported here has a specific activity evere poisonings in a German furniture factory in the 1940s Swere traced to wool impregnated with the resinous reaction Significance product of sulfamide (NH2SO2NH2) and formaldehyde (HCHO). The causative agent was identified as tetramethylenedisulfotetr- Tetramethylenedisulfotetramine (TETS) is a feared chemical threat amine (TETS, also known as tetramine) which was then developed agent because of its high convulsant toxicity, ease of synthesis, as a rodenticide (now illegal) and continues to be of concern as and availability even though it is banned as a rodenticide. Earlier a chemical threat agent. The chronology of TETS chemistry physiological evidence indicating action as a GABA receptor an- and toxicology is given briefly here and more extensively in SI tagonist and inhibitor of [35S]TBPS and [3H]EBOB binding is con- 14 Appendix, section S1. firmed here by radiosynthesis of [ C]TETS and defining its binding TETS was first synthesized more than 80 y ago (1–3). Structure– site in rat brain membranes by accelerator mass spectrometry and 14 3 activity studies showed that any structural modification greatly toxicant specificity studies on inhibition of [ C]TETS and [ H]EBOB reduces the toxicity (4). The need to understand the distribution binding. TETS undergoes specific and unique polar interactions and fate of TETS led to 14C radiosynthesis in 1967 (5) by an un- inside the 1′2′ ring pore region instead of the 2′,6′,and9′ site for disclosed method, but the product was only 80% pure, limiting the insecticides. This study helps define GABAAR sites for potential interpretation of biological experiments. Analysis is achieved by antidotes acting to prevent TETS binding or displace it from its liquid chromatography/MS (6) or when ultrahigh sensitivity is re- binding site. quired and [14C]TETS is available by accelerator mass spectrom- Author contributions: B.D.H. and J.E.C. designed research; C.Z., S.H.H., B.A.B., and J.Y. etry (AMS) (7), as reported here. – performed research; T.S.C. and F.C.L. analyzed data; and B.D.H. and J.E.C. wrote the paper. TETS is highly toxic to mammals with an i.p. LD50 of 0.11 0.22 The authors declare no conflict of interest. mg/kg in mice and rats, leading to its use as a rodenticide until it 1Present address: College of Science, China Agricultural University, Beijing 100193, China. was banned worldwide in the early 1990s (2, 8, 9). However, it is 2To whom correspondence may be addressed. E-mail: [email protected], lightstone1@ still available illegally and responsible for accidental or intentional llnl.gov, [email protected], or [email protected]. poisonings in China and other countries. The estimated lethal dose This paper contains supporting information online at www.pnas.org/lookup/suppl/doi:10. of 7–10 mg in adult humans coupled with its ease of synthesis and 1073/pnas.1407379111/-/DCSupplemental. – stability serve as the basis for the chemical threat concern (10 15). *Zolkowska D, et al., American Epilepsy Society Annual Meeting, December 2–6, 2011, Neurotoxicity is sometimes alleviated or antidoted by compounds Baltimore, abstr 3.069. www.pnas.org/cgi/doi/10.1073/pnas.1407379111 PNAS | June 10, 2014 | vol. 111 | no. 23 | 8607–8612 in water) or its equivalent such as s-trioxane or paraformaldehyde in acidic condition (2, 4). However, the low concentration of commercially available H14CHO (1–3% in water) seriously delayed the final ring cyclization step to form [14C]TETS. To overcome this, the procedure was modified by stepwise cyclization (Fig. 2). Reaction conditions were optimized through tests with H13CHO as the H14CHO mimic. H13CHO (20% aqueous solution, 0.25 equivalents relative to sulfamide) and s-trioxane (source of 1.75 equivalents of HCHO as a solid form) ensured that all H13CHO was incorporated into the product owing to the slower release of unlabeled HCHO from s-trioxane.