The goal of the Chemistry Core is to provide chemistry support to the three projects involved in the Program Project Grant """"""""General Anesthetic Sites on Ligand-Gated Ion Channels"""""""". The overall mission of this PPG is to identify binding sites for common general anesthetics - modulators of GABAA and glycine receptors, exemplified by anesthetic steroids, barbiturates, propofol and etomidate. The general strategy is to synthesize and apply analogs of the known anesthetics equipped with the photo-reactive chemical residues. Illumination of the receptor - modulator complexes with UV light forms reactive carbene or nitrene species that indiscriminately modify chemical residues at the modulator binding site. Determining the location and make up of these sites will advance understanding of molecular mechanisms underlying general anesthesia. The goal of Chemistry Core will be realized in four specific aims, each targeting a different class of allosteric modulators of GABAA and glycine receptors. (1) To synthesize diazirine and azide analogs of alphaxalone, a known steroid anesthetic. The goal is to reproduce the pharmacological properties of the parent steroid, but build-in the photo-reactive residues at four different locations of the steroid framework within the confines of the binding sites. Photolabeling patterns by these analogs should enable determination of the binding site location and the binding poses of the ligands within the site. (2) To synthesize subunit-interface selective analogs of mephobarbital. The structural design involves optimization of the substituents at the N-1 and C-5 positions of barbituric acid for highest subunit-interface-selectivity and highest affinity. Our design will involve substituents of varying length and size at N-1, and alkene, vinyl and cyclopropyl chains of varying rigidity and geometry at C-5. (3) To synthesize photo-reactive analogs of propofol for identification of the binding sites on GABAA and glycine receptors. Analogs in which phenol OH group in propofol is separated from the phenyl ring will be synthesized to avoid stabilization of the carbene at the benzylic positions in ortho- or para-positions. sec-Butyl analogs of diazirine-modified propofols with higher affinity will also be synthesized as separate enantiomers. Additionally, p-halogenated analogs will be synthesized as potential photoprobes for GABAA and glycine receptors. In view of the disparity of the published results and those recently obtained by the PPG on the potency of p-chloro-propofol as a modulator of the glycine receptor, we will identify products of the photolytic breakdown of this compound and synthesize them as possible novel potent modulators of this receptor. (4) To synthesize smaller-sized photoreactive analogs of etomidate. The assessment of the available space in the etomidate binding site will be performed first by analogs with varying size of substitution in the phenyl ring. Finally, analogs with smaller five-membered aromatic residues, such as furane, bearing a smaller fluorodiazirine and diazo photo-reactive residues will also be synthesized.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Program Projects (P01)
Project #
2P01GM058448-16
Application #
8742129
Study Section
Special Emphasis Panel (ZGM1)
Project Start
Project End
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
16
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02199
Woll, Kellie A; Zhou, Xiaojuan; Bhanu, Natarajan V et al. (2018) Identification of binding sites contributing to volatile anesthetic effects on GABA type A receptors. FASEB J 32:4172-4189
McGrath, Megan; Yu, Zhiyi; Jayakar, Selwyn S et al. (2018) Etomidate and Etomidate Analog Binding and Positive Modulation of ?-Aminobutyric Acid Type A Receptors: Evidence for a State-dependent Cutoff Effect. Anesthesiology 129:959-969
Feng, Hua-Jun; Forman, Stuart A (2018) Comparison of ??? and ??? GABAA receptors: Allosteric modulation and identification of subunit arrangement by site-selective general anesthetics. Pharmacol Res 133:289-300
McGrath, Megan; Ma, Celena; Raines, Douglas E (2018) Dimethoxy-etomidate: A Nonhypnotic Etomidate Analog that Potently Inhibits Steroidogenesis. J Pharmacol Exp Ther 364:229-237
Zhou, Xiaojuan; Desai, Rooma; Zhang, Yinghui et al. (2018) High-level production and purification in a functional state of an extrasynaptic gamma-aminobutyric acid type A receptor containing ?4?3? subunits. PLoS One 13:e0191583
Ziemba, Alexis M; Szabo, Andrea; Pierce, David W et al. (2018) Alphaxalone Binds in Inner Transmembrane ?+-?- Interfaces of ?1?3?2 ?-Aminobutyric Acid Type A Receptors. Anesthesiology 128:338-351
Forman, Stuart A (2018) Combining Mutations and Electrophysiology to Map Anesthetic Sites on Ligand-Gated Ion Channels. Methods Enzymol 602:369-389
Ma, Celena; Pejo, Ervin; McGrath, Megan et al. (2017) Competitive Antagonism of Anesthetic Action at the ?-Aminobutyric Acid Type A Receptor by a Novel Etomidate Analog with Low Intrinsic Efficacy. Anesthesiology 127:824-837
Jounaidi, Youssef; Cotten, Joseph F; Miller, Keith W et al. (2017) Tethering IL2 to Its Receptor IL2R? Enhances Antitumor Activity and Expansion of Natural Killer NK92 Cells. Cancer Res 77:5938-5951
Yu, Zhiyi; Cohen, Jonathan B (2017) Enantiomeric barbiturates bind distinct inter- and intrasubunit binding sites in a nicotinic acetylcholine receptor (nAChR). J Biol Chem 292:17258-17271

Showing the most recent 10 out of 116 publications