Each year millions of people undergo general anesthesia so that surgeons can perform life-saving operations. For most patients general anesthesia is safe and effective, however, side effects, such as nausea and vomiting, and complications, such as cardiovascular instability or cognitive dysfunction, increase anesthesia-associated morbidity. Understanding the molecular basis of general anesthetic action may lead to the identification of newer and safer general anesthetics. The long term goal of this project is to elucidate the molecular bases of general anesthesia. Propofol, a widely used intravenous general anesthetic, is the major focus of this project. At concentrations used clinically, propofol interacts with many proteins, however, a major target for its anesthetic effects is the GABA-A receptors. This project will focus on propofol's interactions with GABA-A receptors. In order to understand the molecular basis of propofol's action we must identify the amino acids that form its binding sites, elucidate the conformational changes that it induces, and determine how these conformational changes modulate receptor function. Our ability to accomplish these goals took a quantum leap forward with the recent publication of the homologous acetylcholine binding protein (AChBP) and nicotinic acetylcholine (ACh) receptor structures. These structures provide a solid foundation for structure-based studies of anesthetic interactions with GABA-A receptors. This structural information will guide our experimental design and the interpretation of our results. We propose the following Specific Aims: 1) To identify the residues that lie in close proximity to the propofol binding site near the beta subunit Met286 position and to determine the orientation of propofol in the binding site using sulfhydryl- reactive propofol derivatives. 2) To probe the extent of conformational changes induced by potentiating concentrations of propofol in the M2 segment that lines the ion channel and forms the channel gate. These experiments will serve the dual purposes of verifying the applicability of the ACh-derived structural information to GABA-A receptors and placing structure-function studies of anesthetic interactions with ion channels on a sound structural basis. The successful completion of this project will provide dynamic information on propofol's interactions with GABA-A receptors and new insights into the molecular basis of general anesthetic action. They may provide a rational basis for design of new, safer general anesthetics.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM077660-04
Application #
7663952
Study Section
Special Emphasis Panel (ZRG1-MDCN-F (02))
Program Officer
Cole, Alison E
Project Start
2006-05-01
Project End
2011-04-30
Budget Start
2009-05-01
Budget End
2011-04-30
Support Year
4
Fiscal Year
2009
Total Cost
$354,609
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Physiology
Type
Schools of Medicine
DUNS #
110521739
City
Bronx
State
NY
Country
United States
Zip Code
10461
Akabas, Myles H (2012) Channels: Rotamers affect ion conductance. Nat Chem Biol 8:953-4
Akabas, Myles H (2011) Ion channels: Manipulating the munchies in mice. Nat Chem Biol 7:759-60
Parikh, Rishi B; Bali, Moez; Akabas, Myles H (2011) Structure of the M2 transmembrane segment of GLIC, a prokaryotic Cys loop receptor homologue from Gloeobacter violaceus, probed by substituted cysteine accessibility. J Biol Chem 286:14098-109
Bali, Moez; Jansen, Michaela; Akabas, Myles H (2009) GABA-induced intersubunit conformational movement in the GABAA receptor alpha 1M1-beta 2M3 transmembrane subunit interface: experimental basis for homology modeling of an intravenous anesthetic binding site. J Neurosci 29:3083-92
Jansen, Michaela; Rabe, Holger; Strehle, Axelle et al. (2008) Synthesis of GABAA receptor agonists and evaluation of their alpha-subunit selectivity and orientation in the GABA binding site. J Med Chem 51:4430-48
Zhao, Rongbao; Qiu, Andong; Tsai, Eugenia et al. (2008) The proton-coupled folate transporter: impact on pemetrexed transport and on antifolates activities compared with the reduced folate carrier. Mol Pharmacol 74:854-62
Jansen, Michaela; Bali, Moez; Akabas, Myles H (2008) Modular design of Cys-loop ligand-gated ion channels: functional 5-HT3 and GABA rho1 receptors lacking the large cytoplasmic M3M4 loop. J Gen Physiol 131:137-46
Bali, Moez; Akabas, Myles H (2007) The location of a closed channel gate in the GABAA receptor channel. J Gen Physiol 129:145-59
Rosen, Ayelet; Bali, Moez; Horenstein, Jeffrey et al. (2007) Channel opening by anesthetics and GABA induces similar changes in the GABAA receptor M2 segment. Biophys J 92:3130-9
Jansen, Michaela; Akabas, Myles H (2006) State-dependent cross-linking of the M2 and M3 segments: functional basis for the alignment of GABAA and acetylcholine receptor M3 segments. J Neurosci 26:4492-9

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