title: Targets for ethanol action and antagonism in loop 2 of the extracellular domain of glycine receptors.
abstract: The present studies used increased atmospheric pressure in place of a traditional pharmacological antagonist to probe the molecular sites and mechanisms of ethanol action in glycine receptors (GlyRs). Based on previous studies, we tested the hypothesis that physical-chemical properties at position 52 in extracellular domain Loop 2 of alpha1GlyRs, or the homologous alpha2GlyR position 59, determine sensitivity to ethanol and pressure antagonism of ethanol. Pressure antagonized ethanol in alpha1GlyRs that contain a non-polar residue at position 52, but did not antagonize ethanol in receptors with a polar residue at this position. Ethanol sensitivity in receptors with polar substitutions at position 52 was significantly lower than GlyRs with non-polar residues at this position. The alpha2T59A mutation switched sensitivity to ethanol and pressure antagonism in the WTalpha2GlyR, thereby making it alpha1-like. Collectively, these findings indicate that (i) polarity at position 52 plays a key role in determining sensitivity to ethanol and pressure antagonism of ethanol; (ii) the extracellular domain in alpha1- and alpha2GlyRs is a target for ethanol action and antagonism and (iii) there is structural-functional homology across subunits in Loop 2 of GlyRs with respect to their roles in determining sensitivity to ethanol and pressure antagonism of ethanol. These findings should help in the development of pharmacological agents that antagonize ethanol.
authors.affiliation: Alcohol and Brain Research Laboratory, Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA.
authors.forename: Daya I
authors.initials: DI
authors.lastname: Perkins
authors.forename: James R
authors.initials: JR
authors.lastname: Trudell
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Crawford
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Alkana
authors.forename: Daryl L
authors.initials: DL
authors.lastname: Davies
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems / Q000379:methods*; D000431:Ethanol / Q000008:administration & dosage*; D045604:Extracellular Fluid / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006801:Humans; D009865:Oocytes; D017434:Protein Structure, Tertiary / Q000187:drug effects; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: C439504:GLRA2 protein, human; D018009:Receptors, Glycine; D000431:Ethanol