Targets for ethanol action and antagonism in loop 2 of the extracellular domain of glycine receptors.
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.
Perkins
Daya I
DI
Alcohol and Brain Research Laboratory, Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA.
Trudell
James R
JR
Crawford
Daniel K
DK
Alkana
Ronald L
RL
Davies
Daryl L
DL
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
C439504:GLRA2 protein, human; D018009:Receptors, Glycine; D000431:Ethanol