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ABSTRACT: Structural changes induced by the binding of agonists, antagonists and inverse agonists to the cloned delta-opioid receptor from human brain immobilized in a solid-supported lipid bilayer were monitored using plasmon-waveguide resonance (PWR) spectroscopy. Agonist (e.g. deltorphin II) binding causes an increase in membrane thickness because of receptor elongation, a mass density increase due to an influx of lipid molecules into the bilayer, and an increase in refractive index anisotropy due to transmembrane helix and fatty acyl chain ordering. In contrast, antagonist (e.g. TIPPpsi) binding produces no measurable change in either membrane thickness or mass density, and a significantly larger increase in refractive index anisotropy, the latter thought to be due to a greater extent of helix and acyl chain ordering within the membrane interior. These results are closely similar to those reported earlier for another agonist (DPDPE) and antagonist (naltrindol) [Salamon et al. (2000) Biophys. J.79, 2463-2474]. In addition, we now find that an inverse agonist (TMT-Tic) produces membrane thickness, mass density and refractive index anisotropy increases which are similar to, but considerably smaller than, those generated by agonists. Thus, a third conformational state is produced by this ligand, different from those formed by agonists and antagonists. These results shed new light on the mechanisms of ligand-induced G-protein-coupled receptor functioning. The potential utilization of this new biophysical method to examine structural changes both parallel and perpendicular to the membrane normal for GPCRs is emphasized.
European Journal of Allergy and Clinical Immunology 01/2003; 60(6):322-8. · 1.30 Impact Factor
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ABSTRACT: Structural changes accompanying the binding of ligands to the cloned human delta-opioid receptor immobilized in a solid-supported lipid bilayer have been investigated using coupled plasmon-waveguide resonance spectroscopy. This highly sensitive technique directly monitors mass density, conformation, and molecular orientation changes occurring in anisotropic thin films and allows direct determination of binding constants. Although both agonist binding and antagonist binding to the receptor cause increases in molecular ordering within the proteolipid membrane, only agonist binding induces an increase in thickness and molecular packing density of the membrane. This is a consequence of mass movements perpendicular to the plane of the bilayer occurring within the lipid and receptor components. These results are consistent with models of receptor function that involve changes in the orientation of transmembrane helices.
Biophysical Journal 12/2000; 79(5):2463-74. · 3.65 Impact Factor
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T H Burkey,
F J Ehlert,
Y Hosohata,
R M Quock, S Cowell,
K Hosohata,
E Varga,
D Stropova,
X Li,
C Slate,
H Nagase,
F Porreca,
V J Hruby,
W R Roeske,
H I Yamamura
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ABSTRACT: Delta-opioid receptor-selective drugs may provide an alternative to mu-opioid-selective drugs currently used for the relief of pain. To develop improved delta-opioid receptor-selective drugs, better measures of drug activity are necessary. In this review we suggest that efficacy calculations provide a superior measure of drug activity as compared to dissociation constants and drug potencies in functional assays. Efficacy, as discussed in this review, is defined as a quantitative measurement of the ability of a drug to stimulate second messenger systems or measurable functional responses in cells or tissues under standard conditions. Efficacy values will allow medicinal chemists to understand the contributions of both the coupling efficiency and dissociation constant to drug potencies in the development of new delta-opioid receptor-selective drugs.
Life Sciences 02/1998; 62(17-18):1531-6. · 2.53 Impact Factor
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T.H. Burkey,
F.J. Ehlert,
Y. Hosohata,
R.M. Quock, S. Cowell,
K. Hosohata,
E. Varga,
D. Stropova,
X. Li,
C. Slate,
H. Nagase,
F. Porreca,
V.J. Hruby,
W.R. Roeske,
H.I. Yamamura
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ABSTRACT: δ-Opioid receptor-selective drugs may provide an alternative to μ-opioid-selective drugs currently used for the relief of pain. To develop improved δ-opioid receptor-selective drugs, better measures of drug activity are necessary. In this review we suggest that efficacy calculations provide a superior measure of drug activity as compared to dissociation constants and drug potencies in functional assays. Efficacy, as discussed in this review, is defined as a quantitative measurement of the ability of a drug to stimulate second messenger systems or measurable functional responses in cells or tissues under standard conditions. Efficacy values will allow medicinal chemists to understand the contributions of both the coupling efficiency and dissociation constant to drug potencies in the development of new δ-opioid receptor-selective drugs.
Life Sciences.
