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This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: mol.107.042978v1 73/5/1371    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Hoare, S. R. J. Articles by Grigoriadis, D. E. PubMed PubMed Citation Articles by Hoare, S. R. J. Articles by Grigoriadis, D. E.

Allosteric Ligands for the Corticotropin Releasing Factor Type 1 Receptor Modulate Conformational States Involved in Receptor Activation

Emerging Technologies (S.R.J.H., R.S.G, P.D.C, J.P.W, D.E.G.) and Endocrine and Metabolic (B.A.F, D.E.G.) Biomedical Research and Innovative Discovery Groups, Neurocrine Biosciences Inc., San Diego, California

Allosteric modulators of G-protein-coupled receptors can regulate conformational states involved in receptor activation ( Mol Pharmacol 58: 1412-1423, 2000[Medline] ). This hypothesis was investigated for the corticotropin-releasing factor type 1 (CRF₁) receptor using a novel series of ligands with varying allosteric effect on CRF binding (inhibition to enhancement). For the G-protein-uncoupled receptor, allosteric modulation of CRF binding was correlated with nonpeptide ligand signaling activity; inverse agonists inhibited and agonists enhanced CRF binding. These data were quantitatively consistent with a two-state equilibrium underlying the modulation of CRF binding to the G-protein-uncoupled receptor. We next investigated the allosteric effect on CRF-stimulated G-protein coupling. Ligands inhibited CRF-stimulated cAMP accumulation regardless of their effect on the G-protein-uncoupled state. The modulators reduced CRF E_max values, suggesting that they reduced the efficacy of a CRF-bound active state to couple to G-protein. Consistent with this hypothesis, the modulators inhibited binding to a guanine nucleotide-sensitive state. Together, the results are quantitatively consistent with a model in which 1) the receptor exists in three predominant states: an inactive state, a weakly active state, and a CRF-bound fully active state; 2) allosteric inverse agonists stabilize the inactive state, and allosteric agonists stabilize the weakly active state; and 3) antagonism of CRF signaling results from destabilization of the fully active state. These findings imply that nonpeptide ligands differentially modulate conformational states involved in CRF₁ receptor activation and suggest that different conformational states can be targeted in designing nonpeptide ligands to inhibit CRF signaling.

Address correspondence to: Dr. Sam R. J. Hoare, Emerging Technologies Biomedical Research and Innovative Discovery Group, Neurocrine Biosciences Inc., 12790 El Camino Real, San Diego, CA 92130. E-mail shoare{at}neurocrine.com