Evidence that corticotropin‐releasing factor receptor type 1 couples to Gs‐ and Gi‐proteins through different conformations of its J‐domain

• Published in: British journal of pharmacology Vol. 149; no. 7; pp. 942 - 947
• Main Authors: Berger, H, Heinrich, N, Wietfeld, D, Bienert, M, Beyermann, M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-2006; Nature Publishing; Nature Publishing Group
• Subjects: Allosteric Regulation; Amphibian Proteins; Binding, Competitive; Biological and medical sciences; Cell Line; Corticotropin-Releasing Hormone - pharmacology; CRF receptor 1; Dose-Response Relationship, Drug; GTP-Binding Protein alpha Subunits, Gi-Go - metabolism; GTP-Binding Protein alpha Subunits, Gs - metabolism; Guanosine 5'-O-(3-Thiotriphosphate); G‐protein coupling; Hormone Antagonists - pharmacology; Humans; Medical sciences; Models, Molecular; non‐peptide antagonist; Peptide Fragments - pharmacology; Peptide Hormones; Peptides - pharmacology; Pharmacology. Drug treatments; Protein Conformation; Protein Structure, Tertiary; Pyrimidines - pharmacology; Pyrroles - pharmacology; Receptors, Corticotropin-Releasing Hormone - chemistry; Receptors, Corticotropin-Releasing Hormone - drug effects; Receptors, Corticotropin-Releasing Hormone - genetics; Receptors, Corticotropin-Releasing Hormone - metabolism; Research Papers; Signal Transduction - drug effects; Transfection; two‐domain model; Urocortins; CRF receptor; CRF receptor 1; Non peptide compound; Models; Antagonist; two-domain model; G-protein coupling; non-peptide antagonist; G protein
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0706926

Background and purpose:
According to the two‐domain model for the corticotropin‐releasing factor receptor type 1 (CRF1), peptide antagonists bind to the N‐terminal domain (N‐domain), non‐peptide antagonists to the transmembrane region (J‐domain), whereas peptide agonists attach to both the N‐ and J‐domain of the receptor to express activity. The aim of this study was to search for possible differences in the antagonism of the Gs‐ and Gi‐protein coupling of CRF1 by a peptide (α‐helical CRF(9–41)) and non‐peptide antagonist (antalarmin), to determine whether the conformational requirements of the activated CRF1 states for Gs and Gi coupling are similar or different.
Experimental approach:
We studied the inhibitory effect of α‐helical CRF(9–41) and antalarmin on the coupling of CRF1 to Gs‐ and Gi‐protein in human embryonic kidney cells, using the [35S]‐GTPγS binding stimulation assay.
Key results:
The non‐peptide antagonized the receptor coupling to Gs competitively but that to Gi noncompetitively, and its antagonistic potency was different for urocortin‐ and sauvagine‐evoked G‐protein activation. In contrast, the peptide antagonist exhibited uniformly competitive antagonism.
Conclusions and Implications:
The results allow us to extend the two‐domain model of CRF1 activation by assuming that CRF1 agonists activate the receptor by binding to at least two ensembles of J‐domain configurations which couple to Gs or Gi, that are in turn antagonized by a non‐peptide antagonist competitively and allosterically, respectively. It is further concluded that the allosteric mechanism of non‐peptide antagonism is not valid for the Gs‐mediated physiological activities of CRF1.
British Journal of Pharmacology (2006) 149, 942–947. doi:10.1038/sj.bjp.0706926