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

Authors


Department of Peptide Chemistry/Biochemistry, Leibniz Institute of Molecular Pharmacology, Robert-Rössle-Street 10, Berlin D-13125, Germany. E-mail: beyermann@fmp-berlin.de

Abstract

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

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