Molecular identification and analysis of a novel human corticotropin-releasing factor (CRF) receptor: The CRF2γ receptor

We report the discovery of a new CRF2 receptor splice isoform found in human brain, which we have termed the CRF2 gamma receptor. The CRF2 gamma cDNA encodes for a 397-amino acid receptor that has an amino terminus with no significant homology to the already reported alpha- and beta-termini. When expressed in 293-EBNA (Epstein-Barr nuclear antigen) cells, the CRF,, receptor responds in a dose-dependent manner to CRF and related peptides with a rank order of potency of urocortin greater than or equal to sauvagine>urotensin>r/h CRF, with EC50 values more similar to CRF2 alpha than CRF2 beta. Equilibrium saturation isotherm analysis with radiolabeled sauvagine reveals a two site/state model for binding to CRF2 gamma with a 60 pM K-d high-affinity site and a 5 nM K-d low-affinity site. Analysis of CRF2 gamma RNA expression in human brain demonstrates expression in septum and hippocampus, with weaker but detectable expression in amygdala, nucleus accumbens, midbrain, and frontal cortex.