Corticotropin‐releasing factor receptor type 1 from <i>Tupaia belangeri</i>

Abstract

A cDNA clone encoding corticotropin‐releasing factor (CRF) type 1 (CRF‐R1) has been isolated from the tree shrew Tupaia belangeri with a PCR‐based approach. The full‐length cDNA encoded a 415‐amino‐acid protein with highest sequence identity (≈98 %) to human CRF‐R1 and slightly less identity to rat or mouse CRF‐R1 (≈97 %). Only eight amino acids (residues 3, 4, 6, 35, 36 and 39 in the N‐terminus, residue 232 in transmembrane domain 4 and residue 410 in the C‐terminus) differed between tree shrew CRF‐R1 (tCRF‐R1) and human CRF‐R1 (hCRF‐R1). tCRF‐R1 mRNA was detected by semiquantitative RT‐PCR and RNase protection analysis in the pituitary and in brain areas such as amygdala, brainstem, cerebellum, cortex, olfactory bulb, and striatum. In peripheral organs, only weak expression of tCRF‐R1 mRNA was observed in ovary, testis, and adrenal gland. Binding studies using human embryonic kidney 293 (HEK293) cells stably transfected with tCRF‐R1 showed that the CRF agonists ovine CRF ( K D = 1.28 nM), human/rat CRF ( K D = 1.09 nM), urocortin ( K D = 0.37 nM) and sauvagine ( K D = 0.77 nM), respectively, were bound with significantly higher affinities than the CRF antagonist astressin ( K D = 12.4 nM). In agreement with the binding data half maximum effective EC 50 values of 0.83 nM (human/rat CRF), 1.41 nM (ovine CRF), 1.25 nM (rat urocortin) and 0.71 nM (sauvagine) were calculated when the cAMP production in HEK293 cells stably transfected with tCRF‐R1 was stimulated with the four CRF analogues. These data underline the close relationship between human and tree shrew CRF‐R1.

Keywords

Affiliated Institutions

• Max Planck Institute of Experimental Medicine DE
• German Primate Center DE
• Roche (Switzerland) CH

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