Cloning and characterization of a short variant of the corticotropin-releasing factor receptor subtype from rat amygdala

We have identified and characterized a cDNA encoding a novel isoform of the corticotropin-releasing factor(CRF) receptor, referred to as CRF2 alpha-tr, from the rat amygdala cDNA library. The nucleotide sequence of the cloned cDNA-has a structure of an alternatively spliced form of the CRF2 alpha receptor, which contains unspliced introns 6 and 7 in the message, and encodes a 236-amino-acid truncated protein that comprises three unique transmembrane domains. Northern blot analysis shows that the CRF2 alpha-tr receptor is more strongly expressed in the rat amygdala, thalamus, and hypothalamus than the intact CRF2 alpha receptor. Western blot analysis also reveals that the CRF2 alpha-tr protein can be expressed in transfected COS-7 cells as well as CRF2 alpha. Furthermore, this receptor binds rat/human CRF with almost the same low affinity (Kd = 12.7 nM) as the CRF2 alpha and without accumulation of intracellular cAMP. interestingly, it does not bind sauvagine or-rat urocortin, These findings suggest that this truncated CRF receptor is the major isoform of CRF2 alpha receptor mRNA transcripts in the amygdala and would mediate some functions of CRP pathways in:the central nervous system. (C) 1999 Academic Press.