IDENTIFICATION OF A 2ND CORTICOTROPIN-RELEASING FACTOR-RECEPTOR GENE AND CHARACTERIZATION OF A CDNA EXPRESSED IN HEART

Corticotropin-releasing factor (CRF; corticoliberin) regulates the sec retion of corticotropin (ACTH) and beta-endorphin and has a broad rang e of effects on the nervous, endocrine, reproductive, cardiovascular, gastrointestinal, and immune systems. Recently, human, rat, and mouse CRF receptors (CRF-R) have been cloned and functionally and anatomical ly characterized, We report here the cloning of a second CRF-R cDNA (C RF-RB), which encodes a protein of 431 amino acids, which is 16 amino acids longer and 68% similar to the previously cloned CRF-R, CRF-RA, W hen transiently expressed in COS-R 16 cells, CRF-RB binds CRF with hig h affinity [K-d = 1.2 (0.57-2.5) nM] and transduces the CRF-stimulated signal of the accumulation of intracellular cAMP, which is inhibited by a CRF antagonist. Comparison of the amino acid sequences of CRF-RB and the previously cloned receptor reveals major differences in the N- terminal domain and in the extracellular loops, whereas the sequences of the intracellular loops are nearly identical. CRF-RB and related tr anscripts are expressed in the heart, as well as in other tissues, inc luding the gastrointestinal tract, epididymis, and brain.