The present study reports the isolation of a cDNA clone that encodes a second member of the corticotropin-releasing factor (CRF) receptor family, designated as the CRF2 receptor. The cDNA was identified using oligonucleotides of degenerate sequence in a PCR paradigm. A PCR fragment obtained from rat brain was utilized to isolate a full-length cDNA from a rat hypothalamus cDNA library that encoded a 411-amino acid protein with "70% identity to the known CRF1 receptor over the entire coding region. When expressed in mouse Ltk-cells, this receptor stimulates cAMP production in response to CRF and known CRF-like agonists. CRF and the nonmammalian CRF-related peptides sauvagine and urotensin I stimulate adenylate cyclase activity in a dose-dependent manner with a rank order of potency different from that of the CRF1 receptor: sauvagine > urotensinrat/human CRF > ovine CRF. Tissue distribution analysis of the mRNAs by reverse transcriptase-PCR shows CRF2 receptor mRNA is present in rat brain and detectable in lung and heart. In situ hybridization studies indicate specific expression within the brain in the ventromedial nuclei of the hypothalamus, the lateral septum, the amygdala, and entorhinal cortex, but there is unremarkable expression in the pituitary. An additional splice variant of the CRF2 receptor with a different N-terminal domain has been identified by PCR, encoding a putative protein of 431 amino acids. Thus, the data demonstrate the presence of another functional CRF receptor, with significant differences in the pharmacological profile and tissue distribution from the CRF1 receptor, which would predict important functional differences between the two receptors.Corticotropin-releasing factor (CRF), a 41-amino acid peptide, regulates the secretion of adrenocorticotropin and other proopiomelanocortin products from the anterior pituitary. CRF also coordinates the endocrine, behavioral, and autonomic responses to stress. Within the past few years, substantial evidence has accumulated from both laboratory and clinical studies implicating CRF as a physiological mediator of stress responses and stress-induced disorders (1-6). Immunocytochemical studies have shown that CRF is found within the paraventricular nucleus of the hypothalamus as well as limbic areas such as the central and medial nuclei of the amygdala, the bed nucleus of the stria terminalis, substantia inominata, septum, preoptic area, the lateral hypothalamus, and brain stem nuclei involved in stress responses and regulation of autonomic function, such as the locus coeruleus, the parabrachial nucleus, and the dorsal vagal complex (see ref. 7). CRF, when administered intracerebroventricularly, results in behavioral, physiological, and autonomic responses that are similar to those observed when animals are exposed to a stressful environment (4-6).
