Neurobiology of corticotropin releasing factor (CRF) receptors and CRF-binding protein: implications for the treatment of CNS disorders.

The actions of CRF in the brain and in the periphery are mediated through multiple binding sites. There are three receptors, CRF1, CRF2 alpha and CRF2 beta, which encode 411, 415 and 431 amino acid proteins and transduce signals via the stimulation of intracellular cAMP production. The recent identification of high-affinity non-peptide CRF receptor antagonists should allow for rapid progress in drug development of CRF receptor antagonists. In addition to the receptors, the actions of CRF in brain and in the periphery can also be modulated by a binding protein of 322 amino acids. Ligands of CRF-BP, such as CRF (6-33) can elevate brain levels of 'free' CRF and improve learning and memory without stress-like side effects of CRF receptor agonists. Urocortin, a mammalian CRF-related peptide with close sequence homology to fish urotensin, interacts with CRF1, CRF2 receptors and with CRF-BP. These data indicate that CRF receptor antagonists may be useful for the treatment of the disease states where CRF is elevated such as anxiety and depression, anorexia nervosa and stroke and that ligand inhibitors of CRF-BP may be used to elevate brain levels of 'free' urocortin and other CRF-related peptides.