Rat cerebral cortex corticotropin-releasing hormone receptors: evidence for receptor coupling to multiple G-proteins

The wide distribution of corticotrophin-releasing hormone (CRH) receptors i n brain and periphery appear to be important in integrating the responses o f the brain, endocrine and immune systems to physiological, psychological a nd immunological stimuli. The type 1 receptors are highly expressed through out the cerebral cortex, a region involved in cognitive function and modula tion of stress responses, where they are coupled to the adenylyl cyclase sy stem. Using techniques that analyse receptor-mediated guanine-nucleotide bi nding protein (G-proteins) activation, we recently demonstrated that expres sed type 1 alpha CRH receptors are capable of activating multiple G-protein s, which suggests that CRH can regulate multiple signalling pathways. in an effort to characterize the intracellular signals generated by CRH in the r at cerebral cortex we sought to identify G-proteins activated by CRH in a p hysiological membrane environment. Rat cerebral cortical membrane suspensio ns were analysed for the ability of CRH to stimulate incorporation of [alph a-P-32]-GTP-gamma -azidoanilide to Various G-protein alpha -chains. Our res ults show that CRH receptors are coupled to and activate at least five diff erent G-proteins (Gs, Gi, Gq(/11), Go and Gz) with subsequent stimulation o f at feast two intracellular signalling cascades. In addition, the photoaff inity experiments indicated that the CRH receptors preferentially activate the 45 kDa form of the Gs alpha -protein. This data may help elucidate the intracellular signalling pathways mediating the multiple actions of CRH esp ecially under different physiological conditions.