We have previously shown that Corticotropin releasing factor (CRF) and Urocortins (UCNs) induce the production of catecholamines from normal human and rat adrenal chromaffin and PC12 pheochomocytoma cells via induction of tyrosine hydroxylase, the rate limiting enzyme of catecholamine biosynthesis. We have also shown that CRF induces calcium ion entrance into the cytoplasm from both extracellular sources (influx) and from intracellular stores (mobilization) in PC12 cells. The transcription factor NFAT (Nuclear Factor of Activated T cells) is activated by calcium, is expressed in neuronal tissues and in PC12 cells, and is involved in neuronal cell differentiation. No information is available on its role in chromaffin cells. In the present study we have examined the effect of CRF peptides on NFAT activation, its role on catecholamine production in the PC12 pheochromocytoma cell line and the signaling pathways involved.
Our data demonstrate that: (a) CRF, UCN1 (CRF1 and CRF2 receptor agonists), UCN2, UCN3 (preferential CRF2 receptor agonists) or Cortagine (synthetic CRF1 receptor agonist) induced NFAT activity in a statistical significant manner in PC12 cells. (b) Cyclosporine A (CsA), a Calcineurin/NFAT inhibitor, abolished UCN2 or Cortagine-induced NFAT transcriptional activity in PC12 cells. (c) The effect of CRF receptor agonists on catecholamine synthesis was abolished by CsA in PC12 cells. In conclusion, our data suggest that CRF and UCNs activate the transcription factor NFAT which appears to be essential for catecholamine synthesis.