The calcineurin-nuclear factor of activated T cells signaling pathway mediates the effect of corticotropin releasing factor and urocortins on catecholamine synthesis.

The biological effects of the Corticotropin-releasing factor (CRF) family of neuropeptides are mediated by mobilization of [Ca(2+)]. Aim of the current work was to examine if the calcineurin/NFAT (nuclear factor of activated T-cells) signaling pathway is involved in the effect of CRF peptides in catecholamine synthesis and secretion from PC12 rat pheochromocytona cells, a model for the study of adrenal catecholamine production. PC12 cells express both types of CRF receptors. Our data are as follows: (a) The calcineurin inhibitor cyclosporine A (CsA) blocked norepinephrine secretion induced by ligands of either CRF type 1 (CRF(1)) or 2 (CRF(2)) receptors on PC12 cells. (b) Silencing NFAT2 expression using a selective NFAT2 siRNA blocked CRF(1) and CRF(2) -induced NE production. (c) CRF ligands induced NFAT transcriptional activity in cells transfected with a luciferase reporter construct controlled by NFAT binding elements (NFAT-Luc). (d) CsA completely blocked the stimulatory effect of CRF(1) and CRF(2) ligands on NFAT activity in NFAT-Luc transfected cells. (e) PKA, PKC, p38-MAPK, Tpl2, Ha-Ras, and AKT1 were crucial intermediates for both CRF(1) and CRF(2)-induced NFAT activation. Interestingly, MEK1/2 and ERK1/2 were crucial only for the CRF(2)-induced NFAT activation. (f) p38-MAPK and Tpl2 were crucial intermediates for both CRF(1) and CRF(2)-induced norepinephrine production, while AKT1 affected only CRF(2)-induced norepinephrine production. In conclusion, our data suggest that CRF(1) and CRF(2) ligands activate the transcription factor NFAT and its activation is prerequisite for CRF-induced catecholamine production from chromaffin cells.