Cyclic AMP analogs induce synthesis, processing, and secretion of prepro nociceptin orphanin FQ-derived peptides by NS20Y neuroblastoma cells

Recent studies have shown that cAMP analogs can induce expression of prepro (pp) orphanin FA (OFQ)/nociceptin-related gene products in NS20Y mouse neu roblastoma cells (Saito et al, [1996], J Biol Chem 271., 15615-15622), Addi tionally, exposure of NS20Y cells to cAMP analogs promoted neurite outgrowt h and large dense-core vesicle formation. Even though an OFQ-like precursor (called 27K) was identified in NS20Y cell extracts, no secretion of OFQ-re lated peptides was detected. We have used reversed-phase high-performance l iquid chromatography combined with a specific radioimmunoassay for OFQ(1-17 ) to determine if NS20Y cells secrete ppOFQ-derived peptides when stimulate d by the cAMP analog ctp-cAMP, We found that NS20Y cells secreted abundant amounts of OFQ-derived products when stimulated by cAMP analogs. We also ha ve determined that secretion of OFQ peptides was both time and concentratio n dependent and reversible on removal of cAMP analogs from the culture medi um. In addition, the opioid agonist D-Pen(2)-D-Pen(5)-enkephalin inhibited forskolin-stimulated OFQ peptide secretion. Further, the synthetic glucocor ticoid virtually abolished ctp-cAMP-stimulated OFQ peptide secretion. These results suggest that the processing, and secretion of the OFQ neuropeptide transmitter system can be modulated through lar cAMP levels and that these functions are regulated by opioids and molecules involved in mediating str ess response. The NS20Y cell system will be extremely valuable for studying the regulation of peptides by a variety of intra-cellular and extracellula r signaling pathways.