Expression of novel neurotrophin-1/B-cell stimulating factor-3 (NNT-1/BSF-3) in murine pituitary folliculostellate TtT/GF cells: Pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-induced stimulation of NNT-1/BSF-3 is mediated by protein kinase A, protein kinase C, and extracellular-signal-regulated kinase1/2 pathways

Novel neurotrophin- 1/ B cell stimulating factor- 3 ( NNT- 1/ BSF- 3) is a gp130 cytokine potently stimulating corticotroph proopiomelanocortin gene expression and ACTH secretion by a Janus kinase- signal transducer and activator of transcription ( JAK- STAT)- dependent mechanism. In the current study, we examined the regulation of NNT- 1/ BSF- 3mRNA expression in murine pituitary folliculostellate TtT/ GF cells using Northern blot technique. A 5- to 9- fold and a 4- to 7- fold induction in NNT- 1/ BSF- 3 mRNA expression was observed between 2 and 6 h stimulation with the protein kinase C( PKC) stimulus phorbol-12- myristate- 13- acetate ( 100 nM) and the protein kinase A ( PKA) stimulus Bu(2)cAMP ( 5 mM), respectively. Pituitary adenylate cyclase- activating polypeptide ( PACAP- 38, 50 nM) and vasoactive intestinal peptide ( VIP, 50 nM) also stimulated NNT- 1/ BSF- 3 mRNA expression 5- to 9- fold between 2 and 6 h. Preincubation with PKC and PKA inhibitors such as H- 7 ( 20 mu M), GF109203X ( 50 mu M), and H- 89 ( 50 mu M) decreased the stimulatory effects of PACAP and VIP. Both PACAP- 38 and VIP also rapidly induced ERK1/ 2 phosphorylation and their stimulatory effect on NNT- 1/ BSF- 3 mRNA expression was reduced by the MAPK kinase/ ERK kinase ( MEK) inhibitor U0126 ( 10 mu M). Dexamethasone ( 10(-7) M) was a potent inhibitor of phorbol-12- myristate- 13- acetate- induced NNT- 1/ BSF- 3 expression. RT- PCR analysis demonstrated TtT/ GF cells to express the short and the hop variant but not the hip variant of the PACAP- 1 receptor ( PAC1- R). In addition, TtT/ GF cells express the VIP/ PACAP- 2 receptor ( VPAC2- R). In summary, NNT- 1/ BSF- 3 is expressed in pituitary folliculostellate TtT/ GF cells and induced by PKC-, PKA-, and ERK1/ 2- dependent mechanisms. The novel gp130 cytokine NNT- 1/ BSF- 3 derived from folliculostellate cells might act as a paracrine neuroimmunoendocrine modulator of pituitary corticotroph function.