Molecular cloning of c-jun and c-fos cDNAs from porcine anterior pituitary and their involvement in gonadotropin-releasing hormone stimulation

The presence of the typical transcription factors c-Jun, c-Fos and cAMP-responsive element (CRE)-binding protein in the porcine anterior pituitary was examined by molecular cloning and their involvement in the membrane signal cascade, especially their roles in gonadotropin-releasing hormone (GnRH) stimulation, were studied. Several cDNA clones were isolated from a porcine anterior pituitary cDNA library using cDNA probes. They were identified as porcine c-jun and c-fos by determining their nucleotide sequences, but a homologue for CREB341 which is a member of CRE-binding protein was not detected in porcine anterior pituitary. Reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed to estimate the c-jun and c-fos mRNA contents in GnRH-, forskolin- (cAMP activator) and tetradecanoyl phorbol acetate- (TPA; protein kinase C activator) treated primary cultures of porcine anterior pituitary cells. Densitometric quantification demonstrated that GnRH and TPA treatment increased c-jun and c-fos mRNA levels significantly, whereas forskolin reduced the levels of both. Therefore, c-Jun and c-Fos are definitely present in porcine anterior pituitary and their mRNAs differentially involved in the signal transduction pathway mediated by two kinases. In particular, GnRH might regulate gonadotropin expression by increasing of c-jun and c-fos levels.