Gastrin induces c- fos gene transcription via multiple signaling pathways

• Published in: American journal of physiology: Gastrointestinal and liver physiology 1999-02, Vol.276 (2), p.G415-G424
• Main Authors: Stepan, Vinzenz M., Tatewaki, Makoto, Matsushima, Masashi, Dickinson, Chris J., del Valle, John, Todisco, Andrea
• Format: Article
• Language: English
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.1999.276.2.G415

We previously observed that the trophic actions of gastrin (G17) on the AR42J rat acinar cell line are mediated by mitogen-activated protein kinase (MAPK)-induced c- fos gene transcription via protein kinase C (PKC)-dependent and -independent pathways. In this study, we further investigated the signaling pathways that target c- fos in response to G17. G17 led to a sixfold induction in luciferase activity in cells transfected with plasmids containing the −356+109 sequence of the murine c- fos promoter, which includes the Sis-inducible element (SIE), serum response element (SRE), and the Ca 2+ /cAMP response element (CRE) regulatory elements. Addition of either the selective PKC inhibitor GF-109203X or the MAPK/extracellular signal-regulated kinase inhibitor PD-98059 resulted in an 80% reduction in luciferase activity. G17 induced the transcriptional activity of both Elk-1 and Sap-1a, transcription factors that bind to the E26 transformation specific (Ets) DNA sequence of the SRE, and this effect was inhibited by both GF-109203X and PD-98059. Point mutations in the Ets sequence led to a 4-fold induction of c- fos transcription stimulated by G17 and to a 1.3-fold induction in response to epidermal growth factor (EGF). In contrast, mutations in the CA rich G (CArG) sequence of the SRE prevented transcriptional activation by both G17 and EGF. G17 induction of the Ets mutant construct was unaffected by either GF-109203X or PD-98059. Because activation of the SRE involves the small GTP-binding protein Rho A, we examined the role of Rho A in G17 induction of c- fos transcription. Inactivation of Rho A by either the specific inhibitor C3 or by expression of a dominant negative Rho A gene inhibited G17 induction of both the wild-type and the Ets mutant constructs by 60%. C3 also inhibited G17-stimulated AR42J cell proliferation. Thus G17 targets the c- fos promoter CArG sequence via Rho A-dependent pathways, and Rho A appears to play an important role in the regulation of the trophic action of G17.