Molecular mechanisms for the growth factor action of gastrin

Abstract

We have previously observed that gastrin has a cholecystokinin B (CCK-B) receptor-mediated growth-promoting effect on the AR42J rat pancreatic acinar cell line and that this effect is paralleled by induction of expression of the early response gene c- fos. We undertook these experiments to elucidate the mechanism for induction of c- fos and the linkage of this action to the trophic effects of gastrin. Gastrin (0.1–10 nM) dose dependently induced luciferase activity in AR42J cells transfected with a construct consisting of a luciferase reporter gene coupled to the serum response element (SRE) of the c- fos promoter. This effect was blocked by the specific CCK-B receptor antagonist D2 but not by the specific CCK-A receptor antagonist L-364,718 or by pertussis toxin, indicating that gastrin targets the SRE via specific CCK-B receptors through a mechanism independent of Gi. Inhibition of protein kinase C (PKC) either by prolonged (24 h) exposure of the cells to the phorbol ester 12- O-tetradecanoylphorbol 13-acetate (100 nM) or by incubation with the selective inhibitor GF-109203X (3.5 μM) resulted in an 80% reduction in luciferase activity. Similar results were observed in the presence of the specific extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor PD-98059 (50 μM). We measured ERK2 activity in AR42J cells via in-gel kinase assays and observed that gastrin (1 pM-100 nM) induced ERK2 enzyme activity in a dose-dependent manner. Addition of GF-109203X and PD-98059, either alone or in combination, produced, respectively, partial and total inhibition of gastrin-induced ERK2 activity. Gastrin induction of ERK2 activity also resulted in a threefold increase in the transcriptional activity of Elk-1, a factor known to bind to the c- fos SRE and to be phosphorylated and activated by ERK2. PD-98059 blocked the growth-promoting effect of gastrin on the AR42J cells, demonstrating that this effect depends on activation of MEK. Our data lead us to conclude that the trophic actions of gastrin are mediated by ERK2-induced c- fos gene expression via PKC-dependent and -independent pathways.

Glycine-extended gastrin inhibits apoptosis in Barrett's oesophageal and oesophageal adenocarcinoma cells through JAK2/STAT3 activation

“…However, much less is known of the intracellular mechanisms mediating the effects of G-Gly, probably related to lack of identification of a specific receptor. Proliferative and anti-apoptotic responses to amidated gastrin are mediated via the classical gastrin CCK 2 receptor (CCK 2 R) and activation of various signalling pathways (including Ca CC , extra-cellular signal-related kinase and Akt) (Todisco et al 1997 and at least some of the responses to progastrin are mediated via binding to annexin II and subsequent activation of the canonical nuclear factor-kB (NF-kB) pathway (Rengifo-Cam et al 2007). By contrast, much less is known about G-Gly induced signalling.…”

Transgenic expression of CCK2 receptors sensitizes murine pancreatic acinar cells to carcinogen‐induced preneoplastic lesions formation

“…They activate many intracellular mediators classically described in the regulation of mitogenesis by growth factors. 3 Mitogen-activated protein kinases, ERK1/2, Jun kinase and p38MAPK, as well as the phosphatidylinositol 3-kinase (PI3K) and early responsive genes (c-fos, c-myc and c-jun), are known targets of gastrin. [4][5][6][7] Several groups including ours, have documented the contribution of Src and focal adhesion kinase (Fak) families' tyrosine kinases upstream the activation of these pathways.…”

Characterization of gastrin-cholecystokinin 2 receptor interaction in relation to c-fos induction

“…The parental cell line AR42J was known to respond to gastrin-17 administration with induction of the c-fos promoter (Todisco et al 1997, Stepan et al 1999, Thommesen et al 2001. The cells were cultured in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum (FBS) in 5% CO 2 .…”