Cell type-specific requirement of the MAPK pathway for the growth factor action of gastrin.
Gastrin (G17) has a CCKB receptor-mediated growth-promoting effect on the AR42J rat acinar cell line that is linked to induction of both mitogen-activated protein kinase (MAPK) and c-fos gene expression. We investigated the mechanisms that regulate the growth factor action of G17 on the rat pituitary adenoma cell line GH3. Both AR42J and GH3 cells displayed equal levels of CCKB receptor expression and similar binding kinetics of 125I-labeled G17. G17 stimulation of cell proliferation was identical in both cell lines. G17 stimulation of GH3 cell proliferation was completely blocked by the CCKB receptor antagonist D2 but not by the MEK inhibitor PD-98059 or the protein kinase C inhibitor GF-109203X, which completely inhibited G17 induction of AR42J cell proliferation. G17 induced a c-fos SRE-luciferase reporter gene plasmid more than fourfold in the AR42J cells, whereas it had no effect in the GH3 cells. In contrast to what we observed in the AR42J cells, G17 failed to stimulate MAPK activation and Shc tyrosyl phosphorylation and association with the adapter protein Grb2. Epidermal growth factor induced the MAPK pathway in the GH3 cells, demonstrating the integrity of this signaling system. G17 induced Ca2+ mobilization in both the GH3 and AR42J cells. The calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide inhibited AR42J cell proliferation by 20%, whereas it completely blocked G17 induction of GH3 cell growth. The Ca2+ ionophore ionomycin stimulated GH3 cell proliferation to a level similar to that observed in response to G17, but it had no effect on AR42J cell proliferation. Thus there are cell type specific differences in the requirement of the MAPK pathway for the growth factor action of G17. Whereas in the AR42J cells G17 stimulates cell growth through activation of MAPK and c-fos gene expression, in the GH3 cells, G17 fails to activate MAPK, and it induces cell proliferation through Ca2+-dependent signaling pathways. Furthermore, induction of Ca2+ mobilization in the AR42J cells appears not to be sufficient to sustain cell proliferation.
Stepan
V M
VM
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
Dickinson
C J
CJ
del Valle
J
J
Matsushima
M
M
Todisco
A
A
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000236:Adenoma / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005755:Gastrins / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D006133:Growth Substances / Q000502:physiology*; D010179:Pancreas / Q000166:cytology / Q000378:metabolism / Q000503:physiopathology*; D010766:Phosphorylation; D010911:Pituitary Neoplasms / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D011493:Protein Kinase C / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D051381:Rats; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin / Q000378:metabolism / Q000502:physiology; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D005755:Gastrins; D006133:Growth Substances; D011506:Proteins; D016760:Proto-Oncogene Proteins c-fos; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases