Differential activation of p42ERK2 and p125FAK by cholecystokinin and bombesin in the secretion and proliferation of the pancreatic amphicrine cell line AR42J.
BACKGROUND
AR42J rat pancreatic acinar carcinoma cells have retained the potential to secrete digestive enzymes in addition to their ability to proliferate upon stimulation with regulatory peptides. We investigated the involvement of p42ERK2 and p125FAK (extracellular signal-regulated protein kinase and focal adhesion protein kinase, respectively) by cholecystokinin and bombesin stimulation with regard to secretion and mitogenesis.


METHODS
The p42ERK2 activity was measured by kinase assay and the activation of p125FAK by antiphosphotyrosine Western blot analysis of p125FAK immunoprecipitates. The expression of both kinases was determined by Western blot analysis, the amylase secretion by colorimetry, and the DNA synthesis by [3H]thymidine incorporation.


RESULTS
p42ERK2 and p125FAK were activated by cholecystokinin and bombesin with maximum stimulation at concentrations above 10 nM. Bombesin was a weaker activator of p42ERK2 and p125FAK, causing only half of the kinase activity induced by stimulation with cholecystokinin. PD98059 was shown to inhibit p42ERK2, while tyrphostin 25 blocked p125FAK tyrosine phosphorylation. Preincubation of AR42J cells with PD98059 or tyrphostin 25 was without influence on cholecystokinin- or bombesin-stimulated secretion in normal or 72-hour dexamethasone-pretreated cells. In contrast, inhibition of both protein kinases leads to reduced cholecystokinin-stimulated [3H]thymidine incorporation rates.


CONCLUSIONS
Cholecystokinin induced proliferation of AR42J cells by strong activation of p42ERK2 and p125FAK. Bombesin failed to stimulate DNA synthesis, probably due to its reduced potency to stimulate these kinases. Both protein kinases are not implicated in the process of enzyme secretion.
1st Department of Internal Medicine, Christian Albrechts University, Schittenhelmstrasse 12, D-24105 Kiel, Germany. kkiehne@1med.uni-kiel.de
Karlheinz
K
Kiehne
Karl H
KH
Herzig
Ulrich R
UR
Fölsch
D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002766:Cholecystokinin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D010190:Pancreatic Neoplasms; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D004791:Enzyme Inhibitors; D005419:Flavonoids; D002766:Cholecystokinin; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat; D019950:Mitogen-Activated Protein Kinase 1; D001839:Bombesin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one