Pituitary adenylate-cyclase-activating polypeptide stimulates proto-oncogene expression and activates the AP-1 (c-Fos/c-Jun) transcription factor in AR4-2J pancreatic carcinoma cells.
Pituitary adenylate-cyclase-activating polypeptide (PACAP) has been shown to possess mitogenic activity in various tumor cells. The present study was designed to investigate signal transduction mechanisms and expression of the proto-oncogenes c-fos and c-jun linked to the mitogenic effect of PACAP in the pancreatic carcinoma cell line AR4-2J. PACAP-(1-27)-peptide and PACAP-(1-38)-peptide, but not the structurally related vasoactive intestinal polypeptide (VIP), potently stimulated [3H]thymidine incorporation and cell number at doses of 0.1-10 nM. Both molecular forms of PACAP strongly increased formation of cAMP and inositol trisphosphate, elevated cytosolic Ca2+ levels and induced mitogen-activated protein (MAP) kinase activity. Quantitative reverse-transcription PCR revealed that PACAP-(1-27)-peptide and PACAP-(1-38)-peptide elevated c-fos mRNA levels 50-100-fold, whereas c-jun mRNA levels increased only moderately (2-3-fold). The effect of PACAP on c-fos and c-jun expression in AR4-2J cells was rapid (20 min), transient (1-2 h), dose-dependent IC50, 0.5 nM) and was abolished by the specific PACAP receptor antagonist PACAP-(6-38)-peptide or inhibitors of protein kinase C or tyrosine kinases. Compared with PACAP, epidermal growth factor and gastrin equipotently stimulated c-fos transcription whereas VIP, secretin, forskolin or phorbolester showed only marginal effects. Both PACAP (1-27)-peptide and PACAP-(1-38)-peptide strongly increased the DNA binding activity of the c-fos/ c-jun heterodimer transcription factor AP-1 at 10 nM and also stimulated AP-1 transcriptional activity up to 20-fold in AR4-2J cells. These findings indicate that the mitogenic effect of PACAP mediated via activation of the GTP-binding protein coupled PACAP/VIP-1 (PV1) receptor is linked to the MAP kinase cascade, increased expression of the proto-oncogenes c-fos and c-jun and activation of the heterodimeric transcription factor AP-1.
Schäfer
H
H
1st Department of Medicine, Christian-Albrechts University, Kiel, Germany.
Zheng
J
J
Gundlach
F
F
Günther
R
R
Siegel
E G
EG
Fölsch
U R
UR
Schmidt
W E
WE
D000818:Animals; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002453:Cell Cycle; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D016762:Genes, fos; D016758:Genes, jun; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008934:Mitogens; D009479:Neuropeptides / Q000502:physiology*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*
C495403:Adcyap1 protein, rat; D004791:Enzyme Inhibitors; D008934:Mitogens; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D013449:Sulfonamides; D018808:Transcription Factor AP-1; C017967:W 7; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium