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[Cholecystokinin stimulates peptide chain elongation in mouse pancreatic acini and its molecular mechanism].

OBJECTIVE
To investigate cholecystokinin (CCK), carbachol, and vasoactive intestinal peptide (VIP) stimulating peptide chain elongation in mouse pancreatic acini in vitro and its molecular mechanism.


METHODS
(3)H-lecucine incorporation assay was used to measure the basal and secretagogues-stimulated pancreatic acini elongation rates. Western blot was applied to analyse the effect of phosphorylation of the elongation factor 2 (eEF2) and the eEF2 kinase. MEK inhibitor (PD98059), SAPK/p38 inhibitor (SB202190), and mTOR inhibitor (rapamycin) were used to respectively block MEK, SAPK/p38, and mTOR intracellular pathways or the phosphatase inhibitor (calyculin A) pretreatment before CCK treatment.


RESULTS
All secretagogues except VIP increased the peptide chain elongation in mouse pancreatic acini in vitro. All secretagogues except VIP inhibited the phosphorylation level of eEF2 on Thr-56 and increased the phosphorylation level of eEF2K on Ser-366, which might correlate with their activation status. MEK inhibitor PD98059 partially reversed the dephosphorylation of eEF2 induced by CCK, as did treatment p38 MAPK inhibitor SB202190, mTOR inhibitor rapamycin, and the phosphatase inhibitor calyculin A.


CONCLUSION
CCK increases peptide chain elongation via inducement of dephosphorylation of eEF2 and eEF2 kinase phosphorylation in pancreatic acini in vitro. CCK-induced dephosphorylation of eEF2 in pancreatic acinar cells involves MEK, SAPK/p38, and mTOR, the three intracellular pathways.