Cholecystokinin peptides stimulate pancreatic secretion by multiple signal transduction pathways.
In an attempt to examine the structure-activity relationship of the cholecystokinin (CCK) peptide, we examined the structural motif of CCK truncated peptides responsible for rat pancreatic acinar amylase secretion and signal transduction. CCK-6 (Met28-Gly29-Trp30-Met31-Asp32-Phe33 -NH2), CCK-5 [CCK-(29-33)], and CCK-4 [CCK-(30-33)] caused monophasic amylase secretion with EC50 values of 3, 20, and 30 nM, respectively. CCK-7 [Tyr(SO3H)27 plus CCK-(28-33)] evoked biphasic secretion with an EC50 of 0.7 pM, whereas CCK-3 [CCK-(31-33)] had no effect, suggesting the importance of Tyr(SO3H)27 and Trp30. Whereas CCK-7 [Tyr(SO3H)27/ Met28] evoked biphasic amylase secretion, CCK-OPE [Tyr(SO3H)27/Nle28] and CCK-6 (Met28) caused monophasic secretion. Thus Tyr(SO3H)27/Met28 appears to be required for biphasic secretion. CCK-8-OH and CCK-5-OH did not cause amylase secretion and Ca2+ spiking, suggesting the importance of Phe33 amidation. Similar to CCK-8, CCK-6 and CCK-4 caused Ca2+ oscillations at low doses and large Ca2+ transients at high doses. In contrast, similar to JMV-180 and CCK-OPE, CCK-5 elicited Ca2+ oscillations at all concentrations. Phospholipase C (PLC) inhibitor inhibited amylase secretion induced by high doses of CCK-6 and CCK-4 but not by CCK-5. Protein tyrosine kinase (PTK) inhibitor only inhibited the action of high doses of CCK-4. Neither PLC inhibitor nor PTK inhibitor affected amylase secretion evoked by low doses of CCK-6, CCK-5, and CCK-4. In contrast to its actions on JMV-180 and CCK-OPE, phospholipase A2 (PLA2) inhibitor had no effect on the action evoked by all CCK short peptides. CCK-6, CCK-5, and CCK-4 caused a 2.1- to 3.2-fold increase in intracellular inositol 1,4,5-trisphosphate levels over basal. None of these CCK short peptides increased intracellular arachidonic acid levels. CCK-6 and CCK-5 did not stimulate PTK activity, whereas CCK-4 evoked a 3.2- to 5.3-fold increase over basal. We conclude that Tyr(SO3H)27, Trp30, and Phe33-CONH2 of the CCK peptide are key amino acids in evoking amylase secretion. At low doses, CCK-6, CCK-5, and CCK-4 utilize some yet to be identified pathways to evoke Ca2+ oscillations and amylase secretion. At high doses, CCK-6 and CCK-4 utilize PLC but not PLA2 pathways. CCK-4 possesses the minimal essential amino acids to fully activate the PTK pathway.
Yoshida
H
H
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109, USA.
Tsunoda
Y
Y
Owyang
C
C
D062365:Aminobenzoates / Q000494:pharmacology; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002723:Chlorobenzoates; D002766:Cholecystokinin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002934:Cinnamates / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010179:Pancreas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology*; D013758:Tetragastrin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D062367:ortho-Aminobenzoates
D062365:Aminobenzoates; D002723:Chlorobenzoates; D002934:Cinnamates; D004791:Enzyme Inhibitors; D004963:Estrenes; D010446:Peptide Fragments; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D062367:ortho-Aminobenzoates; D013758:Tetragastrin; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C067408:cholecystokinin (26-32), Tyr-Gly-Nle(28,31) phenethyl ester-; C058451:JMV 180; C049128:cholecystokinin pentapeptide; D002766:Cholecystokinin; C060048:2-(4-amylcinnamoyl)amino-4-chlorobenzoic acid; D010738:Type C Phospholipases; D000681:Amylases; D012844:Sincalide; D002118:Calcium