Cholecystokinin-induced changes in polysome structure regulate protein synthesis in pancreas.
Translational regulation of digestive enzyme synthesis during short-term stimulation by cholecystokinin-octapeptide (CCK-OP), was examined in minced rabbit pancreas by measuring protein synthesis and monitoring alterations in the size of polysomes attached to the rough endoplasmic reticulum (RER). The effect of CCK-OP on protein synthesis was determined by measuring [3H]leucine incorporation into trichloroacetic-acid-precipitable proteins. Concentrations of CCK-OP that caused maximal enzyme secretion (10 and 30 nM) decreased protein synthesis by approx. 50% compared to control. Protein synthesis returned to the control level 60 min after terminating the action of CCK-OP. Autoradiography of [35S]methionine-labeled proteins separated by one-dimensional SDS-polyacrylamide gel electrophoresis demonstrated that CCK-OP reversibly inhibited the synthesis of all of the major groups of digestive enzymes. Northern blot analysis revealed that CCK-OP did not alter the cellular content of amylase and elastase mRNA. Incubation with CCK-OP caused a decrease in the size distribution of RER-bound polysomes. Polysome profiles returned to the control pattern 60 min following termination of the stimulus. These results suggest that the inhibitory effects of CCK-OP on the synthesis of digestive enzymes is regulated at translation by decreasing the number of RER-bound ribosomes that are actively translating digestive enzyme mRNA.
Perkins
P S
PS
Department of Medicine, Veterans Administration Medical Center, San Diego, California.
Pandol
S J
SJ
D000681:Amylases / Q000096:biosynthesis; D000818:Animals; D002766:Cholecystokinin / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D010179:Pancreas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010196:Pancreatic Elastase / Q000096:biosynthesis; D011132:Polyribosomes / Q000187:drug effects* / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000302:isolation & purification; D011817:Rabbits
D012333:RNA, Messenger; D002766:Cholecystokinin; D000681:Amylases; D010196:Pancreatic Elastase