Secretagogues differentially activate endoplasmic reticulum stress responses in pancreatic acinar cells.
Endoplasmic reticulum (ER) stress leads to the accumulation of misfolded proteins in the ER lumen and initiates the unfolded protein response (UPR). Components of the UPR are important in pancreatic development, and recent studies have indicated that the UPR is activated in the arginine model of acute pancreatitis. However, the effects of secretagogues on UPR components in the pancreas are unknown. The present study aimed to examine the effects of different types and concentrations of secretagogues on acinar cell function and specific components of the UPR. Rat pancreatic acini were stimulated with the CCK analogs CCK8 (10 pM-10 nM) or JMV-180 (10 nM-10 microM) or with bombesin (1-100 nM). Components of the UPR, including chaperone BiP expression, PKR-like ER kinase (PERK) phosphorylation, X box-binding protein 1 (XBP1) splicing, and CCAAT/enhancer binding protein homologous protein (CHOP) expression, were measured, as were effects on amylase secretion and intracellular trypsin activation. CCK8 generated a biphasic secretion dose-response curve, and high concentrations increased intracellular active trypsin levels. In contrast, JMV-180 and bombesin secretion dose-response curves were monophasic, and high concentrations did not increase intracellular trypsin activity. All three secretagogues increased BiP levels and XBP1 splicing. However, only supraphysiological levels of CCK8 associated with inhibited amylase secretion and trypsin activation stimulated PERK phosphorylation and expression of CHOP. The effects of CCK8 on UPR components were rapid, occurring within 5-20 min. In conclusion, ER stress response mechanisms appear to be involved in both pancreatic physiology and pathophysiology, and future efforts should be directed at understanding the roles of these mechanisms in the pancreas.
Kubisch
Constanze H
CH
The Univ. of Texas M. D. Anderson Cancer Center, Dept. of Cancer Biology, Unit 0953, SCRB2.2021, 7435 Fannin St., PO Box 301429, Houston, TX 77230-1429, USA.
Logsdon
Craig D
CD
D000681:Amylases / Q000378:metabolism; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D001839:Bombesin / Q000494:pharmacology*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation; D006360:Heat-Shock Proteins / Q000378:metabolism; D008297:Male; D018832:Molecular Chaperones / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D046790:Pancreas, Exocrine / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D017510:Protein Folding; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071701:Regulatory Factor X Transcription Factors; D015398:Signal Transduction / Q000187:drug effects*; D012844:Sincalide / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D013312:Stress, Physiological / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D014357:Trypsin / Q000378:metabolism; D014362:Trypsinogen / Q000378:metabolism; D000071717:X-Box Binding Protein 1; D019892:eIF-2 Kinase / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP
D000681:Amylases; D050976:Basic-Leucine Zipper Transcription Factors; D001839:Bombesin; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D012844:Sincalide; D051742:Transcription Factor CHOP; D014157:Transcription Factors; D014357:Trypsin; D014362:Trypsinogen; D000071717:X-Box Binding Protein 1; D019892:eIF-2 Kinase; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; C000605545:Xbp1 protein, rat; C058451:JMV 180