Raf-1 Kinase Inhibitory Protein (RKIP) Mediates Ethanol-induced Sensitization of Secretagogue Signaling in Pancreatic Acinar Cells

• Published in: The Journal of biological chemistry 2012-09, Vol.287 (40), p.33377-33388
• Main Authors: Kim, Sung Ok, Ives, Kirk L., Wang, Xiaofu, Davey, Robert A., Chao, Celia, Hellmich, Mark R.
• Format: Article
• Language: English
• Subjects: Acinar Cells - cytology; Adenosine Triphosphate - metabolism; Animals; ATP; Binding Sites; Calcium - metabolism; Cell Line; Central Nervous System Depressants - pharmacology; Chymotrypsin - chemistry; Ethanol; Ethanol - pharmacology; Extracellular Matrix; Extracellular Matrix - metabolism; G Protein-coupled Receptor; Inflammation; Mice; Pancreas; Pancreas - metabolism; Pancreatitis - chemically induced; Pancreatitis - prevention & control; Phosphatidylethanolamine Binding Protein - genetics; Phosphatidylethanolamine Binding Protein - physiology; Phosphorylation; Protein Kinase C - metabolism; Raf; Raf Kinase Inhibitory Protein; Rats; Receptors, G-Protein-Coupled - metabolism; Risk; Signal Transduction
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.367656

Excessive alcohol consumption is associated with most cases of chronic pancreatitis, a progressive necrotizing inflammatory disease that can result in pancreatic insufficiency due to acinar atrophy and fibrosis and an increased risk of pancreatic cancer. At a cellular level acute alcohol exposure can sensitize pancreatic acinar cells to secretagogue stimulation, resulting in dysregulation of intracellular Ca2+ homeostasis and premature digestive enzyme activation; however, the molecular mechanisms by which ethanol exerts these toxic effects have remained undefined. In this study we identify Raf-1 kinase inhibitory protein as an essential mediator of ethanol-induced sensitization of cholecystokinin- and carbachol-regulated Ca2+ signaling in pancreatic acinar cells. We show that exposure of rodent acinar cells to ethanol induces protein kinase C-dependent Raf-1 kinase inhibitory protein phosphorylation, sensitization of cholecystokinin-stimulated Ca2+ signaling, and potentiation of both basal and cholecystokinin-stimulated extracellular signal-regulated kinase activation. Furthermore, we show that either suppression of Raf-1 kinase inhibitory protein expression using short hairpin RNA or gene ablation prevented the sensitizing effects of ethanol on cholecystokinin- and carbachol-stimulated Ca2+ signaling and intracellular chymotrypsin activation in pancreatic acinar cells, suggesting that the modulation of Raf-1 inhibitory protein expression may have future therapeutic utility in the prevention or treatment of alcohol-associated pancreatitis. Background: The molecular mechanism by which ethanol (EtOH) sensitizes pancreatic acinar cells to secretagogue stimulation is largely undefined. Results: Ethanol stimulates PKC-dependent RKIP phosphorylation, and RKIP ablation prevents EtOH-induced sensitization of secretagogue Ca2+ signaling and aberrant chymotrypsin activation. Conclusion: RKIP mediates the cytotoxic effects of EtOH on pancreatic acinar cells. Significance: Modulation of RKIP expression may have therapeutic utility in the prevention or treatment of alcohol-associated pancreatitis.