title: RCAD/BiP pathway is necessary for the proper synthesis of digestive enzymes and secretory function of the exocrine pancreas.
abstract: Alcoholism causes an imbalance of endoplasmic reticulum (ER) homeostasis in pancreatic acini. In those cells, the ER is involved in the synthesis and folding of pancreatic enzymes. Ubiquitin-fold modifier 1 (Ufm1) is part of a novel ubiquitin-like modification system involved in maintaining ER homeostasis. Among the components of the Ufm1 system, Regulator of C53 and DDRGK1 (RCAD) has recently been identified as a Ufm1-specific E3 ligase that promotes ufmylation of DDRGK1, an RCAD-interacting protein. We determined the importance of RCAD in the proper synthesis and secretion of pancreatic enzymes using mice with genetically deleted RCAD. The pancreas of RCAD-deficient mice was of normal size and histology. Using quantitative PCR and Western blotting, we found that amylase was upregulated in pancreas organs from RCAD-knockout (KO) mice. Constitutive amylase secretion was much higher in isolated pancreatic acini from RCAD KO mice, whereas CCK-stimulated amylase secretion was disturbed. RCAD deficiency caused a downregulation in expression of ER chaperone BiP, which affected ER homeostasis and activated both apoptosis and trypsin. We also found that both RCAD and DDRGK1 transcript levels were upregulated in pancreatic acini from alcohol-preferring rats. Elevated expression of RCAD and DDRGK1 was associated with increased ER stress and UPR activation. Because of the lack of BiP expression, caspase 3 and trypsin activation we enhanced in RCAD-deficient pancreatic acini upon treatment with ethanol and CCK. In conclusion, the RCAD/BiP pathway is required for proper synthesis and secretion of pancreatic enzymes. In alcoholism, increased levels of components of the Ufm1 system could prevent the deleterious effects of alcohol in the pancreas by regulating BiP levels.NEW & NOTEWORTHYRCAD/BiP pathway is required for the proper synthesis and secretion of amylase from pancreatic acini, as well as for the maintenance of the ER homeostasis. In alcoholism, the exocrine pancreas could increase the levels of components of the Ufm1 system to protect itself from alcohol's deleterious effects by regulating the expression of ER chaperone BiP.
authors.affiliation: Department of Biological Sciences, Augusta University, Augusta, Georgia.
authors.forename: Camille
authors.initials: C
authors.lastname: Miller
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Georgia, Cancer Center, Augusta University, Augusta, Georgia; and.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Department of Psychological Sciences, Augusta University, Augusta, Georgia.
authors.forename: Tadd
authors.initials: T
authors.lastname: Patton
authors.affiliation: Department of Biological Sciences, Augusta University, Augusta, Georgia.
authors.forename: Sarai Hacker
authors.initials: SH
authors.lastname: Graves
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Georgia, Cancer Center, Augusta University, Augusta, Georgia; and.
authors.forename: Honglin
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Biological Sciences, Augusta University, Augusta, Georgia; msabbatini@augusta.edu.
authors.forename: Maria Eugenia
authors.initials: ME
authors.lastname: Sabbatini
mesh_terms: D061354:Acinar Cells / Q000378:metabolism*; D000437:Alcoholism / Q000378:metabolism; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D046790:Pancreas, Exocrine / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014357:Trypsin / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D015820:Cadherins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; C083970:R-cadherin; D000681:Amylases; D014357:Trypsin; D053148:Caspase 3
keywords: BiP; DDRGK1; RCAD; pancreatic acini; ufmylation