title: Phosphorylation of eIF2α is dispensable for differentiation but required at a posttranscriptional level for paneth cell function and intestinal homeostasis in mice.
abstract: BACKGROUND
  Recent studies link endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) to inflammatory bowel disease. Altered eIF2α phosphorylation (eIF2α-P), a regulatory hub of the UPR, was observed in mucosal tissue of patients with inflammatory bowel disease. In this study, we examined the mechanistic role of eIF2α-P in intestinal epithelial cell (IEC) function and intestinal homeostasis in mice.
  
  
  METHODS
  We generated mice with villin-Cre-mediated conditional expression of nonphosphorylatable Ser51Ala mutant eIF2α in IECs (AA mice). We analyzed AA mice under normal conditions and on challenge with oral infection of Salmonella Typhimurium or dextran sulfate sodium-induced colitis.
  
  
  RESULTS
  Loss of eIF2α-P did not affect the normal proliferation or differentiation of IECs. However, AA mice expressed decreased secretory proteins including lysozyme, suggesting eIF2α-P is required for Paneth cell function. The ultrastructure of AA Paneth cells exhibited a reduced number of secretory granules, a fragmented ER, and distended mitochondria under normal conditions. UPR gene expression was defective in AA IECs. Translation of Paneth cell specific messenger RNAs encoding lysozyme and cryptidins was significantly defective leading to the observed granule-deficient phenotype, which was associated with reduced ribosomal recruitment of these messenger RNAs to the ER membrane. Consequently, AA mice were more susceptible to oral Salmonella infection and dextran sulfate sodium-induced colitis.
  
  
  CONCLUSIONS
  We conclude eIF2α phosphorylation is required for the normal function of intestinal Paneth cells and mucosal homeostasis by activating UPR signaling and promoting messenger RNA recruitment to the ER membrane for translation.
authors.affiliation: *Del E. Webb Neuroscience, Aging and Stem Cell Research Center, Sanford Burnham Medical Research Institute, La Jolla, California; †Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan; and ‡Department of Medicine, University of California San Diego, La Jolla, California. Dr. Cao is now with Columbia University College of Physicians and Surgeons, New York, New York. Dr. Harrington is now with Medical University of the Americas, Charlestown, Nevis, West Indies.
authors.forename: Stewart S
authors.initials: SS
authors.lastname: Cao
authors.forename: Miao
authors.initials: M
authors.lastname: Wang
authors.forename: Jane C
authors.initials: JC
authors.lastname: Harrington
authors.forename: Brandy-Mengchieh
authors.initials: BM
authors.lastname: Chuang
authors.forename: Lars
authors.initials: L
authors.lastname: Eckmann
authors.forename: Randal J
authors.initials: RJ
authors.lastname: Kaufman
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D049109:Cell Proliferation; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism; D016264:Dextran Sulfate; D004198:Disease Susceptibility; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis; D007371:Interferon-gamma / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D018832:Molecular Chaperones; D009113:Muramidase / Q000096:biosynthesis* / Q000235:genetics; D019879:Paneth Cells / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure*; D010766:Phosphorylation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012270:Ribosomes / Q000502:physiology; D012481:Salmonella Infections, Animal / Q000276:immunology; D022142:Secretory Vesicles / Q000648:ultrastructure; D015398:Signal Transduction; D013312:Stress, Physiological; D056811:Unfolded Protein Response / Q000235:genetics
chemical_list: D015852:Eukaryotic Initiation Factor-2; D018832:Molecular Chaperones; D012333:RNA, Messenger; D007371:Interferon-gamma; D016264:Dextran Sulfate; D009113:Muramidase