Feedback inhibition of the unfolded protein response by GADD34-mediated dephosphorylation of eIF2alpha.
Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) on serine 51 integrates general translation repression with activation of stress-inducible genes such as ATF4, CHOP, and BiP in the unfolded protein response. We sought to identify new genes active in this phospho-eIF2alpha-dependent signaling pathway by screening a library of recombinant retroviruses for clones that inhibit the expression of a CHOP::GFP reporter. A retrovirus encoding the COOH terminus of growth arrest and DNA damage gene (GADD)34, also known as MYD116 (Fornace, A.J., D.W. Neibert, M.C. Hollander, J.D. Luethy, M. Papathanasiou, J. Fragoli, and N.J. Holbrook. 1989. Mol. Cell. Biol. 9:4196-4203; Lord K.A., B. Hoffman-Lieberman, and D.A. Lieberman. 1990. Nucleic Acid Res. 18:2823), was isolated and found to attenuate CHOP (also known as GADD153) activation by both protein malfolding in the endoplasmic reticulum, and amino acid deprivation. Despite normal activity of the cognate stress-inducible eIF2alpha kinases PERK (also known as PEK) and GCN2, phospho-eIF2alpha levels were markedly diminished in GADD34-overexpressing cells. GADD34 formed a complex with the catalytic subunit of protein phosphatase 1 (PP1c) that specifically promoted the dephosphorylation of eIF2alpha in vitro. Mutations that interfered with the interaction with PP1c prevented the dephosphorylation of eIF2alpha and blocked attenuation of CHOP by GADD34. Expression of GADD34 is stress dependent, and was absent in PERK(-)/- and GCN2(-)/- cells. These findings implicate GADD34-mediated dephosphorylation of eIF2alpha in a negative feedback loop that inhibits stress-induced gene expression, and that might promote recovery from translational inhibition in the unfolded protein response.
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Skirball Institute of Biomolecular Medicine, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
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Harding
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D051701:Activating Transcription Factor 4; D000818:Animals; D000943:Antigens, Differentiation; D022762:CCAAT-Enhancer-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism; D020134:Catalytic Domain; D018797:Cell Cycle Proteins; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D005246:Feedback; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins; D051379:Mice; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D039881:Prokaryotic Initiation Factor-2; D011485:Protein Binding; D014176:Protein Biosynthesis; D011489:Protein Denaturation; D017510:Protein Folding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism
D051701:Activating Transcription Factor 4; D000943:Antigens, Differentiation; D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010448:Peptide Initiation Factors; D010749:Phosphoprotein Phosphatases; D039881:Prokaryotic Initiation Factor-2; D011494:Protein Kinases; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D012333:RNA, Messenger; D051742:Transcription Factor CHOP; D014157:Transcription Factors; D019892:eIF-2 Kinase; C497250:Ddit3 protein, mouse; C070634:Eif2ak4 protein, mouse; C513256:Ppp1r15a protein, mouse