title: Regulated in DNA damage and development 1 (REDD1) promotes cell survival during serum deprivation by sustaining repression of signaling through the mechanistic target of rapamycin in complex 1 (mTORC1).
abstract: Regulated in DNA damage and development 1 (REDD1) functions to repress signaling through the mechanistic target of rapamycin (mTOR) protein kinase in complex 1 (mTORC1) in response to diverse stress conditions. In the present study, we investigated the role of REDD1 in the response of cells to growth cessation induced by serum deprivation. REDD1 expression was induced within 2h of depriving cells of serum, with the induction being mediated through ER stress, as evidenced by activation of PERK, enhanced eIF2α phosphorylation, and ATF4 facilitated transcription of the REDD1 gene. In wild-type cells, signaling through mTORC1 was rapidly (within 30min) repressed in response to serum deprivation and the repression was sustained for at least 10h. In contrast, in REDD1 knockout cells mTORC1 signaling recovered toward the end of the 10h-deprivation period. Interestingly, Akt phosphorylation initially declined in response to serum deprivation and then recovered between 2 and 4h in wild-type but not REDD1 knockout cells. The recovery of mTORC1 signaling and the failure of Akt phosphorylation to do so in the REDD1 knockout cells were accompanied by a dramatic increase in caspase-3 cleavage and cell death, both of which were blocked by rapamycin. Furthermore, overexpression of constitutively active Akt rescued REDD1 knockout cells from serum deprivation induced cell death. Overall, the results implicate REDD1 as a key regulatory checkpoint that coordinates growth signaling inputs to activate pro-survival mechanisms and reduce susceptibility to cell death.
authors.affiliation: Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Dennis
authors.forename: Nora K
authors.initials: NK
authors.lastname: McGhee
authors.forename: Leonard S
authors.initials: LS
authors.lastname: Jefferson
authors.forename: Scot R
authors.initials: SR
authors.lastname: Kimball
mesh_terms: D051701:Activating Transcription Factor 4 / Q000378:metabolism; D000818:Animals; D001343:Autophagy; D002460:Cell Line; D002470:Cell Survival; D004249:DNA Damage; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D044967:Serum / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation
chemical_list: C497110:Atf4 protein, rat; C000632146:Ddit4 protein, rat; D046912:Multiprotein Complexes; D012097:Repressor Proteins; D014157:Transcription Factors; D051701:Activating Transcription Factor 4; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases
keywords: 4E-BP1; 70-kDa ribosomal protein S6 kinase 1; ATF4; Autophagy; DDIT4; ERK; FBS; GCN2; IGF1; LC3; PERK; REDD1; Rtp801; ULK1; UNC-51-like kinase 1; X-box binding protein 1; XBP1; activating transcription factor 4; autophagy marker light chain 3; ca; constitutively active; dn; dominant negative; eukaryotic initiation factor 4E binding protein 1; extracellular signal-related protein kinase; fetal bovine serum; general control non-derepressing 2; insulin-like growth factor 1; mTORC1; mammalian target of rapamycin in complex 1; p70S6K1; protein kinase RNA-like endoplasmic reticulum kinase; regulated in DNA damage and development 1
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