title: Nck in a complex containing the catalytic subunit of protein phosphatase 1 regulates eukaryotic initiation factor 2alpha signaling and cell survival to endoplasmic reticulum stress.
abstract: Stress imposed on the endoplasmic reticulum (ER) induces the phosphorylation of the alpha-subunit of the eukaryotic initiation factor 2 (eIF2) on Ser51. This results in transient inhibition of general translation initiation while concomitantly activating a signaling pathway that promotes the expression of genes whose products improve ER function. Conversely, dephosphorylation of eIF2alphaSer51 is accomplished by protein phosphatase 1 (PP1c) complexes containing either the protein CReP or GADD34, which target PP1c to eIF2. Here, we demonstrate that the Src homology (SH) domain-containing adaptor Nck is a key component of a molecular complex that controls eIF2alpha phosphorylation and signaling in response to ER stress. We show that overexpression of Nck decreases basal and ER stress-induced eIF2alpha phosphorylation and the attendant induction of ATF4 and CHOP. In contrast, we demonstrate that the mouse embryonic fibroblasts lacking both isoforms of Nck (Nck1-/-Nck2-/-) show higher levels of eIF2alpha phosphorylation and premature induction of ATF4, CHOP, and GADD34 in response to ER stress and finally, are more resistant to cell death induced by prolonged ER stress conditions. We establish that a significant amount of Nck protein localizes at the ER and is in a complex with eIF2 subunits. Further analysis of this complex revealed that it also contains the Ser/Thr phosphatase PP1c, its regulatory subunit CReP, and dephosphorylates eIF2alpha on Ser51 in vitro. Overall, we demonstrate that Nck as a component of the CReP/PP1c holophosphatase complex contributes to maintain eIF2alpha in a hypophosphorylated state. In this manner, Nck modulates translation and eIF2alpha signaling in response to ER stress.
authors.affiliation: Polypeptide Hormone Laboratory, Department of Medicine, McGill University, Montreal, Quebec H3A 2B2, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Latreille
authors.forename: Louise
authors.initials: L
authors.lastname: Larose
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D046912:Multiprotein Complexes; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D054645:Protein Phosphatase 1; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation; C081452:Atf4 protein, mouse; D018797:Cell Cycle Proteins; D015852:Eukaryotic Initiation Factor-2; D046912:Multiprotein Complexes; C078332:Nck protein; D015513:Oncogene Proteins; D020033:Protein Isoforms; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D051701:Activating Transcription Factor 4; D051742:Transcription Factor CHOP; D010749:Phosphoprotein Phosphatases; C513256:Ppp1r15a protein, mouse; D054645:Protein Phosphatase 1