title: Disruption of the PP1/GADD34 complex induces calreticulin exposure.
abstract: In response to some chemotherapeutic agents, tumor cells can translocate calreticulin (CRT), which is usually contained in the lumen of the endoplasmic reticulum, to the surface of the plasma membrane. This effect requires the phosphorylation of the eukaryotic initiation factor 2alpha(eIF2alpha) by the eIF2alpha kinase PERK, yet may also be triggered by inhibition of the eIF2alpha phosphatase, which is composed by a catalytic subunit (PP1) and a regulatory subunit (GADD34). Here, we addressed the question whether the dissociation of the PP1/GADD34 complex would be sufficient to trigger CRT exposure. Molecular modeling led to the design of a GADD34-derived peptide that competitively disrupts the PP1/GADD34 complex. When added to intact cells, the GADD34-derived peptide fused to a plasma membrane translocation domain abolished the interaction between PP1 and GADD34, stimulated the phosphorylation of eIF2alpha, and triggered CRT exposure. However, the resolution of the PP1/GADD34 complex did not evoke apoptosis, allowing for the dissociation of CRT exposure and cell death. Anthracyclins, which are highly efficient in inducing CRT translocation to the cell surface also stimulated the dissociation of the PP1/GADD34 complex. These results suggest that the PP1/GADD34 complex plays a major role in the regulation of CRT exposure.
authors.affiliation: INSERM, U848, Villejuif, France.
authors.forename: Oliver
authors.initials: O
authors.lastname: Kepp
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Galluzzi
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Giordanetto
authors.forename: Antoine
authors.initials: A
authors.lastname: Tesniere
authors.forename: Ilio
authors.initials: I
authors.lastname: Vitale
authors.forename: Isabelle
authors.initials: I
authors.lastname: Martins
authors.forename: Frederic
authors.initials: F
authors.lastname: Schlemmer
authors.forename: Sandy
authors.initials: S
authors.lastname: Adjemian
authors.forename: Laurence
authors.initials: L
authors.lastname: Zitvogel
authors.forename: Guido
authors.initials: G
authors.lastname: Kroemer
mesh_terms: D000595:Amino Acid Sequence; D018943:Anthracyclines / Q000494:pharmacology; D000943:Antigens, Differentiation / Q000378:metabolism*; D017209:Apoptosis; D001665:Binding Sites; D037282:Calreticulin / Q000378:metabolism / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D003198:Computer Simulation; D004721:Endoplasmic Reticulum / Q000502:physiology; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D018943:Anthracyclines; D000943:Antigens, Differentiation; D037282:Calreticulin; D018797:Cell Cycle Proteins; D015852:Eukaryotic Initiation Factor-2; D054645:Protein Phosphatase 1; D019892:eIF-2 Kinase; C087519:PPP1R15A protein, human