title: ARTC1-mediated ADP-ribosylation of GRP78/BiP: a new player in endoplasmic-reticulum stress responses.
abstract: Protein mono-ADP-ribosylation is a reversible post-translational modification of cellular proteins. This scheme of amino-acid modification is used not only by bacterial toxins to attack host cells, but also by endogenous ADP-ribosyltransferases (ARTs) in mammalian cells. These latter ARTs include members of three different families of proteins: the well characterised arginine-specific ecto-enzymes (ARTCs), two sirtuins, and some members of the poly(ADP-ribose) polymerase (PARP/ARTD) family. In the present study, we demonstrate that human ARTC1 is localised to the endoplasmic reticulum (ER), in contrast to the previously characterised ARTC proteins, which are typical GPI-anchored ecto-enzymes. Moreover, using the "macro domain" cognitive binding module to identify ADP-ribosylated proteins, we show here that the ER luminal chaperone GRP78/BiP (glucose-regulated protein of 78 kDa/immunoglobulin heavy-chain-binding protein) is a cellular target of human ARTC1 and hamster ARTC2. We further developed a procedure to visualise ADP-ribosylated proteins using immunofluorescence. With this approach, in cells overexpressing ARTC1, we detected staining of the ER that co-localises with GRP78/BiP, thus confirming that this modification occurs in living cells. In line with the key role of GRP78/BiP in the ER stress response system, we provide evidence here that ARTC1 is activated during the ER stress response, which results in acute ADP-ribosylation of GRP78/BiP paralleling translational inhibition. Thus, this identification of ARTC1 as a regulator of GRP78/BiP defines a novel, previously unsuspected, player in GRP78-mediated ER stress responses.
authors.affiliation: Laboratory of G-Protein-mediated Signalling, Department of Cellular and Translational Pharmacology, Mario Negri Sud Foundation, Via Nazionale 8/A, 66030, Santa Maria Imbaro, CH, Italy.
authors.forename: Gaia
authors.initials: G
authors.lastname: Fabrizio
authors.forename: Simone
authors.initials: S
authors.lastname: Di Paola
authors.forename: Annalisa
authors.initials: A
authors.lastname: Stilla
authors.forename: Monica
authors.initials: M
authors.lastname: Giannotta
authors.forename: Carmen
authors.initials: C
authors.lastname: Ruggiero
authors.forename: Stephan
authors.initials: S
authors.lastname: Menzel
authors.forename: Friedrich
authors.initials: F
authors.lastname: Koch-Nolte
authors.forename: Michele
authors.initials: M
authors.lastname: Sallese
authors.forename: Maria
authors.initials: M
authors.lastname: Di Girolamo
mesh_terms: D036002:ADP Ribose Transferases / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress; D058851:GPI-Linked Proteins / Q000032:analysis / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism*; D006801:Humans
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D058851:GPI-Linked Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D036002:ADP Ribose Transferases; C449301:ART1 protein, human