title: Interconversion of GRP78/BiP. A novel event in the action of Pasteurella multocida toxin, bombesin, and platelet-derived growth factor.
abstract: Incubation of Swiss 3T3 cells with [2-3H]adenine, as in other cell types, reveals the ADP-ribosylation of GRP78 (the 78-kDa glucose-regulated protein, also known as BiP, the immunoglobulin heavy chain-binding protein), a resident endoplasmic reticulum protein that assists in the processing of proteins destined for secretion or cell surface expression. Here we show that Pasteurella multocida toxin, a potent growth factor for cultured fibroblasts, decreased the ADP-ribosylation of GRP78/BiP to 16 +/- 6% of the control value (n = 23). The action of the toxin occurred after a lag period, was blocked by lysosomotrophic agents, and potentiated by increased incubation time (ED50 4 ng/ml and 1 ng/ml in 4 and 8 h, respectively), thus indicating that the toxin enters the cells to act. Bombesin and platelet-derived growth factor (PDGF) similarly decreased the ADP-ribosylation of GRP78/BiP (ED50 0.5 nM and 2.5 ng/ml, respectively) but acted more rapidly than the toxin. Signaling pathways activated by the toxin, bombesin, and PDGF had effects on the ADP-ribosylation of GRP78/BiP. Thus, activation of protein kinase C alone by phorbol 12,13-dibutyrate was partially effective, and down-regulation of protein kinase C attenuated but did not block the action of the toxin, bombesin, and PDGF. Agents that mobilize Ca2+ from the endoplasmic reticulum (A23187, ionomycin, and thapsigargin) caused a decrease in the ADP-ribosylation of GRP78/BiP that was similar in magnitude to that achieved by the toxin, bombesin, and PDGF, implicating a role for inositol 1,4,5-trisphosphate-mediated Ca2+ mobilization in the action of the mitogenic agents. The growth factor-induced decrease in the ADP-ribosylation of GRP78/BiP may represent its conversion from an inactive to an active state.
authors.affiliation: Imperial Cancer Research Fund, London, United Kingdom.
authors.forename: J M
authors.initials: JM
authors.lastname: Staddon
authors.forename: M M
authors.initials: MM
authors.lastname: Bouzyk
authors.forename: E
authors.initials: E
authors.lastname: Rozengurt
mesh_terms: D016475:3T3 Cells; D000225:Adenine / Q000378:metabolism; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology*; D001839:Bombesin / Q000494:pharmacology*; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003903:Deuterium; D004591:Electrophoresis, Polyacrylamide Gel; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones; D008970:Molecular Weight; D010325:Pasteurella; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D013462:Sulfur Radioisotopes; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D018832:Molecular Chaperones; C062258:Pasteurella multocida toxin; D010982:Platelet-Derived Growth Factor; D013462:Sulfur Radioisotopes; D000246:Adenosine Diphosphate Ribose; D003513:Cycloheximide; D008715:Methionine; D003903:Deuterium; D000225:Adenine; D001839:Bombesin