A stress‐inducible rat liver endoplasmic reticulum protein, ERp29

Abstract

We have isolated, cDNA cloned and characterised a 29-kDa protein (ERp29), containing a C-terminal endoplasmic reticulum(ER)-retrieval signal, from the rat liver ER. ERp29 was induced to high levels in the rat hepatoma cells under metabolic stress conditions known to cause an aberrant accumulation of proteins in the ER [(e.g. culture in presence of the Ca 2ϩ ionophore A23187, inhibitors of Ca 2ϩ -ATPase (thapsigargin), intracellular protein transport (brefeldin A), or protein N-glycosylation (tunicamycin)]. Experimental evidence of its localisation in the luminal compartment of the ER was obtained by topology studies including immunofluorescence microscopy, in vitro translation and proteinase protection assay. ERp29 constitutes about 0.1% of the rat hepatic microsomal proteins and is constitutively expressed in all rat tissues examined, as evident from northern blot analysis. In rat hepatoma cells ERp29 was found to be associated with the abundant molecular chaperone/stress protein BiP/GRP78 and this interaction was significantly enhanced after treatment with tunicamycin and A23187. Taken together, these results suggest that ERp29 is a member of the stress-response machinery of the ER.Keywords : ERp29; endoplasmic reticulum; stress protein; retrieval signal; BiP/GRP78.The luminal compartment of the endoplasmic reticulum (ER) of the export of secretory proteins from the ER by brefeldin A, an inhibitor of intracellular transport, may also result in excesin eukaryotic cells is a site where nascent polypeptides, destined for transport to Golgi, lysosomes or cell exterior attain their sive accumulation of malfolded proteins in ER and hence cause induction of stress proteins [7]. native three-dimensional configuration, undergo several posttranslational modifications and are assembled. Molecular chap-ER stress-inducible proteins belong to structurally diverse protein families including glucose-regulated proteins GRP78/ erones facilitate these processes assisting in folding and preventing aggregation of nascent chains by binding to the interactive BiP and GRP94 which are similar to the cytosolic heat-shock proteins (Hsp70 and Hsp90, respectively), calnexin, calreticulin protein surface [1]. Other luminal enzymes, which are involved in protein maturation, catalyze disulphide bond formation and and protein disulfide isomerase (PDI and other thioredoxin-containing proteins such as ERp72 and ERp61). The importance of rearrangement, N-linked glycosylation, participate in maintaining calcium homeostasis and in protein trafficking (reviewed in these proteins for the luminal compartment is accentuated by their ER-retrieval signal, the C-terminal tetrapeptide KDEL [2Ϫ3]).The biosynthesis of chaperones and some folding enzymes [8Ϫ9]. A protein (ERp29) with a similar C-terminal sequence is increased in stressed ER, i.e. under a variety of adverse physiologic or metabolic conditions, whose common denominator is (KEEL) was isolated in our laboratory from rat liver ER and the corresponding cDNA was cloned [10]. An analogous clone was ...

Amidoxime Reductase System Containing Cytochrome b5 Type B (CYB5B) and MOSC2 Is of Importance for Lipid Synthesis in Adipocyte Mitochondria

“…Rabbit anti-MOSC2 and anti-CYB5B antibodies were from Atlas Antibodies (Stockholm Sweden); mouse anti-mHSP70 and rabbit anti-VDAC were from Affinity Bioreagents (Thermo Scientific); and rabbit anti-CYB5 was from Santa Cruz Biotechnology (AH Diagnostics AB, Skärholmen, Sweden). Rabbit anti-CYB5R3 (16), rabbit antiERp27 (17), and rabbit anti-calnexin (18) were previously described. Secondary horseradish peroxidase-coupled antirabbit and anti-mouse antibodies were from Dako (Dako Sweden AB, Stockholm, Sweden).…”

Overexpression of endoplasmic reticulum protein 29 regulates mesenchymal–epithelial transition and suppresses xenograft tumor growth of invasive breast cancer cells

“…15 Endoplasmic reticulum protein 29 (ERp29), a novel reticuloplasmin, was first cloned from rat liver and enamel cells. 16,17 Structurally, it has an ER-retrieval signal of the Cterminal tetrapeptide (KEEL) targeting the ER lumen, but lacks the classical chaperone, disulfide-editing, calcium-buffer, and stress-response properties. 18 It has been shown that ERp29 is directly associated with the folding and/or secretion of thyroglobulin, 19 as well as resistance to oxidative and radiation stress.…”

Identification of ERp29, an Endoplasmic Reticulum Lumenal Protein, as a New Member of the Thyroglobulin Folding Complex

“…Quality control of potential cargo proteins is accomplished by the molecular chaperones that monitor fidelity of the protein folding and prevent premature export of incorrectly folded or incompletely assembled secretory proteins from the ER (2). Circumstantial evidence, such as inducibility in certain cell types under the ER stress conditions (3), high expression in the secretory tissues (4,5), and co-localization with the ER chaperones (3), suggests that a recently discovered, ubiquitously expressed endoplasmic reticulum lumenal protein, ERp29, may complement this group of ER chaperones.…”

“…ERp29 cDNA was originally cloned from the rat liver (3,6) and enamel cells (7), and the ERp29 gene was shown to be highly conserved in all studied mammalian species (3)(4)(5). For instance, rat ERp29 and its human ortholog, originally termed ERp28 (8), are 90% identical on the amino acid sequence level (9).…”