{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n ERp27 is an endoplasmic reticulum–resident, 27.7‐kDa protein that belongs to the protein disulfide isomerase (PDI) family yet lacks redox‐active catalytic cysteines. Structural and biochemical studies have shown that it is composed of two thioredoxin‐fold domains homologous to the non‐catalytic b and b′ domains of canonical PDIs, with the b′‐like domain mediating peptide binding and undergoing conformational changes upon substrate engagement. These studies, based on high‐resolution NMR and crystallographic analyses, indicate that ERp27 can bind unfolded substrates (such as Δ‐somatostatin) and physically interact with the catalytic partner ERp57, suggesting that it may help chaperone misfolded proteins and facilitate their subsequent oxidative folding."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In addition to its well‐characterized structural role, ERp27 appears to be implicated in several pathological and biotechnological contexts. For instance, its expression is up‐regulated by interleukin‐22 in colon carcinoma cells, which raises the possibility that ERp27 may contribute to tumor–promoting inflammatory signals."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": " Moreover, in engineered Chinese hamster ovary cells, moderate overexpression of ERp27—especially when co‐expressed with ERp57—enhances cell viability and productivity of both easy‐ and difficult‐to–express recombinant proteins, underscoring its potential as a modulator of ER proteostasis in industrial applications."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Alterations in ERp27 expression have also been observed in disease settings. Differential expression of ERp27 has been noted in carotid atherosclerotic plaques with unstable phenotypes, suggesting that changes in ER homeostasis may be linked to vascular pathology."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " In studies of the human pancreas, ERp27 was identified among proteins with elevated expression levels; conversely, decreased levels of ERp27 were observed in the endoplasmic reticulum of pancreatic tissue during acute pancreatitis, indicating that its expression may serve as a marker of ER functional status in stress and disease."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Together, these findings support a model in which ERp27 acts as a non‐catalytic chaperone within the ER, binding unfolded proteins and presenting them to enzymatic partners such as ERp57 for proper folding. Its regulated expression under stress and in pathological conditions further underscores its importance in maintaining ER proteostasis, while its ability to enhance recombinant protein production highlights a promising biotechnological application.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Heli I Alanen, Richard A Williamson, Mark J Howard, et al. 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