Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P11021 (BiP)
 2,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of asparagine (N)-linked oligosaccharide chains in intracellular folding of the human chorionic gonadotropin (hCG)-beta subunit was determined by examining the kinetics of folding in Chinese hamster ovary (CHO) cells transfected with wild-type or mutant hCG-beta genes lacking one or both of the asparagine glycosylation sites. The half-time for folding of p beta 1 into p beta 2, the rate-determining step in beta folding, was 7 min for wild-type beta but 33 min for beta lacking both N-linked glycans. The p beta 1-->p beta 2 half-time was 7.5 min in CHO cells expressing the beta subunit missing the Asn13-linked glycan and 10 min for the beta subunit missing the Asn30-linked glycan. The inefficient folding of hCG-beta lacking both N-linked glycans correlated with the slow formation of the last three disulfide bonds (i.e. disulfides 23-72, 93-100, and 26-110) to form in the hCG-beta-folding pathway. Unglycosylated hCG-beta was slowly secreted from CHO cells, and beta subunit-folding intermediates retained in cells for more than 5 h were degraded into a hCG-beta core fragment-like protein. However, coexpression of the hCG-alpha gene enhanced folding and formation of disulfide bonds 23-72, 93-100, and 26-110 of hCG-beta lacking N-linked glycans. In addition, the molecular chaperones BiP, ERp72, and ERp94, but not calnexin, were found in a complex with unglycosylated, unfolded hCG-beta and may be involved in the folding of this beta form. These data indicate that N-linked oligosaccharides assist hCG-beta subunit folding by facilitating disulfide bond formation.
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PMID:The asparagine-linked oligosaccharides of the human chorionic gonadotropin beta subunit facilitate correct disulfide bond pairing. 753 25

Protein folding and quality control in the early secretory pathway function as posttranslational checkpoints in eukaryote gene expression. Herein, an aberrant form of the hepatic secretory protein alpha1-antitrypsin was stably expressed in a human embryonic kidney cell line to elucidate the mechanisms by which glycoprotein endoplasmic reticulum-associated degradation (GERAD) is administered in cells from higher eukaryotes. After biosynthesis, genetic variant PI Z underwent alternative phases of secretion and degradation, the latter of which was mediated by the proteasome. Degradation required release from calnexin- and asparagine-linked oligosaccharide modification by endoplasmic reticulum mannosidase I, the latter of which occurred as PI Z was bound to the molecular chaperone grp78/BiP. That a distinct GERAD program operates in human embryonic kidney cells was supported by the extent of PI Z secretion, apparent lack of polymerization, inability of calnexin to participate in the degradation process, and sequestration of the glycoprotein folding sensor UDP-glucose:glycoprotein glucosyltransferase in the Golgi complex. Because UDP-glucose:glycoprotein glucosyltransferase sustains calnexin binding, its altered distribution is consistent with a GERAD program that hinders the reentry of substrates into the calnexin cycle, allowing grp78/BiP to partner with a lectin, other than calnexin, in the recognition of a two-component GERAD signal to facilitate substrate recruitment. How the processing of a mutant protein, rather than the mutation itself, can contribute to disease pathogenesis, is discussed.
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PMID:Organizational diversity among distinct glycoprotein endoplasmic reticulum-associated degradation programs. 1218 35

Recently, it has become apparent that asparagine-linked (N-linked) oligosaccharide at an early stage of processing can play an important role in quality control of the secretory pathway. Here, we have developed a system for better understanding of the N-glycosylation machinery and its involvement in quality control in the endoplasmic reticulum (ER). Rough microsomes (RM) treated with 0.18% Tx-100 (TxRM) preserved translocation activities to a similar extent detected in RM. TxRM were depleted of many soluble proteins including glucosidase II, BiP and Erp72, but maintained approximately 80% of calnexin, a membrane protein. More importantly, TxRM revealed insufficient glycosylation of T cell receptor-alpha (TCR-alpha), suggesting that a factor or factors extracted with 0.18% Tx-100 is responsible for facilitating the transfer of oligosaccharides to the protein. In addition, the top band of TCR-alpha translated in TxRM migrated slower than that in RM, but faster than that in RM treated with castanospermine (CST), an inhibitor of glucosidase I/II. This suggests that the trimming of the inner two glucose sugars is impaired by the loss of glucosidase II. Furthermore, we demonstrated that TCR-alpha coprecipitated with calnexin migrated between unglucosylated and diglucosylated forms on SDS-PAGE. Thus, the treatment of RM with low concentration of detergent is a very powerful method for elucidating not only N-glycosylation processes but also other biological functions such as quality control in the ER.
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PMID:A novel approach for N-glycosylation studies using detergent extracted microsomes. 1618 Jan 1

ROS (reactive oxygen species) play an essential role in the pathophysiology of diabetes, stroke and neurodegenerative disorders. Hyperglycaemia associated with diabetes enhances ROS production and causes oxidative stress in vascular endothelial cells, but adverse effects of either acute or chronic high-glucose environments on brain parenchymal cells remain unclear. The PPP (pentose phosphate pathway) and GSH participate in a major defence mechanism against ROS in brain, and we explored the role and regulation of the astroglial PPP in response to acute and chronic high-glucose environments. PPP activity was measured in cultured neurons and astroglia by determining the difference in rate of (14)CO(2) production from [1-(14)C]glucose and [6-(14)C]glucose. ROS production, mainly H(2)O(2), and GSH were also assessed. Acutely elevated glucose concentrations in the culture media increased PPP activity and GSH level in astroglia, decreasing ROS production. Chronically elevated glucose environments also induced PPP activation. Immunohistochemical analyses revealed that chronic high-glucose environments induced ER (endoplasmic reticulum) stress (presumably through increased hexosamine biosynthetic pathway flux). Nuclear translocation of Nrf2 (nuclear factor-erythroid 2 p45 subunit-related factor 2), which regulates G6PDH (glyceraldehyde-6-phosphate dehydrogenase) by enhancing transcription, was also observed in association with BiP (immunoglobulin heavy-chain-binding protein) expression. Acute and chronic high-glucose environments activated the PPP in astroglia, preventing ROS elevation. Therefore a rapid decrease in glucose level seems to enhance ROS toxicity, perhaps contributing to neural damage when insulin levels given to diabetic patients are not properly calibrated and plasma glucose levels are not adequately maintained. These findings may also explain the lack of evidence for clinical benefits from strict glycaemic control during the acute phase of stroke.
ASN Neuro 2012 Mar 22
PMID:Astroglial pentose phosphate pathway rates in response to high-glucose environments. 2230 Apr 9

Early life events are associated with the susceptibility to chronic diseases in adult life. Perturbations of endoplasmic reticulum (ER) homeostasis activate the unfolded protein response (UPR), which contributes to the development of metabolic alterations. Our aim was to evaluate liver UPR in an animal model of intrauterine growth restriction (IUGR). A significantly increased expression of X-box binding protein-1 spliced (XBP1s) mRNA (p<0.01), Endoplasmic Reticulum-localized DnaJ homologue (Erdj4) mRNA (p<0.05) and Bip/GRP78-glucose-regulated protein 78 (Bip) mRNA (p<0.05) was observed in the liver of IUGR rats at birth. Furthermore, the expression of gluconeogenesis genes and lipogenesis genes were significantly upregulated (p<0.05) in IUGR pups. At 105 d, IUGR male rats showed significantly reduced glucose tolerance (p<0.01). A significant decreased expression of XBP1s mRNA (p<0.01) and increased expression of double-stranded RNA-dependent protein kinase-like ER kinase (PERK) and Asparagine synthetase (ASNS) (p<0.05) was observed in the liver of IUGR male adult rats. Liver focal steatosis and periportal fibrosis were observed in IUGR rats. These findings show for the first time that fetal exposure to uteroplacental insufficiency is associated with the activation of hepatic UPR and suggest that UPR signaling may play a role in the metabolic risk.
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PMID:The exposure to uteroplacental insufficiency is associated with activation of unfolded protein response in postnatal life. 2989 97

Pro-apoptotic peptides have attracted much attention as promising anticancer agents due to their high activity. However, poor cellular uptake of the peptides is often associated with limited therapeutic application. Cell-penetrating homing peptides (CPHPs) were found to increase cell internalization as well as anticancer efficacy of the peptide conjugates. In this study, we developed a novel recombinant fusion protein composed of sIL-24 peptide as a pro-apoptotic moiety and asparagine-glycine-arginine (NGR) motif as a CD13-targeting CPHP component. In silico analysis demonstrated that flexible GGGGS linker provided the best structure and stability for our designed fusion protein. Cell adhesion experiments showed a significant binding affinity toward high CD13-expressing cells (U937 and A549) for NGR-sIL-24. Moreover, confocal microscopy revealed that NGR strongly facilitated the binding and cellular uptake of sIL-24 in U937 and A549 cancer cells. NGR-sIL-24 treatment markedly inhibited the growth of U937 and A549 cancer cells in a dose and time-dependent manner, without affecting the normal cell line MRC-5. Flow cytometric analysis and Hoechst 33342 staining exhibited potent apoptosis induction in U937 and A549 cells treated with NGR-sIL-24. Further mechanism elucidation uncovered that apoptotic death promoted by NGR-sIL-24 was attributed to upregulation of BiP/GRP78, Bax/Bcl-2, GADD34, cytochrome c release, and cleavage of caspase-3, suggesting NGR-sIL-24 penetration into cancerous cells and subsequent apoptosis induction, mainly through endoplasmic reticulum (ER) stress-dependent and mitochondria-dependent signaling pathways. Our results indicate that the designed recombinant fusion protein NGR-sIL-24 may serve as a potential targeted therapy agent for cancers with high expression of CD13.
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PMID:Novel fusion protein NGR-sIL-24 for targetedly suppressing cancer cell growth via apoptosis. 3223 69