Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Endoplasmic reticulum (ER) stress mechanisms have been found to play critical roles in a number of diseases states, such as diabetes mellitus and Alzheimer disease, but whether they are involved in acute pancreatitis is unknown. Here we show for the first time that all major ER stress sensing and signaling mechanisms are present in exocrine acini and are activated early in the arginine model of experimental acute pancreatitis. Pancreatitis was induced in rats by intraperitoneal injection of 4.0 g/kg body wt arginine. Pancreatitis severity was assessed by analysis of serum amylase, pancreatic trypsin activity, water content, and histology. ER stress-related molecules PERK, eIF2alpha, ATF6, XBP-1, BiP, CHOP, and caspase-12 were analyzed. Arginine treatment induced rapid and severe pancreatitis, as indicated by increased serum amylase, pancreatic tissue edema, and acinar cell damage within 4 h. Arginine treatment also caused an early activation of ER stress, as indicated by phosphorylation of PERK and its downstream target eIF2alpha, ATF6 translocation into the nucleus (within 1 h), and upregulation of BiP (within 4 h). XBP-1 splicing and CHOP expression were observed within 8 h. After 24 h, increased activation of the ER stress-related proapoptotic molecule caspase-12 was observed along with an increase in caspase-3 activity and TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labeling (TUNEL) staining in exocrine acini. These results indicate that ER stress is an important early acinar cell event that likely contributes to the development of acute pancreatitis in the arginine model.
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PMID:Early activation of endoplasmic reticulum stress is associated with arginine-induced acute pancreatitis. 1657 87

The unfolded protein response (UPR) events triggered by the accumulation of unfolded protein in endoplasmic reticulum (ER) activate the three UPR signaling pathways mediated by IRE1, ATF6 and PERK. Spliced XBP1 mRNA induced by activated IRE1 is translated to the protein, a potent transcription factor that induces BiP expression. XBP1 is also induced by activated ATF6. It is thus thought to be an important marker reflecting both IRE1 and ATF6 signaling in response to ER stress. For quantitative measurement of XBP1 gene expression, it is important to distinguish between the spliced and non-spliced form of XBP1 mRNA. We have developed a new method to detect the spliced XBP1 mRNA by means of real-time PCR and we compared the result with measurements of the expression of the ER stress inducible gene BiP. A good correlation was found between spliced XBP1 expression and BiP expression. Thus, our method may be useful for simple and quantitative evaluation of ER stress.
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PMID:Quantitative measurement of spliced XBP1 mRNA as an indicator of endoplasmic reticulum stress. 1677 4

Mammalian transcription factor ATF6 is constitutively synthesized as a type II transmembrane protein embedded in the endoplasmic reticulum (ER). It is activated when unfolded proteins are accumulated in the ER under ER stress through a process called regulated intramembrane proteolysis (Rip), in which ATF6 is transported from the ER to the Golgi apparatus where it undergoes sequential cleavage by Site-1 and Site-2 proteases. The cytosolic transcription factor domain of ATF6 liberated from the Golgi membrane enters the nucleus where it activates transcription of ER-localized molecular chaperones and folding enzymes, leading to the maintenance of the homeostasis of the ER. Here, we analyzed M19 cells, a mutant of Chinese hamster ovary cells deficient in Site-2 protease. It was previously shown that M19 cells are defective in the induction of mRNA encoding the major ER chaperone BiP. In M19 cells, ATF6 was not converted from the membrane-bound precursor form to the cleaved and nuclear form as expected. Moreover, some of the ATF6 was constitutively relocated to the Golgi apparatus, where it was cleaved by Site-1 protease, and remained associated with the Golgi apparatus, indicating that the ER of M19 cells was constitutively stressed. Consistent with this notion, the two other ER stress response mediators, IRE1 and PERK, were also constitutively activated in M19 cells. M19 cells showed inefficient secretion of a model protein. These results suggest that Rip-mediated activation of ATF6 is important for the homeostasis of the ER in not only ER-stressed but also unstressed cells.
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PMID:Analysis of ATF6 activation in Site-2 protease-deficient Chinese hamster ovary cells. 1711 Jul 86

Mammalian transcription factor ATF6 is constitutively synthesized as a type II transmembrane protein embedded in the endoplasmic reticulum (ER). Upon ER stress ATF6 is transported to the Golgi apparatus where it is cleaved to release its cytoplasmic domain. This is then translocated into the nucleus where it activates transcription of ER-localized molecular chaperones and folding enzymes to maintain the homeostasis of the ER. We recently found that, owing to the presence of intra- and intermolecular disulfide bridges, ATF6 occurs in unstressed ER in monomer, dimer and oligomer forms. Disulfide-bonded ATF6 is reduced on treatment of cells with various chemical ER stress inducers, and only the reduced monomer ATF6 reaches the Golgi apparatus. In this study, we evoked ER stress under more physiological conditions, namely, glucose starvation, and analyzed its consequence for ATF6 activation. Glucose starvation activated ATF6 and induced the ER chaperone BiP, albeit weakly. ATF6 was thus dissociated from BiP, transported to the Golgi apparatus, and cleaved. Glucose starvation enhanced the synthesis of ATF6 approximately two-fold, probably via transcriptional induction. Importantly, reduction of disulfide bridges and transport of reduced monomer occurred in response to glucose starvation. We conclude that ER stress-induced reduction of ATF6 represents a general feature of the ATF6 activation process.
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PMID:Reduction of disulfide bridges in the lumenal domain of ATF6 in response to glucose starvation. 1790 5

The prevalence of HIV-associated neurocognitive impairment (NCI), which includes HIV-associated dementia (HAD) and minor cognitive and motor disorder (MCMD), has been increasing. HIV-infected and/or activated macrophages/microglia in the brain initiate the neurodegeneration seen in HIV-associated NCI via soluble neurotoxic mediators, including reactive oxygen species, viral proteins and excitotoxins. Neurotoxic factors released by macrophages/microglia injure neurones directly and alter astrocytic homeostatic functions, which can lead to excitotoxicity and oxidative stress-mediated neuronal injury. Often, cells respond to oxidative stress by initiating the endoplasmic reticulum (ER) stress response. Thus, we hypothesize that ER stress response is activated in HIV-infected cortex. We used immunofluorescence and immunoblotting to assess expression patterns of the ER stress proteins, BiP and ATF6, in HIV-positive cortical autopsy tissue. Additionally, we performed immunofluorescence using cell type-specific markers to examine BiP staining in different cell types, including neurones, astrocytes and macrophages/microglia. We observed a significant increase in BiP expression by both immunoblotting and immunofluorescence in HIV-positive cortex compared with control tissue. Additionally, phenotypic analysis of immunofluorescence showed cell type-specific increases in BiP levels in neurones and astrocytes. Further, ATF-6beta, an ER stress response initiator, is up-regulated in the same patient group, as assessed by immunoblotting. These results suggest that ER stress response is activated in HIV-infected cortex. Moreover, data presented here indicate for the first time that numbers of macrophages/microglia increase in brains of MCMD patients, as has been observed in HAD.
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PMID:Expression of the endoplasmic reticulum stress response marker, BiP, in the central nervous system of HIV-positive individuals. 1793 54

The endoplasmic reticulum (ER) stress response is a defense system for dealing with the accumulation of unfolded proteins in the ER lumen. Recent reports have shown that ER stress is involved in the pathology of some neurodegenerative diseases and cerebral ischemia. In a screen for compounds that induce the ER-mediated chaperone BiP (immunoglobulin heavy-chain binding protein)/GRP78 (78 kDa glucose-regulated protein), we identified BiP inducer X (BIX). BIX preferentially induced BiP with slight inductions of GRP94 (94 kDa glucose-regulated protein), calreticulin, and C/EBP homologous protein. The induction of BiP mRNA by BIX was mediated by activation of ER stress response elements upstream of the BiP gene, through the ATF6 (activating transcription factor 6) pathway. Pretreatment of neuroblastoma cells with BIX reduced cell death induced by ER stress. Intracerebroventricular pretreatment with BIX reduced the area of infarction due to focal cerebral ischemia in mice. In the penumbra of BIX-treated mice, ER stress-induced apoptosis was suppressed, leading to a reduction in the number of apoptotic cells. Considering these results together, it appears that BIX induces BiP to prevent neuronal death by ER stress, suggesting that it may be a potential therapeutic agent for cerebral diseases caused by ER stress.
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PMID:A molecular chaperone inducer protects neurons from ER stress. 1804 81

Cigarette smoke (CS) generally places severe stress on cells, as reflected by gene expression profiling and pathway analysis, which, among other effects, also suggested activation of the unfolded protein response pathway triggered by the stressed endoplasmic reticulum (ER stress). Here, we present data indicating that noncytotoxic concentrations of aqueous extracts of CS induce a distinct ER stress response in immortalized nontransformed Swiss 3T3 cells, primarily by activating the PERK pathway of global protein synthesis inhibition. Activation of PERK and PERK-dependent signaling by aqueous extracts of CS was demonstrated by (i) the inhibition of protein synthesis, (ii) the phosphorylation of PERK and its substrate eIF2alpha, (iii) the activation of ATF4, and (iv) the expression of ATF4-dependent target genes chop, gadd34, BiP, and atf3. Within the dose range tested, all effects appeared to be transient in nature, while the periods of recovery from ER stress were clearly concentration dependent. In contrast to these data and to the effects seen with thapsigargin (used as positive control), only minor effects were observed for the activation of xbp-1, a common target of the other two canonical sensors of ER stress, i.e., ATF6 and IRE1. In mechanistic terms, neither the disruption of energy levels nor a contribution of arylating quinones played a major role under the experimental conditions tested. Notably however, the effects of aqueous extracts of CS on the ER could be mimicked in the presence of acrolein at CS-relevant concentrations, indicating that CS interferes with proper ER function, presumably due mainly to changes in cellular redox homeostasis. Since ER stress has been linked to diseases that are also related to CS exposure, these data are relevant in the discussion of a general molecular mechanism of CS-induced disease.
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PMID:Endoplasmic reticulum stress induced by aqueous extracts of cigarette smoke in 3T3 cells activates the unfolded-protein-response-dependent PERK pathway of cell survival. 1820 57

The activity of PERK, an endoplasmic reticulum (ER) transmembrane protein kinase, assists in an ER stress response designed to inhibit general protein synthesis while allowing upregulated synthesis of selective proteins such as the ATF4 transcription factor. PERK null mice exhibit phenotypes that especially affect secretory cell types. Although embryonic fibroblasts from these mice are difficult to transfect with high efficiency, we have generated 293 cells stably expressing the PERK-K618A dominant negative mutant. 293/PERK-K618A cells, in response to ER stress: (a) do not properly inhibit general protein synthesis, (b) exhibit defective/delayed induction of ATF4 and BiP, and (c) exhibit exuberant splice activation of XBP1 and robust cleavage activation of ATF6, with abnormal regulation of calreticulin levels. The data suggest compensatory mechanisms allowing for cell survival in the absence of functional PERK. Interestingly, although induction of CHOP (a transcription factor implicated in apoptosis) is notably delayed after onset of ER stress, 293/PERK-K618A cells eventually produce CHOP at normal or even supranormal levels and exhibit increased apoptosis either in response to general ER stress or, more importantly, to specific misfolded secretory proteins.
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PMID:Endoplasmic reticulum (ER) chaperone regulation and survival of cells compensating for deficiency in the ER stress response kinase, PERK. 1842 96

Disruption of endoplasmic reticulum (ER) homeostasis causes accumulation of unfolded and misfolded proteins in the ER, triggering the ER stress response, which can eventually lead to apoptosis when ER dysfunction is severe or prolonged. Here we demonstrate that human MCF-7 breast cancer cells, as well as murine NIH/3T3 fibroblasts, are rescued from ER stress-initiated apoptosis by insulin-like growth factor-I (IGF-I). IGF-I significantly augments the adaptive capacity of the ER by enhancing compensatory mechanisms such as the IRE1 alpha-, PERK- and ATF6-mediated arms of ER stress signalling. During ER stress, IGF-I stimulates translational recovery and induces expression of the key molecular chaperone protein Grp78/BiP, thereby enhancing the folding capacity of the ER and promoting recovery from ER stress. We also demonstrate that the antiapoptotic activity of IGF-I during ER stress may be mediated by a novel, as yet unidentified, signalling pathway(s). Application of signal transduction inhibitors of MEK (U1026), PI3K (LY294002 and wortmannin), JNK (SP600125), p38 (SB203580), protein kinases A and C (H-89 and staurosporine) and STAT3 (Stattic) does not prevent IGF-I-mediated protection from ER stress-induced apoptosis. Taken together, these data demonstrate that IGF-I protects against ER stress-induced apoptosis by increasing adaptive mechanisms through enhancement of ER stress-signalling pathways, thereby restoring ER homeostasis and preventing apoptosis.
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PMID:Insulin-like growth factor-I protects cells from ER stress-induced apoptosis via enhancement of the adaptive capacity of endoplasmic reticulum. 1843 63

HeLa cells stably expressing the alpha chain of T-cell receptor (alphaTCR), a model substrate of ER-associated degradation (ERAD), were used to analyze the effects of BiP/Grp78 depletion by the SubAB cytotoxin. SubAB induced XBP1 splicing, followed by JNK phosphorylation, eIF2alpha phosphorylation, upregulation of ATF3/4 and partial ATF6 cleavage. Other markers of ER stress, including elements of ERAD pathway, as well as markers of cytoplasmic stress, were not induced. SubAB treatment decreased absolute levels of alphaTCR, which was caused by inhibition of protein synthesis. At the same time, the half-life of alphaTCR was extended almost fourfold from 70 min to 210 min, suggesting that BiP normally facilitates ERAD. Depletion of p97/VCP partially rescued SubAB-induced depletion of alphaTCR, confirming the role of VCP in ERAD of alphaTCR. It therefore appears that ERAD of alphaTCR is driven by at least two different ATP-ase systems located at two sides of the ER membrane, BiP located on the lumenal side, while p97/VCP on the cytoplasmic side. While SubAB altered cell morphology by inducing cytoplasm vacuolization and accumulation of lipid droplets, caspase activation was partial and subsided after prolonged incubation. Expression of CHOP/GADD153 occurred only after prolonged incubation and was not associated with apoptosis.
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PMID:Decreased ER-associated degradation of alpha-TCR induced by Grp78 depletion with the SubAB cytotoxin. 1861 45


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