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 interphotoreceptor matrix (IPM) is located between photoreceptors and pigment epithelium in the retina and is involved in fundamental functions of the visual cycle. These include visual pigment chromophore exchange, retinal adhesion, metabolite trafficking, and growth factor presentation. In general, IPM preparations are contaminated with intracellular proteins, as has also been described for other body fluids. This study aimed at identifying new components of the IPM by discriminating between truly secreted proteins and proteins that are part of the IPM for secondary reasons. "Soluble" porcine IPM was extracted from retina and pigment epithelium with PBS by two different procedures, followed by extraction with water alone that released "insoluble" IPM matrix sheets. Samples from all preparations were separated by 2-DE and a total of 140 protein spots were identified by MALDI-TOF and/or CapLC Q-TOF MS. Although identified proteins included several already known in the IPM, the majority had not been previously described in this structure. Gene ontology classifications allocated the identified proteins into nine different functional networks. The IPM preparations also included intracellular proteins from cells adjacent to the IPM, which may have resulted from cell disruption. This underlines the experimental difficulties of a biochemical analysis of the IPM as an intact compartment. We show here a strategy for predicting the probability of identified IPM proteins occurring in vivo by combined high-resolution protein separation methods with computational prediction methods. Thus, a set of potentially neuroprotective proteins could be extracted, including PEA-15, peroxiredoxin 5, alpha-B-crystallin, macrophage migration inhibitory factor, 78 kDa glucose-regulated protein (GRP78), protein disulfide-isomerase, and PEP-19, which have not been previously associated with the IPM. Furthermore, with immunohistochemical staining we could confirm the localization of GRP78 in the IPM on porcine eye sections, thus validating the proposed prediction method.
Proteomics 2005 Sep
PMID:Proteomic analysis of the porcine interphotoreceptor matrix. 1612 31

We previously reported that the secretory capacity of Pichia pastoris is limited with respect to the secretion of a 96.5-kDa bivalent anti-CD3 immunotoxin; double-copy expression generated more translation products than single-copy expression but did not increase the secretion of the immunotoxin. In Saccharomyces cerevisiae heterologous protein secretion has been reported to increase the expression of molecular chaperones, most prominently BiP/Kar2p. We therefore investigated the relationships between immunotoxin secretion and Kar2p expression in P. pastoris. We found that expression of the immunotoxin in P. pastoris increased the expression of Kar2p to levels that surpassed the retrieval capacity of the cell, leading to secretion of Kar2p into the medium. The level of Kar2p secretion was correlated with the copy number of the immunotoxin gene. Intracellular Kar2p was found to bind exclusively to the unprocessed immunotoxin containing the prosequence of alpha-factor in the endoplasmic reticulum. These results show that Kar2p is intimately involved in immunotoxin secretion in P. pastoris. The limited capacity of P. pastoris to retain a sufficiently high level of intracellular Kar2p may be a factor restricting the production of the immunotoxin.
Appl Environ Microbiol 2005 Sep
PMID:Overexpression of an anti-CD3 immunotoxin increases expression and secretion of molecular chaperone BiP/Kar2p by Pichia pastoris. 1615 Nov 22

The mono(ADP-ribosyl)ation reaction is a post-translational modification that is catalysed by both bacterial toxins and eukaryotic enzymes, and that results in the transfer of ADP-ribose from betaNAD+ to various acceptor proteins. In mammals, both intracellular and extracellular reactions have been described; the latter are due to glycosylphosphatidylinositol-anchored or secreted enzymes that are able to modify their targets, which include the purinergic receptor P2X7, the defensins and the integrins. Intracellular mono(ADP-ribosyl)ation modifies proteins that have roles in cell signalling and metabolism, such as the chaperone GRP78/BiP, the beta-subunit of heterotrimeric G-proteins and glutamate dehydrogenase. The molecular identification of the intracellular enzymes, however, is still missing. A better molecular understanding of this reaction will help in the full definition of its role in cell physiology and pathology.
FEBS J 2005 Sep
PMID:Physiological relevance of the endogenous mono(ADP-ribosyl)ation of cellular proteins. 1615 79

Numerous xenobiotics, including therapeutics agents, are substrates for bioactivation to electrophilic reactive intermediates that may covalently modify biomolecules. Selective estrogen receptor modulators (SERMs) are in clinical use for long-term therapy of postmenopausal syndromes and chemoprevention and provide a potential alternative for hormone replacement therapy (HRT). Raloxifene, in common with many SERMs and other xenobiotics, is a polyaromatic phenol that has been shown to be metabolically bioactivated to electrophilic and redox active quinoids. Nucleic acid and glutathione adduct formation have been reported, but little is known about protein covalent modification. A novel COATag (covert oxidatively activated tag) was synthesized in which raloxifene was linked to biotin. The COATag was reactive toward a model protein, human glutathione-S-transferase P1-1, in the presence but not the absence of monooxygenase. The covalent modification of proteins in rat liver microsomal incubations was NADPH-dependent implicating cytochrome P450 oxidase. The COATag facilitated isolation and identification of covalently modified microsomal proteins: cytosolic glucose regulated protein (GRP78/BiP), three protein disulfide isomerases, and microsomal glutathione S-transferase 1. Oxidative metabolism of raloxifene produces reactive intermediates of sufficient lifetimes to covalently modify proteins in tissue microsomes, behavior anticipated for other polyaromatic phenol xenobiotics that can be tested by the COATag methodology. The combined use of a COATag with a simple biotin-linked electrophile (such as an iodoacetamide tag) is a new technique that allows quantification of protein covalent modification via alkylation vs oxidation in response to xenobiotic reactive intermediates. The identification of modified proteins is important for defining pathways that might lead alternatively to either cytotoxicity or cytoprotection.
Chem Res Toxicol 2005 Sep
PMID:Analysis of protein covalent modification by xenobiotics using a covert oxidatively activated tag: raloxifene proof-of-principle study. 1616 42

Cataract is a multifactorial disease, and a large variety of stressors induce cataracts. Many cataractogenic stressors and endoplasmic reticulum (ER) stressors induce the unfolded protein response (UPR) in various cell types. The UPR is known to produce reactive oxygen species (ROS) prior to the inducement of apoptosis. We investigated whether ER stressors induce the UPR in lens epithelial cells (LECs) or whole rat lenses. Our results showed that higher levels of ER stressors activated Bip/GRP78, ATF4, and caspase-12. In addition, ROS were produced, free glutathione was decreased, and apoptosis was induced. LECs in the mitotic zone were the most susceptible to the UPR while the central LECs were the most resistant. The UPR induced the production of ROS in the ER and probably in the mitochondria. The detectable ROS production in cultured lenses is limited to the epithelial cells. These findings indicate that ER stressors induce the UPR in LECs with and without the induction of apoptosis, and we conclude that the UPR is probably one of the initiating factors of many types of cataracts.
Exp Eye Res 2006 Sep
PMID:Role of the unfolded protein response (UPR) in cataract formation. 1664

Roles for UDP-GlcNAc 2-epimerase/ManNAc 6-kinase (GNE) beyond controlling flux into the sialic acid biosynthetic pathway by converting UDP-GlcNAc to N-acetylmannosamine are described in this report. Overexpression of recombinant GNE in human embryonic kidney (HEK AD293) cells led to an increase in mRNA levels for ST3Gal5 (GM3 synthase) and ST8Sia1 (GD3 synthase) as well as the biosynthetic products of these sialyltransferases, the GM3 and GD3 gangliosides. Conversely, down-regulation of GNE by RNA interference methods had the opposite, but consistent, effect of lowering ST3Gal5 and ST8Sia1 mRNAs and reducing GM3 and GD3 levels. Control experiments ensured that GNE-mediated changes in sialyltransferase expression and ganglioside biosynthesis were not the result of altered flux through the sialic acid pathway. Interestingly, exogenous GM3 and GD3 also changed the expression of GNE and led to reduced ST3Gal5 and ST8Sia1 mRNA levels, demonstrating a reciprocating feedback mechanism where gangliosides regulate upstream biosynthetic enzymes. Cellular responses to the GNE-mediated changes in ST3Gal5 and ST8Sia1 expression and GM3 and GD3 levels were investigated next. Conditions that led to reduced ganglioside production (e.g. short hairpin RNA exposure) stimulated proliferation, whereas conditions that resulted in increased ganglioside levels (e.g. recombinant GNE and exogenous gangliosides) led to reduced proliferation with a concomitant increase in apoptosis. Finally, changes to BiP expression and ERK1/2 phosphorylation consistent with apoptosis and proliferation, respectively, were observed. These results provide examples of specific biochemical pathways, other than sialic acid metabolism, that are influenced by GNE.
J Biol Chem 2006 Sep 15
PMID:Roles for UDP-GlcNAc 2-epimerase/ManNAc 6-kinase outside of sialic acid biosynthesis: modulation of sialyltransferase and BiP expression, GM3 and GD3 biosynthesis, proliferation, and apoptosis, and ERK1/2 phosphorylation. 1684 58

In pancreatic beta cells, the endoplasmic reticulum (ER) is an important site for insulin biosynthesis and the folding of newly synthesized proinsulin. Here, we show that IRE1alpha, an ER-resident protein kinase, has a crucial function in insulin biosynthesis. IRE1alpha phosphorylation is coupled to insulin biosynthesis in response to transient exposure to high glucose; inactivation of IRE1alpha signaling by siRNA or inhibition of IRE1alpha phosphorylation hinders insulin biosynthesis. IRE1 activation by high glucose does not accompany XBP-1 splicing and BiP dissociation but upregulates its target genes such as WFS1. Thus, IRE1 signaling activated by transient exposure to high glucose uses a unique subset of downstream components and has a beneficial effect on pancreatic beta cells. In contrast, chronic exposure of beta cells to high glucose causes ER stress and hyperactivation of IRE1, leading to the suppression of insulin gene expression. IRE1 signaling is therefore a potential target for therapeutic regulation of insulin biosynthesis.
Cell Metab 2006 Sep
PMID:Regulation of insulin biosynthesis in pancreatic beta cells by an endoplasmic reticulum-resident protein kinase IRE1. 1695 Jan 32

The preemptive quality control (pQC) pathway protects cells from acute endoplasmic reticulum (ER) stress by attenuating translocation of nascent proteins despite their targeting to translocons at the ER membrane. Here, we investigate the hypothesis that the DnaJ protein p58(IPK) plays an essential role in this process via HSP70 recruitment to the cytosolic face of translocons for extraction of translocationally attenuated nascent chains. Our analyses revealed that the heightened stress sensitivity of p58-/- cells was not due to an impairment of the pQC pathway or elevated ER substrate burden during acute stress. Instead, the lesion was in the protein processing capacity of the ER lumen, where p58(IPK) was found to normally reside in association with BiP. ER lumenal p58(IPK) could be coimmunoprecipitated with a newly synthesized secretory protein in vitro and stimulated protein maturation upon overexpression in cells. These results identify a previously unanticipated location for p58(IPK) in the ER lumen where its putative function as a cochaperone explains the stress-sensitivity phenotype of knockout cells and mice.
Mol Biol Cell 2007 Sep
PMID:The role of p58IPK in protecting the stressed endoplasmic reticulum. 1756 50

We conducted a genetic yeast screen to identify Thermo-tolerance genes (TTOs) in maize kernel cDNA library. During the screening, we identified a maize clone (TTO6) that seemed to confer elevated heat tolerance in comparison to control cells. TTO6 cDNA (GenBank accession no. AY103785) encodes an 11-kDa protein which is 69% similarity to the Arabidopsis GASA4 gene. To further examine heat tolerance in Arabidopsis, we functionally characterized the GASA4 gene and found that heat induced GASA4 expression. Constitutive expression of GASA4 in Arabidopsis led to elevated heat tolerance in transgenic lines. Interestingly, endoplasmic reticulum chaperone expression analysis suggests that GASA4 influences BiP gene expression during heat stress.
Plant Physiol Biochem 2007 Sep
PMID:Enhanced tolerance to heat stress in transgenic plants expressing the GASA4 gene. 1776 29

p97 (also called VCP or Cdc48p) and E3 ubiquitin ligases are the key players in retrotranslocation and ubiquitination of substrates in the endoplasmic reticulum-associated degradation (ERAD) pathways. Although their biochemical properties have been well studied, their cellular functions in development have not been revealed. Here, we investigate cellular functions of p97 and E3 ubiquitin ligases in Caenorhabditis elegans as a model organism. We found that C. elegans possesses three E3 ubiquitin ligases (named as HRD-1, HRDL-1 and MARC-6) like mammals, and that their simultaneous depletion caused extremely delayed growth. By monitoring the expression of an ER chaperone gene, it was revealed that p97 and HRD-1 play essential roles in unfolded protein response (UPR) and ERAD pathways. We further found that HRD-1 functions in concert with BiP, and that two BiP paralogues are functionally diversified. HRD-1 and BiP(HSP-3) play important roles in the developmental growth and function of intestinal cells, while HRD-1 and BiP(HSP-4) in the gonad formation. We propose that E3 ubiquitin ligases function in concert with a specific partner chaperone.
Genes Cells 2007 Sep
PMID:ER E3 ubiquitin ligase HRD-1 and its specific partner chaperone BiP play important roles in ERAD and developmental growth in Caenorhabditis elegans. 1782 49


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