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 postnatal differentiation of sarcoplasmic reticulum (SR) of rabbit skeletal muscles (the slow-twitch soleus and the fast-twitch adductor muscles) was monitored between Days 1 and 12 by following on Western blots the expression and accumulation of molecular markers specific not only for the muscle endomembrane system, i.e., calsequestrin (CS) and the ryanodine-sensitive Ca2+ release channel, but also for the endoplasmic reticulum (ER) at large, i.e., BiP, calnexin (CN) and calreticulin. Our results demonstrate that SR development, documented by the increase of the SR fractional volume, terminal cisternae proliferation, and reorientation of triads, is accompanied by the accumulation of the SR-specific proteins and also of CN, with no change of the other ER general markers. Moreover, the distribution of two of the markers, BiP and CS, was investigated by immunocytochemistry at both the light and the electron microscope level. At Day 1 CS was found to be concentrated both within the few recognizable triad terminal cisternae and within the lumen of numerous, apparently discrete cisternae and tubules, widely scattered throughout both the contractile and the subplasmalemmal areas of the cytoplasm. These structures remain evident until Day 12, when most triad junctions have acquired proper configuration, composition and orientation. BiP, on the other hand, appears widely distributed within the ER/SR of the fibers. From the early stages of postnatal development it does colocalize with the Ca2+ binding protein in the lumen of the CS-rich structures and appears also within the longitudinal SR and the conventional ER cisternae.
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PMID:The endoplasmic reticulum-sarcoplasmic reticulum connection. II. Postnatal differentiation of the sarcoplasmic reticulum in skeletal muscle fibers. 822 98

The major proteins in the lumen of the endoplasmic reticulum (ER) are thought to function in Ca2+ sequestration or as "molecular chaperones" in the folding and assembly of membrane or secreted proteins. Based on the ability of many chaperones to bind selectively to unfolded proteins and to dissociate from them upon ATP hydrolysis, we developed an affinity chromatography method to isolate proteins with these characteristics from pancreatic or liver ER. Seven ER proteins bound selectively to denatured protein columns and were specifically eluted by ATP (10(-6) M) but not by a nonhydrolyzable ATP analog. These proteins were identified with antibodies and microsequencing as the ER chaperone BiP (grp78), grp94, calreticulin, a novel 46-kDa protein that binds azido-ATP, as well as three members of the thioredoxin superfamily: protein-disulfide isomerase, ERp72, and a previously reported 50-kDa protein (p50). This set of seven proteins bound to and was eluted with ATP from a variety of denatured proteins, including histone, gelatin, alpha fetoprotein, thyroglobulin, lysozyme, casein, and IgG. The release of grp94, protein-disulfide isomerase, ERp72, calreticulin, and p50 was stimulated by Ca2+ in the presence of ATP. These proteins thus appear to function as Ca(2+)-dependent chaperones, which may account for the Ca2+ and ATP requirement for protein folding in the ER.
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PMID:A set of endoplasmic reticulum proteins possessing properties of molecular chaperones includes Ca(2+)-binding proteins and members of the thioredoxin superfamily. 829 23

It has been shown previously that CaBP2, the rat analog of the murine protein ERp72, and CaBP1, the rat analogue of the hamster protein P5, represent members of the protein disulfide isomerase (PDI) family and are able to catalyze the reduction of insulin in the presence of various reductants (Nguyen Van et al., 1993). We have now examined the abilities of CaBP2 and CaBP1 to catalyze the renaturation of denatured reduced model proteins. Both CaBP2 and CaBP1 catalyzed the reappearance of the biological activity of the denatured reduced Fab fragment of a monoclonal anti-human creatine phosphokinase antibody. The reaction rate was positively correlated with the amount of CaBP2 or CaBP1 and dependent on the GSH/GSSG ratio (maximum at GSH/GSSG = 1). Peptide prolyl-cis,trans-isomerase (PPI), which catalyzed some renaturation on its own, showed synergistic effects with PDI, CaBP2, and CaBP1. No synergistic effects could be observed when the combinations CaBP2 + PDI, CaBP1 + PDI, or CaBP2 + CaBP1 were tested. Variation of [Ca2+] between 0 and 1 mM did not have any effect on the rate or amount of renaturation catalyzed by CaBP2, CaBP1, or PDI, nor were these parameters affected by the simultaneous presence of BiP or grp94. Both CaBP2 and CaBP1 catalyzed also the renaturation of denatured reduced ribonuclease AIII in a way that depended on the amounts of CaBP2 or CaBP1 and on the redox potential of the redox system used (GSH/GSSG or CSH/CSSC). PPI alone had no effect on the rate of RNase AIII renaturation and did not significantly affect renaturation catalyzed by PDI, CaBP2, or CaBP1. PDI showed a moderate but significant synergism with CaBP2, and a strong synergism with CaBP1. The results indicate that both CaBP2 and CaBP1 can catalyze the formation of disulfide bonds and protein disulfide isomerization and may thus be involved in the folding of nascent proteins in the secretory pathway. This does not exclude the possibility of additional functions of these proteins in the pre-Golgi compartments.
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PMID:Effects of CaBP2, the rat analog of ERp72, and of CaBP1 on the refolding of denatured reduced proteins. Comparison with protein disulfide isomerase. 830 May 76

Thapsigargin, a tumour-promoting sesquiterpene lactone, selectively inhibits the Ca(2+)-ATPase responsible for Ca2+ accumulation by the endoplasmic reticulum (ER). Mobilization of ER-sequestered Ca2+ to the cytosol and to the extracellular fluid subsequently ensues, with concomitant alteration of cellular functions. Thapsigargin was found to serve as a rapid, potent and efficacious inhibitor of amino acid incorporation in cultured mammalian cells. At concentrations mobilizing cell-associated Ca2+ to the extracellular fluid, thapsigargin provoked extensive inhibition of protein synthesis within 10 min. The inhibition in GH3 pituitary cells involved the synthesis of almost all polypeptides, was not associated with increased cytosolic free Ca2+ concentration ([Ca2+]i), and was not reversed at high extracellular Ca2+. The transient rise in [Ca2+]i triggered by ionomycin was diminished by thapsigargin. Polysomes failed to accumulate in the presence of the drug, indicative of impaired translational initiation. With longer (1-3 h) exposures to thapsigargin, recovery of translational activity was observed accompanied by increased synthesis of the ER protein glucose-regulated stress protein 78 or immunoglobulin heavy-chain binding protein ('GRP78/BiP') and its mRNA. Such inductions were comparable with those observed previously with Ca2+ ionophores which mobilize the cation from all intracellular sequestered sites. Actin mRNA concentrations declined significantly during such treatments. In HepG2 cells processing and secretion of the glycoprotein alpha 1-antitrypsin were rapidly suppressed by thapsigargin. Ca2+ sequestered specifically by the ER is concluded to be essential for optimal protein synthesis and processing. These rapid effects of thapsigargin on mRNA translation, protein processing and gene expression should be considered when evaluating potential mechanisms by which this tumour promoter influences cellular events.
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PMID:Inhibition of protein synthesis and early protein processing by thapsigargin in cultured cells. 842 74

The calcium ionophore A23187 has been shown to induce the expression of a set of glucose-regulated protein (GRP) genes through the depletion of Ca2+ from the intracellular Ca2+ stores. Here we demonstrate that thapsigargin, which inhibits specifically the endoplasmic reticulum Ca(2+)-ATPase and causes a discharge of the intracellular Ca2+ store, is able to induce the transcription of two grp genes (grp78/BiP and grp94) with kinetics and magnitude similar to that of A23187. The induction of the grp genes by both reagents requires several hours of sustained treatment, in contrast to the rapid induction previously described for c-jun and c-fos. The transactivation of the rat grp78 promoter by A23187 is mediated through sequences spanning -154 to -130 and -99 to -90. Further, simultaneous mutation of two 10-base pair regions, spanning -139 to -130 and -99 to -90, severely reduced the A23187 response. The induction by thapsigargin is also partially mediated through these same promoter elements, without the involvement of the TRE and CRE-like elements of the grp78 promoter. The Ca2+ response elements are further defined by their ability to confer Ca2+ stress inducibility to a heterologous promoter. We show that subdomains of the grp78 promoter are capable of conferring the Ca2+ stress response. In particular, two copies of a 50-base pair region spanning -159 to -110, when cloned in either orientation, can confer a 5- and 9-fold induction by A23187 and thapsigargin, respectively. Our results lend support to the hypothesis that the induction of grp78 by A23187 and thapsigargin following ER Ca2+ discharge acts through a novel pathway in which a Ca2+ signal is transduced through redundant elements containing CCAAT box-like motifs flanked by GC-rich regions.
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PMID:Transactivation of the grp78 promoter by Ca2+ depletion. A comparative analysis with A23187 and the endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin. 850 25

Direct monitoring of the free Ca2+ concentration in the lumen of the endoplasmic reticulum (ER) is an important but still unsolved experimental problem. We have shown that a Ca(2+)-sensitive photoprotein, aequorin, can be addressed to defined subcellular compartments by adding the appropriate targeting sequences. By engineering a new aequorin chimera with reduced Ca2+ affinity, retained in the ER lumen via interaction of its N-terminus with the endogenous resident protein BiP, we show here that, after emptying the ER, Ca2+ is rapidly re-accumulated up to concentrations of > 100 microM, thus consuming most of the reporter photoprotein. An estimate of the steady-state Ca2+ concentration was obtained using Sr2+, a well-known Ca2+ surrogate which elicits a significantly slower rate of aequorin consumption. Under conditions in which the rate and extent of Sr2+ accumulation in the ER closely mimick those of Ca2+, the steady-state mean lumenal Sr2+ concentration ([Sr2+]er) was approximately 2 mM. Receptor stimulation causes, in a few seconds, a 3-fold decrease of the [Sr2+]er, whereas specific inhibition of the ER Ca2+ ATPase leads to an approximately 10-fold drop in a few minutes.
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PMID:Monitoring dynamic changes in free Ca2+ concentration in the endoplasmic reticulum of intact cells. 852 3

An immunoblotting technique was used to identify lymphostimulatory antigens within sized polypeptide fractions of Eimeria maxima sporozoites. Six fractions contained polypeptides that specifically stimulated the proliferation of immune lymphocytes in an in vitro assay, and polyclonal antisera were made in rabbits against these fractions. cDNA clones, isolated with antisera against a lymphostimulatory fraction of around 70 kDa, were found to encode four different antigens including a classical hsp70, a molecule homologous to an endoplasmic reticulum chaperonin (BiP/GRP), and a calcium-dependent serine/threonine protein kinase that appears homologous to a recently described molecule from Plasmodium falciparum. The protein kinase cDNA clone was overexpressed in Escherichia coli, and the recombinant antigen was found to induce both antibody and lymphoproliferative responses in chickens when administered subcutaneously. Thus, immunoblotting, in combination with in vitro lymphoproliferation assays, can be used as an initial screen for the identification of lymphostimulatory antigens from a complex pool of polypeptides, and a combination of cDNA cloning, expression, and immunization allows assessment of the lymphostimulatory activity of individual polypeptides. These studies should facilitate further evaluation of antigens that are potential candidates for inclusion in a recombinant vaccine against poultry coccidiosis.
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PMID:Nitrocellulose immunoblotting for identification and molecular gene cloning of Eimeria maxima antigens that stimulate lymphocyte proliferation. 854 29

Stress protein GRP78/BiP is highly induced in progressively growing tumors and has recently been shown to exert a protective role against lysis by cytotoxic T cells and tumor necrosis factor in vitro. This raises the question whether the in vitro observed protective function of GRP78/BiP translates into the in vivo situation in which tumors grow progressively, killing the host. Herein we report that molecular inhibition of GRP78/BiP induction in the fibrosarcoma B/C10ME, while not affecting in vitro cell proliferation, causes a dramatic increase in apoptotic cell death upon Ca2+ depletion of the endoplasmic reticulum. When B/C10ME cells incapable of inducing GRP78/BiP are injected into mice, tumors are initially formed that, however, regress presumably due to a cytotoxic T-cell response demonstrable by a strong in vitro response to the tumor with spleen cells of regressor mice. Since sensitivity to apoptosis is key to tumor rejection, these results may point to new approaches to the therapy of cancer via regulation of stress protein GRP78/BiP.
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PMID:Inhibition of tumor progression by suppression of stress protein GRP78/BiP induction in fibrosarcoma B/C10ME. 875 37

Heat shock/stress proteins (HSP) act as molecular chaperones, protect cells from injury, and are involved in the immune response. We investigated the effects of the immunomodulating bacterial extracts OM-85 on the stress response in normal human peripheral blood monocytes. While OM-85 did not induce the classical HSP, we show here, using 2D gel electrophoresis combined with immunoblotting, the induction of the glucose regulated protein grp78 (the immunoglobulin heavy chain binding protein BiP) along with the described accumulation of pro-interleukin-1 beta. The increased Ca2+ mobilization observed with OM-85 is the likely second messenger for grp78 induction. Recent studies are in favor of a protective role of grp78 against cytokine-mediated cytotoxicity and apoptosis. We suggest that grp78 induction following exposure to OM-85 explains, at least in part, the immunodulatory and protective effects of the bacterial extracts.
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PMID:Selective induction of the glucose-regulated protein grp78 in human monocytes by bacterial extracts (OM-85): a role for calcium as second messenger. 880 8

The inositol 1,4,5-trisphosphate receptor (IP3R) is an intracellular calcium channel involved in coupling cell membrane receptors to calcium signal transduction pathways within cells including endocrine cells. Several isoforms (I, II, and III) of IP3Rs have been identified, which are encoded by separate genes, and are expressed in many tissues with differing patterns of cellular expression. We have generated specific affinity-purified polyclonal anti-peptide antibodies to each of the three isoforms. Western blot analysis of RINm5F and ATt20 cells shows high levels of endogenously expressed type I and type III IP3R, but undetectable levels of type II. Immunofluorescence studies revealed an endoplasmic reticulum-like pattern similar to BiP, an ER marker. In contrast with previous claims, both type I and type III IP3Rs were absent from the secretory granules of ATt20 cells. Western blots of sucrose gradients and gel filtration probed with antibodies to either type I or type III showed a molecular weight of greater than 1,000 kDa consistent with a tetrameric structure. Co-immunoprecipitation experiments indicated that most of the receptors were present as heterotetramers. Homotetramers were identified for the type III IP3R; however, type I homotetramers were undetectable. These data suggest that molecular association of IP3Rs into heterotetrameric forms can contribute to the complexity of the regulation of Ca2+ release from ER by IP3Rs within cells.
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PMID:Inositol 1,4,5-trisphosphate receptors in endocrine cells: localization and association in hetero- and homotetramers. 881


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