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: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purification and sequencing of proteins from cardiac sarcoplasmic reticulum (SR) vesicles have provided a framework for the study of SR function. Included among the SR proteins so far investigated are a collection of intralumenal proteins that stain blue with the protein dye Stains-All in sodium dodecyl sulfate-polyacrylamide gels. A single prominent blue staining SR protein of apparent M(r) = 90,000 (Band VII), however, has remained uncharacterized. In the work described here, purification of Band VII from dog cardiac SR vesicles, along with amino acid sequencing and cDNA cloning, identified this protein as calnexin, a homologue of calreticulin recently described in dog pancreatic microsomes. Using ryanodine-mediated calcium oxalate loading of SR vesicles followed by density gradient centrifugation, we have shown that calnexin is a bona fide SR protein and an integral constituent of both junctional and free SR vesicles. Calnexin was found to be a substrate for casein kinase II and was phosphorylated at two distinct sites localized to the carboxyl- and amino-terminal ends of the molecule. Enrichment of calnexin in cardiac SR vesicles indicates a role for calnexin involving the specialized function of the SR membrane.
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PMID:Purification of a 90-kDa protein (Band VII) from cardiac sarcoplasmic reticulum. Identification as calnexin and localization of casein kinase II phosphorylation sites. 842 70

Calreticulin isolated from spinach leaves has been specifically phosphorylated in vitro by protein kinase CK2 while animal calreticulin from rabbit liver is not a substrate of this kinase under the same conditions. Phosphoserine is the only phosphoamino acid detected. High affinity binding (Km = 4.4 microM) and a nearly stoichiometric incorporation of phosphate was determined. Partially purified spinach calreticulin is phosphorylated at the same site(s) by a copurifying protein kinase sharing biochemical properties very similar if not identical to those of mammalian CK2. Other plant calreticulins isolated from Liriodendron tulipifera appear to be also phosphorylated by CK2.
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PMID:Plant calreticulin is specifically and efficiently phosphorylated by protein kinase CK2. 862 90

Calcium is a second messenger that controls a wide variety of cellular functions. Because of its multiple actions, there is a stringent requirement for calcium homeostasis, and this is achieved in part by a system of transport and storage proteins such as calreticulin located in the endoplasmic reticulum. Calreticulin is also found in the nucleus, suggesting that it may have a role in transcriptional regulation. It has been reported that calreticulin can inhibit steroid-regulated gene transcription by preventing receptor binding to DNA. Here we report that overexpression of the calreticulin gene in B16 mouse melanoma cells resulted in a decrease in retinoic acid (RA)-stimulated reporter gene expression. Gel shift analysis showed that purified calreticulin inhibited the binding of endogenous RAR to a beta-RA response element oligonucleotide, only if added prior to the addition of the oligonucleotide. Co-immunoprecipitation studies suggest a physical interaction between RAR and calreticulin. Transfection of the calreticulin gene into B16 cells inhibited the RA induction of protein kinase Calpha, a marker of RA-induced differentiation. We also found that cyclic AMP increased the expression of calreticulin. Cyclic AMP may act to antagonize RA action by both decreasing RAR expression (Y. Xiao, D. Desai, T. Quick, and R. M. Niles, J. Cell Physiol., in press) and stimulating calreticulin levels.
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PMID:Inhibition of retinoic acid receptor function and retinoic acid-regulated gene expression in mouse melanoma cells by calreticulin. A potential pathway for cyclic AMP regulation of retinoid action. 866 62

We have extensively purified three of the hepatic microsomal intralumenal Ca2+-binding proteins, CBP1, CBP2, and CBP3, which were originally described by Van et al. [(1989) J. Biol. Chem. 264, 17494-17501]. These apparently homogeneous preparations showed only single 45Ca2+ binding bands. On the basis of the peptide sequence, CBP2 was found to be highly homologous with the previously described protein ERp72. Similarly, CBP3 was identical to calreticulin and CBP1 had some homology to calmodulin. Contrary to the report of Van et al. (1989), we found that CBP2 had little thiol:protein disulfide oxidoreductase activity. Of the three purified preparations, only CBP2 exhibited apparent intrinsic protein kinase activity. This activity was found to be due to contamination of the CBP2 preparation by an extremely low concentration of tightly bound casein kinase 2 (CK2). In line with this observation, the phosphorylation was inhibited by heparin, removed by antibody to CK2, and stimulated by spermine. Furthermore, CBP2 was readily phosphorylated in vitro by added CK2 but only slowly phosphorylated by several other protein kinases. Thus, the persistence of CK2 in a highly purified preparation of CBP2 along with several other lines of evidence presented in this study might suggest that the protein CBP2 is a physiologically relevant substrate for CK2. Furthermore, these data suggest that CK2 might be localized in the lumen of the endoplasmic reticulum and that the phosphorylation of CBP2 in the lumen may play a role in the chaperone activity attributed to this protein.
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PMID:Evidence that casein kinase 2 phosphorylates hepatic microsomal calcium-binding proteins 1 and 2 but not 3. 867 86

Two forms (G-I and G-II kinases) of casein kinase II(CK-II) in a partially purified CK-II fraction (Mono Q fraction) of mouse liver were separated by means of glycyrrhizin (GL)-affinity column chromatography. Biochemical characterization revealed that these two GL-binding kinases were identical to CK-II. Two phosphate acceptors [p99 (pI 7.0) and p56] copurified with CK-II were identified as ERp99 (Hsp-90-family protein) and calreticulin, respectively. Another protein [p100 (pI 9.0)], which crossreacted with anti-serum against human glucocorticoid receptor (GR), was associated with ERp99. Phosphorylation of p99 [a hetero-complex of p99 (pI 7.0) and p100 (pI 9.0)] and p56 by CK-II in vitro was stimulated significantly by low levels (1-3 microM) of GL, but inhibited significantly at doses above 20 microM. However, no effect of GL on autophosphorylation of ERp99 was detected. The data provided here suggest that GL can regulate CK-II-mediated phosphorylation involved in the GL-induced biological effects in mammalian cells.
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PMID:Identification of glycyrrhizin-binding protein kinase as casein kinase II and characterization of its associated phosphate acceptors in mouse liver. 885 10

Oligogalacturonide-induced modifications of protein phosphorylation in cells of Nicotiana tabacum L. were investigated by in-vitro phosphorylation of plasma-membrane-enriched fractions and electrophoretic analysis on two-dimensional gels. About 100 polypeptides were resolved; among these 40 phosphoproteins were detected and their 33P-labelling quantified. Most of the phosphorylations were inhibited by staurosporine and several proteins were hyperphosphorylated in the presence of okadaic acid, indicating the presence of protein phosphatase(s) in addition to staurosporine-susceptible protein kinase(s) in the plasma-membrane-enriched fraction. In the presence of oligogalacturonides, phosphorylation of seven acidic polypeptides ranging from 15 to 65 kDa was strongly enhanced. A twofold enhancement of the phosphorylation of 24-kDa protein and a two- to threefold decrease in the phosphorylation of acidic proteins of MrS 62, 65, 80 and 84 was also observed in response to oligogalacturonides. One of the oligogalacturonide-modulated phosphoproteins was identified as calreticulin by direct nucleotide sequencing after preparative two-dimensional electrophoresis and comparison with protein database sequences. Decreased phosphorylation of calreticulin was also observed in vivo, shortly after addition of oligogalacturonides to tobacco cells, confirming the biological relevance of the modification. Although the presence of calreticulin, an abundant reticuloplasmin with high calcium-binding capacity, has been reported in both mammalian and plant cells, its function is as yet largely unknown. Modulation of the phosphorylation of a plant calreticulin-like protein by oligogalacturonides is shown here, suggesting a role in the early transduction steps of this signal.
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PMID:Identification of calreticulin-like protein as one of the phosphoproteins modulated in response to oligogalacturonides in tobacco cells. 923 5

Protein kinase CK2 forms complexes with some protein substrates what may be relevant for the physiological control of this protein kinase. In previous studies in rat liver cytosol we had detected that the trimeric form of eukaryotic translation initiation factor 2 (eIF-2) co-eluted with protein kinase CK2. We have now observed that the ratio between eIF-2 and cytosolic CK2 contents in testis, liver and brain is quite similar, being eIF-2 levels about 5-fold higher than those of CK2. Furthermore eIF-2 was present in liver samples immunoprecipitated with anti-CK2alpha/alpha' antibodies, confirming the existence of complexes containing both proteins. Nonetheless, these complexes would represent only a fraction of total cytosolic CK2 and eIF-2. We had also observed that rat liver membrane glycoproteins obtained through chromatography on wheat-germ lectin-Sepharose contain CK2 activity which copurifies with grp94/endoplasmin. We have now confirmed that this activity was due to the presence of protein kinase CK2 as evidenced by immunodetection with antibodies against CK2alpha/alpha'. The fractions enriched in grp94/endoplasmin and CK2 also contained another 55-kDa polypeptide (p55) phosphorylated by CK2 which has been identified as calreticulin by N-terminal sequencing. Calreticulin and grp94/endoplasmin could be partially resolved from CK2 by chromatography on heparin-agarose and almost completely on ConA-Sepharose. However, phosphorylation of immunoprecipitated grp94/endoplasmin was enhanced by its preincubation with purified CK2 prior to immunoprecipitation, what confirms the easy reassociation between these proteins. The association of protein kinase CK2 with eIF-2 and with grp94/endoplasmin may serve to locate the enzyme in the cellular machinery involved in protein synthesis and folding, and reinforces the possible involvement of CK2 in these processes.
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PMID:Association of protein kinase CK2 with eukaryotic translation initiation factor eIF-2 and with grp94/endoplasmin. 1009 97

Calreticulin is an abundant endo/sarcoplasmic reticulum (ER/SR) protein that may carry out multiple functions inside cells. Except for calreticulin, all of the major ER/SR Ca2+-binding proteins are substrates for protein kinase CK2 in vitro, which led us to hypothesize that native calreticulin might exist in the phosphorylated form. To investigate this possibility, we purified calreticulin from cardiac microsomes and verified its identity by immunoblot analysis and sequencing of tryptic peptides. Purified calreticulin, like cardiac calsequestrin, contained endogenous phosphate as determined by a Malachite green assay for phosphate. Previous analyses of cardiac calsequestrin have localized phosphate to a single tryptic peptide containing serine phosphate on sites phosphorylated by protein kinase CK2. Using a similar procedure, we analyzed calreticulin tryptic peptides with Malachite green, localizing phosphate binding to a single calreticulin peptide 367LKEEEEDKK. As this peptide contains no phosphorylatable residues, our results suggest that calreticulin may tightly bind phosphate or a phosphate-containing molecule at this site.
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PMID:Determination of a putative phosphate-containing peptide in calreticulin. 1036 92

The developing metanephric kidney is a convenient model to study molecular events associated with epithelial cell differentiation. To determine the genes involved in the defining event of this process, namely, the conversion of metanephric mesenchyme to the epithelium of the nephron, we applied differential display (DD) techniques. Explants of rat metanephric mesenchymes were induced to condense ex vivo with fibroblast growth factor 2 (FGF2) or to form tubules with FGF2 and conditioned medium (CM) from a cell line (RUB1) of ureteric bud, the renal inductive tissue. Three time points (6, 24, and 72 h) were chosen to track the dynamics of gene expression during morphogenesis. Seventy-two up- or down-regulated mRNAs were identified, including 36 novel sequences and those of cell cycle regulatory proteins (TGF-beta2, Cyclin D1, p57Kip2), transcription factors (beta-catenin, Sox11, DP1), signaling proteins (SH3-domain binding protein, G-protein-coupled receptor, Ser-Thr protein kinase), cell adhesion molecules (syndecan-4, integrin-beta1), and also gene33, H19, SM20, IGFBP5, MAMA receptor, lectin, keratin, beta-tubulin, calreticulin, GRP78, ERp72, MnSoD, thioredoxin, and others. Some have previously been associated with kidney development and serve as good controls for expected changes, while most have not been linked with kidney epithelial cell differentiation. Using thin sections of embryonic kidney and labeled antisense RNA probes, we applied RNA hybridization to confirm the results of DD and related the expression of these genes to specific cell lineages of the developing kidney. These results provide a window into the events that mediate this critical differentiation process and suggest that a limited number of interrelated events direct the epithelial conversion of metanephric mesenchyme. genesis 27:22-31, 2000. Published 2000 Wiley-Liss, Inc.
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PMID:Mesenchymal-epithelial transition in the developing metanephric kidney: gene expression study by differential display. 1086 52

Disuse atrophy of skeletal muscle leads to an upregulation of genes encoding sarcoplasmic reticulum (SR) calcium-handling proteins. Because many of the proteins that are induced with endoplasmic reticulum (ER) stress are ER calcium-handling proteins, we sought to determine whether soleus muscle atrophy was associated with a prototypical ER stress response. Seven days of rat hindlimb unloading did not alter expression of ubiquitous ER stress proteins such as Grp78, calreticulin, and CHOP/GADD-153, nor other proteins that have been shown to be activated by ER stressors such as vinculin, the type I D-myo-inositol 1,4,5-trisphosphate receptor, or protein kinase R, a eukaryotic initiation factor 2 alpha kinase. On the other hand, expression of heme oxygenase-1 (HO-1), an antioxidant ER stress protein, was significantly increased 2.2-fold. In addition, unloading led to an increase in calsequestrin, the muscle-specific SR calcium-binding protein, at both the mRNA (68%) and protein (24%) levels. Although disuse atrophy is associated with a significant remodeling of muscle-specific proteins controlling SR calcium flux, it is not characterized by a prototypical ER stress response. However, the upregulation of HO-1 may indicate ER adaptation to oxidative stress during muscle unloading.
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PMID:Expression of endoplasmic reticulum stress proteins during skeletal muscle disuse atrophy. 1154 66


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