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)

Antigen stimulation of mast cells via the IgE receptor, FcepsilonRI, results in the recruitment of the cytosolic tyrosine kinase, Syk, and the activation of various signaling cascades. One of these, the extracellular signal-regulated kinase (ERK2) cascade, is inhibited by low concentrations of the immunosuppressant drug, dexamethasone, probably at a step prior to the activation of Raf-1 (Rider, L. G., Hirasawa, N., Santini, F., and Beaven, M. A. (1996) J. Immunol. 157, 2374-2380). We now show that treatment of cultured RBL-2H3 mast cells with nanomolar concentrations of dexamethasone causes dissociation of the Raf-1.heat shock protein 90 (Hsp90) complex. Raf-1 bereft of this protein fails to associate with the membrane or Ras in antigen-stimulated cells. Upstream events such as the Syk-dependent phosphorylation of Shc, the engagement of Shc with the adapter protein, Grb2, and the activation of Ras itself are unaffected. Interestingly, the counterpart of Raf-1 in the c-Jun N-terminal kinase (JNK) cascade, MEKK-1 (mitogen-activated protein kinase/ERK kinase), is similarly associated with Hsp90, and this association as well as the activation of MEKK-1 are disrupted by dexamethasone treatment. Disruption of the ERK and JNK cascades at the level of Raf-1 and MEKK-1 could account for the inhibitory action of dexamethasone on the generation of inflammatory mediators in stimulated mast cells.
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PMID:Disruption of Raf-1/heat shock protein 90 complex and Raf signaling by dexamethasone in mast cells. 1070 72

Steroid hormones (SHs) are lipophilic molecules derived from cholesterol and synthesized in the adrenal cortex (glucocorticoids, mineralocorticoids, and adrenal androgens), the testes (testicular androgens, oestrogen), and the ovary and placenta (oestrogens and progestagens or progestins). SHs reach their target cells via the blood, where they are bound to carrier proteins, and because of their lipophilic nature pass the cell membrane by simple diffusion. Within the target cells SHs bind to steroid hormone receptors (SHRs), the key mediators of SH action, which are complexed to chaperones, e.g. heat shock protein 90 (Hsp90), that help other proteins to fold and prevent aggregation. SHRs are intracellular transcription factors that can be activated, among other possibilities, by the specific and high affinity binding of ligand to exert positive or negative effects on the expression of target genes. Binding of agonistic or antagonistic ligands leads to different allosteric changes of SHRs making them competent to exert positive or negative effects on the expression of target genes by different mechanisms. (i) After dissociation of chaperones the liganded SHR-complexes can bind to chromatin organized DNA sequences in the vicinity of target genes, termed hormone response elements (HREs). The HRE-recruited hormone-receptor-complexes are then able to initiate chromatin remodelling and to relay activating or repressing signals to the target genes transcription machinery; (ii) through protein-protein interactions with other sequence-specific transcription factors, SHRs can also regulate the activity of many genes that are switched on, for instance, during stress or an inflammatory response; (iii) the SH response can also be integrated in the intracellular signalling network via cross-talk of SHRs with signal transduction pathways that transmit extracellular signals via membrane receptors and activation of protein kinase cascades to nuclear transcription factors that activate various target genes. By all these different mechanisms SHRs modulate numerous and specific responses in a large variety of cells, whereby their particular effect depends on the physiological, cellular and genetic context.
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PMID:Steroid hormone receptors: an update. 1087 67

Chronic myelogenous leukemia (CML) is a clonal disorder of a pluripotent hematopoietic stem cells characterized by a chimeric bcr-abl gene giving rise to a p210(Bcr-Abl) protein with dysregulated tyrosine kinase activity. Radicicol, a macrocyclic antifungal antibiotic, binds to the N-terminal of heat shock protein 90 (Hsp90) and destabilizes Hsp90-associated proteins such as Raf-1. This study investigated the effect of radicicol, novel oxime derivatives of radicicol (KF25706 and KF58333), and herbimycin A (HA), a benzoquinoid ansamycin antibiotic, on the growth and differentiation of human K562 CML cells. Although KF25706 and KF58333 induced the expression of glycophorin A in K562 cells, radicicol and HA caused erythroid differentiation transiently. Cell cycle analysis showed that G(1) phase accumulation was observed in K562 cells treated with KF58333. KF58333 treatment depleted p210(Bcr-Abl), Raf-1, and cellular tyrosine phosphorylated proteins in K562 cells, whereas radicicol and HA showed transient depletion of these proteins. KF58333 also down-regulated the level of cell cycle-dependent kinases 4 and 6 and up-regulated cell cycle-dependent kinase inhibitor p27(Kip1) protein without an effect on the level of Erk and Hsp90 proteins. Immunoprecipitation analysis showed that p210(Bcr-Abl) formed multiple complexes with Hsp90, some containing p23 and others Hsp70; KF58333 treatment dissociated p210(Bcr-Abl) from Hsp90/p23 chaperone complexes. Furthermore, KF58333 induced apoptosis in K562 cells and administration of KF58333 prolonged the survival time of SCID mice inoculated with K562 cells. These results suggest that KF58333 may have therapeutic potential for the treatment of CML that involves abnormal cellular proliferation induced by p210(Bcr-Abl).
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PMID:Novel oxime derivatives of radicicol induce erythroid differentiation associated with preferential G(1) phase accumulation against chronic myelogenous leukemia cells through destabilization of Bcr-Abl with Hsp90 complex. 1097 78

HL-60/Bcr-Abl cells, with ectopic expression of p185 Bcr-Abl tyrosine kinase (TK), and K562 cells, with endogenous expression of p210 Bcr-Abl TK, display a high degree of resistance against antileukemic drug-induced apoptosis (G. Fang et al., Blood, 96: 2246-2256, 2000). Present studies demonstrate that treatment with ansamycin antibiotic geldanamycin (GA), or its less toxic analogue 17-allylamino-17-demethoxygeldanamycin (17-AAG), induces cytosolic accumulation of cytochrome c and cleavage and activities of caspase-9 and caspase-3, triggering apoptosis of HL-60/Bcr-Abl and K562 cells. GA or 17-AAG down-regulated intracellular Bcr-Abl and c-Raf protein levels, as well as reduced Akt kinase activity. Similar to Raf-1, v-Src, and Her-2-neu, Bcr-Abl TK has chaperone association with heat shock protein 90 (Hsp90). By binding and inhibiting Hsp90, GA or 17-AAG treatment shifted the binding of Bcr-Abl from Hsp90 to Hsp70 and induced the proteasomal degradation of Bcr-Abl, because cotreatment with proteasome inhibitor PSC341 reduced both GA (or 17-AAG)-mediated down-regulation of Bcr-Abl levels and inhibited apoptosis of HL-60/Bcr-Abl and K562 cells. These data establish the in vitro activity of GA and 17-AAG against Bcr-Abl-positive leukemic cells and support the in vivo investigation of 17-AAG against Bcr-Abl-positive leukemias.
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PMID:Geldanamycin and its analogue 17-allylamino-17-demethoxygeldanamycin lowers Bcr-Abl levels and induces apoptosis and differentiation of Bcr-Abl-positive human leukemic blasts. 1128 Jul 26

We have previously shown that the molecular chaperone heat shock protein 90 (Hsp90) is required to ensure proper centrosome function in Drosophila and vertebrate cells. This observation led to the hypothesis that this chaperone could be required for the stability of one or more centrosomal proteins. We have found that one of these is Polo, a protein kinase known to regulate several aspects of cell division including centrosome maturation and function. Inhibition of Hsp90 results in the inactivation of Polo kinase activity. It also leads to a loss in the ability of cytoplasmic extracts to complement the failure of salt-stripped preparations of centrosomes to nucleate microtubules. This effect can be rescued upon addition of active recombinant POLO: We also show that Polo and Hsp90 are part of a complex and conclude that stabilization of Polo is one of the mechanisms by which Hsp90 contributes to the maintenance of functional centrosomes.
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PMID:Requirement of Hsp90 for centrosomal function reflects its regulation of Polo kinase stability. 1138 20

We used suppression subtractive hybridization to identify highly expressed genes in the cancerous region of human renal cell carcinoma (RCC) compared with noncancerous tissue. Nine genes were identified to show increased expression in the cancerous region compared with the noncancerous region. The nine genes included thymosin beta4, secreted protein acidic and rich in cysteine (SPARC), Cap43, ceruloplasmin, serum amyloid A, osteopontin, heat shock protein 90 (HSP90), LOT1, and casein kinase I. Of these 9 genes, in situ hybridization with 10 clinical samples consistently showed a strong expression of Cap43 mRNA in infiltrating macrophages in RCCs, but not in cancer cells proliferating in an alveolar pattern. However, Cap43 mRNA was also apparently detected in epithelial cells of the renal proximal tubuli in noncancerous tissue. The higher expression of the Cap43 gene in the cancerous region of RCCs appears to depend on macrophage infiltration. Moreover, treatment with phorbol ester resulted in enhanced expression of the Cap43 gene in human monocytic cells in vitro. The expression of the Cap43 gene in infiltrating macrophages is discussed in association with the differentiated or activated status of monocyte/macrophage.
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PMID:High expression of the Cap43 gene in infiltrating macrophages of human renal cell carcinomas. 1144 34

A requirement for cyclin D2 in G(1)-to-S phase progression has been definitively established in mature B cells stimulated via the B cell antigen receptor (BCR). However, the identity of constituents of the BCR signaling cascade that leads to cyclin D2 accumulation remains incomplete. We report that inhibition of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)-1/2 blocked BCR-induced activation of extracellular signal-regulated kinase (ERK). Inhibition of the MEK1/2-ERK pathway was sufficient to abrogate BCR-induced cyclin D2 expression at the mRNA and protein levels. Disruption of endogenous heat shock protein 90 (hsp90) function with geldanamycin abrogated BCR-induced cyclin D2 expression and proliferation. Geldanamycin effects were attributed to a selective depletion of cellular Raf-1 that interrupted BCR-coupled activation of MEK1/2 and ERK. By contrast, signaling through the phosphatidylinositol 3-kinase and protein kinase C pathways was not affected, suggesting that disruption of hsp90 function did not cause a general impairment of BCR signaling. These results suggest that the MEK1/2-ERK pathway is essential for BCR signaling to cyclin D2 accumulation in ex vivo splenic B lymphocytes. Furthermore, these findings imply that hsp90 function is required for BCR signaling through the Raf-1-MEK1/2-ERK pathway but not through the phosphatidylinositol 3-kinase- or protein kinase C-dependent pathways.
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PMID:Requirement for a hsp90 chaperone-dependent MEK1/2-ERK pathway for B cell antigen receptor-induced cyclin D2 expression in mature B lymphocytes. 1182 72

Interactions between the protein kinase C (PKC) and Chk1 inhibitor UCN-01 and the heat shock protein 90 (Hsp90) antagonist 17-AAG have been examined in human leukemia cells in relation to effects on signal transduction pathways and apoptosis. Simultaneous exposure (30 hours) of U937 monocytic leukemia cells to minimally toxic concentrations of 17-AAG (eg, 400 nM) and UCN-01 (eg, 75 nM) triggered a pronounced increase in mitochondrial injury (ie, loss of mitochondrial membrane potential [Deltapsim]; cytosolic release of cytochrome c), caspase activation, and apoptosis. Synergistic induction of apoptosis was also observed in other human leukemia cell types (eg, Jurkat, NB4). Coexposure of human leukemia cells to 17-AAG and the PKC inhibitor bisindolylmaleimide (GFX) did not result in enhanced lethality, arguing against the possibility that the PKC inhibitory actions of UCN-01 are responsible for synergistic interactions. The enhanced cytotoxicity of this combination was associated with diminished Akt activation and marked down-regulation of Raf-1, MEK1/2, and mitogen-activated protein kinase (MAPK). Coadministration of 17-AAG and UCN-01 did not modify expression of Hsp90, Hsp27, phospho-JNK, or phospho-p38 MAPK, but was associated with further p34cdc2 dephosphorylation and diminished expression of Bcl-2, Mcl-1, and XIAP. In addition, inducible expression of both a constitutively active MEK1/2 or myristolated Akt construct, which overcame inhibition of ERK and Akt activation, respectively, significantly attenuated 17-AAG/UCN-01-mediated lethality. Together, these findings indicate that the Hsp90 antagonist 17-AAG potentiates UCN-01 cytotoxicity in a variety of human leukemia cell types and suggest that interference with both the Akt and Raf-1/MEK/MAP kinase cytoprotective signaling pathways contribute to this phenomenon.
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PMID:Synergistic antileukemic interactions between 17-AAG and UCN-01 involve interruption of RAF/MEK- and AKT-related pathways. 1273 74

We previously identified 9 genes (i.e., thymosin beta4, secreted protein acidic and rich in cysteine, Cap43, ceruloplasmin, serum amyloid A, heat shock protein 90, LOT1, osteopontin and casein kinase Igamma) that are more highly expressed in cancerous regions than in noncancerous regions in human renal cancers. In our study, we considered the possibility that the von Hippel-Lindau (VHL) tumor suppressor gene might be able to affect the expression of these 9 genes in renal cancer cells. We first established 2 VHL-positive cell lines, 786/VHL-1 and 786/VHL-2, after the introduction of wild-type VHL into VHL-negative renal cancer 786-O cells. Of these 9 genes, expression of the Cap43 gene was specifically downregulated by VHL. Expression of Cap43 was also much lower in 4 other VHL-positive renal cancer cell lines than in VHL-negative 786-O cells. Cap43 promoter assays with several deletion or mutation constructs demonstrated that the Sp1 site in the element from -286 base pairs (bp) to -62 bp was partly responsible for VHL-induced suppression of the Cap43 gene. Immunostaining analysis with human specimens of renal cancers demonstrated that the Cap43 protein was expressed in most cancer cells and macrophages. We also observed a marked and specific increase of Cap43 mRNA levels in response to hypoxia or nickel in all VHL-positive cell lines. Cellular expression of Cap43 mRNA in response to hypoxia or nickel thus is closely associated with VHL gene expression in renal cancer cells. Although the function of the Cap43 protein remains unclear, the expression of Cap43 protein could be a molecular marker closely associated with VHL in renal cancer.
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PMID:Downregulation of Cap43 gene by von Hippel-Lindau tumor suppressor protein in human renal cancer cells. 1276 66

Radicicol (1), a macrocyclic antifungal antibiotic, is the lead compound of a novel class of heat shock protein 90 (Hsp90) inhibitors that result in the inhibition or degradation of Hsp90-associated proteins, such as v-src and Raf-1 kinases. New O-carbamoylmethyloxime derivatives of 1 were synthesized and evaluated for their in vitro antiproliferative activities against v-src- and K-ras-transformed cells and for their inhibitory activity against v-src tyrosine kinase. O-(Piperidinocarbonyl)methyloxime 9b, one of the most potent of these derivatives, exhibited more potent antiproliferative activity than 1 and its hydroxime KF25706 (2) and had an IC(50) of 25 nM for the inhibition of v-src kinase activity. Compound 9b was also found to decrease the Raf-1 protein level of KNRK5.2 cells. Furthermore, compound 9b exhibited significant antitumor activity when tested against MX-1 and A431 xenografts in nude mice.
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PMID:Synthesis and antitumor activity of novel O-carbamoylmethyloxime derivatives of radicicol. 1277 56


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