Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The protein kinase C-(PKC) activating phorbol esters 12-O-tetradecanoylphorbol-13-acetate (TPA; 100 nmol/l) and phorbol 12,13-dibutyrate (PDBU; 100 nmol/l) enhanced basal cyclin AMP accumulation in cultured neonatal mouse calvaria. The cyclic AMP response to parathyroid hormone (PTH; 10 nmol/l) and the adenylate cyclase activators forskolin (1-3 mumol/l) and choleratoxin (0.1 mumg/ml) was potentiated in a more than additive manner by TPA and PDBU. In contrast, phorbol 13-monoacetate (phorb-13; 100 nmol/l), a related compound but inactive on PKC, had no effect on basal or stimulated cyclic AMP accumulation. In the presence of indomethacin (1 mumol/l), TPA and PDBU had no effect on cyclic AMP accumulation in calvarial bones per se, but were still able to cause a significant enhancement of the response to PTH, forskolin and choleratoxin. PTH-, forskolin- and choleratoxin-stimulated cyclic AMP accumulation in rat osteosarcoma cells UMR 106-01 was synergistically potentiated by TPA and PDBU, but not by phorb.-13. These data indicate that PKC enhances cyclic AMP formation and that the level of interaction may be at, or distal to, adenylate cyclase.
 ...
PMID:Protein kinase C activating phorbolesters enhance the cyclic AMP response to parathyroid hormone, forskolin and choleratoxin in mouse calvarial bones and rat osteosarcoma cells. 166 87

The cell cycle-dependent transcription factor, E2F-1, regulates the cyclin-like species of the DNA repair enzyme uracil-DNA glycosylase (UDG) gene in human osteosarcoma (Saos-2) cells. We demonstrate, through the deletion of the human UDG promoter sequences, that expression of E2F-1 activates the UDG promoter through several E2F sites. The major putative downstream site for E2F, located in the first exon, serves as a target for E2F-1/DP1 complex binding in vitro. We also provide evidence for the functional relationship between the cyclin-like UDG gene product and E2F. High levels of UDG expression in a transient transfection assay result in the down-regulation of transcriptional activity through elements specific for E2F-mediated transcription. Overexpression of UDG in Saos 2 cells was observed to delay growth late in G1 phase and transiently arrest these cells from progressing into the S phase. This hypothetical model integrates one mechanism of DNA repair with the cell cycle control of gene transcription, likely through E2F. This implicates E2F as a multifunctional target for proteins and enzymes, possibly, responsive to DNA damage through the negative effect of UDG on E2F-mediated transcriptional activity.
 ...
PMID:E2F-1 and a cyclin-like DNA repair enzyme, uracil-DNA glycosylase, provide evidence for an autoregulatory mechanism for transcription. 753 93

The representation of cyclins and cyclin-dependent kinases (cdks) was analyzed during progressive development of the bone cell phenotype in cultures of normal diploid rat calvarial osteoblasts. Three developmental stages were examined: (a) proliferation; (b) monolayer confluency; and (c) mineralization of the bone extracellular matrix. We demonstrate that the presence of cyclins and cdks is not restricted to the proliferation period. Consistent with their role in cell cycle progression, cdc2 and cdk2 decrease postproliferatively. However, cdk4 and cyclins A, B, and D1 persist in confluent cells. Cyclin E is significantly up-regulated during the extracellular matrix mineralization developmental period. Examination of the cytoplasmic levels of these cell cycle regulatory proteins indicates a marked increase in cyclin B in the late differentiation stage. The elevation of nuclear cyclin E and cytoplasmic cyclin B is not observed in osteoblasts maintained under culture conditions that do not support differentiation. Furthermore, treatment with transforming growth factor beta for 48 h during the proliferation period renders the cells incompetent for differentiation and abrogates the postproliferative up-regulation of cyclins B and E. Density-induced growth inhibition of ROS 17/2.8 osteosarcoma cells is not accompanied by up-regulation of nuclear cyclin E and cytoplasmic cyclin B when compared to the proliferation period. This observation is consistent with abrogation of both growth control and differentiation regulatory mechanisms in tumor cells. These results suggest that cell cycle regulatory proteins function not only during proliferation but may also play a role in normal diploid osteoblast differentiation.
 ...
PMID:Expression of cell cycle regulatory factors in differentiating osteoblasts: postproliferative up-regulation of cyclins B and E. 758 45

The structurally related natural products rapamycin and FK506 bind to the same intracellular receptor, FKBP12, yet the resulting complexes interfere with distinct signalling pathways. FKBP12-rapamycin inhibits progression through the G1 phase of the cell cycle in osteosarcoma, liver and T cells as well as in yeast, and interferes with mitogenic signalling pathways that are involved in G1 progression, namely with activation of the protein p70S6k (refs 5, 11-13) and cyclin-dependent kinases. Here we isolate a mammalian FKBP-rapamycin-associated protein (FRAP) whose binding to structural variants of rapamycin complexed to FKBP12 correlates with the ability of these ligands to inhibit cell-cycle progression. Peptide sequences from purified bovine FRAP were used to isolate a human cDNA clone that is highly related to the DRR1/TOR1 and DRR2/TOR2 gene products from Saccharomyces cerevisiae. Although it has not been previously demonstrated that either of the DRR/TOR gene products can bind the FKBP-rapamycin complex directly, these yeast genes have been genetically linked to a rapamycin-sensitive pathway and are thought to encode lipid kinases.
 ...
PMID:A mammalian protein targeted by G1-arresting rapamycin-receptor complex. 800 69

Protein phosphatase 1 and protein phosphatase 2A contain potential phosphorylation sites for cyclin-dependent kinases. In the present study we found that rabbit skeletal muscle protein phosphatase 1, as well as recombinant protein phosphatase 1 alpha and protein phosphatase 1 gamma 1, but not protein phosphatase 2A, was phosphorylated and inhibited by cdc2/cyclin A and cdc2/cyclin B. Phosphopeptide mapping and phospho amino acid analysis suggested that the phosphorylation site was located at a C-terminal threonine. Neither cdc2/cyclin A nor cdc2/cyclin B phosphorylated an active form of protein phosphatase 1 alpha in which Thr-320 had been mutated to alanine, indicating that the phosphorylation occurred at this threonine residue. Furthermore, protein phosphatase 1, but not protein phosphatase 2A, activity was found to change during the cell cycle of human MG-63 osteosarcoma cells. The observed oscillations in protein phosphatase 1 activity during the cell cycle may be due, at least in part, to phosphorylation of protein phosphatase 1 by cyclin-dependent kinases. Together, the results suggest a mechanism for direct regulation of protein phosphatase 1 activity.
 ...
PMID:Phosphorylation and inactivation of protein phosphatase 1 by cyclin-dependent kinases. 802 97

Cyclins are key regulatory proteins that, in concert with cyclin-dependent protein kinase subunits (cdks), function to govern critical transitions and/or restriction points during the course of cell cycle progression. Recently, a number of putative mammalian G1 cyclins have been characterized at the molecular level; however, the specific activities of the cyclin/cdk complexes and the precise biochemical pathways regulated by the G1 cyclins remain to be elucidated. In the present study we identify a novel cyclin-like protein in pediatric bone and extremity tumors that appears to be related to, but is clearly distinct from, previously identified members of the cyclin D family, as determined by its profile of antibody cross-reactivity, apparent molecular size, chromatographic behavior, physicochemical properties, and pattern of peptide mapping. This 46-kDa cyclin-like protein, tentatively designated p46cyclin X, is first expressed in synchronized MG-63 osteosarcoma cells in mid-G1, well after the induction of p36cyclin D1, yet prior to the induction of cyclins E and A. Northern analysis, utilizing an oligonucleotide probe complementary to an epitope shared by cyclins D1, D2, and X, detected a novel mRNA species, the appearance of which correlates with p46cyclin X expression. The p46cyclin X protein in Ewing's sarcomas and Wilms' tumors is electrophoretically and chromatographically distinct from both p36cyclin D1 and p34cyclin D2. Moreover, the p46cyclin X protein is 1) precipitated by p9Ckshs1-agarose beads, 2) physically associated with p33cdk2, and 3) autophosphorylated in in vitro kinase reactions. Taken together with the biochemical data, the temporal expression of the p46cyclin X/p33cdk2 kinase system is suggestive of a potential role in regulating latter G1 events (i.e. START) in the commitment to S phase.
 ...
PMID:Identification of a novel cyclin-like protein in human tumor cells. 838 71

Originally identified as a 'mitotic cyclin', cyclin A exhibits properties of growth factor sensitivity, susceptibility to viral subversion and association with a tumor-suppressor protein, properties which are indicative of an S-phase-promoting factor (SPF) as well as a candidate proto-oncogene. Other recent studies have identified human cyclin D1 (PRAD1) as a putative G1 cyclin and candidate proto-oncogene. However, the specific enzymatic activities and, hence, the precise biochemical mechanisms through which cyclins function to govern cell cycle progression remain unresolved. In the present study we have investigated the coordinate interactions between these two potentially oncogenic cyclins, cyclin-dependent protein kinase subunits (cdks) and the Rb tumor-suppressor protein. The distribution of cyclin D isoforms was modulated by serum factors in primary fetal rat lung epithelial cells. Moreover, cyclin D1 was found to be phosphorylated on tyrosine residues in vivo and, like cyclin A, was readily phosphorylated by pp60c-src in vitro. In synchronized human osteosarcoma cells, cyclin D1 is induced in early G1 and becomes associated with p9Ckshs1, a Cdk-binding subunit. Immunoprecipitation experiments with human osteosarcoma cells and Ewing's sarcoma cells demonstrated that cyclin D1 is associated with both p34cdc2 and p33cdk2, and that cyclin D1 immune complexes exhibit appreciable histone H1 kinase activity. Immobilized, recombinant cyclins A and D1 were found to associate with cellular proteins in complexes that contain the p105Rb protein. This study identifies several common aspects of cyclin biochemistry, including tyrosine phosphorylation and the potential to interact directly or indirectly with the Rb protein, that may ultimately relate membrane-mediated signaling events to the regulation of gene expression.
 ...
PMID:Two potentially oncogenic cyclins, cyclin A and cyclin D1, share common properties of subunit configuration, tyrosine phosphorylation and physical association with the Rb protein. 847 54

Cyclin A was initially characterized as a 'mitotic cyclin', believed to function exclusively at the G2-to-M phase transition; however, recent studies have provided compelling evidence that cyclin A additionally functions earlier in the mammalian somatic cell cycle as a putative 'S-phase-promoting factor'. Moreover, numerous inconsistencies have arisen concerning the temporal induction, subcellular localization, subunit configuration, covalent modification and proteolytic destruction of cyclin A, as well as the physiological function of the cyclin A-associated protein kinase complexes. Utilizing precisely synchronized human MG-63 osteosarcoma cells, the present study demonstrates that cyclin A mRNA and protein are clearly expressed in late G1 prior to S-phase entry, as is cyclin A-associated kinase activity and concomitant phosphorylation of the Rb protein. A series of monospecific cyclin A antibodies were generated and utilized to confirm that multiple covalent modifications of cyclin A occur during the course of the cell cycle, and to characterize the subcellular dynamics in additional detail. Pharmacological blockade with mimosine was utilized to further delineate cyclin A expression and to distinguish the temporal induction from the mechanisms of enzyme activation. Subcellular fractionation and immunocytochemical staining localized nascent cyclin A to the cytoplasm, and revealed a distinct translocation to the nucleus during the G1-to-S phase transition. The results of these studies support a multistage model of cyclin A metabolism and enzyme activation.
 ...
PMID:G1 expression and multistage dynamics of cyclin A in human osteosarcoma cells. 850 85

The activation of cyclin-dependent protein kinases (Cdks) is dependent upon site-specific phosphorylation and dephosphorylation reactions, as well as positive and negative regulatory subunits. The human Cdk-activating protein kinase (Cak1) is itself a Cdc2-related cyclin-dependent protein kinase that associates with cyclin H. The present study utilized specific anti-Cak1 antibodies and immunoaffinity chromatography to identify additional Cak1-associated proteins and potential target substrates. Immunoprecipitation of metabolically labeled human osteosarcoma cells revealed a number of Cak1-associated proteins, including p95, p37 (cyclin H), and a 35-kDa protein that was further characterized herein. Microsequence analysis obtained after limited proteolysis revealed peptide fragments that are similar, but not identical to, human and yeast cyclins, thus identifying p35 as a cyclin-like regulatory subunit. The greatest sequence similarity of human p35 is with Mcs2, a yeast cyclin that is essential for cell cycle progression. Immunoaffinity chromatography performed under nondenaturing conditions afforded the isolation of enzymatically active Cak1 from cell lysates, enabling studies of kinase autophosphorylation and comparative substrate utilization. Immunoaffinity-purified Cak1 phosphorylated monomeric Cdc2 and Cdk2, but not Cdk4; the phosphorylation of both Cdc2 and Cdk2 were increased in the presence of recombinant cyclin A. These studies indicate that the Cak1 catalytic subunit, like Cdc2 and Cdk2, associates with multiple regulatory partners and suggests that subunit composition may be an important determinant of this multifunctional enzyme.
 ...
PMID:Biochemical characterization of the human cyclin-dependent protein kinase activating kinase. Identification of p35 as a novel regulatory subunit. 855 Jun 4

Activation of cyclin-dependent kinases (CDKs) by interaction with cyclins regulates progression through cell cycle checkpoints. This process is counterbalanced by CDK inhibitors (CDKIs), which can inhibit progression through the cell cycle. Because CDKI expression acts to inhibit cellular proliferation, CDKIs may have a role as tumor suppressors. One class of CDKIs, characterized by the presence of ankyrin repeats, has at least four members (p15INK4B), p16INK4, p18, and p19). Two of these, p15INK4B, p16INK4, have been mapped to chromosome 9p21, a region of frequent loss in a wide variety of cancers. Alterations of p16INK4 have been detected in various tumors and cell lines. We analyzed p15INK4B, p16INK4, and p18 alterations in 52 osteosarcomas (including 11 explants), and 23 other various sarcomas. Single-stranded conformation polymorphism analysis [polymerase chain reaction (PCR-SSCP)] of the coding regions of these CDKI genes detected a missense mutation of p16INK4 exon 1 in one soft tissue sarcoma. Southern blotting detected complete deletion of p15INK4B and p16INK4 genes in osteosarcomas from 2 patients and a soft tissue sarcoma from another individual. Loss of heterozygosity (LOH) at chromosome 9p21 was observed with a microsatellite probe closely linked to the INK4 genes in the latter case. Deletions of both p15INK4B and p16INK4 genes were detected in five of eight osteosarcoma cell lines. By contrast, no alterations of p18 were detected in any sample. Together these data suggest that alterations of the p15INK4B and p16INK4 genes, but not p18, may occur in approximately 5% of sarcomas. However, deletions of the p15INK4B and P16INK4 genes are frequent in osteosarcoma cell lines and probably have a role in tumor cell growth in culture. Notably, all seven detectable deletions involved both p15INK4B and p16INK4 genes, suggesting that both contribute individual tumor suppressor activity.
 ...
PMID:Alterations of the p15, p16,and p18 genes in osteosarcoma. 860 40


1 2 3 4 5 6 7 Next >>