Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Starfish oocyte maturation was blocked by the addition of 100 microM MG115, a potent proteasome inhibitor, whereas no inhibition was observed by membrane permeable cysteine protease inhibitor, E-64-d. The inhibition by MG115 was diminished by adding at a time corresponding to the half time required for germinal vesicle breakdown. Potent inhibition of germinal vesicle breakdown was also observed by microinjection of anti-proteasome-a-subunit antibodies. The antibody-injected oocytes failed to activate pre-maturation promoting factor (pre-MPF), since the dephosphorylation of phospho-Tyr15 in cdc2 kinase was not observed even in the presence of 1-methyadenine, a maturation-inducing hormone. These results indicate that the proteasome triggers the activation of pre-MPF via the dephosphorylation of cdc2 kinase in the signal transduction pathway in response to the hormonal stimulus during starfish oocyte maturation.
 ...
PMID:The proteasome is an essential mediator of the activation of pre-MPF during starfish oocyte maturation. 922 22

The tumor suppressor p53 and its target the CDK inhibitor p21 (Cip1/Waf1) are key components of the cellular response to DNA damage. Insight into how p21 is regulated in normal cells, and how it may be deregulated in tumor cells is important for the understanding of tumorigenesis. p21 was induced in normal human diploid fibroblasts after UV irradiation-induced DNA damage, but, at a high dose of UV irradiation, a faster mobility form of p21 on SDS-PAGE (designated p21delta) was expressed. Surprisingly, in a variety of growing transformed cell lines, the level of p21 was low but p21delta was prominent. We found that p21delta appeared to be derived through a loss of around 10 amino acids from the C-terminus of p21, which theoretically would remove the PCNA binding domain, a second cyclin binding domain and the nuclear localization signal sequence. Several characteristics distinguish p21 from p21delta. Both the full length p21 and p21delta could be stabilized by a proteasome inhibitor, but only the full length p21 was associated with Cdk2 and PCNA. Consistent with this, gel filtration chromatography revealed that all the full length p21 in the cell was complexed to other proteins, whereas a significant portion of p21delta was in monomeric form. Moreover, p21 was mainly localized to the nucleus, but p21delta was mainly localized to the cytoplasm. We propose that the decrease in p21 and increase in p21delta could contribute to the deregulation of the cell cycle, and could be a mechanism involved in cellular transformation.
 ...
PMID:Expression of a novel form of p21Cip1/Waf1 in UV-irradiated and transformed cells. 954 35

The immunosuppressant rapamycin has been shown previously to inhibit the G1/S transition in several cell types by prolonging the G1 phase of the cell cycle. This process appears to be controlled, in part, by the rapamycin-sensitive FK506-binding protein-rapamycin-associated protein-p70 S6 kinase (p70(S6k)) pathway and the cyclin-dependent kinases (Cdk). We now show that in serum-stimulated NIH 3T3 cells, rapamycin treatment delays the accumulation of cyclin D1 mRNA during progression through G1. Rapamycin also appears to affect stability of the transcript. The combined transcriptional and post-transcriptional effects of the drug ultimately result in decreased levels of cyclin D1 protein. Moreover, degradation of newly synthesized cyclin D1 protein is accelerated by rapamycin, a process prevented by inclusion of the proteasome inhibitor, N-acetyl-Leu-Leu-norleucinal. The overall effect of rapamycin on cyclin D1 leads, in turn, to impaired formation of active complexes with Cdk4, a process which triggers retargeting of the p27(Kip1) inhibitor to cyclin E/Cdk2. In view of this novel experimental evidence, we discuss a possible mechanism for the rapamycin-induced cell cycle arrest at the G1/S transition.
 ...
PMID:Rapamycin inhibition of the G1 to S transition is mediated by effects on cyclin D1 mRNA and protein stability. 960 54

In search for angiogenesis inhibitors, we tested protease and proteasome inhibitors for the induction of G1 arrest and selective inhibition of growth of human umbilical vein endothelial cells (HUVECs). Serine protease-, cysteine protease-, aspartate protease-, and aminopeptidase-inhibitors did not inhibit bFGF/FBS-induced S-phase induction in HUVECs, but a proteasome inhibitor, lactacystin did inhibit it reversibly. Lactacystin increased the cellular level of p53 and cdk2-associated p21WAF1/CIP1 leading to cdk2 inactivation. In addition to the angiogenesis inhibitor TNP-470, lactacystin also inhibited the growth of HUVECs selectively at about a 20 times lower concentration than that of other human cell lines, including normal fibroblasts and carcinoma cells. Lactacystin induced p53-dependent p21WAF1/CIP1 expression at lower concentrations in HUVECs than in other cells. These cellular effects were also observed with a tripeptide-type proteasome inhibitor, N-Ac-Leu-Leu-norleucinal.
 ...
PMID:Induction of G1 arrest and selective growth inhibition by lactacystin in human umbilical vein endothelial cells. 1062 38

Ubiquitin-mediated proteolysis controls intracellular levels of various cell cycle regulatory proteins, and its inhibition has been shown to induce apoptosis in proliferating cells. In the present study, we examined induction of apoptosis in oral squamous cell carcinoma (OSCC) cells by treatment with specific proteasome inhibitors, carbobenzoxy-L-leucyl-L-leucyl-L-norvalinal and lactacystin. In all three OSCC cell lines examined, apoptotic changes such as apoptotic body formation and DNA fragmentation were observed at various degrees after 24 h of the carbobenzoxy-L-leucyl-L-leucyl-L-norvalinal or lactacystin treatment. HSC2 cells showed the most prominent apoptotic changes among the cell lines examined and demonstrated the highest level of accumulation of p27Kip1 protein after the treatment with proteasome inhibitor. Reduced expressions of cyclin D1 and phospho pRb were also observed after the treatment with proteasome inhibitor. Moreover, 12 h of treatment with the proteasome inhibitor inhibited cdk2/cyclin E kinase activity and increased the ratio of the cell cycle population at the G1 phase. The proteasome inhibitor led to inhibition of cell cycle progression. In addition, activation of CPP32 and reduced expression of Bcl-2 were observed. Because apoptosis induced by the proteasome inhibitor was inhibited by treatment with antisense p27Kip1 oligonucleotide, accumulation of the p27Kip1 protein might play an important role in the apoptosis induced by proteasome inhibitor. The present results suggest that inhibition of proteasome function may be used as a possible target of novel therapy for OSCC.
 ...
PMID:p27Kip1 accumulation by inhibition of proteasome function induces apoptosis in oral squamous cell carcinoma cells. 1074 16

We studied the ability of F9 teratocarcinoma cells to arrest in G1/S and G2/M checkpoints after gamma-irradiation. Wild-type p53 protein was rapidly accumulated in F9 cells after gamma-irradiation, however, this was followed not by a G1/S arrest but by a short and reversible delay of the cell cycle in G2/M. In order to elucidate the reasons of the lack of G1/S arrest in F9 cells, we investigated the expression of p53 downstream target Cdk inhibitor p21WAF1/CIP1. In spite of p53-dependent activation of p21WAF1/CIP1 gene promoter and p21WAF1/CIP1 mRNA accumulation upon irradiation, the p21WAF1/CIP1 protein was not detected by either immunoblot or immunofluorescence techniques. However, the cells treated with a specific proteasome inhibitor lactacystin revealed the p21WAF1/CIP1 protein both in non-irradiated and irradiated cells. Therefore we suggest that p21WAF1/CIP1 protein is degraded by a proteasome-dependent mechanism in F9 cells and the lack of G1/S arrest after gamma-irradiation is due to this degradation. We also examined the expression and activity of cell cycle regulatory proteins: G1- and G2-cyclins and cyclin-dependent kinases. In the absence of functional p21WAF1/CIP1 inhibitor, the activity of G1 cyclin/Cdk complexes was insufficiently inhibited to cause a G1 arrest, whereas a decrease of cdc2 and cyclin B1-associated kinase activities was enough to contribute to a reversible G2 arrest following gamma-irradiation. After gamma-irradiation, the majority of F9 cells undergo apoptosis implying that wt-p53 likely triggers pro-apoptotic gene expression in DNA damaged cells. Elimination of defected cells might ensure maintenance of genome integrity in the remaining cell population.
 ...
PMID:F9 embryonal carcinoma cells fail to stop at G1/S boundary of the cell cycle after gamma-irradiation due to p21WAF1/CIP1 degradation. 1095 79

Selected 20-epi and 20-normal vitamin D(3) analogs were studied. First, point mutations were introduced into human vitamin D receptor (VDR) to identify residues important for ligand binding. In helices three, four and five, His229, Asp232, Ser237 and Arg274 seem to have an important role in the binding of calcitriol. Surprisingly, the 20-epi analog MC 1288 did not bind to Ser237. Second, the effects of analogs on VDR degradation were studied. The transcriptionally active 20-epi analogs protected VDR against degradation more efficiently than the 20-normal analogs and calcitriol. With proteasome inhibitor MG-132 formation of Sug-1-RXRbeta-VDR-VDRE complex was detected. The 20-epi analogs effectively prevented its formation. Thus, the 20-epi analogs induce a VDR conformation, which prevents binding of factors mediating VDR degradation. Third, the analogs were found to be powerful regulators of cell cycle progression in MG-63 cells. They arrested cell cycle in the G0/G1 phase at lower concentrations and earlier time points than calcitriol. This was accompanied by hypophosphorylation of Rb followed by strong inhibition of Cdk2 activity. This correlated with increased levels of p27. Cdk2 and cyclin E levels were downregulated but those of p21 and cyclin D1 were not affected. Thus, a similar sequence of events with calcitriol and the analogs in inhibiting MG-63 cell growth was detected but the analogs had much longer lasting and stronger effects than calcitriol. A unifying scheme for the varying effects of vitamin D(3) analogs is presented.
 ...
PMID:Vitamin D(3) analogs (MC 1288, KH 1060, EB 1089, GS 1558, and CB 1093): studies on their mechanism of action. 1117 29

IFNs are a family of cytokines involved in antiviral defense, cell growth regulation and immune activation. IFNs either inhibit cell proliferation or control apoptosis depending on factors such as cell type and state of cell differentiation. It is important to determine how IFN-induced gene products interact with other cellular proteins to produce these responses. We have investigated the effect of IFNalpha 2b on a human small cell lung carcinoma (SCLC) cell line H82. We have found that IFNalpha efficiently induces apoptosis in H82 cells. The induction of apoptosis by IFNalpha 2b is accompanied by decreased levels of c-myc and Cdk2. We have also observed that in H82 cells IFNalpha induces downregulation of p27 and this is in contrast to the upregulation of p27 observed in other cell types where IFNs induce cell cycle arrest. IFNalpha-induced downregulation of p27 is due to protein destabilization and can be prevented by the proteasome inhibitor LLnL. The data suggest that in H82 cells, IFNalpha 2b induces degradation of p27Kip1 independently of CDK2 kinase activity and through a ubiquitin or ubiquitin-related pathway and that the degradation of p27Kip1 could be a molecular event of importance for IFN-induced apoptosis in cancer cells.
 ...
PMID:IFNalpha 2b induces apoptosis and proteasome-mediated degradation of p27Kip1 in a human lung cancer cell line. 1118 68

GL331 is a novel podophyllotoxin-derived compound. In this study, GL331 induced human lung adenocarcinoma cell line CL1-5 growth arrest before death during the initial 24-h incubation period. We found that GL331 had no inhibitory effect on the expression of cyclins E, A, B1, CDK 4, and CDK 2; instead, its cell growth-inhibitory effect was partly attributable to an early down-regulation of cyclin D1 expression and in turn the reduction of retinoblastoma protein phosphorylation. GL331 enhanced the proteolysis of cyclin D1, and a proteasome inhibitor was able to block GL331-caused cyclin D1 reduction, suggesting that GL331-stimulated cyclin D1 degradation was through proteasomal processes. Additionally, GL331 reduced cellular cyclin D1 mRNA level down to 45% of control in 4 h and further to around 20% in 12 h. However, GL331 did not accelerate the disappearance of cyclin D1 mRNA under the condition of transcription blockage induced by actinomycin D. It was reported that a certain region in the 3'-untranslated region (UTR) of cyclin D1 mRNA mediated the mRNA degradation upon extracellular stresses. Herein, transient transfection studies demonstrated that the 3'-UTR insertion did not confer the susceptibility of luciferase reporter gene to the GL331 treatment. Together, these data suggested that GL331 did not decrease the stability of cyclin D1 mRNA. On the other hand, we found that GL331 specifically inhibited the cyclin D1 promoter-driven luciferase reporter activity. Western blot analyses showed that GL331 decreased the level of phosphorylated extracellular signal-regulated kinase (Erk), with no effect on p38 or c-Jun NH(2)-terminal kinase. Furthermore, GL331's inhibition of cyclin D1 promoter was attenuated by ectopic Erk-2 overexpression. These data suggested that GL331 inhibited cyclin D1 gene transcription via the Erk signaling pathway. In summary, we report that GL331 induced an early decline of cyclin D1 expression by dual mechanisms: 1) enhancement of protein turnover and 2) repression of Erk-mediated gene transcription.
 ...
PMID:GL331 induces down-regulation of cyclin D1 expression via enhanced proteolysis and repressed transcription. 1156 39

Treatment of MCF 7 cells with the fungal estrogen zearalenone induced cyclin E-associated kinase activity transiently within 9-12 h; total cyclin-dependent kinase (Cdk) 2 activity was elevated for 24 h and beyond. This increased cyclin E/Cdk2 activity was associated with sequestration of the Cdk inhibitor p27 Cdk inhibitor 1B (p27(KIP1)) by newly formed cyclin D1/Cdk4 complexes and with downregulation of p27(KIP1) expression. The activation of cyclin A/Cdk2 activity corresponded with virtual elimination of p27(KIP1). The activity of cyclin E/Cdk2 complexes from zearalenone-treated lysates was inhibited in vitro by recombinant p27(KIP1), and this inhibition was relieved by the addition of recombinant cyclin D1/Cdk4 complexes. Thus, sequestration of p27(KIP1) by cyclin D1/Cdk4 resulted in activation of Cdk2 in vitro. Cdk inhibitory activity in lysates of zearalenone-treated cells was depleted by anti-p27(KIP1) and anti-Cdc2 interacting protein (p21(CIP1)) antibodies. Overexpression of the Cdk4/6-specific Cdk inhibitor of Cdk4 p16(INK4A) was associated with increased association of p27(KIP1) with Cdk2, concomitant with disruption of D cyclin/Cdk4 complexes. The proteasome inhibitor 2-leu-leu-leu-H aldehyde (MG-132) was relatively ineffective in inhibiting the initial, sequestration-dependent activation of cyclin E/Cdk2 yet was as effective as p16(INK4A) in inhibiting activation of cyclin A/Cdk2 later in G(1). Downregulation of p27(KIP1) proceeded in p16(INK4A)-expressing cells after zearalenone treatment, and G(1) arrest afforded by p16(INK4A) expression was reversible upon prolonged treatment with zearalenone. Zearalenone treatment of MCF-7 cells elicited expression of F-box protein S phase kinase-associated protein 2 (p45(SKP2)), a substrate-specific component of the ubiquitin-ligase complex that targets p27(KIP1) for degradation in the proteasome. These studies suggest that both sequestration of Cdk inhibitors by cyclin D1/Cdk4 complexes and downregulation of p27(KIP1) play major roles in the induction of Cdk2 activity and S phase entry elicited by estrogens in MCF-7 cells.
 ...
PMID:Removal of Cdk inhibitors through both sequestration and downregulation in zearalenone-treated MCF-7 breast cancer cells. 1211 22


1 2 3 4 Next >>