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

The cyclin-dependent kinases are key cell cycle regulators whose activation is required for passage from one cell cycle phase to the next. In mammalian cells, CDK2 has been implicated in control of the G1 and S phases. We have used a two-hybrid protein interaction screen to identify cDNAs encoding proteins that can interact with CDK2. Among those identified was a protein (KAP), which contained the HCXX-XXGR motif characteristic of protein tyrosine phosphatases. KAP showed phosphatase activity toward substrates containing either phosphotyrosine or phosphoserine residues. Since KAP is not significantly similar to known phosphatases beyond the catalytic core motif, it represents an additional class of dual specificity phosphatase. KAP interacted with cdc2 and CDK2 in yeast. In mammalian cells, KAP also associated with cdc2 and CDK2 but showed a preference for cdc2. The ability of KAP to bind multiple cyclin-dependent kinases suggests that it may play a role in cell cycle regulation.
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PMID:KAP: a dual specificity phosphatase that interacts with cyclin-dependent kinases. 812 73

The Cdc25 dual specificity phosphatase family has a central role in controlling cell cycle progression and has been implicated in the etiology of cancer. One compound, 4-(benzyl-(2-[(2, 5-diphenyl-oxazole-4-carbonyl)-amino]-ethyl)-carbamoyl)-2-decanoylami no butyric acid (SC-alpha alpha delta 9), was previously identified as the most potent reported synthetic inhibitor of Cdc25 phosphatases in vitro. In the present study, we demonstrate that SC-alpha alpha delta 9 inhibited Cdc25-dependent cell cycle progression at both G1 and G2/M phase using tsFT210 cells, which express a temperature-sensitive Cdc2 mutant. SC-alpha alpha delta 9 blocked both G2/M transition and dephosphorylation of Cdc2 in a concentration-dependent manner. SC-alpha alpha delta 9 also enhanced tyrosine phosphorylation of both Cdk2 and Cdk4, and decreased Cdk4 kinase activity. Both of the kinases are potent regulators of G1 transition. Furthermore, closely related chemical analogs that lacked Cdc25 inhibitory activity failed to block cell cycle progression at both G1 and G2/M, and did not affect Cdc2 phosphorylation or Cdk4 kinase activity. SC-alpha alpha delta 9 did not alter p53, p21 or p16 levels. Our results support the hypothesis that the disruption in cell cycle transition caused by SC-alpha alpha delta 9 was due to intracellular Cdc25 inhibition. We propose that the SC-alpha alpha delta 9 pharmacophore could be useful in further clarifying the role of Cdc25 phosphatase-dependent pathways in checkpoint control, oncogenesis, and apoptosis.
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PMID:Dual G1 and G2/M phase inhibition by SC-alpha alpha delta 9, a combinatorially derived Cdc25 phosphatase inhibitor. 1059 98

Many cancer therapies cause DNA damage to effectively kill proliferating tumor cells; however, a major limitation of current therapies is the emergence of resistant tumors following initial treatment. Cell cycle checkpoints are involved in the response to DNA damage and specifically prevent cell cycle progression to allow DNA repair. Tumor cells can take advantage of the G2 checkpoint to arrest following DNA damage and avoid immediate cell death. This can contribute to acquisition of drug resistance. By abrogating the G2 checkpoint arrest, it may be possible to synergistically augment tumor cell death induced by DNA damage and circumvent resistance. This requires an understanding of the molecules involved in regulating the checkpoints. Human Chk1 is a recently identified homologue of the Schizosaccharomyces pombe checkpoint kinase gene, which is required for G2 arrest in response to DNA damage. Chk1 phosphorylates the dual specificity phosphatase cdc25C on Ser-216, and this may be involved in preventing cdc25 from activating cdc2/cyclinB and initiating mitosis. To further study the role of Chk1 in G2 checkpoint control, we identified a potent and selective indolocarbazole inhibitor (SB-218078) of Chk1 kinase activity and used this compound to assess cell cycle checkpoint responses. Limited DNA damage induced by gamma-irradiation or the topoisomerase I inhibitor topotecan was used to induce G2 arrest in HeLa cells. In the presence of the Chk1 inhibitor, the cells did not arrest following gamma-irradiation or treatment with topotecan, but continued into mitosis. Abrogation of the damage-arrest checkpoint also enhanced the cytotoxicity of topoisomerase I inhibitors. These studies suggest that Chk1 activity is required for G2 arrest following DNA damage.
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PMID:An indolocarbazole inhibitor of human checkpoint kinase (Chk1) abrogates cell cycle arrest caused by DNA damage. 1067 38

Arsenic acts as a toxicant, a carcinogen, and an effective chemotherapeutic agent, but its mechanisms of action are unclear. We have previously shown that treatment of U937 cells with 5 microM sodium arsenite inhibits cell cycle progression through each cell cycle phase, including S phase. Cdc25A dual specificity phosphatase controls entry into and progression through S phase by dephosphorylating sites of inhibitory phosphorylation on cyclin E-cdk2 (Thr14 and Tyr15). Immunoblotting reveals that a 3-h treatment of U937 cells with 5 microM sodium arsenite results in a dramatic decrease in cdc25A protein levels. Coimmunoprecipitation experiments confirm that cyclin E-cdk2 is more phosphorylated at Thr14 and Tyr15 in the presence of arsenite, and kinase activity assays reveal a decrease in cyclin E-associated cdk2 activity. Therefore, arsenite-dependent cdc25A depletion could contribute to S phase inhibition. There exists an S phase checkpoint known to be mediated by proteasomal cdc25A degradation. However, cycloheximide half-life assay reveals that cdc25A is actually stabilized in arsenite-treated cells. Real-time RT-PCR shows that cdc25A mRNA levels are substantially decreased with arsenite treatment, and actinomycin D half-life assay reveals no change in message stability. Decreased cdc25A message translation is shown by sucrose density gradient polysomal analysis to be an unlikely cause for the profound arsenite-dependent reduction in cdc25A protein levels. Studies are ongoing to establish the mechanism by which 5 microM arsenite decreases cdc25A message abundance, but we surmise that, given the lack of effect on mRNA stability, an inhibition of gene transcription is likely involved.
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PMID:Arsenite slows S phase progression via inhibition of cdc25A dual specificity phosphatase gene transcription. 1754 10

The dual specificity phosphatase Cdc25B is capable of inhibiting cellular proliferation, and this occurs in a manner dependent upon its catalytic activity. Here it is shown that this is accompanied by inappropriate cyclin-dependent kinase activation and premature mitotic entry, leading to both p53-dependent and independent checkpoints. Forced expression of Cdc25B inappropriately up-regulated the activity of Cdk1 and Cdk2, by reducing levels of inhibitory phosphorylation. In cells lacking p14ARF, p53 is induced, and components of the ATM and ATR pathways are activated. Cdc25B triggers cell cycle arrest in the G(1) and G(2) phases that is p53- and p21-dependent and is inhibited by caffeine. Cdc25B also causes cells with an S phase DNA content to enter mitosis prematurely in a p53-independent manner. Synchronization of cells with aphidicolin results in these cells undergoing apoptosis. Thus, inappropriate cell cycle progression and premature mitotic entry via dysregulation of cyclin-dependent kinases results in activation of both p53-dependent and independent responses. Because Cdc25B is known to have oncogenic activity, this provides insight into the multistep nature of cancer development and why there is p53 loss during tumorigenesis.
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PMID:Inappropriate activation of cyclin-dependent kinases by the phosphatase Cdc25b results in premature mitotic entry and triggers a p53-dependent checkpoint. 1913 58

The activity of the dual specificity phosphatase cdc25C is required for mitotic progression though the mechanisms by which cdc25C is activated prior to mitosis in human cells remain unclear. The data presented herein show that the actin binding protein Filamin A forms a complex with cdc25C in vivo and binds preferentially to the mitotic form of cdc25C. Co-expression of Filamin A with cdc25C results in an increase in PCC induced by cdc25C, while knocking down Filamin A expression reduces the levels of PCC induced by cdc25C overexpression. Further, only a Filamin A fragment that forms a complex with both cdc25C and cyclin B1 and retains the dimerization domain can stimulate the ability of cdc25C to induce PCC. These results suggest that Filamin A provides a platform for the assembly of the cyclin B1-cdk1- cdc25C complex resulting in cdk1 activation and mitotic progression.
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PMID:Filamin A stimulates cdc25C function and promotes entry into mitosis. 2132 83

We describe a reliable and efficient method for the purification of catalytically active and mutant inactive full-length forms of the human dual specificity phosphatase cdc25C from bacteria. The protocol involves isolating insoluble cdc25C protein in inclusion bodies, solubilization in guanidine HCL, and renaturation through rapid dilution into low salt buffer. After binding renatured proteins to an ion exchange resin, cdc25C elutes in two peaks at 350 and 450 mM NaCl. Analysis by gel exclusion chromatography and enzymatic assays reveals the highest phosphatase activity is associated with the 350 mM NaCl with little or no activity present in the 450 mM peak. Furthermore, active cdc25C has a native molecular mass of 220 kDa consistent with a potential tetrameric complex of the 55-kDa cdc25C protein. Assaying phosphatase activity against artificial substrates pNPP and 3-OMFP reveals a 220 kDa form of the phosphatase is active in a non-phosphorylated state. The protein effectively activates cdk1/cyclin B prokinase complexes in vitro in the absence of cdk1 kinase activity in an orthovanadate sensitive manner but is inactivated by A-kinase phosphorylation. In vitro phosphorylation of purified cdc25C by cdk1/cyclin B1, cdk2/cyclin A2 and cdk2/cyclin E shows that distinct TP/SP mitotic phosphorylation sites on cdc25C are differentially phosphorylated by these 3 cdk/cyclin complexes associated with different levels of cdc25C activation. Finally, we show that endogenous native cdc25C from human cells is present in high molecular weight complexes with other proteins and resolves mostly above 200-kDa. These data show that untagged cdc25C can be purified with a simple protocol as an active dual specificity phosphatase with a native molecular mass consistent with a homo-tetrameric configuration.
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PMID:Purification and biochemical analysis of catalytically active human cdc25C dual specificity phosphatase. 2356 37

Cdc25C is a cell cycle protein of the dual specificity phosphatase family essential for activating the cdk1/Cyclin B1 complex in cells entering into mitosis. Since altered cell cycle is a hallmark of human cancers, we investigated androgen regulation of Cdc25C protein in human prostate cancer (PCa) cells, including androgen-sensitive (AS) LNCaP C-33 cells and androgen-independent (AI) LNCaP C-81 as well as PC-3 cells. In the regular culture condition containing fetal bovine serum (FBS), Cdc25C protein levels were similar in these PCa cells. In a steroid-reduced condition, Cdc25C protein was greatly decreased in AS C-33 cells but not AI C-81 or PC-3 cells. In androgen-treated C-33 cells, the Cdc25C protein level was greatly elevated, following a dose- and a time-dependent manner, correlating with increased cell proliferation. This androgen effect was blocked by Casodex, an androgen receptor blocker. Nevertheless, epidermal growth factor (EGF), a growth stimulator of PCa cells, could only increase Cdc25C protein level by about 1.5-fold. Altered expression of Cdc25C in C-33 cells and PC-3 cells by cDNA and/or shRNA transfection is associated with the corresponding changes of cell growth and Cyclin B1 protein level. Actinomycin D and cycloheximide could only partially block androgen-induced Cdc25C protein level. Treatments with both proteasomal and lysosomal inhibitors resulted in elevated Cdc25C protein levels. Immunoprecipitation revealed that androgens reduced the ubiquitination of Cdc25C proteins. These results show for the first time that Cdc25C protein plays a role in regulating PCa cell growth, and androgen treatments, but not EGF, greatly increase Cdc25C protein levels in AS PCa cells, which is in part by decreasing its degradation. These results can lead to advanced PCa therapy via up-regulating the degradation pathways of Cdc25C protein.
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PMID:Androgens upregulate Cdc25C protein by inhibiting its proteasomal and lysosomal degradation pathways. 2363 32