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)

Activation of the cyclin dependent kinases (CDK4/CDK6 and CDK2) is required for G1 phase progression and entry into S-phase. The activation of these kinases is regulated by checkpoints that monitor environmental and intracellular conditions. Progression into S-phase is controlled, in part, by the availability of growth factors, and we have investigated the relationship between growth factor availability and the activation of the CDK kinases. Blocking activation of epidermal growth factor (EGF) receptor tyrosine kinase with anti-EGF receptor monoclonal antibody (mAb) 225 induces G1 phase cell cycle arrest in DiFi human colon adenocarcinoma cells. When DiFi cells are treated with mAb 225 for 24 h, we observe marked decreases in the activities of CDK2 kinase and cyclin E-associated CDK kinase which are not accompanied by reduced levels of cyclin E and CDK2 proteins. However, the amount of cyclin/CDK kinase inhibitor p27KIP1 increases in the mAb-treated cells and p27KIP1 is bound to CDK2 in increasing amounts. Immunodepletion of p27KIP1 removes an inhibitory activity from lysates of mAb-treated cells: the immunodepleted and heated lysates lose the capacity to inhibit cyclin E/CDK2 activity in an in vitro assay. The results suggest that G1 arrest in the cell cycle induced by EGF receptor blockade involves p27KIP1.
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PMID:Involvement of p27KIP1 in G1 arrest mediated by an anti-epidermal growth factor receptor monoclonal antibody. 862 55

Organization of intermediate filament, a major component of cytoskeleton, is regulated by protein phosphorylation/dephosphorylation, which is a dynamic process governed by a balance between the activities of involved protein kinases and phosphatases. Blocking dephosphorylation by protein phosphatase inhibitors such as okadaic acid (OA) leads to an apparent activation of protein kinase(s) and to genuine activation of phosphatase-regulated protein kinase(s). Treatment of 9L rat brain tumor cells with OA results in a drastically increased phosphorylation of vimentin, an intermediate filament protein. In-gel renaturing assays and in vitro kinase assays using vimentin as the exogenous substrate indicate that certain protein kinase(s) is activated in OA-treated cells. With specific protein kinase inhibitors, we show the possible involvement of the cdc2 kinase- and p38 mitogen-activated protein kinase (p38MAPK)-mediated pathways in this process. Subsequent in vitro assays demonstrate that vimentin may serve as an excellent substrate for MAPK-activated protein kinase-2 (MAPKAPK-2), the downstream effector of p38MAPK, and that MAPKAPK-2 is activated with OA treatment. Comparative analysis of tryptic phosphopeptide maps also indicates that corresponding phosphopeptides emerged in vimentin from OA-treated cells and were phosphorylated by MAPKAPK-2. Taken together, the results clearly demonstrate that MAPKAPK-2 may function as a vimentin kinase in vitro and in vivo. These findings shed new light on the possible involvement of the p38MAPK signaling cascade, via MAPKAPK-2, in the maintenance of integrity and possible physiological regulation of intermediate filaments.
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PMID:Identification of mitogen-activated protein kinase-activated protein kinase-2 as a vimentin kinase activated by okadaic acid in 9L rat brain tumor cells. 977 16

Accumulating evidence suggests that phosphatases play an important role in regulating a variety of signal transduction pathways that have a bearing on cancer. The kinase-associated phosphatase (KAP) is a human dual-specificity protein phosphatase that was identified as a Cdc2- or Cdk2-interacting protein by a yeast two-hybrid screening, yet the biological significance of these interactions remains elusive. We have identified the KAP gene as an overexpressed gene in breast and prostate cancer by using a phosphatase domain-specific differential-display PCR strategy. Here we report that breast and prostate malignancies are associated with high levels of KAP expression. The sublocalization of KAP is variable. In normal cells, KAP is primarily found in the perinuclear region, but in tumor cells, a significant portion of KAP is found in the cytoplasm. Blocking KAP expression by antisense KAP in a tetracycline-regulatable system results in a reduced population of S-phase cells and reduced Cdk2 kinase activity. Furthermore, lowering KAP expression led to inhibition of the transformed phenotype, with reduced anchorage-independent growth and tumorigenic potential in athymic nude mice. These findings suggest that therapeutic intervention might be aimed at repression of KAP gene overexpression in human breast and prostate cancer.
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PMID:Overexpression of kinase-associated phosphatase (KAP) in breast and prostate cancer and inhibition of the transformed phenotype by antisense KAP expression. 3251 51

Squamous differentiation of keratinocytes is associated with decreases in E2F-1 mRNA expression and E2F activity, and these processes are disrupted in squamous cell carcinoma cell lines. We now show that E2F-1 mRNA expression is increased in primary squamous cell carcinomas of the skin relative to normal epidermis. To explore the relationship between E2F-1 and squamous differentiation further, we examined the effect of altering E2F activity in primary human keratinocytes induced to differentiate. Promoter activity for the proliferation-associated genes, cdc2 and keratin 14, are inhibited during squamous differentiation. This inhibition can be inhibited by overexpression of E2F-1 in keratinocytes. Overexpression of E2F-1 also suppressed the expression of differentiation markers (transglutaminase type 1 and keratin 10) in differentiated keratinocytes. Blocking E2F activity by transfecting proliferating keratinocytes with dominant negative E2F-1 constructs inhibited the expression of cdc2 and E2F-1, but did not induce differentiation. Furthermore, expression of the dominant negative construct in epithelial carcinoma cell lines and normal keratinocytes decreased expression from the cdc2 promoter. These data indicate that E2F-1 promotes keratinocyte proliferation-specific marker genes and suppresses squamous differentiation-specific marker genes. Moreover, these data indicate that targeted disruption of E2F-1 activity may have therapeutic potential for the treatment of squamous carcinomas. Oncogene (2000).
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PMID:E2F-1 induces proliferation-specific genes and suppresses squamous differentiation-specific genes in human epidermal keratinocytes. 1087 39

To maintain the fidelity and integrity of blood formation, the cell cycle is under strict regulation during haematopoietic cell differentiation. To elucidate the molecular mechanisms of cell cycle regulation during haematopoiesis, we examined cell cycle control gene expression during lineage-specific differentiation from CD34+ progenitor cells. Expression of cyclin-dependent kinases (cdks) and cyclins, except cdk4, was generally suppressed in CD34+ cells freshly isolated from the bone marrow of healthy volunteers. Among four major cdk inhibitors, p16 was expressed more highly in CD34+ cells than in CD34-negative bone marrow mononuclear cells, whereas the amounts of p21 and p27 transcripts increased in the CD34- population. The behaviour of cell cycle control genes during haematopoietic differentiation was classified into four patterns: (i) universal upregulation (cdc2, cdk2, cyclin A, cyclin B and p21); (ii) upregulation in specific lineages (cyclin D1, cyclin D3 and p15); (iii) no induction or stable expression (cdk4, cyclin D2, cyclin E and p27); and (iv) universal downregulation (p16). Lineage-specific changes included the sustained elevation of cdc2 and cyclin A during erythroid differentiation, cyclin D1 and p15 induction in myeloid lineage and selective upregulation of cyclin D3 in megakaryocytes. Blocking induction of cyclin D3 resulted in the inhibition of megakaryocytic differentiation. These results suggest that the expression of cell cycle control genes is distinctively regulated in a lineage-dependent manner, reflecting the cell cycle characteristics of each lineage. Some of these genes play an essential role in the process of differentiation itself.
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PMID:Lineage-specific regulation of cell cycle control gene expression during haematopoietic cell differentiation. 1099 79

The high frequency of mutations in cancer cells which result in altered cell cycle regulation and growth signal transduction, conferring a proliferative advantage, indicates that many of these aberrant mechanisms may be strategic targets for cancer therapy. The macrolide fungicide rapamycin, a natural product with potent antimicrobial, immunosuppressant, and anti-tumor properties, inhibits the translation of key mRNAs of proteins required for cell cycle progression from G1 to S phase. Rapamycin binds intracellularly to the immunophilin FK506 binding protein 12 (FKBP12), and the resultant complex inhibits the protein kinase activity of a protein kinase termed mammalian target of rapamycin (mTOR). The inhibition of mTOR, in turn, blocks signals to two separate downstream pathways which control the translation of specific mRNAs required for cell cycle traverse from G1 to S phase. Blocking mTOR affects the activity of the 40S ribosomal protein S6 kinase (p70s6k) and the function of the eukaryotic initiation factor 4E-binding protein-1 (4E-BP1), leading to growth arrest in the the G1 phase of the cell cycle. In addition to its actions on p70s6k and 4E-BP1, rapamycin prevents cyclin-dependent kinase activation, inhibits retinoblastoma protein (pRb) phosphorylation, and accelerates the turnover of cyclin D1 that leads to a deficiency of active cdk4/cyclin D1 complexes, all of which can inhibit cell cycle traverse at the G1/S phase transition. Both rapamycin and CCI-779, an ester analog of rapamycin with improved pharmaceutical properties and aqueous solubility, have demonstrated impressive activity against a broad range of human cancers growing in tissue culture and in human tumor xenograft models, which has supported the development of compounds targeting rapamycin-sensitive signal-transduction pathways. CCI-779 has completed several phase I clinical evaluations and is currently undergoing broad disease-directed efficacy studies. The agent appears to be well tolerated at doses that have resulted in impressive anti-tumor activity in several types of refractory neoplasms. Important challenges during clinical development include the definition of a recommended dose range associated with optimal biological activity and maximal therapeutic indices, as well as the ability to predict which tumors will be sensitive or resistant to CCI-779.
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PMID:The rapamycin-sensitive signal transduction pathway as a target for cancer therapy. 1142 55

Mitosis requires cyclin-dependent kinase (cdk) 1-cyclin B activity [1]. Exit from mitosis depends on the inactivation of the complex by the degradation of cyclin B [2]. Cdk2 is also active during mitosis [3, 4]. In Xenopus egg extracts, cdk2 is primarily in complex with cyclin E, which is stable [5]. At the end of mitosis, downregulation of cdk2-cyclin E activity is accompanied by inhibitory phosphorylation of cdk2 [6]. Here, we show that cdk2-cyclin E activity maintains cdk1-cyclin B during mitosis. At mitosis exit, cdk2 is inactivated prior to cdk1. The loss of cdk2 activity follows and depends upon an increase in protein kinase A (PKA) activity. Prematurely inactivating cdk2 advances the time of cyclin B degradation and cdk1 inactivation. Blocking PKA, instead, stabilizes cdk2 activity and inhibits cyclin B degradation and cdk1 inactivation. The stabilization of cdk1-cyclin B is also induced by a mutant cdk2-cyclin E complex that is resistant to inhibitory phosphorylation. P21-Cip1, which inhibits both wild-type and mutant cdk2-cyclin E, reverses mitotic arrest under either condition. Our findings indicate that the proteolysis-independent downregulation of cdk2 activity at the end of mitosis depends on PKA and is required to activate the proteolysis cascade that leads to mitosis exit.
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PMID:Role for cyclin-dependent kinase 2 in mitosis exit. 1151 56

The tumour suppressor protein p21(WAF1) plays a central role in regulating eukaryotic cell-cycle progression. Through its association with G1- and S-phase CDK complexes it regulates activation of the retinoblastoma protein (pRb) and E2F transcription factors. Recognition of CDK/cyclin complexes by p21 occurs, at least in part, through a protein-protein interaction with a binding groove on the cyclin subunit. The same groove has been shown to be involved in the recruitment of macromolecular CDK substrates, including pRb and E2F. Blocking of this recruitment site therefore prevents recognition and subsequent phosphorylation of CDK substrates and offers a therapeutic approach towards restoration of p21-like tumour suppression. Starting from the C-terminal cyclin-binding domain of p21 we have identified the minimal and optimized bioactive (152)HAKRRLIF(159) peptide sequence with respect to CDK protein kinase inhibition where pRb is the substrate. The phosphorylation of histone H1, however, which does not contain a recognizable cyclin-binding motif, was unaffected. Detailed structure-activity relationship investigations revealed that the determinants within this sequence are residues Arg(155), Leu(157) and Phe(159) and more completely define the composition of the cyclin-binding motif. A marked increase in potency was obtained upon replacement of the native Ser(153) with an Ala residue in the context of short synthetic peptide inhibitors and significantly, this mutation resulted in comparable affinity with CDK2/cyclin A as does the full-length recombinant p21 (which has CDK2 and cyclin A binding sites). Peptides derived from various proteins known to interact with cyclins were compared for potency and selectivity. A molecular model of the complex between the cyclin groove and the HAKRRLIF peptide was constructed. This model accounts for the observed peptide structure-activity relationships, including the potency enhancement of the LIF sequence occupying the hydrophobic pocket. Furthermore, it provides generic insights into molecular interactions governing cyclin groove recognition and lays the foundation for the development of peptidomimetic inhibitors of CDKs.
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PMID:Highly potent p21(WAF1)-derived peptide inhibitors of CDK-mediated pRb phosphorylation: delineation and structural insight into their interactions with cyclin A. 1238 16

Hyaluronidases degrade hyaluronic acid, which promotes metastasis. HYAL1 type hyaluronidase is an independent prognostic indicator of prostate cancer progression and a biomarker for bladder cancer. However, it is controversial whether hyaluronidase (e.g., HYAL1) functions as a tumor promoter or as a suppressor. We stably transfected prostate cancer cells, DU145 and PC-3 ML, with HYAL1-sense (HYAL1-S), HYAL1-antisense (HYAL1-AS), or vector DNA. HYAL1-AS transfectants were not generated for PC-3 ML because it expresses little HYAL1. HYAL1-S transfectants produced < or = 42 milliunits (moderate overproducers) or > or = 80 milliunits hyaluronidase activity (high producers). HYAL1-AS transfectants produced <10% hyaluronidase activity when compared with vector transfectants (18-24 milliunits). Both blocking HYAL1 expression and high HYAL1 production resulted in a 4- to 5-fold decrease in prostate cancer cell proliferation. HYAL1-AS transfectants had a G2-M block due to decreased cyclin B1, cdc25c, and cdc2/p34 expression and cdc2/p34 kinase activity. High HYAL1 producers had a 3-fold increase in apoptotic activity and mitochondrial depolarization when compared with vector transfectants and expressed activated proapoptotic protein WOX1. Blocking HYAL1 expression inhibited tumor growth by 4- to 7-fold, whereas high HYAL1 producing transfectants either did not form tumors (DU145) or grew 3.5-fold slower (PC-3 ML). Whereas vector and moderate HYAL1 producers generated muscle and blood vessel infiltrating tumors, HYAL1-AS tumors were benign and contained smaller capillaries. Specimens of high HYAL1 producers were 99% free of tumor cells. This study shows that, depending on the concentration, HYAL1 functions as a tumor promoter and as a suppressor and provides a basis for anti-hyaluronidase and high-hyaluronidase treatments for cancer.
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PMID:HYAL1 hyaluronidase in prostate cancer: a tumor promoter and suppressor. 1614 Sep 46

Entry into mitosis is catalyzed by cdc2 kinase. Previous work identified the cdc2-activating phosphatase cdc25C and the cdc2-inhibitory kinase wee1 as targets of the incomplete replication-induced kinase Chk1. Further work led to the model that checkpoint kinases block mitotic entry by inhibiting cdc25C through phosphorylation on Ser287 and activating wee1 through phosphorylation on Ser549. However, almost all conclusions underlying this idea were drawn from work using recombinant proteins. Here, we report that in the early Xenopus egg cell cycles, phosphorylation of endogenous cdc25C Ser287 is normally high during interphase and shows no obvious increase after checkpoint activation. By contrast, endogenous wee1 Ser549 phosphorylation is low during interphase and increases after activation of either the DNA damage or replication checkpoints; this is accompanied by a slight increase in wee1 kinase activity. Blocking mitotic entry by adding the catalytic subunit of PKA also results in increased wee1 Ser549 phosphorylation and maintenance of cdc25C Ser287 phosphorylation. These results argue that in response to checkpoint activation, endogenous wee1 is indeed a critical responder that functions by repressing the cdc2-cdc25C positive feedback loop. Surprisingly, endogenous wee1 Ser549 phosphorylation is highest during mitosis just after the peak of cdc2 activity. Treatments that block inactivation of cdc2 result in further increases in wee1 Ser549 phosphorylation, suggesting a previously unsuspected role for wee1 in mitosis.
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PMID:Changes in regulatory phosphorylation of Cdc25C Ser287 and Wee1 Ser549 during normal cell cycle progression and checkpoint arrests. 1619 48


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