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)

We evaluated the effect of beta1-integrin receptor engagement on the expression and activity of cell cycle regulatory proteins in CD34(+) cells under conditions that mimic the steady-state marrow microenvironment and in the presence of supraphysiological concentrations of interleukin-3 (IL3) and stem cell factor (SCF). Adhesion of CD34(+) progenitors to fibronectin (FN) was similar whether IL3 or SCF was present or absent. Engagement of beta1-integrins blocked S-phase entry of CD34(+) cells in the absence of IL3 or SCF, whereas addition of 10 ng/mL IL3 or SCF prevented such a block in S-phase entry. In the absence of IL3 or SCF, cyclin-E levels were significantly lower and p27(KIP1) levels significantly higher in FN-adherent than in FN-nonadherent cells, or than in poly-L-lysine (PLL)-adherent or (PLL)-nonadherent cells. Cyclin-dependent-kinase (cdk)-2 activity was decreased and levels of cyclin-E-cdk2 complexes were lower in FN-adherent than in PLL-adherent cells. In contrast, cyclin-E and p27(KIP1) protein levels and cdk2 activity in cells adherent to FN in the presence of IL3 or SCF were similar to those in PLL-adherent and FN-nonadherent or PLL-nonadherent cells. In conclusion, under physiological cytokine conditions, integrin engagement prevents S-phase entrance of CD34(+) cells, which is associated with elevated levels of the contact-dependent cyclin kinase inhibitor p27(KIP1). Supraphysiological concentrations of IL3 or SCF prevent p27(KIP1) elevation and override the integrin-mediated inhibition of entry into S phase.
 ...
PMID:Opposing effects of engagement of integrins and stimulation of cytokine receptors on cell cycle progression of normal human hematopoietic progenitors. 1064 95

beta(1)-integrin engagement on normal (NL) CD34(+) cells increases levels of the cyclin-dependent kinase inhibitor (cdki), p27(Kip), decreases cdk2 activity, and inhibits G(1)/S-phase progression. In contrast, beta(1)-integrin engagement on chronic myelogenous leukemia (CML) CD34(+) cells does not inhibit G(1)/S progression. We now show that, in CML, baseline p27(Kip) levels are significantly higher than in NL CD34(+) cells, but adhesion to fibronectin (FN) does not increase p27(Kip) levels. p27(Kip) mRNA levels are similar in CML and NL CD34(+) cells and remain unchanged after adhesion, suggesting posttranscriptional regulation. Despite the elevated p27(Kip) levels, cdk2 kinase activity is similar in CML and NL CD34(+) cells. In NL CD34(+) cells, >90% of p27(Kip) is located in the nucleus, where it binds to cdk2 after integrin engagement. In CML CD34(+) cells, however, >80% of p27(Kip) is located in the cytoplasm even in FN-adherent cells, and significantly less p27(Kip) is bound to cdk2. Thus, presence of BCR/ABL induces elevated levels of p27(Kip) and relocation of p27(Kip) to the cytoplasm, which contributes to the loss of integrin-mediated proliferation inhibition, characteristic of CML.
 ...
PMID:Abnormal integrin-mediated regulation of chronic myelogenous leukemia CD34+ cell proliferation: BCR/ABL up-regulates the cyclin-dependent kinase inhibitor, p27Kip, which is relocated to the cell cytoplasm and incapable of regulating cdk2 activity. 1097 91

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.
 ...
PMID:Lineage-specific regulation of cell cycle control gene expression during haematopoietic cell differentiation. 1099 79

In an attempt to gain more insight into the events of leukaemic transformation, a cell line overexpressing MHC class II (DR) was generated by transfecting an early CD34-negative haematopoietic progenitor stem cell line with the appropriate constructs. The stable transfection with genes for DR antigens leads to cellular transformation. The DR(+) transformed cell clones express a tyrosine-phosphorylated DR heterodimer and show a significantly different morphology. DR(+) clones present the morphology of an immature myeloid neoplasia expressing alpha-naphthyl-acetate-esterase (ANAE), but neither myeloperoxidase nor CD34. While D064 cells predominately grow adherent as fibroblast-like cells, the DR(+) clones display a decrease in adherent growth. Although both cell lines express similar amounts of the interleukin-6 (IL-6) signal transducer gp130, the DR-transfected cells still show activation of STAT factors by IL-6, whereas D064 cells do not. Although the transformed clones present acceleration of cell-cycle transition and growth, the G(0)/G(1) progression inhibitor p27(kip-1) is up-regulated, while the expression of proteins involved in the S/G(2) phase transition, such as cyclin B and cdc2 (p34), is suppressed. Instead cyclin D3, one of the G(0)/G(1) progression factors, is up-regulated, as well as tyrosine-phosphorylated p62(dok), suggesting dysregulation of cell cycle-controlling proteins. In addition, DR(+) leukaemia-like cells also overexpress Bcl-2, while bax expression is suppressed, compared with the wild-type (wt) parental haematopoietic stem cell line.
 ...
PMID:In vitro-generated stem cell leukaemia showing altered cell cycle progression with distinct signalling of the tyrosine-phosphorylated rasGAP-associated p62(dok) protein. 1105 20

To maintain the fidelity and integrity of blood formation, the cell cycle is under strict regulation during hematopoietic cell differentiation. This review summarizes recent studies, including our own, on the expression of cell cycle control genes in hematopoietic stem cells and its changes during differentiation. In our study, mRNA expression of cyclin-dependent kinases (cdks) and cyclins, except cdk4, was found to be generally suppressed in CD34+ cells isolated from the bone marrow of healthy volunteers. Among four major cdk inhibitors, p16 was expressed higher in CD34+ cells than in CD34 bone marrow mononuclear cells, whereas the amounts of p21 and p27 transcripts increased in the CD34 population. The behavior of cell cycle control genes during hematopoietic differentiation was classified into four patterns: (i) universal up-regulation (cdc2, cdk2, cyclin A, cyclin B, p21); (ii) up-regulation in specific lineages (cyclin D1, cyclin D3, and p5); (iii) no induction or stable expression (cdk4, cyclin D2, cyclin E, and p27); and (iv) universal down-regulation (p16). Lineage-specific changes include a sustained elevation of cdc2 and cyclin A during erythroid differentiation, cyclin D1 and p15 induction in myeloid lineage cells, and selective up-regulation of cyclin D3 during megakaryocyte development. 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. Additional data from other laboratories are summarized and their significance is discussed in comparison with our findings.
 ...
PMID:Cell cycle control genes and hematopoietic cell differentiation. 1199 51

Forty-four samples from 25 cases of retroperitoneal sarcoma initially diagnosed as malignant fibrous histiocytoma were histologically reviewed. Immunohistochemistry for mdm2 and cdk4 was performed on 20 cases. Comparative genomic hybridization was performed on 18 samples from 13 patients. Seventeen cases were reclassified as dedifferentiated liposarcoma. Twenty-one of 32 samples from these patients showed areas of well-differentiated liposarcoma, allowing the diagnosis of dedifferentiated liposarcoma. Immunohistochemistry performed in 15 of these cases showed positivity for mdm2 and cdk4. Comparative genomic hybridization analysis performed on 15 samples from 11 of these patients showed an amplification of the 12q13-15 region. Eight cases were reclassified as poorly differentiated sarcoma. Twelve samples from these patients showed no area of well-differentiated liposarcoma. Immunohistochemistry showed positivity for mdm2 and cdk4 in one of six of these patients and showed positivity for CD34 in another one. Comparative genomic hybridization analysis performed on three samples from two of these patients showed no amplification of the 12q13-15 region but showed complex profiles. This study shows that most so-called malignant fibrous histiocytomas developed in the retroperitoneum are dedifferentiated liposarcoma and that a poorly differentiated sarcoma in this area should prompt extensive sampling to demonstrate a well-differentiated liposarcoma component, immunohistochemistry for mdm2 and cdk4, and if possible, a cytogenetic or a molecular biology analysis.
 ...
PMID:Most malignant fibrous histiocytomas developed in the retroperitoneum are dedifferentiated liposarcomas: a review of 25 cases initially diagnosed as malignant fibrous histiocytoma. 1264 Jan 6

Satellite cells are quiescent muscle stem cells that promote postnatal muscle growth and repair. Here we show that myostatin, a TGF-beta member, signals satellite cell quiescence and also negatively regulates satellite cell self-renewal. BrdU labeling in vivo revealed that, among the Myostatin-deficient satellite cells, higher numbers of satellite cells are activated as compared with wild type. In contrast, addition of Myostatin to myofiber explant cultures inhibits satellite cell activation. Cell cycle analysis confirms that Myostatin up-regulated p21, a Cdk inhibitor, and decreased the levels and activity of Cdk2 protein in satellite cells. Hence, Myostatin negatively regulates the G1 to S progression and thus maintains the quiescent status of satellite cells. Immunohistochemical analysis with CD34 antibodies indicates that there is an increased number of satellite cells per unit length of freshly isolated Mstn-/- muscle fibers. Determination of proliferation rate suggests that this elevation in satellite cell number could be due to increased self-renewal and delayed expression of the differentiation gene (myogenin) in Mstn-/- adult myoblasts. Taken together, these results suggest that Myostatin is a potent negative regulator of satellite cell activation and thus signals the quiescence of satellite cells.
 ...
PMID:Myostatin negatively regulates satellite cell activation and self-renewal. 1296 5

We have previously shown that engagement of the integrins VLA-4 and VLA-5 to the fibronectin fragment CH-296 in combination with cytokines sustained the capacity of cultured human CD34(+) cells to undergo hematopoiesis in immunodeficient mice for 7 to 12 months, whereas this capacity was rapidly lost in cells cultured in suspension with the same cytokines. In the current study, we assessed the molecular pathways that might explain the loss of long-term engraftment capacity in cells cultured in suspension. Although the cell cycle profile was similar between cells cultured in suspension versus on fibronectin, levels of cell death were higher in the suspended cultures. While the CDK inhibitors p27Kip1 and p57Kip2 were present at equal levels in cells from both cultures, low levels of p21Cip1 were detectable only in the cytoplasmic compartment of cells cultured in suspension. Cytoplasmic location of p21Cip1 has been linked to monocytic differentiation. The levels of c-myb and GATA-2, transcription factors associated with stem cell maintenance, were higher in cells cultured on fibronectin as compared with suspension. In contrast, the levels of PU.1, which is induced during myeloid differentiation, were higher in cells cultured in suspension. There were no significant differences in surface expression of CD34 on the cells after culture, but total CD34 protein, assessed by immunoblotting, was significantly higher in cells cultured on fibronectin. Our data suggest that, in the presence of cytokines, the engagement of VLA-4 and VLA-5 integrins to the fibronectin fragment CH-296 preserves the expression of specific transcription factors associated with primitive stem cell maintenance. In contrast, a lack of integrin engagement leads to the induction of cellular markers associated with myeloid differentiation.
 ...
PMID:Cytokine and integrin stimulation synergize to promote higher levels of GATA-2, c-myb, and CD34 protein in primary human hematopoietic progenitors from bone marrow. 1709 23

Hematopoietic stem cells (HSCs) can remain quiescent or they can enter the cell cycle, and either self-renew or differentiate. Although cyclin C and cyclin dependent kinase (cdk3) are essential for the transition from the G(0) to the G(1) phase of the cell cycle in human fibroblasts, the role of cyclin C in hematopoietic stem/progenitor cells (HSPCs) is not clear. We have identified an important role of cyclin C (CCNC) in regulating human HSPC quiescence, as knocking down CCNC expression in human cord blood CD34(+) cells resulted in a significant increase in quiescent cells that maintain CD34 expression. CCNC knockdown also promotes in vitro HSPC expansion and enhances their engraftment potential in sublethally irradiated immunodeficient mice. Our studies establish cyclin C as a critical regulator of the G(0)/G(1) transition of human HSPCs and suggest that modulating cyclin C levels may be useful for HSC expansion and more efficient engraftment.
 ...
PMID:Cyclin C regulates human hematopoietic stem/progenitor cell quiescence. 1996 89

The goal of the present study was to investigate the specific way in which recombinant stimulatory cytokines modulate the cell cycle dynamics of primitive hematopoietic cells in vitro. A human cord blood-derived cell population, enriched for CD34(+) Lin(-) cells, was obtained by negative selection and cultured in liquid cultures, in the absence or presence of recombinant stimulatory cytokines. The proportion of cells in each phase of the cell cycle, as well as the expression of cyclin D3, cyclin-dependent kinase-4 (cdk4), p16, p21 and p27, was determined at different time points. At the onset of culture, the vast majority of the cells were in the G(0)/G(1) phase of the cell cycle. In the absence of cytokines, most cells remained in such a phase and no cell cycle activity was detected throughout the culture period, which correlated with the absence of population doublings. In the presence of cytokines, approximately four cell cycles, with a proportionate population doubling, were observed within the first 4 days of culture. In cultures incorporating cytokines, expression levels of cyclin D3 and cdk4 were higher than in their absence; in contrast, the levels of the cell cycle inhibitors p16 and p21 were higher in cultures without cytokines. Levels of p27 were also higher in the presence of cytokines. Our results indicate that the proliferation of primitive hematopoietic cells in liquid culture is promoted by recombinant cytokines via the induction of specific positive regulators of the cell cycle and down-regulation of particular cell cycle inhibitors.
 ...
PMID:In vitro cell cycle dynamics of primitive hematopoietic cells from human umbilical cord blood. 2013 57


1 2 Next >>