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)

HIV-1 enters the brain at the early stage of infection and resides primarily in a limited number of macrophages/microglia and astrocytes. Infection of these cells, however, may not explain the massive neuronal pathology which is seen in AIDS-associated dementia, suggesting a role for factors released from HIV-1 infected cells that trigger a cascade of events leading to neurodegeneration. Our results indicate that Tat, the potent regulatory protein of HIV-1 which is secreted by infected cells and can affect neighboring uninfected cells by transcellular means, can influence multiple biological events that lead to neuronal injury. These findings demonstrate that treatment of neuronal cells with Tat affects MAPK/ERK1/2 activity, the downstream central component of the nerve growth factor (NGF) signaling pathway. Furthermore, our data indicate that treatment of cells with Tat severely decreases expression of p35, a neuron-specific activator of cdk5, a cyclin dependent kinase that phosphorylates several neuronal proteins including neurofilament, and plays an important role in neuronal differentiation and survival. In parallel, Tat can bind to the cellular protein, Puralpha, which associates with cdk5. Further, results from Puralpha knockout animals revealed a decrease in p35 activity, pointing to the importance of Puralpha association with cdk5 in the activity of cdk5:p35 complex. These data demonstrate the cooperativity between HIV-1 Tat and the Puralpha in deregulation of the NGF signal transduction pathway in neuronal cells.
 ...
PMID:Tat-induced deregulation of neuronal differentiation and survival by nerve growth factor pathway. 1249 Nov 58

In neuroblastoma (NB), expression of the TrkA receptor is correlated with good prognosis while N-myc amplification is correlated with poor prognosis. Decreased N-myc levels are key to controlling growth and inducing differentiation in NB cells. In this report, we detail mechanisms by which nerve growth factor (NGF) decreases N-myc levels in TrkA-transfected NB cells and its effect on NB cell proliferation. NGF induced a decrease in N-myc mRNA within 1 h of treatment that occurred in the presence of cycloheximide. The stability of N-myc mRNA was not affected by NGF, indicating a transcriptional control of N-myc mRNA by NGF. NGF but not brain-derived neurotrophic factor (BDNF) decreased N-myc levels demonstrating that p75 alone was not involved. The NGF-induced decrease in N-myc expression was blocked by the Trk tyrosine kinase (TK) antagonist K252a indicating that signals transduced by Trk TK downstream targets were involved. Pharmacologic inhibitors implicated the mitogen-activated protein kinase (MAPK) path. This was supported by the finding that expression of a constitutively activated component of the MAPK path, MAPK kinase (MEK), decreased N-myc levels. Alterations in the level of N-myc are known to alter NB cell cycle progression by affecting the levels of E2Fs and p27(kip1). Consistent with these findings, NGF decreased NB cell number and decreased cyclin E-dependent kinase activity via an increase in p27(kip1). Thus, our results indicate that the MAP kinase is selectively involved in the NGF-induced N-myc downregulation through a transcriptional mechanism. Furthermore, NGF affects the time required for 15N TrkA cells to complete a replication cycle by decreasing N-myc, E2Fs, cyclin E kinase activity and increasing p27(kip1) binding to cyclin E kinase.
 ...
PMID:NGF activation of TrkA decreases N-myc expression via MAPK path leading to a decrease in neuroblastoma cell number. 1469 55

S100B is a Ca2+-modulated protein of the EF-hand type expressed in high abundance in a restricted set of cell types including certain neuronal populations. S100B has been suggested to participate in cell cycle progression, and S100B levels are high in tumor cells, compared with normal parental cells. We expressed S100B in the neuronal cell line PC12, which normally does not express the protein, by the Tet-Off technique, and found the following: (i) proliferation was higher in S100B+ PC12 cells than in S100B- PC12 cells; (ii) nerve growth factor (NGF), which decreased the proliferation of S100B- PC12 cells, was less effective in the case of S100B+ PC12 cells; (iii) expression of S100B made PC12 cells resistant to the differentiating effect of NGF; and (iv) interruption of S100B expression did not result in an immediate restoration of PC12 cell sensitivity to the differentiating effect of NGF. Expression of S100B in PC12 cells resulted in activation of Akt; increased levels of p21WAF1, an inhibitor of cyclin-dependent kinase (cdk) 2 and a positive regulator of cdk4; increased p21WAF1-cyclin D1 complex formation; and increased phosphorylation of the retinoblastoma suppressor protein, Rb. These S100B-induced effects, as well as the reduced ability of S100B+ PC12 cells to respond to NGF, were dependent on Akt activation because they were remarkably reduced or abrogated in the presence of LY294002, an inhibitor of the Akt upstream kinase phosphatidylinositol 3-kinase. Thus, S100B might promote cell proliferation and interfere with NGF-induced PC12 cell differentiation by stimulating a p21WAF1/cyclin D1/cdk4/Rb/E2F pathway in an Akt-mediated manner.
 ...
PMID:S100B increases proliferation in PC12 neuronal cells and reduces their responsiveness to nerve growth factor via Akt activation. 1557 70

Cumulative evidence indicates that activation of cyclin D-dependent kinase 4/6 (cdk4/6) represents a major trigger of cell cycle reentry and apoptosis in vertebrate neurons. We show here the existence of another mechanism triggering cell cycle reentry in differentiating chick retinal neurons (DCRNs), based on phosphorylation of E2F4 by p38(MAPK). We demonstrate that the activation of p75(NTR) by nerve growth factor (NGF) induces nuclear p38(MAPK) kinase activity, which leads to Thr phosphorylation and subsequent recruitment of E2F4 to the E2F-responsive cdc2 promoter. Inhibition of p38(MAPK), but not of cdk4/6, specifically prevents NGF-dependent cell cycle reentry and apoptosis in DCRNs. Moreover, a constitutively active form of chick E2F4 (Thr261Glu/Thr263Glu) stimulates G(1)/S transition and apoptosis, even after inhibition of p38(MAPK) activity. In contrast, a dominant-negative E2F4 form (Thr261Ala/Thr263Ala) prevents NGF-induced cell cycle reactivation and cell death in DCRNs. These results indicate that NGF-induced cell cycle reentry in neurons depends on the activation of a novel, cdk4/6-independent pathway that may participate in neurodegeneration.
 ...
PMID:Nerve growth factor-induced cell cycle reentry in newborn neurons is triggered by p38MAPK-dependent E2F4 phosphorylation. 2258 72

Polybrominated diphenyl ether-153 (BDE-153) has been demonstrated to induce neuronal apoptosis in rat cerebral cortex and primary neurons. Neurotrophins and cholinergic enzymes play critical roles in the neuronal survival, maintenance, synaptic plasticity and learning memory, however, their roles in neuronal apoptosis following the BDE-153 treatment remain unclear. In this study, we firstly explored the possible predominant pathway underlying the neuronal apoptotic induced by the BDE-153 treatment in rat cerebral cortex, by measuring expression levels (mRNA and protein) of p53, caspase-3, 8, 9, calpain-1, and calpain-2, detected the levels (protein contents and mRNA) of neurotrophins including brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4), and measured acetylcholinesterase (AchE) and choline acetyltransferase (ChaT) activities in rat cerebral cortex and primary neurons following BDE-153 treatment with or without pretreatment with inhibitors. Results showed that the neuronal apoptosis induced by BDE-153 was dependent on p53, and dependent on more calpain-2 than caspase-3 in the cerebral cortex of rats. Following the BDE-153 treatment, the protein contents and mRNA levels of BDNF, GDNF, NGF, NT-3, and NT-4, as well as the AchE and ChaT activities were significantly decreased in the cerebral cortex and primary neurons when compared to the untreated group. When pretreated primary neurons with calpain inhibitor PD150606 or cyclin-dependent kinase (cdk5, the downstream complex of calpain) inhibitor Roscovitine, the neurotrophins contents and activities of ChaT and AchE were reverted, along with the improvement of neuron survival compared with BDE-153 treatment alone. We conclude that neurotrophins and cholinergic enzymes were regulated by the calpain-2 activation and its downstream cdk5 pathway, and which was involved in the neuronal apoptosis induced by the BDE-153 treatment.
 ...
PMID:Neurotrophins and cholinergic enzyme regulated by calpain-2: New insights into neuronal apoptosis induced by polybrominated diphenyl ether-153. 2962 59


<< Previous 1 2