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)

Human cytomegalovirus (HCMV) stimulates arrested cells to enter the cell cycle by activating cyclin-dependent kinases (Cdks), notably Cdk2. Several mechanisms are involved in the activation of Cdk2. HCMV causes a substantial increase in the abundance of cyclin E and stimulates translocation of Cdk2 from the cytoplasm to the nucleus. Further, the abundance of the Cdk inhibitors (CKIs) p21cip1/waf1 (p21cip1) and p27kip1 is substantially reduced. The activity of cyclin E/Cdk2 increases as levels of CKIs, particularly p21cip1, fall. We have previously shown that these phenomena contribute to priming the cell for efficient replication of HCMV. In this study, the mechanisms responsible for the decrease in p21cip1 levels after HCMV infection were investigated by measuring p21cip1 RNA and protein levels in permissive human lung (LU) fibroblasts after HCMV infection. Northern blot analysis revealed that p21cip1 RNA levels increased briefly at 3 h after HCMV infection and then decreased to their nadir at 24 h; thereafter, RNA levels increased to about 60% of the preinfection level. Western blot analysis demonstrated that the relative abundance of p21cip1 protein roughly paralleled the observed changes in initial RNA levels; however, the final levels of protein were much lower than preinfection levels. After a transient increase at 3 h postinfection, p21cip1 abundance declined sharply over the next 24 h and remained at a very low level through 96 h postinfection. The disparity between p21cip1 RNA and protein levels suggested that the degradation of p21cip1 might be affected in HCMV-infected cells. Treatment of HCMV-infected cells with MG132, an inhibitor of proteasome-mediated proteolysis, provided substantial protection of p21cip1 in mock-infected cells, but MG132 was much less effective in protecting p21cip1 in HCMV-infected cells. The addition of E64d or Z-Leu-Leu-H, each an inhibitor of calpain activity, to HCMV-infected cells substantially increased the abundance of p21cip1 in a concentration-dependent manner. To verify that p21cip1 was a substrate for calpain, purified recombinant p21cip1 was incubated with either m-calpain or mu-calpain, which resulted in rapid proteolysis of p21cip1. E64d inhibited the proteolysis of p21cip1 catalyzed by either m-calpain or mu-calpain. Direct measurement of calpain activity in HCMV-infected LU cells indicated that HCMV infection induced a substantial and sustained increase in calpain activity, although there was no change in the abundance of either m- or mu-calpain or the endogenous calpain inhibitor calpastatin. The observed increase of calpain activity was consistent with the increases in intracellular free Ca2+ and phospholipid degradation in HCMV-infected LU cells reported previously from our laboratory. Considered together, these results suggest that the increase in calpain activity observed following HCMV infection contributes significantly to the reduction of p21cip1 levels and the resultant cell cycle progression.
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PMID:Degradation of p21cip1 in cells productively infected with human cytomegalovirus. 1126 51

Hepatocellular carcinoma (HCC) is one of the most aggressive malignant diseases and is highly resistant to conventional chemotherapy. Neferine, a major bisbenzylisoquinoline alkaloid derived from the embryos of Nelumbo nucifera, has been reported a few physiological activities. However, the mechanisms of anticancer effects are not well understood and its detailed activities on Hep3B cells have not been determined. Our results suggest that neferine exhibited cytotoxicity against HCC Hep3B cells, but not against HCC Sk-Hep1 and THLE-3, a normal human liver cell line. In addition, consistent with the induction of G1/S phase cell population in flow cytometry, downregulation of c-Myc, cyclin D1, D3, CDK4, E2F-1, as well as dephosphorlyation of cdc2 by western blot analysis, as evidenced by the appearance of cell cycle arrest, were observed in Hep3B cells treated with neferine. Our results demonstrated neferine induced ER stress and apoptosis, acting through multiple signaling cascades by the activation of Bim, Bid, Bax, Bak, Puma, caspases-3, -6, -7, -8 and PARP, and the protein expression levels of Bip, calnexin, PDI, calpain-2 and caspase-12 were also upregulated dramatically by neferine treatment. Overexpression of GFP-LC3B by neferine resulted in a diffuse cytosolic GFP fluorescence and the strong fluorescent spots, representing autophagosomes. The significant reduction of the migration in Hep3B cells and the capillary tube-like formation of HUVECs by neferine were also determined. These observations reveal that the therapeutic potential of neferine in treating HCC Hep3B cells, containing copies of hepatitis B virus (HBV) genomes.
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PMID:Neferine isolated from Nelumbo nucifera enhances anti-cancer activities in Hep3B cells: molecular mechanisms of cell cycle arrest, ER stress induced apoptosis and anti-angiogenic response. 2374 59

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.
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PMID:Neurotrophins and cholinergic enzyme regulated by calpain-2: New insights into neuronal apoptosis induced by polybrominated diphenyl ether-153. 2962 59