Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated inhibitory activity of nerve growth factor (NGF) on apoptosis of murine peritoneal exudate neutrophils. During culture for 9 h, apoptotic cells were identified by morphological changes under a light microscope: nuclear pyknosis and chromatin condensation with or without cytoplasmic vacuolation. The apoptotic state was confirmed by DNA fragmentation indicating the endogenous endonuclease activation. When neutrophils were incubated in the presence of NGF, the proportion of cells with the morphological changes was decreased in a dose-dependent manner, and the development of the characteristic DNA fragmentation was restricted. The apoptosis-suppressing activity of NGF was abolished by the addition of anti-NGF monoclonal antibody. These results suggest that NGF may suppress neutrophil apoptosis by preventing the endogenous endonuclease activation.
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PMID:Nerve growth factor suppresses apoptosis of murine neutrophils. 149 39

Past studies have shown that serum-free cultures of PC12 cells are a useful model system for studying the neuronal cell death which occurs after neurotrophic factor deprivation. In this experimental paradigm, nerve growth factor (NGF) rescues the cells from death. It is reported here that serum-deprived PC12 cells manifest an endonuclease activity that leads to internucleosomal cleavage of their cellular DNA. This activity is detected within 3 h of serum withdrawal and several hours before any morphological sign of cell degeneration or death. NGF and serum, which promote survival of the cells, inhibit the DNA fragmentation. Aurintricarboxylic acid (ATA), a general inhibitor of nucleases in vitro, suppresses the endonuclease activity and promotes long-term survival of PC12 cells in serum-free cultures. This effect appears to be independent of macromolecular synthesis. In addition, ATA promotes long-term survival of cultured sympathetic neurons after NGF withdrawal. ATA neither promotes nor maintains neurite outgrowth. It is hypothesized that the activation of an endogenous endonuclease could be responsible for neuronal cell death after neurotrophic factor deprivation and that growth factors could promote survival by leading to inhibition of constitutively present endonucleases.
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PMID:Aurintricarboxylic acid rescues PC12 cells and sympathetic neurons from cell death caused by nerve growth factor deprivation: correlation with suppression of endonuclease activity. 165 5

Human SY5Y neuroblastoma cells which were differentiated in culture by treatment with 7S murine nerve growth factor for 5 weeks and selection with aphidicolin (L. Jensen, Dev. Biol. 120:56-64, 1987) demonstrated a considerably slower rate of removal of DNA adducts of benzo[a]pyrene, benzo[a]pyrenediolepoxide, and N7-methylguanine than did undifferentiated mitotic cells. A dramatic decline in unscheduled DNA synthesis induced by UV radiation was similarly observed. DNA polymerase beta and uracil DNA glycosylase were unchanged after differentiation, DNA polymerase alpha and DNA methylase decreased roughly threefold, and total apurinic-apyrimidinic endonuclease activity increased roughly threefold after treatment.
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PMID:A reduced rate of bulky DNA adduct removal is coincident with differentiation of human neuroblastoma cells induced by nerve growth factor. 314 94

The stabilities of different mRNA species were analyzed in a reticulocyte lysate system under protein-synthesizing conditions. In all cases examined the relative mRNA degradation by reticulocyte ribonucleases as well as by the interferon-modulated (2'-5') (A)n-dependent endonuclease correlated with the extent of (U)nA sequences within the 3' non-coding region. The experimental data presented indicate that according to their stabilities at least three major mRNA groups may be identified: (a) (U)nA-poor mRNAs (e.g. globin) are essentially stable and are only slightly degraded by the (2'-5')(A)n-dependent endonuclease; (b) mRNA species with intermediate (U)nA levels (e.g. Ig alpha and Ig mu heavy-chain mRNAs) are partially degraded by general ribonuclease activity and further degraded by the (2'-5')(A)n-dependent endonuclease and (c) (U)nA-rich mRNA species (such as c-myc and non-skeletal actin mRNAs) are inherently unstable and are extremely sensitive to degradation by general ribonuclease activity. A survey of mRNA nucleotide sequences demonstrated that without exception (U)nA-rich stretches appeared more frequently within the 3' non-coding region than in the coding or 5' non-coding regions. A comparison of 3' non-coding region sequences from 92 different mRNAs revealed that transiently expressed mRNAs, such as the interleukins, nerve growth factor, epidermal growth factor receptor, c-myc, c-fos, c-myb and several other oncogenes as well as interferons alpha, beta and gamma were exceptionally (U)nA-rich. It is postulated that differential mRNA stability may be partly determined by the primary nucleotide sequence and in particular by (U)nA sequences within the 3' non-coding region. This may represent a novel post-transcriptional strategy employed by the cell to selectively retain or destroy discrete mRNA species.
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PMID:Differential mRNA stability to reticulocyte ribonucleases correlates with 3' non-coding (U)nA sequences. 335

Peroxynitrite is a powerful oxidant formed by the near-diffusion-limited reaction of nitric oxide with superoxide. Large doses of peroxynitrite (> 2 mM) resulted in rapid cell swelling and necrosis of undifferentiated PC12 cells. However, brief exposure to lower concentrations of peroxynitrite (EC50 = 850 microM) intially (3-4 h) caused minimal damage to low-density cultures. By 8 h, cytoplasmic shrinkage with nuclear condensation and fragmentation became increasingly evident. After 24 h, 36% of peroxynitrite-treated cells demonstrated these features associated with apoptosis. In addition, 46% of peroxynitrite-treated cells demonstrated DNA fragmentation (by terminal-deoxynucleotide transferase-mediated dUTP-digoxigenin nick end-labeling) after 7 h, which was inhibited by posttreatment with the endonuclease inhibitor aurintricarboxylic acid. Serum starvation also resulted in apoptosis in control cells (23%), the percentage of which was not altered significantly by peroxynitrite treatment. Although peroxynitrite is known to be toxic to cells, the present study provides a first indication that peroxynitrite induces apoptosis. Furthermore, pretreatment of cells with nerve growth factor or insulin, but not epidermal growth factor, was protective against peroxynitrite-induced apoptosis. However, both acidic and basic fibroblast growth factors greatly increased peroxynitrite-initiated apoptosis, to 63 and 70%, respectively. Thus, specific trophic factors demonstrate differential regulation of peroxynitrite-induced apoptosis in vitro.
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PMID:Peroxynitrite-induced cytotoxicity in PC12 cells: evidence for an apoptotic mechanism differentially modulated by neurotrophic factors. 756 48

The mechanisms that lead ultimately to neuronal death in pathological ageing of the brain remain mostly unknown as in the case of Parkinson's disease where there is a progressive and selective loss of dopaminergic neurons within the substantia nigra. Dopamine-expressing PC12 cells that were neuronally differentiated by nerve growth factor treatment were chosen as a culture model in which to study some of the changes that may occur during the course of the degenerative process. They were exposed to the calcium ionophore A23187 in order to produce a sustained rise in cytoplasmic calcium, a phenomenon related to various pathological conditions. The degenerative effects of the ionophore were dose- and time-dependent. They were characterized by early fragmentation of the neurites followed ultimately by a loss in cell viability. Biochemical changes, such as a decrease in [3H]dopamine uptake and modulations of the tyrosine hydroxylase gene, were detected before macroscopic evidence of cell suffering (e.g. neurite fragmentation) could be observed. Although an ongoing degenerative process was occurring in cell somata, PC12 cells were able to recover upon ionophore withdrawal. Characteristics of apoptosis such as chromatin condensation and DNA fragmentation were detectable in a small population of dying cells. DNA fragmentation could be prevented by the endonuclease inhibitor aurintricarboxylic acid. New protein synthesis was not required, as cycloheximide failed to prevent degeneration. Taken together, these results suggest that differentiated PC12 cells react to calcium stress through a sequence of regulatory processes which appears to be independent of the apoptotic pathway.
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PMID:Morphological and molecular characterization of the response of differentiated PC12 cells to calcium stress. 791 84

Terminally differentiated PC12 cells are a useful neuron-like model for studying programmed cell death in response to nerve growth factor (NGF) deprivation. This in vitro model was used to investigate the mechanism by which cyanide-induced histotoxic hypoxia produces neuronal degeneration. Treatment of undifferentiated PC12 cells with 0.1 mM KCN for 24 h did not produce cell death. In contrast, treatment of differentiated PC12 cell cultures with 0.1 mM KCN for 24 h increased cell death by 43% when compared with control cultures, as measured by trypan blue dye exclusion and lactate dehydrogenase release assays. The Ca2+/Mg(2+)-dependent endonuclease inhibitor aurintricarboxylic acid and the transcriptional inhibitor actinomycin D partially attenuated hypoxic toxicity, suggesting roles for endonuclease activation and transcription in this model of neuronal death. Extracted DNA from cyanide-treated neurons demonstrated cleavage into oligonucleosomal fragments on gel electrophoresis. Transmission electron microscopic analysis showed morphological changes consistent with apoptotic cell death, including membrane blebbing and convolution, as well as chromatin condensation and margination to the nuclear membrane. Addition of either ascorbate or catalase to the cultures partially attenuated the loss of cell viability induced by cyanide, and decreased the incidence of apoptotic cells after treatment, based on the in situ detection of DNA strand breaks. The ability of cyanide to elevate intracellular oxidant species was determined by microfluorescence in differentiated PC12 cells loaded with the oxidant-sensitive dye 2',7'-dichlorofluorescin. Exposure of cells to 0.1 mM KCN produced a rapid generation of oxidants that was blocked approximately 50% by ascorbate or catalase. These observations indicate that cyanide induces apoptosis in terminally differentiated, and not undifferentiated, PC12 cells, and that antioxidants significantly reduce the incidence of cyanide-induced apoptosis.
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PMID:Cyanide-induced apoptosis and oxidative stress in differentiated PC12 cells. 875 10

Neuron numbers in developing vertebrate organisms are regulated by the availability of growth factors which promote their survival. However, neuron survival may also be regulated by growth factors which promote rather than prevent cell death. This study examined the effects of bone morphogenetic proteins (BMPs) in inducing apoptosis of MAH cells, an immortalized sympathoadrenal progenitor cell line. Treatment of MAH cells with BMP2 or BMP4 killed the cells in a dose-dependent manner. By contrast, treatment with BMP7 or TGFbeta1 failed to affect survival, suggesting that induction of apoptosis is specific to the dpp subgroup of BMPs. Survival after treatment with BMP2 or BMP4 required addition of fibroblast growth factor (FGF) and nerve growth factor (NGF), indicating that BMP treatment made the neurons dependent upon an exogenous factor for survival. Several experimental observations suggested an apoptotic mechanism for BMP-induced death. After BMP2 treatment, the cells progressively shrank and became pyknotic. Further, there was prominent endonucleosomic cleavage of DNA (laddering) as well as TUNEL staining. Moreover, BMP-induced death was inhibited by the caspase inhibitor z-VAD and was partially prevented by the endonuclease inhibitor aurintricarboxylic acid. These observations suggest that neuron numbers may be regulated by factors which promote death and that exposure to such factors may be a signal for the development of dependence upon other growth factors for survival.
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PMID:Bone morphogenetic proteins induce apoptosis and growth factor dependence of cultured sympathoadrenal progenitor cells. 952 85

DNase gamma, which cleaves chromosomal DNA into nucleosomal units (DNA ladder formation), has been suggested to be the critical component of apoptotic machinery. Using rat pheochromocytoma PC12 cells, which are differentiated to sympathetic neurons by nerve growth factor (NGF), we investigated whether DNase gamma-like enzyme is present in neuronal cells and is involved in neuronal cell death. The nuclear auto-digestion assay for DNase catalyzing internucleosomal DNA cleavage revealed that nuclei from neuronal differentiated PC12 cells contain acidic and neutral endonucleases, while nuclei from undifferentiated PC12 cells have only acidic endonuclease. The DNA ladder formation observed in isolated nuclei from neuronal differentiated PC12 cells at neutral pH requires both Ca(2+) and Mg(2+), and is sensitive to Zn(2+). The molecular mass of the neutral endonuclease present in neuronal differentiated PC12 cell nuclei is 32000 as determined by activity gel analysis (zymography). The properties of the neuronal endonuclease present in neuronal differentiated PC12 cell nuclei were similar to those of purified DNase gamma from rat thymocytes and splenocytes. Interestingly, in neuronal differentiated PC12 cells, internucleosomal DNA fragmentation is observed following NGF deprivation, whereas undifferentiated PC12 cells fail to exhibit DNA ladder formation during cell death by serum starvation. These results suggest that the DNase gamma-like endonuclease present in neuronal differentiated PC12 cell nuclei is involved in internucleosomal DNA fragmentation during apoptosis, induced by NGF deprivation.
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PMID:Presence of DNase gamma-like endonuclease in nuclei of neuronal differentiated PC12 cells. 1464 7

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