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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanisms involved in the translocation of exogenously added genetic information through the cellular cytoplasm and into the nucleus are essentially unknown. Several trans-cytoplasmic translocation systems operate within cells to transport information received by the plasma membrane into the nucleus. Protein kinase C may be functionally involved in many of these translocation mechanisms. In order to explore the involvement of protein kinase C activation in the cytoplasmic translocation of DNA, NIH3T3 fibroblasts were transfected using the calcium-phosphate co-precipitation method with a plasmid containing the lacZ gene and treated with tetradecanoylphorbol 12,13-acetate (TPA) or 1,2-dioctanoylglycerol (DiC8). Addition of TPA or DiC8 immediately after glycerol shock resulted in a 5-7-fold increase in the number of cells expressing beta-galactosidase as well as a concomitant increase in the total amount of beta-galactosidase activity in the population during periods of transient and stable expression. TPA added at later times resulted in lesser increases in the efficiency of transfection. In contrast, TPA added at the time of addition of the calcium-phosphate precipitate inhibited transfection. In support of a role for protein kinase C activation in enhancing DNA transfection, the TPA analog 4 alpha-phorbol 12,13-didecanoate, which does not activate protein kinase C, was ineffective at enhancing transfection. Furthermore, treatment of cells with the protein kinase C inhibitor sphingosine blocked the TPA-mediated increase in transient and stable expression. The results suggest that protein kinase C activation enhances transfection of exogenous DNA through an as yet unknown mechanism.
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PMID:Potentiation of DNA mediated gene transfer in NIH3T3 cells by activators of protein kinase C. 190 Apr 39

Exposure of PC12-VG cells to an extremely low frequency magnetic field (ELFMF) enhanced the beta-galactosidase gene expression stimulated by treatment of the cells with forskolin. The enhancing effect of the ELFMF was inhibited by treatment of the cells with a specific inhibitor of PKC, calphostin C, as well as with the Ca2+ entry blockers nifedipin and dantrolen. Enhancement appeared within the first hour of a 4h forskolin treatment when the ELFMF was given at different times during culture. We speculate that exposure of PC12-VG cells to an ELFMF during the early response to forskolin treatment affects cell signal transduction, resulting in enhanced gene expression.
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PMID:Enhancement of beta-galactosidase gene expression in rat pheochromocytoma cells by exposure to extremely low frequency magnetic fields. 761 92

Because metallothionein (MT) is elevated and may be protective in UV-irradiated skin, we have studied the effects of UV and other agents on MT transcription using the sheep MT 1A promoter, linked to the beta-galactosidase gene and stably transfected into human cell lines. beta-galactosidase reporter activity was inducible by adding Zn2+ ions to the medium (100 microM for 2-4 h). Two differentiating agents, butyric acid and azelaic bishydroxamic acid (ABHA), significantly increased the response to Zn2+ in a melanoma cell line (MM96L-gal). UVB (280-315 nm) had two distinct, time-dependent effects. During the first 4 h after irradiation, high doses of UVB inhibited induction by Zn2+, an effect that was made more acute by simultaneous exposure to the differentiating agents. These changes in reporter activity were not due to alterations in Zn2+ transport into the cell. The UVB-depressed MT response subsequently recovered and by 24 h was double the control, yet remained sensitive to ABHA. Reporter activity in transfected HeLa cells differed from that in MM96L, being depressed 4 and 24 h after UVB and insensitive to ABHA at both times. Galactosidase reporter activity driven by non-MT promoters was not affected by these treatments. Dependence of MT transcriptional activity on UV-related DNA damage could be inferred because equitoxic UVC (254 nm) affected the response to Zn2+ in a similar fashion, whereas UVA, cisplatin and a methylating agent had no effect. The MT response was partly dependent on the PKC signal transduction pathway because it was inhibited by phorbol ester in HeLa, and by bisindolyl maleimide in HeLa and MM96L. The biphasic MT transcriptional response may model a signal transduction pathway that gives an early, depressed response to acute UV damage, with exacerbation by concurrent differentiation stimuli, but switches to a positive, cell-specific and potentially protective response at later times.
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PMID:Biphasic response of the metallothionein promoter to ultraviolet radiation in human melanoma cells. 907 40

Analysis of the expression of a number of known genes in cultured human cells has revealed UVB-induced changes that may be specific for melanocytic cells. The response of c-fos, p53 and HIV-LTR reporter constructs to UVB and UVC was reduced in MM96L melanoma cells compared to HeLa. Cell cycle arrest produced by UVA, gamma radiation, cisplatin or the antimetabolite deoxyinosine differed from that of UVB. Cell cycle analysis after multiple doses of UVB raised the possibility that UVB-induced pRb depletion could result in increased mutation and thus enhanced tumourigenesis of irradiated melanocytes in skin subjected to a defined pattern of UVB exposure. To extend the analysis of gene expression in cultured melanocytic cells to uncharacterised genes, promoter trap cell clones containing unknown genes 'tagged' by a beta-galactosidase reporter construct were generated from MM96L cells. Altered gene expression in clones treated with a panel of DNA-damaging agents was quantitated by measurement of beta-galactosidase activity. Of the clones containing 'tagged' endogenous promoters induced by UVB, 52% were induced only by UVB and not by other DNA-damaging agents (cisplatin, N-methyl-N-nitro-nitrsoguanidine, fotemustine). One third of the clones were also activated by TPA suggesting that general DNA damage responses involving PKC are activated less frequently than unique pathways of gene activation. Overall, 60% of the 50 clones that responded to the panel of agents were induced by only one of the agents, indicating that a high proportion of genes are induced by agent-specific mechanisms. In the long term, promoter trapping may allow the full repertoire of UVB-inducible genes to be characterised.
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PMID:UVB-specific regulation of gene expression in human melanocytic cells: cell cycle effects and implication in the generation of melanoma. 992 Apr 26

By interaction cloning (yeast two-hybrid system) using the catalytic domain of protein kinase Czeta (PKCzeta) as bait, we cloned a human full-length cDNA with 62% nucleotide homology to the A6 protein recently cloned and characterized by Beeler et al. [Beeler, J.F., LaRochelle, W.J., Chedid, M., Tronick, S.R. & Aaronson, S. A. (1994) Mol. Cell. Biol. 14, 982-988]. The deduced amino acid sequence (349 amino acids) of the A6-related protein (A6rp) contained potential actin-binding sites and ATP-binding sites. We also cloned the murine homolog of A6rp. Human A6rp was expressed in an in-vitro transcriptional/translational system with an apparent molecular mass of 40 kDa and as a glutathione S-transferase (GST) fusion protein in bacteria. A polyclonal anti-(A6rp) was raised in rabbits and used for the identification of A6rp by immunoblotting. A6rp was found to be expressed at the mRNA and the protein levels in all cells and tissues investigated. GST-A6rp was phosphorylated by PKCzeta but not significantly by other PKC isoenzymes. Moreover, it was phosphorylated by casein kinase 2 and most effectively by the tyrosine kinase Src. In contrast to GST-A6rp, GST-A6 was also phosphorylated by PKC isoforms other than PKCzeta and strongly by CK2, but just weakly by Src. In contrast to the results of Beeler et al. on beta-galactosidase-A6, we were unable to demonstrate autokinase activity or tyrosine phosphorylation of either GST-A6 or GST-A6rp. In accordance with the potential ATP-binding sites, both proteins were able to bind ATP.
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PMID:Cloning, expression and characterization of an A6-related protein. 1040 62

Opi1p is a negative regulator of expression of phospholipid-synthesizing enzymes in the yeast Saccharomyces cerevisiae. In this work, we examined the phosphorylation of Opi1p by protein kinase C. Using a purified maltose-binding protein-Opi1p fusion protein as a substrate, protein kinase C activity was time- and dose-dependent, and dependent on the concentrations of Opi1p and ATP. Protein kinase C phosphorylated Opi1p on a serine residue. The Opi1p synthetic peptide GVLKQSCRQK, which contained a protein kinase C sequence motif at Ser(26), was a substrate for protein kinase C. Phosphorylation of a purified S26A mutant maltose-binding protein-Opi1p fusion protein by the kinase was reduced when compared with the wild-type protein. A major phosphopeptide present in purified wild-type Opi1p was absent from the purified S26A mutant protein. In vivo labeling experiments showed that the phosphorylation of Opi1p was physiologically relevant, and that the extent of phosphorylation of the S26A mutant protein was reduced by 50% when compared with the wild-type protein. The physiological consequence of the phosphorylation of Opi1p at Ser(26) was examined by measuring the effect of the S26A mutation on the expression of the phospholipid synthesis gene INO1. The beta-galactosidase activity driven by an INO1-CYC-lacI'Z reporter gene in opi1Delta mutant cells expressing the S26A mutant Opi1p was about 50% lower than that of cells expressing the wild-type Opi1p protein. These data supported the conclusion that phosphorylation of Opi1p at Ser(26) mediated the attenuation of the negative regulatory function of Opi1p on the expression of the INO1 gene.
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PMID:Phosphorylation of the yeast phospholipid synthesis regulatory protein Opi1p by protein kinase C. 1139 23

Protein kinase C (PKC) epsilon and PKCdelta translocation in neonatal rat ventricular myocytes (NRVMs) is accompanied by subsequent activation of the ERK, JNK, and p38(MAPK) cascades; however, it is not known if either or both novel PKCs are necessary for their downstream activation. Use of PKC inhibitors to answer this question is complicated by a lack of isoenzyme specificity, and the fact that many PKC inhibitors stimulate JNK and p38(MAPK) activity. Therefore, replication-defective adenoviruses (Advs) encoding constitutively active (ca) mutants of PKCepsilon and PKCdelta were used to test if either or both of these PKCs are sufficient to activate ERKs, JNKs, and/or p38(MAPK) in NRVMs. Adv-caPKCepsilon infection (1 to 25 multiplicities of viral infection (MOI); 4 to 48 hours) increased total PKCepsilon levels in a time- and dose-dependent manner, with maximal expression observed 8 hours after Adv infection. Adv-caPKCepsilon induced a time- and dose-dependent increase in phosphorylated p42 and p44 ERKs, as compared with a control Adv encoding beta-galactosidase (Adv-nebetagal). Maximal ERK phosphorylation occurred 8 hours after Adv infection. In contrast, JNK was only minimally activated, and p38(MAPK) was relatively unaffected. Adv-caPKCdelta infection (1 to 25 MOI, 4 to 48 hours) increased total PKCdelta levels in a similar fashion. Adv-caPKCdelta (5 MOI) induced a 29-fold increase in phosphorylated p54 JNK, and a 15-fold increase in phosphorylated p38(MAPK) 24 hours after Adv infection. In contrast, p42 and p44 ERK were only minimally activated. Whereas neither Adv induced NRVM hypertrophy, Adv-caPKCdelta, but not Adv-caPKCepsilon, induced NRVM apoptosis. We conclude that the novel PKCs differentially regulate MAPK cascades and apoptosis in an isoenzyme-specific and time-dependent manner.
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PMID:Differential activation of mitogen-activated protein kinase cascades and apoptosis by protein kinase C epsilon and delta in neonatal rat ventricular myocytes. 1170 8

Osteoprotegerin (OPG), a secreted member of the tumor necrosis receptor superfamily, is a potent inhibitor of osteoclast formation and bone resorption. Parathyroid hormone (PTH), a potent inducer of osteoclast formation, suppresses OPG mRNA expression in vitro and in vivo. To determine the molecular basis of this inhibition, we analyzed the effects of PTH on the human OPG promoter (-5917 to +19) fused with beta-galactosidase reporter gene in stable and transient transfections into rat osteoblast-like UMR106 cells. The effect of PTH on OPG promoter expression was biphasic and concentration-dependent. PTH (1-100 nM) induced the transcriptional activity of the OPG promoter (1.7-fold) at 8 h followed by a gradual decrease with maximal inhibition (6.6-fold) at 24-48 h. To ascertain the signal transduction pathways mediating PTH (1-38) effects on OPG gene expression, we compared the effects of PTH with PTH analogs, parathyroid hormone-related protein 1-34 (PTHrP 1-34), forskolin, 3-isobutyl-1-methylxanthine (IBMX), dibutyryl cAMP, phorbol-12-myristate-13-acetate (PMA), thapsigargin and calcium ionophore A23187. PTH 1-31 and PTHrP 1-34, which stimulate the cAMP/PKA pathway, and other activators of cAMP/PKA, forskolin, IBMX, N(6), O(2')-dibityryl adenosine 3',5'-cyclic monophosphate (dibutyryl cAMP), all elicited a similar biphasic response on OPG promoter expression. PTH analogs PTH 3-34 and PTH 7-34, that do not stimulate cAMP production, had no effect on OPG expression. In contrast, phorbol-12-myristate-13-acetate (PMA), an activator of PKC, stimulated OPG promoter expression, while thapsigargin and calcium ionophore A23187, which increase intracellular Ca(2+), showed a dose-dependent inhibition of OPG promoter expression. To delineate the promoter sequences that mediate the inhibitory effects of PTH on OPG transcription, we analyzed systematic deletions of the OPG promoter for responsiveness in transient transfection assays. The major inhibitory effects of PTH were localized to 391 bp (-372 to +19) of the proximal promoter. Deletions of the promoter region led to a complete loss of responsiveness. Taken together, these results demonstrate that the inhibitory effects of PTH on OPG are mediated at the transcriptional level through cis elements in the proximal promoter. The similar biphasic response of OPG to PTH, PTH 1-31, PTHrP 1-34, forskolin, IBMX and dibutyryl cAMP suggests that PTH regulates OPG transcription via activation of the cAMP/PKA signal transduction pathway.
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PMID:Identification of signal transduction pathways and promoter sequences that mediate parathyroid hormone 1-38 inhibition of osteoprotegerin gene expression. 1174 11

Previously, we have demonstrated that increased superoxide generation plays a role in the nitric oxide (NO)-mediated inhibition of endothelial NO synthase (NOS III) in endothelial cells (ECs). In this study we demonstrate that the source of the superoxide is likely due to both NADPH oxidase and NOS III itself. Further, this increase appears to be linked to the activation of PKC, as PMA could mimic the increase and PKC inhibition ameliorate the increase. To further investigate this phenomenon we determined the effect of overexpression of copper-zinc superoxide dismutase (CuZn-SOD) and Manganese-SOD (Mn-SOD) on the inhibitory effects of NO. Using adenoviral infection we demonstrated that SOD activity was increased and superoxide levels decreased, in both CuZn-SOD and Mn-SOD overexpressing cells compared to cells infected with an adenovirus expressing bacterial beta-galactosidase protein. However, only the CuZn-SOD overexpression reduced the NO-mediated inhibition of NOS III. In addition, the level of NO-induced peroxynitrite generation and nitrated NOS III protein were reduced only in the CuZn-SOD overexpressing cells. In conclusion, our results indicate that superoxide and peroxynitrite are involved in the inhibition of NOS III by NO, and that the scavenging of superoxide may be necessary to prevent NOS III inhibition during treatments that involve inhaled NO or NO donors.
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PMID:The overexpression of copper-zinc superoxide dismutase protects NOS III from nitric oxide-mediated inhibition. 1248 93

Protein kinase C (PKC) isoenzymes play a critical role in cardiomyocyte hypertrophy. At least three different phorbol ester-sensitive PKC isoenzymes are expressed in neonatal rat ventricular myocytes (NRVMs): PKC-alpha, -delta, and -epsilon. Using replication-defective adenoviruses (AdVs) that express wild-type (WT) and dominant-negative (DN) PKC-alpha together with phorbol myristate acetate (PMA), which is a hypertrophic agonist and activator of all three PKC isoenzymes, we studied the role of PKC-alpha in signaling-specific aspects of the hypertrophic phenotype. PMA induced nuclear translocation of endogenous and AdV-WT PKC-alpha in NRVMs. WT PKC-alpha overexpression increased protein synthesis and the protein-to-DNA (P/D) ratio but did not affect cell surface area (CSA) or cell shape compared with uninfected or control AdV beta-galactosidase (AdV betagal)-infected cells. PMA-treated uninfected cells displayed increased protein synthesis, P/D ratio, and CSA and elongated morphology. PMA did not further enhance protein synthesis or P/D ratio in AdV-WT PKC-alpha-infected cells. To assess the requirement of PKC-alpha for these PMA-induced changes, AdV-DN PKC-alpha or AdV betagal-infected NRVMs were stimulated with PMA. Without PMA, AdV-DN PKC-alpha had no effects on protein synthesis, P/D ratio, CSA, or shape vs. AdV betagal-infected NRVMs. PMA increased protein synthesis, P/D ratio, and CSA in AdV betagal-infected cells, but these parameters were significantly reduced in PMA-stimulated AdV-DN PKC-alpha-infected NRVMs. Overexpression of DN PKC-alpha enhanced PMA-induced cell elongation. Neither WT PKC-alpha nor DN PKC-alpha affected atrial natriuretic factor gene expression. Insulin-like growth factor-1 also induced nuclear translocation of endogenous PKC-alpha. PMA but not WT PKC-alpha overexpression induced ERK1/2 activation. However, AdV-DN PKC-alpha partially blocked PMA-induced ERK activation. Thus PKC-alpha is necessary for certain aspects of PMA-induced NRVM hypertrophy.
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PMID:Protein kinase C-alpha-induced hypertrophy of neonatal rat ventricular myocytes. 1527 71


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