Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To evaluate possible functional differences between basic fibroblast growth factor (FGF) 2 isoforms we analyzed the effects of the 18-kDa FGF-2 which mainly localizes in the cytosol and that of the nuclear-targeted 22.5-kDa form on FGF receptors (FGFR) expression. These peptides were expressed at low amounts through a retroviral-infection system. Point mutated FGF-2 cDNAs under the control of the beta-actin promoter were used to infect a pancreatic cell line (AR4 2J) which does not produce FGF-2. Saturation and competition binding studies with 125I-FGF-2 revealed a 3-fold increase in both high and low affinity receptors in cells expressing the 22.5-kDa form and a 2-fold increase only in the high affinity receptors in cells producing the 18-kDa form. Kd values and molecular weights of the high affinity receptors were unaffected. Increasing cell densities or cell treatment with exogenous FGF-2 resulted in FGFR down-regulation as in control cells. Neutralizing anti-FGF-2 antibodies and suramin did not affect receptor density in control and in cells producing the 22.5-kDa form but further increased by 60 and 80%, respectively, the receptor level in cells synthesizing the 18-kDa form. These data suggest the involvement of the intracellular stored FGF-2 in FGFR up-regulation. Although all cells expressed FGFR-1, -2, and -3 mRNA only the FGFR-1 transcript was found increased, 6-fold in 22.5-kDa expressing cells and 3-fold in cell producing the shortest secreted isoform. The increase in FGFR-1 mRNA levels in the 22.5-kDa expressing cells was due to enhanced stability of the transcript. Confocal microscopy detected the presence of FGFR-1 at the cell surface whereas secretory isoforms of the receptor were not observed. Reverse transcriptase-polymerase chain reaction did not reveal significant differences in the expression of FGFR-1 variants. In the 22.5-kDa expressing cells exogenous FGF-2 evoked a stronger translocation of the calcium-phospholipid-dependent PKC. These results indicate that the transfected FGF-2 isoforms up-regulated FGFR-1 mRNA and protein. The 22.5-kDa form acted by increasing FGFR-1 mRNA stability enhancing cell responses to exogenous FGF-2.
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PMID:Differential regulation of fibroblast growth factor (FGF) receptor-1 mRNA and protein by two molecular forms of basic FGF. Modulation of FGFR-1 mRNA stability. 862 30

Human peritoneal mesothelial cells (HPMC) respond to tumor necrosis factor alpha (TNF alpha) by releasing various cytokines that may activate the endothelium and induce recruitment of leukocytes during peristonitis. We characterized the receptors for TNF on HPMC to elucidate their functions in peritonitis. Scatchard analysis determined the presence of 70 x 10(3) TNF receptors/cell with a kDa of 0.44 nM. TNF receptor 1 (TNF-R1, p55) and TNF-R2 (p75) mRNA were demonstrated by reverse-transcriptase-PCR (RT-PCR). TNF-R1 protein was solely detected by flow cytometry (FCM). Interleukin-1 alpha (IL-1 alpha) induced down-regulation of TNF-R1. This was concomitant with accumulation of soluble TNF-R1 (sTNF-R1) detected by specific ELISA. LPS had a lower TNF-R1-shedding activity while TNF alpha did not induce shedding. The IL-1-induced-sTNF-R1-shedding was suppressed by the protein-kinase-A (PKA) inhibitor, H-8, or by H-7, the inhibitor of both PKC and PKA, but not by the specific PKC inhibitor GF. These experiments suggest a role for PKA in the IL-1-shedding signal. No change in TNF-R1 mRNA levels was observed after IL-1 alpha or TNF alpha stimulation while TNF-R2 (p75) mRNA basal levels transiently increased three to fivefold, reaching a peak after four hours followed by an accumulation of sTNF-R2 in the supernatant. Our data suggest that the main receptor expressed on HPMC is TNF-R1. Down-regulation and shedding of TNF-R1 induced by IL-1, and the transient expression of TNF-R2 induced by IL-1 and TNF, may regulate the responses to TNF by HPMC. These results may be important in understanding the inflammatory process of peritonitis were TNF plays a major role.
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PMID:TNF-receptors on human peritoneal mesothelial cells: regulation of receptor levels and shedding by IL-1 alpha and TNF alpha. 880 91

Transcription by nonsegmented negative-strand RNA viruses is mediated by the viral RNA-dependent RNA polymerase and transcriptional cofactor P. The P protein is activated by phosphorylation, an event initiated by cellular kinases. The kinase used differs among this group of RNA viruses; vesicular stomatitis virus and respiratory syncytial virus utilize casein kinase II (CKII), whereas human parainfluenza virus type 3 utilizes PKC isoform zeta (PKC-zeta) for activation of its P protein. To identify the cellular kinase(s) involved in the phosphorylation of the canine distemper virus (CDV) P protein, we used recombinant CDV P in phosphorylation assays with native kinase activities present in CV1 cell extracts or purified CKII and PKC isoforms. Here, we demonstrate that the CDV P protein is phosphorylated by two cellular kinases, where PKC-zeta has the major and CKII the minor activities. In contrast, the P protein of another member of the morbillivirus genus, measles virus, is phosphorylated predominantly by CKII, whereas PKC-zeta has only minor activity. Selective inhibition of PKC-zeta activity within CV1 cells eliminated permissiveness to CDV replication, indicating an in vivo role for PKC-zeta in the virus replication cycle. The broad tissue expression of PKC-zeta parallels the pantropic nature of CDV infections, suggesting that PKC-zeta activity is a determinant of cellular permissiveness to CDV replication.
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PMID:Phosphorylation of canine distemper virus P protein by protein kinase C-zeta and casein kinase II. 918 3

Protein kinase C (PKC), a key component of the signaling pathways leading to proliferation and differentiation, consists of a family closely related serine/threonine protein kinases. The mRNA expression of these PKC isoforms has been characterized during hematopoietic differentiation. Using the reverse-transcriptase polymerase chain reaction technique, we have analyzed the levels of isoform transcripts in bone marrow CD34(+) hematopoietic progenitors and their progeny differentiated along erythroid, megakaryocyte, or granulocyte/monocyte lineages, upon exposure to growth factors. In contrast with isoforms alpha, beta(I), beta(II), delta, and epsilon, ubiquitously expressed, isoforms theta, eta/L, zeta, and iota/lambda exhibited a lineage-restricted expression. These qualitative changes, which allow to distinguish the erythroid and megakaryocyte phenotypes from the granulocyte/monocyte phenotype, include zeta exclusively upregulated in granulocytes/monocytes and theta, eta/L, and iota/lambda exclusively expressed in megakaryocytes and erythroblasts. In contrast, erythroblasts and megakaryocytes, which supposedly share a common bipotential progenitor, displayed only quantitative changes. These results evidence the selective expression of PKC isoforms at transcriptional and/or posttranscriptional levels in hematopoietic progenitors induced to differentiate, which may suggest a differential contribution of individual isoforms to cellular signaling.
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PMID:Differential expression of protein kinase C isoform transcripts in human hematopoietic progenitors undergoing differentiation. 1051 25

The activity-dependent remodeling of postsynaptic structure is a fundamental process underlying learning and memory. Insulin receptor substrate p53 (IRSp53), a key player in cytoskeletal dynamics, is enriched in the postsynaptic density (PSD) fraction, but its significance in synaptic functions remains unclear. We report here that IRSp53 is accumulated rapidly at the postsynaptic sites of cultured hippocampal neurons after glutamate or NMDA stimulation in an actin cytoskeleton-dependent manner. Pharmacological profiles showed that a PKC inhibitor, but not other kinase inhibitors, specifically suppressed the synaptic translocation of IRSp53 in response to NMDA, and the selective activation of PKC with phorbol ester markedly induced the synaptic translocation. Reverse transcriptase-PCR and Western blotting showed that IRSp53-S is the major isoform expressed in cultured hippocampal neurons. The synaptic targeting of IRSp53-S was found to be mediated through N-terminal coiled-coil domain and the PDZ (PSD-95/Discs large/zona occludens-1)-binding sequence at its C-terminal end and regulated by the PKC phosphorylation of its N terminus. In electrophysiological experiments, overexpression of IRSp53-S wild type and IRSp53-S mutant that is spontaneously accumulated at the postsynaptic sites enhanced the postsynaptic function as detected by an increased miniature EPSC amplitude. These data suggest that IRSp53 is involved in NMDA receptor-linked synaptic plasticity via PKC signaling.
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PMID:NMDA receptor-dependent synaptic translocation of insulin receptor substrate p53 via protein kinase C signaling. 1575 77

The phosphoprotein P of Borna disease virus (BDV) is an essential cofactor of the viral RNA-dependent RNA polymerase. It is preferentially phosphorylated at serine residues 26 and 28 by protein kinase C epsilon (PKCepsilon) and, to a lesser extent, at serine residues 70 and 86 by casein kinase II (CKII). To determine whether P phosphorylation is required for viral polymerase activity, we generated P mutants lacking either the PKCepsilon or the CKII phosphate acceptor sites by replacing the corresponding serine residues with alanine (A). Alternatively, these sites were replaced by aspartic acid (D) to mimic phosphorylation. Functional characterization of the various mutants in the BDV minireplicon assay revealed that D substitutions at the CKII sites inhibited the polymerase-supporting activity of P, while A substitutions maintained wild-type activity. Likewise, D substitutions at the PKC sites did not impair the cofactor function of BDV-P, whereas A substitutions at these sites led to increased activity. Interestingly, recombinant viruses could be rescued only when P mutants with modified PKCepsilon sites were used but not when both CKII sites were altered. PKCepsilon mutant viruses showed a reduced capacity to spread in cell culture, while viral RNA and protein expression levels in persistently infected cells were almost normal. Further mutational analyses revealed that substitutions at individual CKII sites were, with the exception of a substitution of A for S86, detrimental for viral rescue. These data demonstrate that, in contrast to other viral P proteins, the cofactor activity of BDV-P is negatively regulated by phosphorylation.
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PMID:Functional characterization of the major and minor phosphorylation sites of the P protein of Borna disease virus. 1737 20

A bush-type plant was selected from tropical pumpkin 'cga' (Cucurbita moschata Duchesne) in order to study the vine development in C. moschata. In this study, a novel gene encoding NADH dehydrogenase was isolated from the vine line (cgaV) of C. moschata, that was not expressed in the near isogenic bush line (cgaBu). This gene, designated as CmV1 (C. moschata vine 1), was 545 bp in length and was composed of a 477 bp open reading frame, which had 99% nucleotide similarity to the chloroplast ndhJ gene for NADH dehydrogenase subunit J from Brassica oleracea. The deduced amino acid sequence of CmV1 had 99% similarity to NADH dehydrogenase subunit J from Arabidopsis and had 98% similarity to NADH dehydrogenase subunit from Barbarea verna. Analysis of the basic characteristics of the CmV1 protein revealed that it has one Respiratory chain NADH dehydrogenase 30 kD subunit signature, three N-myristoylation sites, one Casein kinase II phosphorylation site, and one Protein kinase C phosphorylation site. Reverse transcriptase-PCR analysis showed that CmV1 was expressed at a high level in the internodes and hypocotyls and was expressed stronger in elongating internodes than in fully expanded internodes. In conclusion, results obtained in the present study suggest that CmV1 gene might play important roles in vine elongation of tropical pumpkin.
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PMID:Molecular cloning and expression of a bush related CmV1 gene in tropical pumpkin. 1930 73