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

---

Query: EC:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To elucidate the molecular mechanism of the stimulatory effect of thyrotropin on the gene regulation of alpha 1B adrenergic receptor in functioning rat thyroid (FRTL-5) cells, we established a competitive reverse-transcriptase (RT) polymerase chain reaction (PCR) and nuclear run-off assay to quantify changes in mRNA levels and transcription rates. A binding assay showed that FRTL-5 cells predominantly expressed alpha 1B adrenergic receptor and that thyrotropin increased its expression sevenfold. By means of RT-PCR, we found that thyrotropin induced an 11-fold increase in alpha 1B receptor mRNA abundance. The nuclear run-off assay demonstrated that thyrotropin caused a ninefold increase at the gene transcriptional level, which occurred in the presence of the protein synthesis inhibitor cycloheximide. The half-life of the alpha 1B receptor mRNA in cells incubated with thyrotropin for 1 h increased 1.5-fold but returned to the original value after 12 h. Dibutyryl cAMP and forskolin mimicked the stimulatory effects of thyrotropin on the gene transcriptional level. The 5'-flanking region of the rat alpha 1B receptor gene contained a putative cAMP responsive element (CRE) at nucleotide -438 relative to the translation start site. The promoter analysis using the reporter gene indicated that the CRE motif confers the cAMP sensitivity to the transcription of the rat alpha 1B receptor gene. These results demonstrated that a CRE-mediated mechanism is involved in the transcriptional regulation of the alpha 1B receptor gene by thyrotropin without requiring new protein synthesis.
...
PMID:cAMP responsive element-mediated regulation of the gene transcription of the alpha 1B adrenergic receptor by thyrotropin. 798 80

Ad4BP, a zinc finger DNA-binding protein, was identified as a transcription factor regulating steroidogenic P-450 genes in a cAMP-dependent manner. Immunochemical and immunohistochemical studies with steroidogenic tissues, adrenal, ovary, and testis, were performed using the antiserum to Ad4BP. Ad4BP was expressed to the same extent in the three zones of the adrenal cortex. Immunohistochemical examination of ovarian follicle and corpus luteum showed the expression of Ad4BP. The granulosa and thecal cells, the two distinct types of the steroidogenic cells in the follicle, gave Ad4BP signals, which were stronger than in the latter cells than in the former. Immunoblot analyses of mature and regressed corpora lutea indicated a parallel expression of Ad4BP and side-chain cleavage P-450, and both proteins significantly decreased in the regressed tissues. Leydig cells surrounding seminiferous tubules gave clear immunostaining signals for Ad4BP. ELP, a mammalian counterpart of Drosophila FTZ-F1 detected in EC cells, and are isoforms transcribed from the same gene. The Ad4BP and ELP forms recognize same nucleotide sequences. Reverse transcriptase-polymerase chain reaction with specific primers for ELP revealed that steroidogenic tissues contained ELP as well as Ad4BP. The effects of the two proteins on the transcription of the CYP11B gene were compared using the expression vectors of Ad4BP and ELP. ELP did not activate transcription and showed a weak inhibitor effect on the Ad4BP-dependent transactivation of the CYP11B gene promoter when transfected simultaneously. A gel shift analysis using in vitro synthesized Ad4BP and ELP revealed that the binding activity of ELP is significantly weaker than that of Ad4BP.
...
PMID:Functional difference between Ad4BP and ELP, and their distributions in steroidogenic tissues. 805 72

By using a mouse delta opioid receptor cDNA as a probe, a kappa opioid receptor gene was isolated from a human genomic library. Reverse transcriptase/PCR was subsequently used to isolate the corresponding cDNA from human placenta mRNA. Characterization of the cloned receptor with a kappa agonist in transfected COS-7 cells, revealed a Kd of 0.67 nM, which is similar to rodent kappa 1 receptors. In competition binding experiments, non-kappa agonists had kis > 1000nM. Furthermore, when expressed in COS-7 cells, the kappa receptor is negatively linked to cAMP. A Northern blot showed the presence of two transcripts, 6 and 7 kB in size, in both placenta and brain mRNA, which hybridized to the kappa cDNA.
...
PMID:Isolation of a human kappa opioid receptor cDNA from placenta. 806 Mar 24

Modulation of the three beta-adrenergic receptor subtypes (beta-ARs) by insulin was investigated in mouse 3T3-F442A adipocytes. Saturation and competition experiments measuring binding of 125I-labeled (-)-cyanopindolol to adipocyte membranes demonstrated that cell exposure to insulin for 4 days caused a 3.5-fold decrease in the density of the major beta-AR component of the adipocyte, the beta 3-AR, while beta 1-AR sites remained unchanged and beta 2-ARs were undetectable. This correlated with a lower potency of the beta 3-AR-selective agonists CGP12177, ICI201651, and BRL37344 in stimulating adenylate cyclase. Northern blotting analysis indicated that insulin induced a rapid and sharp decrease in beta 3-AR mRNA levels. This effect was detectable at low insulin concentrations (EC50 = 3 nM) and was not observed in the presence of insulin-like growth factor I, suggesting an insulin receptor-mediated phenomenon. Reverse transcriptase-PCR analysis showed that, in contrast to its dramatic down-regulatory effect on beta 3-AR mRNA, insulin did not modify the levels of beta 1- and beta 2-AR transcripts. As assessed by nuclear run-on assays, insulin inhibited the beta 3-AR gene transcription rate by 90% within 30 min. mRNA turnover experiments showed that the half-life of beta 3-AR mRNA was short (90 min) and remained unaffected by insulin. These findings demonstrate the genetic control of a beta-AR subtype expression by insulin and reveal a mechanism for the regulation by this hormone of cAMP-dependent biological processes in adipocytes.
...
PMID:Transcriptional down-regulation by insulin of the beta 3-adrenergic receptor expression in 3T3-F442A adipocytes: a mechanism for repressing the cAMP signaling pathway. 820 47

Na+ and Cl- conductances in the apical membrane of respiratory epithelial cells are essential for electrolyte and water transport in the airways. Apart from the well described defect in adenosine 3' : 5' cyclic monophosphate-(cAMP-) dependent activation of Cl- conductances in cystic fibrosis (CF), an increased Na+ conductance has also been reported from transepithelial measurements. In the present experiments we tried to identify these conductances in nasal epithelial cells using patch-clamp and microelectrode techniques. With these methods we found identical and relatively low membrane voltages of about -36 mV in both freshly isolated and primary cultured normal and CF nasal epithelial cells. A Cl- conductance could be activated by cAMP in normal (deltaG = 0.3 +/- 0.8 nS, n = 10) but not in CF (deltaG = 0.3 +/- 0.1 nS, n = 11) cells, whereas Ca2+-dependent Cl- currents activated by adenosine 5'-triphosphate (ATP) and bradykinin were present in both types of cells. Cell-attached membrane patches from stimulated cells did not reveal discernible single-channel events when activated with any of the agonists. A Na+ conductance was also detected in freshly isolated ciliated respiratory cells in impalement studies, as evidenced by the hyperpolarization induced by 10 micromol/l amiloride (deltaV = -5.2 +/- 0.6 mV, n = 56) and when Na+ was replaced in the bath by N-methyl-D-glucamine (NMDG) (deltaV = -5.7 +/- 0.9 mV, n = 14). In whole-cell patch-clamp experiments, the amiloride-induced hyperpolarization was significantly larger in CF (deltaV = 9.7 +/- 2.4 mV, n = 22) when compared to normal (deltaV = -3.3 +/- 0.9 mV, n = 27) cells in short-term culture. Reverse transcriptase polymerase chain reaction analysis of normal respiratory cells identified messenger RNA of both the cystic fibrosis transmembrane conductance regulator (CFTR) as well as the human epithelial Na+ channel (hNaCh). The present experiments confirm the absence of a cAMP-dependent Cl- conductance in CF respiratory epithelial cells and support previous findings obtained in transepithelial and microelectrode studies which indicate an increased Na+ conductance in respiratory epithelial cells from CF patients.
...
PMID:Na+ and Cl- conductances in airway epithelial cells: increased Na+ conductance in cystic fibrosis. 858 4

Previous studies from our laboratory have shown that messenger RNAs (mRNAs) coding for a cAMP-specific phosphodiesterase (PDE4A) are present in mature rat and mouse germ cells. However, no information is available about the properties of the expressed proteins. To determine their structure and regulation, the PDE4A isoforms expressed in the rat testis were identified and compared to the variants expressed in the brain. Western blot analysis using an antiserum specific for PDE4A demonstrated the presence in testis extracts of two distinct proteins with apparent masses of 98.8 and 86 kDa. The electrophoretic mobilities of these proteins differ from those of proteins detected in the brain extracts (113 and 76 kDa). Reverse transcriptase-PCR of the different splicing mRNA variants expressed in testis confirmed the presence of at least one novel PDE4A mRNA that is distinct from the PDE4A splicing variants identified in the brain and other tissues. Expression of the complementary DNA encoding this variant in a heterologous system resulted in an increase in PDE activity and the appearance of an immunoreactive protein with a mass of 98.8 kDa. No 86-kDa protein could be generated with this transfection. Upon fractionation of testis extracts by HPLC diethylaminoethyl-chromatography, a peak of cAMP-PDE activity coeluted with the two immunoreactive species. During testicular development, the 98.8-kDa protein is present in trace amounts at 10 days, and its level increases with the age of the animals, reaching a plateau at 40 days. The 86-kDa protein appears at 20 days of age and reaches its maximum at 40 days. Studies on the cellular site of expression demonstrated that the two polypeptides are most abundant in round spermatids and are expressed in trace amounts in pachytene spermatocytes, whereas they could not be detected in Sertoli or interstitial cells. The 98.8-kDa, but not the 86-kDa, protein was also expressed in epididymal spermatozoa. These data demonstrate the expression of novel cAMP-specific PDEs coded by the PDE4A gene. The expression of these isoforms is maximal in round spermatids and is maintained in mature spermatozoa. The genesis of the lower mol wt species remains to be determined.
...
PMID:Developmental regulation of unique adenosine 3',5'-monophosphate-specific phosphodiesterase variants during rat spermatogenesis. 864 Dec

Lipoprotein lipase (LPL), an enzyme which hydrolyzes triglycerides and participates in the catabolism of remnant lipoproteins, plays a crucial role in energy and lipid metabolism. The goal of this study was to analyze the expression and regulation of the LPL gene in human adrenals. Reverse transcriptase-polymerase chain reaction amplification and sequence analysis demonstrated the presence of LPL mRNA in fetal and adult human adrenal cortex. Furthermore, the human adrenocortical carcinoma cell line, NCI-H295, expresses LPL mRNA and protein, which is localized to the outer cellular membrane as demonstrated by immunofluorescence confocal microscopy and can be released in the medium by heparin addition. To asses whether the LPL gene is regulated by agents regulating adrenal steroidogenesis, NCI-H295 cells were treated with activators of second messenger systems. Whereas the calcium-ionophore A23187 did not affect LPL gene expression, treatment with phorbol 12-myristate 13-acetate decreased LPL mRNA levels in a time- and dose-dependent manner. This decrease after phorbol 12-myristate 13-acetate was associated with diminished heparin-releasable LPL mass and activity in the culture medium. Addition of the cAMP analog 8-Br-cAMP to NCI-H295 cells resulted in a rapid, but transient dose-dependent induction of LPL mRNA. Treatment with the protein synthesis inhibitor cycloheximide gradually induced, whereas simultaneous addition of cAMP and cycloheximide superinduced LPL mRNA levels. Nuclear run-on analysis indicated that the effects of cAMP and cycloheximide occurred at the transcriptional and post-transcriptional level, respectively. Transient co-transfection assays demonstrated that the first 230 base pairs of the proximal LPL promoter contain a cAMP-responsive element activated by protein kinase A and transcription factors belonging to the CREB/CREM family. These data indicate that LPL is expressed in human adrenal cortex and regulated in NCI-H295 adrenocortical carcinoma cells by activators of the protein kinase A and protein kinase C second messenger pathways in a manner comparable to P450scc, which catalyzes the first step in adrenal steroidogenesis. These observations suggest a role for LPL in adrenal energy and/or lipid metabolism and possibly in steroidogenesis.
...
PMID:Expression and regulation of the lipoprotein lipase gene in human adrenal cortex. 866 37

Muscarinic receptor subtypes in the bovine corneal epithelial cells (BCE) were characterized on the basis of their: 1) ligand binding properties, 2) linkage to Ca2+ and cAMP cell signaling pathways, and 3) gene transcripts. Receptor subtypes, m1 and m2, are indicated by competition experiments using subtype-selective muscarinic receptor ligands. [3H]N-methylscopolamine ([3H]-MS) binding was displaced with IC50s of: 1) 1 microM for the m1 antagonist, pirenzipine; 2) 51 microM for the competitive m2 antagonist, AFDX-116; 3) 100 microM for the competitive m3 antagonist, 4-DAMP. In fural2 loaded BCE, carbachol (0.001 - 100 microM) increased intracellular Ca2+ concentration ([Ca2+]i), and these responses were significantly suppressed if they were preincubated with either atropine (1 microM) or 1 microM pirenzipine. In the absence of extracellular Ca2+, these carbachol-induced increases in [Ca2+]i were depressed. A considerable fall occurred with the presence of extracellular Ca2+ and 1 microM verapamil, an L-type Ca2+ channel blocker. These responses suggest that carbachol increases Ca2+ influx through an L-type Ca2+ channel in the plasma membrane, in addition to mobilizing Ca2+ from an intracellular store. BCE also possessed muscarinic receptors which were negatively linked to cAMP production insofar as: 1) preincubation with 10 microM carbachol significantly suppressed the increases in cAMP accumulation induced by isoproterenol (1 - 25 microM); 2) this blunting effect of carbachol on cAMP production was eliminated when the BCE were preincubated with either 1 microM AFDX-116, or 100 ng/ml pertussis toxin. The results of probing for muscarinic receptor gene expression are partially consistent with the ligand binding and functional assays. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the presence of m2 but not m1, m3 or m4 gene transcripts. In summary, we obtained pharmacological and functional evidence for m1 and m2 receptors in BCE. However, only the m2 gene transcript could be detected.
...
PMID:Characterization of the muscarinic receptor subtypes in the bovine corneal epithelial cells. 887 32

The gene encoding surfactant protein A (SP-A) is expressed in type II pneumonocytes and is developmentally and hormonally regulated in fetal lung tissue. SP-A is encoded by a single-copy gene in rabbits, dogs, rats, and mice. By contrast, the human genome contains two similar genes, hSP-A1 and hSP-A2, which are differentially regulated during development and differentially regulated by adenosine 3',5'-cyclic monophosphate (cAMP) and glucocorticoid treatment of human fetal lung in culture. In the present study, we have isolated and characterized baboon genomic clones containing two highly similar SP-A genes. Restriction mapping of these clones, together with Southern analysis of genomic DNA, indicates that these comprise two distinct baboon SP-A genes. Sequence comparison of DNA upstream of the transcription initiation sites and within the 3'-untranslated regions encoded by exon VI indicates that one of the baboon SP-A genes (bSP-A1) is more similar to hSP-A1, whereas the other (bSP-A2) is more similar to hSP-A2. Primer extension analysis of baboon lung mRNA indicates that both baboon SP-A genes utilize conserved transcription initiation sites. Reverse transcriptase-polymerase chain reaction analysis of RNA isolated from lung tissues of fetal baboons of 160 days gestational age indicates that both bSP-A1 and bSP-A2 are expressed in baboon fetal lung and that mRNA transcripts of bSP-A1 and bSP-A2 genes are primarily comprised of sequences encoded by exons I and III-VI. However, minor transcripts of the bSP-A1 gene containing exon II and exon II plus an extension also were detected. The presence of two SP-A genes in the baboon suggests that duplication of the SP-A gene occurred > 26.5 million years ago, before divergence of the baboon lineage from the man-gorilla-chimpanzee clade.
...
PMID:Characterization of two baboon surfactant protein A genes. 889 10

Exposure of rat brown adipocytes differentiated in culture to norepinephrine (NE) results in the production of nitrites (NO2-), the breakdown product of nitric oxide (NO). This production, which is blocked by actinomycin D1 is directly related to the duration of exposure to and dose of NE. Cytosol from NE-treated brown fat cells, but not from untreated cultures, catalyzed the Ca(2+)-independent conversion of L-arginine to L-citrulline, which could be significantly blocked by the specific nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester. Reverse transcriptase-PCR demonstrates that the addition of NE; selective beta 1-, beta 2-, or beta 3-adrenergic receptor agonists; or agents increasing cAMP production, such as forskolin, to brown adipocytes stimulates inducible NOS (iNOS) messenger RNA, which is present within 4 h after exposure. That iNOS is synthesized in brown fat cells is confirmed by immunoblotting using an antibody to the iNOS of mouse macrophages, Finally, in both brown adipose tissue (BAT) and brown adipocyte preparations from animals exposed to low temperature, iNOS messenger RNA and protein were expressed, and NOS activity was detectable; these findings were unlikely for room temperature-acclimated rats. We conclude that brown fat cells can express an inducible form of NOS similar to the iNOS of macrophages, and that its production is directly dependent on sympathetic activity in physiological conditions. NO generated by stimulation of iNOS in brown adipocytes may represent an important mechanism to modulate different BAT functions, among which is vasodilation of the BAT microcirculation.
...
PMID:Inducible nitric oxide synthase in rat brown adipocytes: implications for blood flow to brown adipose tissue. 900 2


<< Previous 1 2 3 4 5 6 7 Next >>

---