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

Immune complexes are thought to be the major cause of cutaneous necrotizing vasculitis, but the mechanism of immune complex targeting to specific vessels is largely unknown. In myelomonocytic cells, immune complex binding and receptor-mediated endocytosis are mediated by Fc gamma R. We asked whether dermal microvascular endothelial cells (DMEC) express Fc gamma Rs. In cryostat sections of normal human skin, mAb IV.3 or AT10, both recognizing CD32 (Fc gamma RII), localizes to the luminal surface of DMEC of the superficial but not of the deep vascular plexus. All DMEC do not express CD16 (Fc gamma RIII) or CD64 (Fc gamma RI) molecules. Adult skin-derived DMEC in culture express CD32 (Fc gamma RII) molecules, as measured by FACS, but are negative for CD16 or CD64. HUVEC, tested for comparison, do not express CD16, 32, or 64 proteins. By reverse-transcriptase PCR and subsequent Southern blot analysis, the isoform of the CD32 molecule expressed on DMEC is determined as Fc gamma RIIa. HUVEC do not contain Fc gamma RIIa or Fc gamma RIIb mRNA. In DMEC, Fc gamma RIIa cross-linking results in immediate intracellular free Ca2+ ([Ca2+]i) concentration fluxes and in rapid internalization of the occupied receptors. We conclude that DMEC are equipped with fully functional Fc gamma RIIa molecules.
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PMID:Dermal microvascular endothelial cells express CD32 receptors in vivo and in vitro. 856 59

Troponin T, which links the troponin complex to tropomyosin, is found as multiple isoforms in the hearts of many animal species. Changes in isoform composition have been correlated with variation in myofilament sensitivity to calcium. In order to determine the origin of diversity of the cardiac troponin T (cTnT) isoforms indicated by existing protein data, we have determined the sequences and patterns of expression of mRNAs encoding troponin T in fetal and adult heart and those present in adult heart in end-stage failure. Three main regions of alternative splicing within the cTnT coding region were identified using reverse-transcriptase polymerase chain reaction (RT-PCR). Alternatively spliced RNAs are developmentally regulated and some of the fetal forms are expressed in adult failing heart. The molecular structure of the spliced regions was determined from cloned cDNAs and RT-PCR products. In the 5' region of the mRNA, isoforms are generated by the inclusion or exclusion of 15-, 3- and 27-nucleotide (nt) sequences and by the inclusion or exclusion of a separate 3-nt sequence. In the 3' region of the mRNA, alternative splicing involves a 9-nt sequence which can be present in full, in part or not at all. A further splicing site was identified in the central region involving a 234-nt sequence and resulting in rare but detectable mRNAs. This work demonstrates the complexity of cTnT RNA composition in human heart and provides the information necessary to address the function of cTnT isoforms in contraction.
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PMID:Molecular cloning of human cardiac troponin T isoforms: expression in developing and failing heart. 857 38

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.
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PMID:Na+ and Cl- conductances in airway epithelial cells: increased Na+ conductance in cystic fibrosis. 858 4

In neutrophils, binding and phagocytosis facilitate subsequent intracellular killing of microorganisms. Activity of Na+/H+ exchangers (NHEs) participates in these events, especially in regulation of intracellular pH (pHi) by compensating for the H+ load generated by the respiratory burst. Despite the importance of these functions, comparatively little is known regarding the nature and regulation of NHE(s) in neutrophils. The purpose of this study was to identify which NHE(s) are expressed in neutrophils and to elucidate the mechanisms regulating their activity during phagocytosis. Exposure of cells to the phagocytic stimulus opsonized zymosan (OpZ) induced a transient cytosolic acidification followed by a prolonged alkalinization. The latter was inhibited in Na+-free medium and by amiloride analogues and therefore was due to activation of Na+/H+ exchange. Reverse transcriptase PCR and cDNA sequencing demonstrated that mRNA for the NHE-1 but not for NHE-2, 3, or 4 isoforms of the exchanger was expressed. Immunoblotting of purified plasma membranes with isoform-specific antibodies confirmed the presence of NHE-1 protein in neutrophils. Since phagocytosis involves Fcgamma (FcgammaR) and complement receptors such as CR3 (a beta2 integrin) which are linked to pathways involving alterations in intracellular [Ca2+]i and tyrosine phosphorylation, we studied these pathways in relation to activation of NHE-1. Cross-linking of surface bound antibodies (mAb) directed against FcgammaRs (FcgammaRII > FcgammaRIII) but not beta2 integrins induced an amiloride-sensitive cytosolic alkalinization. However, anti-beta2 integrin mAb diminished OpZ-induced alkalinization suggesting that NHE-1 activation involved cooperation between integrins and FcgammaRs. The tyrosine kinase inhibitors genistein and herbimycin blocked cytosolic alkalinization after OpZ or FcgammaR cross-linking suggesting that tyrosine phosphorylation was involved in NHE-I activation. An increase in [Ca2+]i was not required for NHE-1 activation because neither removal of extracellular Ca2+ nor buffering of changes in [Ca2+]i inhibited alkalinization after OpZ or Fc-gammaR cross-linking. In summary, Fc-gammaRs and beta2 integrins cooperate in activation of NHE-1 in neutrophils during phagocytosis by a signaling pathway involving tyrosine phosphorylation.
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PMID:Na+/H+ exchange activity during phagocytosis in human neutrophils: role of Fcgamma receptors and tyrosine kinases. 860 83

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

Mesotocin is the oxytocin-like hormone found in most terrestrial vertebrates from lungfishes to marsupials, which includes all non-mammalian tetrapods (amphibians, reptiles, and birds). It has the largest distribution in vertebrates after vasotocin found in all non-mammalian vertebrates and isotocin identified in bony fishes. In this study, we report the cloning and functional characterization of the cDNA for the mesotocin receptor (MTR) from the urinary bladder of the toad Bufo marinus. The cloned cDNA encodes a polypeptide of 389 amino acids that shows the greatest similarity to the teleost fish isotocin receptor and to mammalian oxytocin receptors with mutations in extracellular loops which are involved in ligand binding. When expressed in COSM6 cells, MTR exhibits the following relative order of ligand affinity: mesotocin > vasotocin = oxytocin > vasopressin > hydrin 1, isotocin, hydrin 2. Injection of MTR cRNA into Xenopus laevis oocytes induces membrane chloride currents in response to mesotocin, which indicates the coupling of the mesotocin receptor to the inositol phosphate/calcium pathway. This response is inhibited by an oxytocin antagonist, but not by a vasopressin antagonist specific for V2 vasopressin receptors. MTR mRNA is not only found in toad urinary bladder, but also in kidney, muscle, and brain tissue of the toad as revealed by northern blot analysis and reverse-transcriptase PCR. The results suggest a variety of function for mesotocin and its receptor including, in particular, an involvement in the regulation of water and salt transport.
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PMID:Cloning and functional characterization of the amphibian mesotocin receptor, a member of the oxytocin/vasopressin receptor superfamily. 864 23

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.
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PMID:Expression and regulation of the lipoprotein lipase gene in human adrenal cortex. 866 37

1. The biological activities of the proteinase-activated receptor number 2 (PAR-2)-derived peptides, SLIGRL (PP6) SLIGRL-NH2 (PP6-NH2) and SLIGR-NH2 (PP5-NH2) were measured in mouse and rat gastric longitudinal muscle (LM) tissue and in a rat aortic ring preparation and the actions of the PAR-2-derived peptides were compared with trypsin and with the actions of the thrombin receptor activating peptide, SFLLR-NH2 (TP5-NH2). 2. From a neonatal rat intestinal cDNA library, and from intestinal and kidney-derived cDNA, the coding region of the rat PAR-2 receptor was cloned and sequenced, thereby establishing its close sequence identity with the previously described mouse PAR-2 receptor; and this information, along with a reverse-transcriptase (RT) polymerase chain reaction (PCR) analysis of cDNA derived from gastric and aortic tissue was used to establish the concurrent presence of PAR-2 and thrombin receptor mRNA in both tissues. 3. In the mouse and rat gastric preparations, the PAR-2-derived polypeptides, PP6, PP6-HN2 and PP5-NH2 caused contractile responses that mimicked the contractile actions of low concentrations of trypsin (5 u/ml-1; 10 nM) and that were equivalent to contractions caused by TP5-NH2. 4. The cumulative exposure of the rat LM tissue to PP6-NH2 led to a desensitization of the contractile response to this polypeptide, but not to TP5-NH2 and vice versa, so as to indicate a lack of cross-desensitization between the receptors responsive to the PAR-2 and thrombin receptor-derived peptides. 5. In the rat gastric preparation, the potencies of the PAR-2-activating peptides were lower than the potency of TP5-NH2 (potency order: TP5-NH2 > > PP6-NH2 > or = PP6 > PP5-NH2); PP6 was a partial agonist in this preparation. 6. The contractile actions of PP6 and PP6-NH2 in the rat gastric preparation required the presence of extracellular calcium, were inhibited by nifedipine and were blocked by the cyclo-oxygenase inhibitor, indomethacin and by the tyrosine kinase inhibitor, genistein, but not by the kinase C inhibitor, GF109203X. The contractile responses were not blocked by atropine, chlorpheniramine, phenoxybenzamine, propranolol, ritanserin or tetrodotoxin. 7. In a precontracted rat aortic ring preparation, with an intact endothelium, all of the PAR-2-derived peptides caused a prompt relaxation response that was blocked by the nitric oxide synthase inhibitor, N omega-nitro-L-arginine-methyl ester (L-NAME) but not by D-NAME; in an endothelium-free preparation, which possessed mRNA for both the PAR-2 and thrombin receptors, the PAR-2-activating peptides caused neither a relaxation nor a contraction, in contrast with the contractile action of TP5-NH2. The relaxation response to PP6-NH2 was not blocked by atropine, chlorpheniramine, genistein, indomethacin, propranolol or ritanserin. 8. In the rat aortic preparation, the potencies of PP6, PP6-NH2 and PP5-NH2 were greater than those of the thrombin receptor activating peptide, TP5-NH2 (potency order: PP6-NH2 > or = PP6 > PP5-NH2 > TP5-NH2). 9. In the rat aortic preparation, the relaxant actions of the PAR-2-derived peptides were mimicked by trypsin, at concentrations (0.5-1 u ml-1; 1-2 nM) lower than those that can activate the thrombin receptor. 10. The bioassay data obtained with the PAR-2 peptides and with trypsin, along with the molecular cloning/RT-PCR analysis, point to the presence of functional PAR-2 receptors that can activate distinct responses in the gastric and vascular smooth muscle preparations. These responses were comparable to those resulting from thrombin receptor activation in the same tissues, so as to suggest that the receptor for the PAR-2-activating peptides may play a physiological role as far reaching as the one proposed for the thrombin receptor.
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PMID:Rat proteinase-activated receptor-2 (PAR-2): cDNA sequence and activity of receptor-derived peptides in gastric and vascular tissue. 876 73

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.
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PMID:Characterization of the muscarinic receptor subtypes in the bovine corneal epithelial cells. 887 32

The overall goal of this study was to provide data on the function and physiologic significance of lens calpain I, a cysteine protease requiring low amounts of calcium for activation. Reverse-transcriptase polymerase chain reaction was used to detect mRNAs for calpains I and II in young rat lenses. An in vitro model of crystallin precipitation was used to assess the ability of calpain I to induce hydrolysis and precipitation of crystallins. We found that incubation of crystallins with purified calpain I was indeed a powerful inducer of crystallin precipitation. However, mRNA levels for calpain I in whole lens appeared to be lower compared to calpain-II mRNA. Participation of calpain I in crystallin precipitation during normal maturation of rodent lenses or cataract formation is thus theoretically possible, but unlikely, because of the low level of expression of calpain I.
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PMID:In vitro precipitation of rat lens crystallins by calpain I--a calpain requiring low amounts of calcium for activation. 888 97


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