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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of aquaporins (AQP) and water permeability were studied in Xenopus laevis oocytes and immobilized glial cells by a pulsed-field gradient spin echo NMR technique and a photometric swelling assay. Oocytes injected with poly(A) RNA from C6-BU-1 cells showed increased swelling behavior under hypoosmotic stress due to expressed water channels as compared to control oocytes. The swelling could be reversibly inhibited by HgCl2. Furthermore, the intracellular relaxation time and the apparent intracellular diffusion coefficient of water in oocytes were determined by diffusion-weighted 1H NMR experiments to be T2=36 ms and Dapp, intra=0.18x10-3 mm2/s. In immobilized C6 and F98 cells the mean exchange time of intracellular water was found to be 51 ms which increased to 75 ms upon chronic treatment (4 days) in hypertonic medium. Additional hybrid depletion experiments with antisense oligonucleotides directed against AQP1 were performed on oocytes and C6 cells. Moreover, different water channel subtypes of glial cells were assessed by a reverse transcriptase polymerase chain reaction assay. With this, the mRNA encoding AQP1 could be detected in primary cultures and glial cell lines, whereas AQP4 mRNA was found in astroglia-rich primary cultures, but not in F98 and C6 cells. Our results show that water permeability in glial cells is mainly mediated by water channels which play an important role in the regulation of water flow in brain under normal and pathological conditions.
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PMID:Expression of aquaporins in Xenopus laevis oocytes and glial cells as detected by diffusion-weighted 1H NMR spectroscopy and photometric swelling assay. 982 61

The water channel aquaporin 4 (AQP4) is abundantly expressed in the brain, and also in lung and kidney. Previous studies have suggested that there are at least two AQP4 mRNA. The two mRNA encode for two AQP4 proteins that differ with regard to the length of the N-terminal: AQP4.M1 and AQP4.M23. Here we report, by use of reverse transcriptase PCR and comparison of genomic and cDNA structures, the presence of a third form of mouse AQP4 mRNA. The upstream sequence of this form of mRNA originates from an additional exon, interspaced between exon 0 and exon 1, and an alternatively spliced form of exon 1. Analysis of nucleotide sequence suggests that this new form of AQP4 mRNA also encodes for the AQP4.M23 protein. The two forms of AQP4 mRNA that presumably both encode for M23 have a tissue- and age-specific expression. The new AQP4 mRNA was predominantly expressed in brain. The expression was approximately twofold higher in the adult brain than in the infant brain. In contrast, the expression levels of the new mRNA were low in both infant and adult lung and kidney. The previously described mRNA encoding for AQP4.M23 was predominantly expressed in lung and kidney. In lung, the expression of this form was higher in infancy than in adulthood. In conclusion, we have identified a new form of AQP4 mRNA that is predominantly expressed in the brain and that is developmentally regulated.
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PMID:Identification of a new form of AQP4 mRNA that is developmentally expressed in mouse brain. 1096 Apr 99

Aquaporins (AQPs), membrane-inserted water channel proteins, play a highly important role in the reabsorption of water from the renal tubular fluid. Experimentally, both in rats and mice, failure to insert functional AQP molecules into renal tubular membranes leads to nephrogenic diabetes insipidus. In humans, most forms of renal disease lead to a reduction in the water handling capacity of the kidney. AQP distribution in various forms of human renal disease has not been documented. Immunohistochemical studies of biopsy samples from a wide range of renal diseases revealed a substantial and striking upregulation of AQP-1 in the glomeruli of most diseased kidneys. AQP-1 expression remained prominent in proximal tubules in all lesions. In contrast, there was judged qualitatively to be a reduction in the amounts of AQP-2 and AQP-3 expression, especially in lesions with substantial interstitial fibrosis and nephron loss, as compared with a healthy region of normal kidneys. The results were quantitatively confirmed by real-time reverse transcriptase-PCR. This is the first documentation of altered AQP expression in human renal disease. The significance of the increased AQP-1 expression requires further studies.
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PMID:Aquaporin expression in normal human kidney and in renal disease. 1451 35

Aquaporins (AQPs) are a family of water channel proteins that assist in maintenance of the cellular osmotic environment and whole body fluid balance. Specialized organ-specific AQPs are important in physiologic and pathologic processes but little is known about AQPs in the human heart. AQP1 has been identified in rodent heart. We investigated the presence and localization of AQP1 in human heart and skeletal muscle using immunohistochemistry and confocal microscopy, western blot and reverse transcriptase-polymerase chain reaction. There was abundant AQP1 present in both cardiac and skeletal muscle. Immunohistochemistry revealed co-localization of AQP1 with vinculin, a t-tubule marker, and caveolin-3. No novel sequences bearing an NPA box motif common to other AQPs were identified in human heart using degenerative PCR analysis. We conclude that AQP1 is present in the human heart. AQP1 co-localizes with t-tubular and caveolar proteins. Cardiac AQPs may have a role during osmotic stresses including ischemia/reperfusion and cardiopulmonary bypass.
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PMID:Expression of aquaporin 1 in human cardiac and skeletal muscle. 1513 60

Aquaporin 9 (AQP9) is a recently cloned water channel that is permeable to monocarboxylate, glycerol and urea. In rat, AQP9 has been found in testis and liver as well as in brain where its expression has been initially shown in glial cells in forebrain. However, the expression of AQP9 has not been investigated in the brainstem. The purpose of this study is to describe the distribution of AQP9-immunoreactive cells throughout the adult rat brain using reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot and immunohistochemistry. We performed immunolabeling on brain from animals perfused with fixative and we show that AQP9 is expressed (i) in astrocytes in the glia limitans, in the white matter and in glial cells of the cerebellum, (ii) in the endothelial cells of pial vessels, and (iii) in specific groups of neurons. The neuronal AQP9 expression was almost exclusively observed in catecholaminergic cells including the adrenergic, noradrenergic and dopaminergic groups, but not in other monoaminergic neurons such as serotonergic or histaminergic cells. A slight labeling was also observed in non-catecholaminergic neurons localized in the paraventricular nucleus of the hypothalamus. These results indicate that AQP9 has a unique brain distribution with a preferential localization in catecholaminergic nuclei known to be involved in many cerebral functions. While the presence of AQP9 in glia limitans and in endothelial cells of the pial vessels could be related to water transport through the blood-brain barrier, its expression in neuronal cells, not directly involved in the osmoregulation, suggests that brain AQP9 could also be used as a metabolite channel since lactate and glycerol can be energy substrates for neurons.
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PMID:Distribution of Aquaporin 9 in the adult rat brain: preferential expression in catecholaminergic neurons and in glial cells. 1545 Mar 51

The water channel aquaporin-1 (AQP1) is considered as the molecular counterpart of the ultrasmall pore predicted by the three-pore model of fluid transport across the peritoneal membrane. However, the definitive proof of the implication of AQP1 in solute-free water transport, sodium sieving, and ultrafiltration (UF) during peritoneal dialysis (PD) is lacking, and the effects of its deletion on the structure of the membrane are unknown. Using real-time reverse transcriptase-polymerase chain reaction and immunogold electron microscopy, we showed that AQP1 is the most abundant member of the AQP gene family expressed in the mouse peritoneum, and the only one located in the capillary endothelium. Transport studies during a 2-h dwell demonstrated that, in comparison with Aqp1(+/+) littermates, Aqp1(-/-) mice had no sodium sieving; an approximately 70% decrease in the initial, solute-free UF; and an approximately 50% decrease in cumulative UF. These modifications occurred despite unchanged osmotic gradient and transport of small solutes in the Aqp1(-/-) mice. Heterozygous Aqp1(+/-) mice showed intermediate values in sodium sieving and initial UF, whereas cumulative UF was similar to Aqp1(+/+) mice. The deletion of AQP1 had no effect on the expression of other AQPs and on the density, structure, or diameter of peritoneal capillaries. These data provide direct evidence for the role of AQP1 during PD. They validate essential predictions of the three-pore model: (i) the ultrasmall pores account for the sodium sieving, and (ii) they mediate 50% of UF during a hypertonic dwell.
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PMID:Aquaporin-1 plays an essential role in water permeability and ultrafiltration during peritoneal dialysis. 1705 Dec 65

The aquaporins represent a family of transmembrane water channel proteins that play a major role in trans-cellular and transepithelial water movement. Most tumors have been shown to exhibit high vascular permeability and interstitial fluid pressure, but the transport pathways for water within tumors remain unknown. Here, we tested 10 non-small cell lung cancer cell lines of various origins by reverse transcriptase-polymerase chain reaction and Western blot analysis and identified clear expression of aquaporin 1 (AQP1) in seven cell lines. We next examined the distribution of the AQP1 protein in several types of primary lung tumors (16 squamous cell carcinomas, 21 adenocarcinomas, and 7 bronchoalveolar carcinomas) by immunohistochemical staining. AQP1 was overexpressed in 62% (13 of 21) and 75% (6 of 8) of adenocarcinoma and bronchoalveolar carcinoma, respectively, whereas all cases of squamous cell carcinoma and normal lung tissue were negative. Forced expression of full-length AQP1 cDNA in NIH-3T3 cells induced many phenotypic changes characteristic of transformation, including cell proliferation-enhancing activity by the MTT assay and anchorage-independent growth in soft agar. Although further details on the molecular function of AQP1 related to tumorigenesis remain to be elucidated, our results suggest a potential role of AQP1 as a novel therapeutic target for the management of lung cancer.
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PMID:Aquaporin 1 is overexpressed in lung cancer and stimulates NIH-3T3 cell proliferation and anchorage-independent growth. 2290 56

Polycystic kidney (PCK) rats are a spontaneous model of autosomal recessive polycystic kidney disease that exhibit cholangiocyte-derived liver cysts. We have previously reported that in normal cholangiocytes a subset of vesicles contain three proteins (ie, the water channel AQP1, the chloride channel CFTR, and the anion exchanger AE2) that account for ion-driven water transport. Thus, we hypothesized that altered expression and location of these functionally related proteins contribute to hepatic cystogenesis. We show here that under basal conditions and in response to secretin and hypotonicity, cysts from PCK rats expanded to a greater degree than cysts formed by normal bile ducts. Quantitative reverse transcriptase-polymerase chain reaction, immunoblot analysis, and confocal and immunoelectron microscopy all indicated increased expression of these three proteins in PCK cholangiocytes versus normal cholangiocytes. AQP1, CFTR, and AE2 were localized preferentially to the apical membrane in normal rats while overexpressed at the basolateral membrane in PCK rats. Exposure of the cholangiocyte basolateral membrane to CFTR inhibitors [5-nitro-2-(3-phenylpropylamino)-benzoic acid and CFTRinh172], or Cl(-)/HCO(3)(-) exchange inhibitors (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate and 4-acetamido-4'-isothiocyanato-2,2'-stilbenedisulfonic acid disodium salt hydrate) blocked secretin-stimulated fluid accumulation in PCK but not in normal cysts. Our data suggest that hepatic cystogenesis in autosomal recessive polycystic kidney disease may involve increased fluid accumulation because of overexpression and abnormal location of AQP1, CFTR, and AE2 in cystic cholangiocytes. Therapeutic interventions that block the activation of these proteins might inhibit cyst expansion in polycystic liver disease.
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PMID:Hepatic cystogenesis is associated with abnormal expression and location of ion transporters and water channels in an animal model of autosomal recessive polycystic kidney disease. 1898 97

Birds and mammals are the only vertebrates that can concentrate urine. Avian kidneys contain structurally primitive loopless nephrons and also more advanced looped nephrons, in the cortical and medullary regions, respectively. We have identified the gene sequence of an aquaporin 2 (AQP2)-homologue water channel in collecting ducts of kidneys from adult quail, Coturnix japonica. Although immunoreactive quail AQP2 (qAQP2) was found in both types of nephrons, the expression is enhanced more clearly in the medullary regions after water deprivation. We therefore hypothesized that regulation of qAQP2 expression in quail kidneys via antidiuretic hormone (ADH) may require more advanced nephron structure. In this study, we determined the expression of qAQP2 mRNA in tissues isolated from the cortical and medullary regions before and after water deprivation, by conventional reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative real-time PCR. In both normally hydrated and water-deprived groups, qAQP2 mRNA levels in the medullary regions were significantly higher (P<0.01) than in the cortical regions. In medullary areas, qAQP2 mRNA levels (real-time PCR normalized with 18S) were significantly higher (P<0.01, ANOVA) after water deprivation (1.09+/-0.10) than in normally hydrated controls (0.46+/-0.08). In cortical areas, qAQP2 mRNA levels were also higher after water deprivation (0.37+/-0.05) than in controls (0.11+/-0.02). qAQP2 mRNA signals determined by in situ hybridization of digoxigenin-labeled riboprobe were also enhanced after water deprivation in both cortical and medullary collecting ducts. The results suggest that, contrary to our hypothesis, the endogenous production of ADH by water deprivation stimulates qAQP2 mRNA in both loopless and looped nephrons.
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PMID:Control of aquaporin 2 expression in collecting ducts of quail kidneys. 1913 43

This paper investigates differences in gene expression among the two Thlaspi caerulescens ecotypes La Calamine (LC) and Lellingen (LE) that have been shown to differ in metal tolerance and metal uptake. LC originates from a metalliferous soil and tolerates higher metal concentrations than LE which originates from a non-metalliferous soil. The two ecotypes were treated with different levels of zinc in solution culture, and differences in gene expression were assessed through application of a cDNA microarray consisting of 1,700 root and 2,700 shoot cDNAs. Hybridisation of root and shoot cDNA from the two ecotypes revealed a total of 257 differentially expressed genes. The regulation of selected genes was verified by quantitative reverse transcriptase polymerase chain reaction. Comparison of the expression profiles of the two ecotypes suggests that LC has a higher capacity to cope with reactive oxygen species and to avoid the formation of peroxynitrite. Furthermore, increased transcripts for the genes encoding for water channel proteins could explain the higher Zn tolerance of LC compared to LE. The higher Zn tolerance of LC was reflected by a lower expression of the genes involved in disease and defence mechanisms. The results of this study provide a valuable set of data that may help to improve our understanding of the mechanisms employed by plants to tolerate toxic concentrations of metal in the soil.
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PMID:Comparison of two ecotypes of the metal hyperaccumulator Thlaspi caerulescens (J. & C. PRESL) at the transcriptional level. 1993 57


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