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)

1. We have investigated the identity of the L-type Ca2+ channels present in the H9c2 myoblast line derived from embryonic rat ventricle. To this end, we characterized macroscopic and unitary Ba2+ currents through Ca2+ channels, and looked for specific genetic messages encoding different L-type Ca2+ channel isoforms. 2. The macroscopic Ba2+ current (recorded in 10 mM BaCl2) revealed two components with different time courses of activation. The fast component (IBa,fast) activates with a time constant of 23 +/- 12 ms (at +10 mV), while the slow component activates with a time constant of 125 +/- 12 ms (at +10 mV). 3. Single-channel recordings revealed the presence of two independent channels with conductance values of 11 and 25 pS (in 70 mM Ba2+). These values are identical to those reported previously for skeletal muscle and cardiac Ca2+ channels, respectively. 4. The mean ensemble current from the 11 pS channel reproduced the time course of the slow component observed at the macroscopic level, while the 25 pS ensemble time course paralleled that of the fast component. 5. Reverse transcriptase polymerase chain reaction (PCR) with alpha 1-isoform-specific primers revealed the presence of two distinct transcripts in H9c2 cells. The sequences of the PCR products showed a high degree of homology with the corresponding segments of the rabbit cardiac and skeletal muscle L-type Ca2+ channel isoforms. Adult rat skeletal and cardiac muscle expressed only one type of transcript. 6. H9c2 cells appear to be unique in that they simultaneously express both skeletal muscle and cardiac isoforms of the L-type Ca2+ channel alpha 1-subunit. Thus, the H9c2 cell line may prove to be useful when studying the regulation of subtype-specific Ca2+ channel gene expression.
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PMID:Simultaneous expression of cardiac and skeletal muscle isoforms of the L-type Ca2+ channel in a rat heart muscle cell line. 752 45

There is increasing evidence that the membrane-bound thyrotropin receptor (TSHR) may be mediating clinically important direct effects of thyrotropin (TSH) and of TSHR antibodies (TSHRab) in extra-thyroidal tissues. TSHR mRNA has formerly been detected in thyroid, retroorbital muscle and fibroblasts, peripheral lymphocytes and rodent fat. It is well known that thyroid disease may aggravate or induce heart disease, but the pathophysiological role of TSH and TSHRab is not clear. The aim of this study was to investigate if TSHR is present in cardiac muscle. Reverse transcriptase polymerase chain reactions revealed TSHR in human heart and Northern blot on extracted RNA showed a RNA species of 4.4 kb. TSH stimulation of cultured mouse AT-1 cardiomyocytes elevated the levels of intracellular second messenger 3',5'-cyclic AMP. This effect of TSH could be inhibited by TSHR antibodies. In solution hybridization levels of TSHR mRNA in AT-1 cells were 50% of mRNA in crude mouse heart. In conclusion functional TSHR is present in cardiomyocytes.
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PMID:Evidence for the presence of functional thyrotropin receptor in cardiac muscle. 779 53

This study was designed to quantitate cardiac mRNA levels encoding components of the local renin-angiotensin system during the development of volume overload-induced cardiac hypertrophy. Changes in cardiac renin mRNA levels were measured in relation to renin activity in the left ventricle (LV) and in plasma after acute passive stretch of the heart caused by an aortovenocaval shunt in the rat. A quantitative reverse-transcriptase polymerase chain reaction method with competitive internal standards was used to measure mRNA levels in total RNA derived from cardiac tissues after shunt. Seven days after shunt surgery, LV weight was increased by 23%. Renin activities were elevated four- and twofold in plasma and LV, respectively. LV angiotensinogen mRNAs were not significantly increased by shunt surgery; they were twofold higher than phosphoglycerate kinase mRNA from the housekeeping gene PGK-1. By day 7, LV levels for renin mRNA were significantly increased from well below 0.25% to approximately 1% of PGK-1 mRNA. Identity between renin polymerase chain reaction products from kidney and heart cDNAs and absence of "reninlike" amplification products were supported by Southern blotting. Volume overload caused increased expression of the renin gene in the stretched myocardium. This finding is consistent with the concept of a myocardial renin-angiotensin system that can be activated by locally produced renin and contributes to the hypertrophy of cardiac muscle.
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PMID:Stretch-mediated activation of cardiac renin gene. 794 10

Examination of cDNAs for the laminin-binding alpha 7 integrin subunit identified two different sequences (designated X1 and X2) coding for the variable region between the III and IV homology repeat domains near the putative ligand-binding site. Sequencing of a mouse alpha 7 genomic clone established that the X1 and X2 regions are derived by mutually exclusive alternative mRNA splicing. Reverse transcriptase-polymerase chain reaction analysis of alpha 7 mRNA indicated that the X1 and X2 isoforms were present in equal amounts in mouse skeletal myoblasts and adult heart. However, in adult skeletal muscle, the X2 variant was exclusively expressed. Amino acid sequence homologies in the III/IV segment suggest that alpha 3 and alpha 6 are also alternatively spliced at this site. We identified alternatively spliced exons in a human alpha 6 genomic clone that encode X1- and X2-like segments. Analysis of the alpha 7 cytoplasmic domain indicated that this region was also alternatively spliced and like alpha 3 and alpha 6 could exist as the A or B form. In mouse skeletal and cardiac muscle the B form of alpha 7 was strongly expressed. However, we identified alpha 7A in neonate and adult skeletal muscle but not in cardiac tissue. High levels of alpha 7A were detected in differentiating myotubes, but in proliferating myoblasts only the alpha 7B isoform was present. These results indicate that alternative splicing of alpha 7 mRNA is differentially regulated during development and generates variant integrin chains with structurally and presumably functionally unique ligand-binding and cytoplasmic domains.
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PMID:Alternative extracellular and cytoplasmic domains of the integrin alpha 7 subunit are differentially expressed during development. 825 14

Four different plasma membrane Ca(2+)-ATPase (PMCA) genes and three sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) genes have been previously cloned and characterized. In this study we have investigated the expression of the mRNA encoding the various PMCA and SERCA proteins in fetal and adult human heart and placenta by the reverse-transcriptase-polymerase-chain-reaction (RT-PCR) and cDNA cloning. We have found that PMCA1 and PMCA4 genes were expressed in 8-, 12- and 20-week fetal heart and in adult heart. PMCA2 gene was expressed at low levels in adult heart but was not detected in fetal heart. PMCA3 mRNA was not detected in the heart nor placenta. In contrast, the mRNA encoding SERCA2a, SERCA2b and SERCA3 were expressed in all cardiac developmental stages. Multiple alternatively spliced mRNA transcripts which differ at splice site A and B/C of the PMCA1, PMCA2 and PMCA4 genes were detected in the human heart. Interestingly, a novel tissue specific variant of the PMCA4 gene was detected in both fetal and adult human heart but not in placenta that accounts for about 30% of the total PMCA4 mRNA variant expression. DNA sequence analysis of this novel variant revealed that it corresponds to the equivalent of the PMCA1d variant and accordingly we have named it PMCA4d. We cloned and sequenced eight cDNA inserts encoding for the PMCA1 and PMCA4 variants from a fetal human heart cDNA library confirming that these are the two main PMCA genes expressed in cardiac muscle.
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PMID:Analysis of mRNA expression and cloning of a novel plasma membrane Ca(2+)-ATPase splice variant in human heart. 870 Jan 62

Nebulin is a family of giant myofibrillar proteins with molecular masses ranging over 700-900 kDa. Using a human nebulin cDNA probe, we isolated three nebulin cDNA clones from a mouse skeletal muscle cDNA library. These three clones, labeled 8c. 7a and 4b. carry inserts of 2.0, 3.0 and 3.5 kb, respectively. In Northern blots, each insert detected the same approximately = 25 kb message from skeletal muscle as the human nebulin probe, while detecting no messages from cardiac muscle. Sequence data in combination with reverse-transcriptase PCR indicates that clones 7a and 8c overlap to form 4076 bp contiguous sequence. Alignment with the published full-length human nebulin sequence indicates that clone 4b overlaps with clone 7a over 1596 bp. However, after the first 798-bp overlap, the sequence of these two mouse nebulin clones diverge, suggesting that they derive from distinct transcripts encoding isoforms of mouse nebulin. The mouse nebulin clones encode a series of = 245-residue super repeats, each of which can be subdivided into seven = 35-residue, weakly repeating modules centered around a conserved tyrosine residue, consistent with the human nebulin sequence. The mouse nebulin clones align along the central third of the full-length human sequence, corresponding to super repeats 8-16 of the 22 super repeats found in human nebulin. The translated sequence is greater than 90% identical to the human sequence, with the exception of a 200-amino-acid region at the C-terminus of clone 4b, which is less than 60% identical. In genomic Southern blots, a mouse nebulin probe detected a homologous sequence in a wide variety of vertebrate species under stringent conditions. However, no significant hybridization was observed to genomic DNA from invertebrates and microorganisms, even under very low stringency. The sequence and Southern-blot data suggest that the nebulin sequence is highly conserved among vertebrate species.
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PMID:cDNA cloning of mouse nebulin. Evidence that the nebulin-coding sequence is highly conserved among vertebrates. 877 33

The synchronized contraction of myocytes in cardiac muscle requires the structural and functional integrity of the gap junctions present between these cells. Gap junctions are clusters of intercellular channels formed by transmembrane proteins of the connexin (Cx) family. Products of several Cx genes have been identified in the mammalian heart (eg, Cx45, Cx43, Cx40, and Cx37), and their expression was shown to be regulated during the development of the myocardium. Cx43, Cx40, and Cx45 are components of myocyte gap junctions, and it has also been demonstrated that Cx40 was expressed in the endothelial cells of the blood vessels. The aim of the present work was to investigate the expression and regulation of Cx40, Cx43, and Cx37 during the early stages of mouse heart maturation, between 8.5 days post coitum (dpc), when the first rhythmic contractions appear, and 14.5 dpc, when the four-chambered heart is almost completed. At 8.5 dpc, only the reverse-transcriptase polymerase chain reaction technique has allowed identification of Cx43, Cx40, and Cx37 gene transcripts in mouse heart, suggesting a very low activity level of these genes. From 9.5 dpc, all three transcripts became detectable in whole-mount in situ-hybridized embryos, and the most obvious result was the labeling of the vascular system with Cx40 and Cx37 anti-sense riboprobes. Cx40 and Cx37 gene products (transcript and/or protein) were demonstrated to be expressed in the vascular endothelial cells at all stages examined. By contrast, only Cx37 gene products were found in the endothelial cells of the endocardium. In heart, Cx37 was expressed exclusively in these cells, which rules out any direct involvement of this Cx in the propagation of electrical activity between myocytes and the synchronization of contractions. Between 9.5 and 11.5 dpc, Cx40 gene activation in myocytes was demonstrated to proceed according to a caudorostral gradient involving first the primitive atrium and the common ventricular chamber (9.5 dpc) and then the right ventricle (11.5 dpc). During this period of heart morphogenesis, there is clearly a temporary and asymmetrical regionalization of the Cx40 gene expression that is superimposed on the functional regionalization. In addition, comparison of Cx40 and Cx43 distribution at the above developmental stages has shown that these Cxs have overlapping (left ventricle) or complementary (atrial tissue and right ventricle) expression patterns.
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PMID:Expression pattern of connexin gene products at the early developmental stages of the mouse cardiovascular system. 928 45

We have derived a cardiac muscle cell line, designated HL-1, from the AT-1 mouse atrial cardiomyocyte tumor lineage. HL-1 cells can be serially passaged, yet they maintain the ability to contract and retain differentiated cardiac morphological, biochemical, and electrophysiological properties. Ultrastructural characteristics typical of embryonic atrial cardiac muscle cells were found consistently in the cultured HL-1 cells. Reverse transcriptase-PCR-based analyses confirmed a pattern of gene expression similar to that of adult atrial myocytes, including expression of alpha-cardiac myosin heavy chain, alpha-cardiac actin, and connexin43. They also express the gene for atrial natriuretic factor. Immunohistochemical staining of the HL-1 cells indicated that the distribution of the cardiac-specific markers desmin, sarcomeric myosin, and atrial natriuretic factor was similar to that of cultured atrial cardiomyocytes. A delayed rectifier potassium current (IKr) was the most prominent outward current in HL-1 cells. The activating currents displayed inward rectification and deactivating current tails were voltage-dependent, saturated at >>+20 mV, and were highly sensitive to dofetilide (IC50 of 46.9 nM). Specific binding of [3H]dofetilide was saturable and fit a one-site binding isotherm with a Kd of 140 +/- 60 nM and a Bmax of 118 fmol per 10(5) cells. HL-1 cells represent a cardiac myocyte cell line that can be repeatedly passaged and yet maintain a cardiac-specific phenotype.
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PMID:HL-1 cells: a cardiac muscle cell line that contracts and retains phenotypic characteristics of the adult cardiomyocyte. 950 Dec 1

The Ca2+ release channel of the sarcoplasmic reticulum (SR) is essential for the release of Ca2+ from intracellular stores and is expressed widely in various excitable cells. It plays a key role particularly in excitation contraction coupling in myocytes in skeletal and cardiac muscle. Three isoforms of the SR Ca2+ release channel have been cloned. Recently coexpression of different isoforms was reported in different animal species and various tissues. In human cardiac tissue, however, isoform expression is not yet established. Therefore the aim of this study was to characterize isoform expression of the SR Ca2+ release channel in the human heart. We examined specific isoform expression of mRNA and proteins of the SR Ca2+ release channel in the four different chambers of the heart and the interventricular septum from explanted human hearts from nonfailing organ donors (n=8). Reverse transcriptase PCR from total cardiac RNA with isoform specific primers and western blots from myocardial homogenates with isoform specific antibodies were performed. Quantification of protein expression was achieved by densitometric scanning and computer analysis and is expressed as densitometric units per microgram of protein. A single band DNA signal was detected by reverse transcriptase PCR for the skeletal isoform 1 and the cardiac isoform 2 and isoform 3 in all regions of the human heart investigated. Specific protein expression was detected in all five myocardial regions of the human heart in western blots for the skeletal isoform I and cardiac isoform 2, and a weaker specific band was also detectable for isoform 3 of the SR Ca2+ release channel. Quantification of protein expression showed significant (P=0.008) lower expression of isoform 1 in the right ventricle (42+/-4 densitometric units/g tissue) and similar expression in all other regions (right atrium 58+/-3; septum 51+/-5, left atrium 54+/-5; left ventricle 51+/-6). Isoform 2 of the SR Ca2+ release channel was also significantly lower (P=0.001) in the right ventricle (33+/-4 densitometric/g tissue) and similar in the other heart chambers (right atrium 42+/-5: septum 41+/-3, left atrium 52+/-6, left ventricle 42+/-3). Differences in isoform 3 of the SR Ca2+ release channel for the various myocardial regions did not reach significant levels (right atrium 45+/-6, right ventricle 38+/-5, septum 49+/-8, left atrium 46+/-7, and in left ventricle 45+/-3 densitometric units/g tissue). In conclusion, all three isoforms of the SR Ca2+ release channel were determined in the human heart at both mRNA and protein levels with different quantitative expression in the different heart chambers. Coexpression of the three different isoforms with different functional properties might increase the complexity of regulation of excitation contraction coupling in the human heart in a chamber specific mode.
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PMID:Isoform expression of the sarcoplasmic reticulum Ca2+ release channel (ryanodine channel) in human myocardium. 1100 33

Mammalian small heat shock proteins including Hsp27 and alpha-B crystallin are constitutively expressed in various adult and embryonic tissues including skeletal and cardiac muscle. However, the function of these proteins during embryonic development is not understood, and information on their expression during the earliest stages of development is limited. We have recently demonstrated constitutive and stress inducible expression of a homologue of human Hsp27 in adult zebrafish, an important experimental model of vertebrate developmental processes. Here, we assessed the temporospatial dynamics of zebrafish Hsp27 (hsp27) and alpha-B crystallin (cryab) gene expression using reverse-transcriptase PCR (RT-PCR) and hsp27 expression by in situ hybridization. Our results reveal that initial upregulation of hsp27 expression occurs during early gastrulation. Expression of hsp27 is detected transiently in developing myotomes, lens and brain, and more persistently in developing heart. The constitutive expression level of hsp27 in embryos at some stages of development is considerably greater than that observed in unstressed adult tissues. Expression of hsp27 was also observed in all tissues examined in embryos recovering from heat stress. The pattern of expression observed for hsp27 overlaps partially, but not completely, with that reported for other heat shock proteins.
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PMID:Developmentally regulated gene expression of the small heat shock protein Hsp27 in zebrafish embryos. 1632 46


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