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

We have investigated the properties of gap junction channels of three human malignant trophoblast (choriocarcinoma) cell lines: BeWo, Jeg-3 and JAr, as well as in Jeg-3 cells stably transfected with rat connexin40 (Cx40). Reverse-transcriptase polymerase chain reaction (RT-PCR), Northern blot analysis and immunostaining demonstrated expression of Cx40 in BeWo and JAr cell lines. JAr cells also expressed minor amounts of Cx43. Very low levels of Cx40 transcripts were revealed by RT-PCR in parental Jeg-3 cells, but Cx40 protein was not detected. To compare properties of endogenously and exogenously expressed Cx40 channels we have transfected Jeg-3 cells with rat Cx40. Recordings with dual whole-cell methods were used to determine the junctional conductance (gj) in the various cell lines and transfectants. Cx40 channels exogenously expressed in Jeg-3 cells demonstrated steep voltage sensitivity in the transjunctional voltage range of +/-30 to +/-40 mV and a unitary mainstate conductance of 175 pS, values which are similar to the data obtained from endogenously expressed Cx40 in BeWo cell pairs. In addition, greater driving forces resulted in a lower unitary conductance of about 30 pS, exclusively in BeWo cells. Between JAr cell pairs we determined a gj of 10 nS and unitary conductances were predominantly 100 and 152 pS. Voltage dependence was less sensitive in JAr cells compared to Cx40 transfectants and BeWo cells. Thus, coexpression of Cx43 and Cx40 leads to a macroscopic conductance with a mixture of properties expected for each connexin, whereas single-channel properties of each connexin type are maintained.
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PMID:Properties of connexin40 gap junction channels endogenously expressed and exogenously overexpressed in human choriocarcinoma cell lines. 876 10

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

Myelinating Schwann cells express the gap junction protein, connexin (Cx)32, which is present at the nodes of Ranvier and Schmidt-Lantermann incisures (Bergoffen et al. [1993] Science (Wash. ) 262:2039-2042). Following peripheral nerve injury, other members of the connexin gene family are also expressed (Chandross et al. [1996a] Mol. Cell. Neurosci. 7:501-518). This study surveys the connexin(s) expressed by rat sciatic nerve, cultured Schwann cells, and a mouse Schwannoma (TR6 Bc1) cell line. Reverse transcriptase-polymerase chain reaction (RT-PCR) amplification revealed a constitutive expression of mRNA encoding Cx32 and 43 but not Cx26, 37, 40, 45, and 46 in sciatic nerve. Mitogenic stimulation of cultured Schwann cells expressing Cx32 also resulted in the appearance of Cx43 mRNA. Schwannoma cells expressed exclusively Cx43 mRNA. These results were confirmed by Northern blot analysis. Functional gap junctions in cultured Schwann and Schwannoma cells were shown by analysis of the intercellular transfer of Lucifer yellow, although the coupling between primary Schwann cells was weak or undetectable. Treatment of primary Schwann cells with mitogens resulted in extensive dye coupling. An immunohistochemical study of adult sciatic nerve sections demonstrated Cx32 immunoreactivity at the nodes of Ranvier and in Schwann cell bodies. Lower intensity staining of Cx43 along the myelin sheath and Schwann cell bodies was also observed. Indirect immunofluorescent studies of Schwann cells treated with mitogens showed characteristic punctate cell surface staining of Cx43; Cx32 staining was detected mainly intracellularly. These results lead to the conclusion that in addition to the expression of Cx32 by normal adult sciatic nerve, low amounts of Cx43 protein are also present. The implications of the expression of two connexins by Schwann cells in Charcot-Marie-Tooth X-linked disease, a demyelinating peripheral neuropathy, are discussed.
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PMID:Multiple connexin expression in peripheral nerve, Schwann cells, and Schwannoma cells. 1039 94

It is well established that the 43-kDa connexin (Cx43) is predominantly expressed by ovarian somatic cells, whereas the identity of the connexins contributed by the oocyte to form gap junctions with its neighboring cells is not fully elucidated. Our study aimed to examine oocytes for the expression and regulation of Cx43 throughout oogenesis. Growing and fully grown rat oocytes that were meiotically incompetent and competent, respectively, were examined. Fully grown oocytes were analyzed either before or after reinitiation of meiosis as well as at the second meiotic metaphase. Immunofluorescent analysis of zona pellucida-free oocytes using conventional and confocal microscopy demonstrated a characteristic pattern of punctuated staining of Cx43 on the oolema. Immunogold electron microscopy localized Cx43 to the oocyte surface and the microvillar processes. Reverse transcriptase-polymerase chain reaction and Western blot analysis revealed similar amounts of Cx43 gene and protein in oocytes of different developmental stages. However, a relative increase in the phosphorylated forms of the protein was observed in fully grown oocytes that had completed their maturation. Our findings demonstrate that rat oocytes express a developmentally regulated Cx43. They further suggest that homotypic gap junctions that consist of Cx43 may be present between rat oocytes and their adjacent cumulus cells.
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PMID:Connexin43 in rat oocytes: developmental modulation of its phosphorylation. 1187 59