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  • 1
    Electronic Resource
    Electronic Resource
    Molecular cloning and expression of rat connexin40, a gap junction protein expressed in vascular smooth muscle (1992)
    Springer
    The journal of membrane biology 127 (1992), S. 69-76 
    Details
    ISSN: 1432-1424
    Keywords: gap junction ; intercellular communication ; connexin40 ; vascular smooth muscle ; A7r5 cell line
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Gap junctions contain intercellular channels which are formed by members of a group of related proteins called connexins. Connexins contain conserved transmembrane and extracellular domains, but unique cytoplasmic regions which may provide connexin-specific physiologic properties. We used polymerase chain reaction (PCR) amplification and cDNA library screening to clone DNA encoding a novel member of this gene family, rat connexin40 (Cx40). The derived rat Cx40 polypeptide contains 356 amino acids, with a predicted molecular mass of 40,233 Da. Sequence comparisons suggest that Cx40 is the mammalian homologue of chick connexin42, but it has predicted cytoplasmic regions that differ from previously described mammalian connexins. Southern blots of rat genomic DNA suggest that Cx40 is encoded by a single copy gene containing no introns within its coding region. Northern blots demonstrate that Cx40 is expressed in multiple tissues (including lung, heart, uterus, ovary, and blood vessels) and in primary cultures and established lines of vascular smooth muscle cells. Cx40 is coexpressed with connexin43 in several cell types, including A7r5 cells, which contain two physiologically distinct gap junctional channels. To demonstrate that Cx40 could form functional channels, we stably transfected communication-deficient Neuro2A cells with Cx40 DNA. These Cx40-transfected cells showed intercellular passage of microinjected Lucifer yellow CH. The expression of multiple connexins (such as Cx40 and Cx43) by a single cell may provide a mechanism by which cells regulate intercellular coupling through the formation of multiple channels
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232759
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  • 2
    Electronic Resource
    Electronic Resource
    Expression of the gap junction protein connexin43 in embryonic chick lens: Molecular cloning, ultrastructural localization, and post-translational phosphorylation (1990)
    Springer
    The journal of membrane biology 116 (1990), S. 163-175 
    Details
    ISSN: 1432-1424
    Keywords: gap junctions ; connexin43 ; lens epithelium ; molecular cloning ; protein phosphorylation ; intercellular communication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Lens epithelial cells are physiologically coupled to each other and to the lens fibers by an extensive network of intercellular gap junctions. In the rat, the epithelial-epithelial junctions appear to contain connexin43, a member of the connexin family of gap junction proteins. Limitations on the use of rodent lenses for the study of gap junction formation and regulation led us to examine the expression of connexin43 in embryonic chick lenses. We report here that chick connexin43 is remarkably similar to its rat counterpart in primary amino acid sequence and in several key structural features as deduced by molecular cDNA cloning. The cross-reactivity of an anti-rat connexin43 serum with chick connexin43 permitted definitive immunocytochemical localization of chick connexin43 to lens epithelial gap junctional plaques and examination of the biosynthesis of connexin43 by metabolic radiolabeling and immunoprecipitation. We show that chick lens cells synthesize connexin43 as a single, 42-kD species that is efficiently posttranslationally converted to a 45-kD form. Metabolic labeling of connexin43 with32P-orthophosphate combined with dephosphorylation experiments reveals that this shift in apparent molecular weight is due solely to phosphorylation. These results indicate that embryonic chick lens is an appropriate system for the study of connexin43 biosynthesis and demonstrate for the first time that connexin43 is a phosphoprotein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868674
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  • 3
    Electronic Resource
    Electronic Resource
    Connexin family of gap junction proteins (1990)
    Springer
    The journal of membrane biology 116 (1990), S. 187-194 
    Details
    ISSN: 1432-1424
    Keywords: gap junctions ; connexin ; intercellular communication ; molecular cloning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868459
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  • 4
    Electronic Resource
    Electronic Resource
    Localization and distribution of gap junctions in normal and cardiomyopathic hamster heart (1994)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 222 (1994), S. 203-213 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Gap junctions in mammalian heart function to provide low-resistance channels between adjacent cells for passage of ions and small molecules. It is clear that the almost unrestricted passage of ions between cells, ionic coupling, is required for coordinate and synchronous contraction. This knowledge of gap junction function has made it important to study their properties in normal and abnormal tissues. In the present study, we analyzed gap junction distribution in normal and cardiomyopathic heart tissue utilizing immunofluorescent and electron microscopy techniques. Frozen, unfixed sections of age-matched normal and cardiomyopathic cardiac tissues were immunofiuorescently stained using an antibody directed against a specific peptide sequence of the connexin-43 gap junction protein. These studies revealed a characteristic punctate staining pattern for the intercalated discs in normal tissues. Some of the intercalated discs in cardiomyopathic hearts appeared to stain normally; however, others stained diffusely. The pixel intensity distribution of the confocal images demonstrated a marked difference of up to 90% increase in the number of pixels in cardiomyopathic myocardium (CM), yet the pixel intensity of gap junctions had a decrease of approximately 60%. This suggests the possibility that connexin-43 is present in CM cells in significant quantity; however, it does not become localized on the membranes as in normal cells. Electron-microscopic findings corroborate these observations on CM cells by showing an irregular distribution of intercalated discs relatively smaller in size with abnormal orientation and distribution. © 1994 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052220207
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  • 5
    Electronic Resource
    Electronic Resource
    Structural and molecular determinants of intercellular coupling in cardiac myocytes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 31 (1995), S. 357-363 
    Details
    ISSN: 1059-910X
    Keywords: Gap junctions ; Connexins ; Immunofluorescence ; In situ hybridization ; Arrhythmias ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Electrical activation of the heart requires intercellular transfer of current through gap junctions connecting individual cardiac myocytes. Using a combination of light and electron microscopic techniques and molecular approaches, we have characterized the number, size, and spatial distribution of intercellular connections at gap junctions in cardiac myocytes and have also cloned, sequenced, and elucidated the subcellular distribution of three physiologically distinct gap junction channel proteins. In this review, we present evidence to suggest that the spatial distribution of myocyte interconnections and the molecular composition of gap junction channels may confer distinct conduction properties on specific tissues of the mammalian heart such as atrial and ventricular myocardium, and the nodes and bundles of the cardiac conduction system. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070310505
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  • 6
    Electronic Resource
    Electronic Resource
    Regulation of connexin43 expression and function by prostaglandin E2 (PGE2) and parathyroid hormone (PTH) in osteoblastic cells (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 8-21 
    Details
    ISSN: 0730-2312
    Keywords: gap junctions ; dye-coupling ; connexin43 ; parathyroid hormone ; prostaglandin E2 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Connexin43 (Cx43) forms gap junctions that mediate intercellular communication between osteoblasts. We have examined the effects of prostaglandin E2 (PGE2) and parathyroid hormone (PTH) on gap junctional communication in the rat osteogenic sarcoma cells UMR 106-01. Incubation with either PGE2 or PTH rapidly (within 30 min) increased transfer of negatively charged dyes between UMR 106-01 cells. This stimulatory effect lasted for at least 4 h. Both PGE2 and PTH increased steady-state levels of Cx43 mRNA, but only after 2-4 h of incubation. Transfection with a Cx43 gene construct linked to luciferase showed that this effect of PTH was the result of transcriptional upregulation of Cx43 promoter. Stimulation of dye coupling and Cx43 gene transcription were reproduced by forskolin and 8Br-cAMP. Exposure to PGE2 for 30 min increased Cx43 abundance at appositional membranes in UMR 106-01, whereas total Cx43 protein levels increased only after 4-6 h of incubation with either PGE2 or PTH. Inhibition of protein synthesis by cycloheximide did not affect this early stimulation of dye coupling, but it significantly inhibited the sustained effect of PTH and forskolin on cell coupling. In summary, both PTH and PGE2, presumably through cAMP production, enhance gap junctional communication in osteoblastic cell cultures via two mechanisms: initial rapid redistribution of Cx43 to the cell membrane, and later stimulation of Cx43 gene expression. Modulation of intercellular communication represents a novel mechanism by which osteotropic factors regulate the activity of bone forming cells. J. Cell. Biochem. 68:8-21, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Zygotic expression of the connexin43 gene supplies subunits for gap junction assembly during mouse preimplantation development (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 30 (1991), S. 18-26 
    Details
    ISSN: 1040-452X
    Keywords: Gap junction protein ; Gene expression ; Compaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: De novo assembly of gap junctions begins during compaction in the eight-cell stage of mouse development, and intercellular coupling mediated by gap junctions appears to be required for maintenance of the compacted state. We have begun to explore the expression of the family of genes encoding the connexins, the proteins that form the gap junction channels. We recently reported that a protein with antigenic and size similarity with connexin32, the rat liver gap junction protein, is inherited as an oogenetic product by the mouse zygote, but its gene appears not to be transcribed prior to implantation (Barron et al., Dev Genet 10:318-323, 1989). Here we report that another member of this gene family, connexin43, is transcribed by the embryonic genome from shortly after the time of genomic activation. As revealed by Northern blotting, connexin43 mRNA is absent from ovulated oocytes, becomes detectable in the 4-cell stage, and accumulates steadily thereafter to reach a maximum in blastocysts. In contrast, no transcripts of connexin26 could be detected in any preimplantation stage. A protein with antigenic and size similarity with connexin43 from rat heart was found by Western blotting to accumulate from the four-cell stage onward. Immunofluorescence analysis with embryo whole mounts was used to demonstrate that this protein is incorporated into punctate interblastomeric foci during compaction, consistent with its assembly into gap junction plaques. We conclude that connexin43 is one member of the connexin gene family whose zygotic expression is critical for preimplantation morphogenesis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080300103
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  • 8
    Electronic Resource
    Electronic Resource
    Chicken tissue binding sites for a purified chicken lectin (1980)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 219-227 
    Details
    ISSN: 0091-7419
    Keywords: lectins ; lectin binding sites ; cell surfaces ; extracellular materials ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A lactose-binding lectin previously purified from embryonic chicken muscle and adult chicken liver, and here referred to as chicken-lactose-lectin-I (CLL-I), was added to sections of various adult chicken tissues to detect available binding sites. Both the sites of binding of added CLL-I as well as the tissue distribution of endogenous CLL-I were determined by indirect immunofluorescence using a rabbit antibody to CLL-I followed by fluorescent goat anti-rabbit IgG. Some tissues such as intestine and kidney showed abundant extracellular binding sites for the lectin, primarily between cells, in basement membrane, and in material on the luminal surface. In contrast, adult heart showed no significant binding sites for CLL-I. Adult pancreas showed considerable endogenous CLL-I in an extracellular site surrounding exocrine lobules, but added CLL-I did not bind substantially. The distribution of CLL-I binding sites in intestine were mimicked by those of purpurin, another lactose-binding lectin. CLL-I binding sites were also detected on the surface of cultured chick embryo skin fibroblasts. The factors controlling the specific distribution of occupied and unoccupied CLL-I binding sites are not known.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400130210
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  • 9
    Electronic Resource
    Electronic Resource
    Endogenous lectins in chickens and slime molds: Transfer from intracellular to extracellular sites (1981)
    New York, NY : Wiley-Blackwell
    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 233-242 
    Details
    ISSN: 0275-3723
    Keywords: lectins ; slime mold lectins ; vertebrate lectins ; chicken-lactose-lectin-I ; chicken-lactose-lectin-II ; chicken heparin lectin ; Dictyostelium ; secretion ; muscle development ; extracellular materials ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Endogenous lectins in both cellular slime molds and chicken tissues have been localized primarily intracellularly, in contrast with the predominantly extracellular localization of the glycoproteins, glycolipids, and glycosaminoglycans with which they might interact. Here we present evidence that lectins in both of these organisms may be externalized and become associated with the cell surface and/or extracellular materials. In chicken intestine, chicken-lactose-lectin-II is shown to be localized in the secretory granules of the goblet cells, along with mucin, and to be secreted onto the intestinal surface. In embryonic muscle, chicken-lactose-lectin-I is shown to be externalized with differentiation, ultimately becoming localized on the surface of myotubes and in the extracellular spaces. In a cellular slime mold, Dictyostelium purpureum, externalization of lectin is elicited by either polyvalent glycoproteins that bind the small amount of endogenous cell surface lectin, or by slime mold or plant lectins that bind unoccupied complementary cell surface oligosaccharides. These results suggest that externalization of endogenous lectin may be a response to specific external signals. We conclude that lectins are frequently held in intracellular reserves awaiting release for specific external functions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jsscb.1981.380160304
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  • 10
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    Special-interest subgroups at the ASCB: Gap junctions (1999)
    Cell Press
    Details
    Publication Date: 1999-03-01
    Print ISSN: 0962-8924
    Electronic ISSN: 1879-3088
    Topics: Biology , Medicine
    Published by Cell Press
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