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  • 1
    Electronic Resource
    Electronic Resource
    Disruption of epithelial tight junctions is prevented by cyclic nucleotide-dependent protein kinase inhibitors (2000)
    Springer
    Histochemistry and cell biology 113 (2000), S. 349-361 
    Details
    ISSN: 1432-119X
    Keywords: Tight junction Calcium switch Epithelial cells Protein kinase A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Tight junctions (TJs), the most apical of the intercellular junctions, prevent the passage of ions and molecules through the paracellular pathway. Intracellular signalling molecules are likely to be involved in the regulation of TJ integrity. In order to specifically investigate the role of protein kinase A (PKA) in the maintenance of epithelial TJ integrity, calcium-switch experiments were performed, in which calcium was removed from EpH4 and MDCK culture medium, in the absence or presence of the PKA inhibitors H-89 or HA-1004. Removal of calcium from the culture media of the epithelial cells resulted in disruption of the TJs, characterised by a loss of membrane association of the TJ-associated proteins occludin, ZO-1 and ZO-2, by a loss of TJ strands, by a marked decrease in the transepithelial electrical resistance and by a dramatic increase in the transepithelial permeability to tracers. The association of occludin, ZO-1 and ZO-2 with the actin cytoskeleton is not affected. In contrast, when the removal of calcium was performed in the presence of either the PKA inhibitor H-89 or HA-1004, all barrier characteristics were preserved. Our data indicate that following the removal of calcium from the culture medium of epithelial cells in vitro, PKA is activated and subsequently is involved in the disruption of TJs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180000143
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  • 2
    Electronic Resource
    Electronic Resource
    Tight Junctions of the Blood–Brain Barrier (2000)
    Springer
    Cellular and molecular neurobiology 20 (2000), S. 57-76 
    Details
    ISSN: 1573-6830
    Keywords: tight junction ; blood–brain barrier ; morphology ; freeze–fracture ; cadherins ; catenins ; occludin ; cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The blood–brain barrier is essential for the maintainance and regulation of the neural microenvironment. The blood–brain barrier endothelial cells comprise an extremely low rate of transcytotic vesicles and a restrictive paracellular diffusion barrier. The latter is realized by the tight junctions between the endothelial cells of the brain microvasculature, which are subject of this review. Morphologically, blood–brain barrier-tight junctions are more similar to epithelial tight junctions than to endothelial tight junctions in peripheral blood vessels. 2. Although blood–brain barrier-tight junctions share many characteristics with epithelial tight junctions, there are also essential differences. However, in contrast to tight junctions in epithelial systems, structural and functional characteristics of tight junctions in endothelial cells are highly sensitive to ambient factors. 3. Many ubiquitous molecular constituents of tight junctions have been identified and characterized including claudins, occludin, ZO-1, ZO-2, ZO-3, cingulin, and 7H6. Signaling pathways involved in tight junction regulation comprise, among others, G-proteins, serine, threonine, and tyrosine kinases, extra- and intracellular calcium levels, cAMP levels, proteases, and TNFα. Common to most of these pathways is the modulation of cytoskeletal elements which may define blood–brain barrier characteristics. Additionally, cross-talk between components of the tight junction– and the cadherin–catenin system suggests a close functional interdependence of the two cell–cell contact systems. 4. Recent studies were able to elucidate crucial aspects of the molecular basis of tight junction regulation. An integration of new results into previous morphological work is the central intention of this review.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006995910836
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    Paper (German National Licenses)
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