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  • 1
    Keywords: CELLS ; EXPRESSION ; PROTEIN ; PROTEINS ; EPITHELIA ; KERATINOCYTES ; IDENTIFICATION ; MERKEL CELLS ; MELANOMA-CELLS ; ADHERENS JUNCTIONS ; plakophilin-2 ; Asymmetric junctions ; CONTACTS ; CYTOKERATIN ; Heterotypic junctions ; HUMAN-FETAL SKIN
    Abstract: Merkel cells (MCs) are special neuroendocrine epithelial cells that occur as individual cells or as cell groups within the confinements of a major epithelium formed and dominated by other epithelial cells. In the epidermis and some of its appendages MCs are mostly located in the basal cell layer, occasionally also in suprabasal layers and generally occur in linear arrays in outer root sheath cell layers of hair follicles. As MCs are connected to the adjacent keratinocytes by a series of adhering junctions (AJs), of which the desmosomes are the most prominent, these junctions represent heterotypic cell-cell connections, i.e. a kind of structure not yet elucidated in molecular terms. Therefore, we have studied these AJs in order to examine the molecular composition of the desmosomal halves. Using light- and electron-microscopic immunolocalization and keratin 20 as the MC-specific cell type marker we show that the plaques of the MC half of the desmosomes specifically and constitutively contain plakophilin Pkp2. This protein, however, is absent in the keratinocyte half of such heterotypic desmosomes which instead contains Pkp1 and/or Pkp3. We discuss the developmental, tissue-architectonic and functional importance of such asymmetric junctions in normal physiology as well as in diseases, in particular in the formation of distant tumor cell metastasis.
    Type of Publication: Journal article published
    PubMed ID: 22006253
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  • 2
    Keywords: immunohistochemistry ; ADHESION ; TIGHT JUNCTIONS ; HUMAN EPIDERMIS ; desmosomes ; STRATIFIED EPITHELIA ; ADHERENS JUNCTIONS ; cardiomyocytes ; HEART-MUSCLE CELLS ; plakophilin-2 ; AREA-COMPOSITA ; VERTEBRATES ; Epithelial cells ; Junction plaques ; Protein myozap
    Abstract: The protein myozap, a polypeptide of 54 kDa, has recently been identified as a component of the cytoplasmic plaques of the composite junctions (areae compositae) in the myocardiac intercalated disks and of the adherens junctions (AJs) in vascular endothelia. Now we report that using very sensitive new antibodies and drastic localization methods, we have also identified this protein as a component of the AJ plaques in simple and complex epithelia, in the adluminal cell layer of the transitional epithelium of the urinary tract and in certain cell layers of diverse stratified epithelia, including gingiva, tongue, pharynx and esophagus, cervix, vagina and epidermis. Myozap has not been identified in desmosomal and tight junction plaques. We have also detected protein myozap in AJ structures of carcinomas. The discovery of a novel major protein in AJ plaques now calls for re-examinations of molecular interactions in AJ formation and maintenance and also offers a new marker for diagnostic immunocytochemistry. We also discuss the need for progressive unravelling, extractive treatments and buffer rinses of sections and cultured cells to reveal obscured or masked antigens, before definitive negative conclusions in immunohistochemistry can be made.
    Type of Publication: Journal article published
    PubMed ID: 22160502
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  • 3
    Keywords: TISSUE ; TUMORS ; EXTRACELLULAR-MATRIX ; RIGHT-VENTRICULAR CARDIOMYOPATHY ; ADHERENS JUNCTIONS ; adhering junctions ; MESENCHYMAL STEM-CELLS ; plakophilin-2 ; AREA-COMPOSITA ; Puncta adhaerentia ; RECESSIVE MUTATION ; Heart valves ; MUSCLE CELLS ; PORCINE AORTIC-VALVE ; ATRIOVENTRICULAR VALVES ; CARDIAC-VALVE ; CUSHION DEVELOPMENT ; Myxomata ; Valvular interstitial cells
    Abstract: The interstitial cells of cardiac valves represent one of the most frequent cell types in the mammalian heart. In order to provide a cell and molecular biological basis for the growth of isolated valvular interstitial cells (VICs) in cell culture and for the use in re-implantation surgery we have examined VICs in situ and in culture, in fetal, postnatal and adult hearts, in re-associations with scaffolds of extracellular matrix (ECM) material and decellularized heart valves. In all four mammalian species examined (human, bovine, porcine and ovine), the typical mesenchymal-type cell-cell adherens junctions (AJs) connecting VICs appear as normal N-cadherin based puncta adhaerentia. Their molecular ensemble, however, changes under various growth conditions insofar as plakophilin-2 (Pkp2), known as a major cytoplasmic plaque component of epithelial desmosomes, is recruited to and integrated in the plaques of VIC-AJs as a major component under growth conditions characterized by enhanced proliferation, i.e., in fetal heart valves and in cell cultures. Upon re-seeding onto decellularized heart valves or in stages of growth in association with artificial scaffolds, Pkp2 is - for the most part - lost from the AJs. As Pkp2 has recently also been detected in AJs of cardiac myxomata and diverse other mesenchymal tumors, the demonstrated return to the normal Pkp2-negative state upon re-association with ECM scaffolds and decellularized heart valves may now provide a safe basis for the use of cultured VICs in valve replacement surgery. Even more surprising, this type of transient acquisition of Pkp2 has also been observed in distinct groups of endothelial cells of the endocardium, where it seems to correspond to the cell type ready for endothelial-mesenchymal transition (EMT)
    Type of Publication: Journal article published
    PubMed ID: 22290634
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  • 4
    Keywords: HEART ; TISSUE ; CELLS ; ADHERENS JUNCTIONS ; Valvular interstitial cells ; plakophilin-2 ; Heart valves ; adhering junctions
    Type of Publication: Meeting abstract published
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  • 5
    Keywords: PROTEIN ; TISSUE ; TUMORS ; MONOCLONAL-ANTIBODIES ; DESMOSOMAL PLAQUE ; RIGHT-VENTRICULAR CARDIOMYOPATHY ; ADHERENS JUNCTIONS ; EPITHELIAL DIFFERENTIATION ; adhering junctions ; HEART-MUSCLE CELLS ; plakophilin-2 ; AREA-COMPOSITA ; CYTOSKELETAL ARCHITECTURE ; PROTEIN PLAKOPHILIN-2 ; Myxomata ; Cardiac tumors ; Nuclear plakophilins
    Abstract: Within the characteristic ensemble of desmosomal plaque proteins, the protein plakophilin-2 (Pkp2) is known as a particularly important regulatory component in the cytoplasmic plaques of various other cell-cell junctions, such as the composite junctions () of the myocardiac intercalated disks and in the variously-sized and -shaped complex junctions of permanent cell culture lines derived therefrom. In addition, Pkp2 has been detected in certain protein complexes in the nucleoplasm of diverse kinds of cells. Using a novel set of highly sensitive and specific antibodies, both kinds of Pkp2, the junctional plaque-bound and the nuclear ones, can also be localized to the cytoplasmic plaques of diverse non-desmosomal cell-cell junction structures. These are not only the and the connecting various types of highly proliferative non-epithelial cells growing in culture but also some very proliferative states of cardiac interstitial cells and cardiac myxomata, including tumors growing in situ as well as fetal stages of heart development and cultures of valvular interstitial cells. Possible functions and assembly mechanisms of such Pkp2-positive cell-cell junctions as well as medical consequences are discussed
    Type of Publication: Journal article published
    PubMed ID: 22281687
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