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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: DESMOSOMAL PLAQUE PROTEINS ; ADHERENS JUNCTIONS ; N-CADHERIN ; SERTOLI-CELL ; POSTNATAL-DEVELOPMENT ; MALE CONTRACEPTIVE DEVELOPMENT ; RAT TESTIS ; ECTOPLASMIC SPECIALIZATION ; BARRIER DYNAMICS ; CYTOSKELETAL PROTEINS
    Abstract: The seminiferous tubules and the excurrent ducts of the mammalian testis are physiologically separated from the mesenchymal tissues and the blood and lymph system by a special structural barrier to paracellular translocations of molecules and particles: the "blood-testis barrier", formed by junctions connecting Sertoli cells with each other and with spermatogonial cells. In combined biochemical as well as light and electron microscopical studies we systematically determine the molecules located in the adhering junctions of adult mammalian (human, bovine, porcine, murine, i.e., rat and mouse) testis. We show that the seminiferous epithelium does not contain desmosomes, or "desmosome-like" junctions, nor any of the desmosome-specific marker molecules and that the adhering junctions of tubules and ductules are fundamentally different. While the ductules contain classical epithelial cell layers with E-cadherin-based adherens junctions (AJs) and typical desmosomes, the Sertoli cells of the tubules lack desmosomes and "desmosome-like" junctions but are connected by morphologically different forms of AJs. These junctions are based on N-cadherin anchored in cytoplasmic plaques, which in some subforms appear thick and dense but in other subforms contain only scarce and loosely arranged plaque structures formed by alpha- and beta-catenin, proteins p120, p0071 and plakoglobin, together with a member of the striatin family and also, in rodents, the proteins ZO-1 and myozap. These N-cadherin-based AJs also include two novel types of junctions: the "areae adhaerentes", i.e., variously-sized, often very large cell-cell contacts and small sieve-plate-like AJs perforated by cytoplasm-to-cytoplasm channels of 5-7 nm internal diameter ("cribelliform junctions"). We emphasize the unique character of this epithelium that totally lacks major epithelial marker molecules and structures such as keratin filaments and desmosomal elements as well as EpCAM- and PERP-containing junctions. We also discuss the nature, development and possible functions of these junctions.
    Type of Publication: Journal article published
    PubMed ID: 24907851
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  • 3
    Keywords: PROTEIN ; TISSUE ; FUSION ; MUTATIONS ; review ; EMBRYONIC HEART ; RIGHT-VENTRICULAR CARDIOMYOPATHY ; desmosomes ; MOLECULAR-GENETICS ; ADHERENS JUNCTIONS ; WOOLLY HAIR ; intercalated disk ; PLAKOPHILIN-2 MUTATIONS ; SUDDEN-DEATH ; Arrhythmogenic ventricular cardiomyopathy ; CARDIAC RYANODINE RECEPTOR ; Carvajal disease ; Composite junction ; GENOTYPE-PHENOTYPE ASSESSMENT ; Naxos disease ; PALMOPLANTAR KERATODERMA ; PLAKOGLOBIN-DEFICIENT MICE
    Abstract: In the past decade, an avalanche of findings and reports has correlated arrhythmogenic ventricular cardiomyopathies (ARVC) and Naxos and Carvajal diseases with certain mutations in protein constituents of the special junctions connecting the polar regions (intercalated disks) of mature mammalian cardiomyocytes. These molecules, apparently together with some specific cytoskeletal proteins, are components of (or interact with) composite junctions. Composite junctions contain the amalgamated fusion products of the molecules that, in other cell types and tissues, occur in distinct separate junctions, i.e. desmosomes and adherens junctions. As the pertinent literature is still in an expanding phase and is obviously becoming important for various groups of researchers in basic cell and molecular biology, developmental biology, histology, physiology, cardiology, pathology and genetics, the relevant references so far recognized have been collected and are presented here in the following order: desmocollin-2 (Dsc2, DSC2), desmoglein-2 (Dsg2, DSG2), desmoplakin (DP, DSP), plakoglobin (PG, JUP), plakophilin-2 (Pkp2, PKP2) and some non-desmosomal proteins such as transmembrane protein 43 (TMEM43), ryanodine receptor 2 (RYR2), desmin, lamins A and C, striatin, titin and transforming growth factor-beta 3 (TGF beta 3), followed by a collection of animal models and of reviews, commentaries, collections and comparative studies
    Type of Publication: Journal article published
    PubMed ID: 22450909
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Keywords: ANGIOGENESIS ; CELLS ; ENDOTHELIAL-CELLS ; IN-VITRO ; BLOOD ; Germany ; human ; IN-VIVO ; VITRO ; SYSTEM ; PROTEIN ; PROTEINS ; desmoplakin ; TISSUE ; COMPLEX ; COMPLEXES ; TISSUES ; beta-catenin ; TIGHT JUNCTIONS ; rodent ; JUNCTIONS ; LYMPHATIC ENDOTHELIUM ; RE ; DESMOSOMAL PLAQUE ; INTERCELLULAR-JUNCTIONS ; DESMOSOMAL PLAQUE PROTEINS ; SIZE ; ADHERENS JUNCTIONS ; BOVINE ; function ; lymph node ; LYMPH-NODE ; N-CADHERIN ; adhering junction ; VE-CADHERIN ; BLOOD-BRAIN-BARRIER ; Complexus adhaerens ; DESMOPLAKIN-CONTAINING JUNCTIONS ; HUMAN GLIOBLASTOMA-MULTIFORME ; retothelium ; TO-CELL JUNCTIONS
    Abstract: The significance of a special kind of VE-cadherin-based, desmoplakin- and plakoglobin-containing adhering junction, originally identified in certain endothelial cells of the mammalian lymphatic system ( notably the retothelial cells of the lymph node sinus and a subtype of lining endothelial cells of peripheral lymphatic vessels), has been widely confirmed and its importance in the formation of blood and lymph vessels has been demonstrated in vivo and in vitro. We have recently extended the molecular and structural characterization of the complexus adhaerens and can now report that it represents a rare and special combination of components known from three other major types of cell junction. It comprises zonula adhaerens proteins (VE-cadherin, alpha- and beta-catenin, protein p120(ctn), and afadin), desmosomal plaque components ( desmoplakin and plakoglobin), and tight-junction proteins (claudin-5 and ZO-1) and forms junctions that vary markedly in size and shape. The special character and the possible biological roles of the complexus adhaerens and its unique ensemble of molecules in angiogenesis, immunology, and oncology are discussed. The surprising finding of claudin-5 and protein ZO-1 in substructures of retothelial cell-cell bridges, i.e., structures that do not separate different tissues or cell layer compartments,suggests that such tight-junction molecules are involved in functions other than the "fence" and "barrier" roles of zonulae occludentes
    Type of Publication: Journal article published
    PubMed ID: 16372193
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  • 8
    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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  • 9
    Keywords: INTERMEDIATE-SIZED FILAMENTS ; STRATIFIED EPITHELIA ; DESMOSOMAL PLAQUE PROTEINS ; ADHERENS JUNCTIONS ; Area composita ; HEART-MUSCLE CELLS ; Molecular composition ; INTERCELLULAR ADHERING JUNCTIONS ; TARGET GENE PERP ; HUMAN-EPIDERMIS
    Abstract: Protein PERP (p53 apoptosis effector related to PMP-22) is a small (21.4 kDa) transmembrane polypeptide with an amino acid sequence indicative of a tetraspanin character. It is enriched in the plasma membrane and apparently contributes to cell-cell contacts. Hitherto, it has been reported to be exclusively a component of desmosomes of some stratified epithelia. However, by using a series of newly generated mono- and polyclonal antibodies, we show that protein PERP is not only present in all kinds of stratified epithelia but also occurs in simple, columnar, complex and transitional epithelia, in various types of squamous metaplasia and epithelium-derived tumors, in diverse epithelium-derived cell cultures and in myocardial tissue. Immunofluorescence and immunoelectron microscopy allow us to localize PERP predominantly in small intradesmosomal locations and in variously sized, junction-like peri- and interdesmosomal regions ("tessellate junctions"), mostly in mosaic or amalgamated combinations with other molecules believed, to date, to be exclusive components of tight and adherens junctions. In the heart, PERP is a major component of the composite junctions of the intercalated disks connecting cardiomyocytes. Finally, protein PERP is a cobblestone-like general component of special plasma membrane regions such as the bile canaliculi of liver and subapical-to-lateral zones of diverse columnar epithelia and upper urothelial cell layers. We discuss possible organizational and architectonic functions of protein PERP and its potential value as an immunohistochemical diagnostic marker.
    Type of Publication: Journal article published
    PubMed ID: 23689684
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