title: The different structures containing tight junction proteins in epidermal and other stratified epithelial cells, including squamous cell metaplasia.
abstract: In stratified squamous epithelia constituent proteins of tight junctions (TJs) are not restricted to the zonula occludens-related structures of the uppermost living cell layer such as the stratum granulosum of the epidermis but TJ membrane proteins such as occludin and certain members of the claudin family as well as TJ plaque proteins, notably cingulin and protein ZO-1, have also been identified by immunofluorescence and immunoelectron microscopy in more basal layers where they form special cell-cell-connecting structures such as the "lamellated" and the "sandwich" junctions. In the present study, we describe another TJ protein-containing structure, the very small puncta occludentia ("stud junctions"), as the smallest identifiable TJ-like unit that occurs in most, perhaps all strata. We have also determined the specific distributions of TJ proteins in the cell layers of squamous cell metaplasias of the human bronchial tract. Moreover, we show that the occludin-related tetraspanin protein tricellulin-alpha connects and seals the membranes of adjacent "three corner" cell structures of the uppermost layer in keratinocytes growing in culture. We hypothesize the possible occurrence of tricellulin-beta in more basal cell layers of keratinocyte cultures and the general occurrence of different tricellulin splice forms in stratified epithelia in situ, and discuss the possible functions of TJ proteins in stratified epithelia and tumors derived therefrom.
authors.affiliation: Division of Cell Biology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Schlüter
authors.forename: Ingrid
authors.initials: I
authors.lastname: Moll
authors.forename: Hartwig
authors.initials: H
authors.lastname: Wolburg
authors.forename: Werner W
authors.initials: WW
authors.lastname: Franke
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002450:Cell Communication; D002478:Cells, Cultured; D004817:Epidermis / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D015603:Keratinocytes / Q000473:pathology; D062794:MARVEL Domain Containing 2 Protein; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008679:Metaplasia; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D062794:MARVEL Domain Containing 2 Protein; C516798:MARVELD2 protein, human; D008565:Membrane Proteins