title: Formation of aberrant TJ strands by overexpression of claudin-15 in MDCK II cells.
abstract: Claudins are one of the transmembrane proteins found at tight junctions (TJs); they constitute the backbone of TJ strands and comprise a multigene family. Claudins share a YV sequence at the COOH-termini, which is considered to be a ZO-binding motif. Overexpression of claudin-15 (15CL) or claudin-15 tagged with enhanced green fluorescent protein at the NH2-terminus (EGFP-15CL) induced aberrant strands in MDCK II cells, even though claudin-15 has the ZO-binding motif. Morphometric analysis by freeze-fracture electron microscopy revealed that the mean number of apical TJ strands increased by 47% in EGFP-1CL-expressing cells, 21% in EGFP-15CL-expressing cells, and 28% in 15CL-expressing cells. The number of free-ended apical strands increased remarkably in EGFP-15CL- and 15CL-expressing cells, but not in EGFP-1CL-expressing cells. When MDCK cells expressing EGFP-1CL, EGFP-15CL or 15CL were co-cultured with parent MDCK cells, which express claudin-1 but not claudin-15, EGFP-15CL and 15CL could not be concentrated at the apical junctional region between the heterotypic cells, though EGFP-1CL could. These results suggest that not only binding to ZO-1, but also head-to-head compatibility between claudin species, is involved in organizing claudin proteins at the apical junctional region.
authors.affiliation: Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-Ku, 812-8582 Fukuoka, Japan. sengoku@ana2.med.kyushu-u.ac.jp
authors.forename: Akihito
authors.initials: A
authors.lastname: Sengoku
authors.forename: Tetsuichiro
authors.initials: T
authors.lastname: Inai
authors.forename: Yosaburo
authors.initials: Y
authors.lastname: Shibata
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D062445:Claudin-1; D057167:Claudins; D004285:Dogs; D005347:Fibroblasts / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D007668:Kidney / Q000166:cytology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure; D015854:Up-Regulation / Q000235:genetics
chemical_list: C568108:CLDN1 protein, human; D062445:Claudin-1; D057167:Claudins; C568113:Cldn1 protein, mouse; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C459596:claudin 15; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins