title: Claudins in Caenorhabditis elegans: their distribution and barrier function in the epithelium.
abstract: Claudins ( approximately 23 kDa) with four transmembrane domains are major cell adhesion molecules working at tight junctions in vertebrates, where the intercellular space is tightly sealed (reviewed in ). We examined here the possible occurrence of claudin-like proteins in invertebrates, which do not bear typical tight junctions. Close blast searching of the C. elegans genome database identified four claudin-related, approximately 20-kDa integral membrane proteins (CLC-1 to -4), which showed sequence similarity to the vertebrate claudins. The expression and distribution of CLC-1 was then examined in detail by GFP technology as well as by immunofluorescence microscopy. CLC-1 was mainly expressed in the epithelial cells in the pharyngeal region of digestive tubes and colocalized with AJM-1 at their intercellular junctions. Then, to examine the possible involvement of CLC-1 in the barrier function, we performed RNA interference in combination with a tracer experiment: in CLC-1-deficient worms, the barrier function of the pharyngeal portion of the digestive tubes appeared to be severely affected. CLC-2 was expressed in seam cells in the hypodermis, and it also appeared to be involved in the hypodermis barrier. These findings indicated that multiple species of the claudin homologs, which are involved in the barrier function of the epithelium, exist in C. elegans.
authors.affiliation: Tsukita Cell Axis Project, ERATO, Japan Science and Technology Corporation, Kyoto Research Park, Shimogyo-ku, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Asano
authors.forename: Kimiko
authors.initials: K
authors.lastname: Asano
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sasaki
authors.forename: Mikio
authors.initials: M
authors.lastname: Furuse
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsukita
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000235:genetics*; D062506:Claudin-4; D057167:Claudins; D004848:Epithelium; D041981:Gastrointestinal Tract / Q000000981:diagnostic imaging / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D034622:RNA Interference; D014463:Ultrasonography
chemical_list: D015815:Cell Adhesion Molecules; D062506:Claudin-4; D057167:Claudins; D008565:Membrane Proteins; C122101:claudin 6