title: Lipid polarity is maintained in absence of tight junctions.
abstract: The role of tight junctions (TJs) in the establishment and maintenance of lipid polarity in epithelial cells has long been a subject of controversy. We have addressed this issue using lysenin, a toxin derived from earthworms, and an influenza virus labeled with a fluorescent lipid, octadecylrhodamine B (R18). When epithelial cells are stained with lysenin, lysenin selectively binds to their apical membranes. Using an artificial liposome, we demonstrated that lysenin recognizes the membrane domains where sphingomyelins are clustered. Interestingly, lysenin selectively stained the apical membranes of epithelial cells depleted of zonula occludens proteins (ZO-deficient cells), which completely lack TJs. Furthermore, the fluorescent lipid inserted into the apical membrane by fusion with the influenza virus did not diffuse to the lateral membrane in ZO-deficient epithelial cells. This study revealed that sphingomyelin-cluster formation occurs only in the apical membrane and that lipid polarity is maintained even in the absence of TJs.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan. ikenouchi@sbchem.kyoto-u.ac.jp
authors.forename: Junichi
authors.initials: J
authors.lastname: Ikenouchi
authors.forename: Mayu
authors.initials: M
authors.lastname: Suzuki
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Umeda
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Ikeda
authors.forename: Ryo
authors.initials: R
authors.lastname: Taguchi
authors.forename: Tetsuyuki
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Satoshi B
authors.initials: SB
authors.lastname: Sato
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Donna B
authors.initials: DB
authors.lastname: Stolz
authors.forename: Masato
authors.initials: M
authors.lastname: Umeda
mesh_terms: D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D013109:Sphingomyelins / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism*
chemical_list: D013109:Sphingomyelins