title: Flotillins directly interact with γ-catenin and regulate epithelial cell-cell adhesion.
abstract: Flotillin-1 and flotillin-2 are two homologous, membrane raft associated proteins. Although it has been reported that flotillins are involved in cell adhesion processes and play a role during breast cancer progression, thus making them interesting future therapeutic targets, their precise function has not been well elucidated. The present study investigates the function of these proteins in cell-cell adhesion in non-malignant cells. We have used the non-malignant epithelial MCF10A cells to study the interaction network of flotillins within cell-cell adhesion complexes. RNA interference was used to examine the effect of flotillins on the structure of adherens junctions and on the association of core proteins, such as E-cadherin, with membrane rafts. We here show that the cadherin proteins of the adherens junction associate with flotillin-2 in MCF10A cells and in various human cell lines. In vitro, flotillin-1 and flotillin-2 directly interact with γ-catenin which is so far the only protein known to be present both in the adherens junction and the desmosome. Mapping of the interaction domain within the γ-catenin sequence identified the Armadillo domains 6-8, especially ARM domain 7, to be important for the association with flotillins. Furthermore, depletion of flotillins significantly influenced the morphology of the adherens junction in human epithelial MCF10A cells and altered the association of E-cadherin and γ-catenin with membrane rafts. Taken together, these observations suggest a functional role for flotillins, especially flotillin-2, in cell-cell adhesion in non-malignant epithelial cells.
authors.affiliation: Institute of Biochemistry, Medical Faculty, Justus Liebig University, Giessen, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Kurrle
authors.affiliation: Institute of Biochemistry, Medical Faculty, Justus Liebig University, Giessen, Germany.
authors.forename: Frauke
authors.initials: F
authors.lastname: Völlner
authors.affiliation: Department of Dermatology and Allergology, Phillips University, Marburg, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Eming
authors.affiliation: Department of Dermatology and Allergology, Phillips University, Marburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hertl
authors.affiliation: Institute of Biochemistry, Medical Faculty, Justus Liebig University, Giessen, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Banning
authors.affiliation: Institute of Biochemistry, Medical Faculty, Justus Liebig University, Giessen, Germany.
authors.forename: Ritva
authors.initials: R
authors.lastname: Tikkanen
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism; D000704:Analysis of Variance; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004847:Epithelial Cells / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D034622:RNA Interference; D051185:gamma Catenin / Q000378:metabolism*
chemical_list: D015820:Cadherins; D017931:DNA Primers; D008565:Membrane Proteins; C106354:flotillins; D051185:gamma Catenin