title: Heteromerization of innexin gap junction proteins regulates epithelial tissue organization in Drosophila.
abstract: Gap junctions consist of clusters of intercellular channels, which enable direct cell-to-cell communication and adhesion in animals. Whereas deuterostomes, including all vertebrates, use members of the connexin and pannexin multiprotein families to assemble gap junction channels, protostomes such as Drosophila and Caenorhabditis elegans use members of the innexin protein family. The molecular composition of innexin-containing gap junctions and the functional significance of innexin oligomerization for development are largely unknown. Here, we report that heteromerization of Drosophila innexins 2 and 3 is crucial for epithelial organization and polarity of the embryonic epidermis. Both innexins colocalize in epithelial cell membranes. Innexin3 is mislocalized to the cytoplasm in innexin2 mutants and is recruited into ectopic expression domains defined by innexin2 misexpression. Conversely, RNA interference (RNAi) knockdown of innexin3 causes mislocalization of innexin2 and of DE-cadherin, causing cell polarity defects in the epidermis. Biochemical interaction studies, surface plasmon resonance analysis, transgenesis, and biochemical fractionation experiments demonstrate that both innexins interact via their C-terminal cytoplasmic domains during the assembly of heteromeric channels. Our data provide the first molecular and functional demonstration that innexin heteromerization occurs in vivo and reveal insight into a molecular mechanism by which innexins may oligomerize into heteromeric gap junction channels.
authors.affiliation: Institut für Molekulare Physiologie und Entwicklungsbiologie der Universität Bonn, 53115 Bonn, Germany.
authors.forename: Corinna
authors.initials: C
authors.lastname: Lehmann
authors.forename: Hildegard
authors.initials: H
authors.lastname: Lechner
authors.forename: Birgit
authors.initials: B
authors.lastname: Löer
authors.forename: Martin
authors.initials: M
authors.lastname: Knieps
authors.forename: Sonja
authors.initials: S
authors.lastname: Herrmann
authors.forename: Michael
authors.initials: M
authors.lastname: Famulok
authors.forename: Reinhard
authors.initials: R
authors.lastname: Bauer
authors.forename: Michael
authors.initials: M
authors.lastname: Hoch
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000032:analysis; D016764:Cell Polarity / Q000235:genetics; D017630:Connexins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D004330:Drosophila / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004848:Epithelium / Q000737:chemistry / Q000196:embryology* / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D017434:Protein Structure, Tertiary; D034622:RNA Interference
chemical_list: D015820:Cadherins; D017630:Connexins; D029721:Drosophila Proteins; C438564:INX3 protein, Drosophila; C120024:inx2 protein, Drosophila