The Drosophila homolog of the Exo84 exocyst subunit promotes apical epithelial identity.
The polarized architecture of epithelial tissues involves a dynamic balance between apical and basolateral membrane domains. Here we show that epithelial polarity in the Drosophila embryo requires the exocyst complex subunit homolog Exo84. Exo84 activity is essential for the apical localization of the Crumbs transmembrane protein, a key determinant of epithelial apical identity. Adherens junction proteins become mislocalized at the cell surface in Exo84 mutants in a pattern characteristic of defects in apical, but not basolateral, components. Loss of Crumbs from the cell surface precedes the disruption of Bazooka and Armadillo localization in Exo84 mutants. Moreover, Exo84 mutants display defects in apical cuticle secretion that are similar to crumbs mutants and are suppressed by a reduction in the basolateral proteins Dlg and Lgl. In Exo84 mutants at advanced stages of epithelial degeneration, apical and adherens junction proteins accumulate in an expanded recycling endosome compartment. These results suggest that epithelial polarity in the Drosophila embryo is actively maintained by exocyst-dependent apical localization of the Crumbs transmembrane protein.
Blankenship
J Todd
JT
Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10021, USA. blankenj@mskcc.org
Fuller
Margaret T
MT
Zallen
Jennifer A
JA
D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D051186:Armadillo Domain Proteins / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D016764:Cell Polarity; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
C495305:ARM protein, Drosophila; D051186:Armadillo Domain Proteins; D015820:Cadherins; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C066176:Nrt protein, Drosophila; D021122:Protein Subunits; D014157:Transcription Factors; D033921:Vesicular Transport Proteins; C400774:baz protein, Drosophila; C064360:crb protein, Drosophila