Abstract
Stardust (Sdt) and Discs-Large (Dlg) are membrane-associated guanylate kinases (MAGUKs) involved in the organization of supramolecular protein complexes at distinct epithelial membrane compartments in Drosophila. Loss of either Sdt or Dlg affects epithelial development with severe effects on apico-basal polarity. Moreover, Dlg is required for the structural and functional integrity of synaptic junctions. Recent biochemical and cell culture studies have revealed that various mammalian MAGUKs can interact with mLin-7/Veli/MALS, a small PDZ-domain protein. To substantiate these findings for their in vivo significance with regard to Sdt- and Dlg-based protein complexes, we analyzed the subcellular distribution of Drosophila Lin-7 (DLin-7) and performed genetic and biochemical assays to characterize its interaction with either of the two MAGUKs. In epithelia, Sdt mediates the recruitment of DLin-7 to the subapical region, while at larval neuromuscular junctions, a particular isoform of Dlg, Dlg-S97, is required for postsynaptic localization of DLin-7. Ectopic expression of Dlg-S97 in epithelia, however, was not sufficient to induce a redistribution of DLin-7. These results imply that the recruitment of DLin-7 to MAGUK-based protein complexes is defined by cell-type specific mechanisms and that DLin-7 acts downstream of Sdt in epithelia and downstream of Dlg at synapses.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alleles
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Animals
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Biotinylation
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Blotting, Northern
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Blotting, Western
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Cell Adhesion Molecules / chemistry
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Cell Adhesion Molecules / metabolism*
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Central Nervous System / embryology
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DNA, Complementary / metabolism
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Drosophila
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Drosophila Proteins / chemistry
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Drosophila Proteins / metabolism*
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Drosophila Proteins / physiology*
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Epithelial Cells
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Epithelium / metabolism
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Exons
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Gene Expression Regulation, Developmental*
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Glutathione Transferase / metabolism
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Green Fluorescent Proteins / metabolism
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Guanylate Kinases
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Immunoprecipitation
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Introns
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Membrane Transport Proteins / physiology*
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Microscopy, Confocal
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Microscopy, Fluorescence
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Muscles / embryology
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Mutation
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Nerve Tissue Proteins / metabolism
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Neuromuscular Junction
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Nucleoside-Phosphate Kinase / metabolism*
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Nucleoside-Phosphate Kinase / physiology*
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Protein Binding
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Protein Isoforms
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Protein Structure, Tertiary
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Reverse Transcriptase Polymerase Chain Reaction
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Synapses / metabolism
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Transgenes
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Tumor Suppressor Proteins / physiology*
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Two-Hybrid System Techniques
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Wings, Animal / embryology
Substances
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Cell Adhesion Molecules
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DNA, Complementary
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Drosophila Proteins
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Membrane Transport Proteins
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Nerve Tissue Proteins
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Protein Isoforms
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Tumor Suppressor Proteins
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Veli protein, Drosophila
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dlg1 protein, Drosophila
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Green Fluorescent Proteins
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Glutathione Transferase
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Nucleoside-Phosphate Kinase
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Guanylate Kinases
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sdt protein, Drosophila