title: Distinct requirements for the AP-3 adaptor complex in pigment granule and synaptic vesicle biogenesis in Drosophila melanogaster.
abstract: The AP-3 adaptor protein complex has been implicated in the biogenesis of lysosome-related organelles, such as pigment granules/melanosomes, and synaptic vesicles. Here we compare the relative importance of AP-3 in the biogenesis of these organelles in Drosophila melanogaster. We report that the Drosophila pigmentation mutants orange and ruby carry genetic lesions in the sigma3 and beta3-adaptin subunits of the AP-3 complex, respectively. Electron microscopy reveals dramatic reductions in the numbers of electron-dense pigment granules in the eyes of these AP-3 mutants. Mutant flies also display greatly reduced levels of pigments housed in these granules. In contrast, electron microscopy of retinula cells reveals numerous synaptic vesicles in both AP-3 mutant and wild-type flies, while behavioral assays show apparently normal locomotor ability of AP-3 mutant larvae. Together, these results demonstrate that Drosophila AP-3 is critical for the biogenesis of pigment granules, but is apparently not essential for formation of a major population of synaptic vesicles in vivo.
authors.affiliation: Cell Biology and Metabolism Branch, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: C
authors.initials: C
authors.lastname: Mullins
authors.forename: L M
authors.initials: LM
authors.lastname: Hartnell
authors.forename: J S
authors.initials: JS
authors.lastname: Bonifacino
mesh_terms: D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D001522:Behavior, Animal; D002454:Cell Differentiation; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D004331:Drosophila melanogaster; D017344:Genes, Insect; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D034041:Monomeric Clathrin Assembly Proteins; D009068:Movement; D009154:Mutation; D017956:Photoreceptor Cells, Invertebrate / Q000648:ultrastructure*; D010860:Pigments, Biological / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013572:Synaptic Vesicles / Q000648:ultrastructure*
chemical_list: D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D008565:Membrane Proteins; D034041:Monomeric Clathrin Assembly Proteins; D010860:Pigments, Biological; C439023:clathrin assembly protein AP180