title: Rab6 Is Required for Multiple Apical Transport Pathways but Not the Basolateral Transport Pathway in Drosophila Photoreceptors.
abstract: Polarized membrane trafficking is essential for the construction and maintenance of multiple plasma membrane domains of cells. Highly polarized Drosophila photoreceptors are an excellent model for studying polarized transport. A single cross-section of Drosophila retina contains many photoreceptors with 3 clearly differentiated plasma membrane domains: a rhabdomere, stalk, and basolateral membrane. Genome-wide high-throughput ethyl methanesulfonate screening followed by precise immunohistochemical analysis identified a mutant with a rare phenotype characterized by a loss of 2 apical transport pathways with normal basolateral transport. Rapid gene identification using whole-genome resequencing and single nucleotide polymorphism mapping identified a nonsense mutation of Rab6 responsible for the apical-specific transport deficiency. Detailed analysis of the trafficking of a major rhabdomere protein Rh1 using blue light-induced chromophore supply identified Rab6 as essential for Rh1 to exit the Golgi units. Rab6 is mostly distributed from the trans-Golgi network to a Golgi-associated Rab11-positive compartment that likely recycles endosomes or transport vesicles going to recycling endosomes. Furthermore, the Rab6 effector, Rich, is required for Rab6 recruitment in the trans-Golgi network. Moreover, a Rich null mutation phenocopies the Rab6 null mutant, indicating that Rich functions as a guanine nucleotide exchange factor for Rab6. The results collectively indicate that Rab6 and Rich are essential for the trans-Golgi network-recycling endosome transport of cargoes destined for 2 apical domains. However, basolateral cargos are sorted and exported from the trans-Golgi network in a Rab6-independent manner.
authors.affiliation: Division of Life Science, Graduate School of Integral Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Iwanami
authors.affiliation: Division of Life Science, Graduate School of Integral Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Division of Life Science, Graduate School of Integral Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Takunori
authors.initials: T
authors.lastname: Satoh
authors.affiliation: Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, Heilongjiang, China.
authors.forename: Ziguang
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Division of Life Science, Graduate School of Integral Arts and Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Akiko K
authors.initials: AK
authors.lastname: Satoh
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D004330:Drosophila / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D016296:Mutagenesis; D009154:Mutation; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D021381:Protein Transport; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029721:Drosophila Proteins; D005020:Ethyl Methanesulfonate; D008565:Membrane Proteins; D020691:rab GTP-Binding Proteins; C094135:Rab6 protein; C520715:Rip11 protein, Drosophila; C559123:Rab11 protein, Drosophila; D000099193:rab11 GTP-Binding Proteins; C000608944:Rab6 protein, Drosophila