title: Rabring7, a novel Rab7 target protein with a RING finger motif.
abstract: Rab7, a member of the Rab family small G proteins, has been shown to regulate intracellular vesicle traffic to late endosome/lysosome and lysosome biogenesis, but the exact roles of Rab7 are still undetermined. Accumulating evidence suggests that each Rab protein has multiple target proteins that function in the exocytic/endocytic pathway. We have isolated a new Rab7 target protein, Rabring7 (Rab7-interacting RING finger protein), using a CytoTrap system. It contains an H2 type RING finger motif at the C termini. Rabring7 shows no homology with RILP, which has been reported as another Rab7 target protein. GST pull-down and coimmunoprecipitation assays demonstrate that Rabring7 specifically binds the GTP-bound form of Rab7 at the N-terminal portion. Rabring7 is found mainly in the cytosol and is recruited efficiently to late endosomes/lysosomes by the GTP-bound form of Rab7 in BHK cells. Overexpression of Rabring7 not only affects epidermal growth factor degradation but also causes the perinuclear aggregation of lysosomes, in which the accumulation of the acidotropic probe LysoTracker is remarkably enhanced. These results suggest that Rabring7 plays crucial roles as a Rab7 target protein in vesicle traffic to late endosome/lysosome and lysosome biogenesis.
authors.affiliation: Department of Biochemistry, The University of Tokushima Graduate School of Medicine, Tokushima 770-8503, Japan.
authors.forename: Kouichi
authors.initials: K
authors.lastname: Mizuno
authors.forename: Akiko
authors.initials: A
authors.lastname: Kitamura
authors.forename: Takuya
authors.initials: T
authors.lastname: Sasaki
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004705:Endocytosis / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology; D015723:Gene Library; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008247:Lysosomes / Q000378:metabolism / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D021381:Protein Transport / Q000502:physiology; D044767:Ubiquitin-Protein Ligases; D020691:rab GTP-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D000090802:rab7 GTP-Binding Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C423317:RILP protein, human; C498920:Rilp protein, mouse; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; C000716465:rab7 GTP-binding proteins, mouse; D004815:Epidermal Growth Factor; C483359:Rnf115 protein, mouse; D044767:Ubiquitin-Protein Ligases; D020691:rab GTP-Binding Proteins