title: Mon1-Ccz1 activates Rab7 only on late endosomes and dissociates from the lysosome in mammalian cells.
abstract: Rab GTPases act as molecular switches regulating various aspects of membrane trafficking. Among them, Rab5 and Rab7 play central roles in the endolysosomal network. Although many effectors downstream of Rab7 have been elucidated, our present understanding of the mechanism regulating Rab7 activity is extremely limited. It has only recently been accepted that the Mon1-Ccz1 complex is a Rab7 guanine nucleotide exchange factor, but it still remains unclear what the location where Mon1-Ccz1 works with Rab7 is. To address what kind of change or switch exists in the regulatory mechanism upstream of Rab7 during its transition from the late endosome to lysosome, we examined Rab7 activity in steady-state cells and during EGF-induced macropinocytosis using a newly developed FRET sensor. A combination of a Rab7 sensor and confocal FRET imaging techniques revealed that the activation of Rab7 on late endosomes depends on Mon1-Ccz1 and is implicated in late-endosome-lysosome fusion. In contrast, Rab7 activity on lysosomes was independent of Mon1-Ccz1 and active Rab7 played a role in perinuclear clustering of lysosomes.
authors.affiliation: Division of Biosignaling, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba 278-0022, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Yasuda
authors.affiliation: Division of Biosignaling, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba 278-0022, Japan.
authors.forename: So
authors.initials: S
authors.lastname: Morishita
authors.affiliation: Division of Biosignaling, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba 278-0022, Japan.
authors.forename: Akane
authors.initials: A
authors.lastname: Fujita
authors.affiliation: Division of Biosignaling, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba 278-0022, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Nanao
authors.affiliation: Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba 278-8510, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Wada
authors.affiliation: Department of Anatomy and Histology, Fukushima Medical University, Fukushima, Fukushima 960-1295, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Waguri
authors.affiliation: UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
authors.forename: Giampietro
authors.initials: G
authors.lastname: Schiavo
authors.affiliation: Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Division of Biosignaling, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba 278-0022, Japan tnakamr@rs.noda.tus.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D011992:Endosomes / Q000201:enzymology*; D004789:Enzyme Activation; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000201:enzymology*; D053858:Metabolic Networks and Pathways; D021381:Protein Transport; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000090802:rab7 GTP-Binding Proteins
chemical_list: D033921:Vesicular Transport Proteins; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; D020691:rab GTP-Binding Proteins
keywords: Endolysosomal pathway; FRET; GEF; Small GTPase