title: TBC-2 regulates RAB-5/RAB-7-mediated endosomal trafficking in Caenorhabditis elegans.
abstract: During endosome maturation the early endosomal Rab5 GTPase is replaced with the late endosomal Rab7 GTPase. It has been proposed that active Rab5 can recruit and activate Rab7, which in turn could inactivate and remove Rab5. However, many of the Rab5 and Rab7 regulators that mediate endosome maturation are not known. Here, we identify Caenorhabditis elegans TBC-2, a conserved putative Rab GTPase-activating protein (GAP), as a regulator of endosome to lysosome trafficking in several tissues. We show that tbc-2 mutant animals accumulate enormous RAB-7-positive late endosomes in the intestine containing refractile material. RAB-5, RAB-7, and components of the homotypic fusion and vacuole protein sorting (HOPS) complex, a RAB-7 effector/putative guanine nucleotide exchange factor (GEF), are required for the tbc-2(-) intestinal phenotype. Expression of activated RAB-5 Q78L in the intestine phenocopies the tbc-2(-) large late endosome phenotype in a RAB-7 and HOPS complex-dependent manner. TBC-2 requires the catalytic arginine-finger for function in vivo and displays the strongest GAP activity on RAB-5 in vitro. However, TBC-2 colocalizes primarily with RAB-7 on late endosomes and requires RAB-7 for membrane localization. Our data suggest that TBC-2 functions on late endosomes to inactivate RAB-5 during endosome maturation.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, Royal Victoria Hospital, McGill University and McGill University Health Centre Research Institute, Montreal, Quebec H3A 1A1, Canada.
authors.forename: Laëtitia
authors.initials: L
authors.lastname: Chotard
authors.forename: Ashwini K
authors.initials: AK
authors.lastname: Mishra
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Sylvain
authors.forename: Simon
authors.initials: S
authors.lastname: Tuck
authors.forename: David G
authors.initials: DG
authors.lastname: Lambright
authors.forename: Christian E
authors.initials: CE
authors.lastname: Rocheleau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006801:Humans; D008969:Molecular Sequence Data; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000090802:rab7 GTP-Binding Proteins
chemical_list: D029742:Caenorhabditis elegans Proteins; D020690:GTPase-Activating Proteins; D011993:Recombinant Fusion Proteins; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins
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