title: RAB-10-GTPase-mediated regulation of endosomal phosphatidylinositol-4,5-bisphosphate.
abstract: Caenorhabditis elegans RAB-10 and mammalian Rab10 are key regulators of endocytic recycling, especially in the basolateral recycling pathways of polarized epithelial cells. To understand better how RAB-10 contributes to recycling endosome function, we sought to identify RAB-10 effectors. One RAB-10-binding partner that we identified, CNT-1, is the only C. elegans homolog of the mammalian Arf6 GTPase-activating proteins ACAP1 and ACAP2. Arf6 is known to regulate endosome-to-plasma membrane transport, in part through activation of type I phophatidylinositol-4-phosphate 5 kinase. Here we show that CNT-1 binds to RAB-10 through its C-terminal ankyrin repeats and colocalizes with RAB-10 and ARF-6 on recycling endosomes in vivo. Furthermore, we find that RAB-10 is required for the recruitment of CNT-1 to endosomal membranes in the intestinal epithelium. Consistent with negative regulation of ARF-6 by RAB-10 and CNT-1, we found overaccumulation of endosomal phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] in cnt-1 and rab-10 mutants and reduced endosomal PI(4,5)P2 levels in arf-6 mutants. These mutants produced similar effects on endosomal recruitment of the PI(4,5)P2-dependent membrane-bending proteins RME-1/Ehd and SDPN-1/Syndapin/Pacsin and resulted in endosomal trapping of specific recycling cargo. Our studies identify a RAB-10-to-ARF-6 regulatory loop required to regulate endosomal PI(4,5)P2, a key phosphoinositide in membrane traffic.
authors.affiliation: Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854, USA.
authors.forename: Anbing
authors.initials: A
authors.lastname: Shi
authors.forename: Ou
authors.initials: O
authors.lastname: Liu
authors.forename: Sabine
authors.initials: S
authors.lastname: Koenig
authors.forename: Riju
authors.initials: R
authors.lastname: Banerjee
authors.forename: Carlos Chih-Hsiung
authors.initials: CC
authors.lastname: Chen
authors.forename: Stefan
authors.initials: S
authors.lastname: Eimer
authors.forename: Barth D
authors.initials: BD
authors.lastname: Grant
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000201:enzymology*; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology; D020798:Two-Hybrid System Techniques; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C576670:CNT-1 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D002966:Clathrin; D020690:GTPase-Activating Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D020558:GTP Phosphohydrolases; C510977:RAB-10 protein, C elegans; D020691:rab GTP-Binding Proteins