Abstract
GTPases and lipid kinases regulate membrane traffic along the endocytic pathway by mechanisms that are not completely understood. Fusion between early endosomes requires phosphatidylinositol-3-OH kinase (PI(3)K) activity as well as the small GTPase Rab5. Excess Rab5-GTP complex restores endosome fusion when PI(3)K is inhibited. Here we identify the early-endosomal autoantigen EEA1 which binds the PI(3)K product phosphatidylinositol-3-phosphate, as a new Rab5 effector that is required for endosome fusion. The association of EEA1 with the endosomal membrane requires Rab5-GTP and PI(3)K activity, and excess Rab5-GTP stabilizes the membrane association of EEA1 even when PI(3)K is inhibited. The identification of EEA1 as a direct Rab5 effector provides a molecular link between PI(3)K and Rab5, and its restricted distribution to early endosomes indicates that EEA1 may confer directionality to Rab5-dependent endocytic transport.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Androstadienes / pharmacology
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Animals
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Autoantigens / physiology
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Cattle
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Cell Line
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Cloning, Molecular
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Cricetinae
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Endosomes / physiology*
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Enzyme Inhibitors / pharmacology
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / physiology*
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Guanosine Triphosphate / physiology
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HeLa Cells
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Humans
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Intracellular Membranes / physiology
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Membrane Fusion / physiology*
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Membrane Proteins / genetics
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Membrane Proteins / physiology*
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Mutagenesis
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Phosphatidylinositol 3-Kinases / physiology*
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Phosphoinositide-3 Kinase Inhibitors
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Recombinant Fusion Proteins / metabolism
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Vesicular Transport Proteins
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Wortmannin
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rab5 GTP-Binding Proteins
Substances
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Androstadienes
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Autoantigens
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Enzyme Inhibitors
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Membrane Proteins
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Phosphoinositide-3 Kinase Inhibitors
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Recombinant Fusion Proteins
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Vesicular Transport Proteins
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early endosome antigen 1
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Guanosine Triphosphate
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GTP-Binding Proteins
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rab5 GTP-Binding Proteins
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Wortmannin