Abstract
Here we identify a new regulator of endocytosis called RME-6. RME-6 is evolutionarily conserved among metazoans and contains Ras-GAP (GTPase-activating protein)-like and Vps9 domains. Consistent with the known catalytic function of Vps9 domains in Rab5 GDP/GTP exchange, we found that RME-6 binds specifically to Caenorhabditis elegans RAB-5 in the GDP-bound conformation, and rme-6 mutants have phenotypes that indicate low RAB-5 activity. However, unlike other Rab5-associated proteins, a rescuing green fluorescent protein (GFP)-RME-6 fusion protein primarily localizes to clathrin-coated pits, physically interacts with alpha-adaptin, a clathrin adaptor protein, and requires clathrin to achieve its cortical localization. In rme-6 mutants, transport from the plasma membrane to endosomes is defective, and small 110-nm endocytic vesicles accumulate just below the plasma membrane. These results suggest a mechanism for the activation of Rab5 in clathrin-coated pits or clathrin-coated vesicles that is essential for the delivery of endocytic cargo to early endosomes.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Protein Complex alpha Subunits / metabolism
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Animals
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Caenorhabditis elegans / genetics
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Caenorhabditis elegans / metabolism*
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Caenorhabditis elegans / ultrastructure
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Caenorhabditis elegans Proteins / genetics
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Caenorhabditis elegans Proteins / isolation & purification
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Caenorhabditis elegans Proteins / metabolism*
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Cell Membrane / metabolism*
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Cell Membrane / ultrastructure
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Clathrin-Coated Vesicles / metabolism*
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Clathrin-Coated Vesicles / ultrastructure
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Endocytosis / physiology*
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Endosomes / metabolism
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Membrane Proteins / genetics
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Membrane Proteins / isolation & purification
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Membrane Proteins / metabolism*
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Microscopy, Electron, Transmission
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Molecular Sequence Data
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Mutation
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Phenotype
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Protein Binding / physiology
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Protein Transport / physiology
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Transport Vesicles / metabolism
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rab5 GTP-Binding Proteins / genetics
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rab5 GTP-Binding Proteins / metabolism*
Substances
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Adaptor Protein Complex alpha Subunits
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Caenorhabditis elegans Proteins
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Membrane Proteins
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RME-6 protein, C elegans
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Recombinant Fusion Proteins
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rab5 GTP-Binding Proteins