Caenorhabditis elegans RME-6 is a novel regulator of RAB-5 at the clathrin-coated pit.
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.
Sato
Miyuki
M
Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08854, USA.
Sato
Ken
K
Fonarev
Paul
P
Huang
Chih-Jen
CJ
Liou
Willisa
W
Grant
Barth D
BD
D033965:Adaptor Protein Complex alpha Subunits / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D022163:Clathrin-Coated Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011485:Protein Binding / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D033965:Adaptor Protein Complex alpha Subunits; D029742:Caenorhabditis elegans Proteins; D008565:Membrane Proteins; C502292:RME-6 protein, C elegans; D011993:Recombinant Fusion Proteins; D020696:rab5 GTP-Binding Proteins