Regulation of endocytic recycling by C. elegans Rab35 and its regulator RME-4, a coated-pit protein.
Using Caenorhabditis elegans genetic screens, we identified receptor-mediated endocytosis (RME)-4 and RME-5/RAB-35 as important regulators of yolk endocytosis in vivo. In rme-4 and rab-35 mutants, yolk receptors do not accumulate on the plasma membrane as would be expected in an internalization mutant, rather the receptors are lost from cortical endosomes and accumulate in dispersed small vesicles, suggesting a defect in receptor recycling. Consistent with this, genetic tests indicate the RME-4 and RAB-35 function downstream of clathrin, upstream of RAB-7, and act synergistically with recycling regulators RAB-11 and RME-1. We find that RME-4 is a conserved DENN domain protein that binds to RAB-35 in its GDP-loaded conformation. GFP-RME-4 also physically interacts with AP-2, is enriched on clathrin-coated pits, and requires clathrin but not RAB-5 for cortical association. GFP-RAB-35 localizes to the plasma membrane and early endocytic compartments but is lost from endosomes in rme-4 mutants. We propose that RME-4 functions on coated pits and/or vesicles to recruit RAB-35, which in turn functions in the endosome to promote receptor recycling.
Sato
Miyuki
M
Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ, USA. sato-ken@showa.gunma-u.ac.jp
Sato
Ken
K
Liou
Willisa
W
Pant
Saumya
S
Harada
Akihiro
A
Grant
Barth D
BD
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism / Q000502:physiology*; D004530:Egg Yolk / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; C528928:RME-4 protein, C elegans; C528927:Rab-35 protein, C elegans; D020691:rab GTP-Binding Proteins