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  • The EMBO Journal (2008) 27, 1183 - 1196
  • doi:10.1038/emboj.2008.54

Published online: 20 March 2008

Regulation of endocytic recycling by C. elegans Rab35 and its regulator RME-4, a coated-pit protein

Miyuki Sato1,2,4, Ken Sato1,2,4, Willisa Liou3, Saumya Pant1, Akihiro Harada2 and Barth D Grant1

  1. Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ, USA
  2. Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Gunma, Japan
  3. Department of Anatomy, Chang Gung University, Taiwan, ROC
  4. These authors contributed equally to this work

Correspondence to:

Barth D Grant, Department of Molecular Biology and Biochemistry, Rutgers University, Nelson Biological Labs, Room A307, 604 Allison Road, Piscataway, NJ 8854, USA. Tel.: +1 732 445 7339; Fax: +1 732 445 4213; E-mail: grant@biology.rutgers.edu

Ken Sato, Laboratory of Molecular Traffic, Institute for Molecular and Cellular Regulation, Gunma University, Showa 3-39-15, Maebashi, Gunma 371-8512, Japan. Tel.: +81 27 220 8842; Fax: +81 27 220 8844; E-mail: sato-ken@showa.gunma-u.ac.jp

Received 4 January 2008; Accepted 27 February 2008

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.

  • Keywords:

    • C. elegans,
    • clathrin-coated pits,
    • endocytic recycling,
    • Rab GTPase