AMPH-1/Amphiphysin/Bin1 functions with RME-1/Ehd in endocytic recycling

RME-1/EHD1 family proteins are key residents of the recycling endosome required for endosome to plasma membrane transport in C. elegans and mammals. Recent studies suggest parallels of the RME-1/EHD proteins to the Dynamin GTPase superfamily of mechanochemical pinchases that promote membrane fission. Here we show that that endogenous C. elegans AMPH-1, the only C. elegans member of Amphiphysin/BIN1 family of BAR-domain proteins, colocalizes with RME-1 on recycling endosomes in vivo, that amph-1 deletion mutants are defective in recycling endosome morphology and function, and that binding of AMPH-1 NPF (D/E) sequences to the RME-1 EH-domain promotes the recycling of transmembrane cargo. We also show a requirement for human BIN1/Amphyphysin 2 in EHD1-regulated endocytic recycling. In vitro we find that the purified recombinant AMPH-1/RME-1 complexes produce short, coated, membrane tubules that are qualitatively distinct from those produced by either protein alone. Our results indicate that AMPH-1 and RME-1 cooperatively regulate endocytic recycling, likely through functions required for the production of cargo carriers exiting the recycling endosome for the cell surface.