View Program - asbmb

61
Ang2/Fat-free is a Conserved Subunit of the Golgiassociated
Retrograde Protein (GARP) Complex
Christina Schindler 1 , F. Javier Perez-Victoria 1 , Javier Magadan 1 , Gonzalo Mardones 1 , Cedric
Delevoye 2 , Maryse Romao 2 , Graca Rapos0 2 , Juan Bonifacino 1 .
Cell Biology and Metabolism Program, NICHD, National Institutes of Health, Bethesda, MD
20892 1 , Institut Curie, Centre National de la Recherche Scientifique-Unite Mixte de Recherce
144, Paris 2
Abstract:
The Golgi-associated Retrograde Protein (GARP) complex mediates tethering and fusion of
endosome-derived transport carriers to the trans-Golgi network (TGN). In the yeast
Saccharomyces cerevisiae, GARP comprises four subunits named Vps51p, Vps52p, Vps53p and
Vps54p. Bioinformatics and biochemical analyses have shown that other eukaryotes have
orthologs of these subunits, except for Vps51p. A yeast two-hybrid screen of a human cDNA
library identified a phylogenetically conserved protein, Ang2/Fat-free, which interacts with
Vps52, Vps53 and Vps54. Human Ang2 is larger than yeast Vps51p, but exhibits significant
homology in the N-terminal coiled-coil region that mediates assembly with other GARP
subunits. Biochemical analyses show that human Ang2, Vps52, Vps53 and Vps54 form an
obligatory 1:1:1:1 complex that strongly interacts with the regulatory Habc domain of the TGN
SNARE Syntaxin 6. Depletion of Ang2 or the GARP subunits similarly affects protein retrieval to
the TGN, lysosomal enzyme sorting and autophagy. These findings indicate that Ang2 is an
integral component of the GARP complex in most eukaryotes.