title: Divalent interaction of the GGAs with the Rabaptin-5-Rabex-5 complex.
abstract: Cargo transfer from trans-Golgi network (TGN)-derived transport carriers to endosomes involves a still undefined set of tethering/fusion events. Here we analyze a molecular interaction that may play a role in this process. We demonstrate that the GGAs, a family of Arf-dependent clathrin adaptors involved in selection of TGN cargo, interact with the Rabaptin-5-Rabex-5 complex, a Rab4/Rab5 effector regulating endosome fusion. These interactions are bipartite: GGA-GAE domains recognize an FGPLV sequence (residues 439-443) in a predicted random coil of Rabaptin-5 (a sequence also recognized by the gamma1- and gamma2-adaptin ears), while GGA-GAT domains bind to the C-terminal coiled-coils of Rabaptin-5. The GGA-Rabaptin-5 interaction decreases binding of clathrin to the GGA-hinge domain, and expression of green fluorescent protein (GFP)-Rabaptin-5 shifts the localization of endogenous GGA1 and associated cargo to enlarged early endosomes. These observations thus identify a binding sequence for GAE/gamma-adaptin ear domains and reveal a functional link between proteins regulating TGN cargo export and endosomal tethering/fusion events.
authors.affiliation: Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Rafael
authors.initials: R
authors.lastname: Mattera
authors.forename: Cecilia N
authors.initials: CN
authors.lastname: Arighi
authors.forename: Robert
authors.initials: R
authors.lastname: Lodge
authors.forename: Marino
authors.initials: M
authors.lastname: Zerial
authors.forename: Juan S
authors.initials: JS
authors.lastname: Bonifacino
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D019921:Biotinylation; D002966:Clathrin / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D016296:Mutagenesis; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002966:Clathrin; D020662:Guanine Nucleotide Exchange Factors; D010446:Peptide Fragments; C097227:RABEP1 protein, human; C108382:RABGEF1 protein, human; D011993:Recombinant Fusion Proteins; D033921:Vesicular Transport Proteins; D005982:Glutathione Transferase