title: Rabaptin-5alpha/rabaptin-4 serves as a linker between rab4 and gamma(1)-adaptin in membrane recycling from endosomes.
abstract: Rab4 regulates recycling from early endosomes. We investigated the role of the rab4 effector rabaptin-5alpha and its putative partner gamma(1)-adaptin in membrane recycling. We found that rabaptin-5alpha forms a ternary complex with the gamma(1)-sigma(1) subcomplex of AP-1, via a direct interaction with the gamma(1)-subunit. The binding site for gamma(1)-adaptin is in the hinge region of rabaptin-5alpha, which is distinct from rab4- and rab5-binding domains. Endogenous or ectopically expressed gamma(1)- adaptin localized to both the trans-Golgi network and endosomes. Co-expressed rabaptin-5alpha and gamma(1)-adaptin, however, co-localized in a rab4-dependent manner on recycling endosomes. Transfection of rabaptin-5alpha caused enlarged endosomes and delayed recycling of transferrin. RNAi of rab4 had an opposing effect on transferrin recycling. Collectively, our data show that rab4-GTP acts as a scaffold for a rabaptin-5alpha- gamma(1)-adaptin complex on recycling endosomes and that interactions between rab4, rabaptin-5alpha and gamma(1)-adaptin regulate membrane recycling.
authors.affiliation: Department of Cell Biology and Institute of Biomembranes, University Medical Center, NL-3584 CX Utrecht, The Netherlands.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Deneka
authors.forename: Maaike
authors.initials: M
authors.lastname: Neeft
authors.forename: Ioana
authors.initials: I
authors.lastname: Popa
authors.forename: Masja
authors.initials: M
authors.lastname: van Oort
authors.forename: Hein
authors.initials: H
authors.lastname: Sprong
authors.forename: Viola
authors.initials: V
authors.lastname: Oorschot
authors.forename: Judith
authors.initials: J
authors.lastname: Klumperman
authors.forename: Peter
authors.initials: P
authors.lastname: Schu
authors.forename: Peter
authors.initials: P
authors.lastname: van der Sluijs
mesh_terms: D033982:Adaptor Protein Complex gamma Subunits / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000737:chemistry / Q000378:metabolism; D033921:Vesicular Transport Proteins; D020695:rab4 GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D033982:Adaptor Protein Complex gamma Subunits; D002352:Carrier Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; C097227:RABEP1 protein, human; C486276:Rabep1 protein, mouse; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D033921:Vesicular Transport Proteins; D020695:rab4 GTP-Binding Proteins