title: Rabip4' is an effector of rab5 and rab4 and regulates transport through early endosomes.
abstract: We describe the characterization of an 80-kDa protein cross-reacting with a monoclonal antibody against the human La autoantigen. The 80-kDa protein is a variant of rabip4 with an N-terminal extension of 108 amino acids and is expressed in the same cells. For this reason, we named it rabip4'. rabip4' is a peripheral membrane protein, which colocalized with internalized transferrin and EEA1 on early endosomes. Membrane association required the presence of the FYVE domain and was perturbed by the phosphatidylinositol 3-kinase inhibitor wortmannin. Expression of a dominant negative rabip4' mutant reduced internalization and recycling of transferrin from early endosomes, suggesting that it may be functionally linked to rab4 and rab5. In agreement with this, we found that rabip4' colocalized with the two GTPases on early endosomes and bound specifically and simultaneously to the GTP form of both rab4 and rab5. We conclude that rabip4' may coordinate the activities of rab4 and rab5, regulating membrane dynamics in the early endosomal system.
authors: Department of Biochemistry, Nijmegen Center for Molecular Life Sciences, University of Nijmegen, Nijmegen, The Netherlands.
authors: Michael A
authors: MA
authors: Fouraux
authors: Magda
authors: M
authors: Deneka
authors: Viorica
authors: V
authors: Ivan
authors: Annemarie
authors: A
authors: van der Heijden
authors: Jos
authors: J
authors: Raymackers
authors: Denise
authors: D
authors: van Suylekom
authors: Walther J
authors: WJ
authors: van Venrooij
authors: Peter
authors: P
authors: van der Sluijs
authors: Ger J M
authors: GJ
authors: Pruijn
mesh_terms: D000595:Amino Acid Sequence; D000730:Androstadienes / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017434:Protein Structure, Tertiary / Q000502:physiology; D014168:Transferrin / Q000378:metabolism; D033921:Vesicular Transport Proteins; D000077191:Wortmannin; D020695:rab4 GTP-Binding Proteins / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D000730:Androstadienes; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D014168:Transferrin; D033921:Vesicular Transport Proteins; D000077191:Wortmannin; D020695:rab4 GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; C093846:early endosome antigen 1