title: The Rab5 effector Rabaptin-5 and its isoform Rabaptin-5delta differ in their ability to interact with the small GTPase Rab4.
abstract: Rabaptin-5 is an effector for the small GTPase Rab5, a regulator of the early steps in endocytosis. In addition, Rabaptin-5 interacts with the small GTPase Rab4 that has been implicated in recycling from early endosomes to the cell surface. Recently we have identified a ubiquitous transcript encoding the Rabaptin-5 isoform, Rabaptin-5delta. To evaluate the interaction properties of Rabaptin-5delta with the small GTPases Rab4 and Rab5, we have applied protein interaction assays using the yeast two-hybrid system and a glutathione S-transferase pull-down assay. We found that unlike Rabaptin-5, that interacts with both GTPases in GTP-bound conformations, Rabaptin-5delta interacts only with GTP-bound Rab5, and does not interact with Rab4, presumably due to a disrupted Rab4 binding site. Immunofluorescence microscopy analysis carried out to address the localization of Rabaptin-5delta relative to GTP-bound Rab4 and Rab5 in BHK-21 cells supported these data. Our data suggests that while Rabaptin-5 was proposed to act as a molecular linker between Rab5 and Rab4, to coordinate endocytic and recycling traffic, Rabaptin-5delta is involved only in the Rab5-driven events.
authors.affiliation: Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia. alenavk@igb.ac.ru
authors.forename: Elena
authors.initials: E
authors.lastname: Korobko
authors.forename: Sergey
authors.initials: S
authors.lastname: Kiselev
authors.forename: Sjur
authors.initials: S
authors.lastname: Olsnes
authors.forename: Harald
authors.initials: H
authors.lastname: Stenmark
authors.forename: Igor
authors.initials: I
authors.lastname: Korobko
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D033921:Vesicular Transport Proteins