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The Rab5 effector Rabaptin‐5 and its isoform Rabaptin‐5δ differ in their ability to interact with the small GTPase Rab4
Author(s) -
Korobko Elena,
Kiselev Sergey,
Olsnes Sjur,
Stenmark Harald,
Korobko Igor
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1432-1033.2004.04399.x
Subject(s) - gtpase , endocytic cycle , gtp' , biology , endocytosis , microbiology and biotechnology , biochemistry , cell , enzyme
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‐5δ. To evaluate the interaction properties of Rabaptin‐5δ 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‐5δ 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‐5δ 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‐5δ is involved only in the Rab5‐driven events.