The Rab5 effector Rabaptin-5 and its isoform Rabaptin-5delta differ in their ability to interact with the small GTPase Rab4.
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.
Korobko
Elena
E
Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia. alenavk@igb.ac.ru
Kiselev
Sergey
S
Olsnes
Sjur
S
Stenmark
Harald
H
Korobko
Igor
I
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*
D020033:Protein Isoforms; D033921:Vesicular Transport Proteins