The Rab5 effector Rabaptin-5 and its isoform Rabaptin-5delta differ in their ability to interact with the small GTPase Rab4

FEBS J. 2005 Jan;272(1):37-46. doi: 10.1111/j.1742-4658.2004.04387.x.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cricetinae
  • Cytosol / metabolism
  • Microscopy, Fluorescence
  • Protein Binding
  • Protein Isoforms / metabolism*
  • Subcellular Fractions / metabolism
  • Vesicular Transport Proteins / metabolism*

Substances

  • Protein Isoforms
  • Vesicular Transport Proteins