Inhibition of early endosome fusion by Rab5-binding defective Ras interference 1 mutants

Arch Biochem Biophys. 2009 Feb;482(1-2):83-95. doi: 10.1016/ Epub 2008 Nov 14.


Rin1 has been shown to play an important role in endocytosis. In this study we demonstrated that depletion of Rin1 from the cytosol blocked the fusion reaction. More importantly, endosome fusion was rescued by the addition of Rin1 proteins depending on the presence of Rab5, and its effector EEA1. Furthermore, we found that Syntaxin 13, but not Syntaxin 7, was required by Rin1 to support endosome fusion. We also identified six mutations on the Vps9 domain of Rin1 that failed to rescue the fusion reaction. Two of them, Rin1: D537A and Rin1: Y561F mutants showed dramatic inhibitory effect on the fusion reaction, which correlate with their inability to properly activate Rab5 or to bind endosomal membranes. Taken together, our results suggest that specific residues on the Vsp9 domain of Rin1 are required for its interaction with Rab5, binding to the endosomal membranes and subsequent regulation of the fusion reaction.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Phosphatase / metabolism
  • Cell Fusion
  • Cytosol / metabolism
  • Endocytosis
  • Endosomes / genetics
  • Endosomes / metabolism
  • Endosomes / physiology*
  • Epidermal Growth Factor / metabolism
  • Genes, ras
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Plasmids
  • Qa-SNARE Proteins / genetics
  • Qa-SNARE Proteins / metabolism
  • Vesicular Transport Proteins / metabolism
  • beta-Galactosidase / metabolism
  • rab5 GTP-Binding Proteins / deficiency*
  • rab5 GTP-Binding Proteins / genetics
  • rab5 GTP-Binding Proteins / metabolism*


  • Intracellular Signaling Peptides and Proteins
  • Qa-SNARE Proteins
  • RIN1 protein, human
  • Vesicular Transport Proteins
  • early endosome antigen 1
  • Epidermal Growth Factor
  • Acid Phosphatase
  • beta-Galactosidase
  • rab5 GTP-Binding Proteins