Localization of Rab5 to synaptic vesicles identifies endosomal intermediate in synaptic vesicle recycling pathway

Eur J Cell Biol. 1994 Dec;65(2):319-26.


After exocytosis, synaptic vesicles rapidly endocytose and recycle but little is known about the molecular mechanisms involved. Rab5 is a ubiquitous low molecular weight GTP-binding protein required for endosomal fusion in fibroblasts. We have now raised polyclonal and monoclonal antibodies to rat Rab5 and show that in rat brain, Rab5 is a major synaptic vesicle protein. Immunoisolation of vesicular organelles from brain with antibodies to either Rab3A and Rab5 as small GTP-binding proteins or with synaptophysin as general synaptic vesicle marker demonstrates that there are overlapping populations of synaptic vesicles containing either Rab5 or Rab3A or both, suggesting a stage-specific association of these low-molecular weight GTP-binding proteins with synaptic vesicles. Our data provide the first biochemical evidence that synaptic vesicle recycling involves an endosomal intermediate similar to that of the receptor-mediated endocytosis pathway.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Biomarkers / chemistry
  • Endocytosis / physiology
  • Endosomes / metabolism*
  • GTP-Binding Proteins / analysis*
  • Molecular Sequence Data
  • Molecular Weight
  • Nerve Tissue Proteins / analysis*
  • Synaptic Vesicles / chemistry*
  • rab3 GTP-Binding Proteins
  • rab5 GTP-Binding Proteins


  • Biomarkers
  • Nerve Tissue Proteins
  • GTP-Binding Proteins
  • rab3 GTP-Binding Proteins
  • rab5 GTP-Binding Proteins