Coronin and vacuolin identify consecutive stages of a late, actin-coated endocytic compartment in Dictyostelium

Curr Biol. 1997 Mar 1;7(3):215-8. doi: 10.1016/s0960-9822(97)70093-9.


Cells of the unicellular eukaryote Dictyostelium discoideum take up all their nutrients by endocytosis. Both particle- and fluid-containing vacuoles are transiently surrounded by a cytoskeletal coat [1] [2]. When this coat has dissociated, acidification and digestion of the vesicle contents occur, followed by exocytosis of the indigestible remnants after 60-90 minutes. At least nine compartments are needed for mathematical modelling of endocytic transit [3], suggesting that markers associate for only a few minutes with a specific endocytic compartment. Among the proteins that have been identified as components of endocytic vesicles are actin, subunits of the V-H+ ATPase and small GTP-binding proteins of the Rab family [4] [5] [6] [7]. Using a monoclonal antibody produced against Dictyostelium endocytic vesicles, we have isolated a cDNA corresponding to a novel protein that we have named vacuolin. In order to determine the precise step along the endocytic pathway that involves vacuolin, we generated a fusion protein of the green fluorescent protein (GFP) and vacuolin. GFP-vacuolin-decorated vesicles were identified as a post-lysosomal compartment that acquires endocytic markers shortly before exocytosis. At earlier stages, this post-lysosomal compartment was identified by the binding of a tagged cytoskeletal protein, coronin-GFP. Vacuoles were coated with filamentous actin along the entire post-lysosomal pathway, and the integrity of the actin coat was required for exocytosis.

MeSH terms

  • Actins / analysis
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Biomarkers
  • Cytoskeletal Proteins / analysis*
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / isolation & purification
  • DNA, Complementary / genetics
  • Dictyostelium / chemistry
  • Dictyostelium / ultrastructure*
  • Endocytosis*
  • Endosomes / chemistry
  • Endosomes / ultrastructure*
  • Fluorescent Dyes
  • Fungal Proteins / analysis*
  • Green Fluorescent Proteins
  • Luminescent Proteins / analysis
  • Luminescent Proteins / genetics
  • Microfilament Proteins / analysis*
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Protozoan Proteins / analysis*
  • Recombinant Fusion Proteins / analysis
  • Vacuoles / chemistry
  • Vacuoles / ultrastructure


  • Actins
  • Biomarkers
  • Cytoskeletal Proteins
  • DNA, Complementary
  • Fluorescent Dyes
  • Fungal Proteins
  • Luminescent Proteins
  • Microfilament Proteins
  • Protozoan Proteins
  • Recombinant Fusion Proteins
  • vac A protein, Dictyostelium discoideum
  • coronin proteins
  • Green Fluorescent Proteins

Associated data

  • GENBANK/AF014049