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Endosome fusion and microtubule-based dynamics in the early endocytic pathway of dictyostelium

Margaret Clarke1, Jana Köhler, John Heuser

  • 1Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA. clarkem@omrf.ouhsc.edu

Traffic (Copenhagen, Denmark)
|October 18, 2002
PubMed

Insights

Dictyostelium amoebae fluid uptake involves macropinosome fusion with early endosomes. Microtubules drive endosome dynamics and fusion, crucial for cellular processes.

Area of Science:

  • Cell Biology
  • Molecular Biology

Background:

  • Dictyostelium amoebae exhibit macropinocytosis, a fluid uptake mechanism similar to mammalian macrophages.
  • Endosome dynamics and fusion are critical cellular processes requiring detailed investigation.

Purpose of the Study:

  • To visualize and understand the dynamics and fusion of early endosomes during macropinocytosis in Dictyostelium.
  • To elucidate the role of microtubules and actin filaments in endosome trafficking and maturation.

Main Methods:

  • Utilized fluorescent fluid-phase markers for tracking endocytosis.
  • Employed GFP-labeled microtubules to visualize dynamic interactions.
  • Applied electron microscopy for detailed structural analysis.
  • Used actin and microtubule disrupting agents to assess cytoskeletal involvement.

Main Results:

  • Demonstrated fusion of newly formed macropinosomes with pre-existing endosomes within minutes of uptake.
  • Observed significant shape changes and rapid, microtubule-associated transport of fusing endosomes.
  • Confirmed microtubule-dependent dynamics, with actin filaments playing a lesser role.
  • Showed that further endosome maturation leads to spherical shape, reduced fusion capacity, and decreased motility.

Conclusions:

  • Early endosome fusion and dynamics in Dictyostelium are primarily microtubule-driven processes.
  • Endosome plasticity is highest during the initial fusion stage.
  • Maturation involves loss of plasticity, fusion ability, and motility, indicating a transition to a terminal state.

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